I tried to ride hard on a twisty tight bumpy mountain road that is very popular the other day. I say tried because that day I sucked! I have ridden this road well on other bikes (VFR 400, YZF 750). My '95 900 Monster has a motor which I think is well suited to such terrain, but the rear shock was a disaster.
My forks are re-valved with .95 springs and are set up for "riding fast on crap roads". They perform well and although a little firm for my 180 -190 or so pounds (80-85kgs), give good feel and control when pushing hard. My suspension guy and I spent time setting them up right and I have a good compromise setting.
The shock is rebuilt with an Eibach 9.5 spring (193336/ 0700.225.0550). Without going crazy on the preload ( I wouldn't be compressing it past 10mm on it's free length to get decent sag), I have 10mm static sag and 30-35mm rider sag. Good numbers I thought. I have experimented with the rebound damping and after the rebuild have noted that I have ample rebound damping available being able to use up to 16 clicks out with good control. 10 or so clicks and the shock felt like it was "packing" down in bumps and way harsh.
The main symptom I struggled with while hill climbing this road was the bike hitting bigger bumps and pot holes quite hard, "falling into" the pot holes and the rear squatting. I wasn't able to glide over bigger bumps and dips. This unsettled the front end and caused the bike to lose it's line. This stopped me getting on the gas and transitioning through esses of which this road has many. The back end would dance around and skip across when cornering. The hits were quite hard. A similar winding but smooth road causes no problem which is no suprise. In road dips it feels like the rear end drops very quickly for the initial part of the suspension stroke then "ramps up" fiercely with the progressive linkage. Reducing spring preload gives a bigger "hit' so I must be bottoming out as evidenced by the the sag numbers going out of range (saggy bum). Note that an 8.5 spring I tried was way too soft and didn't get me within decent sag numbers no matter how much I clamped down the preload (and caused scary wallowing of the rear end).
Some thoughts I have are that: 1. My spring is too soft for the "hoop" style linkage (and me) and I'm just really bottoming out?
2. The low speed compression damping is crap letting the rear end fall into dips in the road too quickly? I swear there's plenty of high speed damping (harsh over sharp edges).
3. The linkage has a pretty harsh/ steep rising rate which is great for the track but not for crappy roads (an influence of the 888 chassis perhaps)?
4. Maybe I translated the numbers on the spring all wrong and ended up with the wrong ft/Lbs-Kgs number?
I am aware that communicating suspension/handling symptoms can be ambiguous and appreciate any clarifying questions!Similar feeling symptoms with different causes are confusing.
Also of note is that when I owned the same model Monster from new back in '95-96, I had to have the shock replaced under warranty twice within 6 months for it losing all its gas and compression damping.
I will consult my suspension guy when his shop reopens, but would appreciate any thoughts or tips so I can give him a good context to the job.
cheers [beer]
Tony
I have sorted out a number of road bikes on a race track so I don't have any input on that road you ride (why go fast on a crappy road ?) And i've sorted out more than a few dirt bikes for MX & trail riding and IMO the comprise your going to have to make is that road bike suspension is designed to be good on mostly flat roads that's why there is only 4-5" of travel in sportbike susp. Since your bottoming out on the bumps but bike is fine on a flat road that should tell you something. The extreme braking, cornering, acceleration and weight of a sport bike demands a suspension set up that is inherently terrible on bumps. I don't see you ever getting a set=up that would work well on that road & well on a flat road. Anyway good luck I'd be interested to know if you get it worked out.
Thanks Link
I understand what you're saying, and it's a good point. I have a race bike (VFR 400) that tracks on rails on a race track that would kill you on that road. Further bearing out your point, you would be interested to know that someone went very fast that day on a motard..
My thought was to have a "fast street set up" on the Monster and still have the no compromise race bike for the track. My YZF and other VFR were quick on that road. The front end of the Monster was good, it followed the undulations of the road and I had great feel, but the rear was terrible and I couldn't ride around the problem.
By fast I was meaning riding "The Pace", quick in the corners (still with a margin) and legal on the straights. Fast on the straights around here can mean losing your licence and having your bike confiscated. It can also mean not being ready for the next decreasing radius corner...That's why I can't live without a racebike.
That road is so tight (and technical) that high corner speed is under or around the speed limit. My goal is to achieve the controlled but compliant set up. My suspension guy achieved it with the forks. Is it achievable with the stock shock and linkage?
Cheers
Tony
Also, the front springs may be a little stiff for your weight which would throw the front and rear out of balance. I have .95 RaceTech springs in the fork on my '03 800 Dark and I weigh 220# without gear. They might be just the tiniest bit stiff for me but the sag is good and the bike uses about 95% of the front travel without bottoming so I'm leaving it.
If I were 30-40 pounds lighter like you I can't imagine they'd be right.
Scott
Thanks Scott
I'll talk to my suspension guy when I ask him about the rear shock issues. Maybe I better weigh myself again, possibly too much Christmas cheer!
My sag numbers are 20mm static and 33-35 rider sag for the forks. how do they sound to you?
Cheers
Tony
The stock shock f sure benefits fr a stiffer spring but simply,
it is a bad unit. Maybe the worst on all Ducs I`ve ridden.
The Öhlins on mine transformed it, just is there and does what it is suppsed to.
A must is also to raise rear/lower forks to get a good weight balance.
Your sag numbers seems close enough.
Thanks
Yeah, the shock seems pretty rudimentary. Is it worth re-valving? It recieved a rebuild.
I have raised rear ride height by about 20mm or so via 10mm on the hoop adjustment. The spring is a 550 pounder
(is that 9.5kgs in translation)?
Cheers
Tony
Quote from: koko64 on January 07, 2010, 04:38:09 PM
Thanks
Yeah, the shock seems pretty rudimentary. Is it worth re-valving? It recieved a rebuild.
I have raised rear ride height by about 20mm or so via 10mm on the hoop adjustment. The spring is a 550 pounder
(is that 9.5kgs in translation)?
Cheers
Tony
OK, after reading your second post I get what ur after and it sounds like you should dump the rear & go Ohlins. I used to get my stockers re-valved and a few years back I went with an Ohilins rear and could not believe how good those rear shocks are I mean right out of the box it solved all the problems I was having with rear and over a 2 year period I know I saved enough money on rear tires that paid for the shock. I know shops that do great re-valves but the R&D Ohlins puts into there product is 20 times what anyone else is doing and the stuff they figure out at the race track gets put into next years or even mid-year improvements will get to the Ohilins dealers, pretty cool stuff ! Maybe you could pick up a used rear on ebay for what you would pay for a re-valve. Keep us posted I like suspension stories. Also what type of tires & psi are you running ?
Thanks Link
I'm running Bridgestone BT002 Racing. 30 psi rear, 32 psi front or 33/32 with my wife/highways. But I run Dunlop and Michelin too when the price is right. I have friends that still race and can get me supersport/superstock tyres cheap.
Pilot slicks on the Formula 400 racer (NC30), 28R/30F, only track days now.
I wonder if the Sachs shock can be re-valved and a remote resi added as I have a Showa one. My suspension guy thought there was a problem was with controlling the rate of slow speed compression damping. "No guts" to the shock he said. Any thoughts on his comment from your experience?
Cheers
Tony
Quote from: koko64 on January 07, 2010, 12:26:54 PM
Thanks Scott
I'll talk to my suspension guy when I ask him about the rear shock issues. Maybe I better weigh myself again, possibly too much Christmas cheer!
My sag numbers are 20mm static and 33-35 rider sag for the forks. how do they sound to you?
Cheers
Tony
Yeah, close enough. I go by this setup:
http://www.harpers.org/archive/2009/11/0082723Oops! Here's the right link: http://www.ohlins.com/Checkpoint-Ohlins/Setting-Up-Your-Bike/Underrubrik_1/ (http://www.ohlins.com/Checkpoint-Ohlins/Setting-Up-Your-Bike/Underrubrik_1/)
Maybe it is time for a rear upgrade. An Ohlins is certainly top notch but just getting the right spring is cheap and words better than the wrong one.
Scott
That Eibach spring is 550 lb/in, or about a 9.8 kg/mm.
IMO, it's pretty good for your weight of 180-190 lbs.
Those .95 fork springs are a bit heavier than I would set you up with, but California roads are not Australia roads.
Was the shock better before the rebuild, or is the bike new to you?
I had the bike two years and the shock was fixed under 3 month warranty and also rebuilt after warranty expired by my suspension guy which improved it. I will ask him to revalve it and fit a remote resi which I have.
He said that the shock had "no guts making the spring do all the work". Whats your take on that? Sounds like poor compression damping control to me.
The fork springs are Ohlins and the serial no on the box is: Kunds artnr: 08652-95. Does that number indicate anything to anyone? There are other serial numbers on the box if required. I figure the -95 part is the spring rate.
The forks are revalved and air gap was 130mm with springs with 5wt oil. Alot of effort and testing went into the adjustment of the oil height and preload. The forks work well despite the firm springs, with plenty of travel and don't get knocked off line by bumps, with just the right amount of fork dive under braking. Front end feel is good with good turn in and great trail braking. Nearly all the travel is used without bottoming.
I asked for 0.85-0.9 springs but he insisted on the 0.95's. Maybe I look fat! [laugh].
Cheers
Tony [drink]
hmm... like scott, i agree - .95s should be a little stiff for you. i'm 220 on a great day, buck nekkid on a scale. You ought to be rocking .85s I believe. HOWEVER, if you were able to get spring set correctly, that's a big part of it.
Like Greenmonster said, stock hooped monster's shock internals blow. Really bad. He went Ohlins, like many do, and I went Penske (8983) as many others do. They are the two top-shelf rear shocks. Makes the bike behave completely different. Revalving the forks is "ok", as far as improvements, with racetech valve kit, but really, not near the "WOW!" factor of the rearshock. I should have done that first, before I spent a dollar on anything else. Seriously. (Except maybe DynaCoils, which make the bike behave so pleasantly).
It's pretty common for fork springs to be one or two notches lighter than labeled. RaceTech supposedly measures all their springs before labeling but other manufacturers are often softer. That said, if your sag numbers are good leave it alone ;)
Scott
Quote from: koko64 on January 07, 2010, 12:26:54 PM
My sag numbers are 20mm static and 33-35 rider sag for the forks. how do they sound to you?
I could be wrong, but those seem a little high.
Are the numbers the same for the rear spring?
No, front and back are different. Check the link I posted. And those are a starting point, not carved in stone. It also has to feel right to you but if you're way outside that range chances are something is wrong.
Scott
static seems wrong. i need to grab a book and look.
Someone recently posted a mini sertup PDF.
What is a good range for the front?
Thanks for the advice guys.
Both front and rear sag are good.
I'll be seeing my suspension guy asap. I will ask him about the spring rates being optimistic. Time to fix it.
Cheers
Tony [drink]
Duh! Posted the wrong link. Will fix it later.
Just to clarify guys.
By rider sag I mean the total sag with the rider on the bike. So for the shock, the bike sinks say 8 mm without the rider and sinks about 33 mm with the rider. What I am refering to as rider sag is not the subtracted number. If you are taking the rider contribution to sag as 25mm then you are technically correct. My apologies as I'm giving the rider sag as the total sag number the "slack" way.
My mates and I have a "spring bank" as we keep all our springs from different bikes we have owned. This includes road and race bikes. I will see if I can withdraw 0.85's for the forks. No harm in testing and the weight of opinion is 0.85 for the forks (which is what I had in my Superlight). I will cross examine my suspension guy as to why he felt 0.95's were appropriate!
As for the shock, I will get quotes for revalving Vs replacement. The Aussie dollar is better against the Greenback than the Euro, so Penske would be the replacement shock I guess.
I will update with results.
Thank you all for your help and suggestions. It's great when riders on the same bike can compare data.
Thanks again.
Tony
The correct link for suspension setup: http://www.ohlins.com/Checkpoint-Ohlins/Setting-Up-Your-Bike/Underrubrik_1/ (http://www.ohlins.com/Checkpoint-Ohlins/Setting-Up-Your-Bike/Underrubrik_1/)
Scott
i love my penske.
(http://www.ohlins.com/PageFiles/304/CheckSagRideHeight_MCRT.jpg)
i have .85 springs in the front of mine. maybe they're cut down originals that check at .85, i forget now. .95 is what i have in my 851 with a lot more front bias.
one of the local suspension specialists recommend 8.0 spring in the back of a monster, which sounds very light to me. but one owner has it and loves it over the std, which is actually harder than that. you could also run a showa rear shock from an 851 or 888 if you can find one, but it also needs rebuilding.
I run .85 in front, but I have a 10. in the rear on an Öhlins. I had an 8 at one point on the stocker. I didn't like it. The damping was harsh.
Thanks. I have that Ohlins set up guide. It's nice and simple. I'ts the one I use.
I agree. I tried an 8.5kg spring on the shock and I couldn't get the sag numbers right for it being too soft. I'm 80-85kgs (180-190 lbs). That guy Brad mentioned may be lighter than me. I used a 9.8 kg spring and the numbers came good.
I will call a few mates and try to get a 0.85 spring to try.
Had a detailed discussion with my suspension guy.
We are going to fit a gold valve or equivalent piston and adjustable remote canister to the shock. My tuner feels that "providing greater gas volume will allow for more potential to tune the compression damping without excessive oil cavitation."
I can get rebuild and revalve with remote adjustable canister for $300-$400-00. It was at least $1500-00 for a new Ohlin's. I would pay half that at least without a re-valve for a used one.
After the rear end is sorted out, we will turn our attention to the front springs. My tuner's rationale for going with the heavier springs on a bike with a rearward weight bias, was to account for fork dive under braking (he does my NC30 400cc race bike). He also knows I try to get over the front of the Monster when riding harder.
Once I am happy with the rear I Will re-evaluate the front end and try 0.85 springs, and play with the oil level/air gap (they are re-valved already). I will consult him as I test.
I'll report back with my progress.
Hmm. That Ohlins price seems off. $1,500 USD? That's nearly double or so more than what I would expect to pay - $750-1,000, and only a respring would be necessary, no revalve of the ohlins. That being said, the racetech g2r revalving or whatever the equivalent for the shock would be loads cheaper still.
AFAIK, koko64 is in Australia.
Ah, that makes a difference here by a lot then.
Yes I'm in Australia.
Items like suspension and FCR's are double the price here. Buying them direct from the US is definitely worthwhile. The Euro is so strong if I was going for a new shock I would get a Penske instead of an Ohlins.
The shock will be receiving a new Racetech gold valve ($200-00), remote Kayaba canister and hose($60-00) with compression damping adjustment and set up/tuned for $100-00 to $140-00. So that's $360-00 to $400-00 all up with ongoing tuning support. This guy machine finishes the canister to make it all shiny.
The suspension guy had two main points regarding overcoming the inherent design flaws of the Sachs/Boge shock.
1. Replacing the piston (with a gold valve or other equivalent) and not just re-shimming the stock one, because the standard piston valve is so bad.
2. Providing a greater gas volume with the remote gas canister to prevent oil cavitation, and controlling compression with valving at the canister. There is too little gas volume and pretty useless compression valve control of the shock.
It's getting done next week.
While we are on Ohlins, anyone used them? Seems cheapest by far.
http://stores.ebay.com/Chicago-Performance-1_OHLINS-Suspension_W0QQ_fsubZ277075013QQ_sidZ821817633QQ_trksidZp4634Q2ec0Q2em322 (http://stores.ebay.com/Chicago-Performance-1_OHLINS-Suspension_W0QQ_fsubZ277075013QQ_sidZ821817633QQ_trksidZp4634Q2ec0Q2em322)
Cheers
i heard that an 888 shock will fit. loads cheaper if you can find one.
Got the shock overhauled today.
Total cost including all parts was $360-00. New piston/valve, shimmed with remote cannister and compression damping also re-shimmed.
I'm testing it over the next few days and can drop by the shop for shim stack adjustment when needed for no extra cost.
The bike is composed and turns in with good feel. I can feel the rear tyre now and there is no pitching. I didn't realise how badly the rear was affecting the front during turn in untill now.
Will test .9 and/or .85 springs when I settle on the shock settings. Will test oil heights also.
Glad to hear you've got it mostly sorted! [beer]
Thanks SD.
The bikes looking pretty trick with the remote resi.
Just spending the next couple of days working on damping and preload settings. Using my favorite roads and looking for the bumps I have in my mental map rather than avoiding them!
Believe it or not I am also testing some different shock springs (again). I've had the shock in and out three times since yesterday afternoon.The suspension guy fortunately used to work on 851 and 888 Corsa suspension for the Aus Superbike Championship. He had to go back and remember what he did back then! He gave me some advice about experimenting with spring rates and compression damping. Interesting..
In the end, if you want it set up 'just so', you have to fiddle around the base settings to get the ideal for how you ride. It's fun when you are starting in the ballpark, but hell when chasing your tail when you're not.
I'm on holidays at home (vacation) having a ball being a test rider for Team Me!.
Next test regime will be lighter fork springs from our "spring bank" with a little more oil height.
Are you still using the Eibach 9.5/550 spring?
Quote from: Speeddog on January 21, 2010, 08:02:04 AM
Are you still using the Eibach 9.5/550 spring?
I removed it on advice and went back to a lighter spring. "It can't hurt to try", I thought. I fitted an 8kg Eibach last night and used 20mm preload at the suggestion of the suspension guy.
I thought the spring would be too soft as 20mm is about the max I could get with the preload adjustment. He said he ran softer springs with particular compression damping rates due to the linkage set up. He described the linkage as 'strange' compared to other bikes.
It worked! ???
Could the progressive link be aggressive enough to require me to run a softer spring (with more preload) to allow for the 'ramping up' effect of the linkage in the later part of the stroke? I really don't know.
The 9.5 was way too hard in the last half of the stroke compared to this set up which surprised me (I'm 180-190/80-85).
I had tested an 8.5 and it was way too soft from our 'spring bank'. It was an Eibach with the number rubbed off.. Yep, when checked it was really a 7.5 [bang]. Contaminated methodology! No wonder my arse was draggin'.
This brings to mind Brad Blacks comment about a guy who tried a lighter spring set up from a certain suspension specialist. I'll ask Brad if it's the same guy. Maybe it's just a particular approach.
I also backed off the internal preload 5mm on the 0.95 fork springs. It was an improvement but 0.85-0.9's will be kinder to me.
More "test riding" today.
Hmmm.
I've not tested the early style suspension linkage for progression.
Not to be an arse, but have you checked that 8 kg Eibach to verify the rate?
[laugh]
It's an Eibach 450lber. It was calculated at a bit over 8KG by the suspension guy.
Does that sound correct to you?
I got static sag 10mm, rider sag 30-35mm with 20mm preload (spring down from 180mm free length to 160mm).
It's been the best combination so far.
Are you aware of a paradigm difference among suspension specialists, i.e. light spring heavy/compression damping Vs heavier spring/light compression damping?
Yeah, a 450 lb/in spring is 8.05 kg/mm.
I've not done any rear suspension tuning on the old-style Monster, so I'm going by data I've collected second hand. :P
I'm surprised you can get static/rider sag of 10/30 with 20mm preload on the spring.
I suspect that the hoop-style suspension linkage isn't very progressive.
The most important thing is that it's working the way you like it, or at least it's the best of what you've tried.
As far as suspension tuner 'philosophy' goes...
One of the folks here, stopintime, has an S2R800, and he got his suspension worked over.
His suspension tuner set him up with a *really* stiff spring, far stiffer than I would have.
But he's in Norway, and I'm in California.
I don't know how rough his roads are.
He likes the way it performs.
IMO, most race-oriented tuners are going to set a bike up pretty stiff.
Works good on a track, as they're quite a bit smoother than the street.
Quote from: Speeddog on January 21, 2010, 06:47:40 PM
................
One of the folks here, stopintime, has an S2R800, and he got his suspension worked over.
His suspension tuner set him up with a *really* stiff spring, far stiffer than I would have.
But he's in Norway, and I'm in California.
I don't know how rough his roads are.
He likes the way it performs.
..................
My spring is 150N (=857lbs/inch?) It's a very long spring - there are very few threads left to back out the preload. My understanding is that a longer spring will allow a more consistent action throughout it's travel. Don't know how much it's preloaded, but sag is 12mm and 36mm.
No compression adjuster on my WP 4014, but it was built for me with the "correct" valves. Rebound set at 5 clicks - played with 3 and 7 at the track - went back to 5.
Road conditions varies, but the bike is predictable and very stable. It's set up more towards track performance, not comfort. When I have a passenger it's still very stable, but obviously a softer ride.
Just to help clarify things a bit:
Stopintime is about 210-220 lbs.
S2R800 is the new style linkage, which seem to need a spring about 1.0 kg/mm stiffer than the old style linkage.
I would have set him up with an 11.6 kg/mm (650 lb/in).
His spring is about a 15.4 kg/mm.
I'm surprised you can get static/rider sag of 10/30 with 20mm preload on the spring.
[/quote]
Did you expect higher or lower numbers?
You know, just when I think I'm gaining a handle on suspension principles, a different but very valid logic appears.
I guess it's the decision about one's primary objectives and what area should be compromised, e.g. comfort Vs control.
Usually with a soft spring and lots of preload to get acceptable rider sag, static sag is very small or zero.
For street riding, it's indeed a matter of how you want to compromise.
And it's very subjective, and dependent on rider preference.
Racetrack, it's all in pursuit of lowest laptimes.
Quote from: Speeddog on January 21, 2010, 07:40:39 PM
S2R800 is the new style linkage, which seem to need a spring about 1.0 kg/mm stiffer than the old style linkage.
Are the DSS bikes the same linkage geometry as the S2R bikes? Wondering if shocks/springs between S2R and 800 Dark can interchange even though the swingarm is different.
Scott
Quote from: scott_araujo on January 21, 2010, 08:56:09 PM
Are the DSS bikes the same linkage geometry as the S2R bikes? Wondering if shocks/springs between S2R and 800 Dark can interchange even though the swingarm is different.
Scott
AFAIK, late model DSS and SSS are same linkage geometry.
I've got both styles 'in the house', so I can measure tomorrow....
Thanks :) I'd like to upgrade my rear spring on the existing rear shock of my 800 Dark. So few people do it there's little data. If I can at least cross over with the S2R guys that helps.
Scott
Im pretty sure they are the same.
manglebug has a late model DSS bike where the shock failed and i sent her my SSS shock which looked exactly the same.
I dont remember what happened, but im pretty sure she installed it and went on riding with it.
But if I recall from her shaved seat tutorial pics she's about half my size ;)
I think you're right though and they are the same. I think the aftermarket adjustable link for the rear is the same for both bikes which would also support that. I should stop being lazy and go look up the part numbers for both shocks online. :)
Scott
Went for a good 130 mile sport ride yesterday. The roads included pretty much every kind of road, corner and bump. There's great variety East and North East of Melbourne for that sort of thing.
I have to say I was impressed with the shock's performance. It's nice to feel what the rear tyre is doing! Planted with plenty of feedback, tracking on line, on the sport side of firm with good pitch control. The front feels more planted because the ride height increase I made at the back now works as intended. I will tweak the preload and the damping a little over the next few weeks.
The bike is composed now. No more bouncing off line, no more "rocking horsing", no more collapsing of the rear into bumps and unloading the front. There is good stability considering how sharply it steers. I can't speak for the later Monsters, but a well set up early Monster (888 chassis) can be a razor sharp back road weapon.
It makes me remember the 'Sport Rider' article (Feb 1996, p53) which stated, "Tremendously tight, exact handling package", and, "this 900's back road prowess is astounding", and "laser accurate steering". That article made me buy my first Ducati, a new 1995 Monster in 1996. The only new vehicle I've ever purchased.
It's good to have one again.
Bikes pretty much sorted.
Just a note to say thanks to everyone who contributed their ideas and suggestions.
It was good to have a sounding board and I hope this thread was of use to others.
Cheers [beer]
Isn't the free length of the Eibach spring 7"?
Does that extra .3 inch make a big difference over the stock spring?
Quote from: ajw85 on March 08, 2010, 08:11:20 AM
Isn't the free length of the Eibach spring 7"?
Does that extra .3 inch make a big difference over the stock spring?
My WP spring is about an inch longer. It was explained to me that a longer spring will behave better, with a more even resistance, throughout it's range. If it's noticeable for me? I don't know, but it sounds logical.
Quote from: stopintime on March 08, 2010, 11:32:08 AM
My WP spring is about an inch longer. It was explained to me that a longer spring will behave better, with a more even resistance, throughout it's range. If it's noticeable for me? I don't know, but it sounds logical.
If the spring is a linear spring the rate stay the same.
Quote from: howie on March 08, 2010, 12:13:23 PM
If the spring is a linear spring the rate stay the same.
Isn't the resistance stronger when it's near fully compressed than when it's at it's full length?
Surely, it must be ???
Peter Verdone Design website is very informative about the technical aspects of motorcycle suspension.
The site under the sub heading "Springs" mentions a Dan Kyle test which supports the idea that even linear springs behave a little 'progressively' as they are compressed, so according to those guys you're correct. Also, the shorter springs behaved progressively much earlier than the longer springs.
Peter Verdone also has a PVD Wiki site with various projects.
for the non-engineery types, springs go with hooke's law, like bears go with candybars:
http://en.wikipedia.org/wiki/Hooke's_law (http://en.wikipedia.org/wiki/Hooke's_law)
Quote from: ato memphis on March 09, 2010, 04:03:55 AM
for the non-engineery types, springs go with hooke's law, like bears go with candybars:
http://en.wikipedia.org/wiki/Hooke's_law (http://en.wikipedia.org/wiki/Hooke's_law)
Maybe I'm reading things into that wiki content, but it does says that the force with which the spring "wishes" to return, is greater the further away from it's unstretched/uncompressed state it has been forced, doesn't it? Meaning some progressive behaviour even for linear springs? Sounds obvious to me....
My spring wishes it were a pony. ;D
Like Ato says, ideal springs obey Hooke's law. Their wishes are irrelevant. If Kyle's springs misbehaved, they were compressed beyond their operating range, which is a bad practice.
What the Wiki means is that the force is proportional to a constant times the length of compression or extension, so the more it is compressed or extended, the more the force. The constant is the spring rate and it should not change unless the material reaches a yield state and its properties change.
+1
Quote from: battlecry on March 09, 2010, 01:30:32 PM
My spring wishes it were a pony. ;D
Like Ato says, ideal springs obey Hooke's law. Their wishes are irrelevant. If Kyle's springs misbehaved, they were compressed beyond their operating range, which is a bad practice.
What the Wiki means is that the force is proportional to a constant times the length of compression or extension, so the more it is compressed or extended, the more the force. The constant is the spring rate and it should not change unless the material reaches a yield state and its properties change.
There are some things here that I don't expect to fully master, but I'd like to establish a simple fact in my brain....
Please help me out - even a linear spring will resist compression with greater force when it's fully compressed than when it's just a little compressed, right? Meaning it's easier to compress a linear spring the first inch than the last inch?
Well, its a focus on the extremes in which it no longer behaves spring-like
Think of a spring stretched out as far as it will go. What does it begin to look like? A rod/rope/etc. No longer behaving spring like.
Think of a spring compressed as far as it will go. What does it look like? A hollow tube. No longer behaving spring like.
That much I understand, but I'm asking what it's behaviour is between the extremes. First and last inch different?
"Meaning it's easier to compress a linear spring the first inch than the last inch?"
Shouldn't be, Stopintime. But separate the concept of the force required to compress the spring an inch from the concept of the total force the spring is holding up. The first inch you compress a spring, the force to compress it that one inch, call it X, is the same as the total force the spring is holding up. If you keep compressing the spring, the force required to compress it from inch 3 to inch 4 will still be X, but it will be X on top of 3X and now the spring will be carrying 4X force.
Now it's beginning to sink in.
My reasoning makes sense to me, after reading the latest post.
Allow me - if I try to compress a spring by hand force, it will be easier the first inch than the second a.s.o.
Live bike action on the other hand, is working as described with the 3x and 4x story.
Am I getting closer?
I think you are there - what you mean by "easy" should be defined:
Its just as "easy" to go from 3-to-4, in that you are adding the same amount of force. No, you can't think "go in further, spring!" and not push any harder, you have to push the same you have been pushing for the existing compression, plus the unit amount to go further.
If it takes 50 lbs to push spring from a to b, then to go from a to c, you would need the force for a to b (50) plus b to c (50), net result :100.
This is different than non-linear springs.
In those "progressive rate" springs, you won't simply add another 50 lbs to compress another 1 inch (or whatever the rates might be). You would progressively have to add more and more force to compress the same distance. This would be like,
a to b = 50 lbs.
a to c = ab (50) + bc (55) = 105
a to d = ab (50) + bc (55) + cd (60) = 165
So to move from a to d, it would take 15 more lbs than a linear rate spring.
This is intriguing. (Never too old to learn) [coffee]
Ato - what I mean by "easy" is that if a person is only strong enough, by hand, to compress a spring by an inch, the same person won't be able to compress it the next inch.
If that's true, I will see it as a sign of a spring being progressive no matter what kind of spring it is. It might not be a correct technical term though.
No. That would be incorrect terminology.
If a person was only capable of compressing a spring 1 inch, regardless of spring type, they would be unable to compress the spring any further.
I think you are missing that the spring "stops" compressing until more force is applied. Whether its x more lbs to go z more inches, or if its x^y to go z more inches is the difference in naming.
Thanks, that's confirming my understanding. I'm far from understanding the physics, but that's ok.
Thread jack over, I guess ;D
i think it is a helpful threadjack section for those interested in progressive rate springs. More readings (more of a how-to, really): http://www.webbikeworld.com/motorcycle-shocks-suspension/progressive-fork-springs/ (http://www.webbikeworld.com/motorcycle-shocks-suspension/progressive-fork-springs/)
How about this:
'Linear' or 'straight rate' spring
For example, it's a 50 lb/inch spring.
It takes 50 lb to compress it the first inch.
It takes 50 lb *more* to compress it the second inch.
So, a total of 100 lb to compress it 2 inches.
150 lb to compress it 3 inches.
And so on...
'Progressive' spring
50 lb to compress it the first inch.
60 lbs *more* to compress it the second inch.
So, a total of 110 lb to compress it 2 inches.
70 lbs *more* to compress it the third inch.
So, 180 lb to compress it 3 inches.
...and your ass will never feel the nuances of linear springs becoming 'somewhat progressive'. ;D
<whispering>
Should I tell them that the rear suspension linkage is progressive?
</whispering>
Quote from: Speeddog on March 09, 2010, 05:13:15 PM
How about this:
'Linear' or 'straight rate' spring
For example, it's a 50 lb/inch spring.
It takes 50 lb to compress it the first inch.
It takes 50 lb *more* to compress it the second inch.
So, a total of 100 lb to compress it 2 inches.
150 lb to compress it 3 inches.
And so on...
'Progressive' spring
50 lb to compress it the first inch.
60 lbs *more* to compress it the second inch.
So, a total of 110 lb to compress it 2 inches.
70 lbs *more* to compress it the third inch.
So, 180 lb to compress it 3 inches.
Where were you when I needed you? [laugh]
In my mind (say what you will about it...) this is clear and obvious. The term "linear" is weak IMO - the resistance's growth might be linear (?), but the resistance itself is growing and could just as well be called.... progressive? :D
Quote from: Speeddog on March 09, 2010, 07:34:04 PM
<whispering>
Should I tell them that the rear suspension linkage is progressive?
</whispering>
I know, and I just might get back to you on that. Don't like it an will refuse to accept ;D
Quote from: ducpainter on March 09, 2010, 05:56:58 PM
...and your ass will never feel the nuances of linear springs becoming 'somewhat progressive'. ;D
Just so we're clear - you don't know what my ass is capable of. :o ;D
Quote from: stopintime on March 09, 2010, 10:51:21 PM
Where were you when I needed you? [laugh]
In my mind (say what you will about it...) this is clear and obvious. The term "linear" is weak IMO - the resistance's growth might be linear (?), but the resistance itself is growing and could just as well be called.... progressive? :D
Linear is a perfect word for its behavior - draw a graph: x-axis is compression; y-axis is force required - the line plotted would be linear - old school y=mx+b function.
Progressive would be behave differently - it would curve.
Speeddog's breakdown is way more concise than mine. However, I thought only some of the suspensions had a progressive linkage?
Quote from: stopintime on March 09, 2010, 10:51:21 PM
In my mind (say what you will about it...) this is clear and obvious. The term "linear" is weak IMO - the resistance's growth might be linear (?), but the resistance itself is growing and could just as well be called.... progressive? :D
It's a math thing. Throwing aside the slight progressive nature of all springs, if you plot compression vs. force for a linear spring on a graph you get a straight line. For example with a 1# per inch spring, 1" compression = 1# of force, 2" = 2# of force, 3" = 3#, etc.
Now with a progressive spring you might get something like 1" = 1#, 2" = 3#, 3" = 5.5#, etc. Plot that and you get a curve with a steeper slope as you apply more pressure.
Scott
This thread is awesome, thanks guys.
Too bad I bought a sachs 748 shock and not a showa 748 shock.
meh. look into racetech valving or something and be done with it.
Sure the fancier oem shocks have benefits, but a person can change the internals of the shocks, leaving the exterior as a mere housing and have something quite nice.
Quote from: ato memphis on March 10, 2010, 04:08:48 AM
~SNIP~
However, I thought only some of the suspensions had a progressive linkage?
SBK and ST-framed Monsters ('01 S4, all '02 and later with linkages) have progressive linkages.
851/hoop framed Monsters may have *some* progression.
I haven't done actual measurements on one, but the rocker is quite long, so I suspect not much progressivity.
Spring force will also change if the shock is mounted on an angle. As the swingarm goes up, the angle of the shock decreases which changes the force on the wheel.
Quote from: Armor on March 10, 2010, 08:10:51 AM
Spring force will also change if the shock is mounted on an angle. As the swingarm goes up, the angle of the shock decreases which changes the force on the wheel.
Maybe that's what the linkage is for - to counter that effect?
Time to threadjack the threadjack! [evil]
Quote from: Speeddog on March 10, 2010, 06:40:27 AM
SBK and ST-framed Monsters ('01 S4, all '02 and later with linkages) have progressive linkages.
851/hoop framed Monsters may have *some* progression.
I haven't done actual measurements on one, but the rocker is quite long, so I suspect not much progressivity.
How much difference in progression is there between the ST/SBK linkage and the 851/888 hoop type linkage? I have heard/read two quite different stories about this from different suspension people.
One guy said that the ST linkage was fitted to make it "more supple" compared to the hoop linkage while another guy said that the hoop linkage was
regressive at the last part of the shock stroke! The last comment was from a suspension guy who worked on 888 Corsas.
Did the factory change the linkage much from 888 to 900M?
Can anyone clarify/verify?
Quote from: koko64 on March 10, 2010, 11:55:07 AM
Time to threadjack the threadjack! [evil]
How much difference in progression is there between the ST/SBK linkage and the 851/888 hoop type linkage? I have heard/read two quite different stories about this from different suspension people.
One guy said that the ST linkage was fitted to make it "more supple" compared to the hoop linkage while another guy said that the hoop linkage was regressive at the last part of the shock stroke! The last comment was from a suspension guy who worked on 888 Corsas.
Did the factory change the linkage much from 888 to 900M?
Can anyone clarify/verify?
I'm fairly certain the linkage and rocker are the same between the 851/888 and M models with the hoop.
I know the parts will fit either bike, but I'm not certain all the rocker lengths are identical.
Nate, that's probably true on the bikes imported into the States, but the Strada and the S.P.O. or S.P.5. versions had different rockers. The S.P.O/5 frames had an adjustable eccentric in the rocker to change the linkage geometry through the Ohlins rear shock attachment point. The Strada just straighbolted the Showa shock to the rocker. Don't know how many of those made it here.
This fellow wrote a nice description of the S4R rear, and included some measurements:
http://www.ducatisti.co.uk/forum/technical-help/42566-s4r-rear-suspension.html (http://www.ducatisti.co.uk/forum/technical-help/42566-s4r-rear-suspension.html)
</threadjack>
Quote from: battlecry on March 10, 2010, 12:20:03 PM
Nate, that's probably true on the bikes imported into the States, but the Strada and the S.P.O. or S.P.5. versions had different rockers. The S.P.O/5 frames had an adjustable eccentric in the rocker to change the linkage geometry through the Ohlins rear shock attachment point. The Strada just straighbolted the Showa shock to the rocker. Don't know how many of those made it here.
This fellow wrote a nice description of the S4R rear, and included some measurements:
http://www.ducatisti.co.uk/forum/technical-help/42566-s4r-rear-suspension.html (http://www.ducatisti.co.uk/forum/technical-help/42566-s4r-rear-suspension.html)
</threadjack>
I realize that. [bang] I've seen the adjustable rocker, one on a Monster even, and should have mentioned it.
I guess I was just speaking to the Strada, and the fact the parts will bolt to all the bikes.
nah, we're just getting ancient [thumbsup]
Quote from: battlecry on March 10, 2010, 12:55:32 PM
nah, we're just getting ancient [thumbsup]
That too. ;)
Quote from: Speeddog on March 10, 2010, 06:40:27 AM
~SNIP~
I haven't done actual measurements on one, but the rocker is quite long, so I suspect not much progressivity.
Did some rough measurements of the only 851-style frame I've got at hand.
The rocker isn't really all *that* long.
So, I think it'll still be fairly progressive, but not as progressive as the ST/SBK style.
A definitive answer will require measurements that I can't do right now.
You know, Neil Spalding's book "Moto GP Technology" mentions some teams using regressive shock rate linkages. I don't understand this stuff real well except for setting up what I'm given by the suspension tech.
Anyone able to shed some light on this?