M900 suspension question

[koko64]

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
Tony

[Link]

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.

[koko64]

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

[scott_araujo]

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

[koko64]

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

[greenmonster]

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.

[koko64]

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

[Link]

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 ?

[koko64]

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

[scott_araujo]

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/2009/11/0082723

Oops!  Here's the right link: 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

[Speeddog]

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?

[koko64]

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! .

Cheers
Tony

[junior varsity]

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).

[scott_araujo]

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

[Michael]

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?