My S4 forks are now dangerously hard at speeds above 70mph on anything more than a racetrack smooth surface ,below that speed they are usable but harsh. They have lost all compliance since fitting the recommended Hyperpro springs with Hyperpro 10w fork oil , the old Ducati springs could be compliant with 5w oil but handling was mushy even with many setups of compression damping and rebound tried. The Hypepro springs have made the handling accurate but ride comfort and safety at speed is now bad.
The oil is 10w and air gap is 150mm . compression is set at 2 clicks with 8 on 7 rebound ,sag is 24mm but bike is not using full suspension travel so i suspect ,springs are too hard or oil level to high and 10w oil to stiff.
Dont say fit OHLINS forks its not an option here and as to suspension gurus in Thailand I am on my own , the forks have been to race shop in UK for overhaul recentlly and are in perfect condition
Well today I set preload on forks to zero to see where the tie wrap went down to ,bumped up the rebound damping to 10 leaving compression at 2 ......it was a bit better but the tie wrap does not go nearer than 25mm to the bottom of the fork even under extreme braking so i reckon the new springs are too hard or most likely the air gap is not enough so when I get back from Xmas familt holiday to Chiangmai in the car I will drain 10mm oil out and see what happens ... then try a change back to 5w oil after that .
Handling of front end is very accurate now ,just ride quality thats nasty
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MONSTERMAN
You never told us the spring rate of the springs you put in or what you weigh w/ riding gear. Sounds like the springs are way too stiff for you (I said stiff...).
A description of road conditions would be good also since most of us never ride where you live. You might also consider adding Race Tech valves to your shopping list.
Did you ever check sag after fitting the springs?
The springs are set for 180lb rider with full kit sag was set as per Hyperpro recommendations i then tried max sag today= zero preloada and still too stiff . a zip tie attached to forks does not get nearer tha 25mm from bottom.
Roads here vary between smooth tarmac to concrete roads to tarmac that is very bumpy from rain striations or slowly undulating from semisubsidance of the underlay all types are common .add in pot holes and ruts at random.
I got 2 friends who have 916 and a M696 to ride the bike today and both were terrified once the bike went over 70mph .
The 916 owner has his setup for trackdays and his forks are similar to mine and standard apart from 5w oil and ohlins spring his forks are very compliant ,and accurate ,he reckons mine have too much oil in (oil lock) but I set airgap as directed by hyperpro at 150mm. He liked the accuracy of the steering and the ohlins rear but the front end is way to firm .
10w sounds like way to much to me. When I went thru my Z1000 front end I used Bel Ray US1 synthetic. Which I believe correlates to 5w and it was FIRM. Nothing near what you are describing, but firm. [thumbsup]
What rate are the hyperpro springs?
Try opening the compression adjusters up.
I don't think that'll fix it, but it may give you confirmation that less compression damping is the proper direction.
With the info so far, I'd say go to 7wt oil.
OEM S4 valving is pretty harsh.
It would be good to know the actual spring rate and your actual geared weight.
Also, the rider sag (24mm initially?) is one of two sag numbers that tell the spring story. The relationship between the free sag and the rider sag is important.
Is your stiction value high? Make sure the axle and forks are correctly aligned and installed. Lots of stiction could point to a binding issue, and that'll make things feel harsh.
For oil level, after you have the other things squared away you can put a zip tie on and do some 60-0mph hard stops on a smooth surface to check travel. Remove a few mm of oil at a time to use most of the travel. You don't want to bottom it out and this is fine-tuning if you are starting out at an appropriate oil level.
Thinner oil should be the right direction to go in, but the effects on high-speed compression might be minimal. Might need to be revalved to achieve nirvana.
BK
Quote from: hypurone on December 22, 2009, 05:06:34 AM
10w sounds like way to much to me. When I went thru my Z1000 front end I used Bel Ray US1 synthetic. Which I believe correlates to 5w and it was FIRM. Nothing near what you are describing, but firm. [thumbsup]
+1. When I resprung my Marzocchis I went with (stiff) .95 RaceTech springs and DOWN from standard 7.5w oil to 5w. It feels stiff now but not jarring. My test run was running over 2" drop sewer grates at 50mph. Handled very well with none of the mushy dive and jarring handlebar feel I had on softer stock springs with heavier oil.
The fact that you notice them being too stiff at speed seems to indicate that the damping is what's to blame. If it was too stiff a spring they would feel too stiff at all speeds.
If your springs are correct you should be able to get away with less damping, as long as it doesn't pogo you're fine. Some folks don't care for the feel but set your sag properly and then swap out the oil for a lighter weight, set compression and damping to stock recommended, and see how you like it.
Also, go with stock air space whatever that is for your forks. Reduced air space is only really needed if you're undersprung and/or bottoming excessively.
Also, oil is quick to swap out and cheaper than another set of springs ;)
Scott
It will have to wait until New year now as am taking family on a car trip over the holidays but I plan to do all the sensible suggestions and will post again on results .
Cheers Jerry
I agree it's more than likely a damping issue...over stiff springs will not make things as drastic as you describe.
Oil weight or height will help.
Quote from: koko64 on December 23, 2009, 03:31:58 AM
Note too that whatever the manual says about oil volume has little to do with the resulting oil level/height! It should, but it doesn't and I've been caught out by that one! You can forget volume and just go by air gap/oil height! [bang]
Big +1.
And try to vary only one thing at a time. More than one thing at a time and you can't tell if any single change was good or bad.
I have been working on the damn forks now for 2 years I have a notebook full of each adjustment running to 61 pages .I am now being told by other suspension gurus that progressive springs are what is causing my problem and to go back to the rubbish ducati linears springs ,.I test each mod on same road . This aint science its a black art ...hell i can write a powercommander map that works without a dyno, rebuild scrap 8v heads that rock but these forks are something else????
it really sounds like oil lockup
progressive springs are better on a cruiser/tourer not a sport bike, but that's not your problem.
have you double checked the oil level? valve function?
Quote from: koko64 on December 25, 2009, 02:18:03 PM
I feel for you mate. Sorry we're not nearby to come over with a few beers and help you out.
It really does sound like it could be oil "lock up" (hydraulic lock). Get some oil out to see if it improves. Take a fair bit out coz it's easier to put more back in than pulling those buggers off to take more out again!
use a syringe with a long tube.. snake it down the middle or on the side of the spring. you can do it on the bike.
Quote from: jerryz on December 25, 2009, 06:42:21 AM
I have been working on the damn forks now for 2 years I have a notebook full of each adjustment running to 61 pages .I am now being told by other suspension gurus that progressive springs are what is causing my problem and to go back to the rubbish ducati linears springs ,.I test each mod on same road . This aint science its a black art ...hell i can write a powercommander map that works without a dyno, rebuild scrap 8v heads that rock but these forks are something else????
Progressive springs suck.
The springs installed by the factory are probably wrong for your weight....and I believe were progressive also...at least the ones in my bike were.
How much do you weigh? Have you checked sag on your bike?
It only a black art because you don't understand it. ;)
Quote from: ducpainter on December 27, 2009, 01:49:15 PM
It only a black art because you don't understand it. ;)
Well said DP. Some of the adjustment comes down to rider preference but you should be able to get into the ballpark by getting the right springs, sag, and an oil that is about right. Then minor adjustments with some ride time in between will fine tune it.
Scott
Half the Suspension experts say Progressive springs are the way to go the rest say linear springs are the way to go the standard springs in my S4 are linear and are great for comfort but lousy for handling, the Hyperpro springs are great for handling but lousy for comfort ...who is right?
.I have 2 years of testing and adjustments 61 pages of notes and ...No answers. Ha .
61 pages of notes?
but you are writing with a large crayon and it's a 2x3" notepad?
[laugh]
ok, seriously. maybe it's time to start from scratch. if what you've ended up with is wrong, using the same formula to "fix" it is just going to end up in the same place.
Maybe start with a full rebuild and inspection of the internals. Do you have the original springs? try using them again.
I'm anal, when I rebuild a shock, i leave it to drain over night so I can measure how much oil was in it. When you refill it to the right level, use a graduated container so you can compare to the prior amount.
Quote from: jerryz on December 28, 2009, 02:24:58 AM
Half the Suspension experts say Progressive springs are the way to go the rest say linear springs are the way to go the standard springs in my S4 are linear and are great for comfort but lousy for handling, the Hyperpro springs are great for handling but lousy for comfort ...who is right?
.I have 2 years of testing and adjustments 61 pages of notes and ...No answers. Ha .
I believe linear springs are superior. The stock fork springs are too light for most riders, also the stock valve in the S4 forks is very stiff. It's called undersprung and overdamped. That combination will make for poor handling and a harsh ride. That was your complaint...correct?
You never said if you ever actually
measured sag to determine if the spring you are using is correct, or correctly preloaded. You also haven't said how much you weigh. Believe it or not a stiffer spring will improve the ride quality.
If you're looking for supple
and precise IMO you are going to have to upgrade to a racetech gold valve with a custom stack, and be certain you are running the correct spring. If you don't want to do that you'll have to accept the compromise of modifying oil weight and height to alter the damping. The correct spring is a must regardless.
So post up some actual numbers if you want help.
That said, getting the right spring is the first step. Different oil viscosities are the most inexpensive way to change damping but not as precise as adjustable suspension with custom shim stacks.
Scott
I am going back to basics ...will re install standard ducati springs as i know they offer a comfortable and safe ride with 5w Motul fork oil , the handling is not super accurate but the bike is safe and usable . i will also drop the forks another 5mm and move the the risers/bars to 30mm forward to get more weight on the front .I will play with that setup until April when the forks can go to UK and to PDQ developments for Racetech Gold valves and springs . The Hyperpro springs are going back to the dealer who recommended them.either for a refund or EBAY.
thanks everyone for all the input I will keep adding posts as the work progresses.
The Hypepro springs are out now they have twice as many coils as the standard Ducati springs for the same length and virtually no give at the top progressive end ,that is the problem.
I will reinstall the standard springs for now with 5w oil and wait till i go UK and take the forks to PDQ in UK for racetech revalve and linear correct weight springs.
Oh yeah spoke to the Surrey dealer who sold me the Hyperpro springs and he has refused a refund ...dirrrr he says they use them on Raceteam bikes and they are good .He was really patronising and rude so now they have lost a good customer who spent over $1700 last year on spares in their shop.
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MONSTERMAN
Photograph them next to the stock springs or bring them both in and talk to him again? Maybe the springs were mislabeled.
Quote from: ducatiz on January 02, 2010, 02:50:04 AM
Photograph them next to the stock springs or bring them both in and talk to him again? Maybe the springs were mislabeled.
OH I will ..its only fair, the Hyperpro srings are so stiff they could hold a truck. but that will be in march when i go UK.
OK update........ its all back to basics with the standard Ducati springs refitted and Showa 8 weight oi with 135mm airgap. After consulting my notes i decided to have have compression set at 4 clicks in ,rebound is set at 9 clicks and sag at 24mm already before even riding it is evident that the standard springs move as the bike settles on its suspension.then went for a 60 mile ride on my standard loop around Chonburi Rayong area, in bends the bike felt good , comfort was good the bike is now safe at high speed over bumpy roads as the springs actually work instead of locking up.
The handling is reasonably good as well ,pretty stable so the bike is now usable and safe...Its not perfect but for now until the forks come to UK in March It will do.
Oh yes i also moved the bars 10cm forward and 2cm higher by using different riser so a bit more weight on the front also helps stability and steering .
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MONSTERMAN
Great to hear that you found a safe compromise untill you find that ideal set up. And congratulations on your epic journey!
Cheers
Tony
Sorted at last ......Met a German chap from YSS suspension at the Bangkok bike show, mentioned my fork problem and he said drop them in to YSS workshops,they design suspension systems for bikes and have a huge factory ,they opened up the cartridge and drilled some bigger holes in the shim stack according to a chart and data he has .He also checked my springs and said the standard Ducati ones are fine for my weight .The Progressive Hyperpro springs he said were completely wrong they are way too stiff even if I was 150kg. Not 80kg. we put 8w oil back in and hey presto the forks are really nice now went for a 150mile ride and the handling is noow superb as it should be , oh and the cost from YSS only $60.
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MONSTERMAN
Excellent!! [thumbsup]