new front fork problem

[jerry]

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 a well known Ducati race shop in UK for overhaul recentlly and are in perfect condition they fitted the new springs and said it would be much more comfy and accurate on the bad roads here. They say the forks are perfect and not to mess with them, arrogant buggers ,they may work in UK conditions but having 2 Ducatis there I dont believe it.

[slob]

10W is definately too 'stiff' for the road in my experience.
Ducati recommended is SAE 7.5 (for a good reason)

[jerry]

Well today I set preload on forks to zero to see where the tie wrap went down to ,bumped up the rebound gamping 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 .

[Stafford]

Might be of use Jerry Technical/Fork_oil_replacement.pdf (http://www.mad-ducati.com/Technical/Fork_oil_replacement.pdf)

[Thirdway]

I'm suspecting they have fitted progressive springs ?

Many fit them because they make the initial ride more comfortable. Trouble is they are a big compromise and unless you are generally riding on smoothish tarmac they become a liability, being too hard on bigger compression particularly with braking and cornering. Unfortunately the forks damping system does not allow for progressive springs so you can end up with all sorts of problems.

There are always big arguments over this one, so before I start the war, let me say all my experience is based on specialist suspension companies like Maxton in the UK. They all say to use linear springs based on your current weight and riding style and to have the damping adjusted to match.

[chris.p]

I'm suspecting they have fitted progressive springs ?

Many fit them because they make the initial ride more comfortable. Trouble is they are a big compromise and unless you are generally riding on smoothish tarmac they become a liability, being too hard on bigger compression particularly with braking and cornering. Unfortunately the forks damping system does not allow for progressive springs so you can end up with all sorts of problems.

There are always big arguments over this one, so before I start the war, let me say all my experience is based on specialist suspension companies like Maxton in the UK. They all say to use linear springs based on your current weight and riding style and to have the damping adjusted to match.

I agree with the above and would also add that it would be a good idea to contact Maxton or K-Tech and seek there advice on the correct spring rate to suit your wheight & riding style.


Chris.

[jerry]

Maxton ,Ktech require the forks being sent to them which is not easy from thailand ,also The quotes i had from them it would be cheaper to buy a set of Ohlins forks off Ebay. The Ducati shop I sent the forks to has a great reputation but they have certainly damaged that with my forks as i wanted them revalved but they said that new Hyperpro springs was all that was required.That cost bme a lot to get the forks to UK and it looks as if they may have to go again or I may source some racetek valves and do it myself here.

[gary tompkins]

Single rate springs work best on Ducati forks - it what race teams use. I think the specified rate is 0.97 kg/mm for road use on the 916, which must be similar in weight to the S4. You also need to back damping off to zero when you set preload & sag, otherwise you are wasting your time.

[jerry]

Single rate springs work best on Ducati forks - it what race teams use. I think the specified rate is 0.97 kg/mm for road use on the 916, which must be similar in weight to the S4. You also need to back damping off to zero when you set preload & sag, otherwise you are wasting your time.

If single rate springs are supposedly what race teams use why is it thet the well known Ducati race shop that did my forks fitted HYPERPRO progressive rising rate springs ?
and also did not install the revalve that so many other people recommend ..the contradictions from so many different suspension specialists is baffling.

I have 61 pages of notes and adjustments over 2 years on same stretch of road that i have used and what seems to stand out of my experience is that with the Hyperpro springs in Handling is very accurate and sharp but ride quality is dangerous and uncomfortable but with standard Ducati springs ride quality is reasonable but handling is wallowy and not accurate . I have tried 5w oil 7.5w oil and now 10w the forks have been stripped 36 times for changes the compression shim valves are the only standard part left to change. unless i also change springs again.

[steve wright]

Requirements for racing are very different from road riding. Racing is very focused and the spring rate is very focused on control under braking (controlling the weight shift and it's effects) and also whilst changing up thru the gears to stop wallow and make the bike steer consistently (which causes the bike to steer imprecisely and thus miss "the line"). Single rate springs are used because that gives consistent performance and the damping remains matched all through the travel thus making the forks predictable to work with. Racing bikes spend nearly all the time either flat stick thru the gears (assuming no traction issues) or at near maximum braking force, otherwise you're slow! Comfort doesn't get a look in so springs can be relatively stiff to get good control.
Roadbikes however are designed to spend most of the time floating along at steadier throttle opening rates and gliding smoothly through bends where the forks aren't under anything like racing requirements. Road bikes are comfy things.Your braking distance on the road is probably about 3 times what it would be on a track day and your concentration level about 90% or less. Progressive springs allow the forks to work in a soft fashion for small amounts of travel soaking up undulations in the road. Lots of road corners you'll ride through with little or no brake as you're doing 40mph less as you approach (than if you were racing).
In the event you are braking hard then the progressive springs collapse quickly to the harder bit of the spring and thus decrease dive rate (and get the bike more stable) and give the damping an easier time. Road bike damping is softer, again for comfort reasons.
Ok I can see you're eyes are glazing over, that's my two penworth, I'll stop rambling.
Except to say i'm about to fit hyperpro springs to my M900Sie so i pray i don't get your issues! If I do I'd be reducing the compression damping for certain and maybe rebound followed by an oil lightening if that didn't work.

[chris.p]

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.

.

Ok, I have now re-read your post, the biggest clue is the "24mm of sag", I take it that is Static Sag, if so, it is to small, it should be between 25 to 30mm( that is what we use for racing, so for the road you could add between 3 to 5mm extra gap.). Your air gap is at the far end of the scale that runs from 110mm to 150mm, a good air gap is between 115 & 120mm, the air gap does not come into play till the last quarter of the fork travel, works like an air cushion and you adjust it to finalise your fork travel distance after your suspension is set to suit yourself.
The wheight if the fork oil effects the speed of the suspension depending on the way the shim stack has been built.


My first suggestion would be to contact Maxton or K-Tech and ask them to suggest the correct spring wheight to suit your -:

1/ Wheight.
2/ Bike.
3/ Road conditions
4/ Riding Style.


I have added a couple of PDF files for you to use. One is a problem sheet and the other is a setup sheet.

Chris.

It would appear that the PDF files are to big, if you pm me your email address I will send them to you that way.


Chris.

[Thirdway]

If single rate springs are supposedly what race teams use why is it thet the well known Ducati race shop that did my forks fitted HYPERPRO progressive rising rate springs ?
and also did not install the revalve that so many other people recommend ..the contradictions from so many different suspension specialists is baffling.

I have 61 pages of notes and adjustments over 2 years on same stretch of road that i have used and what seems to stand out of my experience is that with the Hyperpro springs in Handling is very accurate and sharp but ride quality is dangerous and uncomfortable but with standard Ducati springs ride quality is reasonable but handling is wallowy and not accurate . I have tried 5w oil 7.5w oil and now 10w the forks have been stripped 36 times for changes the compression shim valves are the only standard part left to change. unless i also change springs again.

I don't know about the Ducati shop. However I have gained enough cross related information through the likes of Maxton, K-Tech and Reactive and internet articles to confidently say that, unless you are riding a cruiser style bike, then progressive springs are are definitely not recommended. They are a compromise only and will seriously mess up handling/ride quality. This is for road use and not just track bikes. As others have said, give Maxton, K-Tech and Reactive a ring as they can confirm these things in a far more elequent way.

[jerry]

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 or Moto Rapido for Racetech Gold valves and springs . The Hyperpro springs are going back to the dealer who recommended them.either for a refund or EBAY.

KTeck have told me thay have no data on spring rates /damping for Ducati S4 forks and quoted me a complete fork package that i cannot afford £1680 ...that rules them out Too expensive .

thanks everyone for all the input I will keep adding posts as the work progresses.

[Thirdway]

KTeck have told me thay have no data on spring rates /damping for Ducati S4 forks and quoted me a complete fork package that i cannot afford £1680 ...that rules them out Too expensive .

.

phew. My guess, for a revalve, new springs and a rebuild from Maxton around £600.00. Had two bikes worked on by Maxton and have been full satisfied with the results.

[crust]

I have the full racetech package in my forks from PDQ

Very happy with them though you do need the racetech oil, sadly its very expensive at £17 a bottle last time and you'll need two bottles.

:) crust

[jerry]

Crust you were diddled at £34 for 2 bottles of RACETECH oil .....its made up for Racetech by Spectro oils and is a repackaged fork oil . Same as Hyperpro who get their oil made by either Belray or Putoline .

I use motul or Rock racing fork oil its all the same but much cheaper.


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 .

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 £1100 last year on spares in their shop.

[steve wright]

Quote
"The Hypepro springs are out now they have twice as many coils as the standard Ducati springs for the same length"

Intrigueing, the more coils per inch you have the softer the spring will be for the same gauge wire. Were these springs longer than standard? and if so is there a spacer in the S4 forks which should be left out/shortened when fitting? If not it will have the effect of loads of preload which may explain your unusual static sag reading.

[slob]

Jerry, why do you insist on trying SAE5 or SAE10 when you should get the best results with SAE7.5?

[jerry]

Because Hyperpro said use 10w

and 5w worked reasoably well with standard springs in all my other Ducatis wheras with standard springs and 7.5w the standard valving is poor with 5w it works OK .Many dealers use 5w instead of 7.5w .

also in Thailand 7,5 is not available.

[gary tompkins]

You can mix different grades of the same oil to get an in-between spec.

My mate did it to get the set up on his GPZ900 spot on with Racetech internals and single rate springs

[Capo]

Because Hyperpro said use 10w

and 5w worked reasoably well with standard springs in all my other Ducatis wheras with standard springs and 7.5w the standard valving is poor with 5w it works OK .Many dealers use 5w instead of 7.5w .

also in Thailand 7,5 is not available.

Correct me if I'm wrong but didn't they also say which spring you should use?

I don't know who your 'dealer' is (or was) but I would recommend you stick with someone who knows Ducati's. JHP springs to mind.

[crust]

Crust you were diddled at £34 for 2 bottles of RACETECH oil .....its made up for Racetech by Spectro oils and is a repackaged fork oil . Same as Hyperpro who get their oil made by either Belray or Putoline .



No, I wasted a lot of time/money playing around with other fork oils, then after chatting with Larry that owns PDQ he admitted they'd done the same.

He then sold me the Racetech oil and amazingly he was right, it does work the best.

The blend is matched to the the valves.

:) crust

[jerry]

Correct me if I'm wrong but didn't they also say which spring you should use?

I don't know who your 'dealer' is (or was) but I would recommend you stick with someone who knows Ducati's. JHP springs to mind.

The dealer was Proteam. thats what annoys me as they are reputed to be experts.

[gary tompkins]

Useful write up on S4 fork upgrade here using Racetech parts

http://waste.org/~knobs/fork_rebuild1.html

He was installing these on a Sportclassic so 0.95kg spring rate might be a bit soft

Watercooled bikes have more weight over the front wheel

[jerry]

Thanks gary I had that very informative site already.

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 comprssion 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 .

[chris.p]

This may help in your setup, it does not mention go into preload, rebound or compression setting for the forks, but is a good base to start from.





SUSPENSION SETUP

FRONT FORKS.

Remove the fork tops, spacers and springs, collapse the fork leg upper down onto the fork leg lower, the air gap can now be measured.

Ideal gap is between 110mm and 120mm, outer range being 100mm and 150mm.


RIDER SAG.

Should be between 30mm to 45mm ideal being 40mm.

Sag____________

Spring Weight________

Suspension Oil Weight_______



Air Gap_________

STATIC SAG

Once you have set your rider sag, the static sag should be checked ( this goes for both front & rear)

Should be between 25mm to 30mm

Sag____________

If there is to much sag a harder spring will be required, if there is to little sag a softer spring will be required.

And for the rear shock.


REAR SHOCK.

RIDER SAG

Should be between 30mm to 40mm


Sag________

STATIC SAG.

Once you have set your rider sag, the static sag should be checked ( this goes for both front & rear)

This should be between 7mm to 16mm, ideal being around 10mm.

Sag________

Spring Weight______

If there is to much sag a harder spring will be required, if there is to little sag a softer spring will be required.



Rebound Setting_______


Compression Setting_________

[chris.p]

This may also be of help.


A few technical terms explained
Before you actually start your test rides, it is worthwhile knowing a little shock-absorber jargon. To start with, spring pre-load. This setting influences the height at which your motorcycle will ride. The higher the spring pre-load, the higher the riding height of the motorcycle. The spring pre-load can be adjusted by turning the spring collar/spring retainers, which may also be fitted with a locking ring. When you place the motorcycle on its wheels, the front fork will settle, by several centimetres, under the weight (sprung mass) of the bike. This is known as the "negative spring distance", "sag" or "neutral riding position". This negative spring distance (without rider) should be somewhere between 15% and 35% of the total spring distance (fork or shock stroke). Example: the total spring distance is 120 mm. The negative spring distance therefore should be between 20 and 40 mm. This can be easily measured by winding a cable tie around the shock-absorber spindle(s). With rider, the spring distance should be between 35% and 50%. Example: the total spring distance is 70 mm, so the negative spring distance should vary between 25 and 35 mm.

Compression absorption occurs when a shock-absorber or front fork is compressed, while rebound or bump absorption describes the opposite effect.

From diagnosis to therapy
To help you rapidly find the source of your problems (and then solve them) what follows is a brief total overview of several different suspension problems.


TROUBLE SHOOTING OVERVIEW

REAR SUSPENSION

Complaint
too little negative suspension travel
motorcycle shocks through the steering in ruts or when accelerating
shock absorber appears immobile
uncomfortable
overloading on front forks when travelling downhill or braking
Cause
spring pre load too high
Solution
reduce spring pre load
fit a softer spring if necessary
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Complaint
motorcycle dips too deeply on suspension
too much negative suspension travel (“sag”)
uncomfortable
tendency to shocking
motorcycle wanders on uneven surfaces
Cause
spring pre load too low
Solution
increase spring pre load
fit a harder spring (or springs)
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Complaint
very uncomfortable
rear wheel tends to bounce in fast bends especially when accelerating
rear wheel bounces over uneven surfaces
Cause
compression camping too hard
Solution
adjust damping to softer level
have the shock absorber adjusted internally
have worn shock absorbers repaired or replaced
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Complaint
Rear suspension bottoms out
motorcycle and rider subject to hard bumps
Noticeable movements in the frame, particularly when accelerating out of bends
Cause
compression damping too soft
Solution
set compression damping harder
have the shock absorber adjusted internally
have worn shock absorbers repaired or replaced
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

[chris.p]

Complaint
Rear suspension bottoms out
motorcycle and rider subject to hard bumps
Noticeable movements in the frame, particularly when accelerating out of bends
Cause
compression damping too soft
Solution
set compression damping harder
have the shock absorber adjusted internally
have worn shock absorbers repaired or replaced
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Complaint
motorcycle suspension extremely sluggish
rear wheel unable to cope well with uneven surfaces
tendency to bounce on bumpy surfaces
uncomfortable
tendency to snake in ruts
Cause
rebound damping too hard
Solution
decrease the rebound damping
possibly increase spring pre-load
replace shock absorber
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Complaint
motorcycle suspension extremely lively
constant movement in the rear suspension
rear wheel has tendency to bounce / wobble
Cause
rebound damping (rebound) too soft
Solution
increase the rebound damping
reduce the spring pretension if necessary
have worn shock absorbers repaired or replaced
-----------------------------------------------------------------------

[chris.p]

FRONT SUSPENSION
Complaint
front forks sluggish/nearly immobile
handlebars “jump” in your hand when accelerating and crossing ruts
uncomfortable
front wheel bounces / chatters on poor road surfaces
Cause
spring pre load too high
spring too hard
air chamber too small
Solution
reduce spring pre load
fit softer springs or progressive springs with a lighter initial strength
increase air chamber (reduce oil level in front fork)
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Complaint
motorcycle sags to deeply on the springs
too much negative suspension travel
suspension occasionally bottoms out
front forks shake when braking and travelling downhill
Cause
spring pre load too low
springs too soft
air chamber too large
Solution
increase spring pre load
fit stiffer springs or progressive front fork springs with a heavier initial strength
reduce air chamber (increase oil level in front fork)
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Complaint
front forks sluggish/nearly immobile
shocks in the steering when accelerating
front wheel chatters when braking hard
Cause
ingoing (compression) damping too hard
Solution
reduce the ingoing (compression) damping
possibly use lower viscosity fork oil
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Complaint
front forks shock when braking and on uneven road surfaces
and dips rapidly when braking
Cause
ingoing (compression) damping too soft
Solution
increase the ingoing (compression) damping
possibly use higher viscosity fork oil
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Complaint
front forks spring back slowly
uncomfortable
front wheel unable to cope with uneven surfaces
indirect steering behaviour
Cause
outgoing (rebound) damping too hard
Solution
reduce the outgoing (rebound) damping
possibly use a lower viscosity fork oil
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Complaint
front end is lively
bouncing and shocking on uneven surfaces
front forks spring back too quickly
Cause
outgoing (rebound) damping too soft
Solution
increase the outgoing (rebound) damping
possibly use a higher viscosity fork oil
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Complaint
front forks shock
front wheel shudders
not enough progressive hardening of the spring towards the end of travel
Cause
air chamber too large
Solution
increase the oil level in small steps of 5 to 10 mm
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Complaint
forks hard
tendency to shock in the steering
front wheel bounces when braking due to hydraulic stop blocking
uncomfortable
Cause
air chamber too small
Solution
decrease the oil level in small steps of 5 to 10 mm
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

[Thirdway]

It's a good set of instructions, however a couple of points.

1. Not all bikes have a simple fork setup and you can't always set up static sag on the front forks in the conventional way (try it with a Honda CBR600RR).

2. Some of the suspension problems can easily be attributed to poor rider control, shutting off/neutral throttle through bends, holding too tight, stiff arms and body and not letting legs take some of the shock, bracing against the bars when braking instead of gripping the tank. Just a few rider problems to start with and there are lots more.

[chris.p]

[QUOTE=Thirdway;335701]It's a good set of instructions, however a couple of points.

1. Not all bikes have a simple fork setup and you can't always set up static sag on the front forks in the conventional way (try it with a Honda CBR600RR).

The fork setup instructions are for Ducati Showa Forks, so should not be a problem.


Chris.

[jerry]

Chris ..yes i had all that data already.. i also rape the web for info ....its a good post .

i did another 100km today and the forks are nicely compliant and the handling is reasonable ....The people at proteam are going to have some explaining to do over the Hyperpro springs in March.

off course a benefit of all this struggle and research is that i am becoming very good at stripping forks , and a little wiser about the black art of suspension.

jerry

[jerry]

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 opened up the cartridge and drilled some bigger holes in the shim stack according to a chart and date 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 £40.

[gary tompkins]

There's possibly a moral or two in there somewhere

[jerry]

There's possibly a moral or two in there somewhere
yeah but it eludes me ..

[Capo]

Chris ..yes i had all that data already.. i also rape the web for info ....its a good post .

i did another 100km today and the forks are nicely compliant and the handling is reasonable ....The people at proteam are going to have some explaining to do over the Hyperpro springs in March.

off course a benefit of all this struggle and research is that i am becoming very good at stripping forks , and a little wiser about the black art of suspension.

jerry

Is this the same proteam who were being lauded here recently?

[jerry]

Is this the same proteam who were being lauded here recently?

No my apologies to PROTEAM ..It was PROTWINS who sold me the Hyperpro Spring that is totally wrong . Protwins also sold me a nice OHLINS rear schock which is genuine and really sorted the rear .