Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 999 / 749 > Front end feel.....

[JPM]

After having problems with the back end of my bike and having a heavier spring fitted via JHP and the rear now feels fully planted the front feels skippy and light when pushed as I have found out on the last two track days.

One being yesterday at Silverstone , the front felt all "bouncy" and twitching - technical terms there eh? after adjusting the steering damper the head shakes died down and the bike felt somewhat more stable but there were a few corners where the front really struggled, namely club corner as it's a sweeping right hander which is off camber also, everytime I tried to get on the gas I could feel the front trying to tuck under me, so I'd end up losing so much drive out the corner I'd lose 50 yards on the guy in front and chase them round for another 3 miles before I could get back onto them again only for the same thing to happen.

I know nothing about suspension etc, and when you're on a trackday it's hard to gauge what's going right or wrong and make an adjustment without the knowledge to do so, so left everything as it was, but it's annoying as I know I have been faster, smoother on previous bikes, and this one should be in theory faster and more capable.

I know there's a shim/revalve kit for the forks as one or two people off here and a friend has had it done, but I don't know if doing that would actually fix my problem, do I take it to the likes of Maxton/K-Tech or a specialist suspension place and let them sort it? I get the feeling I'll have similar problems in 2 weeks at brands, so it's a matter of getting it done in the mean time.

Any help etc would be good guys..

[Edited on 20-6-2005 by JPM]

[skidlids]

Jon have you got a tie-wrap on the fork leg if so how much travel have you got left.
Fitting the stiffer rear spring will have altered the weight bias towards the front making the front carry more load, you may have to increase your preload to compensate or maybe add some compression and rebound damping to cope with the extra load. You may even find the fork springs are now to soft and as they are Ohlins forks I suspect they already have single rate springs.

[andyb]

JPM, i had the shim/valve upgrade done by jhp. I would say you can notice the action of the forks are smoother, ie less sticktion.

I did ask you where your forks sit in the yolks. I know there are a lot of views on this, but if you stick with one, ie jhp, i dont think youll go far wrong. If hes done the work to your rear end,ooh er, i would go with him on the front. They learnt so much in BSS and are still learning. I set mine to 15mm from top of yolk to top of fork leg, o the direction of JHP, this is mid way on his direction. The result of all my front end mods, coupled with the rest of the bike, does give a, dare i say 998 planted type of feel.
Remember its early days in the 999 set up history!

[JPM]

Skids got a tie wrap on the forks yes, probably got 10mm of travel left, so I would think that's OK

Andyb my forks just sit with one line showing through the yokes, John just did some "tinkering" on the settings there although did recommend the shim kit, but as I'd wheeled my bike in for something completely different he/they basically didn't have time to do anything other than that.

[electricsheep]

just a thought..

the seat tank can be moved back and forward on a 999

when i got my bike serviced they put the seat/tank back in a different position from where I normally have it set.

The bike felt horrible until I realised what had happened and put it back. I was amased at how much difference such a small adjustment made.

[keefer]

Originally posted by JPM
Skids got a tie wrap on the forks yes, probably got 10mm of travel left, so I would think that's OK

with 1cm left id say you are on the bump stop.
wind them up some then see how it feels. you can always go back

[Edited on 20-6-2005 by keefer]

[Totto]

I would try more front preload would agree with Skidlids , not an expert but after playing with my 998 suspension for two years & TWO fork revalves later i seem to have gotten a good setting for me

ON second thoughts just phone K-tech like i do

I have listen to so many so called experts i ended up chasing my tial for over a year ( not talking about anyone on this board ) as it has been a great help , speak to the people who run race teams ,if poss Ducati race teams

Also find out what you have in the front ie spring rate before talking to the experts as they will need to know

[Gizmo]

I'll dive in not claiming to be any kind of expert

Lots of possible causes. What's the sag like with you on bike front and rear??the Ohlins website has a useful sheet to record the info on, its always worth keeping this info along with measuring length of rear shock spring and tie rod even after the experts have worked on it, you might need to put it back there one day. Spring should be 160mm long uncompressed, measure it from edge to edge so you can check preload, typically it'll be 148 -150mm depending upon spring etc.

My best guess would be too soft a fork spring in forks, too little preload, not enough compression damping or too much rebound dependiing upon where it was happening.

First step is to get forks set right and for sag/preload and if needed a spring swap. personally I'm not a fan of progressive springs, at the high angles of lean a track bike runs at your forks need to move a lot further for a given bump size and i'd rather have a spring that lets them do that not increases as it compresses.

Was the corner bumpy and would you say bike was "hard"?? if so thats the forks not recovering quickly enough from too much rebound. it also means at that point you are running a steeper head angle as fork is further into its travel. Depends upon angle of lean at the time as it isnt so important as you lean further. Can also happen if its a hard on brakes and then tipping in fast corner, fork doesn't return fully from the brake compression, bike tips in sharply feels like it's tucking and suspension can't react so feels hard and bumpy.

if its on smoother tarmac has it got a loose bouncy feel like the spring isn't under control?? if so increase rebound.

After that its analysis of what was happening and what you were feeling, go back through it in your head, even better when you are riding and you get a problem its always worth doing a slower lap just to see what happens then or even take the one problem part in isolation, try a different line or body position just so you've got something to compare it to. try coming off the brakes earlier and letting suspension return before going in or leaving off power on exit to see what happens. This is where good suspension guys earn their money, trying to use the feedback and make sense of it but they need info to work with ( unless you have a nice high Khz datalogger fitted ) The more info you can give them the easier it is for them to diagnose the problem and set it up. if you've got all your sag/spring/preload settigns recorded its even easier for them.

[JPM]

Right just spoke to K-Tech, very nice guys just to see if they can shed some light on things, they gave me some base settings for the front end

28mm static sag
Comp - 6 to 8 clicks out
Rebound - 14 clicks out

Think I'll take a note of what I have got and give it a go. A few questions though static sag? I'm guessing I need to lift the front of the bike off the ground measure the length of fork leg exposed, drop again and re-measure? and then adjust via preload (blue nut - technical eh?)

Gizmo, I kind of got half of what you said, then it went blah, blah, blah As for a description well tip in 2nd gear probably doing 60-70mph knee down, and the front feels like it's skipping mid corner (off camber part) the surface was bumpy (F1 cars) and the bike seemed to drift outwards and I'm not sure whether or not I was on the wrong line, so on the wrong (bumpy) bit of the track to try and get on the gas earlier, I tried several differing lines trying to square the corner off a bit, and making the exit come to me, but nothing seem to help the feel.

[Gizmo]

Originally posted by JPM
Right just spoke to K-Tech, very nice guys just to see if they can shed some light on things, they gave me some base settings for the front end

28mm static sag
Comp - 6 to 8 clicks out
Rebound - 14 clicks out

Think I'll take a note of what I have got and give it a go. A few questions though static sag? I'm guessing I need to lift the front of the bike off the ground measure the length of fork leg exposed, drop again and re-measure? and then adjust via preload (blue nut - technical eh?)

Gizmo, I kind of got half of what you said, then it went blah, blah, blah As for a description well tip in 2nd gear probably doing 60-70mph knee down, and the front feels like it's skipping mid corner (off camber part) the surface was bumpy (F1 cars) and the bike seemed to drift outwards and I'm not sure whether or not I was on the wrong line, so on the wrong (bumpy) bit of the track to try and get on the gas earlier, I tried several differing lines trying to square the corner off a bit, and making the exit come to me, but nothing seem to help the feel.

k tech are top guys, they helped me out last year with an Sp2 and I jsut got a new sprign from them 2 weeks ago.

if you are knee down you are well passed the point of tip in and geometry has less of an effect, i'd say its probably 2 things, forks too soft so check your preload, too much rebound, count how many clicks you back it off when you go to the K tech suggestion.

preload is measured by extending the fork and measuring distance from fork seal to bottom edge of fork leg it'll be about 120mm on ohlins, sit on bike bounce/settle suspension and measure again, to set, wind blue adjustors right out ( count turns so you can compare) and then set it so its has 28mm of sag ie 92mm between seal and bottom of leg ( for road use i run more than that). see how far your tie wrap goes ( check mine out this w/e, its a red fork seal slid onto the slider, looks much neater than a tie wrap ) when riding, it should get to the bottom occasionally but not all the time.