JimSpencer
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| posted on 12/6/07 at 09:09 PM |
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Understeer - again... Help needed
Ok have a major understeer problem..
Running a Live axle sylva striker, early one with outboard shock front end.
Rear Axle is 5 linked with Panhard rod.
So nothing clever, no anti roll bars.
Quaife ATB diff
Scudo Stunner tyres, 195/45/15
(Have to run on MSA list 1A rubber)
About 3degree camber
Just seem unable to dial an inherent undeersteer out of the car, tried all sorts of combiantions of springs to little effect - or worse litterally
little effect when dramatically changing things..
Did a test day to set the car up, fiddled away and got to the following set up:-
Rear 175 lb/in shocks @ 16 clicks out of 20
Front 275lb/in shocks @ 15 clicks out of 20
Car had a reasonable balance to it, working ok.
Touched nothing.
Did a track day prior to a 2 day sprint, only ran 3 (out of 6) sessions as car felt good, though perhaps a hint of understeer coming back by the end
of the day - put down to tyres getting hot.
Did the 2 day sprint.
Started with a bit of undeersteer, ended with near terminal undeersteer.
Tried different springs / camber / tyre pressures nothing made any difference what-so-ever (i.e. front springs to 350lb/in etc..)
About the only thing we didn't do - as the car has different pcd front to back - is swap tyres front to rear. Wondered if the inherently
different wear characteristics of a live axle versus independent front end could effect tyres to such a large degree?
Is this possible, can the wear pattern effect the handling to such a degree that large setup changes arn't noticable?
Or has anybody got any similar experiences they would like to share?
And can somebody recommend a guru in the North West who can do setup work on Seven's for a resonable fee, as desperation is now setting in as
just can't make the thing handle properly, its making the events so frustrating it's untrue..
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Howlor
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| posted on 12/6/07 at 09:16 PM |
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How old are the shocks and is there a chance they are going off with use. Aeration in the fluid within them?
Just a thought.
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Howlor
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| posted on 12/6/07 at 09:18 PM |
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Also what about fuel level? Wheres the tank?
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higgsti
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| posted on 12/6/07 at 09:25 PM |
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http://www.rogerkrausracing.com/TechSheets/overunder.shtml
might help
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russbost
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| posted on 12/6/07 at 09:33 PM |
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Make the rear stiffer or front softer (shock adjustment) you may need to be quite drastic in the changes, also narrowing front track or widening rear
will have similar effects
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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JimSpencer
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| posted on 12/6/07 at 10:40 PM |
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Hi
Shocks are failry new AVO's
Tanks at the rear (mini Van..) but car only runs with about 2 gallons Max on the track
Russbost
Re shocks (i.e damping settings?) stiffer / softer I'm being told this just effects transition, and I can ideed effect initial turn in by
adjusting this. However steady state corning seems to be uneffected - is this what you mean or should I be seeing a change hear too?
Re Track width changes, can do this as running 6mm spacers, what way round changes what?
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alister667
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| posted on 13/6/07 at 01:01 AM |
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I'm not sure how a Quaife ATB reacts but several friends have noticed a big increase in understeer after fitting an LSD (mainly plate) - once
it loosens up (repeated thrashing) it seems to improve.
Is there any way of adjusting the Quaife LSD?
Cheers
Ali
http://members.lycos.co.uk/alister667/
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nitram38
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| posted on 13/6/07 at 04:30 AM |
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Your camber setting also seems a bit high. 0.5 degrees per side on a car with little roll is normal, but if you are using 3 degrees of camber to make
the car work, then fit a front anti-roll bar and return it to 0.5 degrees each side.
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nre
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| posted on 13/6/07 at 07:21 AM |
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You are right in that changing the number of clicks on the shocks will only affect transients, not steady state cornering. To change steady state
balance you need to change springs (the 350 fronts you mention will give more understeer, you need to go softer at the front or stiffer at the
rear) or fit anti roll bars.
The fact that the car seems to change from one run to the next is odd though, it suggests that there is something else going on! Is the car the same
when turning left and right?
There was a thread on the Sylva chat list within the last week or so on Striker spring rates, worth having a read... your base setup doesn't
sound a million miles out so strange you are having such problems...
Sylva Mojo Zetec on GSXR750 throttle bodies...
www.mymojo.co.uk - Facebook feed
JPSC Forum - A dedicated forum for discussion on all things relating to Jeremy Phillips designed cars
Including the Star, Leader, Striker, Phoenix, Fury, Jester, Stylus, Mojo, Riot, J15 & Vectis
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russbost
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| posted on 13/6/07 at 07:24 AM |
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Jim
I have always understood that the shock changes should affect cornering all through turn in, once turned in understeer really shouldn't be a
problem - unless perhaps the LSD is affecting things. If it is the LSD a change in driving style may help, flick the car in (as you would with a Kart)
then apply a welly bootful of throttle to stick the back end out (the LSD should break both wheels loose) & then control on the throttle.
The track changes work that the wider & therefore more stable the front end the more it will understeer, hence you need to widen the rear &
narrow the front.
I would disagree with Martin about an anti-roll bar on the front, I think that would increase understeer & camber changes of the order talked
about wouldn't have much effect.HTH
Obviously all the above are generalisations & therefore may behave differently from car to car.
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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Phil.J
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| posted on 13/6/07 at 07:29 AM |
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You could also try lowering the front ride height, and try running about 1/16'' toe out at the front.
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Nick Skidmore
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| posted on 13/6/07 at 07:35 AM |
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Increasing the roll stiffness at the rear will dial out understeer.
With a soft rear end the weight transfers to the rear by rolling in cornering and takes away mechanical grip from the now light front end, a rear ARB
will resist this but still allow relatively soft sprngs at the rear for traction.
It is also possible to overheat the front tyres with no rear ARB for other reasons that escape me at the mo.
[Edited on 13/6/07 by Nick Skidmore]
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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minitici
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| posted on 13/6/07 at 08:12 AM |
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Have you checked to see if your steering rack is still secured to the chassis?
I had what felt like understeer on a GTM Coupe - it turned out that the steering rack clamps were loose and the rack was sliding as the steering loads
increased mid-corner
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jambojeef
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| posted on 13/6/07 at 08:17 AM |
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Tyre pressures?
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BenB
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| posted on 13/6/07 at 10:07 AM |
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Why does altering the ride height effect the understeer or oversteer?
I know it does, just can't work out why!!!!
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Steve Morten
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| posted on 13/6/07 at 11:59 AM |
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I've just sold one of Jeremy Phillips demo strikers that he used to race after running it for 13 years. I used it for Autotesting so getting rid
of all understeer was essential.
So it might help if I list my settings, 'll leave it up to you to come to your own conclusion, just to say turn was superb!
Caster 5.5 degrees positive,
Camber 2.5 degrees negitive,
front ride hieght(at front corner of chassis) 5 1/4 inch,
rear ride hieght (at rear corner of chassis) 4 inch,
Front springs 140 lbs 8 inch free length,
Rear springs 100 lbs 8 inch free length
tracking a little toe out helps initial turn in.
Shocks on softest setting,
tyre pressure 18-20 psi.
When I bought the car it had 180 lb front spring and 140 rears and thats how Jeremy presumably raced it.
Caster is important to turn in so don't dismiss it.
Hope that all helps.
Stephen
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andyharding
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| posted on 13/6/07 at 12:07 PM |
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Try dropping your tyre pressure to 15psi.
My car just didn't feel "right" running 20psi. Dropped to 15psi and huge!!! impreovement.
Are you a Mac user or a retard?
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steve lansley
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| posted on 13/6/07 at 11:14 PM |
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Strikers don't handle. Get an LA
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mawmaw
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| posted on 14/6/07 at 08:56 PM |
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handling
er yes they do(handle - strikers). i found the greatest casue of unexpected understeer was either a few mph too much corner entry speed or a slippy
track. If this is a new problem, change nothing until you have tried it again on a different track. You will always have a compramise in handling.
your settings seem pretty close to spot on. it seems your shocks are set pretty hard. I had mine serviced recently made a huge difference, with those
spring rates i would expect to be in the first third of adjustment. good luck mark
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JimSpencer
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| posted on 15/6/07 at 08:12 AM |
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Thanks All
Plenty of fresh ideas to have a bash at, much appreciated
I'll come back after the next event with an update!
Jim
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