NS Dev
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| posted on 17/8/08 at 10:02 PM |
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7 Handling on track
Put this one here as not really sure where it fits and everybody looks at this bit!!
As many on here know, I mechanic for a Caterham Superlight Duratec running for the second year in the superlight challenge.
Just thought I'd get some opinions on here on a handling issue, more out of curiosity than anything else!
We suffer badly with slow corner understeer in the caterham, and nothing we do seems to stop it doing it.
The car is very quick (top 3) though all the fast sectors of most circuits, but in the "twiddly bits" we lose out a lot, to a magic few
that seem to be able to be rapid in these areas.
I've done all the obvious stuff (minimum front spring, soft front bar, toe out on front, 2.5 deg neg camber on front etc etc) but to be honest
NO setup has ever improved this basic problem.
Anybody with track experience know any tricks to getting a 7 turned in on slower corners??
My "current thought", which is easy for me to say but no doubt either being done or impossible for the driver to do, is to plan late
braking so that brake release EXACTLY co-incides with a VERY aggressive turn-in, hopefully keeping the back end unloaded so it can swing, the front
loaded so it can turn, but not over brake loaded .....?????
any thoughts??
I am stuck for ideas and so is the driver, he blames the car and himself, we can't do much more with the car and blame him!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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worX
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| posted on 17/8/08 at 10:07 PM |
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PMSL!
Was reading your post on my phone, so only snippets of info before scrolling down, and all I could think to say is to tell him to strap on a pair and
brake until the point of turn-in, just like you suggested!!! 
What size tyres are you running front/rear?
Steve
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NS Dev
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| posted on 17/8/08 at 10:13 PM |
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you know I can't bloody remember now!!
I think 195 front and 235 rear, off the top of my head.
Its set in the regs anyway, control Avon tyres and control wheels.
The avons are pretty horrible things that seem to gain and lose grip several times through their heat and cooling cycles.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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worX
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| posted on 17/8/08 at 10:19 PM |
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Well they seem like the correct front to rear ratio for a caterham.
What about changing the brake bias to the rear slightly, that way he could trail the brakes slightly into the slower corners and the front should
squat rather than dive?
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NS Dev
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| posted on 17/8/08 at 10:35 PM |
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fixed bias, single master cyl, no bias bar, just rear bias valve but that's no good!
not allowed to fit bias bar!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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Volvorsport
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| posted on 17/8/08 at 10:40 PM |
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pump the tyres up to 30 - 40 psi , if its still the same , it cant be the spring rate .
ive got no problem turning in with mine , but i think ive still got to hard a spring on the back .
www.dbsmotorsport.co.uk
getting dirty under a bus
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worX
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| posted on 17/8/08 at 11:09 PM |
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From what you are describing I'd say try a touch more toe out, but assuming you've tried a few diff settings, but because you are running
195's on the front, have you ever tried it with a touch of toe in?
Also, ever tried it with front ARB disconnected?
Steve
ETA - just a thought, but is it more prominent round a specific handed corner, ie a left or right hander?
[Edited on 17/8/08 by worX]
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RK
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| posted on 18/8/08 at 12:25 AM |
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Is the driver left foot braking? Works in a Honda Civic; should work on a Caterham.
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Aico
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| posted on 18/8/08 at 06:50 AM |
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An agressive LSD gives slow corner understeer. What diff are you using?
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Richard Quinn
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| posted on 18/8/08 at 08:19 AM |
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As per Worx, just try disconnecting the front ARB on one side and see if that makes any difference.
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novacaine
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| posted on 18/8/08 at 08:38 AM |
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quote:
Originally posted by RK
Is the driver left foot braking? Works in a Honda Civic; should work on a Caterham.
The reason lfb works in reducing understeer/inducing oversteer in a honda civic is that it is front wheel drive
you can lfb in a rear drive car but it works in the opposite way, reduce oversteer/induce understeer
i would second the suggestion of playing about with the toe settings
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britishtrident
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| posted on 18/8/08 at 11:19 AM |
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Ideas
(1) Gets some good head on pictures of the car entering a hairpin and examine them to se what how the car is cornering in terms of roll angle,
wheel camber, steering angle ----.
(2) If you can find some where such as private car park you can turn tight circles measure the tyre temps accross the tread of the fronts.
(3) Front dampers --- could they be valved to stiffly for the car's weight ?
[Edited on 18/8/08 by britishtrident]
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pbura
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| posted on 18/8/08 at 12:47 PM |
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Sounds like an Ackermann issue to me, and a quick Google showed that some Caterham owners like a little toe out to compensate:
http://search.yahoo.com/search?p=caterham+%22toe+out%22&fr=yfp-t-501&toggle=1&cop=mss&ei=UTF-8
It would be interesting to plug into a suspension proggie to see what you have. Here's an idea: Adjust bump steer to induce toe out under
heavy braking.
Pete
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NS Dev
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| posted on 18/8/08 at 09:59 PM |
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toe out - already done
ackermann - all the cars are the same on the grid
diff - good question, but I think its "sealed" but......hmmmmm interesting one!
toe in - mmmm, not tried it yet!
no ARB on front......I KEEP bloody telling the driver to test back to back with no front OR rear bars on but he won't bloody listen!!!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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Richard Quinn
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| posted on 19/8/08 at 04:17 PM |
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quote:
Originally posted by NS Dev
ackermann - all the cars are the same on the grid
But not all drivers have the same size balls when in comes to turning in.
quote:
no ARB on front......I KEEP bloody telling the driver to test back to back with no front OR rear bars on but he won't bloody listen!!!
Back to back testing is the only way forward with this type of issue. Change one thing at a time (including the driver if need be!)
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NS Dev
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| posted on 19/8/08 at 06:39 PM |
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you're right Richard, only the trouble with our driver is that he is TOO ballsy!!!
He is super quick on the fast stuff, where others take it a bit safer, but we all think he is just not patient enough on the slower bits (his corner
entry speeds are ALWAYS quicker than everybody elses, on both fast and slow corners)
Lets not be silly though, he is NOT a crap driver, being an ex formula ford champion!!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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greggors84
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| posted on 19/8/08 at 07:58 PM |
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How long has he been driving the Caterham?
Maybe he is simply trying to drive it too quickly into the slower corners and the understeer means he cant get it out quick enough.
Trying to suggest to an ex formula ford champion that he is driving the car the wrong way is going to be nigh on impossible of course!
All of the above is based on the assumption he is relatively new to the car and is still trying to drive is like a mid engined single seater. Of
course he could have been driving caterhams for years and might have just come across this problem with a new car this season.
Chris
The Magnificent 7!
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Richard Quinn
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| posted on 19/8/08 at 09:30 PM |
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I wasn't questioning his ability as a driver, more his ability to listen and accept that finding a way forward will require his involvement.
Some people have a natural ability and when things don't go right they automatically assume that it is the car. The only way, as I said earlier,
is to do back to back testing. You need an open pit lane track day and make individual changes looking for feedback after each change. Massage his ego
a little and emphasize how important his accurate feedback is. Have you driven the car and experienced the understeer?
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NS Dev
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| posted on 19/8/08 at 10:20 PM |
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greggors and richard, both hit the nail on the head I think!!
I find it very hard to "question" what the car is doing as he's a better driver than me.
Rich, yep I have experienced the understeer, but it was in streaming wet conditions so no great surprise!!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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RK
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| posted on 19/8/08 at 10:52 PM |
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I disagree with Novacaine. Our ice racing instructor this last winter, an experienced 911 driver, and past winner of the Targa Newfoundland, found
that it works as an inducer of oversteer in his car. Last time I checked, it was RWD.
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Richard Quinn
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| posted on 20/8/08 at 01:56 AM |
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Never known anyone who needed to induce oversteer in a 911!
It is more commonly used in fwd, primarily in rallying with a full rear bias, to unload the rear during cornering. The car is then balanced on brake
and throttle.
Left foot braking is used in rwd mainly to reduce the time between brake/throttle application and can lead to a different type of oversteer to that
normally experienced under a trailing throttle.
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RK
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| posted on 20/8/08 at 02:13 AM |
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In any case, if the driver needs to do this or something else to get the car through the corner, it probably needs fundamental setup changes to make
it more balanced, thus making my comments irrelevant!!
Again, in a Honda and an A4 Avant, the LFB technique unloads the back incredibly well on ice and on pavement. The Pendulum Turn (Scandanavian Flick)
is harder to do, but works just as effectively, at least on ice.
[Edited on 20/8/08 by RK]
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