Wheel Waving

[Gerry H]

Having done the MLR sprint at North Pickenham I and a number of others were perplexed as to why I was managing to get a faster time around the twisty track with our illustrious leader firmly ensconced in the pax seat. This, particularly after he, himself, declared, upon placing his sylthe-like 19 stone frame into the car "You ought to strip all this surplus weight out. You'll go much faster"

Having discussed the whys and wherefores I began to wonder whether it may be an inside front wheel lifting. Although 4 wheel drive, the car has an open front diff which will allow the inside wheel to spin and lose drive on the front. Stu's weight was keeping the nearside wheel in contact on the left turns, of which there were many

Anyway, all this conjecture has been confirmed by the pix kindly linked by Rob Callow here:



http://www.phpbbserver.com/clubgtr/view ... um=clubgtr

For those who don't know it's the slightly battered, white Scooby towards the bottom of the page. The pic is taken at the left hander of the chicane (sorry don't know the names of corners) before the pit entrance. If you zoom in to the nearside, front wheel, it's waving in the air. I thought the kerbing felt less vibratory than I remembered :roll: In one respect, I quite like it as it reminds me of those fantastic pix of Jackie Stewart, Graham Hill and Jim Clarke, racing against each other in Mk I Lotus Cortinas, in the days when Formula 1 drivers were less Prima Donna like and would race anything and sometimes causing their tragic demise in the process.

Anyway, I digress. The question I would like to ask of you suspension gurus is Why? and What do I do about it? I know as much about suspension as I do needle point, whatever that is.

I do have, sitting in it's box, a LSD front diff, which I found on ebay. Unfortunately the moronic mechanic who removed it for the seller left it sitting around, uncovered in the workshop and then, I guess, proceded to grind a considerable amount of mild steel in it's direction, covering it in a liberal layer of steel dust that can't just be washed off as there's some magnetic attraction going on. :x

Any suggestions? Is the suspension set too hard? I have KW Variant 3s set pretty much to mid wat, as they came out of the box, Whiteline ARBs set to max on the rear and soft on the front.

TIA

[Stuart]

I think that the roll bar stiffness may be a factor, although your line and weight distribution of the car may be bigger ones. I didn't get a chance to follow you at Snetterton but it was always the transitions that caused problems at Pickenham, and Russells chicane is essentially the same thing but a lot quicker.

I'm not sure the new diff would make a lot of difference as the wheel is not spinning up (it's not touching anything ) I would be interested in playing with the various lines into and through chicanes like this first and only play around with set up if and when that doesn't solve the lifting. Your car is very well balanced (in my very limited knowledge) overall, great in fast sweepers, stable under braking and I think more suspension tweakery may spoil these strongpoints.

Get testing and try and be as objective as possible. I'm sure someone can lend you a driftbox for measuring improvements :thumb:

[duncan]

is it just me or does that picture look surreal ?

I reckon the rear ARB is too stiff for it Gerry or the rebound on the KW's needs adjusting - John Felstead would know why and what to do about it I think.

[Stuart]

is it just me or does that picture look surreal ?
.

The cones/markers are photoshopped

[Mr Fletcher]

i'm not a suspension expert but i think i would have a picture without that kerbs influence before i went to far

as i had a rear wheel air born in a picture(sti 03 std) , stu will know more about the kerbs design as it felt bumpy.

just an observation thats all , good luck with the improvements.

jason

[Mr Fletcher]

is it possible to have the corner weights checked :?:

jason

[sdminus]

Its hard to say from a pic like this. I would say that you have pulled right across the kerb. not exaclty an early apex by the projectary of the car but still too deep.

Again from the pic i would sugest that you entry to the 1st part of the comprimise ess is too fast and has thrown you too deep into the 2nd part. I would sugest looking at gary (apt) pic.

A ess bend is an art form. You should accererate right through. Take take the 1st turn as a late apex to set up the second ( more important part)

Scott

p.s if we know the exact radious and the corner capacity of your car we can work out a avg speed

[ESL]

I'm with Jason here Gerry, the ribs on the inside corner of Russell are fairly substantial. The inside will be very lightly loaded and maybe you are being slightly jacked up at the rear on a raised section? Is this the only pic you have seen exhibiting this behaviour? If so , it might be dangerous to read too deeply into it as your car is a class winner.

I have never seen it do anything like that at Pickenham or at any of the JISC sprints. When you took me round Barkston I thought the car felt very nicely balanced.

I thought you had set your fastest time at MLR with Stu out of the car?

[Gerry H]

Thank you for all the very valuable comments. They're very helpful.

Maybe my best course of action is to consolidate what I have. Try and step back from it and tackle the problem (?) methodically. I'm just not sure how to approach it though. Maybe I ought to have a read up on the principles first and then, with some knowledge, tackle it.

Andy: My fastest time was without Stu by a couple of tenths iirc, eventually, but I also had the centre diff fully locked so the back was still driving even if the front was free to spin, as I understand it.

[ESL]

I'm still worried there may not actually be a problem. Is this the only photo with the front lifting? Theres 1000s of photos of your car on line from all the events you do!