Hi all,

I recently did a track day, apart from engine issues one of the problems we found was body roll-
looking at photos afterwards we seem to have a lot of body roll much more so than the various caterhams westfields etc...
even had some wear on the tyre wall from the wheel arch! for info we had the shocks set to full stiff
anyone experienced this? im almost thinking we will need to fit stiffer springs, currently have the ones supplied by tiger

thanks

les

You have to see the problem as two different and separate issues, the body contacting tyres indicates the bump stops need lengthened by add extra rubbers, the excessive roll indicates you need extra roll stiffness either by increasing spring stiffness or the use of a anti-roll bar(s).

First step is to find out the spring rates and free lengths that are currently fitted and decide if the car handling balance is under-steer or over-steer or is neutral

If you haven't already, check your tyre wear for camber. It could be that you need more camber, which may also cure the issue of your arch rubbing. If the camber is fine, remove some of the fibreglass on the return lip of the wheel arch.

We had a similar issue with our Indy a few years ago with too much body roll on the rear. We played around with front and rear spring rates and eventually found a combination that prevented excessive roll.

Also, what springs do you have?

Phil

One other thing having the shocks set to too stiff is not a good idea, you need to a dampers set quite soft or you are likely to suffer an unplanned trip into the barrier.

If you set the dampers too stiff the wheel will skip over undulations in the road causing sudden loss of grip ie the car will feel great but without warning spin out in the blink of an eye.

Oh the joys of Tiger Avon handling......

I had exactly the same problem with my C20XE Avon.


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The cars actually handle ok to a degree but on track with std Gaz setup and pushed hard they roll alot and feel a little unsettled.

Mark+Colin@MAC#1(01142511016) spent quite a bit of time on my geometry last year which made a fair bit of difference without compromising driveabilty on the road.

That said it didnt solve the body roll which is in question here.....

Ive posted here,there and everywhere on different forums asking about spring changes to our setup.

Ive had a few answers on the subject and my findings are as follows:

Car needs an anti-roll bar fitting(mine is in dock now being fitted, will report back next week)
Other Tiger racing series guys also use one.

Spring changes help but will unsettle it on the road if you go too far.
Again chap in Tiger series uses 400lbs up front and something daft on the rear too but apparently it hanldes great in the dry but like tea trolley in the wet.

Tiger tell me that you need to increase at least 40lbs per spring to actually feel the difference so ive had 4 made, 320lbs up front and 250lbs to the rear(which is where it rolls most,see photo). These arent fitted yet but am holding out till i see the effect of the roll bar first.

I`m glad its not just me.....

As said above really. Its the spring weight you need to change, the damping stiffness essentially affects how quick the car will roll not the amount of weight needed before it will start to roll. Anti roll bar will certainly help.

Your car is a common car and engine I would guess so you should have a common weight overall. This means you can use other car setups as a guide but not gospal. Your trying to get an improvment not the perfect set up at the moment.

Good luck and feed back the results. This is a road that I will be going down shortly. I think I will just take my car to RTR though and be lazy!!

Biz

Hi

The problem with the Tiger front end is that the damper is in a position where a 400 Ish Lb spring may sound high but it is only equivalent to something like a 300Lb fitted on a Westfield for instance. If your dampers are running full hard then they are clearly either not set right or not valved for the application. Either way the damper and spring package need further investigation before you spend money on a Anti roll bar.

The fitment of a anti roll bar is not necessarily there to eliminate the body roll but is there to act a a fine adjustment tool to give adjustable balance to the car. Hence the reason why many end up fitting bars that are way to stiff for the application and are still way out on the spring and damper package.

Cheers Matt

I know how you feel.....





Martini High Res

Sorry for the non 7 hijack :-)

Interesting Matt......

By the sounds of it you`ve seen a few Avons then?

What spring poundage have you used to good effect previously then?

[Edited on 19/5/11 by laptoprob]

One thing car builders are not always aware is the relationship between roll stiffness and a handling balance, if you stiffen the rear without altering the front stiffness by the same percentage change you transfer grip from the rear to the front ---- ie the handling balance tends more toward oversteer.

Keeping it at its simplest level when making a change in roll stiffness at only one end of the car:
Stiffen front spring rate ----> Understeer
Stiffen front ant-roll bar ----> Understeer
Soften rear springs ----> Understeer
Soften rear anti-roll bar ----> Understeer



Stiffen rear spring rate ----> Oversteer
Stiffen rear anti-roll bar ----> Oversteer
Soften front spring rate ----> Oversteer
Soften front anti-roll bar ----> Oversteer

That's the general principle but keep in mind other factors such as roll steer and camber come into play that means these rules of thumb can sometimes get turned on their head.

Altering the damper stiffness is used to alter the car balance in transient changes in steering input.

After speaking with Matt at Procomp i think you need to give him a call.

He certainly knows his stuff and has shed alot of light on my handling woes

Thanks again Matt

Thanks for the replies guys,

Handling is not an issue-very neutral through fast corners, and fully adjustable on the throttle,
Admittedly a bit too much understeer into slow corners, then good fun oversteer on the power from
Apex to exit. Actually responded to changes in tyre pressure and shock changes too,
I used to race fford at a very amateur level many years ago, so I am quite used to stiff
Cars which bite when you get to the limit, and the Avon is really pretty easy to drive at and over the limit,

As I say I was really surprised when I saw the pictures, which doesn't say much for my test driver ability!!!

Some great advice which will give me a starting point, I don't know what the spring rates are at the moment,
They are the standard springs supplied with the car by tiger, it sits down quite a lot when you get in so must be fairly
Soft?

The springs you have are 250lbs at the front and 180lbs at the back.

ok, so probably a too soft from what people are saying- trying to attach a picture but struggling!

les

lsdweb- brilliant!! i dont quite have that much roll, but not far off!!!

les

If you want to go stiffer on the springs then call Tony at YORKSHIRE SPRINGS in Rotherham as he is the one who manufactures them for Tiger

Just tell him what poundage and he`ll make `em for ya.

Just to report back.....

I had the antiroll bar fitted last week which was off an HPC Caterham but bent to shape my Avon.

It made a huge difference. I went to Bylton yesterday and had a fantastic day with the Mac#1 boys.

The handling has become an absolute pleasure, it kept on the toes of all the bike engined stuff without drama.

It balanced nicely on the throttle between under+oversteer. I knew exactly what it was doing all the time and roll has been dramatically reduced.

Blyon is a very flat course so Cadwell may be a different story but upto now the car is sorted

Great info thanks, il give them a call-what spring rates did you end up using? And if I can ask, how much?!
Did you have to bin the gaz shocks?

On a side note, I did an experience day years ago at blyton park- Leicestershire?
Was it a test day or track day? I would love to do a track day there, quite a nice circuit as I remember.

I didnt change the springs in the end.

I left it with the same Gaz setup as yours!

The only thing fitted was the roll bar....major difference




Blyton has had a revamp by the new owners.

It boasts a great circuit and new tarmac now and costs very little.


http://www.blytonpark.co.uk/

Are you local?

Rob.

[Edited on 31/5/11 by laptoprob]

I`m selling my springs if you fancy changing yours?


HAVE A LOOK HERE

hi,

I guess I would be looking for stiffer ones- or maybee go the same route as you and get anti roll bars.

what kind of shock settings and tyre pressures do you find best?

les

Its changed a little now with the roll bar fitted but i ran 8 clicks up front(left>right) and 6 on the back but i have reduced them to 5 and 3 now.

Rob,

Do you have any pictures / details of were you got the bar from? This is something I would like to do on my car.

Did you only do the front or rear as well?

Cheers,
James

Have been following your arb project with interest.
Do you have some approx dimensions please of the arb, especially steel size & bar or tube?
Thanks

Supercat/Emidas.....

it was fitted by an engineer who is very much into Caterhams locally. Its actually off a Caterham HPE 1996 which he bent into shape my upper wishbones then mad two pockets to sit it in which were welded to the wishbones. I dare say he would attempt another but will have to ask first.

Its gone into MAC#1 for brake upgrades to be fitted this weekend so i cant send pics or dimms until Monday but will do so then for you both,

Meanwhile you may want to talk to this chap LINKY as he was the gut i spoke to at Stoneleigh about the whole project but unfortunately was too far away from me. He was very helpful and sent over some pdf`s to do some measuring etc so he could quote for the ideal bar.

I will talk with my local guy this weekend to see if he wants the work.



[Edited on 4/6/11 by laptoprob]

we fitted ARB's to the front and rear of our Avon and it keeps the car nice and flat. We have just fitted the next spring rate up (25lb heavier each) and will be testing them at cadwell on tuesday, but testing so far feels very good.

We tried to get Northampton Motorsport to fit ARBs this week, but theirs didn't really suit.

Can anybody with them fitted please supply pics of where to put them and how to mount them, along with where to get drop links and the bar itself?

Thanks
Ed