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Excessive body roll

matt_claydon - 5/8/08 at 09:23 AM

In this photo taken at an Autosolo I was doing on Sunday, you can clearly see the inside rear wheel clear of the ground. This would be acceptable in a FWD tintop but seems ridiculous for an Indy.

Hi res here

Any suggestions as to where my problem is? Stiffer springs, higher tyre pressure? I know you can get a front ARB for the Indy but I shouldn't need one to keep the wheels on the ground!

worX - 5/8/08 at 09:26 AM

Trouble with that is, I don't believe that is excessive body roll...

Jack the car up at the back with a jack on your Diff only and see if you can replicate the angles to see if the travel of your shocks is correct first of all?

Steve

matt_claydon - 5/8/08 at 09:40 AM

quote:
Originally posted by worX
Trouble with that is, I don't believe that is excessive body roll...

Jack the car up at the back with a jack on your Diff only and see if you can replicate the angles to see if the travel of your shocks is correct first of all?

Steve

How would I know if the travel was 'correct'?

I did consider that the suspension is not being allowed to droop sufficiently. Only fix for this would be longer shocks presumably?

worX - 5/8/08 at 09:40 AM

As above!!!

You could easily Retro Fit a forward facing roll bar like mine below...

worX - 5/8/08 at 09:42 AM

I don't know on your shocks/springs, but if you do as I said and then measure it and post your findings on here, then maybe someone would be in a position to do the same and give you a relative answer - I have sold my car else I would check mine for you, sorry...

quote:
Originally posted by matt_claydon

quote:
Originally posted by worX
Trouble with that is, I don't believe that is excessive body roll...

Jack the car up at the back with a jack on your Diff only and see if you can replicate the angles to see if the travel of your shocks is correct first of all?

Steve

How would I know if the travel was 'correct'?

I did consider that the suspension is not being allowed to droop sufficiently. Only fix for this would be longer shocks presumably?

Syd Bridge - 5/8/08 at 10:08 AM

From that pic, I'd say the problems are front and back.

The front inside tyre seems to be just about to lift as well.

So, front could do with softening some on the springs, and the rear definitely. That's IF, you have enough travel on the front and rear shocks in droop.......???

The rear outer tyre doesn't seem to have moved up much in bump, so it would appear that the springs are too stiff or the shocks a set too hard, or both. (Which is common to most 7 type cars.)

The rear inner doesn't seem to be dropping enough, hence the shock travel probably is insufficient.

Cheers,
Syd.

Howlor - 5/8/08 at 10:35 AM

Not being a suspension expert at all but would anti roll bars help that situation as well?

Dangle_kt - 5/8/08 at 10:51 AM

surely its not a question of droop? If the spring rates on the side that is being compressed where higher then the angle of the whole car would be less, therefore the inside wheels wouldn't be lifting.

I;ve seen a few cars with front inside wheels lifting on the power out the corners - does this show that ind suspension has flaws which a live axle does not??

matt_claydon - 5/8/08 at 11:13 AM

I can understand if the suspension drooped further then the wheel would not leave the ground. I also appreciate that most sevens are probably oversprung. But given that travel is restricted I would have though higher spring rates would be the solution meaning the outside suspension would compress less leaving the inner wheel on the ground?

[Edited on 5/8/08 by matt_claydon]

britishtrident - 5/8/08 at 11:20 AM

Is the car understeeing or oversteering in normal hard cornering ?

If it tends to oversteer stiffen the front in roll either by fitting a front anti roll bar or harders front springs.

[Edited on 5/8/08 by britishtrident]

pbura - 5/8/08 at 04:36 PM

From this picture and others on your website, it looks like your springing is firm enough.

If you like your present handling balance, consider anti-roll bars at both ends, say 10-12mm front/8mm rear. Have adjustable end links so you can tweak the balance.

britishtrident - 5/8/08 at 08:13 PM

quote:
Originally posted by pbura
From this picture and others on your website, it looks like your springing is firm enough.

If you like your present handling balance, consider anti-roll bars at both ends, say 10-12mm front/8mm rear. Have adjustable end links so you can tweak the balance.

Yes looking carefullt at the pictures in the archive I think the spring rates are probably hard enough, but looking at the disposition of the front wishbones when viewed from the front it looks like real root of the problem might be the front roll centre is too low ie at or near groud level. A very low front roll centre is similar in effect to making the front end soft in roll stiffness.

The roll centre is difficult to rectify without re-jigging the front upper wishbone mounting points to move them down, so the best solution is probably anti-roll bars or bars.

I would think just an ajustable front bar would be enough to start with 10 to 12mm if fitted without a rear bar.

Syd Bridge - 5/8/08 at 09:14 PM

I'll simplify what I said earlier.

The rear springs look too hard already, and the shocks appear to have insufficient travel.

As is found in most 7 type cars which are owner built.

Out of interest, do you know, and can you tell us, the open and closed lengths of the shocks fitted?

Cheers
Syd.

[Edited on 5/8/08 by Syd Bridge]

matt_claydon - 6/8/08 at 05:07 AM

That makes sense. I'm not in a position to measure the shocks now, but when I've got a bit of spare time I'll get onto it and report back with the results.

bob - 6/8/08 at 08:49 AM

Hi Matt

I'm thinking your shocks would be gazmatic the same as supplied to me,i will have to find my paperwork but i am pretty sure open length bolt centre to centre is 13" and closed 10"

matt_claydon - 6/8/08 at 04:39 PM

Pretty sure mine are Protech. Chassis is going to be identical though so figures for any working Indy shocks would be useful.

britishtrident - 6/8/08 at 07:43 PM

The working stroke of the dampers is limited by the space available which is not a lot when the bottom end is mounted on to the top wishbone.--- dampers with a longer stroke will be physcally longer even in the fully closed position.
So to accomodate the longer damper tube when closed either the upper mounting as to move up or the lower mounting moved down ---- not easy on an Indy chassis.

Without a damper catalogue to hand (it may vary with damper bodies available but I would guess to get 1.5" extra travel in droop will mean moving one of the damper mounts 0.75"

procomp - 6/8/08 at 09:08 PM

Hi

Looking at the photo's in your archive it is defo rolling to much ( obviously ). First if it dose have the correct 13" open length dampers fitted as it should as standard from MK then there is more than enough travel for bump and rebound. It really needs the ride height looking at and then the dampers position sorting so that it is allowing the correct droop / bump travel. This can be done by playing with the top eyes and swapping them for longer ones if necessary.

But still a case of why the roll. Have the dampers been setup at all and what spring rates are fitted. As others have said anti roll bars are a possibility but you should be getting better roll control than that without them.

Cheers Matt

matt_claydon - 7/8/08 at 06:50 PM

quote:
Originally posted by procomp
It really needs the ride height looking at and then the dampers position sorting so that it is allowing the correct droop / bump travel.

What sort of ride height should I be looking for? Or perhaps more importantly how much bump/droop travel should I be looking for from the neutral position?

quote:

But still a case of why the roll. Have the dampers been setup at all and what spring rates are fitted.

Can't remember where the dampers are set, but that shouldn't make any difference in extension/compression during steady-state cornering. Not sure on the spring rates, they are what was supplied by MK 4 years ago so I assume they should be correct or at least pretty close.

I'm not averse to fitting an ARB, but as you said, I should be able to get better performance without resorting to that.

pbura - 8/8/08 at 03:09 AM

When the car is at ride height (also presuming a representative payload), about 2/3 of the piston shaft should be showing, including the bump rubber.

I wouldn't be concerned about the lack of droop travel. Even if that wheel were on the ground, it would have very little traction as there would be no weight on it. You could adjust your corner weights to keep all four wheels on the ground, as when you have a passenger.

I think a lot of builders are missing out by not having anti-roll bars. Lotus had them from Day 1, in the Series I. Higher-end Sevens have them. IRS cars, e.g., Caterham CSR, generally need them front and rear due to having lower roll centers than solid axle cars. I recommended them to you because it looks like your springs are doing a good job of supporting the car and controlling pitch motions. Adding more spring will control roll, but may do so at the expense of ride quality or tire adhesion.