matt_claydon
|
| posted on 5/8/08 at 09:23 AM |
|
|
Excessive body roll
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
|
| posted on 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
|
| posted on 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
|
| posted on 5/8/08 at 09:40 AM |
|
|
As above!!!
You could easily Retro Fit a forward facing roll bar like mine below...
.JPG)
|
|
|
worX
|
| posted on 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
|
| posted on 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
|
| posted on 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
|
| posted on 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
|
| posted on 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
|
| posted on 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]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
pbura
|
| posted on 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.
Pete
|
|
|
britishtrident
|
| posted on 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.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
Syd Bridge
|
| posted on 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
|
| posted on 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
|
| posted on 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
|
| posted on 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
|
| posted on 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
|
| posted on 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
|
| posted on 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
|
| posted on 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.
Pete
|
|
|
