Axel Tramp - Help needed - AE86

[JoJo]

Well, I've tried, but haven't been able to come to a solution.

My problem is Severe axel tramp in my AE86.

Where do I start.....
My suspension setup is:
GReddy coilover setup (front coilovers and rear adjustable spring perches and fully adjustable GReddy Shocks, stroke and damper), modified R31 rear end..

Now, For the last year, I have had some random positive offset wheels on the car, which were on the car when I installed my GReddy coilover kit. Never had ANY problem with axel tramp.

Recently, I have got some WORK EQUIP 01 rims, 15x8 -13 offset. When I put them on, I adjusted the rear spring perch heights and what I believe is the 'stroke' of the shocks, so the height looked 'JDM' (neg offset and low). Ever since then, I have had severe axel tramp problems.

The car drifts/slides without any problem, but if I try to spin the wheels from standing still, the axel tramp is totally fucked! Why do I need to spin the wheels from standing still you ask? Well I race in the Canberra hillclimb competition, and need to do a burnout to warm up my slicks for the 1 lap circuit.....

I have tried adjusting the spring heights and shock stroke (?) to fix the problem, but it is making no differance. Because of the variables, Iam not really asking for an off the shelf answer, but I am more asking about the causes of axel tramp with an AE86.

If someone here has the time to explain the causes of axel tramp, it might enable me to get my head around the physics of this problem, helping me with an adjustment solution. I am quite frustrated that it was once all ok with this suspension setup, but now cant return it to how it was. All advice is greatly appreciated....

Regards,
JoJo

[litldv8]

axle tramp is suspension wind up (caused by tyre grip) before the weight of the suspension overpowers the grip on the road.
it is usually prevailent in leaf sprung cars
i think you will find that you have adjusted the valve in the bottom of the shock for rebound not "stroke" by which i think you mean height and have made them harder
try adjusting the shock back to a softer setting
what are the bushes in the top and bottom of it like?
and the trailing arms like?
just my 2c
neil

[allencr]

Your motor mounts can also absorb energy & wind up, then release it just like a spring.

[assassin10000]

Stock 4-links? Bushings? Rod ends?

Got traction brackets?

Andrew

[JoJo]

yeah, stock 4 links, standard bushings (only 1 year old)

No traction bracks

Rod ends?

[JoJo]

I cant see how the bushings would be the problem. As I said, I didn't have a problem with this setup, untill I lowered it for the WORK wheels. Now, no matter what I try, I cant get it back to how it was......

[DX20VT]

If you have adjusted the height of the car then the things you have affected are the position of the shock valve in the ride height position and probably the pinion diff angle.
Does it have adjustable arms on the top or bottom of the diff housing? May need to shorten/lengthen them to get the rear to grip properly, I played with them on my car and it makes a noticable difference.
But it is most probably the valving in the shocks, as the stiffness/softness of the actual shock usually varies through it's travel and by lowering it you now have it in a different part of it's travel.

[JoJo]

Thanks mate, good helpful points there.

Had another go at it and it it much better now. I had to lengthen the shock, as I had it too short, affecting the diff pinion angle Iam guessing. There is not much travel in the shocks now though, only about 2-3 inches, but the springs are 6kg spring rate, so there is not much movement in the suspension anyway. I now realise how I went wrong, wasn't focused on the diff angle....

Here is a pic to explain...




Thanks to everyone for their help.....

[JoJo]

double post

[LeeRoy]

You said you changed the wheels - if they're wider it will also affect the axle tramp.

[JoJo]

Really? That might explain why there is still slight axel tramp. The wheels from when there wasn't a problem were 15x7 +6 offset. The WORK EQUIP 01's on there now are 15x8 -13offset. Added heaps more rear track to the car. I will be using the old wheels tomorrow at the Canberra Hillclimb with semi-slicks on them. I will know tomorrow where I am at.....

[Willofan]

If you have adjusted the height of the car then the things you have affected are the position of the shock valve in the ride height position and probably the pinion diff angle.
Does it have adjustable arms on the top or bottom of the diff housing? May need to shorten/lengthen them to get the rear to grip properly, I played with them on my car and it makes a noticable difference.
But it is most probably the valving in the shocks, as the stiffness/softness of the actual shock usually varies through it's travel and by lowering it you now have it in a different part of it's travel.

I know you have acknowledged pinion angle by DX20VT, as this would be the most likely cause. lowering your car changes the pinion angle to point down. After your hillclib I would suggest you buy adjustable upper links and get the diff to point up inline with the driveshaft.

If you then get binding when cornering, I would suggest going to a 3 link and or bringing the upper arms inboard and making them longer to equal the length of the lowers.

Good luck tomorrow

[LeeRoy]

Tyre width will definately have an impact - more tyre means more force the car can put on the driveline before breaking traction. I would agree that the lower suspension settings will probably have an impact also.

Axle tramp is basically the rear suspension being wound up and then let go, like a spring, which gives you all the hopping.

The ability for the diff to rotate will heavily depend on the position of the arms (the cars height) and also the bushes.

[cri_ag]

my ae86 axle tramped hard from a standing start, fix was adjustable lower rear arms to alter the pinion angle of the diff, linden made them, problem solved.

[JoJo]

All fixed..... Had the hillclimb today. Absolutly no axel tramp with starting burnouts. =Happy..... Came equal first in my class........