torque steer
 

Hoping to bounce some ideas off you guys. My mx5 based kit car is exhibiting what I can only describe as torque steer although obviously from the rear end.
When I get on the throttle the car steers to the right and when I lift off it steers to the left. Not by a huge amount but enough to upset things when your pushing hard.

First question is this normal ie. do I need to just learn to live with it?

As for my rear end setup I have mx5/miata hub carriers with stock rubber bush (Could the flexiness of the well used stock bush be causing this?).
Wish bones and rest of the suspension are specific to my car (bushes are poly and not worn though).
Driveshafts (halfshafts) are custom and 40mm different in length which may cause a bit of torque steer but are much thicker than stock so I doubt that's the cause.
Diff centre is ashcroft - helical style much like torsen (is there any way a helical could end up driving one side more then the other?).
Power is 225bhp.
Camber -2 degrees
Toe in 5 degrees (not adjustable unfortunately)
167 kg on left wheel and 190kg on right wheel with me in there.
Suggestions much appreciated.

check tire pressures

I have had similar on power/off power changes in direction on both my wife's 97 and my dad's 99. The 99 straightened right up when we installed poly bushings to replace the worn rubber bushes. It was clear that the A-arms were moving enough to cause rear toe changes under power. Sounds like you already have poly bushings so this might no be your poblem.

Does it behave any different with a passenger in the car?

Tyre pressures 26psi both sides

I still have original rubber bushes in the hub carriers (ie. the big one at top outbound position) Suspect that is the likely cause for now. Hopefully I can find a poly bush that comes as a pair and not a whole set.
Haven't actually tested it with a passenger but that is a good suggestion.

Sounds like its crab walking. Maybe the rear end is not square to the frame. If u have ever been in a car that was in a major accident and the frame was damaged but had a back yard repair done. It does the same thing.

It does indeed feel like that but only under heavy acceleration and when I come off the throttle. Tracks straight down the road at steady speed and geo figures are pretty equal for both sides.

Do you have the same size tires on the rear end?

This is characteristic of a TORSEN when a rear brake caliper is starting to freeze up. Drive for a few miles, then feel how hot the wheels are. If one is noticeably hotter than the other, you need to check the caliper.

yep same tires on all corners. Tried with a friend and it still behaved the same way (and he's a fat bastard too). Kind of feels like driving a forklift which is kind of scary. Have some poly bushings on the way so hopefully they help things.

Thats an interesting thought. Mind you I don't think they are binding as its very easy to push the car around the garage. Never the less I'll have a feel if the hubs are heating after a drive.

<p>when i bought my 90, it did this. i did a driveway alignemnt, and it got a little worse. i assumed it was caused by a shitty thrust angle, and i thought i had induced more thrust angle. it did it with 3 differnest sets of tires, no matter what pressure they were at,&nbsp;or if they were equal.&nbsp;i got it professionally aligned, and it fixed it, but i had almost no thrust angle, so who knows.</p>

Even if tires are directional, try swapping them side to side and see how it reacts. Obviously, test this out in a safe area.

That might be your problem.

Problem solved now. It was the factory top upright bushing - had no idea just how flexy these rubber ones are. Have a poly bush one in now and its all sorted.
Steering is still a bit nervous for my liking but throttle has no influence anymore (unless your going sideways :)

I thought you already had all those bushings upgraded to poly.

I said in the first post I had stock bushes in the uprights and poly in the wishbones. I actually suspected the bushes all along but wanted some advice/sanity check before I replaced them. Anyway as I said it's made a world of difference.

Check the wheel bearings as well, my daily had wheel bearings going out and it did the same thing you are describing. New wheel bears and hubs, problem solved