Ok..what Is Wrong With My Car ?

[shonen]

Alright this is really driving me crazy.....

I dont know how to explain this in words but ill try my best and hopefully at least one of you can understand what im trying to say.

On straight line acceleration the car seems to "shift" or move/steer to the right then come back on line when I take my foot off the accelerator. It is a similar sensation to when you scrabbling for traction in 1st and 2nd....except im not losing traction and it happens at the higher end of 3rd gear.

I have had a wheel alignment done already so I dont think its an issue with alignment.

The only possible explanations I can think of are these.

The rear end is too light ? and not enough downforce in the rear.

I took the jack and spare tyre and wing off almost at the same time. and it shaved almost 30kg from the rear of the car. Put the spare tyre back and it is noticably better. Would a wing make THAT much difference ?

Or I think maybe my diff has had it.....is it possible to open wheel in a straight line ? cause at time it DOES feel like one wheel is spinning faster to cause this shift to the right...

Or my tyre sizing is wrong

I have 235/40/18s up front and 275/35/18 rear.

Previously I had 265 at the rears..but on my last tyre change decided to go for the 275 for the extra fattness

Finally, can the hicas system play up during straight line acceleration ?

and would it have similar effects to what I am experiencing ?

Thing is it doesnt happen ALL the time...only on certain roads, however I have never experienced this in the past 2 years that I have owned the car and I have pretty much been using the same roads....

very confused and need of help................

EDIT

Forgot to mention that at first I thought it was my back left wheel as it kept on deflating to 19psi over a few days. This was due to a pretty bad spin out at wakefield and the dirt got between the rubber and wheel. On this note, could anything have been affected that might not have been fixed during the wheel alignment ? ie wheel bearing ?

Edited August 24, 2005 by shonen