Death Trap

[mattysupra]

In need of some help please.

My R34 GTR used to handle really well.

However i entered TOTB an decided to have the 4 wheel aliment done before i got there. Also i should add that i run different tyres to before also. I drove around on them running the engine in and they seemed o.k, but defo not as grippy as before. To top that i also have enlarged the front brakes to Ap 6 pots and 360mm????? rota's i think.

ANYWAY, the car is a death trap. It suffers really bad from lift off over steer. It also gets very wobbly in a straight line when breaking hard. In fact i was breaking hard on motorway today on a slip way (changing from one motorway to the other) as someone pulled out on me, i was on a slight bend and the rear end was stepped out while im trying to break and steer around the car that pulled out on me! Normally i could of just hit the breaks but i was faced with having to try and steer around the car sideways as i could not touch the bloody breaks as they had sent me sideways!


So, what is wrong? I dont have Hicass ! i have had the car checked at 3 places now and all 3 say that alignment settings are spot on. Well apart from camber and caster on one of the front wheels is slightly out but this cant be adjusted? So why is it trying to kill me?

help please before i end up in a ditch

[fourtoes]

Brake bias maybe Matty?

Bob

[TJB]

Hi Matty , pure stab in the dark .... rear wheels , tracking , not enough toe-in ......
makes for very very unstable , as you describe...........

Lee.

[V1H]

if it only happens under braking, then i would check brakes first esp as fourtoes mentioned brake bias, however, you mentioned lift off oversteer, in which case i would also look at bushes(no idea which ones?), as worn ones wouldn't show up in static alignment but might impact on handling when moving.

[Clive S-P]

Were any changes made to the coilover settings, otherwise what Bob said!

[mattysupra]

im positive its not break Bias as i suffer from lift off over steer also.


For instance, at TOTB this year that had a bend that tightened half way around . I entered this bend and found grip. But as it got tighter and i was off the throttle the tighter i turned the more the rear end was starting to step out !


But lets say it maybe a mixture of Bias also.

Lets say that under breaking the rear end started to float around. What do i need? do i need more or less rear breaking?


O and im also sure i have no worn parts. Im lucky that i have a 2 poster ramp in my garage and i have inspected all bushes again tonight. Also the place that did my aliment drove the car over a suspension checking machine that bounces the car around and it came back as near perfect!

[mattysupra]

can some one post up settings for a 32, 33 , 34 so i can compare. Im thinking the settings im using is wrong. The setting i used was supplied by a tunner and they matched what was already loaded on the alignment software.

BUT as the R34 is pretty rare in the U,k and alignment is not really done by a lot of owners im thinking that i may be one of the first to actually realise that the setting advised are wrong?

[GRowsell]

Surely you nearly answered the question yourself when you mentioned you'd changed the tyres to?

Also i should add that i run different tyres to before also. I drove around on them running the engine in and they seemed o.k, but defo not as grippy as before.

What were they before, and what are they now? And how many miles have you done with them? And what pressures are you running?

[mattysupra]

Originally Posted by GRowsell

Surely you nearly answered the question yourself when you mentioned you'd changed the tyres to?



What were they before, and what are they now? And how many miles have you done with them? And what pressures are you running?

I was using Bridgestones before. (which i was never impressed with on my Supra)

I changed to a Maxxis tyre, there best tyre so should be good? But i noticed a difference straight away. I put this down to the tyre not being scrubbed in.

Well the Maxxis tyres now have a few thousand miles on them.

I have tried all types of tyre pressures. In fact the best grip i found was running suspension on the rear on full soft and the tyres at 22 psi! Still really bad tho.

Have a look at this video, even launching the car in a straight line the car is all over the place !

[GRowsell]

Without saying what Bridgestones (RE40, RE50, RE50A, RE70 etc) it doesn't mean a huge amount, it's like talking about handling and saying my Ford doesn't handle as well as my Vauxhall...

You'll find that there is a world of difference between just those tyres listed above, even the RE50 and RE50A are hugely different, so you really need to be thinking tyres before you worry about the other variables.

I have even had HUGE handling characteristic changes from a slightly different size of the same tyre...

400+hp R34 GTT (rear wheel drive) in Spa... initially huge oversteer with Toyo 888 as a 265/35-18, then (same day, same track) I dropped to a 235/40-17 Toyo 888 and the car handled like it was on rails.

It is not just tyre compound, but also sidewall strength (RE50A has much stiffer sidewalls than the RE50), tyre temperature, tyre pressure, tread depth, what car, what surface and also what driver.

I'd put money all your issues are with those Maxxis ditch finder tyres (bet they were a good price ).

Also, 22 PSI sounds way, way too low a pressure.

[waynegts]

did they have to change the settings much to get them to where they are now? id try some different tyres, could you borrow someones wheels/tyres to see before splashing out on some more tyres

[davew]

Matt, long shot here. Have you had the wheels off since you had the geometry check? Just when did the problem occur??

[mambastu]

What allignment settings are you using now ?

[tonigmr2]

I see you have you adjusted the coilovers. If you've hardened them up all round you may find the car very difficult to keep straight. Potentially if your front settings are soft and the rear hard you'll oversteer like a bitch too. Are you sure the adjustment on the coilovers is working on all four?

Secondly do you have adjustable ARBs. If you've tightened them up (maybe the alignment place?) you may find the rear end extremely skittish.

Third, tyres. Maxxis?? I've not seen any performance tyre from that manufacturer that has been rated particularly? What model as it were?

Trouble is you've changed quite a lot at once, so need to work through them all!

[mattysupra]

Originally Posted by GRowsell

I'd put money all your issues are with those Maxxis ditch finder tyres (bet they were a good price ).

Also, 22 PSI sounds way, way too low a pressure.

Dont know what they cost. They was given to me in exchange for Maxxis using my car on there stand.

But like i say they are supposed to be a high performance tyre. I think they are the same tyre as they use in the Drift Series.

As for the 22psi, yes this way to low and i dont run at this pressure. It is a pressure i tried at TOTB.