Jump to content
SAU Community

Recommended Posts

When I'm on the track and brake really hard with a completely empty boot I find the back end of my car wiggles around a bit which can turn into a rear end slide out if I turn my front wheels too much more than straight.

It doesn't seem to to do it with full kit on though, perhaps the extra weight in the boot is stabilising or something.

Anyway, I've just had my front rotors replaced with slotted DBA4000's and the standard rears skimmed. Now on heavy braking I am getting the same wiggling but more pronounced. It's s little scary because I feel now I can't use the full force of the brakes in case I go sideways.

Oh and also I had the brakes bled at the same time.

Any ideas peeps?

Link to comment
https://www.sau.com.au/forums/topic/48509-car-wriggling-with-big-braking/
Share on other sites

I was getting this towards the end of the last Wakefield trackday, it only happened when I really heated up the back tyres and they became a bit worn/skatey.

Does it happen out on the street or only at trackdays?

benm - it did only happen at the track but now on the street too.

Adrian - I do actually do that on the track. Got it nearly down at Wakefield but EC corners still a bit too big for my balls.

So there's no adjustment for front/rear bias that can be made?

benm - it did only happen at the track but now on the street too.

 

Adrian - I do actually do that on the track.  Got it nearly down at Wakefield but EC corners still a bit too big for my balls.

 

So there's no adjustment for front/rear bias that can be made?

Still got the HICAS?

Tried adding a bit of rear toe in?

Neg camber on the rear?

I have a few others, but these are where I would start :P

At the risk of stating the blindingly obvious, it's probably happening because you are losing grip/traction at the rear. Might seem like a simplistic sounding statement but this can happen and end in a spin like you've described. The rears losing grip is a bastard of a thing to have happen but there are only so many reasons for it.

When you brake weight transfers onto the front and off the rear. The more the weight is transferred forward the more chance you have of losing traction as the rear has a tendency to rise; watch the Moto GP bikes brake for corners with their rear wheel in the air, same principle. A soft/stuffed rear/front shock combo will do it, opposite to the way drag cars are set up to squat in the rear with soft shocks. When the back end lifts enough it loses traction and under braking can lock easily. The fact that you've given the brakes some attention and are now probably generating more weight transfer, and that the lose happens more when there is nothing on the boot, supports this.

Ditto wheel alignment; if it's not set up right it will go birko when the weight is transferred to the front and lose traction again.

If you are running worn or crappy tyres on the back it will cause them to lose traction/grip quicker than if you are running tyres that are good quality.

Any of these seem familiar?

I would start with the alignment....but it could just be the front brakes are working well.

I find that my gtst used to lighten up a fair bit under really heaving braking when using good tyres as well :P

It could be that you need to reconsider how you brake into a corner on the track, generally you would make around 90% of your braking in a straight line...when you do this it doesn't matter too much if the rear end is light. If you are braking too hard as you turn the rear can get too light on you and the car spins....

Hmm,

The phenomenon I'm describing I have also experienced in your car Duncan (now that I think about it).

Lately I have noticed a squeaking coming from my front end when the car is stone cold only going over biggish bumps. This goes away when warm and although I was thinking creaking springs, springs don't warm up, but shocks do. I have done 82000 k's and the rear left shock shows signs of having leaked at some stage (all original shocks) but doesn't anymore. Also I have hit the bump stops on the front with mega hard braking before the last turn at Wakefield several times. Perhaps my shocks are stuffed?

Sigh. Time for $2300 coilovers.

Thanks for the help guys.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Yeh I think i'll message an old contact i had for ages that manages his own tyre shop now.. n tell him what i want n work with him before ordering..  Got this 17x9 +30 Driftteks on 245/45/17 PSR Drag Radials on the rear.. They fit well - for your reference in future - Rear guards  have been lipped in & minimal to non flaring of the rear Gaurds.    
    • If only it were that easy! I also needed to remove seats, shocks, brake calipers, send my car through a fence, and use measuring and ended up guessing because I didn't remove seats, shocks and brake calipers. It can be hard sometimes Can be a little more complex than 'just measure' if you want to truly measure the entire wheel through all of it's suspension travel. But if you aren't going for every last mm then yeah, you can check the space you currently have and guesstimate.
    • If you own a car, and it has wheels on it, and you know the offset of those wheels, and you have a measuring device, you have everything you need to work out if other wheels will fit.
    • Will this fit? but they are staggered set - RAYS 57DR SEMI GLOSS BLACK 18x8.5 +37 | 18x9.5 +38 5-114.3 STAGGERED SET   or If no go could just get a set 4's wheels of 18x8.5 +37 5-114.3 - would i run 8.5's 235s up front n 245's at the back if I do?   Thanks.        
    • Put a clamp on your return line. I have a feeling it's sucking air, and introducing bubbles to your fuel. With a lot of fuel, less problematic. I'd honestly be redoing all the lines in the tank and clamps on everything.   Also, you've given two different answers to the same question: Asked if being followed by the police you could get down to use the whole tank, you said yes you could, so long as you keep off boost. However, you then followed this up that free revving, it would also cause the issues. I'm doubting free revving is enough to make any noticeable boost on what is likely a decent sized turbo.   So now I have to ask, can you actually drive it lightly and use all the fuel, or does it break up even free revving? Also, have you put a fuel pressure gauge on it? Can you hear the pump change noise at all when you're having this issue?
×
×
  • Create New...