Problem with straight line braking

[daves16v 1]

When braking heavily in a straight line from about 40 upwards the car starts to weave very slightly, not all over the road but enough for it to feel very unsafe.

 

The shocks and springs (Koni kit) were changed about a year ago and the tyre pressures are ok. The only other thing I had changed recently was the alloys which came with tyres on the cheaper end of the market. I can't remember the car behaving like this before I changed the alloys and tyres.

 

My guess is the tyre side walls are very soft and giving way.

 

Anyone else experienced this?

 

Dave

[randal 0]

Dave, have you had your balance and tracking sorted? I had a similar problem on the car before the C, and it was solved with that. It's OK, mine does the same from about 40 upwards - scary thing is most of my driving is motorways. M25, 'orrible grooves in the road coupled with the braking probs means jumping lanes when braking!

 

Not good!

[dazzyvr6 0]

it could be down to your brakes

[daves16v 1]

The alloys were new so came balanced and I had 4 wheel alignment done shortly after the Koni kit was fitted.

 

I've just put new 280mm discs and pads on but I still had this problem with the old disc/pads. There is absolutly no pulling either side when braking.

[dazzyvr6 0]

im confused now...the title says problem with straight line braking so that sugests one caliper is working harder than the other

[dr_mat 0]

I doubt the calipers are working unevenly if it's weaving. It would pull to one side consistently if that were the case.

Weaving is most likely camber following, they all do that to some extent, but this will get noticeably worse if there's ANY play in any suspension joints at all, or if the tracking is out.

So you want to be thinking about ball joints, wishbone bushes, track rods, top mounts and so on.

[dazzyvr6 0]

the title sugests its only pulling to the side under heavy braking if it was a ball join etc t it would pull to the side all of the time,if the traking out there would be other symptons aswell

[dr_mat 0]

Ball joints can flop around all over the place and cause weaving, but usually all they do is accentuate the effect of the forces applied to the wheel - i.e. they make camber following and bump-steer much worse.

IMHO.

The description says "weaving", not "pulling to one side" - we need more clarification from the man with the problem! :)

[daves16v 1]

OK, weaving is correct. The car does NOT pull to one side in the case of a dodgy caliper. There is no pull feeling through the steering wheel, the feeling is felt through the whole car. It feels as though the car is drifting one way then the other but only very slightly, you probably can't see it if you were to look at it from the outside. The wheels are NOT locking up either.

[dr_mat 0]

Ok, how many miles on your suspension components?

You might wanna consider checking the rear axle bushes and wheel bearings, plus checking out the front BJs and co then.

[daves16v 1]

78k.

 

I was told by C & R about 6 months ago the rear axle bushes were worn.

 

Tyres haven't been mentioned in any replies..........any thoughts?

[dr_mat 0]

Start with the rear axle bushes then!

It's surprising how much movement can come from the back end...

The tyres are unlikely to cause this, even if they're really high profile (60+), unless they have bald spots or something.

[daves16v 1]

I guess it's a good starting point.

 

Thanks for tips :)

[Kevin Bacon 5]

Could be one of many things........

 

Rear wishbone bushes? They take a pounding when you brake hard.

 

Wider [than standard] tyres can cause tramlining on uneven surfaces too. Try your old wheels and see if the problem persists.

[Henny 0]

rear axle bushes provide flex to give the Corrado a passive rear wheel steering effect. If they're dead, then you'll be getting this effect when you AREN'T going around a corner which will be hi-lighted when braking... :?