Squirming under heavy braking
Discussion
Just been to Brands in my 'new' car (a '99 306 Rallye with 61k)
The car was really good fun, with loads of lateral grip and in general very well behaved. However, whilst under heavy braking, the car seems to squirm (sorry if I don't have a better way of describing it) If I really stand on the brakes, the car becomes unsettled.
What could be the cause for this? I was running in slightly taller tyres (50 profile instead of 45) then in my last car (Clio 182, which didn't suffer this). Is there a big enough difference in tyres to cuase this, or could it be something in the suspension setup, which is still standard.
Cheers in advance!
tbf
The car was really good fun, with loads of lateral grip and in general very well behaved. However, whilst under heavy braking, the car seems to squirm (sorry if I don't have a better way of describing it) If I really stand on the brakes, the car becomes unsettled.
What could be the cause for this? I was running in slightly taller tyres (50 profile instead of 45) then in my last car (Clio 182, which didn't suffer this). Is there a big enough difference in tyres to cuase this, or could it be something in the suspension setup, which is still standard.
Cheers in advance!
tbf
If the tyres aren't directional, try swapping them from side to side. If the are, try swapping front - to rear on the same side. I'm not sure why it happens (and your car might be different) but mine does a similar thing once the tyres have been on for 5000 miles or so.
Failing that, maybe it's the bottom wishbone moving backwards on its bushes far enough to reduce the castor appreciably - maybe harder "competition" bushes will help?
Failing that, maybe it's the bottom wishbone moving backwards on its bushes far enough to reduce the castor appreciably - maybe harder "competition" bushes will help?
Try looking on the Powerflex website to see if they do a kit for your car. As for difficulty, I'm not that familiar with the 306 but it's probably a "3-4 spanner" job in a Haynes manual.
www.powerflex.co.uk/
www.powerflex.co.uk/
Cathar said:
Could also be a matter of brake bias and the rears overbraking. Can you confirm the fronts are locking first when you really stamp on the pedal?
The fronts don't lock up when I really stand on the brakes. Going to get the bushes upgraded when I get home as a starting point...
Nice choice of car 
Are you running the stock 15" rims?
Stock tyre size is 195/55R15, so 50's are about the best size ideally... nice cheap tyres in that size too, and a wider range of more track orientated tyres!
I'd say maybe the front P-bushes (back of the front lower wishbone) are worn, and these can allow yawing about the worn bush under excessive braking, which can make the car feel unstable. If it's never had them done then now is the time @ 61k...
Also, the Rallye's have a rear-brake compensator mechanism, and as the car pitches forward it alters the rear brake bias. I'd maybe check that is free acting and not siezed. This is found on the offside area of the rear torsion beam setup.
Tyre pressures optimal for track work?
You shouldn't be feeling any really heavy movement on a smooth race track, though it would be noticeable on your average UK road... but that would be the same with any car I'd expect. The gti6/rallye is quite a pointy car, but I wouldn't say that this is something you should be taking exception to in this case if the car was right...
Have a search/look around www.306gti6.com in the brakes section, lots of people who track Rallye's and Gti6's so could help you out maybe.
Dave
Are you running the stock 15" rims?
Stock tyre size is 195/55R15, so 50's are about the best size ideally... nice cheap tyres in that size too, and a wider range of more track orientated tyres!
I'd say maybe the front P-bushes (back of the front lower wishbone) are worn, and these can allow yawing about the worn bush under excessive braking, which can make the car feel unstable. If it's never had them done then now is the time @ 61k...
Also, the Rallye's have a rear-brake compensator mechanism, and as the car pitches forward it alters the rear brake bias. I'd maybe check that is free acting and not siezed. This is found on the offside area of the rear torsion beam setup.
Tyre pressures optimal for track work?
You shouldn't be feeling any really heavy movement on a smooth race track, though it would be noticeable on your average UK road... but that would be the same with any car I'd expect. The gti6/rallye is quite a pointy car, but I wouldn't say that this is something you should be taking exception to in this case if the car was right...
Have a search/look around www.306gti6.com in the brakes section, lots of people who track Rallye's and Gti6's so could help you out maybe.
Dave
shirley temple said:
check the strut top mounts, most people over look these and only worry about the bottom arm bushes. The top of the suspension leg moving around has a similar effect to worn lower bushes (remember RS2000 and Capris anyone?)
Mark
Mark
Replacing all the bushes and upgrading the ines I could made all the difference
theboyfold said:
shirley temple said:
check the strut top mounts, most people over look these and only worry about the bottom arm bushes. The top of the suspension leg moving around has a similar effect to worn lower bushes (remember RS2000 and Capris anyone?)
Mark
Mark
Replacing all the bushes and upgrading the ines I could made all the difference
most people forgets the top mounts!!, I've lost count of the number of guys(and girls) having new bottom arms/beefed up lower bushes and uprated springs and shocks fitted to clapped out mega mile strut top mounts!! I guess the "I've got new strut tops" isn't as impressive as "I've got polywoshername lower arm bushes!!)
Mark
[quote=ELAN+2] most people forgets the top mounts!!, I've lost count of the number of guys(and girls) having new bottom arms/beefed up lower bushes and uprated springs and shocks fitted to clapped out mega mile strut top mounts!! I guess the "I've got new strut tops" isn't as impressive as "I've got polywoshername lower arm bushes!!)
Mark [/quote]
I didn't forget
Mark [/quote]
I didn't forget
Edited by theboyfold on Monday 2nd October 08:35
Edited by theboyfold on Monday 2nd October 08:36
Gassing Station | Suspension, Brakes & Tyres | Top of Page | What's New | My Stuff