Loosing rear end round track

[Ryan Spiteri]

Hi guys had my 172 out for its first track day at Croft this weekend. The rear end is very unstable and span out twice during the day. I tried adjusting dampening and tyre pressures throughout the day but couldn't sort the issue. I also found my bias valve isn't working as it should and was locking the rear wheels which could be the issue for the handling but I'm just wondering if anyone has any other suggestions of what could cause it.

 

[NorthloopCup]

Hi guys had my 172 out for its first track day at Croft this weekend. The rear end is very unstable and span out twice during the day. I tried adjusting dampening and tyre pressures throughout the day but couldn't sort the issue. I also found my bias valve isn't working as it should and was locking the rear wheels which could be the issue for the handling but I'm just wondering if anyone has any other suggestions of what could cause it.

What's the geometry like on the rear end? What spring rates are you running at the rear? What tyre pressures also?

 

[JamesBryan]

Was it wet or dry? Could it have been lift off oversteer?

 

[JB21]

I've done a track day with more rear bias than normal (abs disabled) and had no real issues with a lose rear end, the rears would lock up though. Was you trail braking hard into corners?

 

[gingerphil]

Locking the rear wheels won't be helping!
Surprisingly, I remember reading that in a certain scenario more brake bias to the rear prevents them locking.

 

[JB21]

Locking the rear wheels won't be helping!
Surprisingly, I remember reading that in a certain scenario more brake bias to the rear prevents them locking.

Better in the wet supposedly as the fronts don't lock up as easily.

 

[Ryan Spiteri]

It was dry all day so good conditions. It's got 300lbs springs on the rear and adjustable dampening (gaz golds). Also got -2 camber with ns2r tyres, tried them at a few different pressures but didn't make any difference

 

[Adam G]

Were your rear tyres hot?

 

[sam JFM]

You have installed the camber shims correctly?