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FK8 Hard Braking : Rear end instability

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42
Coming from E46 M3 I have noticed a few time this FK8 CTR seems very light at the back when hard on the brakes.

While the pedal feel is good and cornering on the throttle / handling is probably better, the skittish rear end is less confidence inspiring than that 50/50 weight distributed RWD platform. Any steering angle on brakes can lead easily to over-rotation.

Anyone else felt it? Is there a solution?

Tyres good, pressures good etc.

Car still a great bit of kit mind you and bang for buck cannot be beaten. Even M2s I feel might struggle vs these as OEM products....
 
There was a post about this a few months back.

Don’t think a conclusion was made other than yes you do get some but not on track. I have noticed it but think used to it now.
 
yeah as my brake life will testify don't drive as hard as often as others, but I had it once, braking hard into a round about I knew well and I thought I was on the teacups at Thorpe park. Dry conditions, tyres warmed...

It was very weird and did knock my confidence a bit as to that point it had been unflappable

Still, serves as a little reminder to be on your toes
 
I reckon it's a bit of a trait with type-R's I remember having the same feeling way back when I had an EP3 but they where we'll known for it. I've had it a couple of times on the FK8 but nothing you can't control or adjust to keep the car in check. I'd imagine it would be great fun on a track though :woot:
 
I like it and it reflects the performance of the car. You only need to watch the BTCC to see the race cars standing it on their nose. I will add however that whilst i've felt the back end go light many times, only once was it a problem with the car over-rotating and that was when i got a corner very wrong in the wet and was trail braking into it. Was very impressed that a slight lift in brake pressure brought it back in line. What a car!!!! I love it!

To be honest, i ride a motorbike too so pretty sensitive to brake pressure and balance. I hate the feeling of the bike rear end lifting under braking so probably don't push it too hard. Will agree with you regarding the solidity of a front engined RWD platform though. Coming from an F80 M3, that tried to kill you on the way out of the corners, not on the way in!!!
 
I like it and it reflects the performance of the car. You only need to watch the BTCC to see the race cars standing it on their nose. I will add however that whilst i've felt the back end go light many times, only once was it a problem with the car over-rotating and that was when i got a corner very wrong in the wet and was trail braking into it. Was very impressed that a slight lift in brake pressure brought it back in line. What a car!!!! I love it!

To be honest, i ride a motorbike too so pretty sensitive to brake pressure and balance. I hate the feeling of the bike rear end lifting under braking so probably don't push it too hard. Will agree with you regarding the solidity of a front engined RWD platform though. Coming from an F80 M3, that tried to kill you on the way out of the corners, not on the way in!!!

Yes it all sorted itself out with ease of pressure on mid pedal :)
 
Have the geometry checked. Sounds like the rear wheels may be toeing out. Had this on my old FN2 after a poor setup from a supposed specialist garage.

Had the geo done on the FK8 and it was way out from factory (don’t ask me what it was as I’ve lost the sheet with the settings on). I’ve done two track days since and had no issues with the back end feeling light under hard braking.
 
I guess I really should do this (geo set up). The car has 4 newish tyres on it now and I left the geo as the wear on all 4 looked very even when they came off. Who has the right kit to align these CTRs? BMW's Main Dealer KDS system was the only place I could get the M3 done..

I'd be keen that the garage / provider was not only good at geo but also good at looking after the wheels etc :) . I'm in North East England but presume there are some national providers that can do this?
 
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There must be very little weight over the rear wheels under heavy braking so any steering input is likely to cause a loose rear end. As said once you ease off the brakes a little more weight is transferred back to the rear and restores grip.
 
I'd be keen that the garage / provider was not only good at geo but also good at looking after the wheels etc :) . I'm in North East England but presume there are some national providers that can do this?
I had 4 wheel alignment done at http://www.aj-automedics.co.uk/ it's in Durham.
A Computerised graph chart with +/- for each wheel was provided when done and the guy there is really friendly and knowledgeable. They where super careful with my wheels too
 
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