M400 Brakes locking up

[kinetic]

Always thought the brake bias on my M400 was a little too keen to lock up the fronts under hard braking but I recently switched to DS2500 front pads ( leaving the rears untouched) and now its horrendous! In fact positively dangerous! Even moderate braking will now lock up the fronts no matter how progressive I try to be.

Anybody had any similar issues? Anybody found a solution?
Could it be down to a mismatch in pad thickness between front & rear rather than just a harder pad material on the fronts?

[Ash M400]

That sounds very wrong.

I have done the same and no problems whatsoever.

I do get it when the tyres are clap cold, but once warmed up, no prob.

I would get it looked at, it sounds as if the rear brakes are not working properly.

>> Edited by Ash M400 on Sunday 23 April 16:08

[DanH]

kinetic said:

Always thought the brake bias on my M400 was a little too keen to lock up the fronts under hard braking but I recently switched to DS2500 front pads ( leaving the rears untouched) and now its horrendous! In fact positively dangerous! Even moderate braking will now lock up the fronts no matter how progressive I try to be. Anybody had any similar issues? Anybody found a solution? Could it be down to a mismatch in pad thickness between front & rear rather than just a harder pad material on the fronts?

I'm a bit puzzled. If you think you have to much front bias, why would you have fitted more grabby agressive pads to the front only further moving the bias forward?

Pad thickness should be irrelevant. I wonder if your rear brakes are working properly?

[m12_nathan]

I was told to make sure I changed both front and rear pads to the better compound when I did my 3.

I had the later biasing valve fitted and after a lockup at 110mph on a damp road had it changed back to the original one which was far less scary imo.

[DanH]

m12_nathan said:

I was told to make sure I changed both front and rear pads to the better compound when I did my 3. I had the later biasing valve fitted and after a lockup at 110mph on a damp road had it changed back to the original one which was far less scary imo.

Didn't the later valve give you more front bias so presumably you locked up the front?

[m12_nathan]

Correct, it seemed to lock the front with the lightest touch using ds2500 on a damp road, it certainly widened my father in laws eyes as i was demostrating the car to him! I had it reverted to the earlier setting (maybe just remove the extra valve?).

[joust]

IMHO bad idea having DS2500 on only the fronts in wet/damp weather like we've had this weekend. DS2500's are seriously "sharp" - either get some DS2500s on the rear as well, or only use the DSs when on track (it's 10 minutes to change them). I've only ever put DS2500s on front and rear on the M400 - I had DS2500s on SO3s on the M12 which was reasonably OK but even that was pretty much at the limit so with the Corsas I made the choice to change them all around.

As also suggested jack up the rears and check they are working correctly with a mate helping as if it really is as bad as you say then there could be something wrong?

J

[joust]

DanH said:

Didn't the later valve give you more front bias so presumably you locked up the front?

Yep - locking up the rears means it's much easier to do a 180 than the fronts, although when I did occasionally lock the rears on my old M12 2.5 on track I managed to catch it reasonably easily.

J

[kinetic]

O.K, I think I'll change the rears for DS2500 aswell - and get the rear brackes checked out!

[Ash M400]

joust said:

DanH said: Didn't the later valve give you more front bias so presumably you locked up the front? Yep - locking up the rears means it's much easier to do a 180 than the fronts, although when I did occasionally lock the rears on my old M12 2.5 on track I managed to catch it reasonably easily. J

Bloody show off