Plus 8 Brake Bias?

[Pauloamore]

Chaps,

I've just had a master cylinder fitted to the brake system on my 1987 Plus 8. Problem is, that the rear wheels are quite easy to lock up. A sharp dab of the brake pedal is all it takes. Way way before the front wheels feel like they might lock up.

So, 1st question, is that kind of (rather odd) brake bias normal? I.E. Favouring the rear drums as opposed to the front discs.

2 - Is it dangerous?

(My MOT was carried prior to the Master cylinder being fitted and the testers found the rear brakes to be stronger than the front.) I'm told that the pads etc are free, nothing is sticking etc etc.

Any advice would be greatly appreciated in advance.

Regards
Paulo
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[sharkie]

I have the same opinion that this era of +8 has too much brake bias to the rear. This can be alarming in some conditions as the rear brakes lock up and the car spins. Two cures are to either fit the later 4 pot caliper on the front to get more front braking or to use a brake bias valve in the rear brake line in order to reduce rear brake force.

[GreenV8S]

The brake bias valves that go in the rear line are designed to compensate for weight transfer under braking (dynamic balance). However, the static balance has to be correct too, and these bias valves won't achieve that. An easy way to test the static balance is to get the car cornering close to the limit of grip on a slippery surface and gently apply the brakes. If the front washes out there's too much static bias to the front; if the rear steps out there's too much to the rear. Ideally it should be neutral with a very slight bias to the front.

Once the static balance is right you can test the dynamic balance by seeing which end locks up first in slippery conditions and in very grippy conditions. This is easy to feel if you have the car cornering slightly while you brake firmly.

Obviously this sort of testing needs to be done in a safe place.

[Pauloamore]

Thanks guys.

I spoke to a very helpful chap at Brands Hatch Morgan.

Having rallied PLus8's he felt that they often hae a rear balance on the very hard braking.

I've had the rear drums loosened off and have found a seal in on of the front calipers has expanded and stuck so have now got that sorted...

Thanks for your advice!