rear wheels lock up
Discussion
Now, now Simon. I remember you making a comment about my brakes, in that I had more brake dust covering the back wheels than the front. Generally, I would say they where about even and I am quite happy with my setup. I think you should check that you have the front and rear M/C correct and then play with the balance bar (I am not sure what the factory would have done adjustment wise prior to SVA). I would think that the rear wing would only have an effect at high speed in terms of assisting rear wheel lockup!
You may also remember a thread on here about brake balance and I am not sure what the conclusion was. On my track day, in the wet (very wet), I had the back locking also but most of that was dropping down a gear with massive engine braking, great fun but did make me spin on a six pence once!
Have you stiffened your suspension yet, I would have thought your softer setup would perhaps assist the back lifting and causing less grip as the front nose dives, how was it before the change?
You may also remember a thread on here about brake balance and I am not sure what the conclusion was. On my track day, in the wet (very wet), I had the back locking also but most of that was dropping down a gear with massive engine braking, great fun but did make me spin on a six pence once!
Have you stiffened your suspension yet, I would have thought your softer setup would perhaps assist the back lifting and causing less grip as the front nose dives, how was it before the change?
hi guys lets leave the can of worms closed !!! would not say it was a problem the rears were quite easy to control ,yes pb3 i still have the soft springs on the front this helped with turn in as it would not understeer at all infact it was the rear that let go 1st much to my suprise for some reason i exspected it to undresteer.do you think a stiffer front setup would improve it under hard braking ? would not want to loose any front grip as the change of direction was awsome ! the wheel color was identical so i think the brakes are working pretty even ,the reason i noticed yours pb3 was because your rear wheels were a lot dirtier than the fronts (with brake dust ) i would have thought this shows that they are working harder than the fronts .simon
>> Edited by tuxman on Monday 5th September 13:09
>> Edited by tuxman on Monday 5th September 13:09
Dont know your exact set up but chances are it's just a minor adjustment to the bias valve (assuming you have one)...given prevailing dry conditions.
The MC ratio (and pedal bias bar) will tend to lead the front-to-rear braking distribution effort at lower pedal pressures. However, as the line pressure rises past a key point, the bias valve will divert more pressure to the fronts - typically on a 3:1 ratio or thereabouts, for a simple bias valve.
AP has a nice diagram of their bias valve and pressure distrbution here.
www.apracing.com/car/cylinder/cp3550_1cd_iss6.pdf
So suggest a bit more front bias via the valve?
The MC ratio (and pedal bias bar) will tend to lead the front-to-rear braking distribution effort at lower pedal pressures. However, as the line pressure rises past a key point, the bias valve will divert more pressure to the fronts - typically on a 3:1 ratio or thereabouts, for a simple bias valve.
AP has a nice diagram of their bias valve and pressure distrbution here.
www.apracing.com/car/cylinder/cp3550_1cd_iss6.pdf
So suggest a bit more front bias via the valve?
Ultima Factory said:
We would just like to point out to readers of this forum that the braking system on an Ultima incorporates a lockable bias bar fitted to the brake pedal which can easily be adjusted to alter the front/rear bias of the brakes.
Ideally it should be set up so that the front brakes lock up just before the rears.
Do you have a bias (proportioning) valve giving variable distribution according to the amount of braking, or just a static (albeit adjustable) balance bar?
tuxman said:Ouch!
HI Joust, thanks for the offer to have a look at your brakes , i,m free on saturday would you like to have a ride over for a coffee .......... better still with your reliability issues i had better come over to yours !!!!!! 
simon
I'll be at Silverstone if you want to "pop over", or will your bum be too numb by the time you get there
J
GreenV8S said:
We would just like to point out to readers of this forum that the braking system on an Ultima incorporates a lockable bias bar fitted to the brake pedal which can easily be adjusted to alter the front/rear bias of the brakes.
Ideally it should be set up so that the front brakes lock up just before the rears.
Do you have a bias (proportioning) valve giving variable distribution according to the amount of braking, or just a static (albeit adjustable) balance bar?
It's a balance bar.
joust said:
Simon,
You are more than happy to inspect my M400's braking system if you want an answer on how to get it right.
J
Stig, ok, I'm out of here, got the point, no need to say it.......
Ooooh, just as well I've not been reading this thread J or your a$$ would be grass by now
You can get away with your brake setup because of the paltry power output 
Besides, you spend more time on the Ult forum than Knoble these days - very telling
You ready for a 'proper' car yet
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