braking

[dogvet]

I have 4 pots on front, singles on back, dot 4 fluid, the car did a dry v quick track day a month ago, but yesterday at Donington the rear left kept locking up. Going into the Melbourne loop was quite entertaining!!

Any ideas?

pad /disc glaze? boiled fluid and air in system?

It was quite wet all day at Donington so the brake system did not really get used until one dryish session pm.

Thanks in advance.

[Alex Wong1697456877]

I've never quite got my head around this. When I used road front pads, the car tended to lock the fronts first. Now I use red stuff front pads and front braking is superb, and the rears lock up first! I can only assume that the car is nose diving and the back is going light, allowing the rears to lock up first. question.gif

[Jason Plato]

Same problem here especially when the brakes have warmed up and you use them REAL hard ....... Its worrying that if you had to do an emergency stop them you could end up well out of shape and probably in a ditch ! .

 

A brake bias control is a winter upgrade for me together with some cooling ducts to he rear brakes .

 

Alex - maybe the Red Stuff pads are not as good as your previous pads and now the rears are out performing the fronts ???

Dave

 

Edited by - Dave J on 26 Sep 2001 07:54:49

[R2D2]

If the front dives during braking this may unload the rear wheels and cause locking. Quite a few cars have adjustable pressure limiting valves fitted into the rear brake circuits which have a connection to some part of the chassis so that when dive occurs the rear braking effort is reduced. The Alfa Sud has quite a neat system.

 

If you can get you hands on one of the old Taplow accelerometers that they used for MOT brake tests before rolling roads you could get some idea of the different levels of deceleration with the different pads you are using.I would guess that dive would be proportional to decel.

[ashaughnessy]

Chris Flavell, Are you confusing dive with weight transfer? It is weight transfer that causes the rear wheels to be unloaded and weight transfer occurs regardless of whether there is dive. I'm not saying there isn't anything in the suspension setup that might cause the problem, simply that I think you're confusing two different phenomena.

Anthony

[Alex Wong1697456877]

The red stuff pads have been stunningly good. I don't think there's any chance that they're not as good as my old road pads. There is still a question with regard to their durability though.

 

Alex

[EFA]

Alex

 

I've done 2000 miles on Reds and they seem virtually unworn.

 

Although I've only been on the road, I think you know how I drive!

 

 

 

Fat Arn

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[Alex Wong1697456877]

Mine seem to be wearing quite quickly. I must stop using that middle pedal so much! smile.gif

 

Alex

[R2D2]

I don't think that I am confusing dive with weight transfer.

 

As braking force operates at ground level through the tyre contact patch and inertia operates through the CoG there must be a torque produced during braking and with most suspension systems this will produce dive as weight will try to move down at the front and up at the rear.

(Weight Transfer = Braking Force * CoG ratio)

 

I do accept that weight transfer will unload the rear wheels even if there is no dive as the model would still be valid even if there was no tyre or suspension deflection.

 

What would happen if the CoG was at ground level and the torque was zero as I think that the amount of weight transfer produced by a change of speed is a function of the height of the CoG and the wheelbase.

 

The Alfa Sud brake system only senses dive to reduce rear braking effort and I

suppose if dive was completely eliminated an inertial valve may do the same job.

 

I haven't driven a new Seven as mine is an 89 car (which does dive to some degree) but even anti -dive front susension may not stop the rear from jacking due to the applied torque.