Brake bias

[russelld]

Hi All,

My car has just been for it's MOT and as normal at the garage I use the tester Tim has me sitting in the car operating the controls and brakes. I noticed while he was doing the brake test that the braking figures were higher for the back wheels than the front wheels, I had never noticed this before and was always under the impression that the bias on an Elise gave more braking force at the front.

I have CL5+ pads all round and solid vented disks so no imbalance of pad material. Thinking about it with 2/3 of the weight of the car over the back wheels ( which changes with weight transfer when braking )slightly more rear braking may be what is required for our cars ? Also the rear pads are larger than the fronts although they are operated with a single piston not 2 like the fronts.

Can someone who has a non servo car and an MOT imminent please observe what the readings are for their car and report back. Beer for the winner  !!!

Thanks 

Russ.

 

I hope I don't find out something is wrong going into Redgate on Tuesday 

[winthattt]

Russ,

I don't know but.....I expect the brake test measures the amount of force that can go through the rollers before the rollers slip on the tyres. You would expect the rears to take more force to slip as the Elise has more weight on the back and bigger tyres. 

It would not be measuring brake balance.  As you say, in braking you get weight transfer to the front so you can get much more braking from the front, the rear goes light. The brake bias puts more into the fronts as locked rears is not a nice experience, locked means no grip so the back end moves around. 

Much more important is balance across the axle, you can fail an mot if the difference is too much.

On a seperate but related subject, I have never understood why the 50/50 weight balance prompted by some companies is a good idea.  With the dynamics of weight transfer you want more on the back for a rwd sports orientatec vehicle.

Keith

ps I think you car's balance is fine. 

[russelld]

Thanks Keith,

I'm sure it is fine, I was just very surprised at the figures ( I can't remember exactly what they were but the rears were about 15% higher readings ) the balance across axles was fine within about 5% IIRC

Russ.

 

F1 cars are about 45% / 55% front / rear weight distribution, I would think they would be about optimal. 

Elise 38% / 62 %

Caterham closer to 50% / 50%

[jody391]

Prob those 235 rear tyres buddy