Rear brake pad friction coefficient

[rj]

7 wonders,

Absolutely right.

Also smaller pads will be more likely to overheat.

Mike Biddle,

Having a dual master cylinder is in my thoughts but not road legal here. Don't know if it is in the UK. Add that I have very limited space as I have a hydraulic clutch and not the least that I don't fancy cutting my pedal box.

[Ivaan]

With dual master cylinders, the brake peddle effort required will double to get the same breaking pressure. Unless you go for a lot smaller mc diameters.

[Ivaan]

With dual master cylinders, the brake peddle effort required will double to get the same breaking pressure. Unless you go for a lot smaller mc diameters.

[rj]

Ivaan

I doubt so. Again area versus force. Whether the pistons of the master cylinder are behind or beside each other does not matter for the area. 

[Richard Price]

RJ, Clive (Ivaan) definitely did experience that significantly greater pedal pressure was required. He went from having one 5/8" master cylinder, to having two 5/8" master cylinders, whilst retaining the same pedal geometry (it was not practical to change the geometry as significantly as I would have liked on Clive's car with the early, open pedalbox using the cast master cylinder mount). Therefore, for the same pedal pressure, there was half the hydraulic pressure. Clive a case was extreme. His car is VERY light at the front, with its R1 engine/box mounted well back in the chassis, and drum brakes on its live axle. The brake balance was shockingly bad! He could lock the fronts easily, but the rears were hardly doing anything. Once it had dual master cylinders, it would actually stop, but it required a lot of pedal pressure to actually stop!

[Wrightpayne]

After a slow start this has turned into a really interesting topic.

RJ - you put me to shame with your second language skills! BTW its whether not wether. Wether means something entirely different!

Ian

 

[rj]

Ian,

Thanks. Some expressions I never get right. Whether it's rainy weather or not is one of them When then something from the the Welsh fields gets into the equation it gets really confusing.

Likewise when you say "How long have you lived in xxx for?" rather than the Scandinavian "For how long have you" - I have to focus a lot to get it right.

Richard,

If it was a single circuit master driving both fronts and rears it makes sense as the area of the pistons in the MCs was then doubled when adding the second unit and the balance bar.

Otherwise, if it was a tandem unit, I can only explain it with something adding a spring-like effect to the (presumably) rear circuit. If there was IE an air lock the fronts would lock up before there was a decent pressure built up in the rear line.

Edited for typo - how ironic is that!

[Mike Biddle]

I believe that dual master cylinders are legal in UK, but you are not supposed to have a means of adjusting the balance from the driving seat, I will be looking for an MOT soon in order to register the 7 in UK so I guess I will find out then, because that's what I have.

Pedal effort and travel is dependent on the relative surface area between master cylinder and brake cylinder/s pistons. If you have a master cylinder with a large piston surface area relative to brake caliper piston/s then you will have a short pedal travel but high pedal effort, and if its the other way round then you will have less pedal effort with a longer pedal travel. The second scenario offers more sensitive control over braking effort, the first can feel quite "wooden" in action. you can look at in the same way as a gear ratio.