While doing my weekly cleaning of brake dust from my CS wheels I came up with a question.
I cannot find the exact ratio, But the
Cayman
has a pretty near 50/50 weight distribution. If anything, it may be biased to the rear a little, since the engine seems to be placed a little to the rear of center. So, if it has pretty much equal loads on front and rear wheels, why is it that there is always much more brake dust on the front wheels compared to the rear. Is there a built in front brake bias? That is the only logical answer I can think of.
Good question:
Although the CS does have a slight rear weight bias (I'm sure you could find the exact %'s on this site somewhere), the front brakes still do most of the work. This is not due to a brake-bias in the system, but rather due to physics.
Under hard braking a tremendous amount of vehicle weight transfers forward to the front axle. On R-compound
tires
, by CS routinely achieves 1.5g's of deceleration on the track (measured with a Traqmate sampling at 20hz). On street
tires
I bet you can still exceed 1.0g's of decel. So what that means is that the weight over the rear axle (1.0g straight down) is being combined with 1.0 - 1.5g's of braking force (straight forward). I would guess this averages out to about half of the weight that is normally sitting over the rear axle being transferred to the front axle (and therefore the front brakes). So if your static distribution was 40/60% front/rear..... then under 1.0g braking it would be close to 70/30.
If there is an engineer in the room who can correct my math, please do.
Does that answer you question?
Q
Additionally with the front wheels being smaller, there is significantly less space to spread the brake dust around in so the concentration will be higher.
Q's answer is correct. It's all about weight transfer (not wheel size). That's why the front brakes (calipers, rotors & pads) are much bigger than the rears, but still wear out much faster & heat up much more. You've got more brake dust in front because your front brakes are wearing away much faster than the rears.
45/55 per Cayman S product information
You are all right and making good points. I should add that the brakes are bias'd to the front, this for safety. If you have every experienced rear lock-up while turning, some of you have I know, this is not something that street car manufacturers wish on their customers.
The
Cayman
does have 45/55 weight distrbution and larger brakes on the front. Weight transfer will put most of the load on the front as stated earlier.
One interesting thing we are seeing with modern cars is rear brake wear. This is PSM related as the brakes are usused to control balance in the event the car is driven too quickly in a corner. I can know tell if someone is over-driving the car by measuring the rear brake wear as compared to the front.
We are selling more rear brake pads than we used to...
Stan
