2 piece rotors: Which would you get and why?
Jul 10, 2008, 06:39 AM
#77
What do those replacements run?
As far as R compounds vs. street tires, I would think that street tires are harder on brakes. You have to slow down more before corner entry and you have to lengthen stopping distances due to lack of traction (more heat).
As far as R compounds vs. street tires, I would think that street tires are harder on brakes. You have to slow down more before corner entry and you have to lengthen stopping distances due to lack of traction (more heat).
Jul 10, 2008, 08:18 AM
#85
If you are on street tires, you have to brake earlier and you have to keep the brakes on longer, both because you can't brake as hard and you need to slow the car down more before turning in.
Putting aside the lower turn-in speeds with street tires, don't you think it puts more wear on your brakes to apply them more gradually and drag them over a longer distance vs. hitting them hard but over a briefer period of time? Which would give more rotor-cracking/fluid-boiling heat build-up time vs. cooling time?
Jul 10, 2008, 08:28 AM
#86
- Andrew
Last edited by GTWORX.com; Jul 10, 2008 at 08:30 AM.
Jul 10, 2008, 10:17 PM
#87
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Although I have no data to back that, just conjecture
and what I've seen on my car. Plus being an engineer.
Jul 11, 2008, 12:28 PM
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Exactly. It's not just the time the pedal is depressed. The higher forces create more heat and destroy rotors quicker than lower forces and slightly longer braking durations. The difference in braking time maybe 1 second or so, the difference in braking force with R-compounds over Street tires is a larger factor.
Although I have no data to back that, just conjecture and what I've seen on my car. Plus being an engineer.
Although I have no data to back that, just conjecture
and what I've seen on my car. Plus being an engineer.Decel horsepower is dissipated in the rotors and pads in the form of heat.
A higher decel rate (by running R-comps etc does 2 things.
More heat into the rotor - and cast iron has poor properties for heat cycling above a certain temperature. Gray iron can absorb and move a lot of heat - it just doesn't like doing it under certain conditions.
Faster temperature rise - cast iron really does not like thermal shock - or large temperature gradients across a section width.
Both conditions lead to cracking.
The cracking failures are completely normal and expected. If you are not cracking them - then you are on a less brake intensive track - or running a pad that won't generate that much heat w/ otu fading - or are not super hard on the brakes.
You may gain soem life by warming up and cooling down better to minimize thermal shock and/or temp gradient.