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Larger front rotors

Roy
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Roy Grand Master

Roy

Posted
Posted

Had a problem at work the other day, and had a pretty simple fix...then that night was dreaming about my favourite subject :BIG brakes :whackit:

Anyway with problems of work fresh in my mind, i thought about another advantage of running bigger rotors which on paper perhaps makes sense, but have no idea if their is a real world difference.

Im about to buy a new set of 2-pce rotors for my car, and was going to use DBA 5000, Pt No. 5600.1 which are 324 x 30mm thk rotors.

Obviously being 2pce they will be lighter then my current 1pce rotors and should cool better so its all good. So from a thermal perspective im not concerned about having to go bigger.

However if you have a larger rotor then the friction point of the pad onto the disc is going to be further from the disc centre. So that means for the same brake pedal/caliper pistons force exerted on the rotor you will be able to apply more torque to the spinning rotor, giving you superior stopping power/control?!?!?!?!

Imagine you bike wheel spinning, it takes less effort to stop the spinning wheel if you cusp your hands over the tyre as opposed to an inch away from the spline that the wheels spns on. Kinda obvious but i had never considered it before when lookiggn at rotor sized etc etc. :)

So looking at the HSV rotor 343 x 32mm thk, may mean a custom hat...and i will need a custom mount for the caliper anyway? The place im speaking to feels they will be able to get 355mm rotor under the 17" wheel.

So basically if temps isnt a problem, is there any added control, stopping power advantage using a 343/355 rotor.... and is it worth the expense :confused:

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Sydneykid Grand Master

Sydneykid

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Posted

Hi Roy, the leverage effect of larger diameter rotors (even with the same pad dimensions) is quite noticeable. You don't get something for nothing though, you do loose a bit of pedal feel. I am still using standard GTST callipers with standard dimension DBS slotted rotors on ours. The tyres are limiting factor, as to how well it stops, and that's using Yokohama A032R's in the soft compound ie; even after 10 laps I can still lock the wheels with excessive brake application. :)

GTRgeoff Grand Master

GTRgeoff

Posted
Posted

SK, don't say stuff like that......Roy has a massive brake fetish and you're just spoiling it. Make something up, go on, be nice.:rofl:

I'd comment but it would all be theory and would have suggested more feel rather than less, so I'm all ears since my initial instinct were wrong.

From a cycling perspective, since I was a pro cyclist, most good riders only use the front brake and stiffer calipers and NC machined rims have improved feel immeasurably, but the introduction of discs for MTB has been treated like the second coming of Peter Brock. Not comparing apples with apples but it is a massive diameter reduction and swept area reduction. We used to have big probs with melting tyre glue for the "singles" that use glue and pressure to hold them on during long mountain descents. Result was a rolloff from the rim and sudden pain....everywhere.

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