Shaving rotors to decrease rotation inertia...good idea? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

DamnedButDetermined · 03-03-2003, 04:59 PM

I know during a hardcore racing weekend or an actual sprint race, this would be a bad idea, but what about an autoX

Here is what i am thinking...
lightened flywheel/driveshaft/wheels/ect... will increase the powertrains efficiency, so wouldn't shaving the rotors down to a safe thinner thickness, therefore making them lighter? I know it wouldn't take off much weight (i would estimate maybe a pound off each wheel) but in an extremely competative class wouldn't any advantage help?

Here are my questions...
How much weight will be shaved off, while keeping the rotors at a safe thickness?
Would this adversly effect the cooling potential of the rotors, or would it make them cool faster?
Has anyone seen carbon fiber brake rotors for sale? I know indy cars and some sportcars use them...(i read it in "Drive To Win")
During a ITA sprint race...Do you need to replace the rotors every race, b/c of chemical reasons, or because the rotors get used all the way down to the safe thickness? Oh by chemical reasons, i mean it like with R rated tires...they get to that magical sticky point then even though they still have tread left they just won't grip as much as they did.

-DbD-

thelinja · 03-03-2003, 07:57 PM

It doesn't sound like a bright idea to me. Shaving a pound off each rotor is a substantial amount. And plus you would have to shave the rotor so that it is still perfectly smooth, if the rotor is not smooth, braking will not be consistent and the car will shake a lot when you are stopping. I'm not sure if it would cool quicker. I'm going to guess that it would cool faster simply because there is less volume to cool. Carbon composite brake rotors would also probably cost you an arm and a leg. I'm not familiar with ITA rules so maybe someone else can help you out on that. Personally I don't think 4 pounds is that big of a deal. Especially for autocross. Just my .02.

AKADriver · 03-03-2003, 10:14 PM

On the same token that it'd cool faster, though, it'd overheat faster because of the reduced weight.

Brake heat isn't really a big deal in autocrossing, though.

The #1 drawback I can see is that you'd be replacing rotors all the time. Rotors already don't last long in autocross use, running them at bare minimum thickness at all times would mean replacing them almost every event. Not economical for a minor weight savings.

hurleyboi514 · 03-04-2003, 08:47 AM

yah, and carbon brake rotors are easily over a grand a piece im sure, and they probably dont make them for our cars... some shop in japan probably does though for larger brakes (ie. skyline, Z32 brakes).

*sykikchimp* · 03-04-2003, 12:22 PM

I think of CF rotors on the same plane as something like an Enzo Ferrari.

I think you would be better off just getting lighter smaller wheels.

240racer · 03-05-2003, 05:50 PM

Since the Enzo has Carbon brake rotors, you are probably correct. Also, they are not carbon fiber, they don't have fibers and they don't have a resin to hold the fibers. They are made like diamonds, lots of carbon, lots of pressure, lots of heat and lots of time. It takes about 6mos to make a carbon rotor, last I heard on one of the F1 interviews.

I would be amazed if somebody made a bolt on kit for much of anything with carbon rotors.

As far as an autocross car, you would not save 1lb per wheel by turning the rotors down to min thickness. Also, you will lose braking capacity, since the rotors aren't able to absorb as much heat as they were before.

Now if you were going to look at the difference between the 26mm and 30mm 300zx rotors, then you might have a point. If your car isn't really fast (stock) and you aren't racing at a super speedway then you will probably be better off with the 26m rotors. BTW, does anybody know the weight diff between the two, I am considering running the 26's for weight reasons

ruf · 03-07-2003, 02:12 PM

Good luck getting carbon brakes up to temp on an autox track.

03-04-2003, 08:47 AM	#4
hurleyboi514 Zilvia Addict Join Date: Mar 2002 Location: The Fort Posts: 905 Trader Rating: (0) Feedback Score: 0 reviews	yah, and carbon brake rotors are easily over a grand a piece im sure, and they probably dont make them for our cars... some shop in japan probably does though for larger brakes (ie. skyline, Z32 brakes). __________________ HighTach Motorsports

03-04-2003, 12:22 PM	#5
sykikchimp WOW addicted Join Date: Dec 2001 Location: the moon Age: 43 Posts: 6,525 Trader Rating: (0) Feedback Score: 0 reviews	I think of CF rotors on the same plane as something like an Enzo Ferrari. I think you would be better off just getting lighter smaller wheels. __________________

03-05-2003, 05:50 PM	#6
240racer Zilvia Junkie Join Date: Nov 2001 Location: Minneapolis, MN Age: 45 Posts: 574 Trader Rating: (0) Feedback Score: 0 reviews	Since the Enzo has Carbon brake rotors, you are probably correct. Also, they are not carbon fiber, they don't have fibers and they don't have a resin to hold the fibers. They are made like diamonds, lots of carbon, lots of pressure, lots of heat and lots of time. It takes about 6mos to make a carbon rotor, last I heard on one of the F1 interviews. I would be amazed if somebody made a bolt on kit for much of anything with carbon rotors. As far as an autocross car, you would not save 1lb per wheel by turning the rotors down to min thickness. Also, you will lose braking capacity, since the rotors aren't able to absorb as much heat as they were before. Now if you were going to look at the difference between the 26mm and 30mm 300zx rotors, then you might have a point. If your car isn't really fast (stock) and you aren't racing at a super speedway then you will probably be better off with the 26m rotors. BTW, does anybody know the weight diff between the two, I am considering running the 26's for weight reasons __________________ Adam '89 coupe KA24DE+T 14.1 @ 104 MPH '88 Celica All-Trac turbo stock, but no more ecu codes!!

03-03-2003, 04:59 PM	#1
DamnedButDetermined Zilvia Addict Join Date: Oct 2002 Location: Jax, Fl Age: 42 Posts: 637 Trader Rating: (1) Feedback Score: 1 reviews	Shaving rotors to decrease rotation inertia...good idea? I know during a hardcore racing weekend or an actual sprint race, this would be a bad idea, but what about an autoX Here is what i am thinking... lightened flywheel/driveshaft/wheels/ect... will increase the powertrains efficiency, so wouldn't shaving the rotors down to a safe thinner thickness, therefore making them lighter? I know it wouldn't take off much weight (i would estimate maybe a pound off each wheel) but in an extremely competative class wouldn't any advantage help? Here are my questions... How much weight will be shaved off, while keeping the rotors at a safe thickness? Would this adversly effect the cooling potential of the rotors, or would it make them cool faster? Has anyone seen carbon fiber brake rotors for sale? I know indy cars and some sportcars use them...(i read it in "Drive To Win") During a ITA sprint race...Do you need to replace the rotors every race, b/c of chemical reasons, or because the rotors get used all the way down to the safe thickness? Oh by chemical reasons, i mean it like with R rated tires...they get to that magical sticky point then even though they still have tread left they just won't grip as much as they did. -DbD-

03-03-2003, 07:57 PM	#2
thelinja Zilvia FREAK! Join Date: Jul 2002 Location: New Jersey Posts: 1,466 Trader Rating: (3) Rides Gallery: thelinja Feedback Score: 3 reviews	It doesn't sound like a bright idea to me. Shaving a pound off each rotor is a substantial amount. And plus you would have to shave the rotor so that it is still perfectly smooth, if the rotor is not smooth, braking will not be consistent and the car will shake a lot when you are stopping. I'm not sure if it would cool quicker. I'm going to guess that it would cool faster simply because there is less volume to cool. Carbon composite brake rotors would also probably cost you an arm and a leg. I'm not familiar with ITA rules so maybe someone else can help you out on that. Personally I don't think 4 pounds is that big of a deal. Especially for autocross. Just my .02.

03-03-2003, 10:14 PM	#3
AKADriver Post Whore! Join Date: May 2002 Location: Springfield, VA Age: 42 Posts: 3,475 Trader Rating: (1) Feedback Score: 1 reviews	On the same token that it'd cool faster, though, it'd overheat faster because of the reduced weight. Brake heat isn't really a big deal in autocrossing, though. The #1 drawback I can see is that you'd be replacing rotors all the time. Rotors already don't last long in autocross use, running them at bare minimum thickness at all times would mean replacing them almost every event. Not economical for a minor weight savings.

03-07-2003, 02:12 PM	#7
ruf Zilvia FREAK! Join Date: Jul 2002 Location: Reflex Racing, Los Angeles,TX Posts: 1,160 Trader Rating: (0) Feedback Score: 0 reviews	Good luck getting carbon brakes up to temp on an autox track.