Ceramic Brake Rotors on a monster

When the ceramic guys first came out, everyone was really excited, like the Speedog830.

Do you think they would make much of a difference in rotational mass? Their CG is closer to the axle line than, say , the rim of the wheel.

Mags save ( I think) about 5lbs front and 7 lbs rear over the stock cast Marchesisni's, and the difference is quite noticeable not only in acceleration but cornering and suspension compliance over repeat bumps.

Based on physics, what percent "feel" would one notice by switching to ceramic rotors as compared to the switch to forged Mags? None? 25 percent of the mag difference? 50 percent? My S4 can't go fast enouph to notice a difference?

I know there are engineer types out there who have probably calculated this , and I thank you in advance for your input.

Regards,
Rideon




Modified by Rideon at 9:57 AM 5/21/2005

the only noticeable weight loss will be to your wallet!

forged aluminum rims and ductile iron rotors seem like a reasonable combination between cost and weight savings.

Per the BrakeTech website, a CMC rotor is a little over 2 lbs. lighter than an OEM SS rotor.
I assume the weight savings is the same compared to the BrakeTech Ductile Iron rotors. The website doesn't give the weight of the iron rotors, if they were lighter than the OEM rotors I'm confident they would talk about it.

A pair of the CMC rotors will trim 4 lbs. off of a front wheel, which is substantial.

My cast mag front wheel was roughly 3 lbs. lighter than my OEM 5-spoke cast aluminum Marchesini. IIRC, Rideon has forged mags, which are a bit lighter yet.

Likely you would feel the difference in ease of 'turn-in', it won't be as dramatic as the difference with the mag wheels, as the diameter of the rotors is roughly half.

The bike will accelerate and decelerate quicker, first because it is 4 lbs. lighter, and second, due to the reduced rotational inertia. You probably won't be able to feel that, as it would be roughly equivalent to taking a gallon of gas out of the tank.

The ride/suspension quality will improve due to the reduction in unsprung weight.
You should be able to feel that as well.

My rough guess of the 'feel' differences from a set of the CMC rotors (as I'm so woefully short of accurate weight and dimension data that it's not worth calculating anything) compared with the switch to mag wheels:

Straight line acceleration, 5 - 10%
'Turn-In', 25%
Suspension compliance, 100%

The braking 'quality' of the CMC rotors is an issue which I've heard nothing about.
Personally, the OEM SS rotors with the OEM pads were a bit too grabby for my taste.
Too much bite with a light squeeze. For heavier braking, they were just fine.
My BrakeTech iron rotors with Ferodo platinums are nicer, IMO. Initial bite is less, and heavy braking requires a bit firmer squeeze, but a good 2 finger squeeze will still stop the bike very quickly.

Fade resistance? I've heard nothing. Frankly, IMO if you're fading even OEM front brakes on the street, you're riding much too hard.

Weight loss in the wallet will be about par for the course, about 5 franklins per pound.
You can trim weight elsewhere on the bike for less $/lb, but the benefits are less.

Speedo:

Thanks for the input.

Rideon

I'm going to run one on the H1 and drop the left rotor and caliper. As soon as they come out (I'm still waiting for the rotor I ordered) I'll let you know the benefits vs. drawbacks. Should drop about 10lbs off the front end.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by foggy123 &raquo;</TD></TR><TR><TD CLASS="quote">I'm going to run one on the H1 and drop the left rotor and caliper. As soon as they come out (I'm still waiting for the rotor I ordered) I'll let you know the benefits vs. drawbacks. Should drop about 10lbs off the front end. </TD></TR></TABLE>

I was thinking of doing this on the 620. I'll be interested to hear how it turns out, braking power wise and performance wise.

pair of stock "snow-flake" style brembo rotors: 7 lbs 5.0 oz
pair of Brembo FF Iron rotors (reference): 7 lbs 8.8 oz
pair of Braketech Axis rotors: 6 lbs 0.0 oz

to compare any aftermarket rotors with "stock" rotors is kind of misleading because there have been a bunch of different types of brembo rotors offerred on different model/year ducs. if you've got actual weights. post 'em.

and for what it's worth, you CAN feel the difference when you shed pounds off the rims. whether it be by going with lightweight rims or light rotors or both...

my personal suggestion (especially if you're not running a 120+ HP bike), go with marvic piuma rims (lightest/strongest cast magnesium rims i know of) and a single braketech AXIS ductile iron rotor up front with a 4pad brembo caliper and a gold-line master cylinder. while a radial master cylinder will be cream on top, it's just not necessary for the additional $$$.

wheel weights for those interested:
Marchesini cast 5spoke aluminum rims (standard on s4):
Front - 9 lbs 1.5 oz
Rear - 15 lbs 5.0 oz
Sprocket hub - 2 lbs 13.4 oz

Marvic Piuma cast magnesium rims:
Front - 6 lbs 14.0 oz
Rear - 9 lbs 12.0 oz
Sprocket hub - 1 lb 14.5 oz

I saved around 3 lbs over the OEM snowflakes with the 998R rotors and STM full-floating buttons. The buttons, themselves, saved something like 13 ozs. Of course, the 4-pad calipers could weigh more than the goldlines. Didn't weigh them.

I went with a radial master more for feel. The goldline master gave too much intial bite with the 4-pad calipers, narrow-bands rotors and Sintergrip ST pads. So, for me, it was necessary. But I would do it in stages.

Just happened to have my wheels off...

Cast Mag 5-spoke Marchesinis, naked except for wheel bearings and center spacers:
Front - 6 lb 9.6 oz.
Rear - 9 lb. 7.4 oz.

Just slightly lighter than the Marvics.
So, front is 2 lb. 7.9 oz. lighter than OEM 5-spoke aluminum.
Rear is 5 lb. 13.6 oz. lighter.

Jibes well with my previous bathroom scale check of -3 front, -5 rear.