Solid vs. Vented rotors

At what vehicle weight does it become beneficial to have vented rotors on the car? I know it is ALWAYS beneficial, but at some point there has to be diminishing returns in the form of unsprung weight and minimal cooling.

For example, my 79 Civic has solid front rotors and weighs about 1500lbs. When I do the 4x100 conversion on it, I will be able to bolt on the brakes from any 88-00 Civic/CRX, but it will add about 8 pounds per corner from the bigger calipers and rotors. I'm not using sticky rubber on it, but if it can use thinner, solid rotors, I'll be able to use some slightly modified 4-piston bike calipers to get even lighter and still maintain my bias.

A lot depends on brake usage. Hard repeated breaking,ie; track day, the solid rotors will give up very quickly. Vented rotors disipate the heat better. The reduced weight won't help if you can't stop.

Yet for autocross the weight would be a disadvantage

sobe_death wrote: I'll be able to use some slightly modified 4-piston bike calipers to get even lighter and still maintain my bias.

Rock on! Which calipers?

I am sporting the Tokico's from a 2008 GSX-R750 and love them. The sintered pads are very hard on rotors though.

As has been alluded, I would think it depends on your plans for the car.

If you're still around stock weight and power, then an extra 8lbs per corner sounds like a lot at first glance. Then again, I don't know how much the stock brakes suck.

nobody likes fade--are you planning to use all the wheel travel constantly? like offroad? you are trading stop for go and they have to be balanced. if you have the patience, take your version out and test it on the track or in the remote and tweak it accordingly. I can't believe 8 lbs would make that much difference on a 1500 lb car....yes it would. I just added 10 lbs to the rear of my van for bmw brakes, but Im not clipping vortexes with it. it also weighs 3700 lbs.
the solid rotors are common on rear brakes from the factory now as a cost cutting technique. the light cars of the late sixties and on had solids up front, up to 25oo lbs . but that was a cheap upgrade as well. I like venters and a torque engine, which weighs more. your bike calipers sound cool. I always found motorcycle parts overrated and overpriced. good luck and stick withit--it sounds promising

Stock brakes were very marginal back in the day, with captive rotors & a 10mm minimum thickness they were prone to warpage & expensive to repair.

The only car I've had with solid rotors was my geo metro and it did not stop well. I'm not sure if it was the calipers or the rotors, but stopping was barely street adequate.

In reply to mw:

A vented rotor and a solid rotor would be identical until the solid rotor overheated. You wouldn't be overheating solid rotors on the street in a metro. You likely had other issues.

I've road raced a Spridget (1500 #) and A1 rabbit (1750#) - Both with solid rotors front rotors (and rear drums) and never a brake fade problem. Ducting, yes. Proper pads, yes. big azz contact patch (9.5" slicks), yes. Full Boogy, yes (45 minute runoffs race). Fade never an issue.

KJ

With a car that light, I doubt you would need vented rotors.

If it is over 2500 lbs. AND you have more than 200 BHP, AND you compete in the car, vented rotors would be nice. Otherwise fuggedaboutit.

As has been mentioned, vented are superior both for air flow and as a heat sink (they usually have greater mass).

That being said, our Lemons 240z has solid front discs / aluminum drums on the rear and we've run it as much as 24 hours on some pretty demanding tracks with no fade - ducting, race pads (and low HP!) really help

I have Nissin calipers from a CBR F4i. They were free, so my costs include getting custom Carbotech pads made for them.

It's nice to know that autocrossing on solid rotors won't be a problem. It's mostly going to be a daily driver, but even on the stock brakes and 165 width tires I can stop the thing pretty quickly