Thought provoker: Weight vs Consumables

Alright guys, I just wanted some opinions.

I am personally of the belief that the heavier the car, the harder that car will be on consumables. This seems to be a simple matter of physics. If you have a 3500lb car moving at 70 mph, to slow that car to zero requires the braking system of that car to act against 3500lbs of mass. More mass = more energy that needs to be dissipated. The job of the brakes are obviously to turn that energy into heat and slow the car down. Every time this happens, the brakes are worn down that much more.

I think most of you probably get that. Does the same thing go for tires? Are heavier cars harder on tires than lighter cars?

It seems like the Miata is super easy on consumables, and some of you may have seen my "2 cars vs 1 car" thread. I am considering switching my E30 325is for an E36 M3, but I believe my current E30 will be much less harsh on consumables, since it weighs a good 400 or so pounds less than the E36. What do you guys think?

I believe you are correct for the most part. But what if a vehicle has larger brakes and other running gear built with the excesses in mind?

Larger brakes (drums, shoes, discs, pads) are more expensive material-for-material I'd imagine.

But to what extent you are correct I'm not sure. I know it's not enough to keep me driving a lighter car than the heavier one I enjoy more...

All you gotta do is compare a Nascar Cup car to just about anything else. As far as I know, a Cup car is the heaviest race car on the planet. They are notoriously tough on everything: tires, brakes, balljoints, etc. Like you mentioned, it's a simple matter of physics. It's just harder to move more weight around.

It's partially true for city gas mileage. The bigger performance cars can't get 25 city mpg. For consumables, it probably isn't of that much importance unless you are autocrossing your car often or do track days too. Maintenance plays a part in tire life and gas mileage. Performance parts will also change the life of consumables, not to mention the driving habits of individuals. Some performance tire compounds work better on light cars vs. heavy cars.

To some extent it's a proportion thing. A heavy car on a wide tire may not be any harder on tires than a light car on narrow tires. Suspension geometry and driving style probably play at least as much of a factor. Having said that, big wheels cost more. Big tires cost more. Big brake parts cost more. Even if the consumable use is the same, the smaller lighter car ends up costing less.

At one extreme end, my ICA kart weighs less than I do, is in its sixth season of racing, and is on its original rotor, hubs, spindles, spindle bearings, and axle bearings.

ICA at East Lansing

ncjay wrote: All you gotta do is compare a Nascar Cup car to just about anything else. As far as I know, a Cup car is the heaviest race car on the planet. They are notoriously tough on everything: tires, brakes, balljoints, etc. Like you mentioned, it's a simple matter of physics. It's just harder to move more weight around.

Another reason that a Miata is easy on consumables is that it's massively underpowered. Put a turbo or a V8 in it and your tire and brake needs to up by a lot.

I eat through rear tires. But I'm somewhat of a stancetard (although I'm fairly sure my car would/will perform admirably on a track). I run a bit of - camber in the rear (not excessive amounts, but certainly more than BMW intended). +1 for suspension geometry having an effect on consumables. And I like nice tires, so that doesn't help. Wait... you mean treadwear ratings go over 300?

How many miles does it take to wear out your rear tires?

My old 2000lb 270HP race car with brakes appropriate for the job would go an entire season on pads and rotors while slowing the car from 145. Tires (Hoosier R6) lasted 2 race weekends and then became HPDE/practice rubber.

My new 2790lb 206HP race car with brakes appropriate for the job tore thru a set of race pads at both axles and front rotors in less than 180 minutes of racing (1 weekend) with less acceleration and lower top speed. I broke the left front strut 88 minutes into a 90 minute race and corded one tire during the last race.

Weight is most certainly the enemy of consumables. Still, I changed to this class for better/more competition and less crazy costs for expensive stuff like HP/TQ and aero. So in my case - I got better racing and less out-of-pocket by gaining nearly half a ton.