weight of rear rotors?

[dion914-6]

Can someone tell me what the weight of a rear, non-vent 4 bolt rotor is? I don't need exact ounces, pounds is fine.

Thanks for the help,

Dion

[BigD9146gt]

9.5lbs each. Only the factory 9146gt's had vented.

[dion914-6]

Thanks BigD. Some 914-6's have vented like mine, of course they aren't original

Dion

[BigD9146gt]

Dion, may i ask what your doing?

[dion914-6]

Sure. I'm building a Formula First race car based on the existing Formula Vee SCCA class. It uses updated components, essentially bringing the FV into the current world, and that includes disk brakes all around. One option may be to use 914 rear rotors, but we are still playing with the minimum weight rules. Hence the question about weight.

Dion

[BigD9146gt]

Cool project. What are the minimum weight numbers? I might know of a good alternative, and vented....

[dion914-6]

Well, it's still being discussed. The object in this game is to use something readily available, not made of cast iron, but well within everyone's budget. In other words, something anyone can go and buy off the shelf at any VW, or Porsche, supply house.

The rear calipers are either stock 914 fronts or aftermarket replacements for Type 3/Ghia VW's. So vented is not an option, and honestly, not needed at the front or rear. The car only weighs 1150 pounds wet with driver.

Any other ideas? I think there are some two piece designs out there, but they are very light-weight and are cost prohibitive.

Dion

[BigD9146gt]

Hmmm, why wouldn't you want vented? Ok, the car is 1200lbs, so that should make it easier to get going that much faster and need to brake that much harder. Am i thinking overkill? When on a race track your pushing the brakes to the limit. What kind of motor/trans are you going to put into these?

Come to think of it, i would look into Rabbit or GTI parts, those are REALLY cheap. Plus, GTI fronts are like 914 rears, but vented and only 9" in diameter. Plus, you don't have to use (or redrill) the 5 or 4 by 130mm bolt pattern, which doesn;t have all that many rim options (thinking cheap here). By the VW bolt pattern has been around a long time and for a lot more cars... Just a though, Don.

[dion914-6]

Don,

Thanks for the ideas. We are trying to keep the class in the spirit of the original Formula Vees, just with updated technology. The FV class has been a mainstay of SCCA road racing for 40 years, partly because of the rules stability. But that rules stability means it still uses 1200 engines, link pin beams, drum brakes, skinny tires and steering boxes.

The Formula First concept just upgrades to a more modern 1600, balljoint beam, disk brakes and steering racks, along with allowing aftermarket 13x6" wheels with Formula Ford tires. We have to keep this aircooled engines because there is no room for radiators, and stupid things like that... Besides, the rabbit thing has been done before. It was called Supervee.

Braking is not that big of deal with these cars because it is all about momentum. With less than 100 hp on tap, you have to keep the thing moving. With solid disks and the brake setup I described, we can lock up all 4 tires anytime we want. Brake fade is not a problem and we haven't seen any boiling yet.

This thread is starting to move away from 914's, so I apologize to the rest of the board. I've included a link out to the Formula First web page to give you a good idea of what the cars look like, and what some of the ideas are being generated in this concept. I'd also be happy to entertain any comments off-line via email as well.
http://www.formula-first.org/

Thanks for the comments!

Dion

[Dave at Pelican Parts]

Originally posted by dion914-6
... Besides, the rabbit thing has been done before. It was called Supervee....

Before they used Rabbit engines, the Super Vee used the VW Type IV engine. I believe they were de-stroked so that the stock 90mm pistons gave you 1600cc. Some used mechanical fuel injection. Pretty nifty stuff, from what I have read!!

--DD

[dion914-6]

Yep, but they quickly became too stressed and made better grenades than long-term racing engines. I believe they were based on industrial Type IV cases too.

Dion