Inboard Rear Disc Brakes - Plausibility

First off guys, not that your insight isn't any good on this forum, and I do want you to prove me wrong on that statement. It's just the question that I'm posing is generally not in the street scene of things. "Inboard Rear Brakes", If their so good, why don't you see them more. I know this question may not be for this site, but I'd like to run them on my Speedster Kit car. If you have insight into these..., Please enlighten me. I know their a high dollar item, so besides cost, what's the down side, you know..., the bad things to using them.

Is their a problem with transmission output stub axle flex and breakage?

With respects to hanging the caliper and disc in close proximity to the transaxle..., does it cause excessive overheating of the trans?

Is cooling a problem for the rotor / caliper itself?


I can see the plus side that mounting the assembly inboard -vs- at the wheel would allow a very light unsprung wheel, although rotational mass would remain close if not the same.

I remember seeing these a lot in the early to mid eighty's on off road racers and a lot of European road race cars. Again, please enlighten me with comments and criticisms.

Thanks, David

Three reasons not to run them on a Speedster kit car, space, time, and money.

The rear frame horns take up too much room and are within an inch or so of the inner CV joints, there's just no real room to fit them in-board, mid point is useless and causes stress, out-board works well.

These cars are mostly either assembled in a factory or at home. The R&D for in-boards would be lengthy and the end use rare. The home builder is usually using a VW Beetle chassis, and kinda wants to get in and drive the thing ASAP.

The cars just don't warrant that kind of mechanical sophistication. The body shell is modeled after a fifty year old design, the aerodynamics are the same as an airplane wing . . . they LIFT. The terminal speed and braking is within the limits of the stock system.The engine output rarely exceeds 200HP, and four wheel drums will stop that just fine for the most part. Front disc kits are plentiful, factory made and cheap, four wheel disc kits are more than reasonable, and will exceed most factory systems on more expensive imports.

No room, no time, no need.

IMHO

Cool question!

TC

In general, in-board discs offer benefits and drawbacks. The biggest benefit you've already mentioned, a significant decrease in wheel weight.

Now for the bad. The inboard brakes can be a pain in the ass to service. Dropping pads is pretty easy. Depending on the setup, the caliper can be pulled with a minimum of hassle. But with many inboard discs, the caliper removal is quite challenging. The rotars often require the entire 3rd member be dropped for removal. On my 1976 Jaguar, I've replace the pads and was very happy to find the previous owner had replaced the rotars ($$$$ due to labor). I was able to tilt the calipers back and remove the pads easily, but any rotar work would be much more involved. The heat from the brakes does not seem to have any significant effect on the 3rd member (bearing in mind, the engine itself is like 6 or 7 feet away).

Cooling could be an issue on a speedster. The engine bays with performance motors are notoriously hot anyway and unlike the jaguar, the engine bay on a speedy would be sharing the cast off heat from the brakes with the air that you are trying to use to cool the engine. And the heat generated by the engine is not going to help your brake performance.

Can you? Yes. Should you? Probably not. angela

I say " if you have the time and money go ahead and waste it" it's good for the economy.
Your car doesn't need it. Cool factor=high, need factor=low