BRP or now Can-Am recently made a big deal about moving the front discs from the front wheels to the inboard end of shaft at the front differentials. This was to reduce weight on the wheels (unsprung weight) which should improve suspension performance; for improved reliability of discs, calipers, and brake lines; and to better keep brake components clean and up out of mud. Now I see on the new Can-Am Renegade 800 (Can-Ams light weight racing 4WD) that the discs have been moved back out to the wheels. I really thought BRP had a great idea with the inboard front brakes. But inboard brakes would raise center of gravity and might put some small amount of stress on the front wheel drive shafts/joints. I am confused on this change and would like to see BRPs reasons. Seems like what works for racing should also work for normal duty or maybe moving the brakes inboard was not such a great idea after all.

 

I think you may have already stated it, maybe they were trying to lower the center of gravity? Maybe they needed the extra stopping power of two discs since it's made more for racing then utility usage?

 

The closer youcan get the clamping force to the traction surface the greater stopping power you will have as you are taking a lot of material out of the equation. Material that is wheels, bearings nut connections, u-joints, drive shafts, ect. all of thes things move under force and added up will add movement and time from the clamping of the disc to the stopping of the tire. It may not be needed but I am sure every little bit helps.

 

As inboard disks are the standard of braking on independently suspended racing cars, and performance is everything in the racing environment, I'd say that it is more likely that it is cheaper to manufacture the disks on the wheels as opposed to inboard.

 

You nailed it. Having the front bakes at the wheels will give it more stopping power then a inboard. In racing , the front brakes are used the most, and the Renagade will be for racing. So every little bit of stopping power will be needed for that monster.

Glen, it is actually more expensive to put them at the wheels then inboard. If they wanted to stay cheap, they would of kept the Bomb 800 front end and not change a thing. But they needed to make different spindals for the Renagade to hold the calipers and disk. Then longer brake lines and clamps to the a-arms. Being a racer, front brakes are the main way to stop and Can-Am did great. They could of easy just put on sport plastic on a Outty 800 frame and some gas shocks and still ask there price. But they knew what needed to be done and they did it.

 

Whoa! So if you have a long shaft in the lathe, by that theory the lathe motor will have more power against the tool near the chuck than it will near the tailstock!

No, it doesn't matter where the disk is located on the shaft, it will be equally effective.

The energy of the moving vehicle is converted to heat energy by the brakes, via friction. The friction agent doesn't get more efficient the closer along the shaft you locate the disk. It is turning the same speed and resisting the same force no matter where it is. There is no 'lost energy'. Slowing a load of a certain mass a given amount will generate a certain measurable heat energy and that is that!

Else how do you explain ATV back brakes, where there is often a brake drum on one wheel and none on the other, the braking being transmitted by the shaft?
One side is not more efficient in braking than the other or the ATV would slew around when you step on the back brakes alone. [img]i/expressions/face-icon-small-happy.gif[/img]

 

I definetely agree you're going to get more stopping power at the wheels.

1.) The discs are probably bigger, so there is more leverage.

2.) There is twice the pad and rotor surface being applied to the same load.

And yes, the distance between the stopping/starting force and the point where the wheel hits the ground will make a difference. Just think about your lathe this way. Just like using your air gun, you lose a lot of the power with a longer extension.

 

Hey now, who said anything about bigger disks and more pads?
Actually you can have bigger disks and more pads on an inboard disk, because you are not confined for space to what will fit within the inside of the wheel!
But let's not get sidetracked.
Let's don't go changing what we are comparing...

You are saying the same shaft has more power at the driven end than the far end?

That shaft on the lathe would be harder to stop near the chuck than it would be near the tailstock?

 

We are not talking about lathes, we are talking about motor vehicles. I did not say "the same shaft has more power at the driven end than the far end". I said the brake force as close to the tire contact patch as possible is mor efficient.

Thanks for the back up guys, but I feel this hoarse is going to get beat to death.

 

How about this angle? If the front shaft from the inboard disc to the wheel were a solid one piece unit that only rotated without two universal joints to translate then Glen may be correct that disc location is unrelated to stopping force and that makes good sence to me. Now add two moving U-joints that may not be as efficient into equation and maybe now wheel mounted disc will be more predictable and consistant. In any case the suspension will need to work harder with wheel mounted brakes due to increased unsprung wheel weight. I am also puzzled that the Griz 700 now uses dual wheel mounted exposed rear discs while the brand new Big Bear IRS uses single sealed shaft mounted disc. I think the analogy to the single rear drum working OK shows that stopping force is unrelated to distance for a solid axle.