The Kneeslider

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Wilwood Stealth Perimeter Brake System

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Stealth Perimeter Brake System from WilwoodRecently, we had a story about perimeter brake rotors showing up on a number of custom bikes. Although they have a lot of advantages in the area of appearance there is at least some disagreement over whether they work as well as standard rotors but the point is academic since practically no one is making them.

Got a tip yesterday pointing out this Stealth Brake System from Wilwood. I have never seen this before but, judging from the looks of it, I would expect to hear a lot more about it before long. The Stealth System blends into the wheel very well and the caliper hides behind the fork tubes with the end result being an almost invisible front brake.

Stealth Perimeter Brake System from WilwoodIt’s designed to bolt directly to a 41mm Wide Glide front end with stock fender mounts and works with or without a fender. One point I raised in the original story was mounting the rotor of a perimeter brake system requires a wheel with some form of attachment points and Wilwood makes the same statement, custom wheels must be designed to accept their system, however, this gets rid of the problem of no one building wheels for perimeter rotors because the brakes are not available. With a company like Wilwood getting into the market, wheel builders can now produce wheels designed for perimeter rotors and feel confident of demand.

I would be surprised if no one else begins producing these in more varieties since it doesn’t seem like any brake or wheel company would want one company running away with the market.

Great tip Bob, Thanks!

Link: Wilwood Engineering

Comments

  1. I wonder how far away we are from someone going back to their 1985-era ten-speed bicycle and thinking, “Gee, I could just do away with the rotor entirely and use the gigantic heat sink of the wheel itself by mounting a friction surface directly on the rim.”

    I’m not sure if that would cause problems with the tires (extra heat at the bead), but it would probably solve the rotating mass problems of perimeter rotors, at least somewhat.

    cl

  4. Surely it would need extra bracing to stop the forks flexing when you hit the brakes hard. Nice and minimal though. Hiding the brakes probably won’t catch on in sport bikes though, nothing like two wheel sized rotors to let them know you’re serious.

  5. It does look like a fork brace is required. Otherwise the fork legs would try to rotate and the calipers would bind. Actually it looks like they still might do that to some extent.
    -todd

  6. Looks cool, I’ve always though that hidden calipers looked better than ones way out there, and I’m seeing brake rotors built directly into the rim now. Very cool, and if it works it works.

  7. It’ll catch on with the custom guys because it hides the caliper and produces a pleasingly clean look. The custom guys don’t care a deal about absolute brake performance or inertia-induced handling changes.

    I predict that it will never be big news on sports machines. Think about it… where are the highest breaking forces? On F1 cars and MotoGP bikes. Those engineers would already be using the technology if it had merit on a fast vehicle, and they do not.

    Overall it’s a working brake system with neat aesthetics. Good luck to Wilwood.

  8. Could someone please explain how the ‘forks would require bracing with this system” and current twin disc brake systems do not? Are the twisting forces on the fork still relative to the overall braking forces to the ground? Also, Buell has had a perimeter brake system on some of their models for at least a couple years now…. and the parts are readily available.

  9. Hey All;

    360Scott360;

    I think the difference is that on the Buell you still have a rotor being gripped by break pads on both sides of the rotor. On this Wilwood, we seem to have only one pad on each side of the wheel, pinching together, this would indeed cause a lot of strain on the folks, far more in my opinion that a brake rotor being gripped on both sides.

    Basically this is the same as cantilever breaks on a 10 year old 10-speed bike.

    If I am wrong someone please correct me.

  11. 360Scott360;

    …also, on a conventional set-up the caliper and rotor is much closer to the axis of the fork, giving it much less leverage. A Wide Glide front end is fairly wide 😉 and the rotor is mounted near the center of the wheel. There could be upwards of 4x’s more twisting force on the forks.

    Does anyone else think the little 10-32 fender screws might not be up to the task of handling the braking forces? I guess Wilwood did their tests and decided otherwise.

    -todd

  12. forgot to add:

    they are also mounted further from the axel center giving them additional leverage against the forks.

    -todd

  13. I agree Todd;

    I would like to see what happens when these are installed on an 800 lbs HD Fatboy, ridden by a 200 lbs rider at say even 60 miles per hour who has to panic stop. I really doubt that these will be no distortion or damage done.

  14. It’s a double edged sword, they give it extra stopping power but with all the detriments that have already been discussed. And it is just the cantilever braking system, which has been superseded by disc brakes a long, long time ago. In fact cantilevers on a serious downhill mountain bike are considered laughable.

  15. To all;

    I can’t imagine that a very well respected, high performance brake manufacturer like Wilwood would have put this system out there without substantial testing and engineering. They have been around the industry for years. I also can see the hestitation and much of the justification for the arguments here. I think that a Cantilever Brake system IS just a disc brake, the difference between a 10-speed bike brake and this system seems to me to be firstly, that this is a hydraulic-two-sided caliper arrangement versus a cable operated lever, and secondly, that the brake suface appears to be solid where-as a wheel rim on a 10-speed is just formed sheet metal. The whole idea, I thought, was make the brake disc larger in diameter to provide more brake surface, cooling area and of course braking efficency. By the looks of the somewhat small pictures on the Wilwood website, there appears to be a brace between the forks just above the fender. Perhaps this adds to the twisting resistance……? Perhaps not. Personally, I think perimeter brakes can be very effective, much more so than small disc brakes. Is this the ultimate solution, who knows.

  18. This sort of thing would probably work really well on a Hossack fork or the design used on the Yamaha GTS1000. There would be torsional loads, but I don’t think they would be distributed in quite the same way as they might be on a telescopic fork.

  19. Even bicycle cantilevers have additional bracing. From an engineer’s point of view: crap. Will never make it into the EU as well, since it cannot meet safety standards there.

  20. I read all of the comments and concerns. The system will require a fork brace as the system will want deflect the energy outward. But the larger diameter braking surface has some serious stopping power. If you look at the wheel closer you will see that area between the rotor surface and the bead has been cut out. We had this rotor has hot we could get it and I still could put my finger on it without any burning. The systems cools itseld quite quickly. If anybody would like to email me directly I would love to hear from at vtwin@wilwood.com

    Thanks

  21. i agree that this might not do well in the performance bike sector, but the custom/cruiser market will probly go hot for it if the kit isn’t too $$$$.
    as for the tech concerns, anyone who’s used perimeter rotors can vouch for their stopping power and the added centripital force/unsprung weight won’t be much of an issue, as the cruiser/custom bike camp stop using mostly only their rear brakes anyway. remember, some cruisers/customs just forgo front brakes altogether. this at least is a cool alternative.

  22. woops, i meant gyroscopic force instead of centripital in my post above…

    …and as an added note, i personally asked Matt Hoch about the perimeter system he used on his recent “Vinny” custom tribute, and his exact words were “over-braking”, as in almost too much braking power…if that says anything.