[66xlch]

I've fixed a dozen Sprotor failures. I think the problem usually is b/c the fore and aft tugging on the bolts loosens them, though your's all look tight. It could be there was a strain on the bracket b/c of the anchor. If you adjust the chain w/o loosening and double checking the shimming of the anchor, it'll stress it out.

I even GREEN loctited one once (at a cust.'s request) and it still came loose. I'll never run one myself. Failure rate is ASTRONOMICAL, while conventional brake/sprockets just plain work! No brainer, IMO!

 

[66xlch]

BTW, these are NOT Mickey Rourke's fault!

 

[66xlch]

I believe that using one disc as a sprocket and a rotor causes the bolts to come loose eventually, regardless of installation technique. With a conventional rotor or sprocket the bolts are pushed in one direction only. With sprotors, they get pushed one way for braking and the other way for drive through the sprocket. This is what causes EVERYONE who runs them to have them loosen up.

Now, you can double up on the loctite, chase and clean your threads, do what ever you want and all you've done is push it out further into the future, but it WILL come loose sometime. A standard rotor or sprocket can installed such that it will NEVER come loose, a sprotor cannot, IMO.

 

[66xlch]

re-read the title. Answer so far: YES everyone who's run them!

 

[66xlch]

Engine braking would be about 1/100 the force seen from an actual brake, unless it was a meth head teenager TRYING to break something. Sprotors are like power,power,power, brake, brake, brake, repeat until the bolts come loose. Smart riders know that motors cost more than brake pads, and ride accordingly, anyway. When I "engine brake" it's because I am not going to slow down beyond the bottom of the gear I'm already in, and only need a tiny bit of slowing. I certainly don't haul my bike down from speed by slamming down through the gears!

 

[66xlch]

I've been in this industry a long time (since long before there were sprotors). I'm only saying what I'm saying because I've seen so many cut loose. Hell, just on this thread EVERYONE had the bolts come loose! If you want to equate that to pinion brakes on whatchamacallits, I lack the first hand knowledge to dispute you. What I DO know is that almost every sprotor will loosen at some point. I had one come loose with immaculate clean threads and GREEN loctite! Granted, it was a big motor and a huge back wheel, but it came loose.

I have yet to see one that did NOT come loose at one point or another. If you talk to everyone you see with one, they either have not been run long or they came loose, period. If these things worked well, I'd run one and recommend them. I fixed a dozen of them personally. That alone tells me there's a problem. I haven't even had to replace half that many Crane Hi-4 ignitions, and they have been out twice as long and I've installed a hundred of them (vs maybe 6 sprotors)! I speak from experience.


If you must run one, I'd recommend taking the bolts out once every 6 months and cleaning and re-loctiting them. Maybe even more often than that (I know I'd do it if I ran one every thousand miles!) Personally, I warn my customers about the fact that these things loosen bolts and only install them if the customer insists. That is what a responsible mechanic does when faced with this kind of track record. So... NO I will not retract my statements and in fact add to them. Run these things at your own peril!

 

[66xlch]

Besides that,automotive pinion bakes are used in forward 90 percent of the time, AND have totally different mounting hardware schemes. Sprotors are like: power,power,power, brake,brake,brake, repeat until they loosen. They are CONSTANTLY being pushed to and fro by a brutal twin motor that beats up everything it needs to run. A hundred and fifty horsepower jap bike's clutch would be pounded to death in a week behind a 60 horsepower Harley.

Can you tell I'm opinionated and obstinate?

 

[66xlch]

I looked at that. I prussian blued a couple of bolts and installed them they seemed to come out clean, like they hit all the way around, but the machining of the taper seems a bit shady with lots of scored lines around them. Good call, though.

 

[66xlch]

Good question. I checked one by "prussian bluing" the tapers and installing the bolts. They came out clean, but I'm not convinced. The tapers in the actual rotor sure look like they are sloppy. They have a bunch of score lines running radially around the tapers.

Also, if the bolt circle is not 100%, then the tapers will not match up and they will loosen much easier. I couldn't think of a cost effective way to ensure that they were lined up correctly. Maybe a piloted taper cutter that cuts to fit each bolt hole, sequentially? Then, you gotta worry about taper depth, if it's too low the bolts will bottom out. I really don't like the tapered bolt set up in this application, for sure.

 

[66xlch]

Just drill 5 new holes centered between the existing holes and then tap. Back in business!

 

[66xlch]

Majority of those bikes have cushdrives. Also, they surely don't have countersunk bolts in a circular pattern.

 

[66xlch]

BTW, those nord-locks are really cool. I didn't see any for tapers though, but I'm going to get a few and try 'em out, thanks for the link!

 

[66xlch]

The Eixles come with countersunk bolts, but the OP's pic shows button heads, which might be his problem. There's still the fact that MOST of these have come loose, even with the supplied countersunk bolts.

Harley had issues with their front sprocket nuts loosening for quite awhile. They made a series of changes and eventually got them to stay tight. Some designs lend themselves to inherent problems, and clearly the countersunk, radial bolt pattern with continous opposing forces applied is one of those, never mind the heat and lube issues already mentioned. Add it all up and it starts to sound like a really bad idea to run these things.

 

[66xlch]

People, let's try to stick with facts, here.

Older Sportsters (and big twins) ran DRUM brakes with sprockets on them. The drum protected the brake surface from grease. Tapered bolts need a certain degree of precision to ensure contact at the tapers. If so many of these hadn't come loose I'd just say well, it's good enough, but since so many have....

When I was at MMI (20 years ago) they told me to clean ALL brake rotors I come into contact with using alcohol based cleaners to avoid contaminants. I, personally, prefer that to "It'll burn off anyway" from the guy who's getting rich selling them, but maybe that's just me?

Nobodies attacking anyone personally for choosing sprotors. If you feel good about your's, then fine. I just feel strongly about this, because I've seen so many guys get sold these things without a hint of truth involved. Then, when they come apart the customer is shocked! No one should be shocked that a sprotor failed. So many have failed that I am surprised when one works for very long at all!

My motivation is to prevent people from locking up their rear wheels and ending up on the median. At least if I speak up, they will know it's possible. If your motivation is to justify your personal investment in a product, or to help sell a product, then I tend to doubt the veracity of your stance.

Yes sprotors can work to some degree. Yes they might last longer given certain riding styles and conditions. No you cannot install them and have as much faith in them as a conventional brake, PERIOD! I've seen conventional set ups fail (actually only pulleys/sprockets, never rotors), but it's almost always incorrect installation. I've installed sprotors with all the care I can muster and found 'em loose a coupla thousand miles later. I warn anyone who want's these things about the known dangers, because it's my job to.