I know that his explanation was... suspect at best. But apart from calling him a liar and getting into a pissing match with him (he's actually a good guy), there's not much I can do. I AM going to insist that he look at the WHOLE front end- pads, forks, calipers, etc. and see if anything else is going on.

 

Increasing the wheel size most certainly requires more physical work from both rotor and caliper when rotor size remains the same. You are increasing the rotational mechanical advantage that the wheel has over the ability of the rotor and caliper to bring the wheel to a stop. The radial speed decreases when wheel size goes up but the amount of force that’s required at the caliper goes up as well.

Think of it in the reverse order of a sprocket and wheel…. increasing the diameter of the sprocket on the wheel, or decreasing the wheel diameter will make it much easier for the engine to accelerate the wheel from a stop. The same power transmission principles apply with respect to wheel size versus rotor size.

The larger you increase the wheel:rotor ratio, the harder the caliper and rotor are going to have to work, which translates into additional frictional heat. Another way to think of it is if you had a rotor that was the same size of the wheel, it would take very little work from the caliper to stop it because the wheel has no mechanical advantage over the size of the rotor.

I’m not in any way suggesting that the larger wheel is what’s causing the problem here, there are plenty of guys running 21’s without complaint. And there are a lot of guys running a single disc with one larger caliper without problems. I’m just stating that by increasing the wheel size, you do increase the demand on the rotor and caliper(s) to some degree. Many may not ever realize the difference, depends on how aggressive you drive. Going from an 18” to a 19” is one thing, but going from a 18” to a 21” is almost a 17% increase in diameter.

 

What you're saying makes perfect sense and I am aware of the physics involved, but it still doesn't answer the underlying question of why this is happening to MY bike when SO many guys are running HUGE diameter wheels these days with what seems to be nary a complaint. I see baggers all the time with 23+" wheels and running ONE DISC.

I know what's going to happen with this: now that the PM's are back on, they're going to warp. I'm going to go to war with PM. They're going to throw the whole thing back on HD. HD's gonna give me the 'ol "well it's not Original Equipment" line and I'll be forced to eat s**t.

Terrific.

 

I am still thinking that the wheel was not set up correctly...Or perhaps it was but installed backwards on the bike.

 

Backwards?

 

Yes...As it is you really don't have any verification that the bearings were installed in the correct order...That sets up the offset of the wheel...Also was the rotation of the tire mounted correctly to correlate with the wheel set up...With a dual disc wheel and the valve stem being in the middle of the wheel...There is the chance that all of the above could be the problem.

 

Basically, what has been said before more or less stands as facts in my case. I've unintentionally warped car brake rotors in the same fashion making a hard stop on the freeway for stopping traffic and then holding the brake on in one spot waiting for things to clear. Braking was hard enough to leave pending skid marks on the roadway. Same happened with stopping my bike once and firmly holding the front brake due to the steep incline I was stopped on. The mech said the pads pressed against the rotor retained the heat while the remaining part of the rotor cooled causing uneven cooling (expansion and contraction). He suggested rather than having them turned, go back out and do a couple of hard stops but do NOT hold the brake on after ward and allow the rotors to cool while driving. Did that, took care of the problem in both cases. Worth a try to save a buck.

 

What I'm not understanding is why I
should have to put this much thought and effort into STOPPING MY F***ING MOTORCYCLE?!?!

 

I've got 34K on my bike. Replaced the original brake pads last week. Also replaced both wheel bearings last week. Took the wheel to the dealer and asked them to remove/replace the bearings instead of buying a $200-$300 puller. I purchased SKF b/c I don't trust Harley's bearings.

1.) I've never experienced any warped rotors. (knock on wood) I try not to brake too hard just as I do in my cages, but obviously stop as hard as I need to. Living in the foothills of the Appalachians my world ain't flat. I almost always will let go of the brake lever to see if the bike will stay still on it's own, but that is rarely the case so the brakes stay on. I'm not totally sold on this idea of why people get warped rotors. My experience says you can stop, leave the brakes on, and be OK.

2.) Someone in this thread mentioned dragging brakes. That you can hear it when spinning the wheel. I swear mine has done this since day one. It's often bothered me but I figured it was somehow the nature of the beast. Bike will roll quite a while with clutch in so never felt it was actual dragging, but some other noise. It's especially noticable when I kill the engine b4 coming to a stop. After getting 34K on brakes and still not being down to metal I'm still having trouble believing they spent a lifetime dragging as they would have died a lot sooner. Thought it might be wheel bearings but I just replaced them and the noise is still there. One thing I am ashamed to admit is that I did not take my calipers apart and lube the slide pins. Harley's directions in the shop manual didn't go into it so I was hesitant. I'll likely go back and do that some day soon.

3.) As far as things being backawards? Well, I guess it's possible it is a directional tire done backwards. Even if it is that shouldn't warp a rotor. Make it handle worse in rain, yes, but warp? My shop manual did say what side the valve stem should be on, so maybe that matters? (btw, mine is in the center). It ain't wheel bearings though. If he has ABS the ABS would HAVE to be on the left. If not the ABS light should be on and the speedo might not even work. If it is not ABS then both bearings are the same part # so you can't get them backwards.

Have you asked PM if they have an opinion on brake pads? Maybe some pad compounds get hotter and warp rotors?

 

I'd be willing to bet it's either a dragging caliper (as someone mentioned), or a caliper/wheel that's misaligned. But again, you'd likely hear it dragging I would imagine. Does the bike seem to track true? If spacers are off a bit, and tire was therefore off in one direction, could be just enough keep the rotors hot enough to be right at that wrong temp just waiting for the chance to **** you off!!