I installed some of the Vision Warrior wheels on my PM about a year ago. In order to fit them to the PM's axles you need to use 'hub rings', essentially a few millimeter thick shim that adapts these wheels to the PM's axles. Hub rings are, to my understanding, common.
A few weeks ago I was descending the E side of Monarch Pass in Colorado. Often I'll just find the right gear and let the PM idle us down the passes, but on that day, and on that grade, I couldn't find a gear that wouldn't just wind right out. It's a steep road and traffic is hauling. So I ended up using the brakes a lot on the way down.
Toward the bottom, approaching a corner that I needed to be going slower into, I burned down on the brakes to scrub some speed. In so doing the front end of the PM really started to shake and thump and feel, to be blunt, downright terrifying. The symptoms pretty much exactly matched what I know of as 'hot spots', when a rotor is warped and pulses as it passes through the caliper. There were a few more corners left that I had to brake hard for, and on each of these the pulsing/shaking/thumping got progressively worse. If I didn't know better I'd have thought the lug nuts on the wheels were loose. Or gone.
Once things leveled off I pulled over and gave each front wheel a lateral tug, checking to see if something in the suspension was loose or broken. Everything felt solid. After a few minutes, presumably during which things had cooled considerably, we resumed travel. We covered several other passes later that day, and the next, and these symptoms never returned.
When we got back home I stopped by the dealer and had them inspect the brakes, thinking that hot spots are easily remedied. Dealer said the brakes looked pristine, no warping whatsoever. Huh.
So that started me thinking about what the pulsing/shaking/thumping could have been, if not hot spots. And the hub rings are what came to mind, largely because they're made of some sort of nylon.
I went to the tire shop that installed the wheels and tires, and told them what you've just read above. Then asked if it was possible that all of the heat from braking could have softened up the hub rings, maybe distorted them, and allowed the wheels to move elliptically under braking once things were really hot. Both techs I talked to said that yeah, sure that could happen. They put the van on a lift and pulled the wheels off to inspect the hub rings, and they also looked pristine.
So I'm kind of at a loss on how to fix this. I know that it's rare -- Monarch is the only pass in CO that's caused this issue to date. But the pulsing/shaking was so violent that I don't want to send my sweetie out on a trip and wonder if she's going to make it back. I want to solve this, on general principal if for no other reason.
If it's not brakes, and not the hub rings, and the suspension feels tight, what else could it be?
My gut tells me that even though the hub rings look like new, they are the culprit in that they could soften up to cause these symptoms, then firm back up when cool.
Any thoughts/suggestions appreciated.
A few weeks ago I was descending the E side of Monarch Pass in Colorado. Often I'll just find the right gear and let the PM idle us down the passes, but on that day, and on that grade, I couldn't find a gear that wouldn't just wind right out. It's a steep road and traffic is hauling. So I ended up using the brakes a lot on the way down.
Toward the bottom, approaching a corner that I needed to be going slower into, I burned down on the brakes to scrub some speed. In so doing the front end of the PM really started to shake and thump and feel, to be blunt, downright terrifying. The symptoms pretty much exactly matched what I know of as 'hot spots', when a rotor is warped and pulses as it passes through the caliper. There were a few more corners left that I had to brake hard for, and on each of these the pulsing/shaking/thumping got progressively worse. If I didn't know better I'd have thought the lug nuts on the wheels were loose. Or gone.
Once things leveled off I pulled over and gave each front wheel a lateral tug, checking to see if something in the suspension was loose or broken. Everything felt solid. After a few minutes, presumably during which things had cooled considerably, we resumed travel. We covered several other passes later that day, and the next, and these symptoms never returned.
When we got back home I stopped by the dealer and had them inspect the brakes, thinking that hot spots are easily remedied. Dealer said the brakes looked pristine, no warping whatsoever. Huh.
So that started me thinking about what the pulsing/shaking/thumping could have been, if not hot spots. And the hub rings are what came to mind, largely because they're made of some sort of nylon.
I went to the tire shop that installed the wheels and tires, and told them what you've just read above. Then asked if it was possible that all of the heat from braking could have softened up the hub rings, maybe distorted them, and allowed the wheels to move elliptically under braking once things were really hot. Both techs I talked to said that yeah, sure that could happen. They put the van on a lift and pulled the wheels off to inspect the hub rings, and they also looked pristine.
So I'm kind of at a loss on how to fix this. I know that it's rare -- Monarch is the only pass in CO that's caused this issue to date. But the pulsing/shaking was so violent that I don't want to send my sweetie out on a trip and wonder if she's going to make it back. I want to solve this, on general principal if for no other reason.
If it's not brakes, and not the hub rings, and the suspension feels tight, what else could it be?
My gut tells me that even though the hub rings look like new, they are the culprit in that they could soften up to cause these symptoms, then firm back up when cool.
Any thoughts/suggestions appreciated.