View Single Post
Old 08-04-19, 07:33 PM
  #38  
conspiratemus1
Used to be Conspiratemus
 
Join Date: Jan 2009
Location: Hamilton ON Canada
Posts: 1,512
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 297 Post(s)
Liked 245 Times in 163 Posts
I'd second the motion for an all-aluminum front rim for the mountains.

But there's something else: I went back and re-read your careful description of your Walnut Gap wheel failure. I wonder if your rim just plain broke, unrelated to heat. (You said you felt the front brake pulsing when you started to brake into a corner at speed. It wouldn't have been hot, yet, and wouldn't ever have been hot, given very little braking on earlier descents.) Then, when you decided (wisely of course) to stop and check, you had to bring your speed rapidly down to zero on a steep grade, getting only to 10 mph when the wheel went ka-blooie. This is much more aggressive braking than you would have planned to do before the decision to stop and would have put much more heat power into the rim, a rim that seems already to have been damaged and compromised. While this heat clearly finished off the rim, I find myself doubting that it was heat that started the trouble.

A light (and very strong) tandem couple we toured with a few years ago broke a (rear) low-spoke-count carbon rim "just riding along" on the level on pavement. Maybe they hit a bump badly, -- I don't know, they were always out of sight, far ahead of us! -- but for sure there was no braking heat involved in their mishap. They didn't crash -- the wheel held together but there was a large crack with an angulated step deformity in the rim right through the brake track and bead into the V-shape deep to it, looked superficially in my memory like yours.

Just wondered what you thought of this hypothesis. You were there, I wasn't. If correct, it would tell me that the wheel (because it broke when still cool) failed structurally under your weight and road impact even before you heat-stressed it. If I'm incorrect, it would be consistent with the supposition that the rim was fine for purposes and all we need to do is make sure that we don't over-heat them.

Whatever, we're sticking with our 36- and 40- spoke Velocity Deep V's.
conspiratemus1 is offline