Wednesday, June 22, 2016

Sweat the Small Stuff


Here, I peel back the ends of the rim 
strip, to photograph how the ends 
were directly over a spoke hole. 
I think it was already in the eighties when I headed up Camp May Road on Sunday morning. I was sweating buckets and went through two 24 oz water bottles of gatorade in a 20 mile ride, albeit part of that involved hauling my fat carcass up to a close to 10% grade.

Interesting thing happened on the way down the hill. My rear tire blew out with a loud pop on one of those many steep curves coming down from the ski area. Made for an interesting way to do a controlled stop from +40 mph.

I took things apart by the proverbial side of the road to put in a new tube and was looking to figure out how the thing blew up. First I thought it was a fatigued valve stem, but no, there was a hole in the inner tube on the inside of the tube where it presses against the rim strip.

Turns out whoever put the wheel together put the ends of the rim strip directly over a spoke hole, with no overlap of the rim strip ends. Over the years the ends separated and the inner tube bulged into the sharpened spoke hole. On the way down it finally failed catastrophically.  Little things matter. Especially if you like high speed descents.

I tried to align the strip over the spoke hole as best I could and got back to the house in limp-home mode. Then I replaced the rim strip and overlapped the ends. I also checked the front wheel, which had a rim strip installed correctly. Thankfully. A front wheel blowout on a high speed descent would not be fun. I probably wouldn't be sitting here comfortably writing this today.

4 comments:

T Gordon said...

Had exactly the same issue, on the same descent, last summer -- only mine was caused by a plastic rim strip that had hardened over time into a semi-sharp edge. interim fix was replacing plastic strip with woven cotton; long-term fix was a new bike with disc brakes and tubeless tires.

FlyingDog said...

On the first road bike I purchased in 2013 I went through 4 flats within the first week of ownership. This was after having ridden a hybrid bike for the previous year and suffering at most 3 flats in that time.

After taking my tires and tubes off I discovered that the thin, plastic rim tape that came with the wheels was not wide enough to cover the spoke wells. I ended up replacing them myself with better tape and also making sure that the overlap didn't occur at a spoke site.

I'm glad your're OK!

My question is, what is the extra heat on such a day doing to the tires on a long decent?

Khal said...

I imagine there is some heating from braking but never did a calculation. Rim definitely heats up.

Olivia Alexander said...

Big thanks to you for sharing such great information.

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