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Rock strike story- tubed tire food for thought

  • Thread starter Thread starter MAC10
  • Start date Start date
M

MAC10

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I was travelling north of Nakusp BC last weekend. 78 GS1000C with spoked wheels. Ahead of me a car struck-more like nicked- a head size boulder lying in the road. Not unusual for rocks to be on the road on BC mountain highways. What was unusual was that the rock was set to spinning like a top at high rpm and began to erratically skitter across the road and back again. I braked hard, and began a hard counter steer to the right, but the boulder caught my front wheel on the left side. I hate the sound that makes. The bike took it in stride, and stayed controllable.

The rim was bent up about half an inch, and out one inch, with a big scuff mark on the sidewall of the tire. The bead and a small part of the tube was exposed.

It was rideable, and had barely noticeable vibration. The tire was oscillating of track by about three eights of an inch. Had I been running tubeless tires I would have had an instant highway speed flat.

I was able to ride thirty miles to Revelstoke, where there is a tire shop which does bike tires, close to a machine shop who were able to fix the rim to a safe standard to get me home. You want a German machinist like that guy, who apologized for only getting the wheel straight within 10000 of an inch. Only took a four hour stop to get the tire off, the rim straightened, and the lot reassembled. 200 bucks, but cheap at any price.

I was lucky. I have never seen a rock behave like that in thirty years of riding. Had I hit it straight on I wouldn't be writing this. Watch out for spinning boulders!

Additional information one week later: On detailed inspection, I discovered the left center stand foot to be bent, and a small nick in the left side of the rear wheel rim. I will be changing both wheels to be safe.
 
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An alloy rim would've broken and the tire would be flat tube or no tube......
 
Did the machinist say "a tenth" or "ten thousandths"? To machinist, "a tenth" is 0.0001, and "ten thousandths" is 0.01. Everything for machinists less than an inch is measured in thousandths, so "a tenth" is one tenth of a thousandth. (In extremely fine tolerance work, a machinist may shift from thousandths to millionths, but they would always say the millionths part.)

Anyhow, ten thousandths is still darn good for a wheel that you're not setting land speed records with. A tenth on something wheel-sized is pretty much not possible, where unbending is concerned. Fresh (or at least stress-relieved) material and a large ID/OD grinder would be required, to even have a chance.

Glad you had a tube in there. I think I'll be all tubes next time, mostly because my compressor doesn't flow enough to easily seat a tire. This is just one more plus for tubes.
 
OK, I thought all the spoked wheels were steel rims. I would've expected the alloy to break though with an impact like that since alloys tend to be more brittle.
 
To be clear, they were alloy rims, stock spoked wheels. I was surprised to see there were no cracks. The alloy seemed quite malleable. A good thing, as it allowed a repair without the necessity of welding.
 
Keep an eye on that rim. Aluminum does not tolerate an impact well and it can have stress cracks. Steel is more malleable and can usually be bent back.
 
Since we're learning about spoked wheels... Almost all spoked wheels will use a tube, unless specifically designed to not use one. 36 holes in the rim would be hard to seal up without a tube.
 
OK, I thought all the spoked wheels were steel rims. I would've expected the alloy to break though with an impact like that since alloys tend to be more brittle.

I think you're confusing alloy with cast aluminum rims. The alloy wire wheel rims are made from extruded alloy formed into hoops for the rims. Aluminum cast mag style wheels are just that. Cast and don't bend well. The GS1000 had alloy rims while GS750 had cheaper steel rims.

MAC10 where to reside? I'm down in Cranbrook and ridden those roads lots.
 
I think you're confusing alloy with cast aluminum rims. The alloy wire wheel rims are made from extruded alloy formed into hoops for the rims. Aluminum cast mag style wheels are just that. Cast and don't bend well. The GS1000 had alloy rims while GS750 had cheaper steel rims.

Plus those rims require a tube. All old wire wheels do

Only new "retro" wire rims, like BMW and Ducati Sport Classic are tubeless
 
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