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2 x 24" rims on a Radrunner?

Started by handlebar, July 28, 2022, 11:04:56 AM

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My OEM tubes lost air. Months ago, I I bought a pair of tubes the same size. When I mounted one on the back, I got a pair of pinch holes on one side. I thought I'd pinched it with a pry bar. I'd changed a lot of bicycle and motorcycle tires and never done that before. To avoid doing that again, I've been mounting tires without tools. These Radrunner tires fit loosely enough to do that.

I left the OEM tube in the front and continued to add air. When it began losing air faster, I found that the valve core was loose. I know I'd torqued it. I mounted the tire with an aftermarket tube to get a better valve. At 5 psi, I saw that the bead wasn't quite seated at one spot. I deflated the tire and pumped it slightly. I bounced it around.  Finally, I had to use pry bars to get the tube out from under the bead.

One reason for the problem is that the rim is undersized: that is, a 4.00 tube is the nearest size that's big enough. Now it also seems that the tire bead doesn't fit the rim very well; otherwise, with two  layers of tube between the bead and the rim, it would have been much more obvious that the bead wasn't seated.

Lately, I've ridden a bike with 2 x 26" tires at 50 psi. I was amazed at how much more comfortable they were on the rough pavement around here and how quiet they were. They were also easier to pedal at 15 mph, for example.

I think the efficiency difference may be aerodynamic, like the hydrodynamic comparison between a wide ship and a narrow one. The wide ship has to fight high pressure in front and low pressure in back. With a narrow ship, these areas won't be as wide, and the water can more easily move aside in front and close in behind. Similarly, as a wheel speeds up, it may be fighting more pressure as it squishes air in front and more vacuum as it rises behind. A narrower tire may have an advantage.

In inches, bicycle tires are measured by the outside diameter, which makes my Radrunner tires 23". I've got more than an inch of clearance. A 2x24" tire would be half an inch closer to the fenders. I can get a rim for $25 and a set of spokes for about the same. Why not go for it? In that size, I'd have a choice of tires and tubes.

Radio Runner

You may need to drill out the spoke nipple holes in the 24" rims. The stock holes for 14g spokes are probably to small.


Quote from: Radio Runner on July 29, 2022, 08:43:48 AM
You may need to drill out the spoke nipple holes in the 24" rims. The stock holes for 14g spokes are probably to small.

I hadn't thought of that. The company says they're good for ebikes.
You're right, they don't mention spoke gauge.

I was more concerned about length. Figuring it out for a new rim is supposed to be a problem. After the mistake I made in measuring the OEM spokes, I think I can deal with it.

Online I read that you measure from the threaded tip to the head. I measured 130mm. The ones I got measure 130mm from the threaded tip to the bottom of the bend. They were hard to install because they're too long. The corresponding distance is 125mm on the OEM spokes. I measured 130mm to the head because the 90 degree bends had straightened a bit.

If I knew the thread size, I could get a die, grind the spokes to 125mm, and extend the threads. I guess 130mm will do.

With 30 psi in the OEM tire, bumps can be brutal on my hands. Now I know why motorcycles, and some bicycles, had springs on the front long before they had them on the back. I may replace the font rim first.