dogunter

I have a set of Alex Race 28 rims that came with a new bike I purchased in August. These are double-walled rims. My first 4 rides resulted in 4 flat tires. This was after a complete spring and summer season without a single flat. I live in the desert southwest where goatheads are a huge problem. As with my previous bike I put Continental Gator Skins with tire liner on the new bike as soon as it arrived. (I sold the Hutchison Nitro tires on Craigslist after not seeing anything positive said about them.)

Myself, I am a 180lb rider, 5'10" tall. Nothing I would consider a stress on the tires. I ride about 150 miles/week.

I checked the tubes of the 3rd and 4th flats after becoming annoyed and found huge holes on the rim-side of the tubes. Looking at the wheels I then discovered that the yellow nylon rim tape that shipped with the wheels was not sufficiently wide enough to cover the spoke holes, holes that had rather sharp edges. Sure enough, the holes in the tubes correlated with the location of these spoke holes.

I removed the yellow nylon tape and put on Velox rim tape that covered the rim from flange-to-flange. I then went all of September and October without a single flat and then at the start of a century ride last weekend my tire was flat. I didn't have time to examine the tube so I set it aside and rode the century. A few days later I went to go for another ride and the tire was flat again. This time I found the hole - again it was on the inside of the rim.

There are no obvious tears in the Velox tape and nothing sharp protruding but I can now feel the spoke hole edges with my fingers - more than when I first put the Velox on.

My question is this: Should I just settle for a new set of wheels since the Alex Race 28s aren't all that great to begin with or is it possible to put on a second layer of the Velox tape? Will I increase the chance of a pressure blow-out or pinch-flat by doubling up on the tape?

Thanks for any advice for this newbie.

-david

bikepro

It is unusual that you are getting flats due to spoke holes when using Velox tape. Yes, it will settle into the spoke holes after some use, but the ridges should not be enough to damage a tube. Are you using very light weight tubes with very high tire pressure? I guess that could cause a problem. If you want to add another layer of Velox, it shouldn't hurt anything, although I've never known this to be necessary. You might have problems mounting your tires since the two layers of Velox will make the rim very shallow.

FBinNY 

Before you embark on a solution, you have to figure out the cause, or at least have a good working theory to test.

If the tape is already covering the holes, and hasn't visibly blown through, I can't see why you'd think that doubling it can do anything. OTOH doubling the tape will increase the rim diameter at the center making tires harder to mount.

In the same vein, unless you can point to something about the wheel that's a problem, replacing it won't magically solve it.

To help me help you diagnose the issue, I have a few questions.

What do the punctures look like, clean pin holes, tears, cuts, or bursts?
Are they always in the same area with respect to the tire or rim (valve), or random?
How wide are the rims (inside width)?
are the tires tight to mount? do you use tools?
Examine the tubes, do the flatted tubes appear to have stretch marks, or blister like, or sagging areas where the tube stretched more, and didn't shrink back all the way?

fietsbob

Did You de burr the edges of all the rim holes above the nipple heads , if a double wall rim.?

3alarmer 

...the deburring process is something to consider. I have painstakingly removed
someone's Velox tape to attempt a solution to repeated, mysterious flats only to
find a few aluminum shavings left over from the manufacturing process had worked
up into the tape and a sharp, small point would punch through under pressure.

You could not see or feel it without removing the tape to examine the underside.

It really helps in this to have used your punctured tube to trace back around the rim
to give you a smaller area to search for the location.

dogunter

Thanks for the ideas so far. Here's the answer to some of the questions.

Of the first 4 flats I only looked at the tubes of #3 and #4 . The punctures were V-shaped, rather large and occurred on the rim side of the tube and at the location of spoke holes, but not the same hole. This was when only the thin yellow nylon rim tape was present, the tape that allowed the edges of most spoke holes to show.

The two most recent flats are not punctures but thin slits in the tube, about 3mm in length and impossible to spot until you hold the tube under water while trying to inflate it. Again, the slits are in the rim-side of the tube and both have occurred at locations corresponding to spoke holes, but not the same hole.

I did not debur the rim holes but that is what I'm going to do next. I'll remove the Velox, debur and put on a fresh tape rather than double up.

Another possibility is that I may be over-inflating the tubes. I've been inflating to 110 pounds. I'm running the Continental Ultra Gatorskins that say I should inflate to 110-120 but perhaps the tubes I've bought cannot handle it.

Also these last two tubes are Kendra brand and the only two Kendras that I've used. The previous tubes were the Novara branded tubes from REI. I have one Kendra tube left that I'll use after deburring the rim just to test this theory out (while take two new Novara tubes on the ride with me.)

dogunter

A quick follow-up to close out this thread. Since sanding the spoke rim hole edges smooth I've done two 54 mile rides with not flats. Hopefully this is the end of the problem.

-david

Kimmo

Did you notice the holes having burrs before you sanded the rims?

If you think about it, it's not the tube's job to withstand pressure, at least above a microscopic scale.

dogunter

No, there wasn't a single burr along any of the holes. Those I would have caught during the first inspection before putting on the Velox. But the edges were rather sharp.

rm -rf

Thin slits sounds like pinch flats, where the tire bottoms out when hitting a pothole, and the tube is mashed between the tire and the edge of the rim. I've had pinch flats that took a while to start leaking air, the pinch just made a weak spot. There can be one or two slits.

But with 110 psi, that's not too likely. It would usually be a bone-jarring hard hit, where you wonder if you broke the rim. But I've hit a sharp edged cast iron water valve and pinch flatted at a fairly slow speed.

(At 180 lbs, try 110 rear and 100 front. It's a smoother ride.)