By Jim Langley

This week, I’m sharing a couple of great reader comments about last week’s topic, avoiding and dealing with rim wear. There was so much buzz about the Why Not Lights? article that you might have missed these thoughtful tips that relate to more than just rims.

On the subject of rim wear, “Karlobozic” wrote, “I pump my tires up about 30-50% more than I normally ride when putting a new one on. If the rim doesn't fail at that pressure it is unlikely to fail at the riding pressure. That way you see if the tire will bubble too, which most often happens while the tire is still new.”

Thanks, “Karlo.” I’ve heard of testing tires this way, but only by manufacturers. Several tire company spokesman have told me over the years that tires are tested at twice their maximum pressure rating to ensure they won’t blow off. But, your idea to overinflate to both test the new tire for defects in its construction and also test your rim’s condition is brilliant.

Spotting tire defects

For those that have never encountered a defective new tire, what you’re looking for is anything that makes the tire out-of-round and crooked. First, be certain that the tire is properly seated on the rim, because if it’s not, it won’t run true. Then, spin the wheel and watch the tire pass one point on its revolution. The tire should look the same as it spins. Watch the “tread” (the top of the tire that contacts the road) and the sidewalls.

The most common defect I’ve seen is S bends in the tire. In other words, at that point, the tire is out of alignment to the right side and then it veers out of alignment to the other side. If you ride on a tire with an S in it, every time the S hits the road, the bike will shimmy a little. The more pronounced the S shape, the more you feel it. And, an S in a tire can mean the construction is defective, so you should exchange it for a good tire.

Tip: Do NOT ride on a defective tire to test it or you may not be able to exchange it for a good one under warranty. Because it can be argued that riding on it caused the S and it wasn’t a defect. All it takes is running over a rock or bad rut and it’s possible to damage a perfectly good tire.

Rim inspection

For rims, as we discussed last week, if the rim walls are worn enough they can split from the pressure of the tire pushing against it. So, with “Karlo’s” test, you would inspect the rims just like you did the new tire, looking for changes in the rim all the way around and on both sides.

This would be another good use of the outside caliper I mentioned using. You could take measurements at four points around the wheel and see if they’re the same. If not, you might have a rim that’s about to fail where it’s bulging.

Without an outside caliper, you could use your brake and measure from the pads to the rim in several places on both sides of the wheel. That wouldn’t be as precise a number, but it would at least give you some idea, especially if the rim is bad and bulging.

Comment 2

Roadie “Tal” added to the conversation, “It never ceases to amaze me that so many are intent on riding their tires, rims, components and/or frames to the point of failure. And, not just around the neighborhood!”

I’m guilty of this, so I know Tal speaks the truth. For me, a lot of it is wanting to get my money out of the equipment, which has gotten almost prohibitively expensive. I’m also originally from New England, and we “Yankees” are known to squeeze our pennies.

Also, as a mechanic, I enjoy keeping things going. I patch tires with holes but some remaining tread. I run brake pads down until the wear marks are gone. And I can go five years without replacing cables and housing by maintaining them.

Tip: On many bikes, you can quickly inspect and lubricate cables without tools by 1) creating slack; 2) pulling the end of the housing out of the stop; and 3) sliding the housing up or down to expose the inner cable for inspection and lubing.

But, Tal’s point is valid. Even if you maintain your bike, you can’t be sure that something that looks fine isn’t about to fail or worse, cause an accident. Cables can fail without warning, riding in the rain on too-worn pads can be dangerous, and even something as seemingly benign as a patched tube can let you down at the worst possible moment.

True story: After flatting while riding in Death Valley, I removed the tire and saw that the tube inside had already been patched. And, that the leak was from under the patch! The cause? Heat from the road had melted the patch and/or glue, separating the patch from the tube. I was looking over my shoulder for buzzards while I fixed that flat under the scorching sun.


Jim Langley is RBR's Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He's the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his "cycling aficionado" website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim's streak of consecutive cycling days has reached more than 8,000. Click to read Jim's full bio.

Related Topics Rim Wear Rims Carbon Rims

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