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Front wheel issue

My front wheel/brake has given me problems since buying my P-38. It is a Sun 406 wheel. When I apply braking, I get a thump thump. I felt the rim to see if there was something there, but no. I changed the wheel from another bike and it went away, so it must be the wheel and not the brake.

Any ideas?


Hi Gary,

Sometimes a very small bulge in the rim surface - so small it is hard to feel - can cause thumping when you apply your brakes. The most likely culprit is the spot where the two ends of the rim are joined together, under the "Sun" label.

You could take some coarse-grit sandpaper and grind away around the join area. It might help. I have some wheels that do the same thing. It can be annoying.

Safe riding,
Joel Dickman

I ended up buying a 2nd front wheel, and I had a Primo tire put on it. I had the 2nd wheel develop the same thing, but not as bad.

Then, I put the Sun wheel back on, cause I wanted to go back to the Schwalbe tire that was on it, and it didn't seem to do it anymore. I had cleaned it thoroughly before putting it back on.

My theory is that my sports drink bottle leaked some liquid on to the bike frame, and it dripped onto the wheel. And eventually caused pulsing when braking. My bottle bracket is mounted on the stem, and is above the wheel.

I now drink water only, and no more pulsing wheel. YMMV. And I have a spare front wheel and tire. :)

Waterloo, IA
F-40 since 2001.
Vison R-84 tandem since 2000.
WizWheelz Sport, flaming orange, since 2007. Plus a few DFs, Mtn, & 1960s classics.


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