Thursday, December 2, 2010

Troubleshooting Tips: Leaking Rim Seam

While not as devastating as the Gulf Oil spill, watching air and sealing fluid leak out of a rim is frustrating when you are trying to inflate a tubeless tire for the first time.

My first two tubeless rim conversions went fairly smoothly.    The first was a high end Ritchey Protocol wheelset, and the second was a low end wheelset from Performance.   The third, was not so easy.  They were Vuelta XRP cross rims that came on my Motobecane Cycloscross/Commuter bike.

The problem as that the Vuelta rims were pinned, not welded like the Ritchey and Performance wheels.  In the manufacturing process, rims are extruded from aluminum and rolled into hoops.   Then they are either welded together and machined, or just pinned together.  Pinned rims will have a small gap that will let air through, even with some sealant.

How To Seal A Pinned Rim

You will definitely need some sealant.  I use the Stan's sealant, but I there are others out there as well.    You will almost certainly need a compressor.   To seal my rim, I added about 2 ounces of sealant through the valve with a sealant applicator.  Next, I inflated the rim holding the valve side up and the pinned joint down.   While inflating, I shook the rim vigorously.   During the whole time you will have a fine mist of white sealant exiting the rim at the joint, so you probably want to do this outside.   At first I gave up after about thirty seconds without getting the rim to seal.    Later, I just ran the compressor for a good 3-5 minutes while shaking the rim, and it finally sealed.    In fact, if you have lost a lot of sealant in the process, you may wish to add more for flat protection.

I also happen to have a 4 horsepower compressor with an 11 gallon tank, so I am able to continuously pump a lot of through my rims.    I am not sure you could do this kind of tough seal with a smaller compressor.    If your compressor is not up to the task, try visiting an auto repair shop, as they have some serious compressors.

You Only Have To Seal It Once

The good news is that once the rim seals up the first time, it will be much easier the second time.   Once sealed, it held air for weeks, just as good as my other rims.    Even after changing my tires to tubeless cyclocross tires and back to Hutchinson  Intensives, I was able to inflate them with the same ease I expect from my welded rims.

So don't give up when it comes to sealing a pinned rim.   Keep in mind you may have to run air through the rim continuously for a few minutes while shaking and sacrificing some fluid in the process.

Think of the new white spot on your back porch as a badge of honor.

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