shameusf

Hi there,
Completely new to the word of cycling. I'm supposed to ride a lot to recover from knee surgery so I've bought a Trek 8500 and am really getting interested in it. Anyway so I know almost nothing, and wa trying to pump up my frot bontrager tubeless when the end of the presta valve just snpped off without any real pressure. Now without the black cap fixed on the end air just gushes out. Is this realy bad? Do I need an entire new wheel? Or can this be fixed? I've got a 50 mile offroad bikeride (race apparently. Quietly confident I'm going to die) on Sunday so need to get it fixed before then. Can I buy just one or are they always in pairs?

HillRider

You only need a new tube ($5 or less) and lessons in how to inflate a presta tube. See any bike shop and have them replace the tube and show you how they are operated.

BTW, they don't usually snip off with no pressure. Either you didn't unscrew the little nut at the end of the stem or you pushed sideways on the stem too hard. They can be broken off if you are too hard on them.

demoncyclist

Even though you don't have tubes, there is a rim strip inside the rim that has the valve stem attached to it. Just go to the bike shop and get a replacement. Have them show you how to properly install the strip and inflate your tires.

HillRider

Whoops, I missed the tubeless part. Yes, the bike shop can replace the valve or fit a tube to replace it.

AFAIK, the field fix for a flat is to always install a tube.

shameusf

Thanks Hillrider. Aren't these tires 'tubeless?

HillRider

There are tubeless bike tires that rely on a seal between the tire's bead and the rim. However, these tires will accept a tube and, as I mentioned, the way flats are normally fixed along the road or trail is to install a tube. The leak is then patched later at home or in the shop and the tubeless form reestablished.

BTW, are you sure your bike really has tubeless tires? I just looked at the Trek web site and the 8500 specs say nothing about tubeless tires and the corresponding wheels. Tubeless tires/wheels are usually very highline specialty items and certainly not what a new rider should be faced with.

waldowales

These are not tubeless tires. Buy a new tube and get the shop you buy it from to show you how to install it and inflate it.

jsharr

A quick google search shows that the Trek 8500 has come with tubless ready tires since 2003. https://www.google.com/search?sourcei...+8500+tubeless

HillRider

Yes, the picture on Trek's web site shows the sidewall marking on the tires as tubeless-ready but I don't think the 8500 comes with the required rims, etc. I believe the bike is actually delivered with regular tubes and valves.