K2 / Proflex Riders Group
General => Tech Forum => Topic started by: spikebender on November 03, 2020, 02:37:18 pm
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Hey Group, hope everyone is well. I have to be honest on this one--- out of ALL the bikes I've had my entire life my 757 is the first one I've used Presta valves for my set up. Problem is now (front only) is the stem pulls away from the tube do I need to double nut the stem? I always have the proper pressure and they were quality tubes. This makes twice any help would be appreciated.
Thanks, Tracy
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The question is what diameter valve are the rims drilled for?
Presta valves are only 6mm dia, whereas Schrader are 8mm.
If you use Presta tubes in a Schrader drilled rim, then yes, you run the risk of the tube bulging up through the hole and ripping the tube especially if you're at all rough with them during vigorous pumping (Phewerrrr!) <GRIN>
If this is the issue then you need a "Schrader Drilled Rim to Presta Valve Reducer Grommet"
https://www.ebay.co.uk/i/264720447429 (https://www.ebay.co.uk/i/264720447429)
Or here's a sexier and elegant solution:
https://www.ebay.co.uk/itm/Bike-Schrader-Presta-Valve-Bicycle-Wheel-Converter-Nut-Rim-Conversion-Nut-W0R2-/293803825967?_trksid=p2385738.m4383.l4275.c10 (https://www.ebay.co.uk/itm/Bike-Schrader-Presta-Valve-Bicycle-Wheel-Converter-Nut-Rim-Conversion-Nut-W0R2-/293803825967?_trksid=p2385738.m4383.l4275.c10)
I use both valves on my bikes, just depends upon the rim.
Col.
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They haven't been drilled out or modified but now that I think about it they are double walled the inside hole may be larger gonna check that out right now.
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Hopefully not modded as that will probably cause a nice sharp edge to cut your tube!
When I say "drilled" I mean "manufactured/designed"
Bottom line is, measure the diameter of the hole.
or, if a Presta valve rattles around in it and a Schrader is a nice snug fit then you need to use Schrader or get an adapter grommet and yes possibly on the inside as well, all in all, best to use the valves the rim is designed for........
Col.
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Problem fixed, the rims I'm using are double walled. The inside hole was a little larger the outer. So I took a presta nut and a Dremel and tapered it then ran that on the stem first and nutted the outer stem.