Hi Bike friends!
I recently bought a brand new Votec F7 with Mavic Cross Ride rims and the Magura HS-33 brake. The tubes I used so far have standard car-valves. I did some 10 trips so far, not too strong ones although I live in the Alps in Switzerland.
So far I replaced 4 front tubes because of tube movements while braking. At first I checked the valve hole and found that the edge was pretty sharp. I fixed that. Than I changed the tire, no help, too. Finally I took new adhesive rim tape and threw the old plastic band out. A little better now, but still approx. all 50km I need a new tube.
I am biking since 16 years now and with my old bikes (Ok: Cantilever brakes)I never even took a spare tube with me.
What can I do? Mavic couldn't help either.
tried higher pressure?
The only times I've seen excessive valve movement were when tires were run under-inflated. Since you're an experienced rider this likely isn't the cause. But I figured I'd mention it just in case.
hmm... try this...?
the holes in the crossride wheels are schrader, like you said, but you could get away with using presta's... just keep the tires inflated properly after centering the valve in the hole, and you'll be fine...
besides, the presta valve has a metal stem. there's no cutting that.
(and why the crossride's valve holes are schrader, i have no idea. maybe just so you can use both, either presta or schrader.)
what is the problem
Schraeder valve (standard car valves) stems are steel coated in plastic. Are you losing tire pressure after 50km's or is the stem just on an angle. It is very hard to wear through a valve stem with a rim especially if it is aluminum.
i used to own a crossride rear wheel and it came with a small rubber adaptor to size the valve hole down to fit presta valve's. go back to your LBS and see if they can source you a set
BFSSFG old timer
Try dusting the inside of the tire w/ baby powder. It should keep the tube from sticking to the tire.
I would also switch to the presta valves as described above. Pick up the $1 schrader adaptor for a valve cap so you can use any pump that might be handy.