VicM

Am trying to put a bigger tire on my Bianchi Europa. 15 mm i.d. Mavic rims. New Velox rimtape. New tube: Novarra (made by Kenda) 700 by 35/43. New tire: Continental Contact 37-622, (28 by 1 3/8 by 1 5/8) This tire is bigger than Sheldon Brown recommends for a 15mm rim (his chart limits the 15mm rim to 32 mm tire and I'm trying a 37.

When I pumped it up to 80 psi it blew out about one half inch from the Presta valve. The tube seems to have two "lumps" on each side of the valve, one torn open, not in the valve per se, but in the normal thicknessed rubber.

Is the thicker, least flexible base of the valve not compatible with this narrow rim? My only guess is that the valve wasnt all the way up into the rim and the nearby rubber got overstreched beyond its capability? I am not a mechanic and don't sleep at the Holiday Inn.

SweetLou

Most likely, you had the tube between the rim and the tire bead. Make sure the tube is all the way in the tube. If any part of the tube is outside the tire, it will blow with a very loud bang.

VicM

That is not what happened. The tube was 100% inside the tire. The rip in the tire was about .5 inch from the valve on inside (spokeside, right in the middle) of the tube, not on the side. Maybe the tubes are garbage quality and that's why get sold at R.E.I. (Recreational Equipment, Inc).

Al1943

+1
Next time add a small amount of air to the tube before mounting the tire. Before inflating push the valve back into the tire to assure that no part of the tube is caught under the tire bead.
Actually I think you need a smaller tire. I would not go over 28 mm on that rim.

rogerstg

FWIW, your pressure of 80# for a 37mm tire is pretty high and may be part of your problem. It's pressure suitable for about a 350# load on the bike.