May 18, 2002 8:29 AM
I recently switched the tires on my '94 bridgestone rb2 to Continental GP 3000s, and overall I really like the tire. However, I've had 2 blowouts on 4 rides. Both have occurred when I was on the brakes pretty hard and hit small rocks with my front tire. The result is that the inner tube blows out at the seam.
Is it possible that I'm not mounting the tires properly? Or are there stronger inner tubes? Or am I just too big for a tire like this (6'4", 220 lbs)?
Any help would be much appreciated.
May 18, 2002 9:02 AM
|What size tire are you using? Yea your too heavy for 700x21, which Continental's 700x23 really measure.|
May 18, 2002 3:40 PM
|Yes, I think Conti's run small. Try 25mm's at 120 psi. Make sure the inside of the rim is clean, too.
It should not be the tube's fault. Any tube will blow if the tire and rim do not contain it, and the bead comes off the rim.
May 18, 2002 7:59 PM
|Hey, Bigeasy, kevlar beaded tires, pumped up to 120psi, can very easily blow off a rim under the circumstances you describe, if the bead isn't even around the rim. That's really the only way a blowout will happen. A large cut from road debris just flats the tire.
Rims and tires are designed to fit snugly, for liability reasons. One can have faith in any 700C tire on any 700C rim. Spin the wheel in your hands and sight along the bead to see if it's even. If there's a raised bead, the inner tube is very likely wedged into the crack. Pump it way up, and it'll blow there.
Wire beads are easier to mount, and they never blow, and they're cheaper. What more could you ask for? Oh, yeah, they're a few grams heavier than kevlar beads. Big deal.
|Make sure your not pinching the tube under the tire.(NM)||James|
May 18, 2002 11:02 PM
|Was it really a blowout?||Kerry|
May 19, 2002 6:19 AM
|In other words, a loud bang? A blowout comes from one of two things. Cause 1 (by far the most common): the tire unseats from the rim, caused by a poor mounting job, a defective tire, or a defective rim (bent along the bead). Cause 2: the tire is cut and the tube blows through it. In neither case could a "stronger" tube have helped the situation - there's way too much pressure. With a cut tire, you couldn't use the tire again, so we assume that was not your problem.
As noted in another post, check that the tire is properly seated on the rim by watching the casing as you slowly spin the tire. It should be dead level all the way around. 120 psi in a Cont GP3000 should not be a problem in blowing the tire off the rim. At your weight, you should certainly consider 25 or 28mm tires.
Finally, if you're telling us that you had flat tires (not blowouts) due to hitting rocks while a large percentage of your weight was shifted to the front tire, then maybe you are not putting enough pressure in your tires. You might also consider how you get into the situation of hard braking in loose gravel - a condition not good for any tire and quite possibly not good for you. To have a tube fail along the seam due to impact suggests a severe situation. If this was actually just a "fast flat" (no BANG) then you might consider the tubes you're using. Sometims there are tubes that have weak seams. Go with a brand name tube like Conti or Michelin.