erasmus666

My wife has just bought a brand-new 26" wheel bicycle and had the following a couple of times:

As she was riding along the ride felt strange and we found that about 4 inches of the edge of the rear tyre had slipped out of the wheel rim. Fixing it was simple: I simply deflated the tyre sufficiently for me to push the tyre back into the wheel with my fingers and then reinflate. It happened again about an hour later and was fine for the rest of the day. I've been cycling for many years and have never encountered this problem. Has anyone else please?

The bicycle has 26" wheels.

Many thanks

HillRider

There are many "26 inch" size bicycle wheels so a better definition would help. The ISO size should be molded into the tire sidewall and will look something like 559 x 45 meaning a 559 mm diameter rim (aka MTB 26") by a 45 mm wide tire. If it's a newer MTB size wheel it should have a hook bead and should grip the tire securely. If it's a steel "cruiser" rim, it will have straight walls and will not tolerate high pressures without wanting to blow off the tire.

Anyway, there are two possible causes if you have modern hook bead rims. One, and most likely is that a section of the inner tube was trapped between the tire and the metal rim when it was installed. Check very carefully all around the rim to be sure the tube is contained completely within the tire. Another possibility is a slightly oversized tire or a sligtly undersized rim or both. I return ther bike to the dealer for a check if the problem isn't with the tube.

John10568 

If the tire is not a good fit for the rim or maybe it is poor quality, then it won't seat properly causeing the problem that you mention. Also, a tube that is too large can get caught between the base of the tire and the rim, and when inflated can push the tire off the rim. I recommend completely deflating the tire, then unseat it from the rim all around on both side with your fingers, make sure the tube is completely inside the tire, then reinflate. If it continues to do this, I would replace the tire.

Soma Roark

Check the sizes, it may just be slightly off despite "matching" sizes

bjoerges

If it is a totally brand new bike, I doubt there is an issue of incompatible rim/tire combination. If it's a "new to her" bike, it may have had, say, 26" x 1.75 tires. If someone replaced a bad tire with an old cruiser 26" x 1-3/4 tire there will be problems. Although mathematically equal they are not the same.

operator

Is it a brand new 26" bike with STEEL wheels?

Doug64

How much tire pressure?

DLM

It's a brand new bike with low pressure cruiser tires. Either the tube is caught under the bead of the tire or the tire jsut isn't seated right.
Deflate the tire, push the tire toward the center of the rim. If you can see the tube under the edge of the tire, it needs to get tucked up inside the tire before re-inflating. When you pump it up, check around the edge to make sure the tire is evenly inserted into the rim all the way around. If it's poking out in one area, check the opposite area, it may be in a little too far on that side. You may need to play with it a little to get it seated right. But do fix it asap, it could very easily blow out while you're riding if the tire is slipping out like that.