Bicycle Mechanics - Mountain bike tyre question

Hi there

This is probably very basic. I have a mountain bike. The try keeps going down. I bought an inner tube but I am unsure if is the correct size.

Its 26" which is correct but the width is 2.25mm - on my current tyre I beive it says 1.9. I am confused if I have the right inner and I am reluctant to start trying to take the back wheel off without the right one.

Can someone advise?

Thanks a lot

Don't worry one bit, that inner tube shold be OK. Usually inner tubes are very careless about the size of tire they are put in.

However, I am pretty sure your tire or inner tube width is not 2.25 mm but 2.25" (inches).

I believe that the size on the tire is 26X2.25" not MM. Tubes come in a size form 1.9" to 2.25" this size tube will work. Make sure you run the insideof the tire with your hand to finde any object that caused the flat. Also check the rim strip tomake sure ALL the spoke niples are covered.

Hi there

This is probably very basic. I have a mountain bike. The try keeps going down.

You might have a piece of glass or other sharp detritus lodged in your tire. Make a note/mark the position of the tire vs. tube, while you are removing it, and find the hole on the tube. That will tell you where in the tire is the sharp object located.

If you can't see the hole in the tube, inflate it a bit and put it uner water, and then see where the bubbles come out of it. If you see no bubbles at first, grope and squeaze it, until you notice bubbles.

Hi thanks a lot for the advice. Yes I am sure you are right about the mm that is my mistake.

The only other thing I am cocerned about with repalcing hte tyre on the back wheel is the gears. Currently the gears do sometimes change on their own. Do I need to be concerened with this when changing the tyre

Hi thanks a lot for the advice. Yes I am sure you are right about the mm that is my mistake.

The only other thing I am cocerned about with repalcing hte tyre on the back wheel is the gears. Currently the gears do sometimes change on their own. Do I need to be concerened with this when changing the tyre

You won't do anything bad or anything good to the quality of the shifting.

Read this very nice article
http://www.utahmountainbiking.com/fix/flattire.htm

To remove the rear tire, shift the rear deraileur until the chain is in the smallest ring of your cassette (highest-numbered gear). Turn the bike upside down, then open the quick-release lever. Pull the wheel forward off the chain, moving the opposite side of the chain out of the way as the tire comes up.

That's the only thing, as far as gears, that you have to take care of.