A self inflicted injury but help please...

[bobloes]

I have had my present bike for about 15 years and I bought it from an American PX when I was serving in Germany. It is an aluminium frame with aluminium wheels. I have changed the tyres and inner tubes a couple of times (as you can imagine) and I now have a bit of a problem with sizes and fit. The only markings on the wheels are that the rear has 19 x 622 engraved on the rim and the front has a sticker marked "SUMO Taiwan Alloy 6061". I am pretty confident that the original tyres were 37-622 (based on my wife's bike which still has the originals and bought at the same time). I fitted some narrower tyres (I am confident they were 700 x 28) a couple of years ago and recently have fitted tyres marked 25-622 and inner tubes marked 700 x 25 - 32C. The inner tubes appear OK but I have to work hard(ish) to fit the tyres whereas the previous tyres could be fitted with hand pressure. Also I have a point on one of the wheels where the tyre has a lower profile above the rim than the rest of the tyre.
So I want a reasonably narrow tyre with the correct inner tube but am now concerned I will continue to get it wrong and waste money buying rubbish. Any guidance or suggestions please? Aah I feel better for getting that out - does it make sense? Cheers all.

 

[tyred]

The 25mm tyres you have are really too narrow for a 19mm rim. Something like a 32mm tyre would suit your rims better.

Have a look at the tyre/rim compatibility chart near the bottom of the page.

 

[bobloes]

I have read the page ( a few times and still cannot pretend I really understand why the tyre width should not be a direct copy of the wheel rim width). I will take the advice however does this mean that I will have big fat tyres with a massive footprint on the road with (probably) a lower pressure hence increasing the rolling resistance?

 

[TheDoctor]

Generally speaking, a tyre should be between 1.5 and 2.5 times as wide as the rim. For a 19mm rim, I'd go for 28mm as an absolute minimum, and 32mm for preference. 32mm is hardly fat, and will still run at about 100 psi. You won't notice the increase in rolling resistance, but you will feel the difference in comfort, and you'll get a lot fewer pinch p**ctures!!

 

[bobloes]

Message received and understood, will comply, thanks both.

 

[Night Train]

Also I have a point on one of the wheels where the tyre has a lower profile above the rim than the rest of the tyre.

Sounds like the tyre bead isn't seated properly there and has been trapped by the tube down in the rim well.
Deflate the tyre and manipulate the tyre at that point to try and pull the tyre bead back up onto the rim seat. A little talc along the bead may help it slide up the well to seat properly as it is being inflated.

 

[Brommyboy]

Some tyres are tighter than others! The flat part can be lifted up with difficulty to fit on the rim shoulders and, given very high pressure for a while, will stretch to fit normally thereafter. The wider the tyre, the easier to mount, so always expect a 25 mm to be much more difficult to mount than a 37 mm!