ned512

hello


i would like to know if a 1.25 tire fit my rim it has ertro 559*19c written on it and already running knobby 1.95 tires

also will the difference (on roads) will be significant or it isnt worth it ....



thanks

ThermionicScott 

If that 1.25" tire is smooth and also marked with a 559 bead size (it should say 32-559 somewhere on it), then it will work and probably roll a lot better for you.

FBinNY 

I'm not a fan of ultra narrow tires on wider rims not made for them. This isn't to say they won't fit or hold air, but with a correctly matched tire/rim combination, the tire will assume an Omega profile with the tire widest halfway up, and pinched back at the rim. This provides a nice flex zone and ensures the tire handles as designed. If the rim is too wide, the tie has an inverted U profile, and it's vertical flexing suffers, causing reduced traction on bumpy roads.

My guideline is that the tire width should be one and a half times the rim's inside width or more. There's fudge room so close is OK.

As for rolling efficiency, the narrower tire may roll easier than the wider one depending on tread, but IMO might be too far to the other extreme. Consider a 1.5 or 1.6" wide tire for better balance in handling characteristics.

ThermionicScott 

I think the ETRTO marking for rims is usually (always?) the inner width, so a 32mm tire would be way better for his 19mm rims than the wider ones he has on there. Right?

FBinNY 

Yes, if the rim is actually 19mm inner width, something 32mm or so wide (actual width) would be a great fit. If so, I'm surprised it has 1.9" tires now, since that's well wider than idea, and at or beyond the upper limit for that rim width. (tire/rim relative width chart).

Either way, keep in mind that tire nominal and actual widths aren't always the same.

ned512

thanks for response will the difference between 1.5 and 1.25 be noticable in terms of speed / handling

Bike Gremlin

Your wheels can fit tyres from 28 mm to 62 mm wide - no problems.

Speed and handling mostly depend on tyre quality, type. Fatter tyres for small 559 wheels should be even quicker. I'd go with 1.5.

ned512

Thanks for response but how could fatter tires be faster
Wouldnt thinner tires result low air resistance?

Bike Gremlin

Thin tyres do provide slightly lower resistance, and lower weight. Fatter tyres roll better on imperfect pavement. They will hold your weight with lower pressure, so ride will be less bumpy, wheels will be more robust. The bumpier terain you ride, the faster are thicker tyres. 1.5 to 1.25 is minimal gain in weight and air resistance, but significant increase in air volume.

ned512

thanks for ur response and thanks to everyone responded to my question

noglider 

Actually, all things being equal, the fatter tire has lower rolling resistance.

Bill Kapaun

If all things are equal, your air pressure is higher than it should be in the fatter tire or lower than it should be in the skinny tire.

Why do people always say "if all things are equal", when trying to justify fatter tires?
They aren't!

noglider 

That is exactly the point. You can't make all things equal except in theory. But if your main goal is to lower rolling resistance, going to narrower tires is misguided. In practice, there are tradeoffs, and it is rarely a good idea to get the narrowest or widest tire made.