Fitting slick tyres to 26" wheels

Hello
I have fitted 32mm slick tyres to my old MTB, (26"x1.3" Conti Sport Contacts) to use as a commuter bike.
I have two questions...

1. The tyres fit fine on the old mtb rims, I'm just wondering if the tyre width is safe on the mtb rim width? The tyres are wider than the rim when inflated by 1-2mm on each side, judging by eye. (the wheels previously had 2.1" tyres)

2. By having lower profile tyres, I now realise the bottom bracket height has dropped. It is around 25.5cm from floor to the bottom of the bottom bracket. Is this safe on the road?

Thanks

1. probably, time will tell. Inflate to near maximum capacity to avoid pinch flats.
   
2. worst that can happen if that you might get more pedal strike, look out for this when cornering, but on geared or SS, that's not usually a problem.
   

Thanks

The tyres roll great, though dont take kindly to sharp bumps, would a narrower rim help the tyre to deform with out getting pinched and absorb sharp bumps?

Measured the BB height more accurately, 27cm floor to centre of BB. I guess thats not TOO bad with 170mm cranks. I do notice it is lower than "normal", so it feels a bit risky, but just need to get used to it I reckon.

The problem is the low volume of the tyres, you have less "suspension travel" when you hit a bump before you bottom out on the rims, so I don't see how narrower rims would help. Like cedywedy said, inflate to as high as possible. For what it's worth, I run Hutchinson Topslick (26" x 1") on one bike and keep them at almost 10 bar. I have only pinch flated twice in three years as a commuter. Pretty harsh ride though, and don't reckon I'd do it if the roads were rougher.

max pressure, avoid the bumps, enjoy the increase in speed

max pressure, avoid the bumps, enjoy the increase in speed

Not to mention the lightning-fast acceleration from the combo of small wheels and narrow tyres. Although it may feel like you are on bare rims when curb-hopping.

The problem is the low volume of the tyres, you have less "suspension travel" when you hit a bump before you bottom out on the rims, so I don't see how narrower rims would help. Like cedywedy said, inflate to as high as possible. For what it's worth, I run Hutchinson Topslick (26" x 1") on one bike and keep them at almost 10 bar. I have only pinch flated twice in three years as a commuter. Pretty harsh ride though, and don't reckon I'd do it if the roads were rougher.

Cheers.

I was under the impression that having a rim almost as wide as the tyre, would be a bad fit, that the tyre would be at more risk from pinch flat - is that avoidable though as you say by inflating to highest poss. pressure?

Tyre recommends 80psi. High enough?

The ride is harsh, as suggested it does feel like bare rims sometimes over a bump or kerb. But it is quick! Just got to get used to avoiding major bumps.

Hello
I have fitted 32mm slick tyres to my old MTB, (26"x1.3" Conti Sport Contacts) to use as a commuter bike.
I have two questions...

1. The tyres fit fine on the old mtb rims, I'm just wondering if the tyre width is safe on the mtb rim width? The tyres are wider than the rim when inflated by 1-2mm on each side, judging by eye. (the wheels previously had 2.1" tyres)

2. By having lower profile tyres, I now realise the bottom bracket height has dropped. It is around 25.5cm from floor to the bottom of the bottom bracket. Is this safe on the road?

Thanks

This premise isn't actually that original. The Cannondale Bad Boy has been specced with Schwalbe Kojak tyres for ages, and is a good example of what you're talking about.

Thanks, good point.

Also I've had a look at other bikes out and about on the bike racks on the street, and see that on racing bikes with narrow rims and tyres the tyre barely protrudes 1mm either side of the rim, so assume that will be ok on mine with its mtb rims and 32mm tyres too.

Cheers.

There is nothing particularly fast about narrow tyres.

You want light tyres that can handle high pressure, but the thinnest possible tyres are not always the best choice.

Tyre recommends 80psi. High enough?

The fatter the tyre the lower pressure you can get away with. You can actually ride stuff like dmr moto's with about 10psi in them. I used to ride mine at about 60-65psi in "transport mode" then drop it to 30psi or less when hitting the trails.

DFP

Thanks for your reply.

I'll ride these tyres till they need changed or I feel like changing them, I appreciate that I may have gone narrow for the sake of it and they were cheap, and get something a bit wider for comfort but light for speed next time.

I guess I'll have to make sure these are at high pressure to prevent pinching them.

if you've got wider rims, them best not to get too skinny tires. I found Vittoria Randoneurs in 1.5" to be a good size on wide mtb rims.

I'm using Specialized Nimbus 1.50 on my trick bike. they have never rolled off or got a pinch flat even though my rims are wide.
If you maintain the stated pressure they should be ok.

just be aware that some mtb rims are not designed to take the high pressures of thinner road slicks.
seen mavic 317 rims destroyed because people think you pan put inch slicks at 90 psi on them. you can but only for so long.

TYou can actually ride stuff like dmr moto's with about 10psi in them.

Is this possible given that atmospheric pressure is 15psi?

How does atmospheric pressure affect the pressure inside the inner tube? When you connect a pump to a flat tube it doesn't automatically read 15psi does it.

the pressure inside an uninflated tube is 1 atmosphere (14.699psi).

Wikipedia has the answer:

Gauge pressure is zero referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure.

Tire pressure and http://en.wikipedia.org/wiki/Sphygmomanometer must be absolute

just be aware that some mtb rims are not designed to take the high pressures of thinner road slicks.
seen mavic 317 rims destroyed because people think you pan put inch slicks at 90 psi on them. you can but only for so long.

Ah, I see. Will be cautious then.... hmmmm.