Tyre size

[oilyrag]

After a bit of advice regarding tyre size. When buying new tyres for my bike(a Specialized Sirrus) about 18 months ago I'm sure they had 700 x 32c on them. The assistant in the shop said he did'nt have that size but sold me two continental tour rides size 28 x 1 3/8 x 1 5/8 with 37-622 alongside of it which have been fine. I'm now in the market for two new tyres, and whilst repairing a puncture yesterday I noticed a sticker inside the rim with the numbers 18-622 on. My question is what size tyre. What would be the ideal, and have I a min & max size to choose from. Please excuse my ignorance as I am more or less new to cycling,

 

[stephec]

What make and model of rims do you have, they will have a manufacturers recommended max and min tyre size?

 

[Tim Hall]

The sticker on the rim means the internal width of the rim is 18mm. The 622 is the "bead seat diameter" in mm, which is the best way of stating tyre size. You'll notice it was also on the tyres you bought. It's the diameter of the tyre where it sits in the wheel. (For obscure historical reasons, 700c tyres have a 622mm bead seat diameter. And they're sometimes called 28 inch too. See why 622 is better?). Anyhoo, looking at the Sainted Sheldon's website, a 17mm internal width rim should be OK with tyres (or tires as he spells it) from 25mm to 37mm. You had 32mm on it when you got it, replaced them with 37mm. Sorry for the rambling answer, the phone kept ringing.

Sheldon's article on tyre sizes is here. Scroll down a bit and you'll find the rim width bit.

 

[oilyrag]

The sticker on the rim means the internal width of the rim is 18mm. The 622 is the "bead seat diameter" in mm, which is the best way of stating tyre size. You'll notice it was also on the tyres you bought. It's the diameter of the tyre where it sits in the wheel. (For obscure historical reasons, 700c tyres have a 622mm bead seat diameter. And they're sometimes called 28 inch too. See why 622 is better?). Anyhoo, looking at the Sainted Sheldon's website, a 17mm internal width rim should be OK with tyres (or tires as he spells it) from 25mm to 37mm. You had 32mm on it when you got it, replaced them with 37mm. Sorry for the rambling answer, the phone kept ringing.

Sheldon's article on tyre sizes is here. Scroll down a bit and you'll find the rim width bit.

Thanks for the information. So if I bought 700 x 28c would they be ok or am I misreading your explanation.

 

[Tim Hall]

Thanks for the information. So if I bought 700 x 28c would they be ok or am I misreading your explanation.

28mm will be OK. What kind of riding are you doing? The smaller section tyres (28mm) will have less cushioning than larger 32mm or 37mm.

 

[oilyrag]

I cycle every day more or less on roads and pavement (naughty I know), and as I mentioned in a earlier post I look upon myself as a plodder. I just go out and follow my nose no set routes, speeds or times just enjoying the freedom and exercise. I thought the smaller 28mm would give me less drag and better rolling resistance, though of course I realise you still have to put the effort in and not looking for a easy way out.

 

[Tim Hall]

28mm sounds ideal. They'll (usually) be capable of taking a higher pressure than 32mm and 37mm, which will mean a smaller contact patch, so (generally speaking) have lower rolling resistance. And as you already point out, the smaller section will have lower drag/wind resistence.

 

[oilyrag]

28mm sounds ideal. They'll (usually) be capable of taking a higher pressure than 32mm and 37mm, which will mean a smaller contact patch, so (generally speaking) have lower rolling resistance. And as you already point out, the smaller section will have lower drag/wind resistence.

Thanks for the advice 28mm it is then.