Technical & Reference Section > Tech and Restoration

What tyres do I need ?

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Michael bmx:
Thanks again for the reply, yes they are 20" with tyres, there where I made the mistake, I thought all 20" wheels where the same size, but they are not lol, a standard 20" wheel seems to be 16" in diameter but my alex rims are 18" but both are 20" with tyres on, so when I brought 20" wheel tyres I was sent a set for the standard instead of the 451 mm type I needed guess im stuck in the 80s/90s lol before mm was used ha ha. All sorted now 👍

brettypeeps:
The tyre size is 20 x 1 3/8.

Spen69:
20" is the maximum OUTSIDE diameter of the tyre once fitted  :coolsmiley:

Narrow 1-1/8"  & 1-3/8" rims use different tyres but are still only 20" max when inflated.

I could be wrong but I think it has something to do with very early racing rules but either way there are two sizes, one is denoted with a fraction in the notation and the other uses a decimal. A standard rim is termed 20x1.75" or 20x1.5" and will fit any tyre from 20x1.5" upwards, seen newschool running 20x2.4" fairly often. The other rim is noted 20x1-1/8" and will run 20x1-1/8" or 20-3/8" tyres :coolsmiley:

Hope that helps - can probably post a few pictures if it's still not clear but for example my kids race bikes have a 1-1/8" narrow rear tyre and slightly wider 1-3/8" front for better grip :daumenhoch:

Oh, and don't forget you will need different size brake caliper - probably 610 size not standard 890/900/1000/1020's - if you're not sure what I mean the measure the centre of the brake spindle hole to the middle of the rim brake surface in mm then add a zero which will give you a number to aim for in the serial size of the caliper :daumenhoch:

Michael bmx:
Thank you so much for the info it is a great help, I have converted to disc breaks but that info will help in the future. Thank you guys

Michael bmx:
I have alex rims and these ankie ones

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