Info needed: sizing tire flaps

[Harry Moon]

In selecting new tire flaps for CMP 20 inch wheels, does one select the flap based on the tire size? Ie. 1100 X 20 requires a 1100 X20 flap or should they be based on the rim width? What size then would be required for a 20 inch CMP Rim?

[rob love]

I bought a bunch of surplus ones off ebay a while back, and they are multi size: 10, 11, 12 x 20. I don't think it is a big issue if they are a little wide...too narrow would be an issue. And of course, make sure they are valve on center and re-enforced at the valve area.

[Hanno Spoelstra]

AFAIK, tyre flaps are sized accordingly to the inner and other tyre they are to be used with. So you would be looking for 11.00-20 inner tube to go with an 11.00-20 tyre.

BTW, the rim/wheel size is 6.00x20, so the width of the rim where the bead sits is 6 inches wide. The tyre's size is 11.00-20, whereby the width of the contact area is 11 inches.

[Tony Smith]

Originally Posted by Hanno Spoelstra

AFAIK, tyre flaps are sized accordingly to the inner and other tyre they are to be used with. So you would be looking for 11.00-20 inner tube to go with an 11.00-20 tyre.

BTW, the rim/wheel size is 6.00x20, so the width of the rim where the bead sits is 6 inches wide. The tyre's size is 11.00-20, whereby the width of the contact area is 11 inches.

Section width of the tyre, not the contact area.

One thing to consider when selecting flap by tyre size is that most modern tyre recommendations are for much wider rims than the sizes fitted to CMPs. For example the 16" rims that were fitted with 9.00-16 tyres were 6" wide, but the modern recommendation for 9.00-16s are rims minimum 6.5" or wider. Similarly, 11.00-20 are recommended fitted to 8" wide rims.

Specifying a flap for a 11.00-20 tyre will get you a flap suited to the modern recommended rim size and that might be too wide for the CMP rim. It is probably safer, for clarity, to refer to the rim width you are using when asking for flaps.

[Hanno Spoelstra]

Originally Posted by Tony Smith

Section width of the tyre, not the contact area

Yes. That is what I meant to say. Here’s a drawing with all the proper terminology.