28 equals 29 in the crazy world of tyre sizes

[Tim1023]

OK, so a bunch of you will say "Duh...yeah!", but until yesterday, I lived in a world of tyre size innocence.

I've had a really frustrating time trying to find a commuting tyre for my 29" Levo, saw several recommendations, then tried to buy them online only to find that they were all only available in 28", so I passed on them. Most of the recommendations were Schwalbe and it turns out that for their road / touring tyres, they call the size 28" and for the same wheel size for MTB tyres, they call it 29". And they fit the same sized wheels!

Who knew? (don't answer that).

I gather it has something to do with the outer diameter. The tyre / rim width is also important, i.e. you can't fit a racing tyre to an MTB rim. Obviously.

The topic has been covered before (@Gary, obv) if you know to look for it, but I thought I'd just post on it again so that it floats to the top of the list for anyone currently looking for commuting tyres.

 

[Tim1023]

Forgot to include this from Schwalbe: What is actually the difference between 28 and 29 inches?

Just so that you have it officially from the manufacturer

 

[slippery pete]

The idea that the outside diameter of a bag of gas is the important number rather than the precision interface between bead and rim. The bike industry is at its worst when it perpetuates this nonsense.

Admittedly the industry has also tried to rationalise with the catchy ETRTO measurement, but the knuckleheads in marketing have decided that is too engineery. The engineers rebel by molding it in black on black on the sidewalls that nobody ever looks at to the sole purpose of leaving evidence for future archaeologists of a visiting space alien species that the human race really wasn't going to get it together.

Metal thing of certain size. Bag of gas attaches to it at precision interface. Bag of gas comes in different "fatnesses". Why is this difficult?

700c? 650b? the b and c refer to the tyre fatness but the 700 and 650 refer to a nominal outside diameter of a bag of gas. If you compare 650, 650a, 650b and 650c, they refer to four different rim diameters.

The ETRTO of 700c is 622, just like 29er mountain bikes and 28" hybrids - WTAF?. And just for shits and giggles 700mm in inches is 27.5. Whereas the 650b standard (AKA 27.5 or 27) is an ETRTO of 584. The 'b' was based around a 1.5" tyre for touring bikes which seldom has anything to do with the tyre size a self-respecting MTBer fits to such wheels.

The whole lot of 'em should be up against the wall when the revolution comes.

 

[slippery pete]

Or the incomparable Sheldon Brown: Tire Sizing Systems

 

[Sidepod]

Can't help feeling we need to strap in for some imminent Gary-ness

 

[Sidepod]

The idea that the outside diameter of a bag of gas is the important number rather than the precision interface between bead and rim. The bike industry is at its worst when it perpetuates this nonsense.

Admittedly the industry has also tried to rationalise with the catchy ETRTO measurement, but the knuckleheads in marketing have decided that is too engineery. The engineers rebel by molding it in black on black on the sidewalls that nobody ever looks at to the sole purpose of leaving evidence for future archaeologists of a visiting space alien species that the human race really wasn't going to get it together.

Metal thing of certain size. Bag of gas attaches to it at precision interface. Bag of gas comes in different "fatnesses". Why is this difficult?

700c? 650b? the b and c refer to the tyre fatness but the 700 and 650 refer to a nominal outside diameter of a bag of gas. If you compare 650, 650a, 650b and 650c, they refer to four different rim diameters.

The ETRTO of 700c is 622, just like 29er mountain bikes and 28" hybrids - WTAF?. And just for shits and giggles 700mm in inches is 27.5. Whereas the 650b standard (AKA 27.5 or 27) is an ETRTO of 584. The 'b' was based around a 1.5" tyre for touring bikes which seldom has anything to do with the tyre size a self-respecting MTBer fits to such wheels.

The whole lot of 'em should be up against the wall when the revolution comes.

That's now SO much clearer.

 

[KennyB]

That's now SO much clearer.

Yeah, none the wiser but better informed

 

[Mikerb]

"when the revolution comes"..................

 

[steve_sordy]

I'm getting tyred of this thread!

 

[Mikerb]

it just round in circles 29Inch circles that measure.......errr