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bobknh

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Reply with quote  #1 
Here is an interesting discussion about tire an rim width from Lennard Zinn: http://www.velonews.com/2018/06/bikes-and-tech/technical-faq/technical-faq-tires-widths-cassettes-coasting_468445
A
lthough Zinn is not everyone's go-to expert on bike tech., over the years, I've found him to be a reliable source of bike tech. advice and opinion. My take away from this discussion is that while there is considerable standardization by the ETRTO for rims and tires, there is virtually no standardization for combination of specific rims with specific tires. Rim manufacturers go their own way in interpreting the ETRTO standards for rims, while tire manufacturers dance to their own interpretation. Of course, there are manufacturers of both rims and tires, who then try to promote their own mating of tires to their own proprietary designs. This gets particularly confusing and difficult when we throw in the requirements for tubeless. No wonder we have problems mating some tires to some rims. In the meanwhile, I'm hoping that someone will do some extensive testing so that we can optimize our own selection of rims and tires. I'm not holding my breath though!
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chas

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Yeah, I saw that.   Schwalbe has a nice ETRO chart on their site.  I kinda ignore it though - but I wouldn't go too extreme on pressure if I have a mismatched combo.

I'm using a (fat) 28mm on a 23c rim (tire measures 31) and a 32mm on a 12c rim at the extremes.  Not optimum, but...

[Untitled_0] 
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Mark_Landsaat

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This is kind of a can of worms since there's likely as many opinions as there are possibilities. One of the companies trying to address this is Stan's. The have tire width recommendations for their rim profiles based on rim width.

It's an interesting read and it makes sense.

https://www.notubes.com/technology/wide-right 
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bobknh

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Quote:
Originally Posted by chas
Yeah, I saw that.   Schwalbe has a nice ETRO chart on their site.  I kinda ignore it though - but I wouldn't go too extreme on pressure if I have a mismatched combo.

I'm using a (fat) 28mm on a 23c rim (tire measures 31) and a 32mm on a 12c rim at the extremes.  Not optimum, but...

[Untitled_0] 

Thanks for posting the table. Do you know if the rim width used is external or internal? Of course, since the shape of the rim/bead contact varies by manufacturer - especially for rims designed for tubeless, I'm not sure how meaningful this is. Also for tire widths I use for gravel 35-40mm there seems to be a wide range of compatible rim widths. Which begs the question of what is the optimal rim/ tire width for any particular tire/rim. And, since we typically run much lower pressure for gravel, how does this effect things?
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chas

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Its internal rim width.

The chart is meaningful for matching rim to tire - unless a mfg tells you different.  Since gravel riders use low PSI, it is even more critical that we get this right.

That 32mm/19c combo I mentioned above works at moderate pressure and with an innertube.  However at lower pressures, that light bulb shape handles horribly as the sidewall is pinched too much to keep the tire stable on a side load.  Wouldn't work too well as a low pressure tire (but since I have a tube in it, I can't go too low anyway).
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chas

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Reply with quote  #6 
Quote:
Originally Posted by Mark_Landsaat
This is kind of a can of worms since there's likely as many opinions as there are possibilities. One of the companies trying to address this is Stan's. The have tire width recommendations for their rim profiles based on rim width.

It's an interesting read and it makes sense.

https://www.notubes.com/technology/wide-right 


Interesting 
as an example they state for one of their wheels

28mm WideRight rim design optimized for 25mm-40mm tires

Rim Internal Width: 21.6 mm
Rim External Width: 28.0mm

https://www.notubes.com/avion-pro-wheelset

a little different than the ETRO chart.


(That hyper link did not resolved, but worked for me when I did a cut and paste.)
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bobknh

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Reply with quote  #7 
Thanks for all of your input. After reading through it, and considering my own experience with various rim, tire, pressure, tubed, tubeless, tubular -- combinations, I can well understand why there are no really good guide lines. I also understand why some tire and rim combinations can be so difficult to mount and remove; and why some are more or less difficult to seat tubeless. I share Lennards Z's concerns, that few in the bicycle industry are doing meaningful work in closing our gap in understanding. Rim and wheel manufactures know rims. Tire manufacturers know tires. But, it is up to you and me to figure out which tires work best on which rims. And, which combinations don't work to well, or, for that matter are downright dangerous.
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