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When did ETRTO came with rim/tire width recommendations? Why?

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When did ETRTO came with rim/tire width recommendations? Why?

Old 01-21-20, 04:18 PM
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avrilboazmoss
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When did ETRTO come with rim/tire width recommendations? Why?

I noticed many CX bikes back in the day (prior around 2010) came with 15C rims and had 35mm tires on them. Nowadays, these would be considered out of specs by ETRTO, some even publish more restricted ranges marking anything outside but within ETRTO as "non-optimal".

Does anyone understand how it became that universal regulatory body came to dictate these for the manufacturers rather than manufacturers defining what's permissible for their own products?

Also, what is the logic behind e.g. 35mm tire being out of spec for 15C rim, but 19C can take tire up to 62mm - more than triple?

Has the hook design changed over time (NOT talking about hook-less rims), or the tire beads or what caused the regulation to become necessary?

https://www.wtb.com/pages/tire-rim-fit-chart
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Old 01-21-20, 04:25 PM
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Nobody dictates to me about what size tire I use.
They're European........ Would you prefer the French set the standards?
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Old 01-21-20, 05:17 PM
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AFAIK, ETRTO doesn't make recommendations; they just define a uniform standard for designating bead seat diameter and rim width. Tire and rim manufacturers make recommendations on what dimensions work best together with their products.
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Old 01-21-20, 09:35 PM
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The only logical argument I've seen is for carbon rims. Apparently some can be damaged if running the wrong size tires. I just try the tire/rim combo and if it mounts up okay It's fine. I suppose that doesn't help if you don't have experience and are trying to order tires or something.
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Old 01-21-20, 10:10 PM
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With the globalization of our industry being able to use an Asian tire on a Euro rim (or pick your own brand/country of origin) has become even more vital for consumer happiness and safety. ETRTO and ISO are attempts to better give manufactures and designers the foundation for greater options and ability to spec and expect compatibility. Any one who was around in the 1970s (or before) in our industry knows the cost of no standards. The Southerland's Manual was in the forefront of trying to establish the old dimensional practices, check it out sometime. But like before then today's designers want to stand out from the crowd. To produce a product that has mass appeal but no aftermarket supply other then that of the designer's manufacturing. Back in the day it was more about national markets then these days. Having standards allow a manufacturer the faith in investing is a dimensional spec, to produce a product and be able to recoup their development costs.

There's no one saying that you can't come up with your own standards/specs and if the market agrees it will become one more option. If the market votes otherwise then your spec is one more short lived attempt lost to time. Andy (and I haven't begun to include the legal department yet)
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Old 01-21-20, 10:20 PM
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I had Schwalbe CX Pro 30mm tires on narrow rims and if the front tire flatted the bike would be impossible to steer and would crash. Maybe some other wide tire/narrow rim combinations have that same problem?

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Old 01-22-20, 08:17 AM
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Briefly, there are three major tire/tyre standards orginizations:

TRA (Tire and Rim Association) - US
ETRTO (European Tyre and Rim Technical Organization) - EU
JATMA (Japanese Automobile Tyre Manufacturers Association) - Japan

The standards contain standardized load tables, tire size nominal dimensions, and RIM CONTOUR DIMENSIONS and rim width.

The rim manufacturer is responsible for manufacturing a rim to the rim contour dimensions and rim width.

The tire manufacturer is responsible for desigining a tire that follows the load tables. They typically follow (but aren't actually required to) follow the nominal tire size dimensions. Probably more importantly, the tires MUST mate with the standard rim contour(s) and widths. (For tubeless tires, that also means must hold air when mounted on a standard rim contour.)

(One subtle thing that is the nominal tire size dimensions are done on a measuring rim. The tire can be mounted on a range of rim widths. The tire dimensions will vary from measured dimensions on different rim widths. Mounting a tire outside of its supported rim width range is, uh, unsupported.)

TRA, ETRTO and JATMA are all slightly different standards. All spec passenger car and light truck tires. ETRTO also does bicycle tires.

(Finally, there are related perfomance standards for speed ratings, wear ratings, and rolling resistance ratings.)

-mr. bill
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Old 01-22-20, 09:34 AM
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Originally Posted by avrilboazmoss View Post
I noticed many CX bikes back in the day (prior around 2010) came with 15C rims and had 35mm tires on them. Nowadays, these would be considered out of specs by ETRTO, some even publish more restricted ranges marking anything outside but within ETRTO as "non-optimal".

Does anyone understand how it became that universal regulatory body came to dictate these for the manufacturers rather than manufacturers defining what's permissible for their own products?

Also, what is the logic behind e.g. 35mm tire being out of spec for 15C rim, but 19C can take tire up to 62mm - more than triple?

Has the hook design changed over time (NOT talking about hook-less rims), or the tire beads or what caused the regulation to become necessary?

https://www.wtb.com/pages/tire-rim-fit-chart
It's not worth getting THAT worked up about. ETRTO came up with their specifications and recommendations many decades ago (longer ago than you realize). The recommendations are given to show what should reasonably be expected to work. Anything outside of those are not a "SHALL NOT", it just means you're on your own if the tire squirms or blows off. Your question about 19mm rims taking 62mm tires comes from the 1980s/1990s when people decided to start putting skinny rims on MTBs. Since it worked well enough, they extended the chart to reflect that.

For some reason, people have gotten really anal retentive about tire/rim combinations lately, and want to cede all of their thought processes to charts and graphs. It used to be that you would try it, and if it worked, you were happy.
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Old 01-23-20, 05:44 PM
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BTW there is a new ETRTO standard being drafted. You can see a new table of tire/rim/pressure recommendations at THE RIGHT TYRE WIDTH ON THE RIGHT RIM WIDTH - Engineerstalk : Engineerstalk

Generally speaking, itís more acceptable to run narrower tires on wider rims than with the old ETRTO recommendations.
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