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Can someone explain ETRTO meanings?

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Can someone explain ETRTO meanings?

Old 02-06-16, 12:07 PM
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Can someone explain ETRTO meanings?

I was considering replacing some stock wheels that came on my Nashbar steel CX bike. The wheels are Alex C19s.

Per label on these rims and the Alexrims website, they are ETRTO 622x16
Not sure.. is the 16 the measurement of the inside of rim or the rim exterior width. I put some 35mm tires on them, and haven't had a problem (yet).

As a replacement wheel was looking Fulcrum 5 LG CX models. Which per Fulcrum website are ETRTO 17C, 23mm exterior width.

So confusion comes in here.. My CX bike came with 32mm knobby-ish tires and I replaced with 35mm touring tires.. no problem, or so I would think per the chart that Schwalbe uses here near bottom of page: Tire Dimensions | Schwalbe North America

At the same time, the Fulcrum website for the 5 LG wheels indicates compatibility only with the fairly narrow 25-32mm range, even though the schwalbe site indicates a 17c rim should be good up to 50mm width tire? Racing 5 LG CX - Cyclocross Wheels

So what gives? Just legal protection for Fulcrum... or are not all wheels created equal?

(side question.. is there any reason one would not get the CX version of the 5 LGs? Seemingly only a $20 upcharge for the wheelset)
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Old 02-06-16, 12:30 PM
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There's this: Tire Sizing Systems

16 on your C19's should be internal width.

There is a red and green chart lower down on the page at the link I put above that may help you. Note that there is no row for 16c rims, but the commentary before and after the chart may be helpful.
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Old 02-06-16, 01:26 PM
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Originally Posted by Igualmente
There's this: Tire Sizing Systems

16 on your C19's should be internal width.

There is a red and green chart lower down on the page at the link I put above that may help you. Note that there is no row for 16c rims, but the commentary before and after the chart may be helpful.
That's basically the chart I was referring to on the Schwalbe website I linked. However i think the one you linked was from pre-2007 and is considered outdated. Ie. the Schwalbe chart is copied below. But this is my question.. why would Fulcrum indicate that their 17c wheel is only compatible with 25-32mm tires?
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Old 02-06-16, 01:47 PM
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ETRTO standards have now been incorporated into ISO 5775.

I notice that ISO 5775-1 (Tire designations and dimensions) ISO 5775-1: 2014 was updated in 2014, and ISO 5775-2 (Rims) ISO 5775-2 :2015 was updated in 2015.
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Old 02-06-16, 03:35 PM
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Originally Posted by Sy Reene
But this is my question.. why would Fulcrum indicate that their 17c wheel is only compatible with 25-32mm tires?
Presumably Fulcrum has some reason for limiting it to 32mm, but I don't know. I'd point out that HED probably has a reason for recommending at "22mm+" tire for their Ardennes Plus SL (https://www.hedcycling.com/ardennes/a...dennes-plus-sl under the specifications tab), which has a 21c rim. Boyd says their 19.86mm internal width Altamonts work well with 23mm tires (2016 Altamont Alloy Clincher - Boyd Cycling). Those seem to be off the chart too, so maybe there is something about individual wheel designs that allow it, or maybe the chart has issues. Dunno.
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Old 02-06-16, 03:48 PM
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Originally Posted by Sy Reene
....But this is my question.. why would Fulcrum indicate that their 17c wheel is only compatible with 25-32mm tires?
Of course, no one can say what's on Fulcrum's mind, but two possibilities come to mind.

1- the obvious, is that they are saying the ideal tire width for optimum profile, and based on the numbers they're basically in line with most players.

2- less obvious is a strength issue. The stress that the tire puts on a rim's flange is proportional to the tire pressure X the tire width. ie. a 50mm tire at 50psi stresses the rim equally (just about) as a 25mm tire at 100psi. With wider tires now sporting very high pressure ratings, it can throw off the rim makers calculation of needed flange strength, and the wear limits. We're seeing flange wear failures far more commonly than we did a few decades back. I have to wonder if it's because of wider tires at higher pressures.
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Old 02-06-16, 04:10 PM
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So to go about the question another way, and perhaps better suited to the touring forum.. what rim would one suggest for running typical touring/city tires that typically can come in 32-38mm widths? eg. the Schwalbe Marathon's and the like.

FWIW I have Vittoria Randonneur Pros in 700x35. Usually I follow the PSI rating on the tires which is I think max of 70-75.
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Old 02-06-16, 04:20 PM
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Originally Posted by Sy Reene
So to go about the question another way, and perhaps better suited to the touring forum.. what rim would one suggest for running typical touring/city tires that typically can come in 32-38mm widths? eg. the Schwalbe Marathon's and the like.

....
I don't get in to brands, but I'd be looking at a rim in the 19-21mm width range. Of course it'll be heavier, but likewise it'll be beefier than a rim made for racing or club riding.

There's no real reason that you can't exceed the guidelines on the tire/rim charts, but tires that are wider tend to get very sloppy if underinflated, and I've experienced handling issues (and low speed crashes), when a slow leak caused me to ride at low pressure unknowingly. I currently ride 50mm tires on my 21mm rim, and have (by necessity) learned to stay very attuned to any hint of low tire pressure.
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