ETRTO rim widths, nonsense or any actual reasoning?

[DougC]

It has been noted by more than a few people that the ETRTO tire/rim
charts are heavily predisposed to mounting FAT tires on very skinny rims.

Some of us brave and daring souls have found that you get a much better
ride if you obtain a tire/rim combination where the rim is nearly (80%
or so) as wide as the tire.

What is the technical justification for the ETRTO reasoning? Has anyone
here read the official test explanation?

You have to pay them money to see the current copy, they don't post it
online for free.
Also some of the ETRTO material simply defers to,,,,,,, ISO regulations,
that you also have to pay to see.

This page provides a glimpse of the ETRTO foolishness:
http://engineerstalk.mavic.com/the-right-tyre-width-on-the-right-rim-width/

The US CPSC regulations for bicycles don't say anything about being
limited to any certain range of tire sizes based on rim width. Nor does
it refer to any outside rules, such as ETRTO or ISO.

The US CPSC rules do require that the (bicycle) tire must be marked with
its intended BSD and inflation pressure.

[DATAKOLL MARINE RESEARCH]

THUD another landing BUT ! EuroSpace learned valuable data...for example

MARS LANDINGS ARE NOT THEIR FORTE

that said.....ERTO was designed to supply information out of a commercial quagmire caused by language differences and the usual guild BS ....

thus we go to HARRIS CYCLERY for an explanation of ERTO


http://www.sheldonbrown.com/tire-sizing.html

[Andre Jute]

On Wednesday, November 2, 2016 at 1:10:35 PM UTC, Doug Cimperman wrote:
> It has been noted by more than a few people that the ETRTO tire/rim
> charts are heavily predisposed to mounting FAT tires on very skinny rims.

ETRTO is a trade body, supported by the rim and perhaps by the tyre manufacturers.

They compromised their own credibility when balloon tyres made a comeback by first announcing the perfectly reasonable rule of thumb that the rim across the tyre hooks must be at least 40% of the tyre width, and then, under pressure from manufacturers with stocks of narrow rims that would suddenly become unsalable, "discovering" that narrower rims were permissable.

> Some of us brave and daring souls have found that you get a much better
> ride if you obtain a tire/rim combination where the rim is nearly (80%
> or so) as wide as the tire.
>
> What is the technical justification for the ETRTO reasoning? Has anyone
> here read the official test explanation?
>
> You have to pay them money to see the current copy, they don't post it
> online for free.
> Also some of the ETRTO material simply defers to,,,,,,, ISO regulations,
> that you also have to pay to see.
>
> This page provides a glimpse of the ETRTO foolishness:
> http://engineerstalk.mavic.com/the-right-tyre-width-on-the-right-rim-width/

This is an interesting article but I think their maximum width restriction, for instance that a 21mm rim cannot take tyres narrower than 35mm, is conservative. Chalo, all 350 pounds of him, swore by 38mm wide (internally!) rims he sourced from mountain unicycles, with 60mm Big Apples, already about 1/20th or 5% outside that "rule". I never heard that Chalo had any problem with tyres demounting themselves or excessive snakebites or any trouble at all.

> The US CPSC regulations for bicycles don't say anything about being
> limited to any certain range of tire sizes based on rim width. Nor does
> it refer to any outside rules, such as ETRTO or ISO.
>
> The US CPSC rules do require that the (bicycle) tire must be marked with
> its intended BSD and inflation pressure.

I think the question remains open and each cyclist must gather his own empirical evidence. I currently ride on 60x622 Big Apple Liteskins, mounted to very stiff wheels built on Exal rims 24mm wide internally and I would say that is a minimum, and that more comfort and security may be obtained by going wider. I have experience of the same tyres on 16mm internal width rims, nowhere near as stiff as my current wheels, and the difference in comfort is less than you would expect, the handling doesn't deteriorate until very high cornering loads are achieved, but I always felt a little uneasy and restrained my natural exuberance during the period the narrow rims were on the bike. For myself, with the 60mm tyres, I would go wider in the rims when the opportunity offers, but I won't again go any narrower. I suppose it depends on how you ride, but I hang it on the limit often enough to want the best gear under me, with components properly scaled to each other.

In short, I think a definitive tyre-rim width relationship is some ways off yet.

Andre Jute
A subjective opinion based on informed experience is already empirical evidence

[Gregory Sutter]

On 2016-11-02, DougC <dci...@norcom2000.com> wrote:
> It has been noted by more than a few people that the ETRTO tire/rim
> charts are heavily predisposed to mounting FAT tires on very skinny rims.
>
> Some of us brave and daring souls have found that you get a much better
> ride if you obtain a tire/rim combination where the rim is nearly (80%
> or so) as wide as the tire.

There is a present trend of wider rims for wider tires, which both
works better aerodynamically (FWIW) and provides more stability for
cornering loads as shown here (from the article below):
https://intheknowcycling.files.wordpress.com/2016/04/wide-rim-drawing.jpg

I found this article quite enlightening:
https://intheknowcycling.com/2016/04/03/best-wider-road-bike-tires-wheel-sizes/

--
Gregory S. Sutter Mostly Harmless
mailto:gsu...@zer0.org
http://zer0.org/~gsutter/

[James]

On 04/11/16 14:51, Gregory Sutter wrote:
> On 2016-11-02, DougC <dci...@norcom2000.com> wrote:
>> It has been noted by more than a few people that the ETRTO tire/rim
>> charts are heavily predisposed to mounting FAT tires on very skinny rims.
>>
>> Some of us brave and daring souls have found that you get a much better
>> ride if you obtain a tire/rim combination where the rim is nearly (80%
>> or so) as wide as the tire.
>
> There is a present trend of wider rims for wider tires, which both
> works better aerodynamically (FWIW) and provides more stability for
> cornering loads as shown here (from the article below):
> https://intheknowcycling.files.wordpress.com/2016/04/wide-rim-drawing.jpg
>
> I found this article quite enlightening:
> https://intheknowcycling.com/2016/04/03/best-wider-road-bike-tires-wheel-sizes/
>

The rolling resistance the author refers to is the steel drum test,
AFAICT. There has been a bit of work since then that shows the steel
drum test may be ok for comparing tyres, but doesn't reflect the real
world where tyres are used on coarse ship sealed roads.

I have a 23C tyre on a 15C rim on the front, and a 25C tyre on a 15C rim
on the back. The 25C back tyre actually measures 27mm. I've had some
fastest times and more comfort with only about 80psi in the tyres, on
coarse chip sealed roads.

--
JS

[DATAKOLL MARINE RESEARCH]

Increasing profits thru niche mining, the industry sprang from Touring into floatation for bottom end riders needing float on concrete.

[John B Slocomb]

On Fri, 4 Nov 2016 15:31:28 +1100, James <james.e...@gmail.com>
wrote:

I'm a believer.... but...

While the 80 psi tires work great on reasonably smooth roads they
aren't very successful on some of the Bangkok streets which may be
very smooth and well paved but are more likely to be literally filled
with drainage gratings, manhole covers and even large steel plates
measuring 4 x 12 feet, all of which present sharp 90 degree corners
sticking up out of the roadway. After having two snake bite flats in
one kilometer I have changed to 90 psi (both wheels) and (knock on
wood) so far no flats :-) It is hard to dodge the man hole covers when
you are riding between a 12 inch curb and a row of cars doing twice
your speed :-(

In Phuket where nearly all the roads are smooth blacktop I use the 80
psi figure with no problems and as you say, with much more comfort.

[DATAKOLL MARINE RESEARCH]

https://www.schwalbetires.com/images/profile_may_2006.pdf

[Frank Krygowski]

As James said, almost all measurements of rolling resistance are done on
steel drums. This gives nice consistent results, but the results have
limited usefulness, because they don't include the suspension effect of
the tire, which is the real reason we use pneumatic tires in the first
place. (Look at the limiting case: A steel drum would give the lowest
rolling resistance to a smooth solid steel tire!)

Ideally, both tire size and tire pressure would be instantly adjustable,
to account for road conditions. For super-smooth roads, you'd use
super-high pressure and the required small tire cross sections to
contain that pressure. If you were really fast, that might also give you
a bit of aero advantage.

For rougher "chip seal" roads you'd quickly change to lower tire
pressure, and if there were big bumps you'd greatly increase the cross
section as well.

Practically, that's impossible, so compromise is necessary. The
simplest compromise is riding a bit slower, and perhaps jumping the
bumps you couldn't steer around.

--
- Frank Krygowski

[Gregory Sutter]

On 2016-11-04, Gregory Sutter <gsu...@zer0.org> wrote:
> On 2016-11-02, DougC <dci...@norcom2000.com> wrote:
>> It has been noted by more than a few people that the ETRTO tire/rim
>> charts are heavily predisposed to mounting FAT tires on very skinny rims.
>>
>> Some of us brave and daring souls have found that you get a much better
>> ride if you obtain a tire/rim combination where the rim is nearly (80%
>> or so) as wide as the tire.
>
> There is a present trend of wider rims for wider tires, which both
> works better aerodynamically (FWIW) and provides more stability for
> cornering loads as shown here (from the article below):
> https://intheknowcycling.files.wordpress.com/2016/04/wide-rim-drawing.jpg
>
> I found this article quite enlightening:
> https://intheknowcycling.com/2016/04/03/best-wider-road-bike-tires-wheel-sizes/

Here's a fresh article on the widening of rims:
https://cyclingtips.com/2016/11/the-new-normal-the-thinking-behind-wide-road-wheels/

[Duane]

I've been using HED Ardennes 25SL wheels with 23mm tires for a few years
and like them. The difference in cornering is notable. And the lower
pressure (90 psi) is more comfortable on Québec roads.

--
duane

[Frank Krygowski]

On 11/20/2016 6:32 AM, Duane wrote:
>
>
> I've been using HED Ardennes 25SL wheels with 23mm tires for a few years
> and like them. The difference in cornering is notable. And the lower
> pressure (90 psi) is more comfortable on Québec roads.

A comment made to me on a recent club ride: "Do you have enough air in
your rear tire?? There's a little bulge at the bottom!"

My response: "There's _supposed_ to be a little bulge at the bottom!"

(The commenter weighs maybe 140 pounds and uses something over 120 psi.
He's probably never seen his tires deflect.)

--
- Frank Krygowski

[Phil Lee]

Frank Krygowski <frkr...@sbcglobal.net> considered Sun, 20 Nov 2016

He's probably lucky to see anything when riding on chip & seal - other
than the bills from his dental surgeon for replacing fillings!