Originally Posted by alienator .
I see, Alfie, you can't respond with actual critical thought. The chart is either made from DIN specs or from ERTRO. So, spray all you want, if you think it gives you or claims credibility.
Just because something has been done, doesn't make it optimal. 19-20mm tires used to popular on the road, but that didn't make them optimal. Likewise, the use of 53 or 51mm tires on narrow rims isn't necessarily optimal just because it has been done or can be done. I know you don't have any scientific or technical intuition, so it's unlikely that you understand what "optimal" means. You might want to look it up. You might also want to discuss with actual tire engineers or people from tire companies to find what they consider optimal.
You should try learning, Alfie. That's what industry does. It learns and makes improvements. For example, you think wider rims are fashion or fad, but you apparently haven't actually stopped and considered why wider rims for a given tire size could be or are optimal. Perhaps, you're not able to understand.
I really don't expect a critically thought out response from you, as it sure does seem as if critical thought isn't something in your "tool box".
It's almost
cute & often pretty amusing to watch you
flail-away ...
- certainly, this particular instance where you are trying to defend the chart which you posted falls into the former category ...
Because, despite your never ending ability to ferret out various graphs-and-graphics, YOU manage to demonstrate surprising lack of critical
reading skills!
That you have embraced cycling so wholeheartedly is commendable, but that you have gaps in your historical knowledge is clear ...
Since 'I' do my cycling in the
real world, what someone arbitrarily thinks is optimal when a bicycle wheel & tire are sequestered away from an actual bicycle frame is of limited concern to me other than as a hypothetical parameter ...
- based on your comments, it would seem that you failed to read beyond the first sentence where 'I' observed that 53mm wide tires were commonly used on rims with 17mm bead-to-bead MTB wheels ...
- or, you have limited comprehension skills
If you were not as (
comparatively) new to the sport as you are, then YOU might realize why it is that 19mm-20mm tires became popular about 30 years ago ...
It is MY OBSERVATION, for YOUR information, that the phenomena can be easily attributed to the pendulum swinging from the relative extreme of 27" tires (
622-32 equivalent, or larger) to 700c clinchers coinciding with the aero movement in tubing/etc. which ([COLOR= rgb(128, 128, 128)]in the minds of the cognoscenti[/COLOR]) necessitated the smaller tire sizes ...
- to MY chagrin, that subsequently meant that the 700x25 equivalent of sew-up tires became all but impossible to acquire
For YOUR information, the 622-13 rims have the same brake surface width as a traditional tubular rim ...
- with the purpose being to facilitate wheel changes without needing to reset the brake pad offset ...
It's NOT that the bike industry "learns and makes improvements" [
as YOU have declared] as much as some of the
intelligentsia realizing that there was a reason that a 27" wheel's rim was as wide as it was-and-generally-remains ...
Just as the 622-13 rim was a response to facilitating tire changes, the proliferation of tubular CX tires (
yes, tubular CX tires have ALWAYS been around, but they certainly weren't particularly popular until recently) made installation-and-removal of a
622-32 equivalent tire (
that's the ERTRO for a 27x1.25 tire, too, BTW, in case you didn't catch the earlier statement of equivalence) extremely tedious on the equivalent of a 622-13 rim whose brake surfaces were only 19mm apart (
again, that is the width of a typical tubular rim) ...
- sew-up tires certainly do NOT need more gluing surface than the traditional tubular rims provides
- but, if YOU want to believe that marketing spiel, well, so be it
The right person (
team mechanic) must have "complained" loudly enough ... someone listened ... hence, the wider tubular rim ...
Which meant that a
wider-than-622-15 clincher rim to complement the wider tubular rim became the norm in-the-pits ...
AND, lo and behold, the feedback from the riders was that fatter Road tires were more comfortable to ride on ...
- the "industry" has known THAT for decades AND (FYI) that is one of the reasons why Hybrid bikes typically come with 700x42 +/- tires
- the 700x42 tires are necessarily mounted on wider rims because cantilever-and/or-V-brakes can only open so-far relative to the rim's braking surface ...
- but, YOU might know that if your cycling experience wasn't limited to a "Fair View" perception of the cycling world
- and, the boys-and-girls at the various cycling magazines might know that, too, if they weren't such toadies for the industry and so focused on selling only the higher end stuff which they are sent to play with & review
BTW. I think that the widest 700c rim which I may have is a ridiculously wide
SUN 202 rim (
622-19), but I have a 700x52 tire mounted on an Open Pro rim (
622-15) despite it NOT being optimal combination
just because 'I' can ... because, I know how to "open" the calipers ...
- yes, the straddle yoke must be unhooked to open the calipers wide enough to put the wheel in the frame otherwise the brake pads would not clear the tire's sidewalls
- if the frame had V-brakes, then the "noodle" would have to be unhooked to clear the tire's sidewalls
As long as the tire is partially inflated, it is NOT going to come off the rim ...
there is absolutely NO safety issue,
per se ...
- while perhaps not ideal, the FAT tire on the NARROW rim DOES become practical if narrower tires are used in the same frame for the same reason that 622-13 clincher rims exist
FYI. If your mind were a little more historically oriented rather than stuck wherever it is, then you would realize that the PRIMARY (as in "first") function of a tire was traditionally to protect the "rim" ...
For the tire to provide traction was secondary ...
- I hope that you can-and-therefore-will accept as a given that if a tire is TOO small relative to a particular rim width will sit within the well of the clincher & typically NOT provide either the necessary protection or cornering traction ...
- if not, then you need to do the experiment for yourself & mount a 622-19 tire in a 622-19 rim ... just as an obvious see-it-for-yourself-if-you-must example ...
So, for a bicycle (
that is what we are talking about) with rim brake calipers ...
- Again, "The brake pads are typically set a distance from the rim's braking surface which either the shop mechanic prefers OR which the rider prefers ... hopefully, the latter, but some rider's don't know better & simply go with how their bike comes (back) to them from the shop ..."
Alas, a typical Road brake caliper can only "open"
so-far relative to the rim's braking surface ...
... regardless of whether-or-not the intent of the tire is to protect the rim, then the largest tire which can be fit between the
properly adjusted brake caliper's pads becomes the
de facto "optimal" tire to use --
Q.E.D. 
