I assume those tire-rim safety charts are to keep the tire bead from popping off the rim? But this seems to be more of a concern if the tire is extremely wide compared to the rim.
I googled the title from the
chart link above, and found this from
Schwalbe:
That Schwalbe link also says:
Since 2006, the combination of extra wide tires and narrow 17C and 19C rims is officially approved by ETRTO. This just caught up with reality, because this combination has already been an every day occurance in MTBs and Balloonbikes for many years and has not caused any problems.
Often the use of a wider rim is useful because it brings additional stability to the tire. The tire pressure can be reduced slightly before the stability becomes “spongy”.
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HED's
recommendations are way different. (Those rim widths are outside dimensions. The "25mm" Ardennes Plus rims are
25.6mm outside at the top of the rim, 25.2 at the bottom of the brake track. The
inside dimension is 20.6 mm)
23mm C2 clincher rim recommended tire width: 21mm+
25mm Plus clincher rim recommended tire width: 22mm+
23mm C2 tubular rim recommended tire width: 20mm+
*Note: Our wide rims increase clincher tire volume, causing actual inflated sizes to be larger-than-advertised on the tire. Inflated sizes will be 1-2mm wider on our 23mm C2 rims, and 2-4mm wider on 25mm Plus rims.
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And the wider rims have less of an effect on the tire shape than I would have expected. The tires get both taller and wider, not just wider. I don't quite get it--but the wider rim is filling up more of the circle, so maybe it makes sense. This drawing is supposed to be from actual tire measurements.
From HED, via a slowtwitch
blog post:
