Re: [CR] Thank you/Was 700 x 28 tires on narrow Weinmann Concaves

(Example: Framebuilders:Brian Baylis)

Date: Sat, 14 Nov 2009 08:43:12 -0600
To: Ken Freeman <kenfreeman096@gmail.com>
From: "Mark Stonich" <mark@bikesmithdesign.com>
In-Reply-To: <7543b4a40911140420u1d87a600r16d6f8dbca51efa6@mail.gmail.com>
References: <575355.88010.qm@web35902.mail.mud.yahoo.com> <E1N92aY-0006im-Qp@elasmtp-mealy.atl.sa.earthlink.net>
Cc: classicrendezvous@bikelist.org
Subject: Re: [CR] Thank you/Was 700 x 28 tires on narrow Weinmann Concaves


At 11/14/2009 07:20 AM -0500, Ken Freeman wrote:
>Are you concerned with the fact that 125 psi is a lot more than the
>recommended 87 psi max?

Not at all.
> Do you have experience with this? Please share, I'm curious.

Not direct experience but; It is often stated, accurately I hope, that manufacturers test their tires to double the rated inflation.

Destructive tests done by others in the HPV community confirm this. Rims have often failed before tires.

In order to reduce excess rolling resistance due to opposing camber thrust, wheelchair racers run their tires at nearly double rated pressures. I've been told that coast down tests show a noticeable difference in RR between 200 psi and 220.
>A side topic, that I think is also of interest:
>Every time I see a discussion of tires that do not measure their
>advertised size, I think there's a term left out of the equation:
>the installed width of the tire should depend not only the tire
>design (which can certainly involve some gamesmanship, and more so
>with actual vintage on-topic tires), but also the rim width.

Another factor is tire pressure. They do stretch. Somewhat O.T but illustrating both factors; I have a '75 Raleigh "Twenty", originally designed for the British market with 451 rims and 1-3/8" tires. But sold here with the same fork but with very wide steel 406 rims and 1.75" tires. When I installed some 1.95" tires at 35 psi I had at least 1mm clearance on each side but when I tried 50 psi the tire rubbed the fork blades. Now on 27.5mm alloy rims I have at least 2mm clearance on each side even at the tires rated max of 85 psi.

Because of these two factors, if a tire is on a rim that is within the range of what is appropriate for the tire and is within +/- 1.5mm of it's rated size I consider it accurately labeled. I have seen older Specialized and Continental tires rated at 32mm or 1-14" which measured less than 26mm

Mark Stonich;
     BikeSmith Design & Fabrication
       5349 Elliot Ave S. Minneapolis, Minnesota 55417 USA
            Ph. (612) 824-2372 http://bikesmithdesign.com
                        http://mnhpva.org