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

(Example: Framebuilding:Brazing Technique)

In-Reply-To: <E1N92aY-0006im-Qp@elasmtp-mealy.atl.sa.earthlink.net>
References: <575355.88010.qm@web35902.mail.mud.yahoo.com>
Date: Sat, 14 Nov 2009 07:20:27 -0500
From: "Ken Freeman" <kenfreeman096@gmail.com>
To: Mark Stonich <mark@bikesmithdesign.com>
Cc: classicrendezvous@bikelist.org, David Feldman <feldmanbike@yahoo.com>
Subject: Re: [CR] Thank you/Was 700 x 28 tires on narrow Weinmann Concaves


Filling to 125 and letting it sit sounds like a good way to test retention, with a potential bead mismatch. It's not easy to see how well that overpressure represents long term use on a dynamic road surface, but it's certainly better than no test.

Are you concerned with the fact that 125 psi is a lot more than the recommended 87 psi max? Do you have experience with this? Please share, I'm curious.

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. The actual tire can be approximated by a torus, or donut with a round cross section, that has had a chord cut out representing the rim width. The part of the circumference that remains is fixed for a given tire. The chord will be wider for a wide sport-tour rim than for a narrow racing rim, like your Concave, or my MA-40's (there, finally, some CR content!!!). Of course the same will hold for modern iron and rubber ...

I have an example of this at home in my fleet: I have Conti 28 mm Gator tires on my steel Trek with 700c MA-40s, and the same tire on the commuting rim of an off-topic Breezer Liberty, with a between-hooks dimension around 20 mm. On the Breezer the 28 mm tire measures a bit wider than 28 mm, and on the Trek (a 14 mm rim), the tire measures around 26 mm. Both inflated 90-100 psi. I think the added width reflects a small increase in contained air volume, hence a small increase in rim protection.

On Fri, Nov 13, 2009 at 3:17 PM, Mark Stonich <mark@bikesmithdesign.com>wrote:
> I received several off list postings from people who had used such a combo
> with good luck. Thank you
>
> The Michelin Dynamics have steel beads and I intend to run them near the
> middle of their 58-87 psi range. It's nice to see that it's becoming more
> common to find tires that give a range of pressures instead of just a
> maximum. And tires that are actually as big as their nominal size. I like
> a tire that is large and supple enough to roll well at moderate pressures.
>
> Before riding I'll pump them up to 125 or so and let them sit overnight.
> Rims and tires have a +/- tolerance and judging from the chore it was
> getting the old tires off, I think these rims are on the plus side of the
> tolerance.
>
> Right now I do have a 20 y/o set of folding 23mm Michelins on them to
> protect the rims as I build up the bike. They seem to be seated well into
> the rim.
>
> At 11/13/2009 10:10 AM -0800, David Feldman wrote:
>
>> I used wire bead 28's on Concaves when they were current product. I would
>> stick to wire bead tires on them--there were warnings that their bead shape
>> wouldn't hold a folding tire back in the day, to the point where Specialized
>> included printed, illustrated warnings with early folding Turbo tires.
>> David Feldman
>> Feldman's Bicycle Repair
>> Vancouver, WA
>> 360-694-4228/503-998-7249
>>
>
> Mark Stonich;
> BikeSmith Design & Fabrication
> 5349 Elliot Ave S. Minneapolis, Minnesota 55417 USA
> Ph. (612) 824-2372 http://bikesmithdesign.com
> http://mnhpva.org _______________________________________________
>

--
Ken Freeman
Ann Arbor, MI USA