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Presta Valve to Schraeder Hole Adapter

The front rim on my Tour Easy developed a distinct bulge, of the sort usually caused by ramming something, but I’m not Danny McAskell and the bulge got worse over the course of a few weeks, suggesting the rim was deforming under tire pressure. Having ridden it upwards of 35 k miles with plenty of trailer towing and too much crushed-stone trail riding, the brake tracks were badly worn and it’s time for a new rim.

An Amazon seller had an identical (!) rim, except for the minor difference of having a hole sized for a Schraeder valve stem, rather than the Presta valves on the original rims. One can buy adapters / grommets, but what’s the fun in that?

The brake track walls are 1.5 mm thick on the new rim and a scant 1.0 mm on the old rim, so, yeah, it’s worn.

A few measurements to get started (and for future reference):

Presta to Schraeder Adapter - dimension doodle

Presta to Schraeder Adapter – dimension doodle

If you don’t have an A drill, a 15/64 inch drill is only half a mil larger and, sheesh, anything close will be fine.

Introduce a suitable brass rod to Mr Lathe:

Presta-Schraeder Adapter - parting off

Presta-Schraeder Adapter – parting off

Break all the edges and drop it in place:

Presta-Schraeder Adapter - installed

Presta-Schraeder Adapter – installed

One could argue for swaging the adapter to fit flush against the curved rim, but commercial adapters don’t bother with such refinements and neither shall I.

The 7.0 mm length got shortened to fit flush with the center of the rim:

Presta-Schraeder Adapter - valve stem installed

Presta-Schraeder Adapter – valve stem installed

It’s brass, because the rim is heaviest on the far side where the steel pins splicing the ends live, and, with the tube & tire installed, the rim came out almost perfectly balanced. Which makes essentially no difference whatsoever, of course.

The shiny new rim sports shiny new reflector tape (from the same stockpile, of course).

That was easy …

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  1. #1 by Daniel B. Martin on 2018-08-02 - 07:53

    Did you consider using a Schraeder valve tube? IMHO Presta valves are a nuisance. I converted my Presta wheels to use Schraeder tubes. Drill, baby, drill!

    • #2 by Ed on 2018-08-02 - 09:14

      Nope!

      I’d have to drill the three other Presta rims (dismount tire, drill, install new tube, remount tire) and that seems like way more work and much less fun than turning one brass adapter.

      That said, I swapped out the perfectly good tube and totally wrecked tire from the old rim, installed a shiny-new front brake, and replaced the cable.

      To the road!

    • #3 by RCPete on 2018-08-02 - 13:36

      I went the other direction when I tried slick tires on my mid-80s Rockhopper. They wanted close to 100psi, and Schraeder valves leaked too much, while Prestas handled the pressure just fine. When I went back to non-slick tires (mostly road riding, some gravel), I stayed with Presta. They’re also a lot easier to inflate; the Schraeder valve pins are too fussy for my taste.

      The grommets worked fine. [grin]

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