Bike Forums - View Single Post - Crown race 26.6 sanding

07-19-15 | 11:45 PM

#10

verktyg

verktyg

Joined: Jul 2006

Posts: 4,034

Likes: 1,271

From: SF Bay Area

Bikes: Current favorites: 1988 Peugeot Birraritz, 1984 Gitane Super Corsa, 1980s DeRosa, 1981 Bianchi Campione Del Mondo, 1992 Paramount OS, 1988 Colnago Technos, 1985 RalieghUSA SBDU Team Pro

Question?

Is the headset crown race 26.6mm or the mounting area on the fork crown where the race fits 26.6mm?

Per [MENTION=396625]JonD[/MENTION]Thompson, the fork crown should be 26.4mm,

Sounds like you have a Stronglight B10 needle bearing headset. The cups, cones and crown race are made of Delrin plastic. The needle bearings run on hardened steel races.

Those headsets were available with 26.4mm, 26.5mm and 27.0mm bores in the Delrin plastic crown races.

A 26.6mm bore would be a "fall on fit" on a 26.4mm fork crown. It should be a slight interference fit.

0.2mm is a lot of slop in a crown race and after a long ride it will probably get larger! You will be able to sense this a clunk when you brake hard, come to a stop or hit a bump.

A suggestion... Take an aluminum beverage can, using scissors, cut out a shim to fit between the inside of the crown race and the fork crown. This will keep the crown race from getting further damaged.

If it were a metal crown race, I'd recommend Loctite bearing mount but it may not play well with olde plastic...

I always reface the fork crown and the top and bottom of the head tube anytime I have a headset apart. I have the tools to do it but many shops don't or don't know how to use them properly.

Trek built quality frames and yours was faced before it was painted so the head tube and fork are probably still OK (unlike many Holy,Holy scared European, especially high end Italian frames!). It wouldn't hurt to have the fork crown refaced just for yuks!

Your Stronglight B10 headset is ~30 years old and plastics get long in the tooth over time.

I'd recommend replacing the head set with either one of the new Stronglight A9 headsets with precision ball bearings in cartridges. They work very well and look the same as the old needle bearing A9s.

If you buy one of these, make sure that it's made of aluminum alloy. There are some black ones being sold that are black painted steel and have loose bearings not cartridges.

Another suggestion would be a Tange Levin CDS headset. They are very well made with through hardened precision ground steel races. They come in polished chrome, satin chrome and black finishes and have plastic dust seals. You can find them for under $30.00 USD.

BTW... the French have had an almost unholy, kinky thing about DuPont Delrin® plastic... Think Simplex derailleurs, MAFAC brake levers, Stronglight A10 headsets.... Maybe it has to do with the DuPont name being French or maybe their attraction to Jerry Lewis!