Friday, December 8, 2017

Carbon clinchers - an oxymoron?

Finally, a dirty little secret is revealed

Photo from Cycling Tips

Twenty years ago, pretty much about the same time we started CycleItalia, clincher wheels made from carbon fiber started to appear on the market.

Uncle Larry was skeptical (some would say cynical) from the beginning about the claims being made for these products. He remembered attempts to make square-taper bottom bracket spindles using titanium, which contrary to popular belief is NOT as strong as steel. 

Simply making a part in the same shape and dimensions using a material inferior in strength is at best a foolish gamble. The bottom brackets failed, sometimes to the point the rider was left on the ground with a pedal and crankarm still attached to their shoe!

A redesign was in order, with far larger diameters and different specifications, something that can't be done with a clincher rim. It must be made to a specific shape to retain the tire and its internal pressure no matter how much of an aerodynamic wind-cheating design is used.

Tubular rims on the other hand, do not face these issues as their tires are simply glued onto a depression molded into the rim. ALL of the internal pressure is contained inside the sewn-up tire carcass so the only downside of these was less-than-great braking performance, especially once the tire size was increased to reduce impact damage. We've probably all seen a caved-in aluminum rim, usually caused by hitting a large pothole in the road.

Carbon tubular rims these days offer performance under braking good enough, now that carbon-specific brake pads have improved, for the pros to use them pretty much exclusively with no major problems, though of course they usually have a follow-car with spares.. just in case.

The sexy look and lighter weight claims associated with anything made from carbon fiber proved too hard to resist for the bike industry.  But with so few willing to put up with the hassles of tubular tires these days, sales would go nowhere unless clincher versions of these wheels were available so every Joe and Jill Crankarm could ride around looking like a pro.

Photo from Cycling Tips

The first versions were aluminum rims bonded to carbon fiber. You might remember the ill-fated Spinergy Rev-X? They had plenty of issues, the aluminum rim separating from the carbon portion was just one of them! Most makers eventually solved that problem but there was still the thought that all-carbon clinchers would be big sellers, despite not being all that much lighter than their aluminum cousins.

Twenty years ago, all-carbon clinchers were first offered for sale. The braking surface was carbon fiber, far from ideal from a friction or heat-dissipating point of view.

Based on this piece over at Cycling Tips it seems not much has improved in 20 years?

The design of an aluminum alloy clincher rim can't simply be duplicated using carbon-fiber. The thin sides of a clincher rim (unless of course it's a disc-brake design) simply can not handle both the braking friction and temperature increase combined with the internal air pressure of the tire/inner tube.

Claims of special resins or brake pads are band-aids that can't cover up the problem. Of course this isn't a problem if you always ride in flat places and never have much use for your brakes.

We suggested from CycleItalia's beginnings the use of carbon clinchers was a bad idea. This piece at Cycling Tips suggests we were right at the time and nothing much has changed, so our suggestions stand.

*Disclaimer: While neither wheels from Ursus or Campagnolo (both official suppliers to CycleItalia) were mentioned in the linked article we can not endorse their use on our tours. Put the aluminum clinchers your bike came with back on and enjoy piece-of-mind.

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