Sunday, April 15, 2007

A Discussion of Super Thin Spokes

There is one known issue with spokes with very thin middle sections like DT Revolutions. At some point while tensioning the spokes, the force required to turn the nipple on the spoke will become greater than the force required to twist the spoke at its middle. Beyond this point, it will be impossible to turn the nipple without temporarily relieving the spoke tension. This point will occur at a spoke tension that is less than optimal. The result is that the wheel will not be as strong as it should be.

It is possible to force the rim inward enough to relieve the tension so the nipple can turn. This will allow the wheelbuilder to achieve the optimal spoke tension. The downside is that this is such a pain-in-the-butt that many wheelbuilders don't do it. It will also be a pain-in-the-butt should you ever need to true the wheel.

I believe that most wheels built with Revolutions are built with less than optimal spoke tension, and durability is usually sufficient. However, if durability is sufficient with, say, 32 Revolution spokes at less than optimal tension, it will be just as sufficient with 28 15/16 spokes at optimal tension. The weight of the spokes will be nearly the same.

I won't build with Revolutions any longer because I won't build with lower spoke tension and I don't want the pain of dealing with temporarily relieving spoke tension just to turn the nipple. Of course, should the opportunity arise, I wouldn't be opposed to using them on the left side of the rear wheel since those spokes are never at high tension.

Thursday, April 12, 2007

Touring Front Derailleur Update

There is a new problem when using the Shimano Deore LX front derailleur with the Sugino XD600 (or similar) crank. The latest version of the LX front derailleur (and most of the other current Shimano front derailleurs) has a new cage that is more profiled with larger shift ramps than before. It is optimized for Shimano MTB cranks with 44-32-22T chainrings. When using it on the XD600 crank with 46-36-26T chainrings, the inner portion of the cage will hit the middle chainring when shifting to the large chainring unless the derailleur is mounted VERY high. When mounted high, the shift ramps are in the wrong places and will rub against the chain in many gear combinations thus requiring constant trimming.

The current road triple front derailleurs from Shimano have a similar cage profile. They are now all pretty much limited to use with Shimano's standard chainring combinations. This is true even with a friction shifter. As a result, I have now switched to Campagnolo triple front derailleurs. Their cages are also profiled but not nearly as much as Shimano's. They work extremely well with both friction shifters and Campagnolo Ergo shifters. The cages are wide enough that trimming is seldom required to avoid chain rub.

This trend makes me want to buy up any NOS straight cage derailleurs I can find on eBay. Those old derailleurs are very light, durable, and functional. They just don't index well with STI shifters.

Tuesday, April 03, 2007

Heron Site Down

The Heron Bicycles website is currently down because of problems at our site host. Hopefully, the problems will be resolved soon so we can get the site back up. I'll post any news here. Thanks for your patience.