[CR] Fw: Re: Strong/Longlived Wheels

From: Pacific Coast Cycles <paccoastcycles@sbcglobal.net> Subject: Re: [CR] Strong/Longlived Wheels To: "donald gillies" <gillies@ece.ubc.ca> Cc: gretchbzz@earthlink.net Date: Sunday, August 23, 2009, 10:19 PM

Don, you show a great understanding of wheels and the forces that make them work.

I would like to comment on a few statements you made. The guage of the spokes has nothing to do with the resistance of a wheel to pothole deformation. The first line of defense against sharp edged impacts is tire cross section. I am assuming proper tire inflation here.

The guage of the spoke has more to do with the life of the spokes. Too light a spoke for the rider or the intended use will result in shorter spoke life.

The use of double eyelets is something I've given a lot of thought to. A double eyelet weighs one and a half grams. That's forty eight grams for a thirty two hole rim. Forty eight grams is about ten percent of the weight of a sporty rim. That forty eight grams would be better spent in reinforcing the area of the rim where the nipples reside.

Mavic Open Pro rims often crack when built for eight, nine and more speed wheels. Indeed, the rear wheel is the only one I've seen crack. And that is only on the right side. In order to put dual eyelets in the wheel, the hole in the rim is made bigger. On dual eyelets, the size of the "load spreading eyelet" is not big enough to really do that job. If you want to use another piece to spread the load, and that does work, a washer as used by Martano and others actually is big enough to effectively reinforce the load concentration.

Even though the double eyelet, when pulling through the rim, pulls through the top or inner layer also, I don't get much comfort from that. Distributing that forty eight grams around the rim in the area that is pulled on by spoke tension prevents the pull through. The hole is smaller and the wall can be thicker for a given weight.

You can tell I'm no big fan of rims sporting eyelets. Still, there is an emotional appeal to eyelets and people seem to feel comforted by them. Some people claim that they are a better home for the nipple. There may be some truty in that, but in general, I don't see much benefit to the nipple especially when compared to a crack prone rim. Alloy nipples sometimes lose their heads around this coastal area, but that doesn't seem to be aleviated by using eyelets.

One of the things I love about bicycle wheels is that they seem almost like a living thing. There is so much to think about with regard to wheels. Another thing that's pretty cool about them is that almost anybody can build a wheel even if they don't think about the deeper concerns that are designing wheels to a given purpose or rider.

In closing, I will say again that it is the tire's cross section in relation to the obstacles put before it, in relation to the weight it carries, that will make a wheel resist denting, or not.

Chuck Hoefer
Vista, California USA