Sunday, November 21, 2010

Need Some New Wheels

Bicycle wheels are somewhat like wives.  The flashier and more exotic you pick, the more likely you are to have trouble.
Last winter, I picked up a flashy, exotic rear wheel at a good price.  This was a Mavic Cosmic Elite, a relatively heavy and solid wheel, deep V section, primarily sold as a triathlon wheel.  I was assured that this was Mavic’s strongest wheel.  I had kept the wheel in perfect true and spoke tension was perfect, but I broke a spoke anyway.  For reference, this wheel is built with 20 bladed straight-pull spokes.  I had a Mavic Aksium front wheel that more or less matched, but I had no problems with this wheel.  The bottom line is that 20 spokes are just too few for everyday riding for anyone.
Those of you who know me know that I am not a small person.  I’m not oversized either, but even at my ideal weight, I’ve got over 200 pounds on the bike wheels, not including the weight of the bike.  So I need a strong wheel.
What makes a strong bicycle wheel?  Simply enough, a lot of spokes. 
A bicycle wheel is held together by a number of spokes, all with a significant amount of pre-tensioning.  Most wheels have spokes with a pre-tension of somewhere around 200 pounds.  If the spokes are not tensioned, they will be tensioned and de-tensioned with every revolution of the wheel. This will result in a very premature failure of the spoke.  The more spokes on a wheel, the less stress with every wheel revolution.
The other problem with wheels is the manufacturers’ continued escalation in “improvements”.  We started with a 5-speed freewheel and have continued to escalate to an 11-speed.  In doing so, we have sacrificed the strength of the rear wheel.  Why?  To get the extra cogs, the right side flange had to be moved closer to the center of the rear hub, decreasing the bracing angle.
Let’s look at a few pre-built wheels.  I had a pair of Neuvation wheels at one time.  Great wheels, probably the best rolling hubs I have owned.  But there just weren’t enough spokes.  Most of the pre-built wheels fall into this category:  high-performance, lightweight, made for 130 lb riders on smooth roads.  Performance Bike has their Forte Titan wheels.  Same problem, 16-spoke front, 20-spoke rear.  About half of what I need.
So I am getting ready to build a new wheelset to my specifications.  Very strong, reasonably economical, reasonably fast.  I have decided to start with Shimano 105 hubs, somewhat of a benchmark for hub construction.  I had toyed with the idea of Phil Wood hubs.  These are arguably the most bullet-proof hub ever, but they cost a bit more than the Shimano.  They’ll last longer, but probably not five times longer.  The Phil Woods do cost five times more.
For the rims, I have chosen the Velocity Synergy.  This is a 19 mm tall, 23 mm wide box-section rim.  These are a bit more forgiving than the deep-V section aero rims.  I had considered the Mavic Open Sport, a similar rim.  However, the Velocity is a welded rim instead of pinned.  In addition, the Synergy also has an off-center version available.  Why is that important?  Used on the rear wheel, the off-center design can even out the spoke tension in the rear wheel.  The rear wheel right side spokes are typically tensioned at twice that of the left side spokes.  By re-shaping the rim and offsetting the spoke holes 4.0 mm to the left, this changes the ratio from 2:1 to roughly 4:3.  The wheel is more evenly tensioned and spoke breakage is greatly reduced.
I have decided to forgo any exotic spokes and go with a straight 14-gauge spokes.  The wheels will both be laced 3-cross.  No more radial lacing for me.  There’s a variety of anecdotes regarding the stiffness of radial laced wheels versus 3-cross.  Personally, I think the 3-cross give a smoother ride.  However, I will qualify this by stating that all of the wheels that I have ridden with radial lacing have had deep aero-section rims which are much stiffer vertically than their low-profile box section counterparts.
I’ll post building progress of these wheels later.  The plans are to build these while I’m on vacation between Christmas and New Years.

1 comment:

  1. Let me know when you're ready to test out those new wheels - need to see if we can get past that 7 mile mark next time.