Saturday, October 13, 2007
UNDERSTANDING DELTA TRIKE WHEELS
After having my trike wheels custom built the spokes started working loose every few weeks because the shop copied the light duty wheel’s offset dish pattern that came with the trike. A much steeper angle on the disc brake side, like a bike's front disc brake wheel.
There is a theory that says that the spokes on the disc brake side of a bike wheel needs to be shorter because the brakes will pull the spokes on that side first, yet hubs do not twist. The only reason that the spokes need to be shorter on that side is to make it fit in the wheel well.
Some people think that front wheel spoke tension should be less than the rear because they think the high tension will collapse the wheel. Yet the rear wheel of a bike is always asymmetrical making it much less stable when it is subjected to high torque..... One side is inherently tighter, so of course it will collapse.
JOBST BRANDT (The Bicycle Wheel): The only reason that any bike wheel is built lopsided is to make it easier to build a frame that will hold both wheels in alignment with each other. In effect a lop sided wheel (asymmetrically dished) is only half as strong as one with all the spokes the same length. (pages 32 & 39
PIPPA GARNER (builder of quadrocycles): Well, yeah. I retightened the spokes on my canted wheels twice and finally got rid of the pinging noises, but I had the problem on 2 different cycles with canted wheels, one built by Varna in Canada, so the spokes must be tighter than what is considered conventional in wheel building. Certainly the application has something to do with it. There's no question that asymmetrically tensioned spokes are subject to more stress than wheels with the rims centered between the flanges.
HASE DELTA TRIKES: *yes, all spokes have the same length (172 mm) and so they also have the same tension. A symmetric bike wheel is the strongest solution, even with disc brakes. Both flanges on our wheels are the same size. The Ez3-usx is a cheap copy of our trike. Best regards Rüdiger Knopp Diese, hase-bikes.com
LIGHT FOOTCYCLES: Smaller wheels are much stronger in almost all respects, mostly lateral stiffness. They would suffer less distortion from braking, as well, because of the steeper angulations and shorter spokes with less give. Rod Miner Lightfoot Cycles Inc. 179 Leavens Road, Darby, MT 59829 USA , lightfootcycles.com
GERD SHRANER (the art of wheel building): for years I worked with out a tensiometer, being under the false impression that instinct and experience were enough. When I finally started using one I discovered that even my mood on any given day gave me different result. To adjust your rim off center on the axle, just visually determine the spoke length. Then open the rim calipers on the truing stand and let only one side touch the rim. You may need some new nipples because they could disintegrate during adjustment. The tension for 14guage stainless steel spokes can be much higher than for the usual 15guage aluminum. High tension can collapse a wheel if made with cheap rims. BFR's are the best for lateral forces, but deep V rims are the best for high torque.
BROX QUADROCYCLES: On wheels with low spoke tension on one side you may experience the disc brake pulling the tight spokes before the loose side. Centering the rim between the flanges will eliminate this action, but you still need higher tension on the spokes because of the compression factor from lateral forces. We use symmetrically dished wheels with disc brakes, and box wall rims. Brox.co.uk
GREEN SPEED TRIKES: We generally build our rear wheels symmetrically about the flanges (i.e. spokes the same length on both sides) to take the extra side loading trikes put on the wheels.
KEITH BONTAGER (bicycle engineer) The disc brake side spokes should be slightly looser, yet still have the same length. However for light duty use a 20” wheel can be the same tension as the other side.
BOB BRYANT (RCN magazine): In a hard turn most of the weight goes to the outside spokes so they should be at least as tight as the inside spokes, because after all the axle does stand on the spokes. The reason that Sun bicycles built the wheels like bike wheels is simply that they couldn’t afford to build a new wheel-building machine and still keep the price down.