|Double butt spokes question||HAL9010|
Nov 30, 2002 12:45 PM
|I need to rebuild my rear wheel. It has a disk brake (set up for road, rim & tires). would double butt spokes work well on both sides, or one only? I thought that a double butt would move a large portion of stress to the thinner more flexible center section where it could handle it better than at the spoke head bend where the breakage happens the most.|
|works for both sides...||C-40|
Nov 30, 2002 1:40 PM
|14/15 DB spokes can be used anywhere. They will produce more durable wheels than straight gage spokes, if built correctly.
14/17 gage "Revolution" spokes may be marginal for the right rear, where normal tensioning can cause them to stretch. They also wind up more easily which makes them more difficult to build and true-up later. I've had wheels with 28H rims and Revolution spokes on both sides in the rear. Had no problems in 4000 miles of use, but I'm a lightweight who's easy on wheels.
|a good compromise||cyclopathic|
Nov 30, 2002 4:58 PM
|is to use WS DB 14/15 spokes. They actually more like 14/16, middle section 1.7mm vs to 1.8mm 15G. Stronger then 14/17 lighter then DT DB14/15 (and saves wooping 20g per wheel!)
With respect to Revos (or WheelSmith XLs) you can still use them on drive side. The trick is to use DB 14/15 for trailing spokes only, I've build a set like that. No, don't come half year later and ask me to true it. Al nipples + Revos bad combo IMHO.
On disk wheelset the only place 14/17 can be used is front non-disk side, that's the rule I've been told to live by.
Nov 30, 2002 6:19 PM
|How do you "transfer stress" in a spoke? Do you mean that the force per unit area will be greater in the center section? Yes that is true, but the force on the rest of the spoke will be the same as if it were a straight gauge spoke if the wheel is at the same tension. The head of the spoke (or the threaded end) cannot "tell" what the diameter of the center of the spoke is. Per C-40's comment, there is no place that a 14/15 spoke can't be substituted for a straight gauge. Those who recommend straight gauge spokes for a stronger wheel are completely ignorant of the art and science of wheel building. The only advantage of a straight gauge spoke over butted is cost - it's more expensive to produce butted spokes. At worst, butted spokes build a wheel just as strong as a "straight gauge wheel." Many would claim with justification that butted spokes actually build a stronger wheel, as they are better at distributing forces due to their higher compliance. At any rate, it is EXTREMELY rare to have a spoke break in the center section, and such a break is invariably a defective spoke.|
|What a DB spoke does:||Alexx|
Dec 1, 2002 7:04 AM
|Since the center section is thinner, it will elongate more onder stress, which, in turn, causes less "twisting" action at the bend by the head. DB sokes, therefore, are much less likely to fatigue at that point (always the worst place for strain, since it is under bending forces, rather than tensile forces). In the end, a DB spoke is actually weaker in a tensile failure test, but the advantages are only seen after several million cycles of stress when fatigue will occur.|
|Straight guage spokes are easier to build with because||eddie m|
Dec 1, 2002 7:20 PM
|they wind up less as you bring the tension up. Tht'a especially important on the drive side of 9 speed wheels, which need need to carry almost all the tension for the whole wheel. 9speed wheels are stronger if you use lighter spokes on the non-drive side, becuase the lighter guage spoke will stretch enough that it will never go slack. Double butted spokes may be stronger in theory, but in the real word straight guage spokes are easier to build and make perfectly acceptable wheels.|| |