|Radial lacing non-drive side a good thing.||JS|
Nov 7, 2001 10:22 AM
|After reading many posts concerning radial lacing of the non-drive side of a rear wheel and many respondents beliefs that it was not a good idea, I found this little nugget on Sheldon Browns site.
More and more rear wheels now are built "half-radial" with semi-tangent spoking on the right side and radial spoking on the left. Radial front wheels offer mainly esthetic benefits, but half radial rear wheels are substantially more durable than conventional ones. The high amount of dishing called for to make room for more and more sprockets has caused an increase in spoke breakage on the left side of rear wheels. This is caused by metal fatigue.
A spoked wheel relies on having all of the spokes in constant tension. A highly dished rear wheel starts with very light tension on the left side spokes. The torque of hard pedaling can cause the left side "leading" spokes to occasionally go completely slack momentarily. Repeated cycles of tension and slackness cause these spokes to fatigue at the bends, and ultimately break.
With half-radial spoking, the amount of dish is slightly less to begin with if you run the radial spokes up along the inside of its flange. In addition, since there are no "leading" spokes, no amount of torque on the hub can reduce the tension on any of the spokes. In fact, if you have a customer who has been breaking left side spokes, "half rebuilding" the wheel into a half radial will solve the problem once and for all.
I used to think that this was exotic, cutting edge technology, until I happened to look at a couple of Model A Fords in a local parade. Their wheels were highly dished inward, and were laced in the same half-radial pattern, for the same reason.
Nov 8, 2001 3:49 AM
|This much does seem logical, but Sheldon omits the other points which put me, at least, off the idea for ordinary wheels. I wouldn't lace the non-drive side spokes radially for the same reason I wouldn't lace the drive-side radially: they transmit torque from pedalling (transmitted through the hub body) and are liable to the same rotation in the flange, and the subsequent fatigue may cause failure in the spoke. Also of course there's the front wheel thing: the flange might break out. I suspect we haven't seen this much because this pattern is relatively rare.
Building such that the spokes all exit the hub from inside the flange does indeed reduce the relative dish, albeit academically, but is this desirable? I don't think so. Dish is a problem which isn't helped by making the hub width narrower, which just makes the wheel weaker still in its tolerance to lateral loads.
I suggest three reasons for this practice. The first is that many builders don't use high enough tension in their wheels generally, because it is more difficult to maintain trueness when the wheel you are building is reaches its highest tensions, and customers want trueness in their wheels above all else. (I'd prefer a slightly untrue but durable one, but that's another story). This might leave the non-drive spokes too low in tension; this problem is exacerbated by the high-dish wheels we need to accommodate all our gears.
Secondly, the preponderance of new and untested designs with few spokes and heavy rims seem to be loosening spokes all over the place: half-radial might be a crutch for those wheels which have mismatched spokes and rims. Glue in the spoke threads would probably work as well, I believe Mavic now do this and DT are selling threadlocked nipples to cater for these mismatches.
Thirdly, like all rare spoke lacings, it looks specialist and imbues the owner with the reflected glory of having inside knowledge about something.
I suspect this last is the reason most people ask for it even though the reasons Sheldon gives are fair and considered. However, I've never had this problem with my wheels which by and large have been three-cross everywhere since I learned from my mistakes with radial fronts. The vast majority of wheels in the world are like this too and likewise don't suffer. I think this problem is attributable to other things than lacing pattern.
|re: Radial lacing non-drive side a good thing.||Winnebago|
Nov 8, 2001 7:02 AM
|As a mechanic for nearly 23 years now, the issue with the radial lacing (although all valid points) ultimatley comes down to the spoke. If you aren't using a straight pull spoke, then no matter how much tension is used, either the spokes will break at the elbow, or the wheel won't stay true. Radial lacing makes for a stronger wheel vertically, but unless you have a lot of spoke tension, you will lose a lot of side to side stability. Which could really suck cornering on a decent.
Hope this helps?