Trplay, some basics of wheel/spoke loading have to be well understood before analysing what that BMX guy is doing to his wheels. If he has better rims, and doesn't ride thousands of miles on those wheels, they will never fail him, loose or tight. If a spoke breaks at the hub, it is too loose. If the spoke is too loose, the spoke will continually flex at it's 90deg angle when it loads and unloads as the wheel turns, and just like when you keep bending a tin can it will crack and break. If it is tight enough, it won't keep flexing like that. That's why loose spokes break at the hub end. When a wheel fails because a nipple pulls through the rim, it is because it was too tight for THAT rim. Probably a cheap rim, too!
That BMX guy simply bent the rim by hooking it on those fence spikes as he fell of the fence sideways. Almost any wheel can be put back into serviceable shape by stomping it! But it won't be perfect or pretty! Also, he is not subjecting those wheels to as much SIDE loading as we do in a hard corner (I know I will take flak for that comment!!!), especially if you weigh over 200lbs. That video is a good example of just how strong wheels are in radial loading.
Tennbent is here and we have been discussing this thread and spokes, as well as playing with his Baron's chainline. This morning we wanted to check the consistency of the spokes on all of my wheels and his. I must make a public apology to Jim Aliano for my comment about "junk" in regards to his wheel figures. My original reading of 209lbs was for just one spoke on HS. My right hand wheel on HS was reasonably consistent and tight, but the left wheel was all over the higher end of the spectrum, ranging from 180lbs to over 400lbs! Why? Because it is the wheel that gets leaned on the most when I bicycle HS! Bottom line is that the wheel is still straight and true! Stresses have obviouly redistributed the spoke loading, but they were all tight enough to not let the rim move even with different loading. This is a new one on me, but now I have to redo that wheel!
When I read the one spoke at 209lbs, I thought it was a bit low for what I normally use. I don't usually bother with actual "pounds" numbers, but just go by the Park meter's numbers. It read 23, which is 95Kgf=209lbs. Normally, I run them up to about 26, which is about 300lbs. So, that one spoke may have met with Sheldon's recommendations (200lbs), but not for my wheels for trike use.
Also, on the Cat forum, Elso said that Mark told him to use 110lbs as a target figure. As Hippy said, that is for sure a mistake. It should read 110Kgf (kilograms of force), which is 242lbs of tension! This would be consistent with the rear wheel he made for me last year.
The rear wheel on my Slingshot measured from a number 8 on the meter (not even on the chart) to about 21=167lbs. Both on the drive side! Wheel is straight as an arrow.
The point to be made here is that wheel building, truing, spokes and tensioning are all part of a very complex formula to make a good, strong, long-lasting wheelset. It takes tons of patience and practice after reading a lot of the basics. Until you have successfully built a wheel from scratch, it is hard to understand what is gong on with them. Until you do understand those basics, understanding why a Walmart special can withstand a plunge from a roof top into a driveway with no broken spokes, and a Mark Power-built wheel will fail after 10,000 miles of riding along the beach, will be hard!
Other than being crushed or material failures, there are three main ways a wheel fails. First is that the head of a spoke breaks off at the hub after running loose for a long time. Second is that the nipple pulls through the rim hole. Third is if the threads on the nipple pull out. The last one is pretty rare, but the first one is the most common.
Discussing why incorrect toe-in will wear out tires is easy to understand, but, without a proper background of reading the basics and hands-on practicing, wheelbuilding and proper spoke tension are not. A lot of the charts and other diagrams in Jobst's book make my eyes glaze over, but the sections about the basic principles are a good place to start to grow your undertstanding of what is going on and why. Trying to discuss such a complex subject on a forum with words only, and no illustrations, or hand gestures, makes it even harder! And FRUSTRATING!
