orangepaint

Today I was truing a rear wheel that came in for a repair. Everything was going ok until I went to stress relieve the spokes. I usually stress relieve by placing the wheel on the ground with the axle perpendicular to the floor. I then push down on two opposite sides of the rim until I make my way around the entire wheel.

Well, I started doing this and on my second push, the wheel immediately folded in on itself. So I'm left here with a taco'ed wheel. We ended up giving the customer a new wheel free of charge. I'm still confused though. I've never run into problems stress relieving spokes this way and I can't imagine the amount of pressure I put on it would taco a rim so badly(the rim was totally ruined). Any thoughts or opinions? Simply a case of bad luck or am I being too much of a bumbling brute?

operator

Stress relieve spokes by squeezing together sets of parallel spokes on each side.

orangepaint

I used to do that, found the method I described above easier and faster...maybe I'll just go back to my old ways

BCRider

I'm guessing you also checked for quasi equal spoke tension at the same time?

Only two things I can see and granted these are both a guess. A-Grossly unequal spoke tensions could suddenly let the loose side spokes snap past the others. Or B- the rim had been previously taco'd and again the spoke tensions were w***** because of this stress of holding it semi straight and what you did was the last straw?

kramnnim

I've always done it the pushing-on-the-floor way... Was there a lot of tension in the spokes?

Whenever I try the squeezing way, nothing happens. No clicking/pinging sounds of the spokes settling...

cascade168

You are doing it the correct way. You DO have to be careful when you have a rear wheel drive side down and you lean on it. The drive side spokes are under higher tension and are already pulling hard in the direction you're pushing/leaning. The idea is to push just hard enough to get those spoked to creak. This tells you that you are bending the rim enought to unload the spokes on the underside of the wheel and they are then able to relieve any windup they have. It achieves the same thing as not stress relieving (during the build) and then getting on the bike and riding it. What happens then is that during the first few revolutions of the wheel, under load (i.e. your weight on the bike), the spokes alternately load and unload. When they unload, if there is any windup, the spoke pops/pings/whatever as the windup comes out.

The test of any method of stress relieving is riding the bike and listening for those pings. If you are doing it properly, there won't be any. Also, if you ARE hearing a lot of pings, then you wheel has likely gone out of true. You should be stress relieving a wheel at least four or five times during a build and you should be able to stress relieve it and see that the truing does not change before saying the wheel is done.

FWIW, a very good hand/wrist surgeon who also happens to be a bike hobbyist told me that that method of squeezing spokes together will very likely cause permenant nerve damage in your hands and fingers. He said it was very dangerous and should not be done without wearing some heavy leather gloves. I don't do that anymore, but I can remember my fingers aching for days, sometimes, after using that method. The "lean on the rim" method is far superior and safer.

operator

That's good to know. I use leather gloves when stress relieving.

Rev.Chuck

I prefer to hold the wheel against my forearms/chest and pull towards me. I find this has better control than pushing down against the floor. There are some rims out there that are REALLY flimsy and putting to much force in stress releiving will taco them.

Severian

Gerd Schraner, Barnette, UBI, Sutherlands, Zinn and quite a few others all suggest stress relieving in that fashion. (Hub on floor, press on rim at 9 and 3) They all also say to take it easy.

One of the other mechanics in my shop stress relieves by standing the wheel edge on (As if it were on a bike) and pressing down at the 12 o'clock position. He strongly dislikes the previous method for the reason you discovered. And he makes a good point that a wheel rarely ever sees lateral stress forces so why stress relieve in that manner?

waterrockets 

I only stress relieve like that with wheels I've just built myself, and very gradually.

For tune-up wheels, I squeeze adjacent pairs with my shop gloves.

My guess is that there were a couple loose spokes that weren't applying any tension when needed.

cascade168

I'm sure that there are plenty of folks over on the r.b.t. forum would strongly disagree with "rarely ever sees lateral stress forces". And, I do, too. Every time you go around a corner you are putting lateral stress on a wheel. If you are going downhill fast and take a corner you are putting some serious lateral stress on a wheel. Going straight is easy for a wheel, compared to corners. Corners are what really put a wheel's design to the test. Any increase in lateral stiffness makes it easier to take a corner at a higher speed. Look at the promotional literature for any high end racing wheel and they will always tout the lateral stiffness properties of the wheel. For good reason.

The reason you stress relieve in that manner is that you have to completely unload the stress on the spoke to allow it to unwind, if necessary. The method of standing the wheel on edge would do that just fine. How squeezing spokes together can completely unload a spoke is something that does not make any sense, and the prime reason I don't do it anymore and think it achieves nothing, other than sore hands. Squeezing spokes together just increases the load on the spokes, no matter how you do it. How is that going to allow a spoke to unwind? ...(again, the purpose of stress relieving)

christama

I usually put the wheel on the edge of the work bench, at 12 o'clock, then I put the other edge on my hip at 6 o'clock, and then apply slight pressure at 9 and 3. I've seen even veteran mechanics do what the OP, and this is just an easier and safer way to me. I never get a ping on a test ride.

Wordbiker

I use boxing gloves when stress-relieving.

Hey, it beats an assault charge.

Bobby Lex

My guess is that the spokes were overtensioned to begin with and the lateral de-stressing forces caused it to collapse.

Bob

MnHPVA Guy

I've seen this happen several times. Sometimes from stress relieving. other times from the wheel getting a side load while on the bike. In every case there were 3 common factors.

1. Tangential spoking, x5 on a 48 hole, x4 on a 32 or 36 hole or x3 on a 28 hole.

2. Tightly built wheel.

3. Not a beefy rim.

I don't have time to go into a long explanation of the effect of combining 1 and 2. But, does it fit your scenario?

Joshua A.C. New

The OP's experience is beyond mine, so I won't hazard a guess, since others' explanations seem plausible to me.

I put one side of the wheel against the work bench and the other end against my belt buckle. Then I press on the sides, rotating the wheel. I get some pings, retrue, and do it usually once or twice more. One time, it took four or five times around. I suspect it has a lot to do with the nature of the rims and the lubing you've done to the nipples*.

* Lube nipples. Hee hee!

urbanknight

+1 The ground method can ruin cartridge bearings.

The tension must have been high or the rim was already warped to do that during stress relieving.

alecw35

Ive had a couple of wheels fold up on pressing them.

I shouted at them.... you stress releiver...

well a different word