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Wheel dish & Spoke tension???(11 posts)

Wheel dish & Spoke tension???jaybird
Mar 28, 2003 7:26 AM
What are tolerances for a wheel being rideable if out of dish? I just built a bike for my wife and the wheels that came with it are true and round but the front one is about 1/4 of an inch off in the dish. My truing stand is calibrated.

I have a spoke tensiometer from a friend, but I am not sure how to interpret what I am reading. The tensiometer readings are relatively close but when I put check the readings with the tensiometer chart, i get a result of 10-17 kg difference in the tensions. That seems like a lot??

Since it is off dish by such a little amount, there was no real problem setting up the brakes but I am just wondering how serious this is? I dont know if I have the guts to try to do this my self... Would I be able to fix it by a quarter turn loose on one side with a quarter turn tighten on the other? I have built wheels before but for some reason i am a little nervous about this...

Should I just pay the 10-20 bucks to get someone to do it for me???
re: Wheel dish & Spoke tension???sprockets2
Mar 28, 2003 7:53 AM
If your front wheel is 1/4 inch out of "dish", that is too much-and totally unacceptable. If you cannot do the corrections yourself-which is really not too hard if they used the correct spokes-take the wheel to someone.
re: Wheel dish & Spoke tension???jaybird
Mar 28, 2003 8:14 AM
What is the best way to attack it? do I loosen everything and just start from square 1 or is there a better way, maintaining the tension on the spokes?
re: Wheel dish & Spoke tension???curlybike
Mar 28, 2003 9:03 AM
Make sure that you verify that the dish is actually wrong. touch one pointer of your stand to the rim and then flip the wheel in the stand. the difference is 2x the dish error.On the side that is too close to the drop out, loosen the nipple, 1/4 turn and tighten the other spokes 1/4 turn. Repeat as required, this should keep everything pretty close. If you use smooth jawed pliers to grasp the spoke, you will have less problem with torsional wrap over the length of the spoke. Keep flipping the rim until it looks the same to the one pointer. You really should be using a dishing gauge, as there are variables that can exist in the hub that will deceive you. Place the hub in the stand and place one pointer close to the rim, now use a cone wrench and gently turn the axle in the stand, while holding the wheel in the stand. Does the gap between the pointer and rim change? If so, you will have trouble getting the dish correct by flipping the wheel in the stand.
re: Wheel dish & Spoke tension???sprockets2
Mar 28, 2003 9:42 AM
First be darn sure that it really is "out of dish"-you could really screw it up if you are wrong about that. I just stress that point as it is SO amateur that someone tried to pawn off such a wheel on you. It is hard to believe. I have seen low tension machine built wheels, but they have never been as far off as yours seem to be.

There is no easy way to do this that will guarantee that except for the tension/de-tension step, the wheel will remain in an otherwise sound and ready to roll condition. You don't want to completely undo the tension, but there is no sense in trying to otherwise keep the wheel in some hypothetical state of readiness. You are just going to de-tension one side and take it up on the other, if all else is normal. Someone who builds wheels for a living might be able to pull off swinging the rim over without messing everything up, but there is a pretty good chance that mere mortals like us may find that the wheel is going to loose some of its desired characteristics, and we are going to have to work to get them back. Specifically, you will need to true/round check the whole wheel again, as well as stress relieve, but it is worth it.

If the tension is high in the wheel, you might want to end up undoing the flatter side by as much as a full turn plus perhaps a bit more. I cannot predict how much the rim will travel with each adjustment, but you want to work in rather broad strokes. You don't wan't to micro-adjust the tension by loosening on one side by just a touch and then tightening the other. Pretty soon the side that you are moving the rim toward will be too tight. Work in large quantities, like maybe a half-turn. Check tension and round, and true, and adjust as necessary (tightening toward the desired rim-direction-of-travel side would be the favored truing adjustment).
Do it yourself. It's not that hard.Ken of Fresno
Mar 28, 2003 9:08 AM
Come on. If you've built a wheel before a simple 1/4" dish adjustment is nothing. Just loosen the side that is too close 1/4 turn at a time and tighten the other side until the dish is right. One or two times should be enough to get 1/4". Don't know what to say about the tension difference. I've heard that many "factory" wheels can vary a lot as far as tension goes.

Best of luck,
Ken
Do it yourself. It's not that hard.jaybird
Mar 28, 2003 10:11 AM
That is what I initially thought but it sounded too easy and logical.

I think the tension thing scares me becuase I have never used a tensiometer before. Perhaps I have too much info and that has lead me astray...

I also just remembered that there is a spoke with a small bend in it, si I will have to replace that one anyway but that shouldn't have much net effect on the whole scenario. Right???
Do it yourself. It's not that hard.russw19
Mar 28, 2003 11:27 AM
One last piece of adivce I have is to double check your lacing pattern as well. Make sure everything is right before you run the possibility of messing things up further.

Check everything over before you make changes. Remember the old axiom of measure twice, cut once... well you kinda get the point. Look at it all first before you make a change. Check your truing stand and make sure that's not the problem. Check to see that your fork is properly aligned... all that...

Russ
re: Wheel dish & Spoke tension???cycling6500
Mar 28, 2003 12:02 PM
Check with your wheel manufacturer for the tension specs. I have a Park tension meter, it uses a conversion table to convert the reading to Kgf for different spoke type.
It is not difficult to do it yourself but require patience.
Do not use the dish with the tire on the rim unless the ends sit flat on the rim itself. I cut both ends of my inexpensive Park dish gauge so that the ends sit flat on the rim without having to take the tire off.
It is always nicer to have everything according to specs. Good luck.
Dish / tensionEl Kabong
Mar 28, 2003 1:45 PM
Jaybird, if you've built wheels before, getting the dish and tension right here should be easy. Worse comes to worst, you back all the tension off, and then you're at the point in building where you've just finished lacing -- but you probably won't have to get to that point.

1/4" off is a lot, and it certainly should be fixed. When you say that there is a 10-17kg difference, is that between the two sides of the wheel, or between different spokes on the same side? If the former, well there's your dish problem! If the latter, assuming your desired tension is in the 90 - 100 kg range (and that's probably right unless you're using a very light spoke) then you're up to around 20% variability, which seems sloppy.

I would do what it takes to dish the wheel better, and even out the spoke tension if you can. If your overall tension is low, try just bringing in the one side without loosening the other. If your overall tension is about right, you'll have to work both sides. Either way, you'll have to do at least some truing at the end, but that's no biggie, right?

El K.
Do it, man!Fredrico
Mar 28, 2003 3:09 PM
If the spokes are all of equal tension on each side, and the wheel is true and round, all you have to do is loosen all the spokes on one side and tighten all the spokes on the other side, BY THE SAME AMOUNTS on each side, and the wheel will not go out of true. You can tell the relative tension of the spokes by plucking them. If they make the same tone, they have the same tension. The freewheel side will be a higher tone because the spokes are shorter.

Just loosen the non-freewheel side all the same amount, at least a half turn, then tighten the freewheel side slightly less, a quarter of a turn. Go around the wheel once, check trueness and spoke tension by plucking or squeezing two together. Put the wheel on the floor and de-stress the spokes by pressing the wheel down simultaneously on both sides, going around the rim. That'll seat spokes that got wound up when you turned the nipples. Hearing creaking noise when you're pressing on the rim is a good sign that the spokes are seating. The tighter the spokes get, the easier they'll twist, screw up your tension readings, and when they seat on the road, the wheel will go out of true.

As the spokes get tensioned, the nipples become hard to turn, especially on the freewheel side. So I usually dish the wheel an eighth of an inch too much, then bring it back to the center by tightening the non-freewheel side spokes, which are much easier to turn at this stage. Also use thin oil on the nipples. The worst thing you can do is twist off the flats on a nipple that is too tight and won't move. Then you have to detension the spokes to replace the nipple. Otherwise, the wheel will very likely pretzel.

I think you'll be surprised at how easy it is, once you get into it. Put aside an afternoon. Patience is essential.