_ForceD_

I’ve always been OK with lateral (side-to-side) wheel truing on my Park truing stand. But, I’ve never been able to master radial (up-and-down) truing. I’ve laced a few wheels for my own use. But was only marginally successful at the radial truing. What is the trick to it? I’ve got a rear wheel on the stand now that I assembled from a bunch of leftover components more or less for practice. It’s laced, tensioned, dished, and at the moment pretty true laterally. But there are a couple of significant radial ‘humps’ that I just can’t seem to work out. I’ll equally loosen the spokes on either side of the hump, and tighten the spokes in the hump…but then the lateral true goes away, and tensioning gets uneven too. I adjust for the lateral and the humps come back. It’s a Catch-22. — Dan

smd4

With some projects it's hard for me to imagine what I would do, without having my hands on it and actually doing the work. This is one of those cases. Like trying to tell someone how to mix a proper color of paint--I sort of have to do it myself. But I do wonder why you're loosening any spokes? That's something I would do only when truing for side-to-side variances.

Trakhak

Detension the spokes until they're almost slack---then concentrate primarily on radial true and only secondarily on lateral true as you slowly work toward the target tension level (or levels, for rear wheels).

To put it another way, get the wheel as radially and laterally true as possible at low tension---then slowly bring the spokes up to tension while maintaining the radial (especially) and lateral true. And don't work on one section at a time---tension the spokes in sequence from the first (I start at the valve hole) to the last, over and over, continuing to work your way around the wheel.

As the spokes approach full tension, you should end up having to do only the most minimal tweaks here and there, if at all.

cyccommute 

You don’t “equally loosen” the spokes on either side of the hump or dip. You should work out from the center of the hump with large spoke movements in the middle and progressively smaller spoke movements as you move out away from the center. Below comes from my class on wheel building. It’s stolen from a 1986 wheel building series in Bicycling magazine.

The blue arrows indicate 1/2 turns while the red arrows indicate 1/4 turns and the green arrows indicate 1/8 turn. You may need to move outward from the hump or dip further than 2 spokes. Adjust the turns of the spokes accordingly.

One thing to remember is that the wheel is dynamic. Ric Hjertberg, who authored that series in Bicycling, said that think of the wheel as a balloon. Poking it in one spot may cause it to change in another spot. Adjusting a hump in one place may cause a hump or dip in another. Check the entire wheel after a radial adjustment because the wheel may have changed.

_ForceD_

This sounds good. Are you saying to “detention” the whole wheel, or just spokes in/around the humps?

Dan

rm -rf

I was surprised by this method of changing a pair of spokes by turning each with the same rotation. I assumed that the non-drive side, that's under much less tension, would need a different amount of rotation compared to the drive side? (non-disc brake front wheels would be symmetric, of course.)

pdlamb

Sounds like you've got a use rim which may have some bends in it. If that's the case, you need to start with the understanding that you may not be able to get a true wheel with even spoke tensions.

I think Trakhak has the right idea. Ease off on the tension, get the radial true as good as you can. I'd add tighten things a little at this stage, and then you can start the lateral true process tightening one side and loosening the other (unequal turns, since it's a rear wheel) while maintaining radial true. Lather, rinse, and repeat until you've got the average tension up where it needs to be (or as close as you can get without popping the tighter spokes at the radial bumps).

grumpus

Are you sure it was round and flat to start with? If not you won't be able to get it round and true and still have even tension.

Quote:

Originally Posted by _ForceD_

I’ll equally loosen the spokes on either side of the hump, and tighten the spokes in the hump…but then the lateral true goes away, and tensioning gets uneven too. I adjust for the lateral and the humps come back. It’s a Catch-22

For a high spot don't loosen, just tighten the three or four nearest spokes - a turn for the inner one/two, half a turn for the outer two. Likewise for a low spot, only loosen. Then squeeze all the spokes hard, roughly adjust sideways runout, check again for hop/dip.

Trakhak

Completely detension the wheel, to the point where all the spokes are loose.

Check that the spokes are threaded into the nipples with the same number of threads showing outside the nipple (assuming all spokes are of the same correct length).

Then follow the plan I described in my earlier post.

JohnDThompson 

Concur with cyccommute above, with the caveat that rim quality should temper your expectations. Cheap rims tend to be less true and less round than high-quality rims, and no amount of playing with the spokes will get them perfectly true, round and reasonably evenly tensioned. "Pick any two," as they say. And used rims of any quality may have suffered damage that prevents them from being acceptably true, round, and evenly tensioned.

cyccommute 

Roundness is a function of all the spokes in the region being off. The different tensions of the drive/nondrive side really doesn’t matter.

grumpus

There is a difference, but you'll balance that out when you true it, after you've got it mostly round. Then do it again, and maybe one more time.
Clarification: "when you true it" refers to lateral alignment.

FBinNY 

The secret to radial truing is to NOT INTRODUCE radial error in the first place.

You start with all the spokes having the same length, which implies that the wheel will automatically be radially true if you preserve that. Of course, that's impossible, but with a small effort you can keep it within 0.5mm or so.

Use a screwdriver with a depth pin to pretighten spokes equally. Or use your thumbnail at the 1st thread as a stop. Then add equal turns to each spoke by degrees until the wheel nears half tension.

STOP ---- DO NOT ALIGN, DO NOT USE TENSION GAUGE.

Set the elbows by squeezing pairs across the wheel, or by compressing it between two 12" or so pots. This is the single most critical, and overlooked step. Skipping it will have you overworking the dough ( so to speak) realigning the wheel constantly as the elbows relax under increasing load.

Now, you may more tension, and do a very rough true, using minimal turns on wide areas to get it to where it's close enough to meaningfully check for hop. Add tension until no more than 3/4 target and true for radial, while keeping wobble to a few mm. You should be working in adjustments of less than a turn at worst.

It's important to dial in radius where there's some give because the rim has to move along the circumference as it's radius changes.

Now, with a fairly tight radially true wheel, you can add tension as you bring wobble within tolerance. Again spread all adjustments among multiple spokes, so you're not causing tension variance. Do a stress relief and final true.

If you follow this process, you'll automatically end up with a true evenly tensioned wheel, and can confirm by spot checking with the tension gauge.

Final note. On dished rears I find it easier to go to close to final tension in an over dished condition. Then I bring it back using left spokes ONLY which adds the last but of tension without needing to turn tight nipples.

Unca_Sam

Do you have old spokes and nipples? I don't remember where I saw the directions for this tool, but it helps get the nipples threaded on by the same amount. Use a little threadlocker on the nipple you're using as the depth gauge. You can thread the build nipple on the tool through its bottom and tighten it until the spokes meet, then you'll unscrew your tool and do it again. You could probably knock the threading off of the tool with a file to speed building up a bit too.

Old spoke nipple driver

Unca_Sam

Duplicate post

Russ Roth

Cyccommute's pic quote says it but it shouldn't be overlooked, when making the wheel round don't always just tighten to pull in high spots, loosen spokes to let out the valleys in equal measure. I'll often do 2-3 small high spots and then look for the lowest spots and take care of a couple. As he mentioned, what you do in one spot can effect others. But also just pulling in high spots can over tension the wheel, you have to do the lows to let everything move. And just as you tighten the center pair more than the outer pain when eliminating a high spot, loosen the center two more than the outers when eliminating a valley.

FBinNY 

Before you start you have to understand the problem.

There are two distinct issues that present as radial untrue, aka "hop".

You can have a round wheel with the hub off center, or an egg shaped wheel with a high and/or low zone. (or an oval with 2 high and 2 low areas).

Then consider what happens when you tighten a spoke-----Where the spokes are strong and the rim radially compliant, shortening a spoke moves the rim in. OTOH where the rim is radially stiff, ie. a deep aero rim, it will not flex inward, and tightening a spoke just stretches it more.

These are polar examples, but real life is a spectrum between extremes. But thinking about it is useful, because understanding the rim helps define your course of action---- pull in hop or move the hub.

Also, put tension out of your mind for the moment and focus on length, since it's length, and not tension that locates the rim.

As noted by others, it's helpful to detention the wheel. I don't go to zero, but take it to about half or 2/3rds to reduce the likelihood of taking a spoke beyond yield.

Dan Burkhart 

Your assumption is correct and a point many don't seem to know. To illustrate this, if you are bringing a wheel that is already true up to final tension by going around the wheel turning all nipples equally, the rim will move toward the non drive side. The more radical the dish, the more pronounced the effect.

cyccommute 

While what you say is true for lateral trueness, it is incorrect for radial trueness. If a wheel is out of round, it is because the spoke tension is wrong for the area where the wheel hops or dips. The whole area has to be addressed to remove the hop or dip. After the roundness has been addressed, the wheel’s lateral trueness needs to be addressed but that shouldn’t cause a wheel to go out of round.

Additionally, roundness is something that should be addressed at low tension long before final tension is being approached. It’s easier to fix at low tension than at high tension.

Dan Burkhart 

Of course. I always address radial true early in the process at low to moderate tension.Icould have gone on to explain that while the rim responds more to non drive side adjustment for lateral true it is the reverse for radial, but I was just responding to a particular comment.

cyccommute 

rm-rf was confused about radial true. rm-rf seems to think that during radial true, the tension of the driveside vs nondrive side spokes should be different. No one I’ve ever read says to treat the spokes differently during radial truing nor have I ever done so myself. The problem isn’t related to the differential tension as it is in lateral trueness.

FBinNY 

The problem with many posts on this thread is the focus on tension. This is a misdirection and source of unnecessary confusion.

What's important in wheel truing is spoke length and geometry. When you turn nipples you're either lengthening or shortening spokes, and changing the triangle formed by pairs of spokes and the hub flanges.

By way of analogy, imagine 2 people winching a piano up to the 3rd floor.

One weighs double the other, but regardless of the difference both have to haul the same length of rope. More precisely, there's a tiny difference because the heavier piano's rope will stretch more.

Likewise with truing, despite the tension difference both sides pull just about equal distance radially.

The story is different laterally, not because of tension, but because of the difference in bracing angle and the significant difference in the lateral vector.

So, put tension out of your mind and think about triangles and vectors and you can move the rim wherever you want.

Dan Burkhart 

The fact remains that adjusting for radial true on a dished wheel by turning the nipples on both sides equally will introduce a lateral out of true to the non drive side which then must be dealt with by truing to the drive side. I try to deal with it in a way that if anything will bias the area to the drive side and then correct to the non drive.

cyccommute 

You can’t put tension out of mind. If you are going to talk about vectors, you have to talk about tension. A vector is a defined as a quantity will magnitude and direction. “Tension” is a force and it has direction from the hub to the rim. It’s just an easier way of saying what you have said above. It’s also easier to say “adjust the tension on the spoke” than go into a long dissertation involving force, sines and cosines, angles, and a bunch of trigonometry. Tightening the spokes around a hump or loosening the spokes around a dip are adjusting the tension but it’s just easier to say tighten or loosen than go all mathematical on the issue.

zandoval 

That's my trick per say. I don't build wheels and have special tools, but I have resurrected more then a few old wheel sets and some new machine built wheel sets doing this method.

Some times I have been way off radially and other times its just because I know they are off that I start over. What I am trying to say is that when things start getting a little discombobulated on a wheel I am trueing, radially or not, I just loosen it all up and start over.

I am just glad I don't have to do it for a living cause I would surly starve...