How much “wheel hop” do you consider acceptable when truing a wheel?
 

Of course 0mm is ideal.

But if you end up with 1mm, do you call it good? 2mm? 5mm?

I mean, once tension is even and of proper amount and side to side is true, but you have “x” amount of wheel hop.

How much would you have to see to make you start over…?

"Wheel hop" = radial deviation.
"side-to-side" = lateral (or axial) deviation.
I don't build a lot of wheels, just for my personal use. I'd consider 1mm of radial deviation OK. Maybe 2mm tops. Depending on the tire size and inflation pressure*, these would probably be undetectable when riding.

EDIT: *... and speed. :innocent:

According to the Hand Built Wheel Inspection sheets that came with my new Roval Terra CL wheelset, the Radial Trueness is 0.17 front and 0.3 back. No units stated; hopefully mm?

It depends on whether the variation is due to how accurately it is trued or if it is due to a specific problem area - like around the seam.

I hope for better than 1 mm, if I'm building from new parts. The rim has to start out round. I've never been successful trying to straighten a bent rim on the truing stand. Maybe a more experienced builder could have a better chance, but I don't think I've built even a dozen wheels in my lifetime. I only build wheels because I'm interested in oddities such as IGH's.

For me, a "moment of truth" on the stand is not really my goal. I'm trying to build a wheel that will stay true in actual use. For this reason, I'm aiming for fairly high and consistent tension.

I'm sure mine are less than 4/1000", but the joint is never perfect. Tires are off 1 mm a lot of the time.
How I do this is put a piece of elec tape across the fork touching the rim and whittle the hump down.
The closer it gets the less the tape deflects when moving the rim back and forth.

I've never measured it but you can easily see 1 mm and I would consider that to be excessive. Before I could quote a number I would have to take actual measurements and that isn't on the cards. Grab a$$ number would be 0.3 mm.

None, in all seriousness, while I've never actually measured it, but I expect that no more than a quarter turn of the adjusting knob is all that is needed to go from the rim touching for the whole circumference to not touching anywhere. When spun in the hand there should be no visible movement indicating any type of hop at all. I also don't think this is nit picky, at high speeds I don't want anything that can even remotely throw off the way the bike feels.

Depends on the rim. I used to get what looked like 2mm at some seams and no amount of spoke tension variance would change that, but it seems that they do a better job making rims nowadays. I like it when I can only hear it and not see it on the truing stand. That being said, even spoke tension is more important than a fraction of a mm.

I go for roundness and uniform tension first; just getting side-to-side good enough that the tensions are meaningful. Roundness and tension at the same time so I learn early on just how round the rim is, especially at the seam. If the seam isn't perfect, I shoot for the best compromise. I don't like messing with hop once the spokes are becoming tight. With rear wheels that usually means tightening the already very tight drive-side spokes. Building wheels the hard way. I shoot for best compromise on hop by mid-tension on the spokes.Tighten the drive side to close to final and do the rest (now just side-to-side) with the non-drive spokes.

Round wins friends and influence. Even tensioned wheels go further with less attention.

+1 Yes, the new rims are better. And fractions of mms? I went down Smuggler's Notch in a race in 1977 on a Fiamme rim and a Super Champion. I built both wheels. I doubt either was much under a mm. (Those seams.) Bike, wheels, the whole package was simply perfect. Our speeds were not recorded but the pace car, a police car driven by a local cop who knew the road, had to hit 65 on the straights to stay ahead of us. (We weren't braking for corners.)

I don't build many wheels, no dial indicators on my stand, but If I can get within a credit card's thickness (.75mm) I call it good.
Rim joints can be troublesome, sometimes they appear worse than they are because it's the only deviation.
There is a recent park tools YouTube about not interlacing crossed spokes, I think my future wheels will be built without interlacing, I find its easier to get a consistent note when you pluck a spoke.

I build wheels to .5mm radial variance. My friend Al, who is a perfectionist, dials them in to within .1mm. His wheels are truly exceptional, and the sick thing is that he can get that level of roundness in the same amount of time it takes me to get my .5mm. The guy is amazing.

2mm out of round is unacceptable, especially with rim brakes.

I want my wheels true enough that I don't feel any irregularities, which depends a lot on the tire size. I could probably tolerate 3-4 mm on a fatbike, but I'd want less than 1 mm on 20mm wide tires.

+1 this. With new rims, my experience is that more expensive rims will be closer to round than cheap rims. Deviation from round at the weld seam/joint won't go away, no matter what you try. With used rims, do your best but don't expect perfection no matter what the original quality of the rim.

When building, I try to get the radial runout as close as possible. Is that 0.1mm? .004"? I don't know. Except for around the seam, the radial 'hop' is typically not visible. My theory is that radial runout is more closely tied to overall spoke tension in differnet regions of the wheel, so when building and everything is as close to ideal as possible, it makes sense to put in some extra effort to get this as good as possible.

For lateral 'side to side' runout, maybe I shoot for about the same, but since I stopped working in shops and only build my own wheels, 'not hitting the brake pads' is the standard I go for.

On good rims, the seam is usually pretty good. I true to tension mostly. Rim brake wheels I pull true even if it causes a small variation in tension. Cheap wheels are different. Fortunately most cheap bikes nowadays come with disc brakes so it's not super important to get a wheel exactly true or round.

Nothing related to roundness nor true would make me “start over”. I would work to reduce them and try to do that kind of work when the spokes are at low tension but I wouldn’t “start over”. 1mm is probably the most “hop” I would accept but much less than that is part of that “perfect being the enemy of the good”. Let’s remember that 1mm is equal to about 1/32” which really not that much and won’t make that much of a difference.

The seam is always a problem. The pins used to hold the rim together…even welded rims have pins…resist the curvature of the rest of the rim and leave a slight flat spot.

I don't feel that any hop is acceptable. Honestly, it's not hard to tighten the spokes a half-turn at a time where ever the rim touches the top of the arms of the trueing stand until the not-yet-wheel is round & a moderate tension has been reached. Then side-to-side axial true, then dishing. It's at this point the wheel is about 75% built & I go back to focussing on radial deviation.

Then axial working on sets of spokes & so it goes back & forth until perfection at the target tension.

Radial is probably the easiest red flag for uneven spoke tension. The spoke under the higher load is going to unfairly pull the rim towards the hub. When all your tensions are even this is pretty obvious. A tension meter can help but I find it is more of a quality control & validation tool to a properly built, round wheel.

I prefer to have my wheels be a cross section of a sphere & not that of a cone. Focusing only on tension or axial deviation will not yield a round wheel. Round is where there will be the least stress & greatest load share in service.

Got visited by an old buddy from SanAnto. We were hanging out in the driveway getting a couple of bikes ready for a ride and he spotted an old aluminum rim I had given up on. It was out of round and twisted laterally. He grabbed a hammer out of my tool box and within minuets had it all straightened out by just twisting and banging on it on my picnic bench. I was so impressed. It looked perfect. Of course 40 years banging dents out of cars in his body shop probably had allot to do with it.

As to the OP: A hop is not acceptable. But as things get more and more expensive there are things we have to put up with until we can afford a fix, repair, or replacement. So when is a hop unacceptable? When you can feel it during your ride bad things are around the corner...

In manufacturing, everything has some variance from 'perfect'. In super-precision devices this might be in the 1/10s of 1/1000", but there is still variation. On a bicycle wheel, I bet most would be unable to feel a difference of 1mm, radially or laterally. The variance allowed before you can feel it likely varies with tire width and pressure - an 18mm tire at 140psi might make a wheel hop noticeable that wouldn't be noticeable with a 35mm tire at 60psi. Lateral movement is generally less noticable than radial - I have ridden many kms with a broken spoke and 5 or 6mm of lateral runout and not noticed until I realized the brake was rubbing and I looked at the wheel passing through the brakes. A major 'dent' or other flaw causing radial runout is easier to feel.

A wheel with too much of a radial runout will feel bumpy when ridden. True until you cant feel the hump.

the park tool wheelbuilding site list 1mm for radial and .5 mm for lateral (10 sheets of paper and 5 sheets of paper respectively)

https://www.parktool.com/en-us/blog/...and-rim-truing

My standards can be flexible. The 1980s Weinmann rim on the back of my fixed-gear has never in its life been as perfectly round as we expect from good rims today, so I only touch it up if it gets more than a couple millimeters out. Fortunately, that's rare.

Come to think of it, my goal is always to get the wheel as round and true as the rim started out. (Checking it against a pane of glass first isn't a bad idea.) I often have to compromise a little at the rim joint, but with experience, you can find that point of diminishing returns a lot sooner.

I'm with Al, unless its an old wheel that's been through a lot of abuse.