I bought a used wheelset for my road bike and they do not seem to be true. When I apply the break a little bit, I can see the rim is touching the break pad unevenly. I don't have a way to measure, but my guess is the rim is off at least as much as 2 mm.
Is it something I need to worry about? My average speed on flat road is 20 mph.

If indeed the rims of both the front and rear wheels are 2mm off, what might go wrong?
Would it damage the wheels further?
Would it be unsafe to ride in high speed (20+ mph)?
Would it go not as fast?
How true is true enough? 2mm off? 1mm off, or less than 1mm off?

How much would it cost to make them true from a local bike shop?

Many thanks.

Why is this such a challenge for so many people? They're brake pads.

Most wheel builders shoot for a fraction of a mm in both lateral and radial runout. If it's a mm or 2 you won't crash, but it will most likely get worse over time.

Speed shouldn't be a problem.

How much will it cost? Dunno, maybe you should ask your local bike shop instead of people here that have never been to that shop. When I true a wheel the labor charge starts at $20.00 and goes up depending on how long it takes.

 

@dinga

If indeed the rims of both the front and rear wheels are 2mm off, what might go wrong?

If your wheels are that much off, most probably you have drastically uneven spoke tensions. This will eventually lead to broken spokes.

Would it damage the wheels further?

Yes, see above

Would it be unsafe to ride in high speed (20+ mph)?

Could be. Specially if you have one of these low spoke wheels and one breaks off.

Would it go not as fast?

Obviously not.

How true is true enough? 2mm off? 1mm off, or less than 1mm off?

True enough is at 0.1mm with a true rim. Some rims are not as true as others so some wobbling may be inevitable.


As cx said the cost of truing depends on the shop. However, you do not want JUST truing. You need truing and stress relieving and equalizing tensions. At a wobbling of 2mm more than just truing is going on.

 

True enough is at 0.1mm with a true rim. Some rims are not as true as others so some wobbling may be inevitable.

If we're talking about total runout (farthest point to the left, all the way over to the farthest point to the right), and you're using a dial indicator to measure, then 0.1mm is a little crazy IMO. And with lots of rims (especially disc brake rims) it's not even achievable. And even if you think you have it that close, flip the wheel over and measure the other side of the rim. The rim width likely isn't within 0.1mm. Then there's the whole issue of the seam...

Plus, the wheel is going on a bicycle where the frame and fork are flexing, the tire casing is flexing, and you're riding on a road that's nowhere near 0.1mm from perfectly smooth. It doesn't need to be that true, and chasing that number isn't worth the time needed.

I build to 1/4mm for lateral runout. Sometimes it's less though, this DT Swiss TK540 rim (which is a beefy welded touring rim with a machined sidewall) came out at 0.11mm - https://www.instagram.com/p/BBKmb_cypuq/?taken-by=dgaddis12

 

I wouldn't ride wheels that were that untrue. Then again, I'd just true them up. If the are just out of tru but the spokes are not completely out of whack tension wise, this should be a 5-10 minute task per wheel. If you needed to loosen everything up and start over, it is more like 30 minutes to an hour depending on the person doing it. I would take about an hour, and that is because I'm slow. I can't imagine it taking anywhere near that long if someone who did this for a living was doing it.

When I'm done the imperfections around the weld on the rim is usually what touches the finger in the stand, so it is well within a half a mm laterally and radially. When I was learning I used a 0.003" shim to test myself. I think that was overkill.

 

When I'm done the imperfections around the weld on the rim is usually what touches the finger in the stand, so it is well within a half a mm laterally and radially.

Hmmm. If this is a guide to "true enough", does this indicate that I've been too fussy? Sometimes I'll hear that "dink, dink, dink" against the weld, but if I close the fingers just a tad more, I'll find another slight imperfection to adjust. The truing stand definitely amplifies imperfections and I can get quite obsessive.

 

@dgaddis

Lateral trueness target at 0.1mm is doable with the right rim and the right number of spokes and the right amount of time. My absolute max limit on lateral trueness is at 0.2mm. Either will be more evident to the builder than to the rider. I had some rims that could not be tamed while maintaining relatively equal spoke tensions; I dont use these makes any longer and I dont do 24 spokes or less.

 

When I build wheels for others (which is rare) I get them more true than when I build for myself because I know that there are other things more important than ultra-true - and that is, equal spoke tensions (or as equal as possible while providing acceptable trueness). That plus sufficient over all tension.

For most people, wheel wobble (or lack of) is their only way of qualifying a "good" wheelbuild and no matter how much you tell them that tension equality trumps trueness, they still have a skeptical eye. That's why I spend more time on them going back & forth between equal tension and true.

I don't measure runout on my own wheels anymore (I do have a dial indicator truing setup). Close is close enough.

 

Are you saying that one brake pad touches the rim before the other? If so, then your calipers most likely need to be rotated so that they are centered around the wheel. If the wheel looks like it is closer to one side of the frame or fork then the dish of the wheel is off - meaning the rim is not centered with respect to the hub.

 

Is it just the top edge of the brake track, or the outer edge of the rim itself?

Is the tire bed reasonably round?

Without seeing it it's hard to say what to do. When in doubt, cut the spokes and lace up a new rim.

 

Hmmm. Sounds like the rim may be toast. Hubs are good Tiagras. No wonder the bike was so cheap. That may be a good project for next fall/winter.

Or I could just true the wheel, uneven tensions and all and ride them into the ground i.e. until a NDS spoke breaks for lack of tension. These are 36 holers, so if I break one, 35 will certainly get me home.

 

we've derailed this long enough. Check your PM.