It doesn't matter.

Laser level. I have one that I use for knee tracking.

They are cheap ($10-$15 at Target or Home Depot).


The perfectly straight line they create should go down both the center of the tire/wheel, and the center of the back of the seat tube/seat post. Even a small misalignment angle will be plainly visible. It will also show you is the wheel is crooked in the frame, or just off center/dished.

---

ECMGN Therapy Silicon Valley:
Depression, Neurocognitive problems, Dementias (Testing and Evaluation), Trauma and PTSD, Traumatic Brain Injury (TBI)

---

Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

Sounds neat - but I'm trying to figure out how you get the laser to show the center of the tire/wheel and the back of the seat-tube without the wheel itself blocking the laser beam. If you could clarify, I'll try this myself!

Quick pic using the laser:

---

ECMGN Therapy Silicon Valley:
Depression, Neurocognitive problems, Dementias (Testing and Evaluation), Trauma and PTSD, Traumatic Brain Injury (TBI)

"I also dabble in precision, and if you think you can even approach it with your sad, naked, caveman eyeball and a bubble of @?!!# air, you’re the reason this species is a failure, and it makes me angry!"


True Level

---

"I'm thinking of a number between 1 and 10, and I don't know why!"

Ahh right. One of my laser levels had a prism attachment that would form the beam line... it broke years ago, but I like this idea. Thanks!

Just what I was asking for, thanks - I'm gonna try that!

Hey fredly,
Thanks for responding. Sorry, I don't recognize this tool. Where can I read more about it?

https://www.parktool.com/...lp/dropout-alignment

Looks like a good tool to use to indicate a problem! Appreciate the link to read-up on it.

Thanks!

“Typically, misaligned dropouts will not effect how a wheel centers in a frame, “

Fair enough. Also true.
Short of putting your frame on an alignment table, there isn't any easy way of telling if your rear wheel is aligned with the centerline of the frame. Aligning the wheel with the seat tube *definitely* doesn't do this either; how do you know that the seat tube is aligned with the head tube? How do you know that the fork is aligned correctly?

IME, most frames are at least slightly out of alignment, and there really isn't anything you can do to fix this with a carbon frame. It's essentially impossible to notice this when riding (unless it's really bad) and functionally it doesn't matter, unlike dropout alignment which absolutely *does* matter. Again, *functionally* we have to assume that a correct dropout alignment will result in a wheel that is also in alignment with the frame, because you can't fix it if it isn't.

FWIW, this *is* worth checking with a brand new frame, because the only way to solve the problem with a carbon frame is a new frame. Unless it's paint buildup or flash on the dropout surfaces causing an alignment issue, but I'm assuming anyone that has gone this far down the rabbit hole has already checked for that.

If your dropouts aren't in alignment with the rest of the frame, and you happen to have horizontal adjustable dropouts, you don't want to attempt to "fix" alignment issues by canting your wheel in the dropouts. Doing this will A: put your cassette out of alignment with your derailleur B: misalign the dropout faces with the end caps of the hub and C: impart a bending moment on the rear hub axle.
"C" is something that used to be a big problem when horizontal drops were more common and freewheels rather than freehubs meant a long unsupported span of axle on the drive side of rear hubs; bent hub axles were pretty much ubiquitous back in the day. It's really hard to do this with modern equipment, but if you're going to do it, well... this is how you would go about it.

---

Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

Thanks fredly,
I found your response very objective and well-scoped. For context, the DA1 frame was a NOS purchase last October and the build was completed early January. The 85 mm rear wheel purchase (prior-owned) integration soon followed. After the maintenance on the cassette I mentioned above, I noted the observation which prompted this post.

What I plan to do:

• Unpack my wheel-building stuff and do a dish, spoke tension and run-out measure (we recently moved and I haven't done this yet.) I already know that there's about a 2mm out-of-true spot on the rim just by spinning the wheel.
• Once the wheel is correct, re-install it, measure the brake surface - chainstay gaps, and then try to minimize any apparent "yaw" discrepancy by using the dropout adjustment setscrews.
• If I can find a replacement prism for my laser level, I'll clamp it in my camera tripod as an indicator/comparator to the rest of the frame as mentioned above.

I think this approach would be what I can realistically do to mitigate any off-set wheel tracking.


Everyone: thanks for your response. I appreciate your thoughts.

Regards,
Eric

Don't assume chainstay gaps will or should be equal on both sides of the wheel. This sometimes isn't the case, and by design.
If you're going to center the wheel to any specific point, on a caliper brake bike you should probably use the mounting point for the brake.

---

Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

Hiya fredly,
Lol... trying not to assume anything, but your point is well-taken! The DA1 has two mounted posts for the brake arms behind the BB. That may serve as a "known" starting point :-)
Cheers,
Eric

Place bike on ground upside down. Place a ruler in the dropouts. Mark the center point. Mark center point of brake mounts, and center point of headtube. Shoot a laser line across all three points, see if they line up.

---

Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

Use a long straightedge. Have it contact front and rear wheels/tires each in two places all simultaneously. Easiest way I know. If there is misalignment you lose watts. This way disregards frame center but gives actual wheel alignment which is critical.

Kinda?
Unless you take the tires off, it's giving you tire alignment. I know the tires on the bike I'm riding right now aren't in alignment (I've checked).

So, take the tires off. Then yes, you're getting wheel alignment.

My wheels aren't perfectly dished anymore, so... well, that's out too.

I suppose I could go and dish the darn things, but then I will need to make sure that the dropouts are correctly faced and that the fork is true. Which, if it's a carbon fork, it probably isn't. Corollary to this, my guess is that these days if a person actually wanted to go down this rabbit hole, in order to get the two wheels to run in perfect alignment (with a stock carbon fork) you'd more or less have to intentionally run the rear wheel out of alignment with the frame. Which is what the OP was asking how to check.

It's a giant rabbit hole.

---

Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

Thanks Matty. I appreciate it!

Folks will want to be mindful of the pretty serious limitations of a technique like that when working on modern frame designs. There's an awful lot of asymmetry baked into some of them, especially in dropout construction, but sometimes it goes way farther than that...

---

Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

ermergerd haha. Thanks for that.