Custom frame, is *close* close-enough?

I recently acquired a custom Ti Frame by a builder in the western US. Based on one of their stock design road bikes, with a bunch of changes to geometry and added tire clearance. Paragon z-couplers for travel purposes. Stock model has clearance for 700c x 30mm tires; I requested clearance to run 38mm tires if needed although had not planned to do so often. I had anticipated to usually run 28-32mm. Recently did some traveling with the bike, for most of the trip I rode 30mm tires. I brought some cross tires and mounted them on the rims I had with me; when inflated these measured out to 37-38mm width. The sidewall lightly rubbed on the inside of the drive-side chain stay. Cleared the seat stays and seat tube. This bike is equipped with the Syntace eccentric thru-axle dropout system. My understanding is the builder aims to get the rear triangle as perfect as possible; however this is not really practical due to the heating during brazing/welding, etc… So they get it as close as they can - within a couple mm I presume - and then the eccentric thru-axle system is used to get the rear wheel centered perfectly. On my particular frame, I cannot get the rear wheel centered, even with adjusting the eccentric thru-axle dropout. The rear wheel is biased too far to the drive side. If I could center the wheel the 38mm tire would have fit. Now… I did flip the wheel to confirm the dish is correct as well as trying an entirely different wheel. Same result. These wheels are also running true. I then placed the same wheel in a different frame which also has the Syntace setup, and the rear triangle on that frame can be centered perfectly. The 38mm does not exactly have a ton of clearance (if it could be centered)…would be about 2mm on each side at the chain stays. As it is there is 4-5mm (ish) on the non-drive side and 0mm on the drive-side chain stay - at that is the best adjustment possible with the adjustable dropout.

So… The frame otherwise rides great, and is beautiful with nice, tidy welds. Should I have them cold-set the frame to enable me to center the rear wheel?? a 35mm wide tire would roll, but would still be closer indeed to the drive side seat stay, such that it could potentially rub when under heavy stress.

S

hello Scott, have you spoken to the frame builder to air your concerns about the frames alignment? as it’s custom, i’d expect it to be perfect or if it’s not, i’d expect the builder to work with you to get it as perfect as possible and to get you happy with it

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Oh yes, the frame builder is great. They are happy to get it back to cold set it a little to get it better centered, no problem.

I wanted to get a feel from others in the community on what their experience has been re: frame alignment. For example Is the expectation that frames be 100% perfectly centered? Off by 1-2mm is OK, but 3 or more is not?? I mean these are metal objects made by hand, subjected to heating, cooling, bending, milling, etc…. I think it is hard to make them absolutely perfect.

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Yeah I would have them fix the issue. If this bike had carbon drop outs it would be a far bigger issue but if you’re paying the kind of money it costs to get a custom USA frameset then the wheels better be in straight. Any frame I buy regardless of price I put in a known good wheel right away and if it’s not square in the middle I send it back. A 10 grand C-Dale pile of garbage with an obviously bad rear end alignment they refused to warranty taught me that lesson.

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I agree with what others are saying. You seem very similar to me - you don’t want to be a jerk to the builder, but at the same time you’re always going to have trouble looking at the bike without thinking about the alignment issue. You’ve tried 2 different wheels and have the same problem, and that problem doesn’t exist when the wheel is in other frames, so you’ve proven that the issue is with the frame. It would be good for the builder to know this, as he may need to improve the process currently being used to build the frame. You’re not being a jerk here - getting a properly-aligned frame is one of the main reasons to go custom.

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Yeah, 1mm would be OK, 2mm borderline, but 3mm is not okay in any way.

Since this is made to be an all-road type frame with 38mm clearance you’d be looking at bare minumum 4mm all direction clearance out back. Also the fact that it looks to you like it’s only 2mm clearance if it was centered is also a problem.

At bare minumum some sort of cold-setting to improve tolerances and clearances is warranted.

I think what you asked and are asking for is quite reasonable. I’m currently engaged in a back and forth about a very tight seat tube on a custom frame, and my view is the same: expecting accurate tolerances is not an excessive or fussy request. I’d be polite but firm: it should be fixed.

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Regardless of whether it is centered or not, a 2mm clearance on a tire that big will hit the frame when it is loaded laterally. I would not run those clearances even when centered. I agree with the centering idea though

This is really interesting. I bought a custom steel randonneur (only geo was custom, design was standard) 10 years ago and the shop told me it was normal for custom steel frames that it was a bit uneven. They came with some plastic plugs in the dropouts to balance out the unevenness. I threw them away for some reason. Does somebody know how they’re called? Now adjusting the v-brakes is always a lucky game.

out of curiosity, was that C-Dale a carbon frame with a rear triangle bonded to the front triangle? how was the tracking when riding it?

No Clue, 2015 Super Six Evo Hi Mod. I will try to find pics of the alignment. I banished it to a dumpster after Cannondale refused to warranty it. Bike didn’t have a huge riding issue it would go on a straight line. It would rub a 23mm and the shifting became god awful.

No idea who built the frame, but in their defense, a road bike with 38mm knobby clearance is very difficult to achieve on a “road” bike. Also, just my opinion, 38mm knobbies push past the scope of a road bike to the point where you start compromising its design.

It is possible that the frame is out of alignment. But I think it’s more likely the difference in clearance is the asymmetry of the DS and NDS chainstay. It’s really hard to clear a 38mm tire and road bike chainline (compact gearing) with a titanium chainstay. You would likely need a 3D printed yoke or some other trickery:

If I were you, I would just eyeball the tire alignment relative to the seat tube. If it’s really 3mm off, you should be able to see that by eye.

Also, I would throw some 35mm knobbies like the Conti terra speeds and call it a day. Even if you could fit 38mm the bike would probably not ride as well, unless it was specifically designed for it.

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It is a road bike frame, with a little extra clearance. I did ask for 38mm clearance but I don’t think this was factored into the design very well. It was designed to be optimal on a 32mm tire. But the exact clearance is not a huge issue; I’m fine with whatever clearance the frame provides at this point. A 35 would clear the stays better and be rideable as-is. But I still expect the rear wheel to be centered better. And keep in mind this bike uses the Syntace eccentric dropout system. With that system the rear wheel should be able to achieve exact center. The fact that I can’t get in centered even with adjusting the eccentric thru-axle dropout indicates to me the frame needs adjusting.

The stays are perfectly symmetrical, and straight. Not pinched. If i send the frame back for cold setting I could ask them to pinch the chainstays….but I don’t want to ruin those perfect stays.

There are two degrees of freedom that the rear axle can be misaligned:

  • Left and right centering - the axle needs to be in the centerline of the front triangle
  • Angular alignment - the plane of the wheel and plane of the front triangle should be parallel

Syntace dropouts only correct angular alignment. the 1mm eccentric insert angles the wheel roughly .4deg, and results in ~2.5mm of lateral movement at the tire. The eccentric dropout is not intended to be used to “fix tire clearances” (which it often is used for).

The way you are checking alignment (clearance between the chainstays) is not a good indicator of alignment. Your chainstays are likely asymmetric by design, so it is a bad reference.

Builders often align the BB and ST first, then ensure the dropouts are properly spaced and bisect the centerline of the frame. If your wheel looks aligned with the seat tube, it is probably both centered and parallel. If not, the builder would need to determine if it is a centering issue (which is easy to cold set), or an angular alignment issue (which is solved with the syntace dropout).

Regarding dimpling your stays more, I personally would avoid this. Titanium does not like to be cold-formed, it decreases its fatigue life.

Again, I have no idea who your builder is, but I would give them the benefit of the doubt. Thru axles, flat mount dropouts, and shifting drivetrain standards make gravel bike framebuilding very challenging. 700x38 and road chainline and chainstay lengths are really challenging combos to achieve in titanium without the use of 3D CAD. And even then, I would argue that road gearing with 38mm knobbies does not make sense.

I’m sure they tried their best with the time that they had, the knowledge that they possessed, and the tools and workflow they had available to them. That’s part of the fun of having an individual build your frame, rather than a corporation.

Great info - thanks!

I agree the syntace dropouts are a “fine adjustment” tool only and cannot account for a wheel & RT that are out of center or out of camber (the angular alignment). The RT should be built near perfect as possible and the eccentric dropout used to make a tiny tweak if needed. Although there are really three degrees of freedom here…. One is that the wheel is centered. Two is angular alignment front to back. Three is angular alignment top to bottom. The syntace dropout can compensate (to an extent) for both front-back and top-bottom angular alignment, but not centering (for that you’d have to move the wheel sideways in the right-left direction relative to say the seat tube (or plane of the RT).

The builder is DEAN in Colorado, who are great and I love the bike overall. It is an El Diente with paragon’s z-couplers for travel. Size is custom but based on the El Diente geo. This is a road bike, not gravel. It’s true I did ask for 38mm clearances but the El Diente normally doesn’t have that much clearance, so they did not actually build it with that much clearance. But they gave me as much as they could within the constraints of the design of that model. It’s intended for 28-32mm tires. 38’s really can’t be ridden - even if it were perfectly centered. 34 or 35 would be a stretch. The cross section of the chainstays is oval. No pinching/dimpling at all. Straight, no s-bend at all in any direction. They are not asymmetrical. Both chainstays exactly the same in all respects. Seatstays are smaller diameter, round cross section.

The only reason I haven’t sent it back yet is because I don’t want to part with it just yet - even for just a couple weeks.

You are also correct in that without proper measuring setup, I can’t tell if the wheel is in plane and not centered, or if it is truly out of angular alignment. They would need the frame to figure this out for certain. At that time I would ask them first what would be required to align it properly. If it would require anything that could potentially reduce the fatigue life of the frame I would not do it.

Lastly I agree that I do not want to dimple or pinch the stays. I don’t know if this would potentially damage the metal or not….but I just like the look of the perfectly straight symmetrical chainstays.

A great discussion!

SB

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I just asked because it would seem that metal frames would be harder to keep aligned all the way through the manufacturing process (and that probably holds true), but then I realized there’s also plenty of ways a molded carbon frame’s alignment can go to shit because one step in the process got blown.

Judging from what you’re describing here and having worked on a few Dean frames like yours in the past years I’d argue that the frame as it is can’t be better aligned. Or if they try they’ll not improve it and compromise its longevity.
If you’re happy with how the bike rides when you’ve got up to 32 mm wide tires installed I wouldn’t let them try to cold set it. They don’t have any magic capabilities to get this thing straight past welding. Especially not with those dropouts.
If you want it to be as ordered - compatible with 38 mm wide tires -, Dean has to remove the rear “triangle” and do a better job of making sure it’s well aligned on the second attempt.
As others have already stated sufficient clearance for 38 mm tires on a frame with just 420 mm chainstay length, a road dual chainring crankset with straight chainstays is next to impossible to reach though.

Bike rides great….and nothing is perfect. As I said I don’t want to part with it - even temporarily - at the moment. Still undecided on whether to send it back and let them fiddle with it. At work we have a saying…. “The enemy of good is better”.

The frame is 99% perfect now. Trying to get it to 100% may make some things worse. I would hope the manufacturer would not do anything that would harm the frame but sometimes they could make unintentional sacrifices in order to make the customer happy.

Thanks for all the great advice!

SB

Tire clearance aside, if the wheel wasn’t centered it’d drive me slightly mad.

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Yeah…. Rides great. Beautiful bike. Just drives me a little mad knowing it’s not as perfect as we think it ought to be! Hence all the discussion….

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