Handmade frame: asymmetry normal?
I have a steel handmade frame, and I noticed the chainstays are slightly asymmetrical.
The right chainstay is something like a couple of millimetres closer to the centre of the hub than the left.
As a consequence, I redished the rear wheel to the frame (i.e. not to the hub) to improve clearance, and I don't think it'd be an issue.
But is this kind of asymmetry a normal thing in handmade frames? I ask since I read some people asked the builder to change their frame for something similar. To me a couple of millimiters seem reasonable in a handmade build.
All depends on the control the builder has with their hands. Many would probably say it is normal. Obviously a couple of mm's won't make a difference but actual interference of parts is exceeding the tolerance level of what would be considered standard.
I've read some opinions on the web, and it seems there is no definitive answer to what an acceptable frame alignement is.
In this post it is said:
most industry tolerances for frames is 5mm
Frankly I doubt that typical industry tolerance is 5 mm--they seem too much!
A good frame should be aligned with less than 1mm
of deviation from center (again, taking the measurement from the inside of the dropouts, which determines where the wheel actually lines up w/ the frame).
Nevertherless, another opinion is that:
A more involved answer is the following:
Customs frames are typically held to much higher tolerances
than factory stuff, it's one of the things that set them apart.
So I'm a bit confused. The only issue I had was little tyre clearance to the right chainstay, but after a custom dish of the wheel (as I described in my original post) I solved it. I can't notice any tendency of the bike to pull in one direction, so I'd assume the wheels are parallel, even though they don't lay exactly on the same plane (they are 1-2 mm from each other).
None of the frame alignment "standards" people quoted is really correct, because there are two standards. Any good framebuilder will have two alignment tolerances, one for how far off of the centerline line a part of the frame can be (but parallel to the centerline), and one for how twised it can be relative to the centerline. The twist is the tigher tolerance
. The important thing is that when you look behind the frame - are the wheels parallel (and perpendicular to the seat mast / BB) or do they make an "X"? The frame can be out of alignment quite a bit but as long as everything is parallel to the centerline it will handle fine. When the front and rear wheels make and "X", then you start have problems. The issue with the string method is that it measures down the center of the "X", which can read perfect but your wheels may possibly point in completely different directions. The true test is, take your hands off the bars - does the bike pull in one direction? Now turn hard left and right, does is want to dive into the turn going one way, but fights you going the other way? Then you have an alignment issue that can only be corrected by measuring and setting on a precision table. If it handles fine, then forget about it and don't mess with your wheel dish either.
Since I don't have any noticeable issue I'm not particularly concerned now. Mine is just curiosity to better understand this point.
I saw an aluminum frame the other day made by a major manufacturer that had at least 10mm misalignment between the dropouts on a through axle bike. It was one of 3 with the same issue. Manufacturer's response was to cold-set. Nobody builds a dropout alignment tool for through axle yet, do they?
I wouldn't take a wheel out of dish if it wasn't actually in danger of hitting. I don't know what to say about your frame, hard to tell without seeing it. The spacing of tubes on the BB is where I would expect to see some -- mostly harmless -- discrepancy on a handbuilt frame.
Symmetry isn't "alignment"
Remember, for your frame/fork to ride straight, you only need a few things: BB, hub axles, and saddle all in the same plane. This is "alignment" and as long as the bike goes straight when you want it to, and doesn't act weird when turning in one direction but not the other, it is as good as you need it to be. Every builder has their own standard here but the bottom line is that it takes a LOT of misalignment (I know because I built one by accident with at least 2 degrees of HT twist thanks to not tightening my HT cones and it *almost* rode straight) to cause a problem.
You'll see a lot of pictures online of people messing with super-finely calibrated dial indicators and plates ground to .0001" flatness and such, but if you're referencing from the (faced) BB shell the best you can really do is about +/- 2mm anyway (unless you're facing the shell with some sort of amazingly perfect tool that doesn't exist). So it's not worth getting too hung up on in general.
Now, symmetry. You also want various parts to not interfere (ie, chainring hitting chainstay, tire hitting seat tube, etc) and that's a separate concern. Many, many bikes are not built in perfect symmetry deliberately (ie FS bikes which use a dropped driveside chainstay to clear a front derailleur) and there are also lots where there is some accidental asymmetry (a chainstay is joined 1mm outboard on one side compared to the other, or the bends in the seatstays aren't perfectly even, etc). There are also often non-symetrical frame parts (disc mounts, derailleur hangers/mounts, etc) and brazeons. I often use different wall thicknesses of seatstay on the brake and non-brake side of a frame. So having a bike be symmetrical is not very important in most cases, and in fact there are sometimes advantages to a deliberate lack of symmetry.
As an aside, I like to build 5mm offset rear triangles on some 1x drivetrain bikes because you end up with lots of room for a tire, a great chainline, and a dishless rear wheel. Sick!
If your bike rides the way you want it to, then you are good to go. That said, it's a custom bike and if you're not happy, have your builder make some fixes. They should be happy to oblige.
Specialized made the Demo, SX Trail and BigHit with 6mm offset for some time. The dishless rear wheel and 2.5 tire on a 10x135 frame was pretty sweet.
Originally Posted by Walt
Why not? The bike does go straight even though the wheel now is slightly out of dish (1-2 mm max).
Originally Posted by unterhausen
Previously the tyre was so close to the right chainstay that with some mud or when the wheel flexed it interfered with the right chainstay.
Probably the wheel was also out of dish previously (just 1 mm or so to the right). The right chainstay is closer to the centreline of another mm. We therefore adjusted the dish and moved the wheel a couple of mm to the left.
No noticible drawback, but better tyre clearance.
Thanks Walt for clearing this up.
My builder in fact told me the right chainstay is closer to centreline so that it doesn't interfere with chainring.
Personally I didn't notice anything weird either before or now--after slightly changing the dish. Personally I feel such change on the wheel was so small that in practice it doesn't affect riding.
The only thing previously was tyre clearance, but now it's solved.
Wait, so you shift the whole rear end by 5mm to the drive side and then dish the wheel 5mm toward NDS? How does that increase tire clearance? Wouldn't it also need to be S bends CSs to keep heel clearance in check?
Originally Posted by Walt
FWIW, I love the idea of this! Talk about "custom", that's just a really great idea.
I would imagine that you'd also have some funny looking tire spacing on the SSs too huh?
A better explanation
Ok, sorry for the hijack:
-This only works for 1x setups where you do NOT want to run a bashguard integrated to the crank (you can go the ISCG mounted route if you want, though). There an exception if you are ok with a non-73mm shell, I'll get to that in a second.
-Move the rear wheel wheel 5mm to the DS.
-Dish the wheel back 5mm to the NDS, resulting in a (basically) zero dish wheel. Note that if you're using a SS hub this is dumb because you'll have to take it from zero dish to a bunch of NDS dish - so this is something you do with a *geared* hub. If you want to run SS you can but a geared hub and a few more cassette spacers is the way to go.
-Move your chainring from the middle to the outer position on the crank.
-Now you've got a dishless wheel, a decent chainline, and a chainring that has moved ~6mm away from the chainstay on the driveside. This means you can move the chainstay outboard too (yes, s-bends are a good idea if you are worried about heel strikes) and get a bunch of extra tire clearance.
-I like to use tab-type dropouts and you can just make the slots asymmetrical (ie slot outboard on the DS, inboard on the NDS) to keep the stays relatively symmetrical if you want even crankarm/heel clearance.
-You can also do an 83mm shell if you want to run a crank bashguard (the middle ring will line up perfectly in normal middle position) though the selection of cranks is not the best.
I have a hard time talking customers into this because they sort of inherently think it is weird, and you have to have a custom dished wheel (ie, you can't just grab any old wheel and shove it in the frame). But it's a great way to go in some cases.
Hopefully that makes sense. If not let me know.
Don will make you an offset dummy axle if you ask nicely, btw.
Originally Posted by jay_ntwr
Walt, thanks! This is really validating to me. I built a frame with a 5mm offset and an 83mm bottom bracket shell. It ran a Hammerschmidt and fat tires, just barely.
I parted it out, a stupid decision. I miss that bike.
Again, I like the idea and immediately thought it would be great on a DH 29er and that's probably where I'd use it if I were to do it. Thanks for the clarification on what you do as well.
Originally Posted by Walt
For OP, how did you measure this offset rear axle spacing? I know I can get it close to nuts-on with a surface plate and height gauge but not sure how many people that don't have those tools have that option.
There is a Surly frame (Crosscheck i think?) that comes with 132.5 rear axle spacing, so you are free to use a 130 or 135 axle...Obviously not a small custom builder but the point is that people pull and push on chainstays of steel frames all the time not thinking about the alignment consequences and definitely don't go to the trouble of re-dishing a wheel (unless it's for Walt's new offset 1x frame -sweet idea for a short stay 29er!). But hey, you did it and it works so more power to ya!
I heard a story of an old Ibis Hackaluggi (sp?) that was 135 and the recommended fix for the racer to use his old 130 cross wheels was to lay the frame on its side and stand on the rear triangle till it fit the 130 hub...! They didn't even consider the centerline and it rode and raced fine.
But if I were in your place, I would have just cautiously yanked on the DS stay to pull it out 2mm, then pulled on the NDS chainstay 2mm and called it good - assuming you have the right tools to keep the centerline constant and not pull the dropouts out of parallel...
I've had my few frames come out aligned ok...ish. But holy hell is it tough to keep everything perfectly symmetrical, especially when hand cutting tubes. I don't consider myself a framebuilder by a long shot, but I've picked up an appreciation for things that a few years ago would have gone totally unnoticed.
And to jump on the threadjack about offset rear ends: I've got thousands of Pugsley miles under my ass, so an offset isn't an oddity to me anymore. It's kind of far down the build list but I have a Trials-ish Play bike in mind with a little offset built into a short 26"wheel in rear end. On a 26" with short stays and no FD, a chain guide is needed to keep things in check due to the angle created by the short distance from BB to Axle. So with a bit of offset to keep the chain line reasonable and minimizes the dish required....and a SS cassette hub with 6ish cogs on it would build a bomber rear wheel. I need to do more thinkin' to see what offset would be needed to be evenly dished with a SS cassette hub.
Slowly slipping to retrogrouchyness
This is a slight thread drift but it seems like this thread has drifted anyway, so... If the frame is built close to symmetrically and the rear spacing is off, then pulling or pushing the dropouts using the other dropout as your counter force (as opposed, say,to the bottom bracket post of an alignment table) will keep thinks more/less on center. Newton's third law of motion (every action has an equal and opposite reaction) says so. This, of course, doesn't help the OP.
Originally Posted by Meriwether
BTW, you didn't spell Hakkaluggi correctly (and neither did I, I think). It has (or at least should have) an umlaut or three in it.
Unless you discussed and specifically asked for an asym rear triangle, your frame should not have one.
I build a fair mount of 6.5mm-offset rear triangles, but only when asked to do so.
My frame builder told me it's hard to bend tubes equal, thereby stays may well have some slight difference.
Originally Posted by G-reg
Originally Posted by solitone
Well, it's really not, with decent equipment. The hard part is in the fitting/welding phase in my opinion. Stuff really likes to wander if you don't pay attention.
Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
- John Hajny, a.k.a. TrailMaker