Who to trust for frame alignment?

[stephenmarklay]

I noticed my rear wheel on my CSI is closer to the left stay than the right stay. I want to get the rear triangle looked at.

Is this something a bike shop can do or do I need to seek out someone else like a builder?

[Joxster]

Is the dish on the wheel correct?

A basic way to check is to tie a bit of string on the lefthand drop out and run it upto the head tube and back to the righthand dropout, pull tight and measure the gap between the seat tube and string. If there is a decent difference then take it to a frame builder to fix.

[oldpotatoe]

Is the dish on the wheel correct?

A basic way to check is to tie a bit of string on the lefthand drop out and run it upto the head tube and back to the righthand dropout, pull tight and measure the gap between the seat tube and string. If there is a decent difference then take it to a frame builder to fix.

I would agree. A decent bike shop will have a frame alignment gauge or similar but if it's just the rear triangle, a good bike shop can align and space dropouts properly.

BUT of course, check wheel dish. Turn wheel around in frame. If the wheel isn't dished, it will be closer to the other side. If it's the same, frame/rear triangle, rear alignment. BUT, if aligned and parallel and the wheel is still oit chould be other things like chainstay lengths, dropout lengths, etc.

[unterhausen]

check the dish. If the dish is good, leave it alone. I don't know how many framebuilders I would trust to check that alignment. If you take it to a shop, you'll get some variation on the string test, which really doesn't tell you anything. Steel tubes aren't straight anyway, so the string test is totally bogus.

[David Kirk]

Put your wheel in the rear and note to which side, and by how much, it's off center.

Now take it out and put it in backward and see if it's the same or if it's now off to the other side.

If it's the same the frame needs looking at.......if it's off to the other side the rear wheel needs looking at.

dave

[druptight]

You can also check to see how close the crank arms come to the outside of the chainstays on either side when in the 9:00 position. Assuming you've got chainstays that aren't somehow different on either side (crimped, or asymmetrical somehow), they ought to be fairly close to the same distance from the chainstay on either side.

[Web1111a]

How much is enough to worry about

Using the string method described I have a 3.75 mm difference between left and right

[druptight]

How much is enough to worry about

Using the string method described I have a 3.75 mm difference between left and right

Can you ride the bike no-handed? Do you have shifting or wheel issues? If the answer is yes to no-handed and no to other extenuating issues, I wouldn't worry about what the string method tells you.

[David Kirk]

How much is enough to worry about

Using the string method described I have a 3.75 mm difference between left and right

How much is enough? That's hard to answer with a firm number. I would say that nearly 4 mm is way more than enough to cause an issue. That is a big number.

dave

[Web1111a]

Been having issue with front derailleur shifting to small ring sometimes it seems to get stuck in between rings or it throws the chain off usually under load

Frame is a Merckx Corsa extra Reynolds 753

Bike is very stable handles great I will have to try the no hands test and find a shop that can do alignments


Any issues with Aligning 753?

I assume rear stays and chainstays are not 753

I know it is supposed to be a tough metal

[stephenmarklay]

Thank you so much everyone. I will check the dish first and go from there.

[pgrizzwald]

I recently had a similar issue after having the rear stays on my Columbus SL Bertoni spread. The frame was in alignment, but the wheel kept creeping toward the left chainstay and even jammed the tire against it on two occasions. I was pretty worried, but did a little research and discovered it was simply due to weak skewers. I was using some external cam skewers that came with my 3T wheel. My dropouts are also semi-horizontal, so you need some serious clamp force to hold the wheel in place and prevent slipping. Solution: use a steel internal cam skewer! Or if you want to get fancy, you could drop some $$$ on the Dura Ace/Ultegra internal cam skewers. But, in my case, a simple old school steel internal cam skewer has solved the problem, because it has a greater clamp force than external cam type skewers, and the serrated steel teeth on the skewer hold tighter on steel dropouts. That's why a lot of external cam skewers have serrated steel tooth inserts inside aluminum/plastic on their clamping areas. This might have nothing to do with your issue, but if it does, this is a simple fix.

External cam skewer
http://2.bp.blogspot.com/-yn6Y5i2PVPc/UhyalmwJJaI/AAAAAAAAFpY/UcUaQFFswRM/s1600/IMAG0946.jpg

Internal cam skewer
http://www.os2.dhs.org/~john/zeus-2000-skewer.jpg

[Mark McM]

How much is enough? That's hard to answer with a firm number. I would say that nearly 4 mm is way more than enough to cause an issue. That is a big number.

dave

This makes me wonder about another thing: How symmetrically are frames built, and does it matter?

Clearly, the wheels and the steering axis need to be aligned for correct handling and tracking. But does it matter if the chainstays aren't symmetrical, or the seat tube is a bit off-center, as long as the wheels & steering are aligned?

Take for example frames with BBRight bottom brackets (like most Cervelos). The 79mm wide BB shell is purposely off-center (the right face is 34 mm from center, and the left face is 45 mm from center) and likewise the chainstays are usually non-symmetrical, with the left chainstay more outboard than the right. Yet I have heard of no particular handling problems with bikes with BBRight bottom brackets.

The infamous "string test" for rear triangle alignment relies on the seat tube to be perfectly straight and in plane. But if the seat tube wasn't perfectly straight and in-plane, couldn't the string test give a false positive, even if the rear dropouts were perfectly aligned?

[chiasticon]

Been having issue with front derailleur shifting to small ring sometimes it seems to get stuck in between rings or it throws the chain off usually under load

Bike is very stable handles great I will have to try the no hands test and find a shop that can do alignmentsyeah if you're having the chain fall off the big dog while under load in the bigger sprockets, something's not right (assuming your hanger is aligned and everything is otherwise dialed-in correctly, of course). personally I'd recommend contacting a frame builder if there's one in your area. they'll generally have more experience and tools than a shop (shop doesn't have an alignment table, for example) and you'll get a cool look into the world of frame building. win-win.

[David Kirk]

This makes me wonder about another thing: How symmetrically are frames built, and does it matter?

Clearly, the wheels and the steering axis need to be aligned for correct handling and tracking. But does it matter if the chainstays aren't symmetrical, or the seat tube is a bit off-center, as long as the wheels & steering are aligned?

Take for example frames with BBRight bottom brackets (like most Cervelos). The 79mm wide BB shell is purposely off-center (the right face is 34 mm from center, and the left face is 45 mm from center) and likewise the chainstays are usually non-symmetrical, with the left chainstay more outboard than the right. Yet I have heard of no particular handling problems with bikes with BBRight bottom brackets.

The infamous "string test" for rear triangle alignment relies on the seat tube to be perfectly straight and in plane. But if the seat tube wasn't perfectly straight and in-plane, couldn't the string test give a false positive, even if the rear dropouts were perfectly aligned?


Good questions all -

From my experience.........

- if the two wheels, the head tube and the saddle are all in the same plane then the effective alignment is good. How one connects the dots will matter little.

- the BB being off center relative to the main plane of the frame is more of an ergonomic issue and less of a handling thing. The offset BB will mean that the lateral hip angles (how much the feet are offset from bike and body center) will not be the same. How much does this matter? I don't know. Most crank sets have a small amount of offset and put the pedals unequal distances from the bike centerline and this is never talked about so I suspect that a little offset isn't an issue. As that offset grows it would of course become and issue but I don't know of a number where the tipping point is reached.

- the string test is never an exact way to measure alignment but it's most often a simple indicator that says things are close.......or not. If the seat tube is bowed to one side then that will throw off the results. That said most any non-crap tubes will have less than 1 mm of TIR (total indicator reading) of run out which means that it would be less than 1/2 mm bowed. So if the string test is showing 4 mm on a metal bike the chance that something is wrong is really high.


Years ago - for the fun of it, and out of complete boredom, I built a down-and-dirty frame that looked WAY out of line. Nothing was symmetrical, level, or straight.....yet the alignment was spot on because the saddle, head tube and both wheels were in the same plane. How the dots were connected was another matter.

So many years ago a good woman Carol (customer service) at Serotta took a call from a guy who said his new Serotta was off in a way that made his knee hurt. She did her best to understand the guy but in the end had no idea what he was talking about. His call made it to my desk and he then explained that the bike (CSi I think?) had S bend chainstays and that the curve of the two stays was very slightly different and ....... follow me here....... this made his knee hurt. I did my best to explain that this was impossible and that even if the tubes had a different curve to them that this would not bother his knee. I asked if he was running the same exact saddle (no he wasn't) with the same exact set back (didn't know what setback was so the answer was no) and suggested this could be the cause of his knee issue. He wasn't buying it and "knew" without a doubt that the chainstays caused his knee issue.

I had the office issue him a full refund and got the bike back and it was, surprise, just fine.

Go figure.


dave

[stephenmarklay]

I am glad I posted this as I have learned a thing or two. This may not be an issue as I have not ridden the bike yet. I just noticed it and thought hmm.

I actually think I remember this with my old Serotta CR and I never looked deeper and never had an issue.

[Mark McM]

- the BB being off center relative to the main plane of the frame is more of an ergonomic issue and less of a handling thing. The offset BB will mean that the lateral hip angles (how much the feet are offset from bike and body center) will not be the same. How much does this matter? I don't know. Most crank sets have a small amount of offset and put the pedals unequal distances from the bike centerline and this is never talked about so I suspect that a little offset isn't an issue. As that offset grows it would of course become and issue but I don't know of a number where the tipping point is reached.

With (properly designed) BBRight bottom brackets and cranks, the pedals/cranks are not offset. (See: http://www.bbright.net/)

The concept behind BBRight is that the bottom bracket shell should be as wide for frame striffness. There are drivetrain clearance issues on the right side (due to the chainrings), so there is a limit on how offset the chainstays/BB shell can be on the right, but these limitations don't exist on the left, so the left side chainstays/BB shell can be offset more. Thus, the BBRight BB shell is wider on the left than on the right.

This BB shell asymmetry on BBRight bottom brackets is corrected by the design of the BB bearing cups or by spacers on the crank axle. For example, for Campagnolo Ultra-Torque cranks/cups, the left bearing cup is inserted entirely internal to the BB shell, but the right cup extends about 11 mm outside the BB shell, so that the bearing placement becomes symmetrical, and the cranks/pedals are also symmetrical. For PF30 cranks/cups, the cups will both be internal to the BB shell, and a spacer will be placed on the right side of the crank axle to make the cranks/pedals symmetrical.

(I am not a BBRight apologist - I think it is an unnecessary mish-mash. The last thing we need is a new BB standard. I bought a Cervelo despite the BBRight bottom bracket, not because of it.)

[David Kirk]

With (properly designed) BBRight bottom brackets and cranks, the pedals/cranks are not offset. (See: http://www.bbright.net/)

The concept behind BBRight is that the bottom bracket shell should be as wide for frame striffness. There are drivetrain clearance issues on the right side (due to the chainrings), so there is a limit on how offset the chainstays/BB shell can be on the right, but these limitations don't exist on the left, so the left side chainstays/BB shell can be offset more. Thus, the BBRight BB shell is wider on the left than on the right.

This BB shell asymmetry on BBRight bottom brackets is corrected by the design of the BB bearing cups or by spacers on the crank axle. For example, for Campagnolo Ultra-Torque cranks/cups, the left bearing cup is inserted entirely internal to the BB shell, but the right cup extends about 11 mm outside the BB shell, so that the bearing placement becomes symmetrical, and the cranks/pedals are also symmetrical. For PF30 cranks/cups, the cups will both be internal to the BB shell, and a spacer will be placed on the right side of the crank axle to make the cranks/pedals symmetrical.

(I am not a BBRight apologist - I think it is an unnecessary mish-mash. The last thing we need is a new BB standard. I bought a Cervelo despite the BBRight bottom bracket, not because of it.)

I understand that.

I was mostly referring to the potential asymmetrical stiffness one could see with the BB shell being wider on one side than the other.

dave

[lhuerta]

I am glad I posted this as I have learned a thing or two. This may not be an issue as I have not ridden the bike yet. I just noticed it and thought hmm.

I actually think I remember this with my old Serotta CR and I never looked deeper and never had an issue.

Steel frames do not spontaneously combust/explode/bend unless they are severely rusted or you crashed. If neither has occurred then the issue is likely ur wheel dish.

[unterhausen]

If the string test says x on one side and x+4 on the other, then that means (assuming perfectly straight tubes) that the seat tube is 2mm off center. And that's assuming that it was properly done. When I have been desperate enough to try it, I find it's easy to get that kind of measurement error.

[stephenmarklay]

Again this was instructive for me.

I took the advice and this is not a frame issue. It is the dish after all.

I will fix that ASAP.

[Black Dog]

Again this was instructive for me.

I took the advice and this is not a frame issue. It is the dish after all.

I will fix that ASAP.

Good news! :)

[stephenmarklay]

Good news! :)

No doubt. I honestly was not too concerned but dish is an easier nut to crack. I am fixing the wheel tomorrow.