Maximum Allowable Chainline Deviation?
 

There are a lot of discussions about correcting Chainline, but I can't find any discussing what is an acceptable deviation. on a single speed, Fixed gear or internally geared Hub bike obviously

If its close to straight, (say a few mm out) is it worth the trouble of respacing and re-dishing a wheel just to get those last couple of mm in line?

How much mis-alignment or deviation in Chain line is acceptable?

I searched and couldnt' find an obvious thread.

It's acceptable when you can tolerate the noise, the extra drivetrain wear and when it doesn't drop the chain on every bump. I accept no less than near perfection for noise reasons.

If this is for a freewheeling bike just add a tensioner that is aligned correctly and get the best of both worlds. It still will be louder than a straight chain, but should be ok. It won't wear your cog and chainring down as much.

The "safe" deviation would depend on cog/chainring type, size, wear, trueness, etc. The chain itself will have a huge role in this, most 1/8" chains have much less latitude for side to side motion than a 9 speed chain would (as you could guess). The safe latitude is just whatever the range is that you won't drop the chain.

1mm

My singlespeed mountain bike chainline is off about 6-7mm because of a seriously mismatched BB and crank (will fix this soon). Anyway, its still fairly quiet and I've never dropped the chain. Road bikes function well with the chainline off by several cm. You can't get away with that with a SS chain, but you can still get away with a lot of slop in your chainline. Nonetheless, I'd still aim for getting it to within 1-2 mm. If you are measuring your chainline with just a tape measure or even a digital calipers, you're measurement error is going to amount to 1-2 mm anyway, so don't expect it to be absolutely perfect.

you can have plenty of chainline deviation. there may be some increased wear - may or may not be noticeable. same goes for noise - may or may not be noticeable. if your chain tension is proper and your chainring is close to round (out of round chainrings lead to unevenly tensioned chains - tight spots and loose spots in the rotation), you won't throw a chain.

teiaperigosa, most people can't accurately measure their chainline to within 1mm.

i'd say that within 10mm, you're fine, but that's just a guess. i've certainly ridden setups with bad chainlines - with absolutely no problems.

1/8" chains have plenty of side to side movement, though not as much as a 9 or 10 speed chain, obviously. try this. remove your chain from your bike. hold it at one end, let the rest dangle. move it from side to side. feel how much movement it can handle. plenty.

I'd say it could be in the 6-7-8mm range without big problems.

Unless you've got the proper measurement tools, the ability to get the chainline within +/- 1mm is doubtful.

I think a chain 1/4" - 1/3" of an inch off might be noticeable.

A ruler and a pen and paper?

A caliper is the best. With rulers, you're always eyeballing somewhat (you can't exactly put the ruler flush with the elements that you're measuring).

i have no clue as to how to measure this.

I've been eyeballing my chainline. I put a yard stick against the chain and look to see if it seem parallel to the downtube.

I'm finding that 3/32" 8 speed chains make much less noise then 1/8" It must be because derailer chains are designed to flex and so can take more misalignment?

Yeah, you can't get correct chain line measure without calipers. How I do it is measure the seattube width, than the distance from center of ring to the far end of the seat tube (farthest away from you) and than take that number and subtract it with one-half the seat tube.

digital caliper.

Just eyeball it until you can't tell if it is off to one side or the other.

5mm. i wish i could remember the guy's name, an olympic mechanic who said that, and i think it's pretty much always worked for me.

edit: whoops, not asking about fixed. carry on.

yeah i would agree... just make sure your chain tension isn't totally off and you shouldn't have any problems..

2mm is where it starts to get too loud for my taste, though my general answer to this question is "get it exactly right." Measuring with calipers works pretty well, but you are assuming that your frame is perfectly aligned. Wooden yardsticks are guaranteed to be off at least a little. I have a good steel carpenter's square that I use by laying it flat against the chainring, then I check against the calipers. There used to be a park chainline gauge, but they don't make it any more and it was kind of jingus anyway.

Sorry, but I did mean - Fixed Gear, Single Speed or Hub geared (without using a chain tensioner).

I was just curious abotu what peopel consider too much. - My last two fixies were pretty rough and ready conversions... I didn't worry much abotu the chain-line. I just eyeballed it from the rear and thought - yeah thats 'kinda straight' I think... although it was noticably off a little.

it may have even been say 10 mm off - I don't really know. but it was pretty quiet and the chain never fell off.

but then yesterday i was watching the new Bobs Garage video which covers chainline and i thought - hmm maybe I shoudl be more concerned?

http://www.fixedgeargallery.com/colu...age/indexb.htm

I think getting it down to 1 - 2 mm out is enough isn't it? ther eis quite abit of lateral movement in most chains.

:rolleyes: but most gully people can

The closer your chain is to perfect, the less chance you will have to throw a chain. When I first started riding a fixed, I would break chains and occasionally through them. I remember my cog was about 15 mm off from my CR. I still rode the **** out of the bike and 99.9% of the time life was good.

My cog and CR are now dead on because of an adjustable bb. I have not broke or thrown a chain in about 4 years.

I do not know what my chainline is. I use the method Landgolier mentioned about lining up a straight edge (I use a three foot aluminum carpenters level) on your CR. This is most important to me, having the cog and CR perfectly in line.

From.... http://sheldonbrown.com/gloss_ca-m.html#chainline

Chainline Measurement