Chainline Question

what dimensions would be required ?

I didn't want to start a new thread for inane chainline questions, so I'm hijacking this thread a little, sorry.

Currently I have a perfect chainline with Sugino RD2 Cranks, Chainring and BB (103mm) with GranCompe hub and Surley sprocket. I want to upgrade to the Sugino 75 cranks which suggest to be paired with their own 109mm BB's.

Is the different size in BB length because the cranks sit slightly differently on the axel, or the chainring sits deeper? Should I be keeping my 103mm BB or swapping out for the 109mm BB to keep my perfect chainline?

Thanks
Monsta

Hi,
I'm converting an old frame to a fixed gear. Was thinking of using a Campy crankset from an old road bike with only one ring on it. Is there an easy wat to figure out what size BB ill need to to get a good chainline?

Thanks

Sigh

Sheldon is your friend:

http://sheldonbrown.com/chainline.html

Thanks

Can anyone give me some advice.

I'm beginning to get parts together for a new build and am thinking about running Mavic Ellipse wheels with a Dura Ace cog and Sram Omnomnom cranks.

Has anyone run this set up before, and is the chainline any good?
I've tried to search online but haven't found any real answers.
I'm guessing the fact that the omniums use an external cup bottom bracket may make a difference.
As it's going to be a fairly pricey set up - hopefully Sugino 75 chainring, and dura ace stuff I want to treat it properly and get it spot on..

any help would be awesome.

Cheers

anyone haz any ideaz?

Have you checked the transmission database bro?

^ no? what be that?

http://www.lfgss.com/thread3372.html

^ Nice one lads

Hey,

I have been "googling" for the past 2 hours to get my head around general considerations with BBs and chainline to no real avail.

I am getting a Dolan Pre Cursa (68mm English BB size) and a set of Ambrosio Prestige Cranks (ISO taper) from a friend to go with it.

Thing is...what BB spindle length will I require? What BB will I need to be as close as possible. Will be getting some (cheap, I know) Planet X AL30 track wheels, which do have some good forum reviews tbh.

http://www.lfgss.com/thread3372-12.html#post3549281

^this is all you need..

Transmission database - for all your crank / bb / bottom bracket questions

Didnt see it there :(.

I have seen bits about the pre cursa's chain-stays flaring out a bit and people resorting to longer than recommended lengths in some cases.

Would running 4-5mm out be the end of the world for a couple of steady months before getting a miche crankset or the like? May just get a 111mm ISO BB and hope for the best :|.

It won't kill you dead or make you drop a chain unless you've got mega low chain tension, but it will increase wear and noise. You could always use a Miche Primato BB (and I happen to have a 107mm one...). They're not the best BBs and take some effort to set up right, but they do give you a lot of adjustability.

Am I fighting a losing battle here? Trying to run a mtb triple chainset with a road bike but the angles don't look to clever. Maybe I should just bung a double on.

Apologies if this has been covered before.....

if I stick enough spacers behind the sprocket of my Goldtec hub to achieve a perfect chain line with the chainring, I'm left with only 3 to 4 mm's worth of thread available on the hub for the sprocket to be screwed onto.

To my mind that's a recipe for disaster of the stripped thread kind.

So, my question is - how critical is the chain line? And would it be ok for it to be out by 2 or 3 mm's.

TIA

The chainline is extremely important, it's the main reason to ride with a single cog. You are correct about using spacers, it is the worst way to adjust chainline, and it is a recipe for disaster.

If the hub has any possibility to juggle the axle spacers, this is the easiest way to move the chainline in the rear. You will have to redish your wheel. You can also move the chainring in by installing a shorter crank spindle, or using spacers to move the chainring in.

Good luck and let us know how it works out for you.

Thanks, bikeguy.
An hour or so of sweaty palms and blue air later, and it looks like installing a BB with a 113mm axle as opposed to 119mm should give me the reference points I am looking for. Thanks for the prompt response.
I will come back to let you know if I've won.

Job done.
108mm BB axle fitted - giving an nigh-on perfect chainline.
Had to put a spacer between the lock ring and cog, as the lock ring was bottoming out against the larger thread (therefore ineffective) rather than the cog.

I think this is fairly self-explanatory

In case not:
I have a bottom bracket of 119mm.
Rear hub is 135mm.
The cranks are an old cheapo all in one single piece, so cant move the chainring on to the outside of the spider or anything like that.

The "line" is 9mm out. I need to push the chainset out more.

What size bottom bracket do I need to buy to straighten it up?

136mm seems enormous, also not sure if you can get them...

1 Attachment

ISO square taper

I'm doing my my first fixed build and I'm trying to avoid a chainline error.
If you can help, your advice is appreciated.

What I have:
Steel frame
BB: 68mm shell english thread
With Shimano double 113mm spindle length BB (already installed)
Rear dropout spacing 126mm
An SR Royal double crankset (outer ring chain line 46mm (I think - am I wrong?))
Need to buy: Rear wheel

I would like to use the chain line on the outer ring for aesthetic purposes therefore I think would want a 46mm chainline for the rear wheel. (or am I wrong)

What is the best way to achieve this? I would like you buy a wheel and don't want to have to redish anything. My knowledge of fixed rear wheels is bad.

Ie is this possible
Buy a 120mm wide rear wheel (this is standard right?) Which would have a 42mm chainline. Add 4mm of spacers each side and on the drive side have the cog 4mm over? (what do I buy). Giving the rear wheel a 128mm width which should fit in the 126mm dropouts, and keep the wheel centred?

If you bothered to read that thanks!

The chainline is taken from the middle point between the 2 drop outs

4mm spacing on each side won't move the hub as you have mentioned so chainline won't change.

You can't move the cog on a fixed gear hub, it screws into one place only.

You will likely need to redish, which isn't rock science. Tighten non-drive spokes, loosen drive side.
Read here for help: http://sheldonbrown.com/deakins/how-to-fixed-conversion.html