# Singlespeed & Fixed Gear - Calculating chainline given a few weird specs

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bellweatherman
05-13-06, 09:34 AM
Can you calculate chainline based on the following information given on Surly's hub specs page?
http://www.surlybikes.com/spew8.html

BTW, what does (C-T-F) on that page stand for?

christiank
05-13-06, 09:55 AM
Center To Flange.

The measurement from the center of the hub body to the center of a flange. Depending on the hub the C-T-F measurement will usually differ on for the left and right measurements on a rear hub to compensate for a dish. That is unless it's a double fixed hub where they would likely be the same.

MacG
05-13-06, 10:26 AM
I don't think you can garner any useful chainline info from what they give you there.

ken cummings
05-13-06, 10:28 AM
For chail-line would you also need the rear axle to bottom bracket distance. I visualize a trapezoid with three of the four sides being: 1. Chainring to centerline of bike, 2. bottom bracket to rear axle, 3. centerline to sprocket. The chainline is the fourth side. Simple trig gives the chainline and chainline angle. To be really picky allow for the different diameters of the ring and sprocket.

bellweatherman
05-13-06, 06:32 PM
For chail-line would you also need the rear axle to bottom bracket distance. I visualize a trapezoid with three of the four sides being: 1. Chainring to centerline of bike, 2. bottom bracket to rear axle, 3. centerline to sprocket. The chainline is the fourth side. Simple trig gives the chainline and chainline angle. To be really picky allow for the different diameters of the ring and sprocket.

Thanks for the dissertation, but I didn't ask for any of that.

bellweatherman
05-16-06, 06:39 AM
Well, so why would Surly give us all these useless measurements for singlespeed hubs, but not the critical one for figuring chainline? Makes no good business sense at all.

queerpunk
05-16-06, 07:26 AM
so, with chainlines, it's a pretty safe assumption that your hub (edit: if it's a track hub) will yield a 42mm chainline. to doublecheck, you can go to sheldon brown's database of Obsessively Accurate Dimensions of Things ( http://www.sheldonbrown.com/chainline.html ) and add the center-to-shoulder distance of your hub to the from-shoulder measurement of the cog you're using. that will give you your chainline.

for cranks, http://sheldonbrown.com/harris/fixed.html#cranks and businesscycles.com will give you the recomended bottom bracket spindle length for each crank in order to achieve a 42mm chainline.

Aeroplane
05-16-06, 10:11 AM
Most hubs that are intended for 135mm spacing (mountain bikes) will give a 52mm chainline. But most fixed hubs are 42mm, since they are "track" hubs.

bellweatherman
05-16-06, 10:33 AM
so, with chainlines, it's a pretty safe assumption that your hub (edit: if it's a track hub) will yield a 42mm chainline. to doublecheck, you can go to sheldon brown's database of Obsessively Accurate Dimensions of Things ( http://www.sheldonbrown.com/chainline.html ) and add the center-to-shoulder distance of your hub to the from-shoulder measurement of the cog you're using. that will give you your chainline.

for cranks, http://sheldonbrown.com/harris/fixed.html#cranks and businesscycles.com will give you the recomended bottom bracket spindle length for each crank in order to achieve a 42mm chainline.

See, here's the thing. Yes, Sheldon has that chainline page up. And yes, that page is obsessive to get things measured just right with chainline, but unlike track hubs and track cranks, 135mm mtn hubs and chainlines for such vary drastically.

The manufacturers for track hubs stay within about +/- 1mm of a 42mm figure when you add on just about any track cog. However, mtn 135mm hubs are a totally different story. Most, if not all, mtn 135mm hubs are no where in the neighborhood of a +/- 1mm difference of 52mm. Really. And once you get more than about a 1mm difference in chainline, then life truly sucks because of your bad chainline creating more dropped chains, higher wear, etc.

queerpunk
05-16-06, 10:38 AM
See, here's the thing. Yes, Sheldon has that chainline page up. And yes, that page is obsessive to get things measured just right with chainline, but unlike track hubs and track cranks, 135mm mtn hubs and chainlines for such vary drastically.

The manufacturers for track hubs stay within about +/- 1mm of a 42mm figure when you add on just about any track cog. However, mtn 135mm hubs are a totally different story. Most, if not all, mtn 135mm hubs are no where in the neighborhood of a +/- 1mm difference of 52mm. Really. And once you get more than about a 1mm difference in chainline, then life truly sucks because of your bad chainline creating more dropped chains, higher wear, etc.

yup, sorry about that. i confess to answering without looking at the link and properly understanding your question. seems like your best bet is to get your hands on a hub and put a ruler to it. maybe there's an lbs that has one? or a friend with one on their bike?

trackasaurus
05-16-06, 11:13 AM
i am running that hub on my ss cross bike as a fw....

on my bike, the centre of the acs freewheel cog sits about 12-13mm from the outer flange of the locknut. 135mm/2 - 12.5mm = 55mm

however, your chainline depends on wether you're running a freewheel or fixed. as freewheel is a bit further outboard than a track cog which sits about 2mm closer to the hub flange.

i'm running a 135mm 1x1 hub, with an acs freewheel, truvativ 113mm bb and rouleur double road cranks, with the ring on the outside of the cranks. my chainline would be straighter if my front chainring was about further 2-3mm outboard.

i've seen that 1x1 hub run with alot of triple cranks, with the ring on the outside of triple cranks, with bang on chainline.

most bike that i've seen who are running triple mtn cranks or double road cranks, and a bashguard, have swapped out their bb's for longer ones.

hope this helps.

Sheldon Brown
05-16-06, 11:16 AM
Well, so why would Surly give us all these useless measurements for singlespeed hubs, but not the critical one for figuring chainline? Makes no good business sense at all.

The measurements hub suppliers commonly provide are for calculating spoke length, not chainline.

I don't know of any hub manufacturer who gives precise dimensions relating to chainline, that's why I measured all of those hubs and sprockets.

Sheldon "Dial Caliper" Brown

+-------------------------------------------------+
| One measurement is worth 50 expert opinions |
| --Howard Sutherland |
+-------------------------------------------------+

bellweatherman
05-16-06, 07:54 PM
The measurements hub suppliers commonly provide are for calculating spoke length, not chainline.

I don't know of any hub manufacturer who gives precise dimensions relating to chainline, that's why I measured all of those hubs and sprockets.

Sheldon "Dial Caliper" Brown

+-------------------------------------------------+
| One measurement is worth 50 expert opinions |
| --Howard Sutherland |
+-------------------------------------------------+

Your site is one of the only ones, actually the only one that I know of that has some listed figures for chainline. And it is a fantastic resource, no doubt. The only thing is that a couple of the measurements on that page a off. For ex: the Kogswell center to shoulder width measurement is off by about 2 mm. You probably are aware of the fact that Formula and some other company manufacture the same hubset rebranded as Kogswell, Iro, On-one, etc. With a cog of around 6-6.5, you would think that you would get close to a 52mm chainline as indicated by Iro's site. Actually, on-one publishes a different chainline spec for the same hub. Another ex: the Surly hub center to shoulder measurement is actually listed incorrectly I believe. Maybe I'm wrong, but the measurement is listed for an old 1x1 hub which isn't produced anymore and the measurement is different from the "new" surly fixed/free hubs. Perhaps, you got some bad info from two different sources? Don't get me wrong. I find your webpage highly useful for finding chainline info for track hubs/crank bb's, but mtn 135 hubs/bb's are another story.