Chainline confusion

DirkVoodoo

Yes, once again my ineptitude with fixed gear/singlespeed bikes is on show.

My 08 Felt Dispatch came with FSA Vero Cranks (square taper, 130mm BCD). I found this little bit of information from VeloSolo Shop:

FSA Vero Single Chainset

Popular single ring track chainset found on many off the peg fixed wheel bikes. Ideal for any singlespeed or fixed wheel new build or conversion. Forged aluminium arms complete with 48t chainring.

BCD is 130mm. Choice of 165mm or 170mm lengths. 165mm in black finish with 1/8" chainring. 170mm in polished silver finish with 3/32" chainring (also usable with 1/8" chain. Complete with crank fixing bolts. Requires 110mm bottom bracket with JIS (Shimano type) taper. See UN40 bottom bracket for more and FAQ for advice on different BB tapers.

I'm pretty sure the rear dropouts are 120mm wide. The stock bottom bracket is an RPM square taper model. I will have to check the label again, but I'm nearly certain Felt's description is right, which is:

FSA 68mm w/ Forged Chromoly Square Taper 107mm Spindle

I have always thought the chainline didn't look perfectly straight, but now I'm a little confused as to what to go with. A 110mm JIS seems like the obvious choice, but which one? Are 110mm shimano style bottom brackets all symmetrical? I saw one or two random posts saying that 110mm spindles will give you the required 42mm chainline for 120mm wide dropouts, although I'm not sure if this will be different for a singlespeed over a fixie.

I want something of better quality than the RPM model, it's pretty nasty (9 euro on CRC should give some idea as to the quality) and I can hear the bearings grinding away when I spin the cranks.

I like the look of this Token one, and the price is right, 111mm spindle though, is this a problem?

The Shimano UN54 seems well priced, but I would prefer something of slightly better quality.

LondonFGSS mention another RPM model, available on PBK and it's this one I'm leaning towards if I get the thumbs up from someone who knows their chainlines and fixies.

redmaxi

"I usually check the chainline by installing the hub in the bike, with no chain installed. By placing my head just in front of the chain wheel, I can sight along the chainwheel and see back to the rear hub, to see if the chainwheel lines up exactly with the rear sprocket. If it doesn't, I re-arrange spacers or change the bottom bracket axle as necessary."

By The late great Sheldon Brown

TinyExplosions

Found on t'internets...

one thing to consider is they use FSA's proprietary Power Drive spline system bottom bracket which is roughly the same diameter as a square tapered BB but there's a 99% chance your LBS won't have it in stock...

Also there's stuff about it coming n standard square taper (but if that's ISO or JIS (Shimano), I don't know!).

The Token one should do you fine, I wouldn't worry about the 111mm, or go for Shimano... buy cheap and buy often

it's mick

don't buy the token one!! it's got an iso taper which is narrower than the jis (shimano type) taper that your crankset needs. this does matter because a jis crank will set 4-5mm further down a jis spindle.
as for the 107 vs 110 the difference in chainline will only be half of 110-107=3. so only 1.5mm which really doesn't matter (infact i currently have a bb on my bike that pushes my chainline out by 2mm). i would be inclined to stick with 107mm since that's what's already in there though.
if you want i have a 107mm shimano un54 which i bought after making the iso vs jis taper mistake the other way round! it's never come out of the box which is still sealed, you can have it for a tenner if you want.

so, to wrap up here. buy a shimano bb either in 107 if you trust the bike manufacturer or 110 if you trust the crankset manufacturer

DirkVoodoo

Cheers Mick, I could have sworn the token was JIS, nuts!

I'll take the bottom bracket, where you based?

Thanks all for the advice.

it's mick

i'm based in drumcondra but i can meet you in town. just shoot me a pm and we can arrange something.