Chain line question. Please Help!

[fstrthnu]

Hello All,

If I wanted to achieve a near perfect chain line for a single speed mtb using a:

1. Tune Fastfoot Crank 110/74 MTB Spider.

2. Phill Wood rear hub with 54mm of offset.

What width BB would I need to use? a 113 of a 117? Also, The ring will be mounted on the outside of the spider.

Many Thanks,
Fstrthnu

[obtuse]

depends on the frame. you'll probably need to guess and if it doesn't work try the other bb combination.

obtuse

[Ti Designs]

Each crank has chainline offset numbers for both inner and outer ring positions, as do bottom brackets. We know the offset for the hub, and as long as the hub's over-locknut dimentions are the same as the bikes dropout spacing (and making the bold assumption that the frame is aligned), it shouldn't matter what the frame is. My bet would be that the nerds on the weight weenie board would have those carnk/bb numbers off the top of their heads. They'll also tell you the difference in weight between the 113 and 117 BB and make all kinds of suggestions about chainrings, gearing and which stack bolts to use.

I'm with Obtuse on this one. Throw the bike on the stand, start with the 113 if you want to run the outside position, put the wheel on the bike with the cog on, mount the chainring, take about ten steps back and sight down the chainline. Italian frame builders like to use their thumb as a gauge - not sure how that works...

[Marcusaurelius]

Every crank manufacturer I've seen always has recommended bottom bracket length for their cranksets. The newer 110/74 cranks (sugino xd) use 110mm-113mm depending on your frame as previously mentioned. Of course the older shimano 110/74 were mostly in the 122.5 range. I don't suppose the crank manufaturer has a website? (I couldn't find any tune website, itune but no tune)

[DfCas]

But in my experience I have found that mounting the chainring on the inner side of the crank gives the best chainline with thread on rears.That said,I would take a WAG and say try the shorter BB spindle since your ring will be on the outside.