kimjmoon

Hi all, I have a Raliegh One Way single speed steel frame touring bike that I rode last year on a 6 day supported tour across Lower Michigan. I was running a 42t chainring and 20t rear cog and for the most part it worked fine. I had trouble on a few long steep hills and couldnt keep up with my friends on thier road bikes on the flats. 18mph had me spinning like a hamster on a wheel!

This year I have decided to upgrade to a Sturmey Archer 3 speed using the same chainring/rear cog combo. Here is my question:

I want to run the Velo Orange Grand Cru crank arms and the Grand Cru 42t chainring. They suggest a minimum of 116mm square taper bottom bracket length, but the one I just removed was 108mm.

I was thinking about installing the white industries titanium square taper BB but it only comes in 113mm or 121mm lengths.

Is it correct to assume that this will affect the chainline distance and can it be corrected with spacers on the cogs or will the 113mm just not work?

Here is a pic of the bike.



Thanks in advance

loubapache

Nice bike.

I am not sure which SA 3-speed hub you are going to use but many (such as the older and reliable AW) come with a dished cog so you can install both ways to adjust the chain line. You can also move the large cog spacers around as well. IIRC, dish in and dish out can have enough movement to have straight chain line from the middle chainring to the outer chain ring in a double chainring setup. It will definitely have enough for the 5 mm you are concerned about.

Then add/move axle spacer can also correct slight chain line issues.

mihlbach

Either of those bottom brackets will probably work as long as your chainring doesn't hit the chainstay. However, you should forget about Velo oranges recommendations. First find out the chainline of the hub you are getting...then you'll know how far you need to deviate your chainline (if at all) from Velooranges defalt recommendation. For a symmetrical BB spindle, the chainline difference is only half the difference of spindle lengths, so its not hard to get it within a few mm of straight either way, which is more than good enough. And as loubache notes, there are ways to tweak the last bits of error out of your chainline.

Six jours

I used V/O cranks with a Sturmey FM hub, which I believe puts the cog in the same spot as the AW. With a 116 spindle I had to put all the spacers on the outside of the cog in addition to running the dished cog so that it was as inboard as possible. I suspect that with a 108 spindle you will not be able to get a good chainline. If confronted with a choice between 113 and 121 I'd go with 121.

<edit> In your shoes I would buy the hub/wheel first and then measure with the existing crank/BB. That'll tell you what you need to know more accurately than any amount of figuring will.

kimjmoon

Thanks all for the quick replies......since I will have to rebuild my existing wheel to accomodate the SA srf3 hub, can I change the dish to compensate for any chainline differences? Or is the dish a statutory spec and need to use spacers? I had several broken chainring teeth and a sloppy BB so I have already removed the old and getting ready to install the new as soon as I make the purchase.

Steev

Wheel dish does not change chainline.

kimjmoon

Good to know, thanks!

mihlbach

Not directly, but redishing a wheel will alter your chainline in the sense that you will have to respace the rear axle to center the rim. So yes, redishing will necessite a change in chainline.