Sugino RD2 messenger cranks and BB help

[Baxter22]

G'day,
I recently broke the original chain ring and right crank on my schwinn single speed (not a fancy bike but she gets the job done each day) as a result of an unfortunate incident with a car trailer.

The happy result from it is now I can upgrade the drivetrain. I am looking at Sugino RD2 messenger crankset and a 103mm BB. I can get a cheap deal for all up $159.
The problem I have is that I'm not sure this will fit the bike properly and just need a spot of re-assurance from my singlespeed/fixed brethren. The old set up on the bike is 46T, 170mm crank length (spider on the outside of the chain ring), 45mm chain line and a cheap bog standard 68mm bottom bracket (square taper) 113.5mm.

The potential new Sugino set up will give the same 45mm chain line length (it says so on the box anyway) but on a much shorter bottom bracket than I currently have.
My question is can I go with the recommended Sugino set up of a 103mm BB or should I go one that is a bit longer in length (108mm an above). I could experiment with BB sizes but would rather stay away from buying more than one in case it doesnt fit.

Any help would be much appreciated.

Cheers

[slidetaker]

Internet search results show discrepency...

Find a good bike shop that are willing to try for you.....or buy some BBs to try and sell off...

Good thing is you only need to do this once.....

[HappyHumber]

I am pretty sure I have run Sugino branded 103mm cartridged sealed bearing on my set of RD2s. They were originally supplied on a complete Surly Steamroller, but subsequently ridden on a couple of converted FG frames.

Look at the info here and there. Harris Cyclery via Sheldon Brown leak a lot of handy little reference info out there their via their product/item descriptions. See if you can find the Sugino 103mm unit, confirm taper type (still slips my memory all the time and then see if there there's a same taper type 103mm "Home Brand" unit around cheaper.

I am sure since I replaced my there are more 103 cheapies on the market.... probably since the FG fad has peaked and there's lots of such bits in the market. I still like the RD cranks over a lot of others that have appeared since.

edit : Yep, just checked mine. the Sugino model is CBB-103. Easily checked because the parts are all in the same box awaiting the next frame prep.

[slidetaker]

It would help the OP a lot if you could quickly check the chainline of your RD2 with 103 setup.

Is it closer to the standard 42mm or outward like 45mm?

[HappyHumber]

It would help the OP a lot if you could quickly check the chainline of your RD2 with 103 setup.

...the parts are all in the same box awaiting the next frame prep.

Hard to measure with the bits all in a box. I had this set up on firstly a Surly Steam Roller frame, then later on a 80s Ricardo conversion which probably needed some slight cold setting and alignment running with the hub. I also had a Surly dingle (2x fixed) cog for a while which ran perfectly on either cog despite the slight shift in chainline when I manually changed the between the cogs.

My point is - chainline isn't the exact lazer-aligned trigonometry some people would have you believe. My advice, from my experience with that crank & bb set up would be stay with the 103 Sugino or equivalent width tapered BB.

[Baxter22]

Just to add some closure to the thread and possibly help other fellows in the future I'll update the completion of the problem I orginally posted.

I bought 172.5mm 44T Sugino RD2 messenger cranks online and quite cheap. Took a punt on bottom bracket lengths and went with the recommended length offered by sugino after much research on the internet and forums (BB length 103mm). Bought a FSA 103mm BB square taper for $35 (shiny and chrome so matches the cranks). The big risk was that the old set up had a longer BB (113.5mm) and a 45mm chainline and the new set up (being 10mm shorter) wouldnt give the same chain line distance. I also didnt want to buy 2 BB's of differing length and then either sell the one that didnt fit or keep it as a spare, not that they are expensive just seems a bit wasteful.

Bought the cranks first and when they showed up the crank spider sits on the outside and there is a ~10mm "stem" or "neck" on the inside to fit onto the bottom bracket spindle (which you dont see on any photo of the cranks or described in the specs from Sugino). With this in mind it appeared that I could confidently buy a 103mm BB and it'd all work out nicely.

Put it all together last week and it fits perfectly and rides like a dream, so smooth and silent I wish I'd done it sooner. Coupled with a new chain and some TLC its a whole new bike.

Thanks for the help and turns out the problem was solved with a bit of research, a bit of a punt and some elbow grease. Came at a week or 2 delay but well worth it to get it right. I'll post a photo soon.

Cheers