chainrings... middle vs outer question

[Thomas Lynn Skean]

Hi!

Has anyone used the 46T Origin-8 chainring sold by RBW (or one like it) in the middle position on the RBW-sold Sugino crank (or one like it)? Any comments on how well it works or worked? If you got it to work "well enough" for you, was there anything non-obvious that you had to do to make that happen?

So here's the deal: I have three bikes, two Hillbornes and a Bike Friday (406BSD wheels). The Hillbornes have the triple Sugino cranks sold by RBW. The Bike Friday came with a 130BCD triple crank, 52T/42T/30T. I got rid of the 52T chainring because I never used it; higher than I want in general. Replacing the 42T middle chainring with a 44T was an improvement in the overall gearing on the Bike Friday and leads me to want to try a 46T.

However, as another goal I'd like to have the same Sugino 110BCD crank on all three bikes. My question above arises because I don't see any 46T-or-greater 110BCD chainring on the web sold as a "middle" ring. Some, including the 46T 110BCD Origin-8 chainring sold by RBW, are not described as being either explicitly inner, middle, or outer. I note that RBW's web-site says that its 44T chainring can be used as either a middle or an outer; it does not say that for the 46T.

With respect to a given 110BCD chainring that is sold as a middle vs outer ring for a triple crank, what about the chainring makes it that way (instead of being position-agnostic)?

In case it matters to potential respondents... the Hillbornes have 7-speed clusters in the back and the Bike Friday has an 8-speed cluster. Also, I'm uninterested in 9-speed unless I'm forced by product availability to go that way. Fortunately I have predicted the demise of less-than-9-speed drivetrains, thus making it very likely that they'll stay around. I wonder if that principle works when predicting one's own demise?

Yours,
Thomas Lynn Skean

P.S.

Just so you know I've considered it... the shifting between the 30T inner and the 44T middle chainring on the current Bike Friday setup works "well enough" for me. I've literally had zero problems, but I've done it rarely enough that it's a very limited sample size. I suspect the 30T-46T would be good enough for me also, though I do have a 32T 74BCD chainring waiting in the wings, which I presume would have a decent chance of shifting much like the 30T-44T combination. With the overall gearing on the Bike Friday, goodness knows I'd be happy enough with a 36T inner ring if they are available.

[David Banzer]

Thomas,
PM sent about 46t middle chainrings I have.
To answer your question - it depends on the chainring. Some have a chamfered edge that help with up shifts. To be in the correct orientation with the chainring bolt recesses, chainrings are marked as middle or outer. In practice you can swap middle and outer, but chainring bolts won't sit flush if you keep the chamfer edge correctly facing the inside.
David
Chicago

[dougP]

Thomas:

If you look closely at most chainrings, you'll notice a slight bevel on the inside, with the outside being flat.  This is not universal but is fairly common.  The intended position location is evident in the countersinking of the bolt holes.  An outer ring will have the mounting holes countersunk for the chainring bolts on the outer (non-beveled) face.  A middle or inner ring will have countersinking detail on the inner face. 

I have successfully used middle rings on the outside.  The bolt heads just stick up a bit but everything works fine.  One time I even (mistakenly) installed a middle backwards (bevel out), taking my cue from the countersinking rather than the bevel.  It also worked fine. 

The above is experience with plain, flat rings with no shift assist ramps'n'pins.  IMHO, if a 44T works for you in the middle, a 46T has a high probability of also working.  The nuts won't be flush with the ring but if you look at the countersinking it's quite shallow. 

dougP

[dailyrandonneur]

I worked through this question on my Bike Friday Pocket Rocket with 451mm wheels when I went to big rings. I set up a 36-48-58 set on a 110/74 crankset, in my case a Suntour XC Pro. Using the Sheldon Brown online gear calculator, this gave me a match to my standard bikes setup.

TA sells (or sold, haven't checked recently) a 36 tooth 74 bcd ring; the largest you can fit on that bolt pattern, I understand. I paired it with a Shimano SG-X outer 48t, the one one they sold on their 110/74 MTB setups in the 90s. The new outer is a Sugino flat 58 tooth ring.

Using bar end shifters, and Shimano 9-speed chain, if all shifts very well with a Campagnolo triple front derailleur. I'm using the version they sold for their 10-tooth jump 30-40-50 cranksets.

I've found these particular fronts to be really versatile, they seem to work a little better under load and over a broad range than Shimano's road front triples.

I think any good ramped outer from Shimano, better yet a TA Zephyr, will make a good middle ring. It's doing essentially the same job in the middle, picking up and dropping the chain to the smaller ring next to it. The question will be whether you are satisfied with a flat outer ring.

Good luck --
Ed Felker
Washington, DC

[Thomas Lynn Skean]

That's the sort of experience I like to hear!

I'm satisfied with no outer ring at all. So I'm covered there.

It sounds like I'll be fine with a 32T/46T setup in general, presuming I don't screw something up putting it all together and adjusting the front derailer. I really like the Sugino cranks, so I'll be happy have one on the Bike Friday. It gives me yet another bit of "common kit" between the Bike Friday and the Hillbornes, sort of a "spare part" bin. I've already set up the Bike Friday to be like the Hillbornes in several ways: B17 saddle, Bosco-like bars (narrower) with bar-ends-on-thumbies, grip king pedals, schmidt dynamo lighting, nitto F-15, NR-50, and pannier rack... things on the way include love levers, motolites, and the sugino crank. if there were a way to add a double-top-tube I'd probably do it just to finish it off!

It'll never ride exactly like the Hillbornes. I don't know how I'd fake the extra rotational inertia or narrower tires or controlled-ness (my Friday's stem riser does move about a bit). But it's already close enough to be the second most comfortable bike I've ever ridden. And, unlike the Hillbornes, I can take it on the train in rush hour, put it in my car quite easily, or travel with it on megabus. Now I'll never be without a multi-mile-capable super-comfortable bike!

Yours,

Thomas Lynn Skean

[dailyrandonneur]

If you're set on using two rings, you could also just get the Sugino XD500-d 34/48 compact double from Harris Cyclery. With 406mm wheels, you may find the couple extra teeth on each ring are acceptable.

[René Sterental]

Any photos of your Bike Friday? I'd like to see how you've transformed it. 

René 

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[Thomas Lynn Skean]

Well I'm not sure how visual any transformation centered around chai rings would be... ...but here is a "before" picture. The after will have to wait 'til after the transformation :)

http://www.guu-watanabe.com/pannierosyaree.html#thomas

Yours,
Thomas Lynn Skean

[Garth]

   FWIW , for a few dollars more than $38 you can get Dimension 110 46t rings w/o ramps/pins made from harder 7075 T-6 Al  :)