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Shimano 600/SC: Increase cog capacity?

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Shimano 600/SC: Increase cog capacity?

Old 04-22-11, 09:13 AM
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Shimano 600/SC: Increase cog capacity?

Hello peoples of Earth.....

I have a short cage (and I do mean short....not medium) Shimano 600 RD I just acquired. I decided not use it on my ride, but rather put it on a bike I intend to build for my sister. So, in deciding how I'm gonna the gear the sucker to suit her abilities, I figure I probably need to go with a top cog of atleast 30t. Probably she could get away with a 28t, but 30t might be better.

On the front, I intend to build a double on a triple crankset with a small ring of 28 and large of 42 or 30 and 45.....Using a worn even larger ring (w/teeth ground off) as a guard. Anyway, I read up and found a lot of info regarding the short cage capacities........someone saying no more than 14/15 tooth difference on the crank and no more than a 28 (or maybe even 29) for a top cog.

Well, I understand about chainwrap and cog capacity and what determines those parameters, but I'd also read a while back that a med. cage (eg. Suntour GT) could handle up to 32t cog or even 34t IF the hanger was of the long'sih variety. Sooooo......<<<dum-da-dum-dum>>> I'm thinking maybe I could push this SC 600 capacity to 30 with a long hanger. The hanger would be the bolt on/claw type, but off a Shimano Tourney RD......and that sucker is pretty freakin' long! (comparatively speaking).

The question is: even though I really think this would work, has anyone ever done this and experienced the contrary??

I'm sure the proper thing to do would be just to throw a long cage on the back, but hey.....I gotta do something with this 600 or it's probably gonna just wind up in a box.........knowing me, of course.

Thanks!
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Old 04-22-11, 09:42 AM
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This all seems like a lot of effort for what could be acomplised with off the shelf parts.

For the RD, that will probabaly struggle with a 30t; why not stick it on ebay instead of a box?

Why use a triple crank for a double, when you can get doubles?, and the chain ring sizes you have suggest are small, more like MTB than any other bike; also the cost of even cheap chain rings will soon add up to the same as a new crank.

The idea of grinding off teeth of a chainring rather than getting a purpose designed one, will end in tears, cut shins and a lot of blood, you can get proper guards for this.
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Old 04-22-11, 01:38 PM
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Thanks for the opinions. I'm just asking if someone has tried it or knows for sure it would work. I can certainly always just try it myself and see if the chain loads up on the freewheel correctly. But, doesn't hurt to ask, either.

A lot of effort equates to not much more than attaching everything I already have to work with. It'd be more effort for me to acquire off the shelf parts. You know......I'd have to trade out, sell, and/or buy to get something else.

The frame requires a bolt on hanger, anyway. So, no real extra effort on that.

As for using a double crank, this limits how small of a chainring I can use. I'm sure you know this, though. To go any lower than 34t ring (on any 110bcd spider) I'd have to get another crankset with a different BCD......which means, again, more money or bartering. Either requiring more effort than my intended plan. Also, I know a couple of people that have used a modified chainring as guard with no injury. And, I've not heard of prob's on web searches. So, I'm not sure where you get that idea.

But, if you really think the RD will struggle with that size of cog, I can always just use a 28t top and work the crank gears a bit to suit. I have a bunch of spare rings, so the expense is already covered.
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Old 04-22-11, 01:55 PM
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I would think that a 30 in the front and 28 in back should be low enough, even for Winslow Arkansas, been there many times. I think 42-30 in the front and 12-28 or 14-28 in the back might make a good combination.
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Old 04-22-11, 02:01 PM
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Since the frame doesn't have a derailer hanger and you must use an adapter claw, I think it is possible for this to work if you get the right claw. Right now I'm running a 30T with my short cage 600 derailer. I've tried a 32T and it will run, but not very smoothly.

My chain wrap is 29 (52/42 with an 11-30 cassette) and I will tell you that's pretty much the max. With the proper length chain in the big/big combination my RD is completely slack in the small/small combo, where the upper pulley is almost touching the lower line of chain. I never use either of these combos so it's not an issue. But you're proposing a capacity of up to 36 teeth (45/28 assuming an 11-30 cassette.) The RD will almost certainly rub the chain in the small/small combo with the correct length chain so make sure your sister knows this and does not attempt to use those gears.

In general I agree with jimc101, this sounds like a lot of work. But if you really want to, it can probably be done.
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Old 04-22-11, 07:08 PM
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Originally Posted by Al1943
I would think that a 30 in the front and 28 in back should be low enough, even for Winslow Arkansas, been there many times. I think 42-30 in the front and 12-28 or 14-28 in the back might make a good combination.
Well, if it were me or you riding it, I'd agree....hehe. Besides, my sister lives in Memphis and she's way, way, way outta shape. If you're familiar with Winslow, you've probably been to Devil's Den. Last time she came up and we went, it was VERY difficult for her. She couldn't even make it to the first cave, dude.
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Old 04-22-11, 07:48 PM
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Originally Posted by FastJake
Since the frame doesn't have a derailer hanger and you must use an adapter claw, I think it is possible for this to work if you get the right claw. Right now I'm running a 30T with my short cage 600 derailer. I've tried a 32T and it will run, but not very smoothly.

My chain wrap is 29 (52/42 with an 11-30 cassette) and I will tell you that's pretty much the max. With the proper length chain in the big/big combination my RD is completely slack in the small/small combo, where the upper pulley is almost touching the lower line of chain. I never use either of these combos so it's not an issue. But you're proposing a capacity of up to 36 teeth (45/28 assuming an 11-30 cassette.) The RD will almost certainly rub the chain in the small/small combo with the correct length chain so make sure your sister knows this and does not attempt to use those gears.

In general I agree with jimc101, this sounds like a lot of work. But if you really want to, it can probably be done.
Guys, believe me.....I'm happy to be getting input from you all. But, what part about this seems like a lot of work? I don't get it. It's not any different than setting up any kind of conventional combination. I'm installing all the normal components any bike would have. Only difference, I'm putting on the chainring w/ the teeth ground down (which is no different or anymore dangerous than running a mtn/rd triple) and putting a longer derailleur hanger than normal to try and make use of this derailleur.

You guys should see this hanger. It's atleast nearly 1/2" longer than most adapter claw or braze on hanger I've seen! And, it's some cheap mtn bike thing....I wanna say Huffy, but don't remember offhand. Something along those lines, though.

Anyway, the most I'm gonna gear it up to will be about 80-85 gear inches and the low to be around 30.... at least. Knowing her, she'd be comfortable in this range and find all the gears usable. Down the road when she's lost weight and gotten stronger, then she can go somewhere and have done whatever she wants, you know? She's lives in Memphis and there's a great bike shop (went there all the time going to college....The Peddler) in midtown. I'm doing this in return for a big favor she's done for me. All the parts save the derailleurs, any cables/housing, the tires ($3/pc @ nashbar long time ago), and a nice saddle, were/are free. I mean, no money was spent. Just a barter.

Anyway, sorry 'bout that ramble.......just tryin' to explain so you guys have some framework.

The freewheel I was considering using is a barely used, Maillard 6spd-14/30. I've run it before to test it and works/shifts pretty darn good for what it is. On the other hand, if using the long cage and the 600 wasn't/isn't gonna work out, I have a back up 7spd Suntour 13-28. In either case, she is a REAL smart girl. If said,"Hey sis......you can't make these shifts", she'd follow "why" as much as she could, but she'd certainly remember not to do it. She remembers things from when we'z little people that I don't even remember. Embarrassing things.......<<<<shut up!>>>

In ANY case, I do intend to build it and ride it several, several times to make sure everything's kosher on it. I'll make whatever adjustments necessary after that. The fact that you (Jake) are running what you are is encouraging. I'll keep that chainwrap count down however that needs to happen. But, a 1:1 ratio on the low end is what I'd like to shoot for. So, I think I'll go ahead and give it shot, then.

42/30 to 14-30 = 28 on the chainwrap. Going by your inputses, we'll see if it works!
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Old 04-22-11, 09:13 PM
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Originally Posted by Al1943
I would think that a 30 in the front and 28 in back should be low enough, even for Winslow Arkansas, been there many times. I think 42-30 in the front and 12-28 or 14-28 in the back might make a good combination.
Crap......I think you're right, man. I just punched in the numbers on Sheldon's chart. Not much difference in gear inches between a 30t ring/30t cog and 30t ring/28t cog. What....just a couple of gear inches? Hmpfth......

I think I just wasted your time, fellas. I'm terribly sorry 'bout that. Appreciate the input....really.
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