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Short Cage on a Triple - Check My Derailleur Math

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Short Cage on a Triple - Check My Derailleur Math

Old 08-20-21, 01:52 PM
  #101  
Harold74
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Originally Posted by 70sSanO View Post
Or you could swap out your 12t for a 13t and have 13/28 7 speed. Since 12 is bad and 14 is good 13 might be a good compromise. We are only talking 1t.
.

Thanks for the suggestion. I don't believe that would get the job done however. By my math, I need to shed 4T for the capacity to work out by the book, without relying on the 2T extra capacity that some folks say is built into Shimano derailleurs. My second cassette cog is 24T which barely gets that job done coming down from the 28T at the top.
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Old 08-20-21, 02:09 PM
  #102  
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Originally Posted by ShannonM View Post
The only potential snag I see is that it looks like they've got a freewheel, and individual cogs aren't always available anymore.
I do, in fact, have a freewheel on the 1992 Miyata 1000 that is the subject of this thread (primarily).

I recently bought the only two decent, NOS 7-speed cassettes that I could find on eBay for a price that I was happy with. HG-50-7. I'm pretty committed to using them so I'd not be changing gearing unless it's a simpler/cheaper thing to find alternate cogs than I've been imagining.
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Old 08-20-21, 02:13 PM
  #103  
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Originally Posted by 70sSanO View Post
46t is a great idea. You’ll get more top end than a 48/14, not lose a gear, and make your 36t more enjoyable.
I do already have an expensive new Sugino crankset in hand although I probably could find an alternate big ring for it. I like the idea but I'd probably just cave and use a long cage derailleur before executing that.
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Old 08-20-21, 02:16 PM
  #104  
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Originally Posted by ThermionicScott View Post
Blocking out cogs is a hack, and you know it.
Well... yeah, it's definitely a hack. This thread is basically about me intentionally trying to hack my derailleur situation.

Thanks for the big ring swap suggestion.
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Old 08-20-21, 07:46 PM
  #105  
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I'd say the best hack is a combination of your original hack and the smaller big ring hack.

Swap the 48 for a 46.
Size chain for the 46/28.
Don't ride in the granny on smaller cogs. Which you'd never do intentionally, because on just about every road triple I've ever seen, any cog smaller than #3 on the granny is a duplicate gear, and feels like garbage anyway. And if you land in one of those gears by accident, say by upshifting the rear when you wanted the front, you won't crash or break your bike.

Set up this way, (which is definitely a hack,) you're only exceeding chainwrap by two teeth in the gears you're actually going to use. Good gear range, good shifting, and you get to keep your short cage rear derailleur... what's not to like?

And, hell... if you're not exceeding some specs, are you really hacking?

--Shannon

PS: Detailed descriptions of your hack, both on the stand and on the road, with pictures, are required for all bike hacks.
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Old 08-21-21, 10:07 AM
  #106  
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I've just remembered something that I did decades ago to get a slightly larger rear cog to work with a derailleur. I took out the B-screw and put it in form the opposite side. I'm not sure if I used the original B-screw or if I used a front derailleur adjusting screw that was longer. What it did do as move the upper pulley of the derailleur further away from the cogs. This was before index shifting and I don't think it affect the shifting much.

Cheers
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Old 08-21-21, 11:13 AM
  #107  
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Originally Posted by Miele Man View Post
I've just remembered something that I did decades ago to get a slightly larger rear cog to work with a derailleur. I took out the B-screw and put it in form the opposite side. I'm not sure if I used the original B-screw or if I used a front derailleur adjusting screw that was longer. What it did do as move the upper pulley of the derailleur further away from the cogs. This was before index shifting and I don't think it affect the shifting much.

Cheers
OP's rear derailleur is modern enough not to have any trouble with the size of a 28T cog, he needs to work around its chain-wrap limitations.

Personally, I like to go the other direction regarding the B-screw: dial it out, and often remove it entirely for more chain wrap angle around the cogs.
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