sd5782 

A garden variety Shimano 600 fd shifts a 26-36-42 triple just fine on my Miyata 1000. I read after my attempt at it that others have done the same. I also have a stock Suntour VXs front shifting a 28-36-46 with no problems at all fwiw. A triple sounds like the way to go with grades like that.

xanthochrome

It's done and it (basically) works! The full extremes are extremely silly, as pictured, and they did have to change out the BB and put on a new chain which obviously cost more, but I now have a 28/28 lowest gear (total gearing pictured below) and at least accidentally switching into the extremes won't destroy anything. I'll keep an eye out for a cheap long cage or mountain rear derailleur, but this will certainly tide me over seeing as I'll never actually plan to use these cross-chaining situations.

Thanks again for the advice and apologies for the dirty bike!

bikemig 

I'm impressed that the rear derailleur can handle that much chain. You pushed the envelope on the capacity of this derailleur.

Velobase has the max chain wrap at 28 teeth: https://velobase.com/ViewComponent.a...5-ba7eb763d263

The 28 running on a 28 is a nice low gear for climbing.

JohnDThompson 

"SFR" and "PR" refer to the dropout onto which the derailleur will mount, and means that the hangers on those models are positioned in a manner that will allow the derailleur to clear the 34T sprocket. It's possible other dropouts would also work, but finding out would be a matter of trial and error. If you have a wheel with a 34T sprocket available, stick it in your frame and see what happens (you may need to adjust the chain length). Otherwise, a long-cage derailleur is only a few bucks more and would likely be a simpler solution.

xanthochrome

If I did my math right, this is 38 teeth (52 + 28) - (28 + 14) = 38 of chain wrap from the big/big combo to the small/small combo. Between that and the FD managing to shift the triple, it seems like I got pretty lucky!

sd5782 

That looks scary to me, especially when a long cage is the proper tool for the job.

genejockey 

Wow. The extremes are.... extreme. I'd find a GS cage RD as soon as humanly possible. I don't trust myself not to misremember where I am on the cassette and go full Biggie Bigs or Smallie Smalls.

jdawginsc 

Send your address via PM if you want this.

bikemig 

You did get lucky but you will want to seriously consider replacing the RD with a long case. This is not likely to be a good long-term solution.

xanthochrome

For those worried about my extreme extremes, I'm getting this RD! Thanks again for all of the help and advice on this forum

bikemig 

We were a little in awe that you got that combination to work as well as a little concerned.

kommisar

With a triple you really want a long cage derailleur. I suggest a shimano rd-m310. It has a take up of 43 and max cog of 34T and can be had for less than $20 new on ebay.

Charles Wahl

I'd prefer a Shimano M739, for a classic bike like that one. Or the long-cage Cyclone, even more classic.

Piervinc

I’m pretty surprised this works. I probably would have gone for a longer cage derailleur. But, really, you’re rarely (never) going to be fully cross-geared, so what you’ve done ought to be ok! Nice!

kommisar

Good choices too. The m739 sgs has max take up of 38 and max cog of 32T. The gt cyclone mk1 has max take up of 36 and max cog of 32 or 34T depending on length of the hanger. The gt cyclone mk2 has a max take up of 34 and max cog of 34T

xanthochrome

Thank you all again for all of the advice and especially to jdawginsc for the long-cage RD-Z505 derailleur that I just finished installing (myself!) today. Hopefully these two photos cause less anxiety

My new gearing is a 52-38-28 triple up front and a 14-28 in the back. I'm not looking forward to the big hill, but it does seem much less daunting with a 1:1 gear ratio than it did with a 39 up front and a 28 in the back!

jdawginsc 

Whoop whoop!