Campy SR Long cage conversion
 

I'm wanting to extend the lower gear range of a '83 Campagnolo SR equipped Raleigh Comp GS. The Chainrings are 52/42 with 14/24 gears; so I thought a longer cage may get me to maybe 30t or 32t? Maybe even lower? Or would I be better off investing in a triple crankset? Any experience with doing this?

http://bikeforums.net/attachment.php...hmentid=367471 Plus http://bikeforums.net/attachment.php...hmentid=367472

The longer cage will wrap more chain, but not affect the largest cog you can use. Most bikes will allow the SR derailleur to shift to 28t or even larger cogs. Longer cage comes handy with a wide range or triple crank.

Velognome: I used the Soma RD arms to convert a Campy NR RD to long cage to accommodate a 13-30 freewheel on my L'Eroica '13 ride and it worked well. I don't recall 100% but I don't think I was able to use the 30 tooth prior to the longer arms. I have returned the original arms to the RD and will be using a smaller freewheel if winter ever ends and we get to ride again this year.

Brad

I run a 28t freewheel with both of my SR equiped bikes with no problem. I've never tried 30t but you may want to give it a try.

I'm using the Soma pulley cage on a Super Record with 30-48 chainrings and 11-32 nine speed cassette. On my bike, the rear wheel has to be all the way back in the horizontal dropout in order to work with a 32 tooth cog, otherwise the upper pulley will touch the cog. See http://www.peterbrueggeman.com/cr/somecmax.htm

Nice, thank you!

http://www.peterbrueggeman.com/cr/somecmax-bike-big.jpg

Yeah, the cage length is more about sucking up slack from a granny on the crank. It doesn't really change the position of the top pulley for a larger rear cog.
That said, I highly encourage this kind of monkey business.
http://i291.photobucket.com/albums/l...n/IMG_0903.jpg

So you think there is enough length in the original cage to pick up the extra length required if I go from 24t to 30t ?

Ive done it on a Nuovo Record rear derailleur. I wanted to use a 28tooth cog and a triple crank with a 34 low. It worked great....Well at least as great as you would expect a campy derailleur to perform.

How long is your derailleur hanger? That was the limiting factor on a couple experiments I did with stuffing 34T cogs under supposedly short- and mid-cage RDs in my collection. Pretty much everything worked, as long as the hanger was long enough to keep the top jockey wheel from riding directly on that big cog. When things were close, the position of the axle in the dropout and the adjustment of the B-screw (when available) made the difference between working and not working. Otherwise, it was the hanger length.

Ooooh, burn! I really need to get some Campy RDs to see if they are as good/bad as their acolytes/detractors say. :)

This is the limit for me. I must not cross chain to the 52, and have very little reason to. I forgot this isn't the set up anymore as I now live in an area that doesn't require the lower gear. I have another bike to do that chore. 28t BTW.
http://farm6.staticflickr.com/5488/1...a3e17a7d_b.jpg

^ Perfect! I'll pick up a 28t freewheel and give it a try. That will give me a few more gear inches.

Originally this was a 6 cog freewheel. The IRD 7spd fit right in without modification and gave me the needed lower gear which I rarely used except to get up the hill to my former house.

Velognome, I also ran a 29T with a NR RD a few years ago. Cross chaining was an absolute no-no, but other than that, no worries.

The SR has a different cage configuration from the NR that lowers the position of the top jockey wheel and enables it to handle a larger rear cog. It should handle a 30t rear cog with no problem. The Rally-style cage lowers the jockey wheel a bit more and should handle a 32t rear cog, plus wide-range chainrings up front.

If I'm doing the math right (the circumference will change by 3" but the chain is only on half of it) it will change the amount of cage swing you need by an inch and a half.

This is the second time I've heard that the Rally cage lowers the upper wheel to handle a larger gear.

So it seems the limits to the SR would be 28T stock and 32T with the addition of the Rally cage.

What happens if you accident cross chainring? I'm in the same conundrum. 28t with a short chain clears the upper pulley, but the chain isn't long enough for big/big.

If I accidently try to make the shift, I expect a dropped chain. But I wonder if that is the worst that will happen.

I have the Soma cage on my NR and it easily handles the 28T rear but only if I adjust the chain length carefully. Too long a chain and the pulleys bounce off the largest cog. It can probably handle a 30 or 32T with some careful chain adjustments. I'm pretty sure that the top part of the Soma cage is the same configuration as a Super Record cage, which can handle a larger rear cog than a Nuovo Record cage for sure. I would guess that the SR and/or the Soma cage can handle up to a 32T with careful chain length adjustment and a long derailleur hanger. The bigger issue is how much chain wrap can the SR cage handle.

Any time I tried to shift to "big-big" it was like throwing a board between the chain, the RD and the freewheel cogs. An immediate stop to the cranks. :eek: There is lots of resistance and the RD does not want to budge. I never had the chain drop. Instead it felt as if the RD was trying to bend and flex to the point of breaking.

Right. Danger to the derailleur and hanger.
FWIW, I use a stock NR derailleur with a 28 tooth big cog. Adjusted properly, with proper chain length, it can handle it.

Unfortunately with shimano uf vertical dropouts and no B screw, the only other adjustment I can think of is wedging some material against the stop

I've heard that making that big-big shift accidentally can break something. With some derailleurs such as Simplex where the body is screwed onto the claw it can pull the body forward and loosen the screw, which means it loses all tension on the spring holding the body backwards. So FWIW I've always set my chain length so that it would manage both cross-chain possibilities. Better that than breaking the RD or bending the DO. I have indeed accidentally hit the big-big combination a few times, and it has survived.

A second question is whether the guide pulley or even the cage itself can actually clear the big cog. I've found that to be a problem on at least one derailleur, either a VGT Luxe or Vx-S IIRC.

Same here with 14-24 42-52, with Campy frame ends. Juuuuuusssssst enough tolerance to not crack the RD.

You don't need it. I'm running that RD with a 42/53 front and 13-28 rear without coming close to it's limit, and I have occasionally used it with a 14-32 ultra 6 cluster in the rear without problem on the big/big combo. It's rated to handle the 42/53 up to a 30T cog, and with careful adjustment and a sufficiently long chain, it will go to 32.