105 rear cog limits.
 

I recently purchased a like new 2005 Sirrus Comp , with a Shimano 105 rear derailleur, with a 50-34 front, and a 9 spd 12-26 rear. Id like to have a lower gear for tough hills. I know what Shimano says are the limits, but what is the largest cog I can really fit on the rear, in the real world? This is the only change I am considering, other than 32-35mm tires, when these 28s wear out.

I can make do with what it came with, but its tough on an old damaged knee at times. Other than this one thing, I love this bike, and its a nice alternative to my Crosstrail when my back allows it.

I use a 30T .

You realize bigger tires will result in slightly higher gearing + more weight to get up the hills?

If you wanted to install a newer mountain RDER, you could go as big as 36T.

Per spec, 27T is the largest cog a 5500 (9-speed 105) RD will take: https://www.bike-components.de/bedie.../rd-5500.2.pdf

Since Shimano is conservative in their ratings, I would imagine it could take at least a 28T, but it'll depend on the bike. If I were in your shoes, I'd be considering a triple. ;)

Foldable Marathon Supremes weigh next to nothing, and the added weight wont dent my 200+..... and I will stick with this DR and switch to the largest cog which will work while everything is still brand new

A 32F and a 35R will soften the ride a bit more than the 28s that are on there now.

Hopefully someone who has made a switch to a 30 - 32 cassette will chime in.

The actual largest cog that will work also depends on the configuration of your frames derailleur hanger. A longer hanger will clear a larger cog. As a general rule and based on numerous reports: For 9 and earlier 10-speed Shimano road rear derailleurs with an "official" 27T limit a 28T will always work, a 30T will usually work, a 32T will sometimes work and a 34T will almost never work. As a last resort you can either reverse the B-screw or substitute a longer one to get more capacity.

If you ever change to a bigger tire be sure to check the frame and fork clearances, you can't always count on bigger tire sizes fitting the frame or the fork.

I ran a 12-30 Tiagra without problems.

New 105 RDs aren't that expensive and they can handle a 32 tooth. They're $44 at Nashbar and today you get 15% off plus free shipping.

Thanks for the suggestions, appreciated all!

You're going to use 2 different sized tires?

Yes, on the sizes. I have found that the slightly smaller front improves quickness and handling, without sacrificing ride. While the larger rear improves ride and capacity, without sacrificing handling. I love mixing tires for their attributes.

A 30t cog will work.
Make sure you have clearance for the wider tires.

Front will accommodate almost anything. Rear will be limited to a 35, with just enuf room to add fenders if needed........... A 40 might fit, as long as the wheel remained perfectly true................ total width on the rear frame is "almost" 45.

The RD5501, short cage, will not quite wrap enough chain. The 50-34 compact, and the 11-30 cassette work fine other than that problem. In the little ring, and the 11-12 rear, the chain wraps tight enough to not be floppy, but the chain rubs the tab of the short cage itself. I think a long cage would work fine. If I stay out of the 34, and 11-12 combo, no issues.

It shifts perfectly, up or down, but I don't like the rub. Yes, the B screw is all the way in to accommodate the 30T.

Too bad I can't buy the long cage itself from Shimano, and convert my short cage 105 to a long cage.....

Since I can't find a long cage 5501, or any 9spd long cage road derailleur, looks like a Shimano SLX M662 Shadow 9 Speed, will be in my shopping cart soon.

There are plenty of used 5503 long cage 105 derailleurs around. Have you tried Evilbay?

I got one from a CraigsList Seller about two weeks ago for $15.

I will look again, but found none earlier. Heck, I'd even take a broken one, as long as the long cage was OK.

Maybe the problem is the way you are searching. RD-5501 is a short cage derailleur. You are not going to find a long cage 105 derailleur that way. Try searching "Shimano rear derailleur GS". GS is Shimano's designation for a medium/long cage.

You can't easily change a derailleur's cage length because one of the cage plates is only sold with the derailleur body

I found a NOS 105 9 spd, 5501 Long Cage,,,,,,, and it's in the mail....... I'm happy!

The bad news is that it is supposed to be in the 20s for a high, and snowing, when it gets delivered...................

Putting on a long cage RD would be a lot easier and cheaper than a triple.

A triple requires a new FD shift lever which is mucho $$$.

I found a NOS 105, 5501GS (long cage) rear derailleur, and it works perfectly. Plenty of wrap, and shifts all nine. Looks like it might wrap enuf for a 32.

I only got a very short ride, before the snow, but it sure gave me what I want with a higher (11T) gear, and a lower gear (30T) for my compact (34-50) double. The 11,12,14,16,18,20,23,26,30 rear cassette is a really nice spread, with lots of overlap for gear choice. Now, I can go downhill faster, and that 30T on the back is a HUGE difference compared to the 26T stock cassette. And, I think the Shimano cassette shifts smoother than the SRAM. Now, if I just had the dork disc.....................

Just wanted to let you know of the final resolution.