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105 RD range(5 posts)

105 RD rangekilimanjaro
Sep 9, 2002 8:11 PM
I have an old 105 RD (part of late 80s/early 90s biopace group). I want to increase my largest rear cog and can't find info on what is the largest cog the RD will accept.

Juding by the size of the rear cage I would guess that it is a medium cage at minimu. The rear cluster that came with the bike is 14-24 and I found 28t cogs on I would like to know if will work with the RD (I want to climb a few hills towing my kids). According to the sheldon brown website the current 105 doubles RD will accept up to 27T cog with a chain wrap of 29 (I will have chain wrap of 28 with the 28t cog so this chain wrap should not be a problem).

I am not afraid to look up the info myself if I only knew where to search.

Thanks for your help in advance.

re: 105 RD rangeRusty Coggs
Sep 10, 2002 4:35 AM
I have used the old 105s with a 30 tooth large rear cog and they may handle more.Shimano spec was at least 28,which is typically conservative.
I don't know for sure, but I'd sure try it.Spoke Wrench
Sep 10, 2002 5:41 AM
Back in the olden days long arm rear derailleurs routinely would handle a 34 tooth rear cog. I even had a Sun Tour AG Tech rear derailleur that would handle a 38 tooth rear cog! We didn't have separate road and mountain component groups back then. Your derailleur sounds to me like it came from the end of that era.
I had one of those 38 tooth rear cogs for loadedscottfree
Sep 10, 2002 9:03 AM
touring in the mountains! Sigh. Size of my current inner chainwheel!
So that's two.Spoke Wrench
Sep 10, 2002 1:00 PM
How many do you think they sold in total? Mine was on my original Schwinn Twinn tandem. I don't want to talk about the rest of the bike because I take ridicule badly.