smurf hunter

I've got a Shimano 105 FC-5603 crankset with the stock rings on it (50/39/30). I prefer running a relative straight block for my rear 10 speed cassette, but I live in a hilly area and once in a while require some low gearing to get my fat butt over a mountain pass, or just a 20% hill in downtown Seattle.

On paper it would appear I can change out my 30t granny ring for a 26t without any FD trouble. Even if the shifting from middle to inner isn't the smoothest, I can deal with it.

I rarely use the granny, but when I do it seems I really need it.

1) Can I use a run of the mill retro MTB 74BCD inner ring?
2) Can I go even smaller (24T) and still have it cooperate w/ my FD?
3) I am inclined to be frugal and go through the recycled parts bin for a suitable ring - unless someone can convince me of a technical reason not to

Thanks

DMF 

There's nothing special about granny rings. They should interchange okay.

You will be adding more slack that needs to be taken up by the RD, but you should already have a long-cage RD. Check the overall slack against the RD spec just to be sure.

zzyzx_xyzzy

Should work fine. One trick for un-sanctioned chainring combinations: If you install it and it doesn't shift well try rotating the small chainring by one bolt and try again. 39/26 simplifies to 3/2 so if you get the chainring timing right it can shift very well.

I run a 24-39, with aforementioned playing with the chainring alignment it shifts quite well.

I was just in recycled cycles, they have like a dozen new takeoff 74x26t granny rings there.

smurf hunter

Thanks.

I love recycled cycles. I've scored a couple 10 speed ultegra cassettes from there - each under $10.

In fairness, they were filthy and no where did it say "Ultegra", but I noticed "cs-6600" and tried to not be obviously excited.

Chris_W

Putting a 26 tooth should work fine, a 24 tooth is pushing it a bit, but can also be done. Neither should necessitate changing anything, just stay away from the small-small gear combinations, where there might not be much tension in the chain and/or the chain may rub on the middle chainring.

Put a Dog Fang, or something similar, chain retention device on to make sure that the chain doesn't derail off of the inside when shifting into the granny ring (which is much more likely due to the large gap between chainring sizes).

If it is a Shimano crankset, then you'll notice that your current 30-tooth chainring is spaced a little bit in from the mounting points due to the shape of the ring. To get the new ring, which will probably be completely flat, to sit in the same lateral plane as the old one, put some thin washers between the ring and each of the mounting points.

I've done this switch so many times to mine and friends bikes that I have a whole stack of barely used 30-tooth rings hanging around. If anyone needs one, then I can post one to anywhere in Europe for very little cash.

HillRider

Me too. I have a collection of never-used Shimano and even one Campy 30T 74 bcd rings hanging on my garage wall. Same offer for the US. If anyone wants one, PM me.

Metaluna

Another 30T collector here. Right now running a 28T T.A. Specialites on a Tiagra 50-39-30 crank, and it shifts great. Before that I had that same granny ring on a Record 50-40-30. I have a 26T from a retired Sugino crank sitting around somewhere, so maybe I'll give that a try one of these days.