Surferbruce
03-17-05, 07:55 PM
what's the smallest size i can go for a big ring on a standard ultegra crankset. i mostly see 50's, can i get a 48 or 46?
Bicycle Mechanics - smallest large ring?
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Michel Gagnon
03-17-05, 08:09 PM
Almost as small as you can get.
The Ultegra triple crankset uses 130/74 mm 5-arm bolt circles. The 74-mm bolt circle exists only on triples and is for the granny.
On the 74-mm circle, you can go as low as 24 teeth.
On the 130-mm circle, you can go as low as 38 teeth.
Shimano road derailleurs (triples and wide range doubles, AFAIK) are optimised for a 10-14 tooth spread between both largest rings, so you could have 24 (or whatever), 38-48.
You could go lower, I think, with a close range double or an old derailleur that prefers 3-4 teeth differencial.
BTW, I'm not sure that Shimano road rings go below 48, but TA makes almost any size you want.
The Ultegra triple crankset uses 130/74 mm 5-arm bolt circles. The 74-mm bolt circle exists only on triples and is for the granny.
On the 74-mm circle, you can go as low as 24 teeth.
On the 130-mm circle, you can go as low as 38 teeth.
Shimano road derailleurs (triples and wide range doubles, AFAIK) are optimised for a 10-14 tooth spread between both largest rings, so you could have 24 (or whatever), 38-48.
You could go lower, I think, with a close range double or an old derailleur that prefers 3-4 teeth differencial.
BTW, I'm not sure that Shimano road rings go below 48, but TA makes almost any size you want.
Surferbruce
03-17-05, 08:29 PM
awesome -thanks!
John E
03-17-05, 09:28 PM
I am happily running 48-45-34 with an old Sugino mountain crankset (110mm BCD) and an older Shimano 600 front derailleur. Half-step gearing is NOT dead! I have 8-tooth outer drops, such as 50-42, 48-40, and 46-38, on various other bikes with a variety of older and newer front derailleurs. (An 8-tooth drop in front tends to give a great 1.5-step ratio progression with 2-tooth steps in back.)
darkmother
03-18-05, 07:04 AM
I am happily running 48-45-34 with an old Sugino mountain crankset (110mm BCD) and an older Shimano 600 front derailleur. Half-step gearing is NOT dead! I have 8-tooth outer drops, such as 50-42, 48-40, and 46-38, on various other bikes with a variety of older and newer front derailleurs. (An 8-tooth drop in front tends to give a great 1.5-step ratio progression with 2-tooth steps in back.)
Interesting. Where did you find the 34 tooth granny?
Interesting. Where did you find the 34 tooth granny?
sydney
03-18-05, 07:17 AM
Interesting. Where did you find the 34 tooth granny?About any place that sells 110 BCD chainrings.
John E
03-18-05, 01:42 PM
About any place that sells 110 BCD chainrings.
Actually, my grannie has a 74mm BCD, for the inside position of a conventional 110/74 triple, but Sydney is correct, in the sense that one could just as well use a 110 BCD 34T grannie in a triple setup by holding all three rings with a single set of long stack bolts and spacers. (I still have two sets left over from my years of riding a "1/3-step" 49-46-43 / 13-16-19-23-26 setup. Check out the 14-speed ratio progression on that combination; it's incredibly smooth!)
To answer the original question, I found my 74mm BCD 34-toother on eBay. I'll be Harris Cyclery has them, as well.
Actually, my grannie has a 74mm BCD, for the inside position of a conventional 110/74 triple, but Sydney is correct, in the sense that one could just as well use a 110 BCD 34T grannie in a triple setup by holding all three rings with a single set of long stack bolts and spacers. (I still have two sets left over from my years of riding a "1/3-step" 49-46-43 / 13-16-19-23-26 setup. Check out the 14-speed ratio progression on that combination; it's incredibly smooth!)
To answer the original question, I found my 74mm BCD 34-toother on eBay. I'll be Harris Cyclery has them, as well.