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Ultegra double Question
I did a search and didn't find what I'm looking for, I have an ultegra ten speed double, had thought about a compact crank but was wondering if I could just get a smaller chainring to replaced the 39 tooth ring? if so should i expect shifting problems by going to a 53 34 setup? wondered if it was possible or if anyone has done it with sucess?
Take a good look at where the bolt holes are on your 39 tooth chainring. You'll realize that putting a smaller diameter 34 tooth ring on your crank just isn't possible.
38 is about as low as they make them for a 130 BDC, and I have a site that made a 37 but the bolts were placed high into the teeth. If you want to do something like a 53 / 34 you need to look at a compact crank with a compact front dr to make the shift difference. Go look at the Road thread....they have lots of compact crank advice.
Shimano now has an Ultegra level compact crank (50x34) that uses the same bottom bracket as the normal double and will work with the standard double front derailleur.
As noted, 38T is the smallest commonly available ring that will fit the 130 mm bolt circle on your crank and the change from 39 to 38 is insignificant.