Originally Posted by
stevegor
Hi
I'm restoring a Reynolds 531 steel frame bike with a Dura Ace crank set using a 53/38 rings and DT shifters.
1: Is the jump too much between the 53 & 38?
2: I measured my 116 link chain by the Park Tool method: Large chainring to Large rear cog, then 1 link and it seems too slack on the 38 in the smaller cogs, what am I doing wrong?
3: The RD seems to pull forward too much, why?
The issue is Chain Wrap and the capacity of the RD may not be great enough. See:
http://www.sheldonbrown.com/gloss_ca-g.html#capacity
"
For rear derailers, the capacity relates to the amount of chain slack the derailer can take up, and is equal to the front range (15 in the example above) plus the rear range. Thus, if you have a 53/38 crank set, and a 12-28 (16 tooth difference) cluster, the total capacity required would theoretically be 31 teeth (15 front difference + 16 rear difference).
Manufacturers specify this fairly conservatively. They must do so, because they have to assume that some of their derailers will be sold to incompetent cyclists, who will abuse their drive trains by using the smallest chainwheel with the smaller rear sprockets.
Competent riders can considerably exceed the official rated capacity, since they will not misuse the granny ring by running it with the smaller rear sprockets, so it doesn't matter if the chain hangs slack in those gears".
What size cassette (or freewheel) is installed? What make & model RD are you using?
You could solve the problem with a new set of chainrings, or not. Knowing the chain wrap of the RD and the cassette range is needed to answer the question.