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54x39...Possible?????(5 posts)

54x39...Possible?????The Flash
May 6, 2002 10:40 AM
I'm currently running a 53x39 chainring set and would like to use my Dura Ace 54 on my tri bike without using a 42 small ring. Is this possible/advisable? I'd like to keep the 39 because it's lighter and gives me a wider range of options with my gearing. BTW, I run either a 12/25 or 13/26 on the rear.

Thanks all!
Scott
According to Shimano, yes it is possible...Cima Coppi
May 6, 2002 11:07 AM
Check out the stats page on Shimano's website for the D/A front derailleur:

http://bike.shimano.com/road/dura-ace/ComponentTemplate.asp?partnumber=FD-7700

The capacity is 15 teeth, so with your 39t inner ring you would be at the maximum capacity. According to the webpage, you can go as high as a 56t outer ring, but you would need to up the inner ring as well.

Good luck,

CC
worksDougSloan
May 6, 2002 1:10 PM
I've used up to a 56/39; you have to be a bit more patient in the upshifts, but it will work. The shifts can be slower. Also, it may limit use of the small ring and the smaller cogs, as the bigger the difference between the front rings, the more likely the chain will hit the larger ring when on the small ring as the chainline moves outward.

You won't really gain much from it, though.

Doug
worksThe Flash
May 7, 2002 5:50 AM
Doug...

The only advantage I see of going to this chain ring is that it is much more rigid than a standard chainring. Seeing that I'm a clydesdale, I'm looking for something to reduce chainrub when I'm mashing it out. Do you think it's worth going to for that reason, and will I see a difference in gearing ratios?

Thanx!
Scott
worksDougSloan
May 7, 2002 6:08 AM
I have the 54 Shimano, too (that's the one you are talking about?). Compared to a 53, it's less than a 2% difference, whereas a 1 tooth difference between an 11 and a 12 cog is about 9%. I'm using a 12-21 in the back on the time trial bike.

I can't really tell if it's stiffer. I'm not that powerful. I think it's slightly more aero, though. Only the outside of the ring is solid aluminum -- it's only a very thin skin; the backside is milled out like a normal chainring.

Hey, can't hurt.