Bicycle Mechanics - AN "ALMOST" GREAT IDEA

With more time on my hands, than good sense in my head.

I decided that I would be happier with my Ultegra triple crank if I switched the chainrings from the factory 52-42-30 to a better fatboy 53-39-30, using an Ultegra double crank that I had.

I guess what? the 42 is no where near identical to the 39! The 39 is a flat ring, just like I have seen a thousand times. The 42 from the triple has pins, ramps, bumps and lumps all over it. I assume to help with the dreaded middle to low ring shifts.

I know that I could have made the change and it would work, but I have enough trouble keeping the mid-lo shift workings as it is.

You would need to find a 39 that is designed to be a middle ring. SInce the one from your double was designed to be the small ring, it has no need to ramped and pinned. It would work, but not as smoothly.

Specialities TA make good rings with all the pins and stuff.

Na, I ain't going to put any money into this...just thought that it was interesting that there was such a difference.

It will work fine - just not as smooth as possible. It's how gears were shifted before ramps and pins were invented - only a short while ago. Certainly worth the effort.

55/Rad

Na, I ain't going to put any money into this...just thought that it was interesting that there was such a difference.

Another problem that might arise is that the Ultegra front dérailleur probably won't have enough lift to bring the chain from a 39t middle ring to the 53 outer ring.

Another problem that might arise is that the Ultegra front dérailleur probably won't have enough lift to bring the chain from a 39t middle ring to the 53 outer ring.
My Ultegra double doesn't have a problem getting from 39 to 53, even without pins and ramps - why would a triple have that problem?

55/Rad

My Ultegra double doesn't have a problem getting from 39 to 53, even without pins and ramps - why would a triple have that problem?

55/Rad
The Ultegra double front dérailleur is designed to lift the chain from 39 inner to 53 outer, a 14t jump. The triple front dérailleur is different and designed to lift the chain from 30t to 42t to 52t chainrings. If you look at the inner plates of both the double and triple dérailleurs, you will see the triple has two lifting surfaces on the inner plate, one for the 30~42 jump and one for the 42~52, a 10t jump, the double has a single surface. A double dérailleur can be made to work with a triple crankset, though not always well. The triple dérailleur has a very hard time lifting the 14t difference (39~53).

1oldRoadie,

You're not alone. A 39 small/mid chainring suits my style and rear cogs to a tee. So when I swapped back to a triple, I wanted to retain my normal 39-52 setup and simply add a 30T bailout gear. I had most of the parts on hand so it seemed simple. I use an older DeoreLX FD. Getting this to shift with STI seemed to take forever so I started looking. I think Davet may have a point here. Check out Peter White at
http://www.peterwhitecycles.com/chainrings.asp. I haven't tried the DA as its not exactly a budget-conscious, commuter bike solution. If anyone has experience with various FDs on a 53-39-30 or even 52-38-28 chainring setup, I'd like to hear, good or bad.