stevegor

I have a 26" tandem which came with a 48/38/28 110 BCD set up.
I've changed the 48 to a 52, but I'm considering going to 54/42/32 for more top end speed to match a normal road bike.

My questions are these:
What FD problems would/could I face by going to the 54/42/32 or 30
What is too much of a jump from the middle ring to the granny gear?
Would 42/32 work?

And finally:
Would I get more pull on the gear cable for the FD with friction bar-end shifters than STI triple shifters?

TallRider

By 26" tandem do you mean it has mountain-bike-size wheels?
Having top-end gearing on a tandem is nice because you can go way fast with two people powering a bike that has little more drag than a single cyclist.

If you change the chainrings, I would recommend keeping the 28t small chainring, because the advantages of tandems do not extend to climbing, especially out-of-the-saddle climbing.

Your present derailer will likely be fine with the switch from 48 to 52, I'd try it and see how it does. Of course you'll need to slide it slightly up your seat tube. If it doesn't work, update to a road-triple front derailer.
I'm presently using an early-90's LX (mtb) front derailer on a 48/36/24 triple with no problems:
https://www.unc.edu/~cupery/pics/bike...ino_crank.html
I'm also using a Sora triple front derailer on a 52/42/28 (Biopace rings) triple:
https://www.unc.edu/~cupery/pics/bike...lt/MG_7003.jpg

Retro Grouch 

What are you using for a shifter?

Friction shifters or non-indexed Grip Shift shifters will compensate for a lot of minor crankset/front derailleur mis-matches.

Indexed shifters, like STIs or Rapid Fire, are a lot pickier about having everything exactly right.

Longfemur

What do you mean ?

Who says that's "normal". It's normal for an all-out racing bike, and the bikes that are marketed for those with more go fast mentality than ability. A 50 or smaller big ring makes more sense for almost everybody, and many road bikes are equipped like that, often by a savvy owner who knows better.

stevegor

My tandem is a 26" wheel hybrid type using a 3x7 gearing set up. I've removed the flat bars and installed drop bars with Shimano 3x7 STI shifters, they're got a thumb button for shifting like Campag, but I can't get enough pull on the left shifter for the clamp-on STX FD to use all 3 chainrings, that's why I'm hoping the bar ends will work, and yes, they'll be in the end off the drops.
BTW, the STX FD worked fine with all 3 chainrings with it's original grip shifters. I realize I will have to lengthen the chain as well.

As I used to road race and still train with the boys, I usually ride a 53 or 52 on my single bikes, (I still love going very fast), so considering that the 26" wheel is smaller I thought a 54t would give my stoker and I a bit more speed for down hills etc.

JohnDThompson 

You may run into problems with the 28T ring if you increase the size of the large chainring much. My tandem came with 50-45-28 rings; when I bumped up the high end to 54-48 I found I could no longer use the 28T ring because the chain would drag on the spacer pin of the front derailleur cage -- the cage just wasn't long enough to accommodate that much difference (Shimano Deore XT aka "Deer Head" FD). I had to go to a 32T small ring to get clearance.

Panthers007

Just to clarify something about hybrid bicycles - there are many things that people disagree about regarding this new breed of machine. Such as is it a racing-bike trying to be a mountain-bike? Or a mountain-bike trying to be a racing-bike? Little squabbles like this. LOL! But there is one thing that's agreed on even by the manufacturers of hybrids: They all have full-size - 700C - wheels.

stevegor

Oh well, my tandem has 26" wheels, I don't know what it would be classified as.

Interestingly, some tandem manufacturers promote a 26" wheel as superior to the 700c.

the desert fox

you need to replace the STX FD to a road type FD. the road FD needs a shorter cable pull to make the chain shift compared to an MTB FD, like your STX. in other words, the road STI brifters are not compatible with the MTB FDs. rear shifters and derailers are no problem, they have the same indexing.

stevegor

Thank you for that info, can you suggest a clamp-on road triple FD I could use?

the desert fox

if you are going to go with the 52 or 54 teeth chainring and an STI brifter, i suggest the ULTEGRA FD. most MTB FDs can only handle 48 teeth at max. there is a big difference in the FD cage profile between Road and MTB.

stevegor

Sorry if these are dumb Qs, but...
I'm currently using a 52/38/28 set up with the STX FD, the 52 and 38 work well with good clearance, but the problem is the STI brifter cannot pull enough on the cable to use a third ring, it seems the FD is long enough for it too work.

So will an Ultegra/Tiagra or Sora FD allow more side ways movement to use all 3 rings with my STI brifters?

PS: Do Ultegra triple FDs come in clamp-on?

the desert fox

1. yes, the STX FD will only work on either two large rings or two small rings. any adjustments won't be able to make it work for all three. there is not just enough cable pull or cable release from the STI brifter to actuate an MTB FD.
2. either Ultegra, 105, Tiagra, or Sora FDs will work as long as you get the triple.
3. there are clamp-on adapters available in different diameters for braze-on type Road FDs.

PS: i have done this exact same conversion.

stevegor

You don't know how much I appreciate your advice, thanks desert fox.