I have a Specialized Tarmac 20 speed with an Ultegra Standard crank, Ultegra FD, and an 11-26 cassette with Dura Ace RD. I am a flatlander, but have some mountain ride vacations coming up. With my 52 year old bad knees, I don't want to push big gears up mountains. I'd like to have a minimum of 34T front and 34T rear gearing. If I could go smaller on the front, I'd like to. I looked at my standard crank and I don't think I can go smaller than the 39T small ring. That leaves a compact as my only option I assume. I want to keep my shifters. I guess that leaves Shimano as my only crank option. Can I put smaller chain rings on a Shimano compact crank, say 48-32? If I drop to a compact, will my FD work well with it? If I go to an 11-34 cassette, I will have to switch out the Dura Ace RD for what? The bottom bracket on the bike is an FC6601.



Any other things I need to consider?

Your current Ultegra crank has a 130 mm bolt circle diameter and can accept a 38T chainring as a minimum and 39T rings are far more common. Most road compact cranks use a 110 mm bolt circle diameter and a 33T chainring is the smallest that will fit and, again, 34T is by far more common. So, no, a 32T chainring won't fit. Your front derailleur will work with a compact double if you lower it to obtain the proper clearance over the smaller outer chainring.

Road triple cranks are usually geared 50/39/30 or 52/39/30 so they are a possibility. The Tiagra 4603 crank is 50/39/30 and will work with your bottom bracket but perhaps not with your shifters unless your front shifter is triple compatible.

You will need a 9-speed MTB rear derailleur to clear a 34T rear cog and it will work fine with your 10-speed shifters. Note that the newest 10-speed MTB rear derailleurs won't work as they use a different cable pull.

Thanks for the reply. Simple and to the point. Just my style. How would I know if my current brifter is triple compatible? I'd love to go with a 105 road triple, but don't want to have to buy new brifters. They are EXPENSIVE!

Are your shifters 10-speed Ultegra? The model number will be ST-6703 if they are triple compatible and ST-6700 if double only.

There are compact doubles out there that go smaller than 34 tooth small rings. For example, this crankset from Velo Orange is 46 - 30. Whether that would work with your current shifters and derailleurs IDK, but it is out there.
Review: Velo-Orange Grand Cru Cranks @ The Path Less Pedaled
Running the gear ratios through a gear inch calculator, it looks pretty reasonable for someone with bad knees looking for a mountain friendly crankset. The 46 tooth big ring should be fine for riding on the flats or in the valleys, while the 30 tooth small ring mated with a mountain cassette will get you all the way down to 23 gear inches for the really steep climbs.

If you really want to go extreme, Sugino makes a 44 - 30 compact crankset, with options to go even lower on the small chainring.Sugino OX601D Crankset (part 1) - Bike Hugger

Yes, they are Ultegra 10 speed. Where would I find the model number?

That could well be my solution if they are compatible with my brifters (they should be) and my BB. I am going to dig into that a little bit.

Here are two reviews of the Sugino crankset.
Boston By Bike: Low gearing on a road bike - Part 3/3: "Sugino OX601D - The Freedom Crankset"
https://epicureancyclist.com/review-s...rankset-44-26/

From the second review.

"The Sugino OX601D Compact Plus‘s best feature is freedom (cue music). Freedom from the tyranny of road racing conventions that muck up cranksets for the rest of us. In all seriousness, it is wonderful to see a crankset that really gives you carte blanche with your chainring choices. It really allows you to fine tune your bike to your style of riding….and they are also compatible with modern STI shifters. You can set up a standard wide range double of 44-30, or even do something crazy like a 44-26! The only real downside is the cost. They are admittedly a bit spendy. However, if you are tired of waiting for Shimano and SRAM to make a crankset for your style of riding (instead of trying to fit into theirs), then the Compact Plus is just the ticket."

Here is another possibility from IRD. A friend of mine recently installed this on his vintage road bike. I don't believe he has ridden it yet, but we are hopeful that replacing his standard double with this compact will give him a much more useful gear range for the style of riding he does now compared to 30 years ago.
IRD Defiant Wide Compact Road Double Crank Set (46-30t)

The Velo Orange crank uses a oddball 50.4 BCD granny and the Suguino is basically a 110/74 BCD triple crank with the outer chainring removed. I suppose you could convert a Shimano 105 FC-5703 crank to the same wide range double by moving the big chainring to the inner position, removing the 39T chainring and using a short bolt set.

The 50.4mm bolt circle mounts the outer ring, not the inner (the inner ring mounts to the back of the outer ring, using six bolts and spacers), and while not common now, was once a widespread standard. Stronglight, TA, Shimano, Williams, Lambert, Nervar, Zeus, Sugino, and probably others all made cranks using the 50.4mm bolt circle. Rings for these are still available, with a little effort.

Another option that I've done twice now --is to acquire a Shimano 6503 vintage (or 105 equivalent) triple crank and simply use the inner two cranks. Both of my conversions removed the 52 (replaced with a CF chainguard) leaving 42-30 and I replaced the the 30 with a 26. The other is now a 44-28. With a rear cassette up to 28 or 32, I have reasonably low gearing for hills and still can cruise easily at ~20mph (on the 44-11) if I have to.

Let me ask this. Would one of the new readily available mountain double cranksets work? They are running some good ring combinations for my style. If I do that should I get a new mountain FD as well so that the FD plate profile matches better with the smaller rings?

An MTB crank will work but you will have to retain your road front derailleur. MTB front derailleurs require a different cable pull from road fd's so your road shifters won't work with it. Actually, if set at the proper height, road fd's work remarkably well with "too small" chainrings.

Good stuff folks. Thank you all very much for giving me some good ideas to kick around.

If you have a braze on style FD mount, the FD will only go so low. Most mfgs try to cover 50-54.

It's a clamp on!

OP, Are you allergic to walking? These low ranges were designed for touring cyclists whose loaded bikes can weigh 50 lbs or more. You wouldn't want to push something that heavy up a hill but you wouldn't care that much about pushing a CF road bike. Some of these super low gear options would allow for below walking speed progress. In other words, you might as well walk. Taking gears that are too low is as crazy as taking gears that are too high.

I don't know you but I know the age. I think a road strategy offers benefits not available when using touring or mtb specific components.

A) With a road triple (30/39/52) you can minimize the differences between the new gearing and the old. It's going to take a while to get used to where your "old" gearing combinations have moved to. This adjustment period can be frustrating because the new gearing is unfamiliar. I wouldn't want to be frustrated with new gearing on my vacation

B) In the long run, you'll minimize the expense. Owning two sets of drivetrains isn't probably what you had in mind. With a road solution you can ebay, donate, CL, your old cranks etc because there will be no compelling reason to go back.

C) You will minimize the transformation of the bike. A bike is also an "object" worthy of appreciation and your Specialized is a great looking bike. It just needs a 30T inner ring.

One solution is what I built up below. You'll need a new triple crank (I recommend the https://www.nashbar.com/bikes/Product...76_-1___205162, a new left shifter (Ultegra ST-6703), a new GS-size rear derailleur, and a new front derailleur. (Put all the parts you took off the bike up for sale, you won't be going back. :-) )

Will this crank work with the FC6601 bottom bracket that I have right now? Is there any reason this crank wouldn't work? It is entirely possible that this crank alone could do everything I want. If it is compatible, I could try it then add a new cassette and RD if I need taller gearing?

SRAM X0 2x10 42/28 Crankset

That's a neat idea - I'd expect to see something like this on a dedicated climbing bike. It's available in 175 and 170mm crank lengths and it looks like the BB might be compatible - here's the one SRAM recommends:



A new BB would be way cheaper than going triple anyway. And don't let anyone tell you to walk up hills rather than do this!

A mountain vacation. Some of those hills in the mountains are 20 miles long. That would be a long walk! I'd go for low gears.