ridemgis

I have a 2014 Surly Disc Trucker with Shimano Sora FD & Andel RSC6 Crankset. Currently have a 26,36,48 triple. Can I do 24,34,42 or do I need to maintain that 12 tooth difference between the middle and outer?
Thanks!
PJ

bikemig 

If the jump is too big that can be a problem for the front derailleur. A smaller jump won't be an issue for the FD. Do these gear ratios make any sense? You may find that you are better off staying with what you already have.

ridemgis

I've been biking for 20 years and never had much reason for the outer ring unless I want to hit 50 mph downhill. More often than not I'm in a low to very low gear spinning a 100 rpm. I can rack up an entire day and many miles that way. And I've never been a strong climber - I'm quite content to drop to 5mph on a long hill.

So it seems like my options are to swap in a mountain triple with a 22-32-42 or do what I can with the current hardware by only changing the rings. And I'm thinking, perhaps mistakenly, that a new crankset would probably require a new front derailleur and bottom bracket. ?

mdilthey

A new crankset doesn't require a new bottom bracket unless you change the spindle. Your Andel crankset looks like a pretty typical square spindle, so you can swap in a lot of other cranksets. If you want to go with a Shimano crankset, it's probably going to be Hollowtech II, in which case you'll need to spend $25-35 on an outboard bottom bracket. That new BB will still work with your 68mm English-thread BB shell. No big deal. No compatibility issue here if you get the same spindle as the current BB, too.

I think your logic with switching your triple sounds about right. I, too, didn't need the 50T on my outer chainring and instead opted for a 46T, and I don't miss the extra power at the top end when loaded touring.

As long as your triple crankset is ramped for 22-32-42, it works with your triple front derailleur (I'm 99% sure, someone can correct me or confirm). My Sora front derailleur adjusted fine between a 34-46 and a 34-50. It shifted both. So, no worries on compatibility.

And finally, go for this. Really, it sounds like you'll just end up with a bike that is closer to your ideal. Keep the old crankset as a backup. Buying three rings will cost almost as much as buying a new crankset, so just get a new crankset.



As a final warning, talk to your LBS about this switch. Just to make sure there's no funky differences between what you're getting and your current chain, cassette, BB, and FD.

nun

The new rings will work with your derailleur, but you might have to adjust it down a bit to get the best shifting.

If you want a 42 outer ring you'll have to get a new crank because 44 is the smallest outer ring made for the 110mm BCD of your current crank, but you could do 44-34-24 by just buying new rings. Alternatively you could get 42-34-24 using a 94x58 triple like the TA Carmina

TA Carmina cranksets from Peter White Cycles

ridemgis

Thanks all. I think I will go for the mountain triple. 22-32-42 I'll be using the full range available.

fietsbob

Back plates of triple FD are deep.. to better push the chain up from the smallest Ring.

so too small a mid to outer difference, & then FD has to be raised to clear the middle one to shift up to the big one,
which makes the FD seem high above the outer ring, when viewed from the right side.

ridemgis

Well I'm thinking that the 22-32-42 triple will need a new derailleur anyway. Looking at the Sora its seems the tail is too long to move it down to the 22 without hitting the frame first.

Null66

There's a really good reason that doesn't involve top speed.
There's a trick I learned that helps you recover.
Works best on the descent. Upshift pedal slowly very, very, lightly.

It really helps maintain circulation in your legs which helps your legs recover, but also takes a load off your heart.
oh and you stretches out your coasting...

<edit>
Says the guy running 22,32,44 11-32...

Doug64

fietsbob is right on. If the difference between the middle and large chain ring is less than 12 teeth, the back plate will not allow you to get the FD low enough to the large chainring to shift smoothly. Look in Shimano tech docs on line to find out the limitations of your particular derailleur. For Sora FD 3503 will have the large rear plate, and the 3403 will have the smaller plate. At least that is how their numbering system seems to work for other FD's. I learned the hard way when putting a 46/36/34 crankset on a bike. The 4503 Tiagra FD would not work with a 10 tooth difference.

Also, just because you have a square tapered crank not all cranksets will work. Mountain cranks require a shorter bottom bracket spindle length to maintain the proper chainline.

A 24 tooth small chainring will work on the stock 5 arm crank. I put one on my daughter's LHT.

Disposable

I have the same bike with the same crank and derailleur, and changed it out this summer for the same 24-34-42 rings. I lowered the derailleur a little to match the smaller big ring, and shortened the new chain by, I think, two links as compared with the old one. The only problem I had was the new stainless rings I got caught the chain at the bottom with a resounding CLUNK for the first 60-80 miles, but they've been fine since. A 42 tooth isn't a common outer ring, so I got flat rings with no ramps or pins, and after the first week I didn't notice any difference in shifting. I did have to get some tiny, thin 0.6mm spacers to maintain the proper middle to outer gap with those steel rings.

I find I do a lot more double shifting now, but I'm also a lot more comfortable on the hills and I don't feel like the big ring's just ballast. I changed mine out for the lower gearing, and picked those sizes because it almost completely eliminates duplication in the ratios. It turns out that hasn't really mattered to me, because I don't feel the even-ness of the shifting when I'm grabbing for a lower gear.

nun

TA produce a vast number or rings

Chainrings

I've been riding TA 42/26 rings on a Sugino SD 110x74 BCD (I don't use the outer ring) for a long time. I offset the BB by a few mm to get the chainline right.