GiantDefyGuy

I have a Giant Defy 3 with a Sora triple/8 speed. I'd like to change my crankset to a compact double. I'm not looking to "upgrade" as much as I'm looking to just not have a triple crankset on my bike anymore. Nothing is worn out or in desperate need of a replacement at all.

I've been poking around the internets looking at my options, and I came pretty close to ordering all of the Shimano 105 parts needed to turn this into a 2x10. But then I saw this:
https://www.jensonusa.com/store/produ...+Crankset.aspx

I've been reading that it's okay to use a "9-speed" crankset with an 8-speed cassette, and if that's true, I wouldn't really need to change too much. I'd need a 9-speed chain too and a new front derailer I guess. It should work with my current shifter, right? And this Bottom bracket: https://www.jensonusa.com/store/produ...m+Bracket.aspx.

So am I correct that I could just order that Double Sora crank and use it with my current 8-speed setup?

Thanks in advance for the help.

kaimat

You can get a 10sp 105 cassette for like $105 on Bonktown.

I'm new to road cycling, but what I've heard is that Sora is crap.

GiantDefyGuy

You have fallen for the hype, my friend. Sora is not crap at all! I know this for a fact because I have it and it rides just fine. No problems at all.

The reason I'm trying to avoid getting a new cassette is because I'd need new shifters too. Those are the kicker. So if I'm able to do this without changing anything but the crankset, that would be awesome!

AngryScientist 

you can use any crankset with your current set-up, 8,9,10 speed will be fine.

always match the chain to the rear cassette, in your case, all you would need to change is the crankset itself. i dont know if the sora triple shifter is triple/double specific, but either way you should be able to get away with setting the limit screws on your FD tight enough to allow the compact to work. that's the way ultegra works, so i'll assume it will work with Sora too.

i just bought a second hand cross bike with ultegra 9-sp and a triple, converted to a compact double with nothing more than a new crankset and FD adjustment.

LowCel 

Well you have heard wrong. Sora is a great group for the money and shifts great when setup correctly.

GiantDefyGuy you will still be using an 8 speed chain since your cassette 8 speed. The crankset should work fine as well. The only thing I don't believe will work is your triple shifter with the double crankset. Someone else will chime in soon to give you a definite answer on that.

LowCel 

Looks like I was beat on my reply by someone not typing on a phone.

jeffpoulin

Is there a reason why you can't just use the middle and outer rings all the time? To answer your question, if you have an index shifter for your FD, then going to a double may be an issue.

Elvo

You can get a used SRAM Force Compact Crank for ~$80 or so if you look at CL or the various classified forums.

LowCel 

There is a pretty big difference in gearing doing it that way vs a double. For example a sora triple is 50/39/30 so just getting rid of the small ring would give you a 50/39. Going to a double he will most likely get a 53/39 or a 50/34.

GiantDefyGuy

Wow, awesome information! Thanks all!

I'm not really interested in getting anything used. I'm just not into that. So yeah, in my opinion, a brand spankin' new Sora crankset is better than some random dude's older fancy crankset. PLUS, that Sora double crankset is effing beautiful (to me).

I DO have an indexed shifter for my triple, and I'm expecting to have to "work" with it, but I'm also expecting it to work. I don't care if I need to click twice to change rings, but I'm thinking that I may not even need to do that if I can get it setup right.

I could keep the triple and only use the outer rings. That's what I'm doing now (actually mostly just use the 42). I feel like I'm losing front shifting performance just because I have to have it work for a triple. I just think that I'll be happier on a double for reasons that have to do with shifting, cross-chaining, and beauty.

Also, thanks for clearing me up about matching the chain to the cassette instead of the cranks. Nice.

jrobe

You do realize that there are a difference between double and triple shifters and front derrailleurs. A bike with a triple drivetrain and a compact double drivetrain has different components besides the cranks. It cost substantially more than $69 to make this change if you do it the way Shimano has designed the gear.

desertdork

GiantDefyGuy

Sora FC34xx cranks have an integrated BB spindle which is compatible with external BB cups. If you get the 3450 crankset, get the BB cups if you don't already have them. From the info in your post, I believe you've got a 3304 triple crank which uses an octalink BB. Different system altogether.

lunchbox1972

I run a double on my triple shifters, no issue.

If you are currently running a Shimano Hollowtech II crank, this will slip right it. You will have to adjust the front derailleur and you may/may not be happy with the way that shifts. You can always get a double specific front derailleur if you are not satisfied witht he shifting..

Your long cage rear will work, but you could "upgrade" that into a short cage, most likely.. You don't need to though.

GiantDefyGuy

I totally realize that. That's why I started this thread......to see what kind of options I have, and to see if any options I THOUGHT I had were valid or not.

Changing the entire drivetrain is like $600 instead of ~$100, so I'm just looking to see what I can do. I'm also trying not to have a box of perfectly good parts that I replaced when I maybe didn't need to.

GiantDefyGuy

Yeah, I was going to get the cups too. They're like $15 or so.

Good info. Thanks.

GiantDefyGuy

Thanks everyone. It looks like I'm going to try this.

Right now, my shopping list is the Sora crank, the BB cups, and a Front Derailler. That's about $100!

MegaTom

You may be able to get away with using your current derailleur. You would just need to adjust the high limit screw so that it is in position for the big ring, and you can completely lock out the 3rd position with the low limit screw. I've seen that work with some FDs, while others seem to not have enough range in the high and low limit adjustments. I've never had a chance to do that with my Sora 8-Speed group, but the guy at the LBS that sold it to me said it should work.

clink83

The only thing that really needs changed is the FD. You could jury rig the triple FD, but they are so cheap online it's not worth it. Other than that, a triple shifter just needs the limit screws adjusted properly and it will shift a double fine. Campy doesn't have a double or triple shifter, it uses the same prinicple.

bengreen79

The Sora FD/shifter on my Allez compact double supposedly works with either a double or triple.