Chompers25

I have a CAADx Ultegra (with the replacement fork) that I would like to make a bit all-purpose and use for some gravel riding (I was going to buy a new gravel bike, but my derailler went wild on my roadie and fubared the carbon chainstay, so I have to rethink my purchasing strategy).

Anyway, it's currently 46/36 FSA Gossamer with a c'dale crank and BB30. I'd like to take it down to 46/30 after riding a friends bike around some of the local hills. I think this will give me the range I want. And, no, I'm not looking to change my rear cassette.

What are the best/cheapest options for this? Shimano GRX? SpideRing? An FSA option? Would love to hear your suggestions that aren't like $600. Is there any solution that doesn't also require a new BB?

Iride01 

Probably need to get GRX out of your head. Yes it's a gravel groupset, but your CAADx is probably set up with road group chain lines. GRX has a slightly wider chain line.

Is your front DR a clamp-on or braze-on? If the clamp-on type then you can easily move it down to match the smaller chain ring. If braze-on, you'll just have to find out unless another knows for certain.

Other than that, just look for a crankset that will take the ring sizes you want or already has them and has a BB that will fit your BB shell. Make certain they aren't made for bikes with wider chain stay spacing for wider tires as that is why Shimano made GRX with a wider chain line.... I think!

shelbyfv

I wouldn't necessarily rule out GRX. It works fine on one of my vintage steel bikes but I may have more tolerance than some for mechanical imperfection. I have no idea what would be needed to make it work with your bb. A mod can correct your thread title.

Chompers25

Oh, yeah, oops, a slight number mix up there. Meant 46/30

Chompers25

It's clamp-on, so that's a bit easier.

DaveSSS 

The grx cranks have a +2.5mm chainline. I used some spacing washers and longer chain ring bolts to correct it. I used McMaster-Carr 98370A015 washers. A little thinner washers won't require longer bolts.

msu2001la

Do you have an FSA Gossamer, or a Cannondale crank? They're two different things.

I'm assuming your bike has the FSA Gossamer, which my CAADX from that era also has. This is a 110BCD 5 bolt setup. The smallest commonly available chainring that fits this is 34T. There are some 33T versions out there, but they are hard to find. If you want to go smaller, you'll need a new crank.

If you have Cannondale's Hollogram or SI crank with direct-mount SpiderRing, you can buy a 46/30T ring for it: https://www.cannondale.com/en-eu/gea...pidering-8-arm

Chompers25

It's kind of a weird setup. I have the FSA Gossamer 46/36 original rings that came with the bike, but the Gossamer crank was replaced by a previous owner with a Cannondale Si. It's still a 5 bold, 110 BCD spider, so not the SpideRing format. You can see it here: https://imgur.com/a/1C7H6vO

msu2001la

Ahh, ok. I'm not familiar with that version of the Cannondale crank, but do remember reading somewhere about an older SI carbon version that was 110BCD, and this looks like that. Either way, I'm pretty sure 110BCD is limited to 34T min. I don't think there is a way you can get 30T without a new crank.

As for new crank options, you can run Shimano cranks on BB30 with an adapter (wheels mfg, or Praxxis). Cannondale's newer SI and Hollowgram SpideRing cranks fit the aforementioned 46/30T, and Easton makes the EC90, which uses a similar direct-mount spider that I think also has a 46/30 spider/ring option. These solutions all work with BB30 bottom bracket, but are all going to be in that undesirable $600 range though.

mstateglfr 

FSA Omega 46/30 in 172.5 or 175mm
https://www.bike24.com/p2344423.html

$108 delivered to the US.
I am pretty sure you need a 19mm FSA MegaExo press fit bottom bracket. That is based off what I remember when I changed out the BB on my wife's Cannondale with a road version of this crank.

Chompers25

I've come across this, but hadn't found many people using it. I did find this https://www.ebay.com/itm/154594437727, which seems to be similar but made for BB30. Granted, 165 mm, but no need for adapters.

mstateglfr 

Yeah, thats the same crank. I have 0 to offer when it comes to bottom bracket guidance between the two options as all I use are threaded bottom brackets so I dont get into the various press fit sizes and workarounds.
Anyways, the FSA Omega and Tempo cranks have been around for a long time and have come in 46/30 for a handful of years now. They were spec'd on bikes to get easier gearing before GRX was introduced, and are still spec'd on bikes, to be clear.
I installed a 46/30 Tempo crank on a friend's bike a few months ago because she wanted an inexpensive way to get lower gearing.

msu2001la

Cannondale currently sells 2x versions of the Topstone with both the FSA Omega and FSA Tempo cranks, both running a 46/30. The bike with the Omega crank is running a combo of GRX and 105 components, and the Tempo bike is running Sora.

You might want to compare weights before buying, if you care about that, as I suspect either setup is significantly heavier than your current gear.