Bottom Bracket / Crankset Compatibility Help Needed
 

About 3 months ago, I bought a like-new condition 2006 Specialized Roubaix Pro that belonged to a good friend’s late father. I think this was one of their top line carbon models outfitted with Dura Ace all around. I bought it without riding it as I was familiar with the brand/model, in addition to that fact that I was getting an unbelievable deal.

When I brought it home and rode it, I discovered the left FSA K-Force carbon crank was slipping slightly (1-2mm slippage). I removed the crankset, examined and the tell-tale signs of carbon/alu de-bonding were present. Oh, well. “I’ll simply get a replacement crank,” I thought…

Here I am, 3 months of daily searching later, and the bike still sits on a stand, begging to be ridden. It has an FSA MegaExo BB with 24mm spindle accommodation and I have not been able to locate a left crank for it. It has also been difficult to find an entire compact crankset to fit the MegaExo.

--Since the FSA rep told me that carbon may simply de-bond with age regardless of usage, I hesitate to invest in an entire 2nd hand crankset off Ebay, etc.

--Since learning that MegaExo, Hollowtech II and GXP all accommodate 24mm spindles, will cranks listed as Hollowtech or GXP compatible fit my MegaExo BB?

If not, and I decide to replace the BB to accommodate more reliable cranksets (e.g. Ultegra, DuraAce) what BB style would be the way to go on this swap?

Thanks in advance!

If you decide to replace the crank set the crank set manufacturer will have a recommended BB to go with it - pretty straightforward.

I have a 2007 Roubaix and it has the Mega Exo crank and external bearing BB. I think it is an english threaded BB which means a simple removal/replacement using a few job-specific tools. Most threaded BB's are in the $20 to $30 range unless you want something super high-end.

Find the crank set you want first.

If you have a standard threaded bb, a Shimano crank and bb would be a good choice. However, a quick Google hints that you may have some weird bottom bracket.

Man, three months of a great bike sitting unused - get a new crank and BB!

I'd bet that you have a conventional British threaded bottom bracket which means that that the crank and BB will be easy to replace, and you can do it yourself with common hand tools and an inexpensive bottom bracket tool. One of the most easy DIYs w/ plenty of online tutorials. Or a very cheap LBS job.

I've read that there is some compatibility between some of the 24 mm cranks, but really, with the cost of BB bearing sets, just get a new set that matches your new crank. Don't waste any more time trying to finesse this thing!

If you're unsure about what sort of bottom bracket you have (the only siginificant question is threaded vs. press-fit, and I don't think press-fit was happening in 2006?), simply post a picture or describe what it look like.

Then, just get a new crank and matching bearings. The bearings are cheap regardless of which brand of crank you go with, about $30 as others have said. If you really want to keep the existing bearings, just shop for a matching crank. But I'd get the crank first and buy bearing with it. If you later find that the bearings you have are indeed compatible, just save them and use them later.

As for crank, you can go as cheap or as expensive as you want. The cheaper cranks by all manufacturers all look great and are perfectly fine for mere mortals. But heck you have a Dura Ace bike! That might effect your aesthetic sensibilities. 8-)

I have a Shimano FC R700 compact crank on one of my bikes and it's really a great crank. It's one of (or the?) Shimano's first forays into compact double cranks and it's said to be about Ultegra quality before they actually marketed group-specific compact cranks. A similar crank is the R600, a little cheaper. Looks and acts great with my otherwise Dura Ace 9/10 speed mixed component set up (9 speed shifters, but I think the R700 is officially 10 speed). Easy to find for cheap-ish on Ebay. But really, any Shimano, FSA, Sram or even Campy crank of any type with matching bearings will be fine with your Dura Ace shifters. Set a price point and get 'er done. Did you really say "THREE MONTHS???" That's Roubaix is a great bike and should be ridden daily!

Thanks. I discovered that HT2 compatible cranks will fit my MegaExo BB. Indeed, I've checked Ebay for the cool looking silver/black Dura Ace model 7900 cranksets and the compact 50/34s are few and far-between. Unless I can find an actual left crank for the FSA set, I'm going DA!

I have an FSA SLK 50/34 mega-exo crank/BB sitting unused. I replaced it with a Campy Chorus that matched the rest of my group just this past winter. Let me know if you want it for the shipping cost. The problem it always had is that the left bolt loosens as it was threaded the wrong way by design, and FSA changed it in the following years.

I'm not sure if all the mega-exo cranks were interchangeable, but there was a compatibility chart on their website somewhere. I think that's when I threw up my hands and replaced it all with Campy, just the frustration of finding something that works.

Hi there and sure, I'd take you up on your generous proposition. Just let me know what to do...
My email addy is: michaelm101@sbcglobal.net
Thanks for your attention!

OK, I'll get in touch via email. The crank is hardly new, the 34 tooth ring is newer than the 50 as I wanted lower gears than the original 50/36 and that seemed like an easy solution. It has the BB but it is shot. I'll send it to you and you can do what you want with it.