tristan3b

I want to switch over to FSA’s TT-style chainrings on my new tri bike build, but I am unsure about the mechanical implications of what I have in mind…I want to do 55t/44t chainrings with a SRAM Force front derailleur. However, the SRAM Force front derailleur is supposed to be good only up to a 54t big ring. Anyone out there know how hard and fast the manufacturer’s specs for front derailleur/chainring interface are? How much difference (in circumference, right?) could 1 little tooth make, anyway?
Thanks,
Tristan

Edonis13

55/44??? damn son, are all your bike courses perfectly flat?

but yeah, i cant actually help you. sorry.

cslone

Do you know how big a 55/44 is? I am a huge masher and gave up on that setup 2 years ago.

As far as the question, it probably really depends on your derailleur mouting and if you can get it high enough to clear the ring. I wouldn't think a 1T difference is that big. If you have a clamp on it may work. A braze on and you may have to dremel it up to raise the FD.

tristan3b

looks like i may be getting in over my head! to be honest, i thought this was more of a standard setup--i am a rookie--and also i should have mentioned the wheels are 650c...for what it's worth...can anyone out there recommend a more versatile gear ratio?

cslone

Well, that changes it. Sorry, I didn't even think about that. A 55/44 should be faily close to a 53/39 with 650's. You can search for a gearing calculator to play with cassette ranges.

cjbruin

Here's my go-to gear calculator. I find it to be very helpful.

https://sheldonbrown.com/gears/

tristan3b

Thanks guys for the responses. Looks like 56/44 might even be a little closer to what 53/39 on 700c--I might even go with that, as crazy as that sounds. Anyone have opinions on FSA vs. Dura-Ace tt chainrings? I would naturally lean more toward DA...any opinions?

Sprocket Man

My bike:


I have a 55/44 setup. My wheels are 650 as well. The FSA chainrings work just fine. I imagine that the DA chainrings would work just as well as the FSA. I chose the FSA chainrings over the DA chainrings because the FSAs were less expensive and personally, I really like the way they look.

Treefox

You've already dropped the cassette down to an 11-23 or similar, yes?

tristan3b

Treefox: Yeah, thanks--I got a 11-21 10-speed cassette, so I figure that's about as low as I can manage in the back, right?!
SprocketMan: Thanks for putting the picture of your ride in there--very cool to see what other folks are doing. Sounds like we may and up having pretty similar setup in some ways...
cslone and cjbruin: thanks for the info on the gear ratio, and yeah, it turns out the 55/44 on a 650c is pretty close to what 53/39 on a 700c would be. Turns out 56/44 is even closer. So, looks like I will be going with 56/44 in the front and 11-21 in the back. Whew!

tristan3b

a little update for those who have been in here with me on this thread...I ended up buying a set of Dura Ace 7800 TT chainrings (went with the DA as opposed to the FSA based mostly on aesthetics, but also got an okay deal on eBay) only to find that the interface between the rings and the crank at the spider is far from seamless. Yes both are 5-bolt 130bcd, but the DA rings are a lot beefier then the SRAM Force HCT cranks I was trying to fit them to...looked bad, dangerous (?) and definitely NOT aero (!). Anyway, there was alot of overlap at the spider, a problem I imagine would be not a problem with the FSA rings as they are solid (no gaps) around the clamping circle...unless, does anyone out there happen to know, are the FSA pretty beefy at the bolting part? They are lenticular, so-called, which I would imagine means "a little thick in the middle compared to the outer edge" so I wonder if there are any issues with the depth of the clamping area interfacing with non-FSA cranks?