trigger

I'm building up my first SS/FG. I've determined that I need to run 69 or 70 gear inches to be able to do all my usual routes ... truthfully, I could go a little higher, but I'm worried what that might do to my knees over the long run.

Questions:

1) what's the most sensible chain ring and cog combo to gear this? I'm not that concerned about skid patches.

2) I'm planning to run a flip-flop hub with fixed / free. what's the general wisdom there ... run a bit higher on the fixed side than the free-wheel?

Any help on this would be greatly appreciated. I think I know just enough to be dangerous, which worries me!! Also, this will be my first single speed of any sort, and while I have ridden fixed before and like it, I don't have much knowledge of ratios etc and the conventional ways to build / gear things. I'm used to life on a road bike.

Thanks in advance!

tmh657

Did you check this out?

https://www.bikeforums.net/singlespeed-fixed-gear/468351-gearing-primer.html

If you care about looks then a bigger chain ring looks better, IMO. 48 x 18 = 72.0 GI

I have never run a SS on a flip/flop. I have a fixed/fixed hub. 81 GI on one side and 75 on the other. Works for me cuz I don't have a lot of hills.

If I want to coast I go with gears.

trigger

Yeah, I'd checked that out. That's how I figured out the gear inches I'm favoring.

My big question I guess is if I'm running a flip / flop, how best to make use of the two different cogs. I think that 49 x 19 = 69.6 inches is going to be my happy place for a while, but I've been figuring this out riding my road bike and not switching gears. I can do all my regular routes in this combo without stressing out my knees ... I can make it up the hills and though I spin out on the descents, it's manageable.

I'm thinking that maybe the other cog should be a little steeper gearing wise for larger descents?

Gawd this is making me feel dumb.

trigger

um ... they don't make a lot of chain rings in a 49 though, do they? In which case, 50 x 19 = 71.1 inches.

^^see comment about feeling dumb. Oy.

Meepers

46/18 is 69 GI. just bough a 18t freewheel for my GF's single speed.

Cynikal 

The easiest way to get that range of GI is to use standard road parts. By this I mean parts that are not track/ss specific. A 42x16 gets you 69.2 GI and these are parts that most shops have in stock.

tmh657

I have a 49t Vuelta 1/8 " CR.

veganwar

49 tooth chainrings aren't that hard to find. But dont' forget to take into account that your road cranks are/may be longer than the cranks you are going to run on your new bike.

trigger

Yeah, I checked the gearing with crank length as a consideration. Thanks.

Does anyone have any advice as to what ratio difference I should run on the other side of the flip-flop? Higher or lower? I'm going to run fixed / free. Thoughts? Help?

Thanks!

jim-bob

I had the same thoughts when I first got a flip-flop hub, and figured "oooh, I can run multiple gears."

In all honesty, though, the last thing you want to do when you get to the top of that hill is get off the bike, pull your rear wheel off, flip it around, adjust brakes if necessary, and then go downhill where you'll do the same thing as soon as things get rough again.

I'd try to get my primary gear dialed in, and then run a bailout gear (lower) on the other side, just in case.

trigger

I also could just run the same gearing ... since one is going to be free and one fixed, the flip-flop will just be for those days when I really want to be able to coast. Once I've had the bike for a while I might ditch the free-wheel side eventually. I like / need the psychological security blanket of the freewheel for now ... just to know it's there, ya know?