Sprocket sizes on an SRAM Spectro 7

[Sammyboy]

I've got an opportunity to buy an SRAM S7 for cheapish, and I've realised that if it'll run a 14t socket, it'd work well for my super-fast Moulton. Question is, will it? If not, I still need an SA8. Anyone know?

[doco]

hey sammy, does this help out?

http://www.sram-imotion.com/us/html/navigation_us.html
...::: POWERED BY SRAM :::...

ooops doesn't say

[Sammyboy]

No it doesn't does it? I know they take SA type sprockets, so I guess it'll come down to whether or not they need to be dished. With the clickbox on the outside, I would assume (and hope) not. I guess that the 130mm spacing might also give me problems though - that's a lot of spread on a little triangle....

[LittlePixel]

Hmm - I need to cast my mind back but recall that you can't go below a certain size as although the SA-style sprocket will still fit, there's a shoulder next the cog that means the chain won't sit in the teeth properly beyond a certain size.

Mine came with a 14t I think or maybe a 15 - I liked it but thought the gearing a little low with my 52t chainwheel so went up one on the front and got a couple of smaller sprockets to try at the back. As I recall the 13t fit ok but the 12 didn't. This might be wrong though - it might have been that the 14 fit and the 13 didn't. I can check later on today as it still has the smallest one I could fit attached but it'll definitely take a 14 and maybe a 13 so that does answer your question...

Great hubs - the clickbox less so if you need to take the wheel off a lot for punctures (as I did).
h

[Sammyboy]

Thanks Huw. I believe the cranks on my Moulton are 60T (they're definitely bigger than 52), which would mean with a 14t:

60 / 14
1.74 100.4
17.6 %
1.48 85.4
19.4 %
1.24 71.5
24.0 %
1.000 57.7
23.5 %
0.81 46.7
19.1 %
0.68 39.2
19.3 %
0.57 32.9

Or 13T would be

60 / 13
1.74 108.1
17.6 %
1.48 91.9
19.4 %
1.24 77.0
24.0 %
1.000 62.1
23.5 %
0.81 50.3
19.1 %
0.68 42.2
19.3 %
0.57 35.4

Both of those fit within my parameters, though really I'd still rather a higher top - I seldom shift as low as 35.4 on my other bikes, and especially not on fast roadies. However, the price may be the defining factor; I had this hub earmarked for my tandem, but now I have an Elan 12 for that (dipping my toe in VERY murky waters!). We shall see.