I have two to choose from for the Mongoose Iboc rat build. One is a brand new 36t inner ring that came with the Sram cranks I’m using. Supposedly it’s for “10 speed chains only”. It’s not ramped or pinned. The other chainring is an older style 40t SR ring. This is used, plenty of life left, and not as modern so probably more suited to 7/8 speed chains.
Suggestions?
Oh, the largest sprocket on the cassette is 32t.
I used a single ring 39t round town with a 12-27 cassette and it was enough range.
I’d try the 40t one. Both with probably work just fine, just try them out?
40x32 is ridiculous for around town!
Unless you’re portaging lead or climbing steep, loose surfaces, why not run a 12-25? You’ll need an MTB mech or some serious B Screwing to clear the large sprockets.
If the answer is ‘I have the cassette already’, as you were.
Use the 40T.
Use a Wippermann 8sp chain. (But I know ya’ll wanted that 808)
I have the cassette already on the wheel which is the only reason I’m using it.
Probably gonna run SRAM X4 trigger shifter and matching rear long cage derailleur.
Would maybe go a bigger front ring, but I might as well run one of the ones I already have.
I’m glad to see you have decided to eschew drop bars for this bike.
Yeah, gonna run a flat bar for now. See how I go.
What tyres you running? 40T is kinda high for a mtb
Whatever 26" Kenda knobbies Larfinboy included with it.
If you were running slick Fred 26 tyres I’d say 40T is fine. But knobbies, 40T is too much IMO.
Go 36T and you actually use the mtb for what it was designed for, ie go off road.
SUV. Ha.
40 should be fine
40:32 gives you a ~32’ low gear which should be fine for the col du small lump or whatever the cat 1 climb is on Zoltans commute
whats the smallest sprocket?
36:11 will still give a reasonable high gear but at 36:12 or 13 you might run out of top end (yes i know)
So why the knobbies then??
soccer mum Zoltan 
cos they’re what he has
also possible epic trolling
Cos they’re on there.
I will take this off-road. Maybe.
Ah, see!
Knobbies are cool for a commuter bike (as long as they are decent quality). If they are heavier than 600g, rip them off.
is this a troll thread?
No, and I’ve received my answer.
Just don’t come crying back to FOA if you find 40T is overgeared. Remember, MTB 26 is QUITE DIFFERENT than a fixie.