Apologies if this is a numpty question…
TT bike has SRAM force crankset (130 BCD) with 175mm crank arms.
The more I look into it, I want to try this with shorter crank - ideally 165.
Can you not buy just the arms/spider without having to get the full chainset?
Chainsets themselves seem rare as hens teeth too. Sigma seem one of the few with much choice. Any less obvious places to shop?
Try looking for an Ultegra one
I picked up a 52/36 170mm 11sp for £85 
That’ll be compatible with SRAM
Will I be able to swap out my outer chain ring with it? Assume just needs the same BCD?
Eh?
Why would you do that?
I’m confused.
Just change the whole crankset.
It’s a 5 minute job. Max.
Arms are fixed ( length)
Rings can be changed.
110 bcd seems more common these days.
I have two bikes with 165 cranks, both tt, the other is 172.5, once I’d adjusted seat height it’s hard to tell any difference.
Some people got a much bigger comfort / performance gain.
I know sram do a 167.5 chainset, I’m assuming 165 too.
Seen a brand new in the box red ( 167.5) on flea bay recently
Cause its got an aero ring on it and I’m fickle 
Yeah bikes from 2012…so not new tech 
Aren’t Shimano 24mm spindles and SRAM 30mm GXP, so would have to change BB too.
My sram are all bb30 but your right, he would need a conversion kit or suitable bb I think
Its so frustrating. I only want to change the arms/spider. Now looking at entire crankset & bottom bracket.
New bike then?
Probikekit have 105 chainsets in 165mm
That work with 10 speed?
Yep, I used a 11 speed chainset with 10 speed everything else for years. You can run 11 speed chains on 10 speed too
How tall are you?
And why do you want 165mm?
Under 6ft - thats tiny right 
5ft 11/181cm.
a) Cause then I can get the saddle up - cant see any other way I can get that higher with current set up. Crank length seemed an easy way to find 10mm
b) To continue to try and work out why I cant hold power on that bike (plan a turbo session on TT to see if I can eliminate a few things)
Good luck getting a 130bcd 165mm crank!
You can mix and match with impunity in my experience. I have Rotor chainset, KMC chain, SRAM mechs.
Probably won’t make a difference at your height, TBF.
If you’re grinding on Zwift to get the power out, you might want a bigger ring and longer cranks to get the torque down. (And I mean “laying the torque down” here, not decrease it)
I’ve left the 172.5mm 50/34 on mine and was “spinning” in 50-11 on Wednesday.
I really must put the 175mm 55/42 on for next Tuesday 
I leave my saddle height well alone for the 2.5mm differences (my road bike 52/36 is 170mm)
With SRAM there are removable spiders could you just swap the speeder to move from 110 to 130? Or is the inner part that connects to the crank different?
I’m not sure I’m that strong tbh. What I also want to check is the power phases on the pedals. Im sure inside I have much less dead spots - where as outside I only seem to to have power on the down stroke;
That’s where you want to put the power on IMO, I have yet to see a study that shows good cyclists pulling the pedal up.
Thanks @r0bh I have been waiting for 165mm to come back in stock and this is the best price I have seen 
Single leg drills.
40s each leg.
20s with two.
Great practise for clipping in whilst moving away from junctions, too
