michaelm101

I just bought another version of a bike I already own due to the frame geometry. This one is set to be my "power shopper" / errand bike as it's simply perfect for riding around locally in the flats. It's got front and rear rack mounts, fender mounts, and a square taper 1 x 9 (38 x 11-34) drivetrain! I did a test ride and the gearing is spot on for the tasks at hand, including some off-road automobile dodging. HOWEVER, the cranks are 172.5mm and I can immediately feel the difference in efficiency as I use 175s on all my bikes.

I have not been able to locate a 175 crankset with similar specs. I feel as if this crankset is a rare configuration without an adequate substitute. BMX is too short, fixie cogs are too big, and the 110BCDs can't accommodate a single 38 without complications or looking odd.

Does anyone have any suggestions?

Thanks as always for your informed replies!

chas58

2.5mm is nothing on a crank. I'm thinking your feeling something else. I use 175 for high torque applications and 165 for high rpm applications, but really, 2.5 mm is nothing I notice. What exactly do you feel the difference is?

rhm

You can get a 38t ring for a 130 mm bcd crank. It's not a common item, but they exist; not that I can imagine what's wrong with using a 110 mm bcd spider.

175 mm cranks are unnecessarily long, in my opinion; I know of no benefit to using a crank longer than 165. Using the 172.5 really shouldn't cause you any problems. But whatever; 175 mm cranks are not that hard to find, in either 110 mm bcd or 130 mm bcd.

martianone

I run a 1x9 with 38 t chain ring and 12-36 cassette.
Some suggest a couple mm in crank length does not make a difference,
That is not my experience.
Not sure what the OP is asking.
Chain ring on my 1x9 is from origin 8, for 130 mm bcc crank

nayr497

Sorry if this is completely useless, but I'll put it out there just in case. I built up my first real commuter (would always go too fast/racey in the end) bike last year. Went with a SRAM Rival 1 GXP 172.5mm 110 42T X-Sync Crankset up front and an 11x36 in the back, it's a 1x10 drivetrain. I live in a pretty flat city, gets me around just fine, though I wouldn't mind a 38 or bigger in the back, but the Shimano XT RD only will accept up to a 36. This is my first 1x setup and I love the simplicity and the single shifter pod.

tFUnK

Shouldn't be that difficult to find a 175mm crank, 110 or 130bcd, and a 38t chainring.

Leebo

175 mm are long? Hmmm, everyone is the same size? Works for me at 6'4"

Leebo

Lots of options for a single ring. Check out some mt bike ones, like any. White, Surly, Velo orange should be of help. Also Rivendel.

michaelm101

Forgot to mention that I wanted to utilize the existing nifty little "chain guard" that encases the single sprocket. Keeps it from coming off. Yep, it's 104 BCD, but this ones a square taper interface and I don't really see too many of these...

In terms of crank length, I ride much more efficiently and cover more ground with 175s. I'm not a physicist or a physiologist, but IMO, leg (femur/tibia) length and crank length are correlated in terms of power and energy efficiency.
A few mm in crank length multiplied by thousands of revolutions adds up. This reminds me of a type of tennis ball I once used during an arm injury, They were called DUNLOP 'Absorber' balls. The label read, "15% less shock." I thought, "Oh boy, a whopping 15 percent...."
I then multiplied that by the thousands of times I struck a tennis ball every week and realized the extra $$ was well worth it. They have since been discontinued, but I can say that they certainly helped me through a rough period in my life...

tFUnK

Technically you should get a narrow wide chainring and not need that bash guard. But if you insist on using it, then you'd just need a 104 bcd crank and a 38t ring. Why does it have to be square taper?

carlos danger

just get any double or triple. grind the teeth off the big ring. remove the small and get a middle of your choice.
Just look up with bolt pattern would suit you best. 4-104, 5-130 or 5-110 etc. some patterns are easier to find certain tooth rings for. I'd guess a 38 or 39 would be very easy for the 5 bolts since they usually come in 39-52 and similar.

carlos danger

just use the out ring on a regular as chain guard.
also shimanos hollowtech 2 BBs cost like 10 bucks on chainreactioncycles. I would ditch square taper and get shimano HT2 cranks instead. Cheap and good.

michaelm101

I think I'll go that route! Thx!

Darth Lefty 

carlos danger

michaelm if you look in my thread in the road forum. you will see 2 cranks (identical) that I just ground the teeth away from the big ring. and put a 42 on the inner pos. 9sp. very easy diy project. I do this on all my bikes since i like 1x systems. here is a DA crank i converted to 1x

fietsbob

middle ring of a triple crank is in the center, like a single ring chainring should be..

My 9 speed is a Sram i9 IGH..

michaelm101

Very cool. However, I don't have a grinder, nor do I have the patience to grind all those teeth!