louky

I was given a bike to fix by an organization that supports unhoused people in my town. It was a return that had been previously given out, the complaint was that it was difficult to pedal.

I can understand why. Two different size cranks, plus the cranks weren't quite in a straight line . Near as I can tell, neither of these cranks was stock on this box store dual suspension 26" MB. The black crank arm is a 170mm suntour, and maybe too nice for this bike when sold. The bike is black so I don't think the white (165mm) white crank was stock either. I am going to the co-op tomorrow to try to get something for low cost that will work. Can someone weigh in on what the more common configuration for these cranks is. Centerline of crank running across the diagonal or centerline of the crank running across the square. If I can find a 165mm LS crank on the diagonal I will be golden, but I may have to get a whole set. This is a 42t large gear. If I can't find that, I may have to go to 48t. Will I typically have to increase chain length and by how much? If I can't find 165mm stuff, will 170mm make much difference? Thanks for the help!

FBinNY 

You should have held off until the 1st.

And no, nobody except a very experienced cyclist would ever notice a 5mm difference in crank length if both sides match. Likewise most wouldn't notice even if both sides didn't match.

maddog34

unless you are under 5'6" tall, i'd go with a 170mm crankset. And as long as both arms are the same orientation to the crank spindle, you will be ok. the white crank is steel.. steel is heavy. heavy is not good on a bike. Get a set that has Aluminum arms.

As to the size of the chainrings (sprockets), Stay with the 42/32/22 sizes to avoid other possible problems... the Co-op will be able to find a nice set for you, i'm sure.

louky

I think the small chainring on the current one is 24. Will this cause a problem?

maddog34

Go to the Co-op.. ask for help.

a 22 or 24 tooth small ring will not matter one bit.

and i advised getting rid of that steel armed crank part, remember?

GO TO THE CO-OP.
ASK FOR HELP.

louky

Thanks, I will ask for help if I can. Many times the co-op is slammed as far as the knowledgeable staff helping other people. They will let me root around in the parts, but I need to know what I am looking for. I depend a lot on this forum for basic info, so I can at least have my questions in order when I get there. I did note your comment about the heaviness of the steel crankset. My goal in this work is to get the bikes back on the road as inexpensively as possible. Most of these bikes have a short "lifespan". Many of the folks who receive them don't have shelter and don't have access to tools or parts. They are ridden until they won't ride anymore, then brough back to the organization, where they are replaced if a replacement is available.

Kontact

This whole bike is going to be heavy. I don't see why the steel crank is an issue for a homeless bike. If a decent NDS match comes up, why not use it. This is not for RAGBRAI.

louky

I'm built just like this! Haven't ever seen myself run, but buying pants is a b*tch.

louky

Great verbalization of what I was trying to explain!

veganbikes

So you need to figure out the taper. That is the important thing, this one has a diamond taper on the DS and square taper on the NDS and while technically both are square taper they won't match up because it won't clock right on one side. Like you said put it together as cheaply as possible so steel cranks are fine or whatever you can find that matches. One of the cranks is probably fine just need to match that taper.

maddog34

i was trying to not have to type a book on proper bike fitment. i'm riding a 165mm crank length these days. i've shrank 2" over the years.and after numerous injuries.

Kontact

The crank length of a donated bike for the homeless doesn't matter. There are no KOMs at risk, here.

maddog34

i like to upgrade parts whenever possible.. and i don't look at who is a possible owner as a reason to deprive any owner of a great upgrade. Ypou have two dis-similar halves.. swap out the heavy half for a better part, IMO. There are a ton of those Suntour Cranksets in 170mm length around most used bike part outlets... one is lying on the shop floor 4 feet from me right now.

Rotating mass is "slow you down and eat up energy" mass. The bike may lose 7 to 10% weight if you upgrade to an aluminum arm crank set. You are at the perfect point to make someone's bike funner and easier to ride.
Or hope you find a steel 165mm length left crank arm that is usable... they bend, and also like to work loose, then wear,on the spindles...
tip: Shimano and most Sugino cranksets use the "diamond" JIS taper spindle holes... SR Suntour uses the "square" design. Both are JIS (Japanese Industrial Standards) internal taper. If the name sounds French or Italian, chances are that the Taper will be wrong for the (probably) Genesis bike's BB spindle.. they love putting those white cranks on bikes.

jadmt

we call it the mad dash to the islands of walmart and home depot. Gotta get to the primo pan handling locations first.

dsaul

They most certainly should notice that the crank arms aren't 180 degrees apart. Note the orientation of the square that interfaces with the bottom bracket spindle.

Kontact

He's talking about crank length and aesthetics, not the 45 degree offset.

FBinNY 

Actually, my laughter at seeing the orientation problem is why I suggested the OP should have waited until the first (of April).

I added the reference to length, as an afterthought, figuring the OP wanted an opinion.

wheelreason

You normally need to log into a salmon fishing site to see this level of trolling, but I'll play, "Just hit the center of the spindle with the oxy acetylene until it glows and twist it until the tapers align"...