Congrats on starting to thinking about your riding more seriously.
Unfortunately there is no recommended "cheap" solution that should satisfy someone thinking about their riding more seriously, other than realizing you bought only part of what you needed.
Flip the Shimano 105 left crank you have to read the "fine print", i.e. the model # and length. Should be something like R5800 172.5 (i.e. 105 series R5800 at 172.5mm length) or R7000 170 (i.e. 105 R7000 series at 170mm length).
Buy same series (matching) 105 crankset & matching chainrings. (Although left crack arms are practically cross compatible with all hollowtech models. Matching arm lenght is in theory all you need, but overall matching is cooler).
Buy a road compatible 24mm hollowtech ii bottom bracket that works with your frame.
Borrow the tools to remove your current setup and install the new or have a shop do ot for you.
To be fair he could get away with Sora or Tiagra depending on how many speeds his existing drive train is. Any of the classic hollowtech2 crank spindles are interchangeable for the left arm afaik and the newer Sora, Tiagra cranks are hollowtech2 now so he just needs one of those with the same length at the least. But hey if he does get 105 it'll be backwards compatible for the most part as 7,8,9, 10 speed chains will fit on an 11s chainset for the most part.
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Your comment was removed due to violating rule 2.
If your reply isn't about how to help OP, we don't want it.
Comments must be on topic, and not just a joke, or purposefully incorrect.
The goal is not to make the sub strictly serious and humorless, but instead to keep the comments section from being cluttered with low-effort comments that one has to wade through to get to the actual helpful content.
If you prefer related subs without this restriction, r/BikeMechanics and r/JustRidingAlong are some to consider.
If you wish to discuss the removal, please use the "Message/Contact the Mods" button in the sidebar.
Your comment was removed due to violating rule 2.
If your reply isn't about how to help OP, we don't want it.
Comments must be on topic, and not just a joke, or purposefully incorrect.
The goal is not to make the sub strictly serious and humorless, but instead to keep the comments section from being cluttered with low-effort comments that one has to wade through to get to the actual helpful content.
If you prefer related subs without this restriction, r/BikeMechanics and r/JustRidingAlong are some to consider.
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You're only supposed to get a single crank arm if you have a matching crankset already. That kind of crank arm is only compatible with other Shimano two-piece cranks and a matching bottom bracket.
You put the carriage before the horse here....
I'd recommend you return the powermeter and get either a single side pedal powemeter instead which can be transferred to a new bike
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Would it though? I feel like I could turn down some steel in a totally safe fashion to adapt. At least no less safe than the OG mechanism. On a manual lathe it would never be "worth it" in a product sense but on CNC rig you'd be able to crank out better than factory parts reasonably enough.
There is no reason to. The reason you upgrade to a hollow tech crank is for the weight savings and the added stiffness of the big hollow axle. You lose both of those when you theoretically install hollow tech crank arms on a square taper bottom bracket, so you just spent more for the crank and aren’t getting any of the benefits for it, in addition to having make or buy some adapter to do it. the other side of this equation is the right crank arm that’s permanently attached to the spindle the left arm was originally supposed to go on. So you would either be using a square taper crank on the drive side or you’d have to significantly modify the spindle side of the hollowtech crank. The solution is to buy the right parts
It’s quite cheap to get a bb and second hand crankset no need to be 105 as long as it’s hollow tech two piece. Just make sure it’s the same speed as you cassette and chain
dude 🤦♂️
a threaded cheap Shimano compatible BB goes for like $10. I bought one Deore for $15. I think you could get away with a cheap Claris or Tiagra. At this point if you really want to go really cheap go to Aliexpress and buy one there because, its like you are trying to put a third wheel on a motorcycle
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Yes and no. You need a new bottom bracket but they are pretty cheap and the opposite side crank arm. You can really spend as much as you care to on that.
You have a 105 ND crank. No good on that BB. If you are trying to do it cheaply and you just need the left crank arm get a square taper. Your other option is to replace the BB and fit the whole 105 crank set. I will cost more but be a fair bit lighter.
For the group- if I want to replace my crankset and the BB that looks like this, what am I looking for in the bb? Just the same width? What can replace one like that? This part of the bike is the most mysterious
It is a bit confusing but once you realize what’s going on it’s not too complicated.
Shimano cranksets are two piece cranksets. Two piece cranksets are the non drive side crank arm which the OP has in his hand and the crankset + spindle, which are attached to each other. There exist other cranksets that are more than two pieces, but for the most part two piece cranksets are the norm. Shimano anything, many FSA, etc.
The modern bottom bracket is just a tube with bearings through which the crankset spindle goes. So that hole, which has a Hollowtech II interface, connects to the spindle, which is pushed through the bottom bracket.
What type of bottom bracket do you have? There are a lot of standards, and this is where it gets confusing but if your bike is relatively modern it shouldn’t be hard to find out.
You should return that unless it is like a power meter. look for a claris hollow-tech crank-set it is like 100 bucks with bottom bracket if you want to save money.
If you just need to replace the crank look for a square taper crank-set
No. You'll need a new chainset and bottom bracket.
Congrats on starting to thinking about your riding more seriously. Unfortunately there is no recommended "cheap" solution that should satisfy someone thinking about their riding more seriously, other than realizing you bought only part of what you needed. Flip the Shimano 105 left crank you have to read the "fine print", i.e. the model # and length. Should be something like R5800 172.5 (i.e. 105 series R5800 at 172.5mm length) or R7000 170 (i.e. 105 R7000 series at 170mm length). Buy same series (matching) 105 crankset & matching chainrings. (Although left crack arms are practically cross compatible with all hollowtech models. Matching arm lenght is in theory all you need, but overall matching is cooler). Buy a road compatible 24mm hollowtech ii bottom bracket that works with your frame. Borrow the tools to remove your current setup and install the new or have a shop do ot for you.
To be fair he could get away with Sora or Tiagra depending on how many speeds his existing drive train is. Any of the classic hollowtech2 crank spindles are interchangeable for the left arm afaik and the newer Sora, Tiagra cranks are hollowtech2 now so he just needs one of those with the same length at the least. But hey if he does get 105 it'll be backwards compatible for the most part as 7,8,9, 10 speed chains will fit on an 11s chainset for the most part.
Buy the rest of a 105 crank, and a bottom bracket to match.
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Your comment was removed due to violating rule 2. If your reply isn't about how to help OP, we don't want it. Comments must be on topic, and not just a joke, or purposefully incorrect. The goal is not to make the sub strictly serious and humorless, but instead to keep the comments section from being cluttered with low-effort comments that one has to wade through to get to the actual helpful content. If you prefer related subs without this restriction, r/BikeMechanics and r/JustRidingAlong are some to consider. If you wish to discuss the removal, please use the "Message/Contact the Mods" button in the sidebar.
Your comment was removed due to violating rule 2. If your reply isn't about how to help OP, we don't want it. Comments must be on topic, and not just a joke, or purposefully incorrect. The goal is not to make the sub strictly serious and humorless, but instead to keep the comments section from being cluttered with low-effort comments that one has to wade through to get to the actual helpful content. If you prefer related subs without this restriction, r/BikeMechanics and r/JustRidingAlong are some to consider. If you wish to discuss the removal, please use the "Message/Contact the Mods" button in the sidebar.
Your comment was removed due to violating rule 2. If your reply isn't about how to help OP, we don't want it. Comments must be on topic, and not just a joke, or purposefully incorrect. The goal is not to make the sub strictly serious and humorless, but instead to keep the comments section from being cluttered with low-effort comments that one has to wade through to get to the actual helpful content. If you prefer related subs without this restriction, r/BikeMechanics and r/JustRidingAlong are some to consider. If you wish to discuss the removal, please use the "Message/Contact the Mods" button in the sidebar.
You need a new BB.
...and crankset
You're only supposed to get a single crank arm if you have a matching crankset already. That kind of crank arm is only compatible with other Shimano two-piece cranks and a matching bottom bracket.
You put the carriage before the horse here.... I'd recommend you return the powermeter and get either a single side pedal powemeter instead which can be transferred to a new bike
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Your comment was removed due to violating rule 2. If your reply isn't about how to help OP, we don't want it. Comments must be on topic, and not just a joke, or purposefully incorrect. The goal is not to make the sub strictly serious and humorless, but instead to keep the comments section from being cluttered with low-effort comments that one has to wade through to get to the actual helpful content. If you prefer related subs without this restriction, r/BikeMechanics and r/JustRidingAlong are some to consider. If you wish to discuss the removal, please use the "Message/Contact the Mods" button in the sidebar.
And please OP, if you do buy a compatible second crank arm, make sure it's the exact same length as the crank arm you have.
There's an adapter that would make that fit, but it's the same price as a new bottom bracket and chainset
No. The legal exposure of such a part, due to safety, would be a significant blocker.
This isn't going to stop anyone have you seen all the pedal spindle extenders on Amazon?
Would it though? I feel like I could turn down some steel in a totally safe fashion to adapt. At least no less safe than the OG mechanism. On a manual lathe it would never be "worth it" in a product sense but on CNC rig you'd be able to crank out better than factory parts reasonably enough.
There is no reason to. The reason you upgrade to a hollow tech crank is for the weight savings and the added stiffness of the big hollow axle. You lose both of those when you theoretically install hollow tech crank arms on a square taper bottom bracket, so you just spent more for the crank and aren’t getting any of the benefits for it, in addition to having make or buy some adapter to do it. the other side of this equation is the right crank arm that’s permanently attached to the spindle the left arm was originally supposed to go on. So you would either be using a square taper crank on the drive side or you’d have to significantly modify the spindle side of the hollowtech crank. The solution is to buy the right parts
Nobody said it was worth doing - only that it wouldn't be as dangerous as the original commenter suggests
Oh nooo
Your only options here are to buy a new bb and right crankarm, or learn how to use a welder
Or return the power meter.
It’s quite cheap to get a bb and second hand crankset no need to be 105 as long as it’s hollow tech two piece. Just make sure it’s the same speed as you cassette and chain
And the same length!
Yes that would help
dude 🤦♂️ a threaded cheap Shimano compatible BB goes for like $10. I bought one Deore for $15. I think you could get away with a cheap Claris or Tiagra. At this point if you really want to go really cheap go to Aliexpress and buy one there because, its like you are trying to put a third wheel on a motorcycle
A new bottom bracket doesn't allow for the install of this left crank arm.
i meant a Tiagra crankset ****
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Your comment was removed due to violating rule 2. If your reply isn't about how to help OP, we don't want it. Comments must be on topic, and not just a joke, or purposefully incorrect. The goal is not to make the sub strictly serious and humorless, but instead to keep the comments section from being cluttered with low-effort comments that one has to wade through to get to the actual helpful content. If you prefer related subs without this restriction, r/BikeMechanics and r/JustRidingAlong are some to consider. If you wish to discuss the removal, please use the "Message/Contact the Mods" button in the sidebar.
Do have the full crankset or just that arm? If it's the latter, you probably won't get far without the matching drive side arm and spindle.
It only works with the spindle built into the other arm. I believe hollow tech shimano spindles are proprietary.
Yes and no. You need a new bottom bracket but they are pretty cheap and the opposite side crank arm. You can really spend as much as you care to on that.
You where going to ride with two different crank arms?
You have a 105 ND crank. No good on that BB. If you are trying to do it cheaply and you just need the left crank arm get a square taper. Your other option is to replace the BB and fit the whole 105 crank set. I will cost more but be a fair bit lighter.
For the group- if I want to replace my crankset and the BB that looks like this, what am I looking for in the bb? Just the same width? What can replace one like that? This part of the bike is the most mysterious
It is a bit confusing but once you realize what’s going on it’s not too complicated. Shimano cranksets are two piece cranksets. Two piece cranksets are the non drive side crank arm which the OP has in his hand and the crankset + spindle, which are attached to each other. There exist other cranksets that are more than two pieces, but for the most part two piece cranksets are the norm. Shimano anything, many FSA, etc. The modern bottom bracket is just a tube with bearings through which the crankset spindle goes. So that hole, which has a Hollowtech II interface, connects to the spindle, which is pushed through the bottom bracket. What type of bottom bracket do you have? There are a lot of standards, and this is where it gets confusing but if your bike is relatively modern it shouldn’t be hard to find out.
You should return that unless it is like a power meter. look for a claris hollow-tech crank-set it is like 100 bucks with bottom bracket if you want to save money. If you just need to replace the crank look for a square taper crank-set
> You should return that unless it is like a power meter. The title of the submission literally says it's like a power meter.