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Crankset/Chainring question

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Crankset/Chainring question

Old 08-23-22, 08:39 PM
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m0unt41n_d0
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Crankset/Chainring question

Greetings, I'm rebuilding an old 3 x 9 mtb and my local bike shop, who is highly reputable by everyone around sold me a Shimano M-361 "hybrid" crankset/chairing combo among other parts for a complete drive train. I couldn't find a "groupset" that I liked within my price range and NOT a 1 x so I ordered everything separately but I didn't have a particular crankset or chainring in mind so I asked them for a recommendation and that was what they came up with. The tooth count matched what was originally on there, it has the 175mm crank arms and the cogs are serviceable/removable and the price was right.

I got a BBUN300 in 73 x 113 which is both consistent with what came off and also with measurements taken by me. I'm having some trouble getting things right and I just went to look online and while checking out my crankset I find that it's for 3 x 7 or 3 x 8 but can't find anywhere where it says it is compatible with a 3 x 9. It's too late tonight to call the shop but I would like to know if anyone has any input on whether this will work with a 3 x 9 or if the shop just goofed. I'd find that hard to swallow because I've been going there the entire 10 + years that I have lived here and they have always been spot on. They have prices that are usually at or even at times lower than the big online retailers, they almost always have what I need in stock and if they don't it never takes more than 2 business days for them to get it, they always know what I'm talking about and vise versa, they are open 7 days a week and are open 2 hours later than any of the other shops around on the weekdays. I also know that I'm getting genuine parts there as opposed to the uncertainty of ordering online due to the high volume of fake parts circulating around out there.

They do cater to more upscale customers than me as the floor is always stocked with $8,000 to $15,000 bikes and the vehicles in the parking lot are usually worth more than I make in a year but they have never treated me any differently than them. I just go there for inexpensive parts for old bikes that I fix up so the bums can steal them. It's my service to the community. Anyway, I'm going to call them tomorrow but am just looking for some input from others who may know more than I do about this particular situation.
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Old 08-23-22, 11:27 PM
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From what I gather on Sheldon Brown's website, a narrower chain for a 9 speed might be fine on 8 speed parts so it doesn't seem too off to do that... https://www.sheldonbrown.com/speeds.html
Have you asked the shop their thoughts behind the combination?
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Old 08-24-22, 12:09 AM
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I've not had any problems going from 7 to 9 on one bike (original crank when the bike was a 3x6) . 8 to 9 on 2 others.
When experimenting with crank length, I temporarily installed an old cottered crank from a (1972ish) 2x5 road bike. No issues. It was friction shifting on the front though.
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Old 08-24-22, 07:08 AM
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Check the chain line. See Sheldon Brown if needed. A new crankset may need a different bottom bracket length to maintain the correct chain line. One symptom would be if the FD limit screws are very unequal--one screwed all the way in, the other all the way out.
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Old 08-24-22, 10:09 AM
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Originally Posted by andrewclaus View Post
Check the chain line. See Sheldon Brown if needed. A new crankset may need a different bottom bracket length to maintain the correct chain line. One symptom would be if the FD limit screws are very unequal--one screwed all the way in, the other all the way out.
I do believe this is the answer to my issue. I'm going to try a BB with a longer shaft, 73 x 122.5.
I called the shop and they said it was the closest they would be able to recommend me within my price range and that as long as I had a 9 speed cassette and tear derailleur that it should work fine but they did not mention that I may need a different BB when I was in to order the parts but upon reading this I called them back and they said that the BB could be the cause so I had them order me a 73 x 122.5. From what I can tell based on the issue I'm having it seems like it will take care of it as long as it lines things up when I install it.

Thanks for the info and I'll post back with the results. I should have the new BB by tomorrow afternoon so I can install it after work.
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Old 08-24-22, 10:46 AM
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It sounds like you sized the bottom bracket to match the old one, but since youre replacing your crankset you may need a different length bottom bracket to fit that. Looks like if you have the square taper version of that crank, then the 122.5mm BB should work.
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Old 08-24-22, 10:55 AM
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when in doubt, consult the manual:
https://si.shimano.com/en/pdfs/si/6T...002-00-Eng.pdf
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Old 08-24-22, 11:06 AM
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Originally Posted by icemilkcoffee View Post
This is your answer. But the FC-M361 has a quirk. It seems the 7 speed crank is square taper and the 8 speed is octalink. If you talk to the shop, you should probably start off with, "I saw some Shimano Manuals online..."

But don't act too knowledgeable because you'll fall flat on your face.

Here is the main Shimano Tech Doc site...
https://si.shimano.com/en/

John
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Old 08-24-22, 02:38 PM
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I have the square taper 175mm FC-M361 22-32-42. I like the longer arms and the low gear ratio of the 22 tooth low with the longer arms gives me good climbing power. This is my FS bike that I use for technical stuff.

I also have a hard tail that's set up for the paved and flat dirt trails. That one is already finished and I had no issues with it. It was a simple build. I use it for work commute when the weather is nice and I don't have to transport tools but I got my hands on a matching FS and am setting it up for "off road". I ordered a 73 x 122.5 bb which will be at the shop tomorrow afternoon so I'll see if that solves the issue. As long as the drive side of the shaft is at least a half inch or so out more from the frame it should work. 122.5 - 113 is 9.5mm, which is close but hopefully will work. My half inch estimate is eyeballed so hopefully I'm over with it. I'll see tomorrow evening. Fingers crossed.
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Old 08-24-22, 03:05 PM
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From the Shimano Specs, 122.5mm (BB-UN26 (-K) is the correct BB spindle length.

John
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Old 08-24-22, 08:31 PM
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Originally Posted by 70sSanO View Post
From the Shimano Specs, 122.5mm (BB-UN26 (-K) is the correct BB spindle length.

John
Thanks for the confirmation. I was assuming it would based on what I'm looking at.

I probably didn't need to do everything I'm doing to it, I think I could have got by with a new front derailleur and a chain but usually when I overhaul one of these old bikes, I just do it all. The parts are cheap enough because I tend to stay between Altus and Alivio or Deore or comperable microshift or sram stuff. I'm not against Tektro brakes and the like either. It rarely costs me more than $150 to $200 to make pretty much everything new. Not great but new. I don't do any riding that requires anything more and I usually don't have the bikes long enough to wear anything out. I've managed to sell a couple and about break even, maybe put $20 to $50 in my pocket but I'm in Denver, CO. and there's a huge problem here with homeless people stealing bikes. I am from Maine originally and only ever had one bike stolen in the 40+ years I lived there. I've been here almost 10 years now and have had 4 of them stolen. 2 were locked up here where I live, 1st time they cut the cable so I bought a better cable and they cut the lock. Not sure how homeless people can afford high grade cutters but thats the story. The other 2 were taken from a "secure" job site and a light rail train station while I was working. So I bought wall mount hooks and keep them in my apartment now and they don't leave my sight when I'm out. There are no consequences for the thieves to worry about so it goes on unchecked. I have a strategy that would put things back into perspective but so far nobody else thginks it's a good idea. I remember reading somewhere that there was a time when thieves would lose things that were valuable to them, such as fingers and hands but I guess those methods are outdated.
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Old 08-26-22, 11:52 PM
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Ok, so I installed the 73 x 122.5 bb and now everything is off to the right, worse than it was to the left with the 73 x 113. I am looking at other options but so far all I'm able to find is a 73 x 118 octa-link which would require me to buy another chainring set. I think it shifted better with the 113 spaced over to the right but I don't know how well that would hold up in the long run because I couldn't get the left bb piece in far enough to snug up onto the main bb piece that goes through from the right (drive side). I don't think this 122.5 bb is going to work at all. I can't get the front derailleur to go out far enough to line up with the outer chain ring, not even close with the high limit screw all the way out.
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Old 08-27-22, 07:30 PM
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So I'm seeing as low as 107mm, which I know won't work because it's shorter than the 113mm that was too far in toward the bike frame. I unscrewed the drive side a few mm and got it to line up and shift normally but I didn't like the install because the non drive side "guide" part of the bb wouldn't thread through far enough to snug tight with the shaft/bearing part of the bb. So I ordered the 122.5mm bb based on info from here, my own observations, and with the advise of the bike shop where I buy my parts but this one is way too far to the right, so much so that the front derailleur will barely engage the low chain ring with the low limit set all the way in and it won't even consider moving out far enough to engage the outer chainring with the high limit screw actually removed. I know I didn't need to remove it, I just couldn't see when the arm stopped where the end of the screw was and a couple of turns later just to be sure, out it came. So I'm racking my brain here trying to figure out which bb I need to make this crank set work, or whether to just bin this mess and start over with a different crank set. I do a lot with older bikes so I'm sure that eventually I can find a use for these 2 bb and this crank set but that's definitely not ideal as I am not made of money and I still have to get a bb and crank set that will work and I don't have proper tools for measuring exact chain line measurements. I know for certain that the frame where the bb goes is 73mm. I don't have fance calipers but it's easy to access and I do know how to use a ruler. It's a nice SS machinest's ruler by Starette so it is accurate. I am also 100% positive that the bb I removed is a 73 x 113 because it says it right on it. I already have 2 bb sitting here and am not into collecting them so with the options I am looking at, ruling out anything 113 and below and anything above 122.5, it loos like Shimano offers 115, 116, 118, 120, & 121. I believe I also saw a couple of half sizes and other brands that offer even more so it looks like I'm down to .5mm increments of anything between 114 and 121. That leaves me quite a few options and at $15 to $25 a piece... Ummm, no. So does anybody have a sure fire way to check chain line measurements and how to figure it into how it works with the crankset? Before I go down this road of half mm trial and error to find which bb is the right fit. I did some looking around but just got frustrated. Well actually already was frustrated so my attention span for trying to figure that out from what seems like gibberish to me right now. just isn't there. I have this bike all done besides this and I just want to go ride it. The shop is booked out 2 weeks or more for service appointments and I don't really have the money for their rates anyway.
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Old 08-27-22, 08:27 PM
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Read most of this but may have missed something.

What is the chainline that you are getting with the 122 BB? Shimano MTB cranks usually have a chainline of 47.5-50mm, 45mm for older cranks sometimes.

What front derailleur are you using? Most Shimano FD can handle a 50mm chainline, even older ones.

What brand/model is your 113 BB? Cartridge type? Most cartridge BB have similar measurements across brands. A few mm max. difference is common, but not much. Wondering if your 113 is odd.
The right side difference between common 113 & 122 is usually about 4mm, 1/2 of the difference in total length, assuming a symmetrical, or close to it BB.

Attached is Tange specs, minor difference from Shimano but close.
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Old 08-27-22, 08:35 PM
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Something you might consider, either as a permanent solution or just to get riding for now, is to set up a 2x9 - then you don't need to reach the outer chainring position.

Also, if only using the inner two positions, you can use shims to move your chainrings to the left if necessary. I've done that - using mounting tabs cut from an old aluminum chainring - which were 5mm thick - and M10 spring washers from Home Depot - they fit nicely around chainring bolts, & are 2.3mm thick. Unfortunately you can't do that with all 3 rings, because shims would move the outer ring to the right.
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Old 08-28-22, 12:07 AM
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Originally Posted by KCT1986 View Post
Read most of this but may have missed something.

What is the chainline that you are getting with the 122 BB? Shimano MTB cranks usually have a chainline of 47.5-50mm, 45mm for older cranks sometimes.

What front derailleur are you using? Most Shimano FD can handle a 50mm chainline, even older ones.

What brand/model is your 113 BB? Cartridge type? Most cartridge BB have similar measurements across brands. A few mm max. difference is common, but not much. Wondering if your 113 is odd.
The right side difference between common 113 & 122 is usually about 4mm, 1/2 of the difference in total length, assuming a symmetrical, or close to it BB.
I'm just over 50mm, 50.3

My FD is a Microshift Marvo 3 x 9 however I am changing that because I can't get to the limit adjustment screws because of the odd pivot system for the rear suspension. I ordered an Alivio 3100 which will be here on the 1st.

The BB is a standard BBUN300

I try to include photos but the image sizes are too big and I am not good at editing them yet but it will let me upload them to my members page so I will upload them there and then try to link them if that will help.
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Old 08-28-22, 07:03 AM
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Well, I may have found a "sweet s;pot" wkth the 113mm bb. Instead of seating it against the frame, I left it off a few mm, snugged the other side up to it and jogged back and forth with them until I got the crank/chainring inner plane just off the profile of the bb tube looking from the bottom of the bike. I flipped it upside down so that i could get a good look at what I was doing. Once that was set, I adjusted the FD so that the cage was centered above the low gear (smallest/inner) chainring with the clamp and cable loose using the low limit screw and holding it in place where I could reach it with a driver. I moved it into it's working position and set the high limit with a pair of needle nose pliers, set the cable and installed a new chain. It goes through the gears ok on the stand. Going to take it out for a test ride here in as few to see how it does on the trail.
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Old 08-28-22, 07:23 AM
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If this bottom bracket setup works out, Id suggest using a spacer to fill the gap on the drive side between the BB and shell so you can torque the cup and not have it come loose while riding.
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Old 08-28-22, 07:37 AM
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I don't quite follow your process, but it sounds like the BB is loose in the shell, held only by the NDS lock ring. If so, don't ride it that way. You may damage the shell threads. It's probably okay to try a 1 or 2 mm spacer on the drive side for a permanent fix, but better to get a longer BB.

If you can get to a bike co-op, they'll have a bin full of salvaged cartridge BBs you can try out for very low cost. Bikes Together in Denver might be able to help out.

I volunteer at a non-profit shop in Golden and we often have to correct chainline problems, usually from poorly done crankset replacements. It's sometimes a juggling act between a pegboard full of cranksets and a bin full of bottom brackets, frustrating at times.
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Old 08-28-22, 03:18 PM
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Originally Posted by m0unt41n_d0 View Post
I'm just over 50mm, 50.3

My FD is a Microshift Marvo 3 x 9 however I am changing that because I can't get to the limit adjustment screws because of the odd pivot system for the rear suspension. I ordered an Alivio 3100 which will be here on the 1st.

The BB is a standard BBUN300

I try to include photos but the image sizes are too big and I am not good at editing them yet but it will let me upload them to my members page so I will upload them there and then try to link them if that will help.
https://cimg1.ibsrv.net/gimg/bikefor...9c28166b6d.jpg
https://www.bikeforums.net/g/picture/26172672
https://www.bikeforums.net/g/picture/26172673
Thanks for providing more info.

Saw in your later post that you seem to have figured out a couple of options.

Surprised that the Microshift can't handle a 50.3mm chainline. Most Shimano MTB FDs have throws that go out to mid 50mm, at least this is the case for bottom swing ones. Not sure about the top swing designs.
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Old 09-04-22, 01:54 AM
  #21  
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QUOTE=bboy314;22626731]If this bottom bracket setup works out, I’d suggest using a spacer to fill the gap on the drive side between the BB and shell so you can torque the cup and not have it come loose while riding.[/QUOTE]

I have put a spacer in there

andrewclaus it's not a process of mine, it's trying to get a crank set that isn't made to be a 3 x 9 that Wheat Ridge Cyclery sold me. I specified it was a 3 x 9 drive train that I was re-grouping. I have another bike to ride so I'm not riding it much, only to attempt to dial in the shifting. I have it working quite well after some trial and error.

The bb is not "loose" meaning there is no play or slop in it and it doesn't move. If you mean loose as in not tight to the frame, I have a lock ring that was on another bike on there as a spacer and it's tight to that. Basically what's happened is I got a crank set with a different offset than what was on there with the original 113mm shaft. I bought a 113mm bb to replace what came out as I wasn't aware of the fact that crank sets had different mounting "depths" or whatever that would be referred to as so I've had to shift the shaft position of the 113mm bb over a few mm to compensate for the difference in the crankset mounting position.

I tried a 122.5 which was way too long. I'm not sure exactly what length I need but it looks like it's quite a bit more than 1 or 2mm. The spacer I have on there looks to be about 5 or 6mm which would put me at about the 118mm shaft length IF the difference is only on the drive side. If it's not then I'm not understanding why the 122.5 threw things so far out.

Had they informed me that the M-371 3 x 9 specific crank set was only $20 more than this "hybrid" M-361 I probably would have let the 5mm crank arm length go for the proper fitting but I gave them my spending budget and specified that I wanted the 175mm crank arms so this was about my only option from what they had to go on. I just wish someone there could have picked up on this issue but then again, they are all about pushing the 1 x drivetrains now so I guess I have to forgive them for not thinking of the rest of us who still enjoy our 2 and 3 x or simply don't want to go that route for whatever reason. It's still cheaper to re-group a 3 x with a second derailleur and shifter than it is to buy a 1 x so that is an issue as well.

It sucks when the next new thing comes along and then everybody seems to forget about what most of the rest of the population is still using. A few yuppies with some money for 10 to 15 thousand dollar bikes are all of a sudden the focus of everyone's attention while 90% of the rest of the people are left on our own with our reasonably priced bikes, or in my case cheap af bikes because I simply don't have much money for anything other than my basic living expenses. I know that's my problem but there are a lot of other people who are in the same boat and if the math is done, overall, the little we do spend adds up to more than the yuppie sales, but nobody cares about that because it's not one big sale all at once. our money trickles in so it's insignificant.

Anyway, enough of my mindless ranting. I do thank you for the suggestions and advice. I may try one more time on my own with the 118mm bb because they are cheap enough at less than $20 and I am able to sell the parts I don't use on FB marketplace. That's where I pick up the bikes I buy and I've had good luck so far selling parts that haven't worked out. I can usually come close to breaking even because I can sell them as "like new" and get pretty close to what I paid so I'm not really losing a whole lot in the long run. I've even been lucky enough to get a few things on sale and sell them just a tad under current retail and put a few bucks back in my pocket so I guess overall I am kinda breaking even and learning a lot in the process, which is valuable in itself to me.

@KCT1936
Surprised that the Microshift can't handle a 50.3mm chainline. Most Shimano MTB FDs have throws that go out to mid 50mm, at least this is the case for bottom swing ones. Not sure about the top swing designs.
The Microshift derailleur is fine, the bolt for the clasp was too long and interfering with the travel mechanism. I put a shorter bolt in the clamp and it's fine now except that I can't get to the limit screws because of the way they are oriented and the rear suspension pivot design on this bike. The Shimano one is a front pull with the limit screws sideways on the drive side instead of on top with the top pull. The derailleur mounts underneath the pivot support and there's no way to get to them with a screwdriver and needle nose pliers just chew up the screw heads so that's the only reason I swapped. The Alivio eliminated that issue and it's better looking and matches the rest of the Shimano parts.
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Old 09-04-22, 09:24 PM
  #22  
KCT1986
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@KCT1936

The Microshift derailleur is fine, the bolt for the clasp was too long and interfering with the travel mechanism. I put a shorter bolt in the clamp and it's fine now except that I can't get to the limit screws because of the way they are oriented and the rear suspension pivot design on this bike. The Shimano one is a front pull with the limit screws sideways on the drive side instead of on top with the top pull. The derailleur mounts underneath the pivot support and there's no way to get to them with a screwdriver and needle nose pliers just chew up the screw heads so that's the only reason I swapped. The Alivio eliminated that issue and it's better looking and matches the rest of the Shimano parts.[/QUOTE]

OK, was just commenting based on your post that the MS FD wouldn't move out to the outer ring, even with high limit screw actually removed.

Glad you seem to have it sorted.
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Old 09-07-22, 09:22 PM
  #23  
m0unt41n_d0
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Bikes: 03' Iron Horse Sonic XS 3 x 8 hardtail, RockShox JudyTT, Shimano Acera group, 13' Iron Horse Maverick 4.5 3 x 9 FS, RockShox Dart II, Shimano Alivio group, 9?' Trek 950 Singletrack, single speed freewheel

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Originally Posted by KCT1986 View Post
@KCT1936

The Microshift derailleur is fine, the bolt for the clasp was too long and interfering with the travel mechanism. I put a shorter bolt in the clamp and it's fine now except that I can't get to the limit screws because of the way they are oriented and the rear suspension pivot design on this bike. The Shimano one is a front pull with the limit screws sideways on the drive side instead of on top with the top pull. The derailleur mounts underneath the pivot support and there's no way to get to them with a screwdriver and needle nose pliers just chew up the screw heads so that's the only reason I swapped. The Alivio eliminated that issue and it's better looking and matches the rest of the Shimano parts.
OK, was just commenting based on your post that the MS FD wouldn't move out to the outer ring, even with high limit screw actually removed.

Glad you seem to have it sorted.[/QUOTE]
I couldn't push it out far enough because the bolt that tightens the clamp was touching the mechanism that moves the derailleur. I didn't figure it out right away until I was trying to adjust the shifts and it wasn't retracting right. I have the larger of the
3 seat post sizes so there was no need for a spacer so I didn't think that should be an issue. It's possible I was over tightening. I do have a torque wrench but I didn't research the spec for that particular bolt. I know they need to be pretty tight because of the force they have to withstand from the spring tension when shifting to the larger chain rings and I've been doing mechanical work all my life on bikes, vehicles, machinery, etc so I'm petty good at hand torquing because I know things need to be tight enough for their intended purpose and I spent a good bit of time fixing snapped hardware when I was younger but I haven't (knock on wood) snapped any in years. It doesn't look like the clamp or frame of the derailleur are bent so I'm not sure why it was like that. I'm
sure I had the right size because I tried to install it with the next size adapter and it was definitely a no go. I wonder if anyone else who bought these derailleur had the same issue. I would assume that Microshift would know what size hardware to use but who knows. I've always been told to never assume anything lol.
Anyway I have it for a spare it's not really worth selling because it was only $16 to begin with and I've chewed up the back of the mechanism and both limit screws. There's really nothing wrong with it and if I find someone who can use it I'll donate it. I like The Alivio derailleur and everything else besides the brake levers are Shimano. It's been a learning experience for sure. I think this is one of the bikes that was sold off after Iron Horse went belly up by whoever took over and sold the remaining stock of frames that was left. It's an odd duck from my experience with mountain bikes. My older hard tail is pretty standard, much easier to work with but I haven't had many FS bikes so that's a learning curve of its own I suppose.
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