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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 08-25-12, 10:30 PM   #1
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Skidded once on Sugino 75s, now it's making noises?

I'm currently running SG75s with SG75 chainring and an RPM BB7420 bottom bracket (I'm aware that that's the incorrect spindle length for SG75 cranks). Anyways I was riding and did a few skids and now my drive train is making a really bad noise. It's like some sort of crunching sound every pedal stroke, like the sound of a really bad chain line. I've ridden with this setup for a couple weeks and had no problems until I did a few skid stops yesterday.

So I took off my chain and spun the cranks. Judging by the chainring, the drive side crank is wobbling side to side (away and towards the frame). It's not the chainring, because I removed it and placed it flat on the ground and it didn't seem bent. I'll be pulling the crank off tomorrow to see if I'm f*ed, but right now I wanna know how this could have happened? I've skidded on $50 Vuelta Pista cranks with no problem for god's sake...
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Old 08-25-12, 10:37 PM   #2
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skidding has nothing to do with this. you probably set up your drivetrain wrong. chainline, spindle length, bolt torque, etc etc. The problem here isn't the cranks it's how you installed it. inspect the drivetrain everytime the crunching sound appears and check what seems to be out of line.
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Old 08-25-12, 10:47 PM   #3
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Sounds like a BB problem.

Not a lot of possibilities if it's a fixed gear bike and a crunching noise.
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Old 08-25-12, 10:48 PM   #4
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Must I get the correct size bottom bracket? I checked my chainline and it looks near perfect. Or is there something more to it...
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Old 08-25-12, 10:51 PM   #5
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I think what leuky mentioned is correct. you are using a different type of spindle rather than the length of the spindle.
this article should clarify: http://sheldonbrown.com/bbtaper.html
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Old 08-25-12, 10:53 PM   #6
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What did you check your chainline with? Are we talking about a tool, or just eye-balling it?

I could say I tightened my stem bolts so they look perfectly even, so it's not gonna have issues. But a torque wrench would be a much more accurate option.

And like Leukybear said, you gotta use a compatible BB with the cranks.
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Old 08-25-12, 11:10 PM   #7
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The thing is I rode it with no problems (and barely any sound) before, so maybe it was undertorqued? And Sheldon Brown says "I have a lot of experience mixing ISO/J.I.S. in both directions on my own personal bikes, and it as never given me a lick of trouble." and "In practice, you can very often get away with mixing these sizes, as long as you select a spindle length that gives the desired chainline."

I took a tape measure to my chainring/seat tube and my chainline is off by 3 mm. Measured from the center of the seat tube to a tooth and got 45 mm

Last edited by Reeses; 08-25-12 at 11:11 PM. Reason: more info
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Old 08-25-12, 11:19 PM   #8
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so maybe it was undertorqued?
you said it

wont know for sure until you use a torque wrench
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Old 08-26-12, 03:04 AM   #9
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I'm currently running SG75s with SG75 chainring and an RPM BB7420 bottom bracket (I'm aware that that's the incorrect spindle length for SG75 cranks).
Derp.
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Old 08-26-12, 04:25 AM   #10
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The thing is I rode it with no problems (and barely any sound) before, so maybe it was undertorqued? And Sheldon Brown says "I have a lot of experience mixing ISO/J.I.S. in both directions on my own personal bikes, and it as never given me a lick of trouble." and "In practice, you can very often get away with mixing these sizes, as long as you select a spindle length that gives the desired chainline."

I took a tape measure to my chainring/seat tube and my chainline is off by 3 mm. Measured from the center of the seat tube to a tooth and got 45 mm
Did Sheldon ever bust Mad skids like you did?
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Old 08-26-12, 04:37 AM   #11
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Did Sheldon ever bust Mad skids like you did?
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Old 08-26-12, 06:40 AM   #12
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Sounds like you didn't have the correct torque. Not a JIS/ISO issue.

Correct torque specs are all over the map for 75s. Despite what the quote says, I'd recommend something like 28-33 ft/lbs since you've already biffed them once.

Quote:
Dear Mr. --

Thank you very much for your e-mail.

The torque is 12-16N.m.
However, this torque specification is appropriate
under the condition that the SG75 cranks are used with the NJS parts.

We recommend to grease the BB spindle slightly
to prevent seizing and rust on the spindle.

We also recommend to do maintenance periodically.

Best regads,
Yuki Iwai
SUGINO CYCLE INDUSTRIES, LTD.
iwai@suginoltd.co.jp
TEL. +81-(0)742-62-5311
FAX.+81-(0)742-62-5320
287-1 Tohkujo-cho, Nara, Japan 630-8144
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Old 08-26-12, 04:31 PM   #13
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I removed the cranks and BB and reinstalled everything with sufficient torque but the chainring/crankarm still wobbles side to side.
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Old 08-26-12, 04:34 PM   #14
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Sounds like either the square taper interface is damaged or the BB is crap.
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Old 08-26-12, 05:06 PM   #15
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I removed the cranks and BB and reinstalled everything with sufficient torque but the chainring/crankarm still wobbles side to side.
still using the incorrect bb?
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Old 08-26-12, 06:00 PM   #16
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Old 08-26-12, 06:03 PM   #17
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Old 08-26-12, 06:40 PM   #18
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Currently I'm trying to work a stripped crankarm off of a Sugino 75 BB so I can use the correct size bottom bracket.
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Old 08-26-12, 06:45 PM   #19
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Timely topic.

I run a freewheel on my TimeLine, so no skid stops. I do ride over the local bridges and some hills in the area. I've been doing more and more hill rides lately. I don't stand and mash when I climb, but maybe the spate of climbing over the last three weeks has something to do with today's problem. I rode over the Brooklyn Bridge to the Greenway and up to 44th Street: No problems until, on the way back, this really annoying squeaking started coming from my bottom bracket. It sounded almost like shoes on a basketball court.

The crank arms and pedals look okay, so I'm guessing the BB needs to be lubed and torqued. Since I don't have a torque wrench, I'll take it up to the LBS this week.
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Old 08-26-12, 07:35 PM   #20
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Cool story bro.

For what it's worth, "mashing" is not standing up and pedaling like a rabid gorilla. To "mash" simply means to push a big gear ratio.
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Old 08-26-12, 09:55 PM   #21
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Cool story bro.

For what it's worth, "mashing" is not standing up and pedaling like a rabid gorilla. To "mash" simply means to push a big gear ratio.
Yup. Thanks for the reminder. To clarify, I do run the stock gearing, which is pretty big (46/15). What I meant to say was that while I do mash in the sense of the big gear, I climb seated. Sorry about the misuse of terms .

This actually belongs in the Ask Scrod thread (so, sorry again for the mis-post; please move at your discretion, Mr. Scrodmerator), but does this sound like a matter of lube the BB and re-torque it, or is it likely that my stock BB is toast? I've read elsewhere on the board that a few people have had issues with the BB on The Hour, which I believe is the same on the TimeLine.

"To stand up and pedal like a rabid gorilla, or to sit and spin like a gerbil on crack? That is the question..."
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Old 08-26-12, 10:05 PM   #22
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Great hijack. Lube the BB and re-torque it... Do you know what you are talking about?
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Old 08-27-12, 12:16 AM   #23
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He must mean grease the threads and install it to the right torc speques
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Old 08-27-12, 06:29 PM   #24
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He must mean grease the threads and install it to the right torc speques
Yup. Thanks. Sorry for the thread hijack.
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Old 08-28-12, 12:31 AM   #25
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Today I tried to separate the stripped SG75 crank from the SG75 bottom bracket - it did not go well. But in curiosity I attached the drive side SG75 I skid on a couple days ago onto the non drive side of the BB and put the chainring on it. I gave it a spin and the wobble was gone. I guess it was that cheap RPM BB that I trashed and not the crank arm, thank goodness.
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