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Nervar Bottom Bracket Question....

Old 08-14-14, 07:53 AM
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Nervar Bottom Bracket Question....

I am using a Nervar crankset (50.4 BCD) not sure of the model number in a frame spaced 126mm. I hThe crankset came with a spindle (no cups) maked 118mm. I know that there is the ISO vs. JIS taper issue so I was using a 122mm cartridge bb and in 7th gear, the driveside crank arem is hitting the chain. It touches just a bit as the crank come around.

I checked the wheel dish with the Park dishing guage and it seems good. Has anyone ever had a bent crank arm? Any other things I should be looking for?
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Old 08-14-14, 08:19 AM
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the first thing to check in these situations is the chainline. sight from the back of drive side along the cogs and chainwheels. in a 7v setup the middle cog should line up right between the c/w's.

this will tell you if a change is warranted in either direction.
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Old 08-14-14, 08:22 AM
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Edit: Juvela is correct. It would be very helpful to do "before-and-after" driveline alignment checks. The crainrings must have moved inboard with respect to the cogs.

A bent crank is possible, but I think you would notice the resulting once-per-revolution pedal wobble. I suspect the cartridge makes your drive side crank sit a bit farther inboard, which you might be able to resolve by shimming the cartridge where it screws into the BB shell.

If you have a "pie plate" spoke protector or other shim on the freewheel, removing that will move your cogs inboard without affecting your wheel dish.

If neither of these suggestions helps, your only other options are to live with it, to add a washer to the drive side of the rear axle (and redish as necessary), or to get a longer BB spindle or one with a different taper.
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Old 08-14-14, 09:21 AM
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This is the weirdest thing I've heard in a while, the crankarm hitting the chain!

It makes me wonder if the chainstays are perhaps offset toward the drive side, or if the two chainrings are perhaps both bolted to the driveside of the crankarm tabs.

As John E. says, a bent crankarm would manifest itself as a severe pedal wobbling.

Even weirder, since the JIS 122mm bottom bracket would certainly position the driveside crankarm further toward the driveside than would the original bb.
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Old 08-14-14, 09:32 AM
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Or, the high gear cog is too close to the inner chain stay. There is a minimum clearance one has to be at. I tried a 7 speed freewheel on the P13 Paramount and had the same thing happen. The crank arm just barely rubs the chain in high gear. So, I put the 6 speed freewheel back on, problem solved.
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Old 08-14-14, 05:26 PM
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Originally Posted by Michael Angelo
Or, the high gear cog is too close to the inner chain stay. There is a minimum clearance one has to be at. I tried a 7 speed freewheel on the P13 Paramount and had the same thing happen. The crank arm just barely rubs the chain in high gear. So, I put the 6 speed freewheel back on, problem solved.
This. I swapped in a 6 speed freewheel and the problem went away. Thanks!
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Old 08-14-14, 05:35 PM
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Originally Posted by fender1
I checked the wheel dish with the Park dishing guage and it seems good. Has anyone ever had a bent crank arm? Any other things I should be looking for?
Good to see you fix it (though at the expense of that 7th cog). But FWIW wheel dish would have nothing to do with it. The hub position won't change if the wheel is re-dished.

Who needs a 7th cog anyway?
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Old 08-14-14, 06:46 PM
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Originally Posted by jimmuller
Good to see you fix it (though at the expense of that 7th cog). But FWIW wheel dish would have nothing to do with it. The hub position won't change if the wheel is re-dished.

Who needs a 7th cog anyway?
Yeah, I need to stop being such a baby and HTFU when it come to gearing!
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Old 08-14-14, 07:05 PM
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Has anyone ever had a bent crank arm?
Yup, on this old Peugeot PE41 roadster...





Just the crank arm was damaged. Everything else was bang on straight.
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Old 08-14-14, 07:39 PM
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Is it this crank? This is on the Schwinn Superior I'm restoring. For what it's worth, this one is bent inward a bit. Also, I bent the right crank on my original Superior many years ago. It seems the zee French cranks, zey are made of cheese...

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Old 08-14-14, 07:40 PM
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Originally Posted by fender1
Yeah, I need to stop being such a baby and HTFU when it come to gearing!
Actually, what you're describing would mean you could not use the outer cog. Spin, baby, spin.
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Old 08-14-14, 07:42 PM
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Originally Posted by Jeff Wills
Actually, what you're describing would mean you could not use the outer cog. Spin, baby, spin.
Maybe but now I can try the shorter BB and try get the large cog usable....heres to hoping!
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Old 08-15-14, 08:02 AM
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Originally Posted by randyjawa
Yup, on this old Peugeot PE41 roadster...





Just the crank arm was damaged. Everything else was bang on straight.
Wow!
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Old 08-15-14, 08:02 AM
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Anyone got an Ultra 7 freewheel I try>? I have stuff to trade....
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Old 08-15-14, 08:33 AM
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Originally Posted by fender1
Anyone got an Ultra 7 freewheel I try>? I have stuff to trade....
I believe all 7-speed freewheels already have "ultra" spacing.
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Old 08-15-14, 08:53 AM
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FWIW, the Sronglight 93 on my Le Champiion used a 118 spindle.
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