Too close for comfort (chainring content)

[jemdet]

I have never had the pleasure of owning a 6400 crankset / BB, but I have owned the same in 7400. The 7400 cup and cone BSA BB was 113 mm JIS "low profile," which meant that a standard taper JIS BB needed to be longer. Once cartridge BBs came out, Shimano's own literature paired the 7400 crankset with a 115 mm BSA UN-91. This may also be true of the 6400. Not sure if it was just DA.

I had the same problem as you running the 7400 crankset with a newer 113 mm BB and a 42 inner chainring. If you are running a newer 113 mm BB because that's what the literature told you, try bumping it up to 115 mm.

[azrider]

Originally Posted by Mark McM

Yup, too close.



If the left crankarm is sitting further from the frame than the right, there might be possibility that you've gotten an asymetrical spindle in backwards.

Hmmmm.....if anything the L crank looks a little close also.

Which tells me too narrow BB

No?






Sent from my iPhone using Tapatalk

[azrider]

Originally Posted by zmudshark

113bb?

Sup Z, no clue what's in there currently as I bought it built up

Originally Posted by pinkshogun

and could you adjust the front derailer inboard enough for proper shifting?

Ha...funny you mention that. A buddy asked me same thing today and I told him "ya know.....come to think of it......I always did find it odd that I got a little rubbing on my lowest gearing combo

[Kontact]

What's the chainline? If the inner ring is 41mm from the frame midline, then it is the frame's fault.

If the inner ring is closer than 41mm, than something is wrong with the combination of parts, or the BB shell has been faced down too far.


There are lot's of fixes, but you ought to start by finding out where the problem lies.


The 6400 crank needs to be on a 113mm JIS (not ISO/Campy) spindle for an English BB, and 115 for Italian.

[AngryScientist]

there also appears to be a chainstay protector on the NDS chainstay and not one on the drive side. lol.

[zmudshark]

Doug, You need to measure the BB. Any idea what model is in there?

[Peter P.]

Originally Posted by FlashUNC

The real mystery is why that chainstay wasn't crimped to make room.

That's a valid option, but if it's a Serotta, I think it's safe to assume it was built properly and crimping the chainstay was not necessary nor part of the design. Many builders either ovalize the chainstay or use chainstays that are oval by nature.

Before purchasing a longer BB axle, I'm in the camp with the others, and I'd measure the chainline to verify the chainrings are not at the 43.5mm standard position from the centerline of the bottom bracket.

[ColonelJLloyd]

Originally Posted by AngryScientist

there also appears to be a chainstay protector on the NDS chainstay and not one on the drive side. lol.

Good stuff.

Originally Posted by azrider

Must be the photo because it looks like you've got a lot of space between the chain stay and NDS arm. Are you sure the spindle isn't asymmetrical and in backward?

[azrider]

Originally Posted by AngryScientist

there also appears to be a chainstay protector on the NDS chainstay and not one on the drive side. lol.

ha.....yeah it's there, it just extends further toward the bb. I put another around the nds to protect the lettering

[seanile]

Originally Posted by ColonelJLloyd

Are you sure the spindle isn't asymmetrical and in backward?

my thought as well if this is a loose-ball bb...which, by the looks of it, it is.

[azrider]

I'm not one to leave lose ends so just wanted to close this up.

With my travel/work schedule last week I had some time that i was going to be at home on Tuesday afternoon so instead of trying to figure out issue myself I opted to call "mobile mechanic" service that comes to your house and fixes your bike.

I emailed the mobile mechanic service, explained the issue with chain ring being too close to chain stay, and I was told "yeah, shouldn't be too difficult". Upon arriving, mechanic immediately looked at bike and started questioning what group was on there, and even asked "how old is that bike?".

He reluctantly took it to his van and after three hours said he was done. He even admitted that he had to "go online to figure out how to cable the group/frame" WTH ??

I asked how much i owed him and he said "well, i replaced the chain and cables so parts/labor is $100". What?! That sounds crazy but hey, if you say it's fixed then I'm willing to pay. I took it for a short ride around block and not only was it still shifting improperly (because the chain ring was STILL too close to chain stay and hence the FD was too close) but the chain ring was STILL too close to the frame. I argued that I didn't feel he did anything to fix what i had asked him to fix and he immediately wanted to offer refund.

What frustrates me even more, is that on the following weekend I took the bike to a shop 40 minutes away from my house to a guy who knows his sh*t and within seconds of looking at it determined, "ummmm.......yeah, you have wrong BB. You need something wider".

$20 and a shared 6 pack of beer while reminiscing old times and CSI is finally back to normal.

Thanks to those who helped.

Cheers.

[Kontact]

Originally Posted by azrider

I'm not one to leave lose ends so just wanted to close this up.

With my travel/work schedule last week I had some time that i was going to be at home on Tuesday afternoon so instead of trying to figure out issue myself I opted to call "mobile mechanic" service that comes to your house and fixes your bike.

I emailed the mobile mechanic service, explained the issue with chain ring being too close to chain stay, and I was told "yeah, shouldn't be too difficult". Upon arriving, mechanic immediately looked at bike and started questioning what group was on there, and even asked "how old is that bike?".

He reluctantly took it to his van and after three hours said he was done. He even admitted that he had to "go online to figure out how to cable the group/frame" WTH ??

I asked how much i owed him and he said "well, i replaced the chain and cables so parts/labor is $100". What?! That sounds crazy but hey, if you say it's fixed then I'm willing to pay. I took it for a short ride around block and not only was it still shifting improperly (because the chain ring was STILL too close to chain stay and hence the FD was too close) but the chain ring was STILL too close to the frame. I argued that I didn't feel he did anything to fix what i had asked him to fix and he immediately wanted to offer refund.

What frustrates me even more, is that on the following weekend I took the bike to a shop 40 minutes away from my house to a guy who knows his sh*t and within seconds of looking at it determined, "ummmm.......yeah, you have wrong BB. You need something wider".

$20 and a shared 6 pack of beer while reminiscing old times and CSI is finally back to normal.

Thanks to those who helped.

Cheers.

Would you mind saying what crank model/year this is and how long the old spindle was?

I'm curious if the BB was wrong or something else was.

[cnighbor1]

Reinstall BB Cups drive side with a spacer or two
What happens is that when under load frame of crankset can move a bit
And chain ring hits the frame many times
Or crankset get out of true see line above

[Peter P.]

What-no Before and After photos?!

What were the differences in dimensions between the BB's?

Inquiring bike geeks want to know.