misaligned bottom bracket? NOW MEASURED

[Lewis Moon]

I finally decided to build up the State Warhawk SSCX. The seller gave me an allowance to get it repaired and everything was going swimmingly until I popped in the BB and crank. I'm using a Rival road crank and, when it is fitted and torqued, the drive side crank arm hits the chainstay pretty badly while the NDS crank arm is about 5 mm out. I understand some builders really want you to use MTB cranks for clearance (like Kelly) but the fact that the BB may be that far off kind of bugs me. I did the "string test" and the alignment is spot on, the BB is 68 mm and the rear spacing is 130 mm, so I really think the BB is tweaked. I can't think of anything that could help this...

[AngryScientist]

this is SSCX?

before you go buying anything, better make sure you have a decent idea of what chainline the frame needs, that'll wind up being just as big of an issue as the crank arm clearance. just something to keep in mind...

[oldpotatoe]

I finally decided to build up the State Warhawk SSCX. The seller gave me an allowance to get it repaired and everything was going swimmingly until I popped in the BB and crank. I'm using a Rival road crank and, when it is fitted and torqued, the drive side crank arm hits the chainstay pretty badly while the NDS crank arm is about 5 mm out. I understand some builders really want you to use MTB cranks for clearance (like Kelly) but the fact that the BB may be that far off kind of bugs me. I did the "string test" and the alignment is spot on, the BB is 68 mm and the rear spacing is 130 mm, so I really think the BB is tweaked. I can't think of anything that could help this...

threaded BB road crank, yes? Those BBs come with spacers..maybe swap to other(DS) side? See note 2.

[Lewis Moon]

this is SSCX?

before you go buying anything, better make sure you have a decent idea of what chainline the frame needs, that'll wind up being just as big of an issue as the crank arm clearance. just something to keep in mind...

Chainline isn't the real issue. I can deal with that. I'm using a 10sp freehub with spacers so I can put the cog basically anywhere. I just can't get my head around the idea that; when the BB and crank are properly installed and torqued, that one crank arm would be +- 7 mm farther out than the other at the pedal. I might even understand if it were the drive side (chainring clearance and all) but it's the NDS. I'll get a straight edge on the BB tonight to see if it really IS misaligned.

[Lewis Moon]

threaded BB road crank, yes? Those BBs come with spacers..maybe swap to other(DS) side?

I put a 2 - 2.5 mm spacer on the drive side and the crankarm still hit the chainstay. Also, when I torqued it with the spacer, the BB bearings started to bind. I'm OK (but disappointed) with the idea that a road crank won't fit. I feel "cowboyed out" on MTB cranks but I have a couple of sets of MTB cranks that can go on. I just can't think of anything other than a misaligned BB that would cause this. Do any of you know if the Rival cranks have LESS clearance on the drive side?

[oldpotatoe]

I put a 2 - 2.5 mm spacer on the drive side and the crankarm still hit the chainstay. Also, when I torqued it with the spacer, the BB bearings started to bind. I'm OK (but disappointed) with the idea that a road crank won't fit. I feel "cowboyed out" on MTB cranks but I have a couple of sets of MTB cranks that can go on. I just can't think of anything other than a misaligned BB that would cause this. Do any of you know if the Rival cranks have LESS clearance on the drive side?

No...68mm shell? Accurate at 68mm? Binding is mysterious, with the supplied spacers.

[tctyres]

Did you email State to see if the crankset is compatible? On some CX bikes, road cranks are off-limits, as you noted.

[Lewis Moon]

Let's table this for the time being. I'll tear it down this evening and get a mic and some straight edges on it to see if the BB is within specs and aligned.

[Lewis Moon]

threaded BB road crank, yes? Those BBs come with spacers..maybe swap to other(DS) side? See note 2.

Hey OP: where did you find those instructions? I just looked on SPAM's website and I didn't see a mention of spacers. GXP Instructions (https://sram-cdn-pull-zone-gsdesign.netdna-ssl.com/cdn/farfuture/FmnsINy3tPU8poCYzhHTpxpScqyrHnsRtDhp1BiiTOs/mtime:1372788144/sites/default/files/techdocs/RED%20Crank%20BB%20PRINT.pdf)

[Hindmost]

look at the logo in the upper left corner of the instructions. That will tell you if it is road or mountain bike GXP bottom bracket.

[oldpotatoe]

Hey OP: where did you find those instructions? I just looked on SPAM's website and I didn't see a mention of spacers. GXP Instructions (https://sram-cdn-pull-zone-gsdesign.netdna-ssl.com/cdn/farfuture/FmnsINy3tPU8poCYzhHTpxpScqyrHnsRtDhp1BiiTOs/mtime:1372788144/sites/default/files/techdocs/RED%20Crank%20BB%20PRINT.pdf)

Googled 'picture of GXP BB assembly instructions.'

[David Kirk]

Hey - try this.......

Take the BB out and place a straight edge against a face of the BB shell so that the other end of the straight edge is near the rear drops. Now measure from the ruler to the dropout face and make a note of that number.

Now flip it and check the other side the same way. This is NOT a super precise way of checking the rear end alignment but great as a rough indicator. If the BB is cocked in the frame it will show in a big way.

dave

[Lewis Moon]

Hey - try this.......

Take the BB out and place a straight edge against a face of the BB shell so that the other end of the straight edge is near the rear drops. Now measure from the ruler to the dropout face and make a note of that number.

Now flip it and check the other side the same way. This is NOT a super precise way of checking the rear end alignment but great as a rough indicator. If the BB is cocked in the frame it will show in a big way.

dave

That's exactly what I'm going to do when I get home. Also going to measure against seat tube to see if it's shorter on one side, although it would probably have to be visibly shorter to make a diff.

[David Kirk]

That's exactly what I'm going to do when I get home. Also going to measure against seat tube to see if it's shorter on one side, although it would probably have to be visibly shorter to make a diff.


You are right..........a mm or two shouldn't be a cause for serious alarm as the BB faces may have paint on them or the ruler might not be dead straight (few are) but if you do it carefully you should get a good feeling of what, if anything, is going on.

dave

[cmbicycles]

Sram (or Shimano, etc) only requires those 2.5mm spacers with Mtn cranks to take up the extra space between either 'e clamp' bb mounts, and/or the difference between 68/73 shells. They aren't used on 73mm shells or on road cranks afaik.

[Lewis Moon]

Sram (or Shimano, etc) only requires those 2.5mm spacers with Mtn cranks to take up the extra space between either 'e clamp' bb mounts, and/or the difference between 68/73 shells. They aren't used on 73mm shells or on road cranks afaik.

This was my assumption. Thus the side load binding when I put one in.

[Lewis Moon]

Well, got a straight edge on the BB. It's off by a bunch. If a straight edge is extended back from the plane of the BB face to the rear fork ends, the drive side is about 7 mm different than the NDS. Measuring the distance between the BB face and the seat tube, the drive side is about 3 mm closer.
So, there's the problem: the BB is off a lot.

I did the string test again and it's well within 1mm

Any suggestions?

[Black Dog]

This might even be a challenge on the alignment table if it is the bb that is off and not the rear triangle. Calling Dave or Doug...:help:

[weisan]

Lewis pal, the days of half measures are over, time to make the cut.
http://tapatalk.imageshack.com/v2/15/02/03/a2d0135ad1eb9f319133961ef6b4c26a.jpg

http://forums.thepaceline.net/showthread.php?t=162812

[David Kirk]

Just to state the obvious just in case it's only obvious to some......

Alignments should be based on the BB faces and everything should reference to them. This makes it so the plane the c-rings are in is parallel to the centerline plane of the frame.

It sounds like the frame you have is superficially straight......meaning that a string test from front to rear shows the head tube, seat tube, and rear drops to be centered on the same plane..........but.........the BB shell is cocked at some hard to determine angle. This is a tough one.

The real way to fix this may or may not be practical depending on the frame material and method of construction. In a perfect world the frame would have its BB faced to be sure they are parallel and concentric and then the frame would go on a real alignment plate.

Assuming the BB faces are good now (may not be a good assumption) when you put the frame on the plate you'd expect to see that the rear end is off to one side, the front end is off to the opposite side (allowing the string test to come out good) and the seat tube is off to one side. I'd be surprised to find the head tube being parallel to the seat tube and would expect to find some head tube twist (meaning that one end of the HT would be closer to the plate than the other - this causes one wheel to be tilted when the other wheel is straight up and down.

If the bike is steel or ti a good builder may be able to cold set it all and have everything come into the same plane........if the bike is aluminum life will be tougher and if it's carbon you can make some sweet wind chimes out of it.

I don't know anything about the bike or the material or the builder nor how or why you own it. Maybe there would be compelling reason to try to fix it. I personally would send it back to where it came from and start anew with something less compromised. The bike was made out of plane and this is hard to recover in a good way. If it was free and you know a good builder who you can take it to then it might be worth the risk of investing the time/money to fix it. But anyway you cut it it will take someone with a good touch to bring it into alignment and this will load of the frame so it isn't in a neutral state (one tube being held in a flexed position by the other tubes) and this usually shortens the life of a frame in a real way.

I hope that helps.

dave



Well, got a straight edge on the BB. It's off by a bunch. If a straight edge is extended back from the plane of the BB face to the rear fork ends, the drive side is about 7 mm different than the NDS. Measuring the distance between the BB face and the seat tube, the drive side is about 3 mm closer.
So, there's the problem: the BB is off a lot.

I did the string test again and it's well within 1mm

Any suggestions?

[cmbicycles]

I assume it's a 68mm shell? Maybe have it measured for better accuracy, then have half the distance it's off faced off the nds and put a spacer on the drive side to compensate?
Or go to a Phil wood square taper bb, since there is no shoulder on Phil cups you can position the bb closer to where you might need it. Maybe an asymmetric spindle would be an option as well, you can set the spindle off center a bit as well with some Phil bb's.

[pbarry]

Most likely, the seat tube was welded to the BB, then that assembly is loaded into a jig with the rest of the tubes and tacked.

If the BB/ST weld area was not tacked in a jig, or if was tacked on only one side, the weld will pull, and the BB won't end up square to the rear triangle. Another possibility, the ST assembly may not been firmly clamped into the frame jig--slightly twisted.

The plates are telling the truth, but I'd be interested in the measurements from the rear inside face of the D.O.s to the BB shell, on both sides.

[Lewis Moon]

https://lh6.googleusercontent.com/-91V1vNoSU9Q/VNFpGZraA6I/AAAAAAAABhg/5tkwVTFIp9I/w827-h553-no/P1030178.JPG

https://lh5.googleusercontent.com/-pBqBcK6tkRo/VNFpIELX2tI/AAAAAAAABho/XN_wd4H9rKY/w732-h553-no/P1030179.JPG

[unterhausen]

that doesn't look that bad for an inexpensive production bike -- unless I'm being fooled by the parallax

[gospastic]

When you put a wheel in, does it sit center of the seat tube when looking at the bike from behind?

[choke]

that doesn't look that bad for an inexpensive production bike -- unless I'm being fooled by the parallaxLook at where the end of the dropout is compared to the end of the ruler.

[Lewis Moon]

When you put a wheel in, does it sit center of the seat tube when looking at the bike from behind?

Yeah, because that's not what's wrong. The alignment is spot on, the bottom bracket is tweaked.

[Lewis Moon]

Look at where the end of the dropout is compared to the end of the ruler.

Sorry about the photos, it was hard doing it with only two hands.

[pbarry]

I'd be interested in the measurements from the rear inside face of the D.O.s to the BB shell, on both sides.

This ^ will tell the differential in the two sides of the BB, and whether or not there is enuf wall thickness to machine. Guessing that you are on the margins of being able to re-thread once the faces are made right.

Mavic made a great BB back when, adjustable side-to-side, and does not rely on threading for alignment. Might be your best option here. You'd need to get the BB faces machined parallel to the rear drop outs first, then the fun part: Find someone who has the Mavic chamfering tool.

[Lewis Moon]

This ^ will tell the differential in the two sides of the BB, and whether or not there is enuf wall thickness to machine. Guessing that you are on the margins of being able to re-thread once the faces are made right.

Mavic made a great BB back when, adjustable side-to-side, and does not rely on threading for alignment. Might be your best option here. You'd need to get the BB faces machined parallel to the rear drop outs first, then the fun part: Find someone who has the Mavic chamfering tool.

I sent an email to State and we'll see what they do. I'd rather not resort to "heroic measures" on this frame.

[Black Dog]

I sent an email to State and we'll see what they do. I'd rather not resort to "heroic measures" on this frame.

Heroic indeed! It sounds like you are going to need chains and a couple of bulldozers to pull this BB back into alignment.