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When you widen the rear dropout, do you need to change the bottom bracket spindle?

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When you widen the rear dropout, do you need to change the bottom bracket spindle?

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Old 10-11-18, 01:18 PM
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When you widen the rear dropout, do you need to change the bottom bracket spindle?

OK, I framed this question a different way and did not get a response, so I will reframe the question: If you have a older frame with 120mm dropouts and you widen to 126mm, would you need get a wider bottom bracket spindle? It seem to follow that you would, if so how much longer should it be? 6mm? 3mm? That is the question. Any help would be appreciated. Thanks in advance!



The background is that I have an old Botteccia frame that has been widened from 120mm to 126mm, at least I believe so since it is an early 70's frame. I purchased an old Campy NR triple crank, also from the early 70's. If I look at an early 70's catalog, the recommended spindle length is 118mm on a frame with an Italian bottom bracket shell. At the time I believe 120mm rear dropouts were the norm, but I don't know if I want the 118mm bottom bracket spindle or something wider to account for the widening to 126mm, A 118mm Campy spindle appears to be an allusive animal.
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Old 10-11-18, 01:53 PM
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Originally Posted by crandress View Post
OK, I framed this question a different way and did not get a response, so I will reframe the question: If you have a older frame with 120mm dropouts and you widen to 126mm, would you need get a wider bottom bracket spindle? It seem to follow that you would, if so how much longer should it be? 6mm? 3mm? That is the question. Any help would be appreciated. Thanks in advance!



The background is that I have an old Botteccia frame that has been widened from 120mm to 126mm, at least I believe so since it is an early 70's frame. I purchased an old Campy NR triple crank, also from the early 70's. If I look at an early 70's catalog, the recommended spindle length is 118mm on a frame with an Italian bottom bracket shell. At the time I believe 120mm rear dropouts were the norm, but I don't know if I want the 118mm bottom bracket spindle or something wider to account for the widening to 126mm, A 118mm Campy spindle appears to be an allusive animal.
The short answer is no.
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Old 10-11-18, 02:01 PM
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...I know this isn't what you want to hear, but in order to get an optimal result you'll probably have to dry fit something and see where it ends up in terms of chainline. Whatever wheel/freewheel combination you choose can move in and out some, and certainly fitting a Campy triple to this frame compounds your dilemma by having the interior ring pretty close to the stays.

So probably not, but without mocking up something in a certain spindle length, and then evaluating where the chainline sits, I personally would not be able to do this.
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Old 10-11-18, 02:02 PM
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Originally Posted by Salamandrine View Post
The short answer is no.
Fair enough, so I look for a 118mm Campy (or other ISO) spindle then. Thank you sir1
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Old 10-11-18, 02:08 PM
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Originally Posted by 3alarmer View Post
...I know this isn't what you want to hear, but in order to get an optimal result you'll probably have to dry fit something and see where it ends up in terms of chainline. Whatever wheel/freewheel combination you choose can move in and out some, and certainly fitting a Campy triple to this frame compounds your dilemma by having the interior ring pretty close to the stays.

So probably not, but without mocking up something in a certain spindle length, and then evaluating where the chainline sits, I personally would not be able to do this.
Yes, I would check this out after. Just want to make sure if I have to spend up for a bottom bracket I have it close. Want to make sure I am not missing anything.
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Old 10-12-18, 08:17 AM
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Old 10-12-18, 08:21 AM
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If you took care to widen the spacing symmetrically, nothing need change at the bottom bracket. You should re-align the dropout faces to be parallel after changing the spacing. But a triple crank will need a longer spindle than a double crank, so if your current spindle is sized for a double, you'll need a longer spindle. The official Campagnolo trimple spindle will be marked "X3" but you may be able to find a compatible 3rd-party spindle instead.

http://www.os2.dhs.org/~john/campy-BB-specs.pdf

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Old 10-12-18, 08:50 AM
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If initially you had little clearance between the inner chainring and the chain stay, widening the dropouts could lead to needing a longer spindle or smaller inner chainring. My Medici got pretty tight but I'm still using stock parts.
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Old 10-12-18, 08:55 AM
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Originally Posted by JohnDThompson View Post
If you took care to widen the spacing symmetrically, nothing need change at the bottom bracket. You should re-align the dropout faces to be parallel after changing the spacing. But a triple crank will need a longer spindle than a double crank, so if your current spindle is sized for a double, you'll need a longer spindle. The official Campagnolo trimple spindle will be marked "X3" but you may be able to find a compatible 3rd-party spindle instead.

http://www.os2.dhs.org/~john/campy-BB-specs.pdf
Weill I did not widen the rear myself. Was already that way when I bought it. I was just going off the old Campy catalog to find the specs for the required bottom bracket for the triple. It then dawned on me that I did not know if I needed a longer spindle since the catalog specs would have been based on 120mm rear dropouts. But as everyone has chimed in, that does not appear to be the case. However I do appreciate the link. I had seen this before but could not find it in my last search. This is more specific, so I know what terms to search for. Thank you!
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Old 10-12-18, 08:56 AM
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Originally Posted by Bad Lag View Post
Phil
Not exactly sure why this was NOT top of mind. Good suggestion!
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Old 10-12-18, 09:03 AM
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^^^ For sure check your frame and dropout alignment. If it's crooked from a home frame reset, nothing's going to work right.

A properly reset frame is a non issue WRT BB spindle length. However, getting a proper spindle for that crank is a little tricky. That's what you need to worry about. Also you'll need old style thin cups. According to the charts in the article linked to above, the X3 campy spindle came originally in 118, and later in a 122 mm length. It may be hard to find any. Campy triples weren't ever common. I mostly remember them from bike boom era Paramounts. Also keep in mind that these were ISO tapers, more or less. You could conceivably use a JIS BB, but it will require a shorter spindle, and possibly a few dry fits.

A better solution is to get the correct BB from Phil. They make the correct BB with the correct taper. Plus there's no maintenance required, and an infinitely adjustable chainline. Costs money, but better than buying 2 or 3 or more BB's before you find one that fits.

This is the kind of thing that I would have recommended taking your bike to an LBS for in the past. If you have a vintage capable shop in your area, maybe still the best option.
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Old 10-12-18, 12:44 PM
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Originally Posted by crandress View Post
Weill I did not widen the rear myself. Was already that way when I bought it.
If you're not certain about how the re-spacing was accomplished, it may be prudent to check the rear triangle alignment with the "string test," as described in Sheldon Brown's article on frame spacing:

https://www.sheldonbrown.com/frame-spacing.html
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Old 10-12-18, 01:04 PM
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Q?

Wider rear dropout .. spacers, added to left side of hub ,

moves the gear cluster X amount to the right..

Is X significant to you?
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Old 10-12-18, 09:57 PM
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I would first "dry-fit" this setup with a 118mm JIS cartridge, which is symmetrical.

Then, if the chainring hits the chainstay, I would add a fixed-cup spacer, which will restore some of the asymmetry of the original setup while likely allowing the chainrings to clear the seatstay.

It's really handy to keep a few worn-out old cartridge bb's around for test fits, since even one such bb can generate measurements that will be enough to confirm what the best bb is for this bike.

My goal would be to get the chainrings as close as possible to the chainstay without rubbing since triples usually suffer very poor chainline when using the full spread of cogs while in the big ring (how I prefer to ride).
Having both pedals equally spaced out from their respective chainstays is another thing I would try to achieve.
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Old 10-13-18, 07:07 AM
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Originally Posted by Bad Lag View Post
Phil
This.
My otherwise full NR Mirella came to be with a Phil BB and when adding a tripleizer I just cranked it 5mm outboard.

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Old 10-13-18, 07:23 AM
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Originally Posted by top506 View Post
This.
My otherwise full NR Mirella came to be with a Phil BB and when adding a tripleizer I just cranked it 5mm outboard.

Top
Can you really adjust the Phil bottom brackets that much? They don't seem to make a 118mm currently, but if I can get a 113 and adjust...
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Old 10-13-18, 09:14 AM
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Phil is showing a 120 ISO BB on their website. Must be available somewhere. Perhaps direct from Phil. Since the early campy 3X was 118, and the 'new style' was 122, it would seem that 120 ISO is the best and correct size. Might be worth asking them directly.

You can adjust them to pretty much wherever you want, but obviously if you offset the spindle, it will become increasingly asymmetrical.
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Old 10-13-18, 09:26 AM
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Put the chain on the "most middle" cog.
Stand behind the bike and look.
Does the chain seem to run parallel to the centerline of the bike?

Since I use my outer cogs more, I run a slightly longer spindle.
The real goal is to have the chain running "straight" as possible the majority of the time.
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Old 10-13-18, 10:10 AM
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Originally Posted by crandress View Post
Can you really adjust the Phil bottom brackets that much? They don't seem to make a 118mm currently, but if I can get a 113 and adjust...
Worked for me, but no promises.
YMMV.

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Old 10-13-18, 10:50 AM
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Originally Posted by Salamandrine View Post
The short answer is no.
+1.

If you do the math, spreading a bike from 120mm to 126mm widens each side by 3mm if you do it right. But by going from a 5-speed to 6-speed freewheel, you also widen the freewheel by about 5mm, 2mm of which goes "inward". So the crank stays pretty well centered with the freewheel, as long as you don't do anything.
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Old 10-13-18, 11:37 AM
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@crandress, there is a concept called the chain line. The chain line runs parallel to the center line of the bicycle frame.

https://www.sheldonbrown.com/chainline.html

If you widen your dropouts and your freewheel/cassette is moved further from the center line of the bicycle frame, then technically you need to increase the distance of the chainrings from the center line of the bicycle frame.

Is this critical to the bicycle and its performance? Probably not. The concept, when employed, minimizes the maximum bend in the chain between the front and rear gears. A similar concept is the concept of avoiding "cross chaining".
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Old 10-13-18, 01:06 PM
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Originally Posted by Hummer View Post
@crandress, there is a concept called the chain line. The chain line runs parallel to the center line of the bicycle frame.

https://www.sheldonbrown.com/chainline.html

If you widen your dropouts and your freewheel/cassette is moved further from the center line of the bicycle frame, then technically you need to increase the distance of the chainrings from the center line of the bicycle frame.

Is this critical to the bicycle and its performance? Probably not. The concept, when employed, minimizes the maximum bend in the chain between the front and rear gears. A similar concept is the concept of avoiding "cross chaining".
If all you did was widen the dropouts and leave the freewheel/cassette width the same (5-6 speeds), then the chain rings could be farther out, but seriously doubt there’s any reason to do that given the lateral flexibility of today’s chains.

But the wider dropouts happened because cassette widths/speed counts were widened, so there’s more cog width on both sides of an idealized straight chain.

I always set chainline for the chainrings’ distance from the seattube centerline using Sheldon’s suggested 43.5 mm for doubles, 45mm for triples, regardless of rear spacing. Those dimensions work with all the front derailleurs I’ve encountered, including my own bikes and all the 6-10 speed (rear) bikes rebuilt as a volunteer for the last 3.5 years at the Seattle bike non-profit (Bikeworks.org). When we encounter a front shift problem that isn’t a blown shifter, it’s just about always a crankset or BB that was replaced without consideration for chainline.

BTW, I just checked my wife’s relatively new custom Indy Fab that uses an Ultegra 2x11 drivetrain with external BB bearings and 135 rear dropouts (for the disc brake) - 43.5mm to the center of the rings.
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Old 10-13-18, 01:53 PM
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Originally Posted by Dfrost View Post

If all you did was widen the dropouts and leave the freewheel/cassette width the same (5-6 speeds), then the chain rings could be farther out, but seriously doubt there’s any reason to do that given the lateral flexibility of today’s chains.

But the wider dropouts happened because cassette widths/speed counts were widened, so there’s more cog width on both sides of an idealized straight chain.
I was making a technical point. If the original bicycle set up has the correct chain line and then you change the rear dropout, then there is a good chance that you have changed the chain line distance from the center line of the bicycle frame visa vi the rear gears.

Originally Posted by Dfrost View Post

I always set chainline for the chainrings’ distance from the seattube centerline using Sheldon’s suggested 43.5 mm for doubles, 45mm for triples, regardless of rear spacing. Those dimensions work with all the front derailleurs I’ve encountered, including my own bikes and all the 6-10 speed (rear) bikes rebuilt as a volunteer for the last 3.5 years at the Seattle bike non-profit (Bikeworks.org). When we encounter a front shift problem that isn’t a blown shifter, it’s just about always a crankset or BB that was replaced without consideration for chainline.
The chainline distance is not set by the the chainring distance alone. It also involves the gears on the rear wheel. This means that you may have a chainline that is not parallel to the center line of the bicycle frame, which is not the ideal. The chainline distance can be less than 43.5mm and greater than 45mm, and anything inbetween.
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