Irremovable spacer on drive side square taper spindle?

[RecordAceFromNew]

Well, after a bit of fettling I've got it in to what appears to be a working state.

Previously I was only running one chain-ring in the outer position of a double chainset. As RAFN suggested, my chainset is most likely ISO which moved it out 4.5mm on the JIS bottom bracket (still haven't figured out what that spacer is for, but there seems to be enough taper interfacing with the crankset despite it).

To combat that I moved the chain-ring to the inner position on the chainset, putting it back to roughly the right chain line. The outer chain ring position is now useless as it's too far out, but that doesn't bother me too much. It seems to shift well from the testing I have done so far.

It's not the perfect solution, but as this is just my around-town bike, if it works I'll keep it. If it doesn't work I'll just replace the lot with a new JIS chainset and matching bottom bracket to get it over with.

As I speculated earlier, your new UN26 122.5mm BB is indeed asymmetric. It is 63mm drive side and 59.5mm non-drive side, which explains the presence of the spacer.

One way to guesstimate whether chainset is indeed ISO is to see how far the taper goes into the chainset, some useful example photos here e.g.

In your case if your chainset is ISO and if the original 121mm BB is indeed ISO and symmetric your UN26 should give you (63mm - 121mm/2 +4.5mm) i.e. roughly 7mm or so more chainline than you want.

Further IF the chainset is no different to modern ISO, and if the original 121mm BB is ISO and symmetric, I would expect a new Shimano JIS 110.5mm (sometimes marketed as 111mm) BB should give you practically exactly the same chainline and clearance as previous (+/- 1 or at most 2mm), since it is: a) practically symmetric, and b) nearly 9mm (i.e. 2 x 4.5mm) shorter than a symmetric 121mm ISO one. You can of course also try to hunt down a 121mm ISO BB, or indeed as you said change the whole lot to something that is self compatible and delivers the correct, desired chainline.

 

[HovR]

As I speculated earlier, your new UN26 122.5mm BB is indeed asymmetric. It is 63mm drive side and 59.5mm non-drive side, which explains the presence of the spacer.

When buying new sealed bottom brackets, how does one tell whether they are symmetric or asymmetric? The CRC page I bought the bottom bracket off gives no information. Without knowing this it seems like it's impossible to know whether you'll be getting the right chainline!

Further IF the chainset is no different to modern ISO, and if the original 121mm BB is ISO and symmetric, I would expect a new Shimano JIS 110.5mm (sometimes marketed as 111mm) BB should give you practically exactly the same chainline and clearance as previous (+/- 1 or at most 2mm), since it is: a) practically symmetric, and b) nearly 9mm (i.e. 2 x 4.5mm) shorter than a symmetric 121mm ISO one. You can of course also try to hunt down a 121mm ISO BB, or indeed as you said change the whole lot to something that is self compatible and delivers the correct, desired chainline.

Considering that the chainset isn't really worth keeping (obsolete BCD, ISO taper meaning more expensive/hard to find BB's, nothing really too special) I was thinking of replacing it in May with something like the Stronglight ST55 from Spa. Would the recommend 119mm BB length work fine on a multi (6 or 7) speed bike?

Thanks for the help!

 

[RecordAceFromNew]

I was thinking of replacing it in May with something like the Stronglight ST55 from Spa. Would the recommend 119mm BB length work fine on a multi (6 or 7) speed bike?

A 7 speed bike will have a rear chainline of approximately 43mm if the hub is 126mm or 130mm, but around 46mm if the hub is 135mm. A 6 speed with 120mm or 126mm hub will have a rear chainline of 42mm. What front chainline do you want?

Can never understand why Stronglight copy Shimano's BB spec but not exactly their spindle lengths (there is no Shimano 119mm BB), but a Shimano UNxx 118mm BB will give you a front chainline of 45mm with the 55 chainset.

 

[HovR]

A 7 speed bike will have a rear chainline of approximately 43mm if the hub is 126mm or 130mm, but around 46mm if the hub is 135mm. A 6 speed with 120mm or 126mm hub will have a rear chainline of 42mm. What front chainline do you want?

Can never understand why Stronglight copy Shimano's BB spec but not exactly their spindle lengths (there is no Shimano 119mm BB), but a Shimano UNxx 118mm BB will give you a front chainline of 45mm with the 55 chainset.

Finally getting around to ordering this.

The Peugeot has been re-spaced to 130mm at some point in it's life (and is running a 130mm threaded freewheel hub), but is still using the original 6 speed freewheel (although this could likely change to a Shimano 7 speed later on in the bikes life). Will the recommended 119mm Stronglight BB work well in these applications (running the chainset with a single chainring only)?

Cheers

 

[RecordAceFromNew]

Finally getting around to ordering this.

The Peugeot has been re-spaced to 130mm at some point in it's life (and is running a 130mm threaded freewheel hub), but is still using the original 6 speed freewheel (although this could likely change to a Shimano 7 speed later on in the bikes life). Will the recommended 119mm Stronglight BB work well in these applications (running the chainset with a single chainring only)?

Cheers

As I indicated earlier you should have a rear chainline of approximately 43mm, but given the original size/speed of the hub is uncertain you might want to do a rough check (centre of sprockets around 130mm/2 - 43mm or therefore 22mm from dropout). If you want to match that up front a Shimano UN series 115mm bb should get you close, but you could consider using e.g. a Shimano 118mm bb if you are going to be on the smaller sprockets most of the time. I have no idea what the Stronglight 119mm bb would give you - you might want to check with Spa for that.

 

[HovR]

As I indicated earlier you should have a rear chainline of approximately 43mm, but given the original size/speed of the hub is uncertain you might want to do a rough check (centre of sprockets around 130mm/2 - 43mm or therefore 22mm from dropout).

Just measured 42mm for the rear chainline, give a mm for lack of measuring accuracy, so 43mm sounds about right.

If you want to match that up front a Shimano UN series 115mm bb should get you close, but you could consider using e.g. a Shimano 118mm bb if you are going to be on the smaller sprockets most of the time. I have no idea what the Stronglight 119mm bb would give you - you might want to check with Spa for that.

As the ratios on my current freewheel are quite closely grouped I tend to use the whole range of them. Could the 115mm BB possibly bring the cranks in-board enough to interfere with the chainstays? It seems like quite a significant change down in size (compared to older cranks/BB's I've worked with anyway).

Probably going to get a UN55 this time, hopefully better quality than the UN2X range.

Edit: Should the bottom bracket needed to achieve a certain chainline be the same with any single ring square taper chainset? Just spotted this on CRC and love it!

 

[RecordAceFromNew]

As the ratios on my current freewheel are quite closely grouped I tend to use the whole range of them. Could the 115mm BB possibly bring the cranks in-board enough to interfere with the chainstays? It seems like quite a significant change down in size (compared to older cranks/BB's I've worked with anyway).

Probably going to get a UN55 this time, hopefully better quality than the UN2X range.

Edit: Should the bottom bracket needed to achieve a certain chainline be the same with any single ring square taper chainset? Just spotted this on CRC and love it!

Last question first - there is usually no consistency between different models, let alone different makes of chainsets for a certain bb length to achieve a certain chainline. For example according to CRC that FSA chainset requires a 110.5mm bb to deliver 45mm.

In case you wonder no current Shimano JIS bb I know of will deliver a lower chainline than that, because afaik the shortest they sell is 107mm, but it is just as long as their 110.5mm on the drive side.

While not light at around 300g a piece the UN5x are good and generally seem to outlast all these new-fangled contraptions...

I use a 115mm UN72 (hard to find these nowadays) with a Stronglight 55 and still have over 5mm clearance at the chainstay which is itself wrapped in a Lizard skin protector some 3mm thick. A Shimano 118mm JIS spindle is 2mm longer than a 115mm on the drive side.

That FSA chainset looks nice and reminds me of some 70's / early 80's Campag chainsets. Unlike the 55 it has replaceable rings and I would expect it to be more robust, but I would guess 150g or so heavier.

 

[e-rider]

fit a new BB without problematic spacer!

 

[HovR]

Last question first...

Thanks for your help RAFN, unfortunately I just noticed that the FSA chainset has no 170mm crank lengths in stock so I decided to go with the ST55 and a UN series 115mm BB upon your recommendation. It's all ordered now, hopefully when it arrives everything will go together with no issues!

fit a new BB without problematic spacer!

The original Nervar chainset was becoming slightly worn anyway, and as chainrings with the correct BCD are no longer in production I thought I'd take this opportunity to upgrade to something a bit newer.

 

[Smurfy]

Well, after a bit of fettling I've got it in to what appears to be a working state.

Previously I was only running one chain-ring in the outer position of a double chainset. As RAFN suggested, my chainset is most likely ISO which moved it out 4.5mm on the JIS bottom bracket (still haven't figured out what that spacer is for, but there seems to be enough taper interfacing with the crankset despite it).

To combat that I moved the chain-ring to the inner position on the chainset, putting it back to roughly the right chain line. The outer chain ring position is now useless as it's too far out, but that doesn't bother me too much. It seems to shift well from the testing I have done so far.

It's not the perfect solution, but as this is just my around-town bike, if it works I'll keep it. If it doesn't work I'll just replace the lot with a new JIS chainset and matching bottom bracket to get it over with.

Sheldon lists Nervar as ISO.

Best way to remove the spacer is to remove the BB, shield the bearings from dust with some tape, then grind/cut through the spacer. As soon as you have cut all the way through it the hoop stress will be zero (which is what gives the compression fit and all the friction holding it in place) and the spacer will slide off very easily.

 

[HovR]

I did consider grinding it off, but decided to go for the more hassle free option of just buying a new BB and chainset. I still have the BB with the spacer so I may end up doing that at some point in the future if I ever use it on a different bike.

The new chainset and bottom bracket arrived yesterday, and I fitted them today with no issues. Everything has gone together fine and the bike runs like it should again, cheers to all who helped!