Chainline out by 5mm (hubgear) - too much or doesn't matter?

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Galactic
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Joined: 21 May 2022, 7:42am

Chainline out by 5mm (hubgear) - too much or doesn't matter?

Post by Galactic »

Long time lurker here, asking my first question - hello all!

My chainline is 5mm out, and I'm wondering whether this is worth remedying or ignoring.
Here's the set up:
  • Rohloff with splined carrier 8540s on old-style hub (55mm chain line)
  • Shimano Alfine crankset FC-S501 with single chainring (49.2mm chain line)
  • The chain ring is already on the outside of the spider
I don't have the know-how (or probably the tools) to add a spacer to the bottom bracket, but plan to add spacers to the chainring, which will add up to 2mm (my chainring bolts are a bit loose anyway, so would benefit from washers), reducing the offset to a mere 3mm. Can I use any old washers as spacers, or should I get specific chainring spacers (LBS is 30 miles away, seems silly to order 5 washers from the internet)?

Any feedback on whether I'm worrying unnecessarily over a 5mm (or 3mm with spacers) offset on my chainline?
Appreciate any thoughts!
cycle tramp
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Re: Chainline out by 5mm (hubgear) - too much or doesn't matter?

Post by cycle tramp »

Hello There,
Both SPA cycles and St John Street Cycles sale chain ring spacers (of varying widths) and chain ring bolt sleeves of varying widths.
Depending on the space between the crank spider and crank arm, I would be tempted to purchase some wider chain ring bolt sleeves to replace the narrower sleeves that you are using and some wide chain ring spacers to get as close to a perfect chain line as possible, by fitting the spacers between the chain ring and the crank spider. It's something I tried briefly when I had a 4 x 7 set up

..however that said when I set up my 3 speed hub bike, many years ago, I don't think I ever checked my chain line and the chain stayed on without issue.
Motorhead: god was never on your sidehttps://www.google.com/search?ie=UTF-8&client=m ... +your+side
slowster
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Re: Chainline out by 5mm (hubgear) - too much or doesn't matter?

Post by slowster »

Galactic wrote: 21 May 2022, 7:58am
  • Shimano Alfine crankset FC-S501 with single chainring (49.2mm chain line)
  • The chain ring is already on the outside of the spider
49.2mm is the chainline according to Shimano with the chainring mounted as standard on the inside of the spider (with the double chainguard). If you have fitted the chainring to the outside of the spider, then your chainline should be a lot more than 49.2mm, and possibly is very close to your desired 55mm.

https://bike.shimano.com/en-EU/product/ ... -S501.html

https://dassets.shimano.com/content/dam ... 1-3475.pdf

If you have not already done so, I suggest you measure the chainline of the chainring (half the diameter of the seat tube, measured using a caliper or using the frame specification dimension, e.g. 28.6mm/2 or 31.8mm/2, plus the distance from the seat tube to the chainring's teeth). I suggest you also check that the 6.5mm spacer (item 11 in the exploded diagram above) is fitted.
Jdsk
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Re: Chainline out by 5mm (hubgear) - too much or doesn't matter?

Post by Jdsk »

cycle tramp wrote: 21 May 2022, 9:01am Both SPA cycles and St John Street Cycles sale chain ring spacers (of varying widths) and chain ring bolt sleeves of varying widths.
Depending on the space between the crank spider and crank arm, I would be tempted to purchase some wider chain ring bolt sleeves to replace the narrower sleeves that you are using and some wide chain ring spacers to get as close to a perfect chain line as possible, by fitting the spacers between the chain ring and the crank spider.
Especially as you need to fix those loose chainring bolts asap anyway.

And I'd start with SJS.

Jonathan
PH
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Re: Chainline out by 5mm (hubgear) - too much or doesn't matter?

Post by PH »

Apart from the lose chanring bolts which need to be sorted, it isn't a problem. Rohloff say up to 1 degree off is fine and that's about 8mm depending on chainstay length. You can check for yourself - just look at the chain on the ring and sprocket, it shouldn't have the side plates in contact.
If you still feel it could be better there's several options as well as chainring spacers, though they'd be my first choice. How are you tensioning the chain? If it's with a tensioner you have some adjustment there. Or if it's a EBB you can run that slightly off center.
Mine are within 1mm, I think that used to be the Rohloff advice, or it just might be my own fussiness.

EDIT - Just to add that new Rohloff hubs come with chainring spacers, so it's an expected way to achieve the chainline.
rogerzilla
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Re: Chainline out by 5mm (hubgear) - too much or doesn't matter?

Post by rogerzilla »

5mm is too much. The sprocket and ring will wear on one side, and it will be noisier than necessary.

Frames are rarely perfectly straight, frequently 4mm off, so get a long straight edge rather than trying to calculate front and back chainline, and see how bad it is that way.

If it really is more than 1mm out, I would try to do something about it. HT2 cranks are hopeless for adjusting chainline as they are essentially fixed at about 50mm. It can more easily be addressed with a square taper crank and BB of suitable length. Some cheap singlespeed cranks give a 46mm chainline on a 103mm JIS BB. Use a readily-available 122.5mm BB and Bob's your uncle.

The root of the problem is that the rear chainline is extreme. For comparison, a traditional track sprocket sits at 42 5mm (Campagnolo).
rjb
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Re: Chainline out by 5mm (hubgear) - too much or doesn't matter?

Post by rjb »

If it's a standard bottom bracket you may be able to slip a couple of 2mm sturmey archer washers behind the fixed cup. :wink:
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
Galactic
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Re: Chainline out by 5mm (hubgear) - too much or doesn't matter?

Post by Galactic »

Thanks for all the speedy answers!
If you have fitted the chainring to the outside of the spider, then your chainline should be a lot more than 49.2mm
I measured the chainring line at 50mm using a ruler, so assumed that was pretty much what Shimano said should be 49.2mm.
I suggest you also check that the 6.5mm spacer (item 11 in the exploded diagram above) is fitted
The crankset doesn't have any guards on it and the spacer only applies to the double guard. There's no spacer, and I think my crankset must be older than the one you linked to.
Look at the chain on the ring and sprocket, it shouldn't have the side plates in contact.
The teeth on the chain ring and sprocket seem to be quite happy, not nudging the sides, although they do wander a little from front to back, showing the chain is at an angle. So perhaps not desperately urgent to sort out, but I know it's there, it'll bother me until I do find a solution (only noticed because I needed a new sprocket on the Rohloff - presumably I've been running an angled chain for the last 30,000 miles!)
How are you tensioning the chain?
Horizontal sliding dropouts (if that's what they're called), so there's nothing other than the chain ring and the sprocket in contact with the chain.
Get a long straight edge rather than trying to calculate front and back chainline, and see how bad it is that way.
That was a brain teaser - no straight edges to hold the straight edge against and compare the chain line to! I put a spirit measure against a couple of chain bolts (then another two to average it out) to see where the other end of the measure ended up. It looks like it's approx 5mm (spirit measure was too wide and the spokes were in the way, so had to extrapolate the last couple of inches).

All in all, it sounds like 5mm is worth worrying about, and the easiest solution seems to be spacers with extended chain bolts. My current bolts are m8/8.5 and are 1mm too long, the chainring is 2mm thick and if I use 5mm spacers then presumably I need to find some bolts and sleeves that are about 12 to 14.5mm long? Am I seeing that right, that the spacers slip over the bolts and sleeves?

Thanks for your help so far - it's got me a lot further!
rogerzilla
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Re: Chainline out by 5mm (hubgear) - too much or doesn't matter?

Post by rogerzilla »

You hold the straight edge flat against the chainring :wink:
Galactic
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Re: Chainline out by 5mm (hubgear) - too much or doesn't matter?

Post by Galactic »

The only flat bit of the chainring has the chain on it - the rest has bolts and sleeves and the spider making ruler-unfriendly bumps and humps :( But I think I managed it in the end, and the result married up to the theoretical mathematics ...
slowster
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Re: Chainline out by 5mm (hubgear) - too much or doesn't matter?

Post by slowster »

Galactic wrote: 21 May 2022, 1:33pm
I suggest you also check that the 6.5mm spacer (item 11 in the exploded diagram above) is fitted
The crankset doesn't have any guards on it and the spacer only applies to the double guard. There's no spacer, and I think my crankset must be older than the one you linked to.
Even though it seems that chainring spacers are likely to be the solution, I suggest you check/confirm exactly what chainset you have.

Because you quoted a chainline of 49.2mm, I took that to indicate that you had the double guard version of the FC-S501. I would expect the exploded diagram to be the correct one for your chainset. The previous model, FC-S400, was a 3 piece chainset requiring an Octalink bottom bracket - FC-S501 is a 2 piece chainset requiring a Hollowtech 2 bottom bracket.

If you have an FC-S400, you may be able to replace the existing Octalink bottom bracket with one which has a longer axle, in order to improve chainline.

If you have an FC-S501, it appears that the right hand crankset and spindle unit may be the same for the single and double guard versions. If so, it would appear that you could fit the 6.5mm spacer to improve chainline. The spacer is available from SJS:

https://www.sjscycles.co.uk/chainsets/s ... -1f9-1300/

To ffit the spacer you would need a torque wrench suitable for ~14Nm, and a hex key. The plastic bearing pre-load cap on the left hand crank only needs to be finger tight (to prevent the spindle moving from side to side), and does not need a special tool.
Galactic
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Re: Chainline out by 5mm (hubgear) - too much or doesn't matter?

Post by Galactic »

Ok, you make that sound a lot less scary than was in my head - I'm sure I could borrow a torque wrench from somewhere.

On the other hand, it sounds like I need to put in washers or spacers or shorter bolts anyway since my current chain ring bolts are a mm too long and wobble around (although they and the chain ring itself are just as tight as they were 5k ago, still, best not to tempt fate ...)
PH
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Re: Chainline out by 5mm (hubgear) - too much or doesn't matter?

Post by PH »

rogerzilla wrote: 21 May 2022, 11:57am 5mm is too much. The sprocket and ring will wear on one side, and it will be noisier than necessary.
As already posted - Rohloff say otherwise "This is technically is harmless and unproblematic for the function."
https://www.rohloff.de/en/service/handb ... y/crankset
rogerzilla
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Re: Chainline out by 5mm (hubgear) - too much or doesn't matter?

Post by rogerzilla »

The sprocket and ring will still wear on one side and it will still increase noise. Rohloff can't change the laws of physics. It will work, but if you have a £1200 hub then you might as well get the basics right!
PH
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Re: Chainline out by 5mm (hubgear) - too much or doesn't matter?

Post by PH »

rogerzilla wrote: 21 May 2022, 4:10pm The sprocket and ring will still wear on one side and it will still increase noise. Rohloff can't change the laws of physics. It will work, but if you have a £1200 hub then you might as well get the basics right!
Well on the one hand we have the hub manufacturer, who before that were manufacturers of premium chains, and on the other some forum expertise. People can make their own mind up, but the OP has done thousands of miles without noticing which ought to be a clue.
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