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chainline 2x7 tourney

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chainline 2x7 tourney

Old 02-18-19, 09:52 AM
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chainline 2x7 tourney

ok so i just got this NOS Dawes Litning from Bikeilsand. i think sumting wrong with chainline.

btw, i have measured chainline on my single speed bikes...and i get numbers consistence with Sheldon Browns...~42mm...so i know how to accurately meausre chainline.

SheldonB web says dual chainring should havr 43.5 chainline. i measured my Dawes, and it is way off. wtf!

last nite...laying in bed...out of the blue...sumting in my head tells me go to meausure the chainline.
so i jumped out and grab the caliper...its measuerd...48mm on inner chainring...56mm on outer chainring. ... so mid is 52mm...so my bike is off by almost 10mm...how can my bike be off by so much???

what am i missing? is the Tourney different from other 2 ring setup?

sumting is really not rite!!! noone could have made a huge mistake like that?!

letme know before i order a shorter UN55 BB.

Last edited by mtb_addict; 02-18-19 at 10:10 AM.
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Old 02-18-19, 10:00 AM
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the chain is noisy...so maybe thats wha trigger my brain.
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Old 02-18-19, 10:10 AM
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While chain line is typically measured from the center of frame to the center of your front sprocket stack, the important thing about chain line is where it falls on the rear cassette. If you extend the centerline of your front gear stack to the rear gear stack, then it should hit somewhere near the middle. How much tolerance? Well that depends on the range of your derailler, chain flex and whether or not you'll hit your chainstays and stuff. All can be different for different makes of bikes, but bikes with similar bb's should have about the same chainline measurement.

If yours isn't causing issues, then why make yourself headaches?
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Old 02-18-19, 10:32 AM
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You know how to Measure the chainline?
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Old 02-18-19, 11:19 AM
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Originally Posted by mtb_addict View Post
...laying in bed...

There's the problem.



Originally Posted by mtb_addict View Post
what am i missing?
Ride time.
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Old 02-19-19, 09:28 AM
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Originally Posted by fietsbob View Post
You know how to Measure the chainline?
Yes. Double checked it again with the caliper.

Also did a visual check...indeed the chain looks very bent. Only when it is on the outer chainring and the outer rear cog at same time, does it look straight.

Now, I'm pretty sure the manufacturer used the wrong BB spindle length.

I suspect this is why the chain is noisier than my other bikes.

No big deal...I can get a Sunrace BB for $12...But check your chainline, people!

Last edited by mtb_addict; 02-19-19 at 09:31 AM.
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Old 02-19-19, 09:59 AM
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Chainline 101 parallel to bike center line

rear is middle of cog cluster (4 of 7, etc) front , middle of triple, or single or gap between 2, the spider..
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Old 02-19-19, 10:57 AM
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Originally Posted by mtb_addict View Post
Yes. Double checked it again with the caliper.

Also did a visual check...indeed the chain looks very bent. Only when it is on the outer chainring and the outer rear cog at same time, does it look straight.

Now, I'm pretty sure the manufacturer used the wrong BB spindle length.

I suspect this is why the chain is noisier than my other bikes.

No big deal...I can get a Sunrace BB for $12...But check your chainline, people!
Once again, you're complaining about a cheap bike not being a top-level bike.

Cheaper drivetrain parts tend toward a wider chainline, presumably to avoid crank/chainstay strike. (For example, note that while official track chainline is 42mm, many cheap "track/singlespeed" cranks have a 46mm chainline.)

They can get away with it because most people at that price point aren't going to notice.
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Old 02-19-19, 11:35 AM
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Originally Posted by ThermionicScott View Post
Cheaper drivetrain parts tend toward a wider chainline, presumably to avoid crank/chainstay strike. (For example, note that while official track chainline is 42mm, many cheap "track/singlespeed" cranks have a 46mm chainline.)

They can get away with it because most people at that price point aren't going to notice.
Okay...as soon as I get home...I'm check to make sure there's enough room on the chainstay.

Btw...I don't want peeple wrong idea I am unhappy...I'm luv'ing the bike so far. It is really fast, just like its name sake. Besides the chainline and the cheap tires...it's a great bike...I would call it mid-level quality bike.

Last edited by mtb_addict; 02-19-19 at 11:40 AM.
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Old 02-19-19, 02:31 PM
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Originally Posted by ThermionicScott View Post
Cheaper drivetrain parts tend toward a wider chainline, presumably to avoid crank/chainstay strike.
Okay...I just checked...plenty of clearance to use a shorter spindle. Like more than 10mm between the small chainring and chainstay.

Time to get a shorter BB. To meet the Shimano Spec below...the new BB spindle will have to be 20mm shorter. Wow that's extreme! And the small chainring will probably be very close to the chainstay.


https://sheldonbrown.com/chainline.html:
Shimano spec, measured to the midpoint between the rings.
with typical 5 mm chainring spacing, this puts the inner at 41 mm, the outer at 46 mm
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Old 02-19-19, 05:43 PM
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That does seem like a lot. It's not a bad idea to pick up a few UN26s in a variety of lengths. Cheap way to test the fit on this and future projects.
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Old 02-20-19, 07:59 AM
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It may have a 135mm rear, if so you may want a slightly higher chainline number than a typical road double.

You'll know you've gone with too short a spindle when your chain starts dragging on your big ring while you're in your little ring.
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Old 02-20-19, 08:15 AM
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If you have a Tourney front derailleur then Shimano specs 47.5 chainline.

If FD-A050 as the BD site says, then 43.5 is specced, for use with 130mm rear wheels. Maybe add 2 or 3 with 135mm rear.
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Old 02-20-19, 02:07 PM
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Sometimes I feel like an analogue man whose been trapped in a digital world.

With a double chainring, stick a straight edge between the two chainrings. If it bisects whatever you're using for a freewheel or a cassette, you're good. Faster and more accurate than digital measurement.
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Old 02-20-19, 10:21 PM
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If you move your chainrings too far in, you may run out of adjustment range on your FD. Check that before making a purchase.

On less expensive bikes, manufacturers have discovered that many people run them small to small all the time and never shift.....which leads to Shimano's BB recommendations, so that the chain doesn't hit the big ring in small-small. Of course this messes things up for knowledgable bike people.
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Old 02-21-19, 10:11 AM
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Originally Posted by Retro Grouch View Post
Sometimes I feel like an analogue man whose been trapped in a digital world.

With a double chainring, stick a straight edge between the two chainrings. If it bisects whatever you're using for a freewheel or a cassette, you're good. Faster and more accurate than digital measurement.
Yes, I verified my measurement and calculation with your method. And they match good.
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Old 02-21-19, 10:23 AM
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Okay...currently the measured chainline is shown in the pic below. There is a problem: the clearance between Crank and BB shell is only 6mm.
So...I believe I have 2 options:
  1. The current BB is 122mm...get a 110mm...
    122-(2x6) = 110...
    this is get the chainring to within 5mm of the ideal position...the crank will be almost touching the BB shell...
    but this is not perfection...but this is cheap and simple to do.
  2. Find a different Crank that put the chainring closer to the centerline...
    the current chainring is pressed into the Crank...
    I might find a Crank and BB combo that give me perfection...but this could be expensive and time consuming to find the right combo.

#################################################################################################### ####################







Originally Posted by nfmisso View Post
If you move your chainrings too far in, you may run out of adjustment range on your FD. Check that before making a purchase.

On less expensive bikes, manufacturers have discovered that many people run them small to small all the time and never shift.....which leads to Shimano's BB recommendations, so that the chain doesn't hit the big ring in small-small. Of course this messes things up for knowledgable bike people.
Originally Posted by LesterOfPuppets View Post
If you have a Tourney front derailleur then Shimano specs 47.5 chainline.

If FD-A050 as the BD site says, then 43.5 is specced, for use with 130mm rear wheels. Maybe add 2 or 3 with 135mm rear.
The rear spacing is 126mm.

Last edited by mtb_addict; 02-21-19 at 01:46 PM.
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Old 02-21-19, 10:54 AM
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Originally Posted by mtb_addict View Post
Okay...currently the measured chainline is shown in the pic below. There is a problem: the clearance between Crank and BB shell is only 6mm.
So...I believe I have 2 options:
  1. The current BB is 122mm...get a 110mm...
    122-(2x6) = 110...
    this is get the chainring to within 5mm of the ideal position...the crank will be almost touching the BB shell...
    but this is not perfection...but this is cheap and simple to do.
  2. Find a different Crank that put the chainring closer to the centerline...
    the current chainring is pressed into the Crank...
    I might find a Crank and BB combo that give me perfection...but this could be expensive and time consuming to find the right combo.

#################################################################################################### ####################








The rear spacing is 126mm.
126??? Wow!!!!!!! '80s flashback.

When you take the rear wheel out does the space between dropouts remain 126?

Is the frame steel? Is it a lugged frame like that in the diagrams?

The rear hub may be improperly spaced. Is it a nutted axle or QR?

Having the chainline fall a cog or two outside the middle cog usually isn't a big problem.

If shifting is OK I'd be hesitant to bother doing anything. I like at least 3mm clearance between chainrings and chainstay, and crankarm and chainstay. So if a 110 BB will bring it that close Id go 113 instead.

Last edited by LesterOfPuppets; 02-21-19 at 11:03 AM.
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Old 02-21-19, 11:05 AM
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Originally Posted by LesterOfPuppets View Post
126??? Wow!!!!!!! '80s flashback.

When you take the rear wheel out does the space between dropouts remain 126?

Is the frame steel? Is it a lugged frame like that in the diagrams?

Having the chainline fall a cog or two outside the middle cog usually isn't a big problem.

If shifting is OK I'd be hesitant to bother doing anything. I like at least 3mm clearance between chainrings and chainstay, and crankarm and chainstay. So if a 110 BB will bring it that close Id go 113 instead.
Regarding the Front Deraileur...there's plenty of adjustment...current the L-limit screw is all the way in, which by itself suggest the chainline is way off.

Steel Crhomoloy frame. Not lugged.

I haven't ridden the bike enough yet...but so far...the chain shifht smoothly...but there's chain noise.

I'm used to zero chain noise from a Single-speed bike with perfect chainline...so I might be jaded. Maybe multiple speed bikes are just naturally very noisy and I just need to get used to it.

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Old 02-21-19, 11:08 AM
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Originally Posted by mtb_addict View Post
Regarding the Front Deraileur...there's plenty of adjustment...current is it set in the lowest setting, which by itself suggest the chainline is way off.

Steel Crhomoloy frame. Not lugged.

I haven't ridden the bike enough yet...but so far...the chain shifht smoothly...but there's chain noise.

I'm used to zero chain noise from a Single-speed bike with perfect chainline...so I might be jaded. Maybe multiple speed bikes are just naturally very noisy.
Multispeed bikes are generally louder. Tourney equipped bikes are often noisy. Just need to see if it's unusually noisy.
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Old 02-21-19, 11:11 AM
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Originally Posted by mtb_addict View Post
Regarding the Front Deraileur...there's plenty of adjustment...current is it set in the lowest setting, which by itself suggest the chainline is way off.
Does "lowest setting" mean the low limit screw is screwed all the way in?

Or all the way out?
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Old 02-21-19, 11:13 AM
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Originally Posted by LesterOfPuppets View Post
Multispeed bikes are generally louder. Tourney equipped bikes are often noisy. Just need to see if it's unusually noisy.
Actually, when I say noisy, I don't really mean noise as in sound. What I mean is, that I feel the chain thru my feet. Does that make sense? It's like the deraileur needs adjustment...but it does not...it is perfectly adjusted. The this feel...I attribute to chainline issue.

On my SS, I feel nothing almost...it is very smooth.
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Old 02-21-19, 11:14 AM
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Originally Posted by LesterOfPuppets View Post
Does "lowest setting" mean the low limit screw is screwed all the way in?

Or all the way out?
Yes, I meant the L-limit screw is almost all the way in.
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Old 02-21-19, 11:17 AM
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Originally Posted by mtb_addict View Post
Yes, I meant the L-limit screw is almost all the way in.
Have you determined the FD model? Should be stamped on the inner plate. If it's a triple model one would expect the LL screw to be screwed in when mated with a double.
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Old 02-21-19, 01:11 PM
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Originally Posted by LesterOfPuppets View Post
Have you determined the FD model? Should be stamped on the inner plate. If it's a triple model one would expect the LL screw to be screwed in when mated with a double.
I'll have to check when I get home tonite.
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