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Optimizing Chainline

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Optimizing Chainline

Old 01-09-21, 09:44 PM
  #1  
Moisture
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Optimizing Chainline

I tend to avoid using the larger cogs on my rear freewheel/cassette because I can feel drivetrain losses due to my chain bending.



Using this for reference, I can roughly say that my chainline while using 34 or 30t on the rear cassette, my chainline is just outside of what would be considered "within tolerance."

Bearing this in mind, is there any way i can use some sort of spacers between my chainrings to try and help with this? Or how could I find a crankset in the future which allows for a better chainline? Anything I could measure?
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Old 01-09-21, 11:18 PM
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Originally Posted by Bill Kapaun View Post
You don't give any details about what crank/ring(s) you're using.
IF this is a single speed the simple answer would be a shorter BB spindle.
Your sketch shows a lot of offset on the NDS but NONE on the DS.
Not sure what ND or DS means. A quick search only specifies information about Nintendo DS.

I'm using a Truvativ Touro double ring crankset. Was using 34/50 circle rings first. Now got 38/48 biopace. That didn't make any difference with chainline.

The crankset is pretty much as close into the right side of the BB cylinder as possible.

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Old 01-10-21, 07:22 AM
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Originally Posted by Bill Kapaun View Post
A bit of web searching indicates that crank may be a Sq. taper OR an ISIS.
WHICH?

How much is "pretty much as close into the right side of the BB cylinder as possible?
Vague answers aren't real helpful.

Did you realign the DO's so that they are parallel? Going from 120 to 130mm without doing so is going to eat bearing cones.
It appears you are trying to turn a sows ear into a sows ear with problems.
Don't even mess with >7 speed unless you have at least 130mm Do spacing. Pick up a different frame from Craigslist or ??.
my crankset is square taper.

The bottom bracket spindle im using is pretty much close enough so that the inner part of the crankset (which is designed to partially slip inside the BB cylinder) is just about the touch, but not quite.

Referring to my little diagram, my chainline is apparently within tolerances for what would be considered normal.

I didnt really have to spread the dropouts much to get it to fit... I'd say its mostly aligned, but unlikely to be 100% perfect. I don't think its enough to cause any bearing wear inside the hub, but if you still think it's a bad idea, I will have to look for a wheel with a 126mm hub and go with 7 speed.

The rear end of the bike otherwise feels really good, nice and smooth.
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Old 01-10-21, 07:56 AM
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Ideal chainline puts the gap between the two chainrings in line with the middle of the rear cluster. Spacers between the rings are not a good idea; that will allow the chain to jam between the rings when shifting between them. Chainline adjustments can be made by adding a spacer under the flange of the fixed cup to move the crank outward, or by using a shorter bottom bracket spindle to move the crank inward. Some cartridge bottom brackets allow side-to-side adjustment of the whole cartridge, e.g. Phil Wood. Most inexpensive cartridges do not, although spacers can sometime be installed on the drive side to move the crank outward, and a cartridge with a shorter spindle can move the crank inward.
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Old 01-11-21, 06:44 AM
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Originally Posted by Moisture View Post
Not sure what ND or DS means. A quick search only specifies information about Nintendo DS.

I'm using a Truvativ Touro double ring crankset. Was using 34/50 circle rings first. Now got 38/48 biopace. That didn't make any difference with chainline.

The crankset is pretty much as close into the right side of the BB cylinder as possible.

I believe in this context,
DS=Drive Side (side where chain is)
NDS=Non-Drive Side
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Old 01-11-21, 07:02 AM
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Originally Posted by Moisture View Post
I tend to avoid using the larger cogs on my rear freewheel/cassette because I can feel drivetrain losses due to my chain bending.
You lost me right there.


Originally Posted by Moisture View Post
Not sure what ND or DS means.
So, you're worried about drivetrain friction, but you don't know the most basic terminology? Seems odd.
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Old 01-11-21, 10:03 AM
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Old 01-11-21, 01:35 PM
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Originally Posted by Moisture View Post
... is there any way i can use some sort of spacers between my chainrings to try and help with this? Or how could I find a crankset in the future which allows for a better chainline? Anything I could measure?
Slow down a bit. Three questions you can answer:

1. What is the distance (in millimeters) from the centerline of your seattube to the line mid-way between your 50 and 34T chainrings?
2. What is the distance (in millimeters) from the line that bisects you rear dropouts to the center-most cog position in your freewheel (5-speed shown? 3rd cog. 6-speed? space between 3rd and 4th cog.)
3) What type of chain are you using (specific make, model of chain)?

I'd be able to help you if I knew these three things.
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Old 01-27-21, 09:08 PM
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Originally Posted by Phil_gretz View Post
Slow down a bit. Three questions you can answer:

1. What is the distance (in millimeters) from the centerline of your seattube to the line mid-way between your 50 and 34T chainrings?
2. What is the distance (in millimeters) from the line that bisects you rear dropouts to the center-most cog position in your freewheel (5-speed shown? 3rd cog. 6-speed? space between 3rd and 4th cog.)
3) What type of chain are you using (specific make, model of chain)?

I'd be able to help you if I knew these three things.
1. (With bike upside down, measured from middle of bottom bracket barrel to in between the two chain rings.. roughly 45 or 46mm

2. About 41mm (note, using a washer on the axle si that the chain clears the dropout in the smallest outer cog)

3. (Current setup, 9 speed cassette, new 9 speed chain.

so my chainline is about 4mm off then

Thank you

Last edited by Moisture; 01-27-21 at 09:37 PM.
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Old 01-28-21, 01:21 AM
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funny, i rode in a training camp with Greg LeMond, he was riding a bunch of old Gitane's he had from his Renault days, had about ten of them, i said " it must be nice to get cool bikes for free' he said "no, just looking at them causes me pain, there just tools of torture to me!'

anyway, i notice he would ride around all the time with this god-awful chain line, he would be on the big ring and the 5th cog up the cluster, you could actually see the chain bowing, too lazy to use the small ring i guess, or he had to slow down when riding with us,

Last edited by cjenrick; 01-28-21 at 01:24 AM.
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Old 02-03-21, 12:45 AM
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Any way I can maybe install some sort of spacers on the inside of each chainring to get them to sit closer inwards? I'm pretty close to having the right chainline here.

I'm assuming that I'd need a crankset with a 41mm chainline for future reference?
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