Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

7->8 spd...should I be concerned about the chainline?

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

7->8 spd...should I be concerned about the chainline?

Old 07-14-13, 04:21 PM
  #1  
stephr1
Senior Member
Thread Starter
 
Join Date: Jan 2011
Location: Silicon Valley, CA (Yes, that one :)
Posts: 133
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 22 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
7->8 spd...should I be concerned about the chainline?

Hi all,

This is somewhat related to my previous post (http://www.bikeforums.net/showthread...=#post15828314).

I've decided to take my '99 Specialized HR from 7 spd. to 8 spd. (wish I had considered this *before* I bought a new 7 spd freehub and cassettes late last year...very poor planning Setting aside the fact I know I'll have to re-dish the rear wheel (good news is rear dropout is 135 mm and a 5 mm spacer that sits on the axle opposite side from the freehub can be removed or maybe replaced with a 1.5 mm spacer to make room for the new 8-spd freehub and cassette), I was curious if I need to be aware of any issues that might be related to how critical the chainline setup would be relative to the cassette. Here's why I ask....

Based on chainline specs from Specialized, cassette dimension data from the Sheldon Brown site and my best ruler/eyeball process |^( it looks like the rear chainline sits pretty much on center (give or take) with the 4th cog/gear of the 7 spd cassette. When I install the 8-spd freehub, (again using Sheldon Browns data) it looks like the chainline would then line up almost 1/2 way between the 4th and 5th gear/cogs (~.1 mm closer to 5). So, it still looks like the chainline sits in the center of the cassette.

Intuitively, it would seem that this is a nice, ideal arrangement and that, other than getting the dishing right/straight and aligned, it should be a no-brainer process. If there is anything anyone thinks I should know about or be aware of in this, please speak now or I am off to potentially screw up my bike when the freehub arrives next week

Thanks in advance...Steph
stephr1 is offline  
Old 07-14-13, 04:49 PM
  #2  
IthaDan 
Senior Member
 
IthaDan's Avatar
 
Join Date: Jan 2012
Location: Ithaca, NY
Posts: 4,917

Bikes: Click on the #YOLO

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
Dish it and ride it. Suboptimal Chainline isn't nearly the deal breaker that everyone makes it out to be.
__________________

Shimano : Click :: Campy : Snap :: SRAM : Bang
IthaDan is offline  
Old 07-14-13, 04:51 PM
  #3  
Retro Grouch 
Senior Member
 
Retro Grouch's Avatar
 
Join Date: Feb 2004
Location: St Peters, Missouri
Posts: 29,254

Bikes: Catrike 559 I own some others but they don't get ridden very much.

Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1142 Post(s)
Liked 20 Times in 16 Posts
I've never worried about it.

Think about your smallest rear cog. It's going to reside in pretty much the same place regardless if it's 7-speed or 8-speed. That's as good as you can get it.
Retro Grouch is offline  
Old 07-14-13, 05:01 PM
  #4  
sreten
Banned.
 
Join Date: Feb 2013
Location: Brighton UK
Posts: 1,662

Bikes: 20" Folder, Road Bike

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Hi,

Chain line is a poor excuse for upgrading and not much of an issue.

However its nice my big front lines up with ~ 5
of 7 and the small front lines up with ~ 2/3 of 7.

For a single front the best chain line is in the middle of the gears
you most use, not physically in the middle of the rear cassette.

rgds, sreten.

I don't use the top two gears of 7 much, the rest a lot.

Last edited by sreten; 07-14-13 at 05:05 PM.
sreten is offline  
Old 07-14-13, 05:07 PM
  #5  
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 36,049

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

Mentioned: 121 Post(s)
Tagged: 1 Thread(s)
Quoted: 4339 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by IthaDan View Post
Dish it and ride it. Suboptimal Chainline isn't nearly the deal breaker that everyone makes it out to be.
+1,
Don't obsess. It's a derailleur bike so spends very little time in an "in-line" combination anyway.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline  
Old 07-14-13, 05:10 PM
  #6  
bradtx
Senior Member
 
Join Date: Jun 2010
Location: Pearland, Texas
Posts: 7,580

Bikes: Cannondale, Trek, Raleigh, Santana

Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 304 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Steph, A couple of years ago I did a similar 7S to 8S change to my 135 mm spaced touring bike. Your cassette's small cog will be the same distance from the chainstay as before with the large cog about 4 mm further inboard. Inconsequential IMHO. The only issue that popped up in the change was my RD required the L stop screw adjusted fully out to allow the RD to travel the extra difference.

Brad

Last edited by bradtx; 07-14-13 at 05:13 PM. Reason: corr
bradtx is offline  
Old 07-14-13, 05:53 PM
  #7  
Bill Kapaun
Senior Member
 
Bill Kapaun's Avatar
 
Join Date: Feb 2007
Location: Mid Willamette Valley, Orygun
Posts: 10,745

Bikes: 86 RockHopper,2008 Specialized Globe. Both upgraded to 9 speeds.

Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 645 Post(s)
Liked 17 Times in 16 Posts
Originally Posted by FBinNY View Post
+1,
Don't obsess. It's a derailleur bike so spends very little time in an "in-line" combination anyway.
+1
I tend to ride a lot on the middle ring & smaller cogs, so I've actually set my chain line a bit "wide".

IMO, "upgrading" from 7 to 8 is rather a waste. IF you really need more gears, go straight to 9. A lot more available cassette combinations.
I went 7>8>9 and basically wasted good money on 8.
Bill Kapaun is offline  
Old 07-14-13, 07:45 PM
  #8  
stephr1
Senior Member
Thread Starter
 
Join Date: Jan 2011
Location: Silicon Valley, CA (Yes, that one :)
Posts: 133
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 22 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Thanks to everyone for the comments. I really appreciate the feedback and input.

A special hello and thx to Retro Grouch and FBinNY who I remember have been kind enough to help me in the past.

After doing the rough calcs, chainline wasn't really a concern (tho, re-dishing the wheel is). It looks like everything shifts just right (or close enough). I just wanted to check in with the xperts and see if I had missed something in doing this.

Some interesting comments...

Re: use of gears...I am more of an urban MTB'er so I mostly use the upper gears (3-7...top gear is 11T to get a little more speed) and I'm in the middle chainring for 99.9% of the time.

Re: 9 spd. Yeah. I get it. However, I don't know that I could make good use of 9 cogs, given how few I normally use. I had trouble deciding to go to 8 spd. The main thing pushing me was that the 7-spds have gotten cheap and there aren't as many 7 spd cassette options around as there were a few years ago. I could go to 9 spd sometime down the road (freehub supposedly can handle it, not sure of the RD). But I see myself in 8 spds for quite some time.

Again, thanks for the help on this.

Cheers...Steph
stephr1 is offline  
Old 07-14-13, 08:10 PM
  #9  
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 36,049

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

Mentioned: 121 Post(s)
Tagged: 1 Thread(s)
Quoted: 4339 Post(s)
Likes: 0
Liked 1 Time in 1 Post
It's hard to critique anybody's gear selection, but there are three things to consider.

1 ride the gear that's comfortable n\for you in any situation. This is the main objective, but if when you have choices between two comparable combinations the following may help decide.

2- larger sprockets are more efficient, and produce less wear. So if you can choose between the outer and a larger rear instead of the middle and a smaller on, larger is usually better.

3- sprockets that are better aligned are more efficient, so outer with outer half of the cassette, middle with middle, etc. This isn't digital as in good and bad, just a matter of degrees.

Rules 2 and 3 are often in conflict since using the larger chainring may force you inboard on the cassette, and the middle with a smaller sprocket may be better. So throw it all into the hat and remember that rule 1 is what drives the process.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline  
Old 07-14-13, 09:09 PM
  #10  
FastJake
Constant tinkerer
 
FastJake's Avatar
 
Join Date: May 2010
Location: Madison, Wisconsin
Posts: 7,640
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 24 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
If your chainline was fine with 7S it will be fine with 8S. Just don't try using that first cog with the big ring.

Originally Posted by IthaDan View Post
Dish it and ride it. Suboptimal Chainline isn't nearly the deal breaker that everyone makes it out to be.
I mostly agree with this, but terrible chainline can definitely be a deal breaker. I had a beater once setup so bad that I literally could not use the big ring with the first two or three cogs. The chain would fall off the ring if I tried. That's what really bad chainline can do.
FastJake is offline  
Old 07-14-13, 09:30 PM
  #11  
ThermionicScott 
hungry
 
ThermionicScott's Avatar
 
Join Date: Aug 2011
Location: CID
Posts: 18,318

Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers)

Mentioned: 65 Post(s)
Tagged: 0 Thread(s)
Quoted: 1968 Post(s)
Liked 42 Times in 40 Posts
Originally Posted by stephr1 View Post
Re: 9 spd. Yeah. I get it. However, I don't know that I could make good use of 9 cogs, given how few I normally use. I had trouble deciding to go to 8 spd. The main thing pushing me was that the 7-spds have gotten cheap and there aren't as many 7 spd cassette options around as there were a few years ago. I could go to 9 spd sometime down the road (freehub supposedly can handle it, not sure of the RD). But I see myself in 8 spds for quite some time.
Actually, the selection of 7-speed cassettes is nearly as good as it's ever been (certainly better than 8-speed) and Shimano has recently started making HG50 cassettes in silver again: http://www.niagaracycle.com/categori...settes/7-speed

So I wouldn't be in too big a hurry to switch. (Unless you want more gears.)
__________________
Originally Posted by chandltp View Post
There's no such thing as too far.. just lack of time
Originally Posted by noglider
People in this forum are not typical.
RUSA #7498
ThermionicScott is offline  
Old 07-14-13, 10:30 PM
  #12  
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 41,464

Bikes: 8

Mentioned: 183 Post(s)
Tagged: 0 Thread(s)
Quoted: 6718 Post(s)
Likes: 0
Liked 139 Times in 117 Posts
Doing the frame spreading, too ?
fietsbob is offline  
Old 07-14-13, 11:13 PM
  #13  
ThermionicScott 
hungry
 
ThermionicScott's Avatar
 
Join Date: Aug 2011
Location: CID
Posts: 18,318

Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers)

Mentioned: 65 Post(s)
Tagged: 0 Thread(s)
Quoted: 1968 Post(s)
Liked 42 Times in 40 Posts
Originally Posted by fietsbob View Post
Doing the frame spreading, too ?
He's already at 135mm, so I would expect not.
__________________
Originally Posted by chandltp View Post
There's no such thing as too far.. just lack of time
Originally Posted by noglider
People in this forum are not typical.
RUSA #7498
ThermionicScott is offline  
Old 07-14-13, 11:16 PM
  #14  
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 41,464

Bikes: 8

Mentioned: 183 Post(s)
Tagged: 0 Thread(s)
Quoted: 6718 Post(s)
Likes: 0
Liked 139 Times in 117 Posts
ideal chain line is center of cluster.. 4 0f 7 or the space between 4 & 5 of 8.,.
fietsbob is offline  
Old 07-14-13, 11:50 PM
  #15  
rebelLT
Member
 
Join Date: Dec 2012
Posts: 26
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I too find that I ride 99 percent in the middle chainring. All of my bikes are 7 or 8 speed and I have contemplated taking off the front derailleur and two chain rings and running my bike as a seven speed. Hhmmm.
rebelLT is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.