Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

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.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 03-27-11, 10:32 PM   #1
rothenfield1
Senior Member
Thread Starter
 
rothenfield1's Avatar
 
Join Date: Jun 2009
Location: Montereyish
Bikes:
Posts: 2,330
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Rear Dropout Adjuster- Why & How

I like working on older bikes and I see these all-the-time without really understanding them. My primary question; that I’ve wondered about for awhile; is: How do you know when the rear wheel is absolutely straight. It seems that the eyeball method could never be really accurate, unless by chance; and that even a minuscule error would cause extra tire wear, at the least. What is your method to set the adjusters, and is really important?
The secondary question I have I guessed with no proof. I can see how the ability to adjust the wheelbase would be a nice feature. Lengthen it when you need extra stability, control, and comfort; shorten it on race day.
rothenfield1 is offline   Reply With Quote
Old 03-27-11, 10:40 PM   #2
relyt
Senior Member
 
Join Date: Jan 2004
Bikes:
Posts: 619
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Actually the only way to do it is by eye, and it works fine. The wheel doesn't need to be *perfectly* straight.

The screws are there so that once you get the wheel straight, you can tighten up the screws. Then the next time you insert the wheel, push it in until it hits the screws and it will be in the exact same place it was last time.
relyt is offline   Reply With Quote
Old 03-27-11, 10:56 PM   #3
rothenfield1
Senior Member
Thread Starter
 
rothenfield1's Avatar
 
Join Date: Jun 2009
Location: Montereyish
Bikes:
Posts: 2,330
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by relyt View Post
Actually the only way to do it is by eye, and it works fine. The wheel doesn't need to be *perfectly* straight.

The screws are there so that once you get the wheel straight, you can tighten up the screws. Then the next time you insert the wheel, push it in until it hits the screws and it will be in the exact same place it was last time.
Why not just take them out then?
rothenfield1 is offline   Reply With Quote
Old 03-27-11, 11:07 PM   #4
Kimmo
bike whisperer
 
Kimmo's Avatar
 
Join Date: Dec 2009
Location: Melbourne, Oz
Bikes: copy/paste links: http://velospace.org/node/36949 http://velospace.org/node/47746 http://velospace.org/node/47747
Posts: 7,099
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Because of the angle of the dropouts, shortening the wheelbase also steepens the head angle a bit.

Pretty tiny changes, though. I never really saw the point, unless it was to allow framebuilders to be more sloppy...
Kimmo is offline   Reply With Quote
Old 03-28-11, 12:41 AM   #5
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Bikes: 7
Posts: 18,766
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 207 Post(s)
the adjusters are justthere so when you pull the wheel back in, after mending a puncture
the wheel goes back in the same spot..

but they rust fuse in place after a while.
fietsbob is offline   Reply With Quote
Old 03-28-11, 12:52 AM   #6
Sixty Fiver
Bicycle Repair Man !!!
 
Sixty Fiver's Avatar
 
Join Date: Sep 2007
Location: YEG
Bikes: See my sig...
Posts: 27,255
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
When you set up a bike's derailleurs you dial the derailleur's position relative to the cog set to maximize the performance of the shifting system and if you re-install the wheel in a different position this will affect the fine tuning of the rear d and change the chain tension.

The set screws ensure that the wheel goes back in the same position and that it will be properly aligned in the frame and when you are setting up the bike you can use these set screws to make very fine adjustments.

It is something you only find on higher quality frames with cast dropouts... lesser frames often use a backstop for the drive side and the wheel gets aligned by shifting the position of the axle on the non drive side.
Sixty Fiver is offline   Reply With Quote
Old 03-28-11, 01:10 AM   #7
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Bikes: 7
Posts: 18,766
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 207 Post(s)
And Forged dropouts .. have 2 Campag 1010 dropouts , 2 bikes .. as such.
fietsbob is offline   Reply With Quote
Old 03-28-11, 01:28 AM   #8
fuzz2050
Real Men Ride Ordinaries
 
fuzz2050's Avatar
 
Join Date: Sep 2008
Bikes:
Posts: 3,697
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Sixty Fiver View Post
When you set up a bike's derailleurs you dial the derailleur's position relative to the cog set to maximize the performance of the shifting system and if you re-install the wheel in a different position this will affect the fine tuning of the rear d and change the chain tension.
This is the only answer I've heard that makes any sense. The changes in wheelbase would be to minuscule to really make an impact, and proper alignment could be more easily achieved by simply pulling the wheel to the back of the dropouts.
fuzz2050 is offline   Reply With Quote
Old 03-28-11, 05:22 AM   #9
JohnDThompson 
Old fart
 
JohnDThompson's Avatar
 
Join Date: Nov 2004
Location: Appleton WI
Bikes: Several, mostly not name brands.
Posts: 16,357
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 56 Post(s)
Quote:
Originally Posted by rothenfield1 View Post
Why not just take them out then?
You can, and you'll be none the worse off.

The bolts were originally intended as a racing feature, to facilitate quick wheel changes. Once properly set, you just pull the wheel all the way back against the stops, tighten the QR down and you're good. But they also weaken the dropout -- a common dropout failure mode is cracking through those bolt holes.
JohnDThompson is offline   Reply With Quote
Old 03-28-11, 09:29 AM   #10
rothenfield1
Senior Member
Thread Starter
 
rothenfield1's Avatar
 
Join Date: Jun 2009
Location: Montereyish
Bikes:
Posts: 2,330
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks all. It sounds like there are pros and cons to whether or not to remove them And, an eyeball alignment seems the only practical way to set them. I guess I'll just keep doing what I always have and that is to set them the best I can and then leave them alone.
rothenfield1 is offline   Reply With Quote
Old 03-28-11, 09:37 AM   #11
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
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
Posts: 29,390
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 70 Post(s)
You don't want to remove the adjustment screws because then you'll have to recenter the wheel every time you re-install it. Their purpose is to provide a single, reliable, repeatable position for the axle, so that wheel changes can be done on the fly without having to fool around dialing in the position. Vertical dropouts do the same job eliminating the need for the positioning screws.

BTW- when these were in common use, one problem is that with normal (somewhat rough) handling these would get bent where they stuck out behind the dropout. This was a problem because they couldn't be moved or removed without damaging the threads in the dropout. When I set up team bikes, I'd get them perfectly adjusted then saw off and file smooth the section outside the frame. If need be they could still be adjusted or removed from the axle end, but no more damaged threads.
__________________
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   Reply With Quote
Old 03-28-11, 10:19 AM   #12
HillRider 
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Bikes: '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
Posts: 28,776
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 36 Post(s)
Quote:
Originally Posted by FBinNY View Post
BTW- when these were in common use, one problem is that with normal (somewhat rough) handling these would get bent where they stuck out behind the dropout. This was a problem because they couldn't be moved or removed without damaging the threads in the dropout. When I set up team bikes, I'd get them perfectly adjusted then saw off and file smooth the section outside the frame. If need be they could still be adjusted or removed from the axle end, but no more damaged threads.
Since these are just standard M3 bolts, one way to handle the too-long problem is use shorter bolts. I replaced the ones in my Surly with a pair of bolts just long enough to let me adjust the wheel alignment with very little sticking out the back of the dropout.
HillRider is offline   Reply With Quote
Old 03-28-11, 10:27 AM   #13
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
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
Posts: 29,390
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 70 Post(s)
Quote:
Originally Posted by HillRider View Post
Since these are just standard M3 bolts, one way to handle the too-long problem is use shorter bolts. I replaced the ones in my Surly with a pair of bolts just long enough to let me adjust the wheel alignment with very little sticking out the back of the dropout.
Same result, but the bikes came with the screws and sawing was free which trumped having to spend dough. Also 40 years ago 3x.5 screws weren't as readily available as they are today.
__________________
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   Reply With Quote
Old 03-28-11, 06:35 PM   #14
HillRider 
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Bikes: '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
Posts: 28,776
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 36 Post(s)
Quote:
Originally Posted by FBinNY View Post
Same result, but the bikes came with the screws and sawing was free which trumped having to spend dough. Also 40 years ago 3x.5 screws weren't as readily available as they are today.
I didn't exactly spend much. The bolts were left-overs from some long gone Cat-Eye cyclonmeter handlebar clamps.
HillRider is offline   Reply With Quote
Old 03-28-11, 06:55 PM   #15
rogerstg
Fred-ish
 
rogerstg's Avatar
 
Join Date: Aug 2007
Location: Rhode Island
Bikes:
Posts: 1,800
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by rothenfield1 View Post
...And, an eyeball alignment seems the only practical way to set them. I guess I'll just keep doing what I always have and that is to set them the best I can and then leave them alone.
FWIW, you can use the Sheldon Brown technique for measuring frame alignment. Just measure from the string to the wheel rim instead of the seatpost.
rogerstg is offline   Reply With Quote
Old 03-28-11, 07:28 PM   #16
xyzzy834
Senior Member
 
Join Date: May 2009
Bikes:
Posts: 358
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
For a smooth running chain, you want the wheel to be very, very close to parallel with the front chainrings. It's worth getting out a caliper and setting the wheel position by adjusting the dropout bolts. Once that is set, the Park derailleur alignment tool is the best $50ish you can spend for getting clean, crisp shifts.



The Park tool allows you to align the derailleur hanger to be very close to precisely parallel to the wheel and thus the rear cluster. After you've gone to the trouble of getting everything aligned, it's worth having the dropout adjusters to make sure that removing the rear wheel and replacing it doesn't screw up your great shifting rear derailleur.
xyzzy834 is offline   Reply With Quote
Old 03-28-11, 07:51 PM   #17
Grand Bois
Senior Member
 
Grand Bois's Avatar
 
Join Date: Mar 2005
Location: Pinole, CA, USA
Bikes:
Posts: 16,551
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 24 Post(s)
Quote:
Originally Posted by fietsbob View Post
And Forged dropouts .. have 2 Campag 1010 dropouts , 2 bikes .. as such.
I've noticed that Sixty Fiver always calls forged dropouts cast. Maybe it's a Canadian thing.
Grand Bois is offline   Reply With Quote
Old 03-28-11, 08:39 PM   #18
conspiratemus1
Used to be Conspiratemus
 
Join Date: Jan 2009
Location: Hamilton ON Canada
Bikes:
Posts: 776
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I'll just add that provision for fore-and-aft adjustment of the wheel is no longer necessary because modern derailleurs have B-tension adjustment screws which accomplish the same thing, hence vertical dropouts. But for a "classic" derailleur like a Campy NR or SR, you need horizontal dropouts to get everything dialed in properly.
conspiratemus1 is offline   Reply With Quote
Old 03-28-11, 09:55 PM   #19
Sixty Fiver
Bicycle Repair Man !!!
 
Sixty Fiver's Avatar
 
Join Date: Sep 2007
Location: YEG
Bikes: See my sig...
Posts: 27,255
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Quote:
Originally Posted by Grand Bois View Post
I've noticed that Sixty Fiver always calls forged dropouts cast. Maybe it's a Canadian thing.
Cast and forged are two different things process - wise but you get similar results... but even if they are forged my brain wants to say cast.

Too much time spent in the machine shop working on cast parts I guess.
Sixty Fiver is offline   Reply With Quote
Old 03-28-11, 10:34 PM   #20
rothenfield1
Senior Member
Thread Starter
 
rothenfield1's Avatar
 
Join Date: Jun 2009
Location: Montereyish
Bikes:
Posts: 2,330
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Good stuff Gentlemen. A bit over my head for now. Sometimes I feel like I'm a work in progress as much as the bikes I work on.
rothenfield1 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

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



All times are GMT -6. The time now is 04:33 PM.