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 07-16-11, 06:43 AM   #1
ncscott
cyclist
Thread Starter
 
Join Date: Aug 2004
Location: vermont
Bikes: road bike, mountain bike, touring bike
Posts: 336
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 18 Post(s)
7sp cassette, 8sp STI

I recently got a bike with a 7speed cassette with down tube shifters. I have a pair of STI levers for 8 speed. Will they work together? I realize there would be an extra click but is the spacing the same for 7 and 8 speeds?
If they won't work, what are my options for putting indexed shifting on the handlebars for my 7 speed bike. I noticed bar ends only go to 8 speed.
Thanks
ncscott is offline   Reply With Quote
Old 07-16-11, 07:59 AM   #2
MNBikeCommuter
Senior Member
 
MNBikeCommuter's Avatar
 
Join Date: Nov 2010
Location: Minnesota
Bikes: Cannondale '92 T600 '95 H600 '01 RT1000
Posts: 600
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Check out Sheldon's Alternate Cable Routings section, as it's what you want:

http://sheldonbrown.com/derailer-adjustment.html

Excerpt:

Shimano originally publicized an alternate cable routing which placed the cable slightly closer to the pivot, making the derailer move slightly farther for each click. This adaptation makes newer Shimano derailers work with older Dura-Ace shifters, but it is also useful when you want to use a 9-speed cassette with 10 speed shifters, or 8-speed cassette with 9-speed shifters, or a 7-speed cluster with 8-speed shifters.
MNBikeCommuter is offline   Reply With Quote
Old 07-16-11, 08:29 AM   #3
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Bikes: 7
Posts: 22,152
Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 1132 Post(s)
Maybe the 'centeron' pulley slop sideways will cover minor mis synch issues..

Quote:
I noticed bar ends only go to 8 speed.
..
you mean you didnn't find the"Dura Ace' 9 speed bar end shifters?
look around more, there are 9 speed too..
but that requires more stuff to by to run 9 speed , and the extra ratio may not really matter.

Generically a 8 speed adds a gear to the spacing of a 7 speed ,
so a leftover shifter klick should not be an issue.

Last edited by fietsbob; 07-16-11 at 09:17 AM.
fietsbob is offline   Reply With Quote
Old 07-16-11, 09:06 AM   #4
LarDasse74
Guest
 
Join Date: Jul 2008
Location: Grid Reference, SK
Bikes: I never learned to ride a bike. It is my deepest shame.
Posts: 3,769
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Ihave tried to use 7 speed shifters on 8 speedcassettes iin the past. The result was barely acceptable - extra concentration and effort required to get between certain gears. Others have said they got it to work perfecty. IIRC, 8 speed has a 4.8mm/gear spacing and 7 speed has 5 mm/gear spacing. The result is that over 7 gears you can be as much as 1.4mm out of alignment, which doesn't sound like much but it is 28% of a step.

I have had moderate success changing a 7 speed hub over to a 8 speed freehub body to use a 8, 9 or 10 cassette, although this changes the spacing of the rear axle.
LarDasse74 is offline   Reply With Quote
Old 07-16-11, 09:35 AM   #5
FastJake
Constant tinkerer
 
FastJake's Avatar
 
Join Date: May 2010
Location: Madison, Wisconsin
Bikes:
Posts: 7,577
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
I've had good luck mixing 7 and 8 speed shifters and cassettes/freewheels. Setup is more finicky but I've always gotten it to shift fine.

If the 7 speed cassette doesn't index to your satisfaction, get an 8 speed cassette and lose one cog. Then it will work as intended. Alternatively, you could tear apart both cassettes and use the 8 speed spacers on your 7S cassette.
FastJake is offline   Reply With Quote
Old 07-16-11, 09:47 PM   #6
Kimmo
bike whisperer
 
Kimmo's Avatar
 
Join Date: Dec 2009
Location: Melbourne, Oz
Bikes: velospace.org/viewcluster?c=873
Posts: 7,115
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Quote:
Originally Posted by FastJake View Post
Alternatively, you could tear apart both cassettes and use the 8 speed spacers on your 7S cassette.
8spd cogs are 0.05mm thinner; this would introduce an error of up to 0.3mm. Not much, but if you have the 8spd cogs, it just makes more sense to use 7/8.

I'd just get hold of an old 8spd cassette body and re-dish the wheel so I could use all 8.
Kimmo is offline   Reply With Quote
Old 07-16-11, 10:04 PM   #7
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Bikes: 7
Posts: 22,152
Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 1132 Post(s)
I like the ratio set of the 7 speed Shimano K cassette. a practical combination.
fietsbob 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 06:51 AM.