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 06-25-03, 08:47 AM   #1
bbarend
Superman With Silver Guns
Thread Starter
 
bbarend's Avatar
 
Join Date: Jun 2003
Location: Knoxville, TN
Bikes: Trek 2100, Cannondale MTB, Fetish SS
Posts: 220
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
8 speed shifter 7 speed cassette

Can a rear derailieur be tuned so that an 8 speed sti shifter will work on a 7 speed cassette? The chains are the same size. It seems all you would have to do is adjust the stops on the derailieur.
bbarend is offline   Reply With Quote
Old 06-25-03, 09:24 AM   #2
Chi
Rides with Cows
 
Chi's Avatar
 
Join Date: Apr 2003
Location: Fixing a flat
Bikes: Trek 7000
Posts: 1,232
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I think you need to have 7 speed shifters and adjust cable tension as well as the stops.
__________________
Chi is offline   Reply With Quote
Old 06-25-03, 01:55 PM   #3
dwatson
Senior Member
 
dwatson's Avatar
 
Join Date: Jan 2003
Location: MD
Bikes:
Posts: 387
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Yes, you can do it. Just like you said you will have to adjust the stops. Just remeber that you will have an extra click in the shifter.
But with the said, it is best to run a complete group, 7 or 8 speed.
dwatson is offline   Reply With Quote
Old 06-25-03, 02:04 PM   #4
FOG
Senior Member
 
Join Date: Apr 2003
Location: Annapolis, MD
Bikes:
Posts: 798
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
The cassette spacing is different in 8 speed versus 7.
http://www.sheldonbrown.com/k7.html#spacing
FOG is offline   Reply With Quote
Old 06-25-03, 02:22 PM   #5
bbarend
Superman With Silver Guns
Thread Starter
 
bbarend's Avatar
 
Join Date: Jun 2003
Location: Knoxville, TN
Bikes: Trek 2100, Cannondale MTB, Fetish SS
Posts: 220
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Ok, so who is correct. Sheldon Brown also says "Modern indexing systems are so forgiving, however, that many theoretically incompatible combinations actually work fairly well." Has anyone ever tried it?
bbarend is offline   Reply With Quote
Old 06-25-03, 03:59 PM   #6
Chi
Rides with Cows
 
Chi's Avatar
 
Join Date: Apr 2003
Location: Fixing a flat
Bikes: Trek 7000
Posts: 1,232
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
My bike came with 7-speed components out of the box. However, the previous owner had upgraded the cassette to an 8-speed, but neglected to do the same with the shifters. All I had to do once I got the bike was buy new shifters (and a new chain--but the same kind, IG90). It works almost like a charm now, except for the front derailleur which I think has seen its last days ...
__________________
Chi is offline   Reply With Quote
Old 06-25-03, 04:07 PM   #7
BikerRyan
Senior Member
 
BikerRyan's Avatar
 
Join Date: Dec 2002
Bikes:
Posts: 306
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
its really fairly easy to do. Just put the shifter in the 8th position so that all the cable is out. Then move the rear der. to the smallest cog and make sure that the limit is holding the der. right underneath that small cog. Then pull the cable finger tight and anchor it under the bolt. A couple of left turns on the barrel adjuster should have it tight enough after that. Then shift up to the largest cog again checking the limit so that your last shifter click wont send the der. flying into the spokes and you should be done. Setting it up this way keeps the shifter from having that last annoying extra gear although your gear indicator, should you have one, will be one number off.

-Ryan
BikerRyan is offline   Reply With Quote
Old 06-25-03, 05:54 PM   #8
Chasbo
Senior Member
 
Join Date: May 2002
Location: Hagerstown
Bikes:
Posts: 77
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Keep in mind that the spacing is different and your indexing will require more tune-ups than if you used the proper cassette. Other than that you can fudge it so it will work so-so. It will never work as well as full 8 speed would.

Chuck
Chasbo is offline   Reply With Quote
Old 06-25-03, 06:28 PM   #9
chip
Senior Member
 
chip's Avatar
 
Join Date: May 2003
Bikes:
Posts: 314
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
You could rig it up but you'll have an extra click at the end like has already been mentioned?What about the resale value it could be harder for you to sell or trade in when it's like that.
chip is offline   Reply With Quote
Old 06-25-03, 08:45 PM   #10
uciflylow
Look Ma, NO hands!
 
Join Date: Oct 2002
Location: UC Tennessee
Bikes:
Posts: 988
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I put drop bars on my MTB commuter recently and wanted to use bar end shifters. The 7 speed index shifters are almost impossible to find and when you do they are more used than new 8 speed stuff!
I got a set of 8 speed index off eBay with the intentions of using friction if I had to. Long story short, they work like a charm with the 7 speed IG system. You just have that extra click at the bottom of the travel limit. I set mine up to where the low speed click is at the end of the limits and the high end "little sprocket" has the extra click, you just get extra slack if you click one too many on the high end.
Good luck
uciflylow is offline   Reply With Quote
Old 06-26-03, 06:12 AM   #11
bbarend
Superman With Silver Guns
Thread Starter
 
bbarend's Avatar
 
Join Date: Jun 2003
Location: Knoxville, TN
Bikes: Trek 2100, Cannondale MTB, Fetish SS
Posts: 220
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks for all the input!
bbarend is offline   Reply With Quote
Old 01-29-09, 04:52 PM   #12
Grand Bois
Senior Member
 
Grand Bois's Avatar
 
Join Date: Mar 2005
Location: Pinole, CA, USA
Bikes:
Posts: 16,568
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 31 Post(s)
I don't know what uciflylow is talking about in that thread. There is no extra click. The derailer stop screws and cable tension won't allow it if it's set up right.

I have a 7 speed cassette and 8 speed shifters on my wife's bike and it performs perfectly.

Grand Bois is offline   Reply With Quote
Old 01-29-09, 05:01 PM   #13
caloso
Packfodding 3
 
caloso's Avatar
 
Join Date: Jul 2002
Location: Sacramento, California, USA
Bikes: Ridley Excalibur, Gazelle Champion Mondial, On-One Pompino, Specialized Rock Hopper
Posts: 33,615
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 55 Post(s)
Quote:
Originally Posted by uciflylow View Post
I put drop bars on my MTB commuter recently and wanted to use bar end shifters. The 7 speed index shifters are almost impossible to find and when you do they are more used than new 8 speed stuff!
I got a set of 8 speed index off eBay with the intentions of using friction if I had to. Long story short, they work like a charm with the 7 speed IG system. You just have that extra click at the bottom of the travel limit. I set mine up to where the low speed click is at the end of the limits and the high end "little sprocket" has the extra click, you just get extra slack if you click one too many on the high end.
Good luck

I did something similar -- old set of 8spd RSX brifters on my 7spd Rock Hopper. It works okay. Not perfect, but good enough for a grocery-getter/kid-trailer-puller.
caloso is offline   Reply With Quote
Old 01-29-09, 05:29 PM   #14
Retro Grouch 
Senior Member
 
Retro Grouch's Avatar
 
Join Date: Feb 2004
Location: St Peters, Missouri
Bikes: Rans Rockst (Retro rocket) Rans Enduro Sport (Retro racket) Catrike 559, Merin Bear Valley (beater bike).
Posts: 26,535
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 58 Post(s)
7-speed and 8-speed cassette spacing is only a hair off. Many riders report mixing and matching 7-speed and 8-speed components with good results. If you do this the best thing is to adjust the cable tension so that the derailleur lines up spot-on when it's in the middle of the cassette. That way your "fuzz factor" will be spread over two different directions.

Personally, I've fooled around mixing 7-speed and 8-speed components, both road and mountain, in various combinations. I've never been able to get them to work to my satisfaction over any significant period of time but maybe I'm just too picky.
Retro Grouch is offline   Reply With Quote
Old 01-29-09, 05:36 PM   #15
Metzinger
Primate
 
Metzinger's Avatar
 
Join Date: Jan 2006
Location: gone
Bikes: Concorde Columbus SL, Rocky Mountain Edge, Sparta stadfiets
Posts: 2,582
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I've used a 7/8 combination happily from time to time, and even raced on one. Each time it was with an 8 speed cassette and 7 speed downtube shifters. I'd pull the shifter past the last click to get the largest cog. Only problem was the chain would sometime shift out of that cog when I hit a bump.
Metzinger is offline   Reply With Quote
Old 04-19-11, 09:26 PM   #16
SuperFatDave
Senior Member
 
Join Date: May 2006
Bikes:
Posts: 98
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
If you have the ability, the know how and the patience, you can make a variety of Shimano shifters and derailleurs work, despite what the specs say.
Your results may vary from perfect to passable.
The specs are for setting things up so that it is the best there is/it can be.
That's why folks who do the own repairs may try and suceed at things that mechanics in bike shops won't do, as the guy in the shop has to sweat specs, warranties and customer satisfaction. Hence he stays away from "jury rigs".
The home/own mechanic tries knowing what he's willing to do/invest. If it works, he's happy. If it doesn't then he goes the spec route.
The issue boils down what you want done is determined by who is doing the work.
SuperFatDave is offline   Reply With Quote
Old 04-19-11, 09:39 PM   #17
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)
Sometimes it works and sometimes it doesn't but usually, if the difference between the shifter and cassette is one the drive can work reasonably well and then, some combinations of shifters, derailleurs, and cassettes just don't play well together.

Ran my mtb with a 9 speed shifter and an 8 speed cassette for quite some time and was pretty pleased but it is flawless now that it is running 9 and 9.

The rule of thumb is that old Suntour and Shimano won't play well together either but if you run a shifter that is plus 1 you can often get nice results because Suntour spacing was a little tighter.
Sixty Fiver is offline   Reply With Quote
Old 04-19-11, 09:46 PM   #18
FastJake
Constant tinkerer
 
FastJake's Avatar
 
Join Date: May 2010
Location: Madison, Wisconsin
Bikes:
Posts: 7,574
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Sixty Fiver View Post
The rule of thumb is that old Suntour and Shimano won't play well together either but if you run a shifter that is plus 1 you can often get nice results because Suntour spacing was a little tighter.
I put a Shimano 7S shifter on my dad's 1983 Schwinn World Sport equipped with a Suntour RD and Suntour 6S freewheel. It works surprisingly well for a freewheel and derailer not designed for index shifting. It's not great, but he rides his bike about twice a decade so it's a non-issue..
FastJake 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 01:04 AM.