7 speed shifters index to 8 speed cassette
#1
Kid A
Thread Starter
Join Date: Aug 2009
Location: Alexandria, VA
Posts: 1,778
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 5 Times
in
5 Posts
7 speed shifters index to 8 speed cassette
I've read that this is possible due to the close spacing of the two systems, but I've never had my 7 speed DT shifters index very well with an 8-speed cassette.
Is there a trick way to adjust them to work properly? Or are people just satisfied with having a few gears not mesh properly?
Is there a trick way to adjust them to work properly? Or are people just satisfied with having a few gears not mesh properly?
#2
aka: Dr. Cannondale
Join Date: Jul 2009
Posts: 7,729
Mentioned: 234 Post(s)
Tagged: 0 Thread(s)
Quoted: 2152 Post(s)
Liked 3,402 Times
in
1,203 Posts
I find that using 6 speed shifters with a 7 speed FW works, but not so much a 7 speed shifter with an 8 speed FW. My latest project is a KHS Flight 500 frame build, and I'm using an 8 speed DT shifter (Shimano 600) with the 8 speed cassette to avoid the noisy shifting and 'missing' index at the bottom of the shift stroke. 8 speed Shimano shifters are out there if you look for them...
#3
Call me The Breeze
I run an 8sp cassette with 7sp XT thumb shifters. It takes a bit of extra patience to get it just right, but in my case at least, it works quite well now and I'm very particular when it comes to things working correctly.
Make sure your limit screws, especially the high limit are set correctly.
Be sure your derailleur hanger is straight and true.
There's .2mm difference in spacing between each cog between 7 and 8 speeds, so that's a total of 1.4mm you'll have to make up. Fortunately .7mm on either end of the range is usually within the tolerance of the derailleur to work properly. I'm using an XT derailleur FWIW.
You'll have to go by trial and error to get it just right, but since the shifter pulls more cable than it should, In my case I leave the high limit screw set slightly farther out than I normally would. Basically you want it as far out as you can go without throwing the chain.
The other thing to try is to leave the cable just slightly looser than you normally would The extra slop on the first shift (from 8 to 7) will help to deal with the accumulated spacing difference over the range of the cassette.
So, hard to describe in words but hope that helped a little!
Edit- I also forgot to mention that the old Shimano thumb shifters (XT and Deore at least) have an extra click built in which obviously makes things easier.
Also also, you can always switch to friction.
Make sure your limit screws, especially the high limit are set correctly.
Be sure your derailleur hanger is straight and true.
There's .2mm difference in spacing between each cog between 7 and 8 speeds, so that's a total of 1.4mm you'll have to make up. Fortunately .7mm on either end of the range is usually within the tolerance of the derailleur to work properly. I'm using an XT derailleur FWIW.
You'll have to go by trial and error to get it just right, but since the shifter pulls more cable than it should, In my case I leave the high limit screw set slightly farther out than I normally would. Basically you want it as far out as you can go without throwing the chain.
The other thing to try is to leave the cable just slightly looser than you normally would The extra slop on the first shift (from 8 to 7) will help to deal with the accumulated spacing difference over the range of the cassette.
So, hard to describe in words but hope that helped a little!
Edit- I also forgot to mention that the old Shimano thumb shifters (XT and Deore at least) have an extra click built in which obviously makes things easier.
Also also, you can always switch to friction.
#4
Primate
Join Date: Jan 2006
Location: gone
Posts: 2,579
Bikes: Concorde Columbus SL, Rocky Mountain Edge, Sparta stadfiets
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 5 Times
in
5 Posts
I ran 7sp 105 DT shifters with an 8sp cassette for a couple of years. My main beef was with the largest cog. The chain didn't want to stay on it as there was no detent on the shifter for that gear. On long climbs I had to keep pushing the right lever forward. I_bRAD's set-up sounds like how I adjusted mine. I don't know if it helped, but my cassette was practically a straight-block.
#5
Kid A
Thread Starter
Join Date: Aug 2009
Location: Alexandria, VA
Posts: 1,778
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 5 Times
in
5 Posts
Actually, your two descriptions make prefect sense to me . I appreciate it. I may try again to see if I can set it up - I kind of like index on the rear derailleur. Not 100% necessary, but I like it.
After the chain wears out it won't matter - I'll pick up a 7 speed cassette.
After the chain wears out it won't matter - I'll pick up a 7 speed cassette.
#6
Call me The Breeze
Nice 7sp cassettes are getting harder to find! You can still get the HG70 though. I'm running a 12-32 XTR which is very nice, but it was expensive (and I get parts for wholesale even)
#9
Senior Member
I've used Campy C-Record 7-speed downtube shifters with an 8-speed Campy cassette with no problems.
#10
Kid A
Thread Starter
Join Date: Aug 2009
Location: Alexandria, VA
Posts: 1,778
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 5 Times
in
5 Posts
Ok, tried it this evening. It hasn't worked well.
Strangely, the shifters want to skip a cog (the 3rd smallest) when shifting each direction across the cassette. This makes me wonder if I installed the cassette with incorrect spacers at some point....which is possible since I basically "rigged" this one together from a couple of older 8 speeds I had laying around.
Thanks for the advice though
Back to friction mode-
Strangely, the shifters want to skip a cog (the 3rd smallest) when shifting each direction across the cassette. This makes me wonder if I installed the cassette with incorrect spacers at some point....which is possible since I basically "rigged" this one together from a couple of older 8 speeds I had laying around.
Thanks for the advice though
Back to friction mode-
#11
Primate
Join Date: Jan 2006
Location: gone
Posts: 2,579
Bikes: Concorde Columbus SL, Rocky Mountain Edge, Sparta stadfiets
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 5 Times
in
5 Posts
Are either your shifter or derailleur pre-1997 Dura-Ace?
That could be the issue.
That could be the issue.
#12
Senior Member
Join Date: Feb 2004
Location: St Peters, Missouri
Posts: 30,225
Bikes: Catrike 559 I own some others but they don't get ridden very much.
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1572 Post(s)
Liked 643 Times
in
364 Posts
Over the years I've fiddled with various combinations of 7 and 8-speed shifters and cassettes. I can get it to kind of work but I can't get it to work to my satisfaction for an extended period of time. My conclusion is that the guys who use such combinations are either better bike mechanics than me or they're not as picky as I am.
#13
Senior Member
Join Date: Feb 2005
Location: Oklahoma
Posts: 9,438
Bikes: Trek 5500, Colnago C-50
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Likes: 0
Liked 7 Times
in
6 Posts
Shimano 7-speed cogs are spaced 5.0 mm center to center.
Shimano 8-speed cogs are spaced 4.8 mm center to center.
That's the problem. The 0.2 mm error is cumulative as you shift across the cassette.
Al
Shimano 8-speed cogs are spaced 4.8 mm center to center.
That's the problem. The 0.2 mm error is cumulative as you shift across the cassette.
Al
#14
Senior Member
Most of us agree that it will probably work but not well. If you're using 7 sp shifters you could pull the 8 sp cassette apart and use 7 sp spacers to give you the 4.8mm spacing. That should give you perfect shifting. Or use a 4.5mm spacer and a 7 sp cassette. Good luck
#15
Call me The Breeze
#16
Call me The Breeze
I too am very particular, and it took me some time to figure out how to set it up just so, so that it worked perfectly. Once it's set up it works exactly as it should though! This may also be one of those situations where it's dependent on a suitable combination of components.
#17
Member
Take the 8 spd cassette apart. Discard the 3.0mm plastic cog spacers. Purchase 3.15mm 7 spd spacers (available on line) and replace the discarded spacers. This results in a 4.95mm cog spacing instead of 4.8mm....closer to the 5.0mm 7 speed spacing. The total stack height will now be slightly more than 1mm thicker, but you should still be able to engage the threads of the hub with the lockring. Alternately, you can discard one 8 spd cog and replace with a 1mm spacer (keep the cog spacer with it). Optionally, if you are using on an 8-10 spd cassette hub (this requires a 2mm spacer using with an 8 spd cassette), you can replace that spacer with a 1mm spacer and keep all 8 cogs. This gives you the option of setting your limit screws for 2 to 8 or 1 to 7 cog usage.Suggest you set the high detent on 7 on the shifter since the cable pulls for lower gears. The shifter detent for 1 and the RD limit will stop together to prevent unintentional cable stretching from over shifting.
#18
Passista
Join Date: Jul 2005
Posts: 7,597
Bikes: 1998 Pinarello Asolo, 1992 KHS Montaña pro, 1980 Raleigh DL-1, IGH Hybrid, IGH Utility
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 866 Post(s)
Liked 721 Times
in
396 Posts
I use a 8sp cassette minus 1 cog on a 7sp hub with a 7sp shifter, works OK.
#19
Senior Member
Join Date: Jun 2014
Location: Ontario, Canada
Posts: 4,624
Bikes: iele Latina, Miele Suprema, Miele Uno LS, Miele Miele Beta, MMTB, Bianchi Model Unknown, Fiori Venezia, Fiori Napoli, VeloSport Adamas AX
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1324 Post(s)
Liked 927 Times
in
640 Posts
And yet another Zombie thread gets reborn by a Newbie. This one languished for NINE YEARS before being resurrected. LOL
Cheers
Cheers
#20
verktyg
Join Date: Jul 2006
Location: SF Bay Area
Posts: 4,030
Bikes: Current favorites: 1988 Peugeot Birraritz, 1984 Gitane Super Corsa, 1980s DeRosa, 1981 Bianchi Campione Del Mondo, 1992 Paramount OS, 1988 Colnago Technos, 1985 RalieghUSA SBDU Team Pro
Mentioned: 207 Post(s)
Tagged: 0 Thread(s)
Quoted: 1036 Post(s)
Liked 1,238 Times
in
654 Posts
Night Of The Living Dead! ARRGH!
I did get an answer for my question though....
verktyg 50:
__________________
Don't believe everything you think! History is written by those who weren't there....
Chas. ;-)
Don't believe everything you think! History is written by those who weren't there....
Chas. ;-)
#21
bike whisperer
Join Date: Dec 2009
Location: Melbourne, Oz
Posts: 9,545
Bikes: https://weightweenies.starbike.com/forum/viewtopic.php?f=10&t=152015&p=1404231
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 1528 Post(s)
Liked 718 Times
in
510 Posts
Surprised the correct answer wasn't provided: rotate the pinch bolt washer so the cable goes around the tab, changing the RD geometry to require more cable pull.
__________________
Sheldon Brown's bike info ~~~ Park Tools repair help
Half-step triple, using double gear ~~~ 6400 STI rebuild walkthrough ~~~ Want 8/9/10s @126mm OLD? OCR. ~~~ Shimano cassette body overhaul ~~~ Ergopower Escape wear repair ~~~ PSA: drivetrain wear
List of US/Canada bike co-ops ~~~ Global list
Sheldon Brown's bike info ~~~ Park Tools repair help
Half-step triple, using double gear ~~~ 6400 STI rebuild walkthrough ~~~ Want 8/9/10s @126mm OLD? OCR. ~~~ Shimano cassette body overhaul ~~~ Ergopower Escape wear repair ~~~ PSA: drivetrain wear
List of US/Canada bike co-ops ~~~ Global list
Thread
Thread Starter
Forum
Replies
Last Post
cwjDC
Classic & Vintage
6
02-29-16 06:04 AM
hellmean
Classic & Vintage
10
11-03-13 07:49 PM