7 sp to 8 sp Conversion
#1
Senior Member
Thread Starter
7 sp to 8 sp Conversion
Has anyone ever swapped their 7 sp Shimano cassette hub for an 8/9 sp one? If so, how did it work? I've got an older MTB with a 130mm spacing and was going to try it. I was wondering about dish and whether it would be too much on a 26" wheel.
#2
Banned.
Join Date: Dec 2007
Posts: 27,199
Mentioned: 34 Post(s)
Tagged: 1 Thread(s)
Quoted: 378 Post(s)
Liked 1,409 Times
in
909 Posts
7 to 8 is quite possible in road. I simply don't know about mtb. I doubt the dish is a big deal, and it can be redished.
My modifications are road bikes, and I've done it 2 ways:
1-Change a 7-sp freehub to an 8-sp freehub, redish and use a longer axle. I paid LBS $50 total for the change, including parts.
2-Swap out the rear wheel for a more modern one. This is by far the easiest. I generally pay $60-$125 for a wheelset, and sell the older set for $40-$75, sometimes up to $100.
My guess is that if you had a 130mm spaced rear, an 8-sp would fit right in there. I'm not sure when mtb's went to 135, but I don't think it was during the 8-sp era.
I'll yield to the older mtb guys here. You can PM roccobike, he knows that @#$%^& inside and out.
My modifications are road bikes, and I've done it 2 ways:
1-Change a 7-sp freehub to an 8-sp freehub, redish and use a longer axle. I paid LBS $50 total for the change, including parts.
2-Swap out the rear wheel for a more modern one. This is by far the easiest. I generally pay $60-$125 for a wheelset, and sell the older set for $40-$75, sometimes up to $100.
My guess is that if you had a 130mm spaced rear, an 8-sp would fit right in there. I'm not sure when mtb's went to 135, but I don't think it was during the 8-sp era.
I'll yield to the older mtb guys here. You can PM roccobike, he knows that @#$%^& inside and out.
#3
Bike Junkie
Join Date: Jun 2005
Location: South of Raleigh, North of New Hill, East of Harris Lake, NC
Posts: 9,622
Bikes: Specialized Tarmac, Specialized Roubaix, Giant OCR-C, Specialized Stumpjumper FSR, Stumpjumper Comp, 88 & 92Nishiki Ariel, 87 Centurion Ironman, 92 Paramount, 84 Nishiki Medalist
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 68 Post(s)
Likes: 0
Liked 37 Times
in
27 Posts
I've made the swap from 7 to 8 several times. It's not difficult. Your 26" wheel will be fine, but it will have to be redished. If you have a Shimano freehub, then the old one unbolts using a hex wrench (10mm I think) and the larger 8/9 speed bolts right in. If it's not Shimano, I can't comment. Some are compatible, some are not.
My only concern is the 130mm spacing in the frame. All the MTB conversions I've done were performed on frames with 135 spacing.
I recall reading a post here on BF the reason MTBs require 135 is due to the chain line being too close to the seat stay causing chain slap against the stay when riding on technical single track.
In theory, the change should work with a 130mm spacing because that's what road bikes have. But I've never made that change.
My only concern is the 130mm spacing in the frame. All the MTB conversions I've done were performed on frames with 135 spacing.
I recall reading a post here on BF the reason MTBs require 135 is due to the chain line being too close to the seat stay causing chain slap against the stay when riding on technical single track.
In theory, the change should work with a 130mm spacing because that's what road bikes have. But I've never made that change.
__________________
Roccobike BF Official Thread Terminator
Roccobike BF Official Thread Terminator
#4
Senior Member
Thread Starter
The bike has 130mm spacing now with a Deore 7 sp cassette. I already have the donor cassette hub with seals. I'm planning on using it more for a city MUP bike. So, there really won't be any rough riding on this one. The only reason I'm looking at 8 or 9 sp is because of the availablility of shifters and cassettes.
#5
Senior Member
Join Date: Dec 2005
Posts: 329
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
7sp parts are still readily available and very inexpensive. For a city bike, I would not recommend going up to an 8 - it's simply not worth it in my opinion.
Shift performance on 7sp index is so reliable and rock steady, even the cheapest triggers work really well. And you could hunt down some old 7sp thumbshifters if you want to!
Shift performance on 7sp index is so reliable and rock steady, even the cheapest triggers work really well. And you could hunt down some old 7sp thumbshifters if you want to!
#6
STFD
Join Date: Jul 2008
Location: North Bergen, NJ
Posts: 778
Bikes: '80 Windsor Carrera Sport, '02 Specialized Sirrus A1, '10 Giant Escape 2
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
I have an extra set of 7-speed indexed thumb shifters, if you need them.
#7
PanGalacticGargleBlaster
Join Date: Apr 2009
Location: Smugglers Notch, Vermont
Posts: 7,531
Bikes: Upright and Recumbent....too many to list, mostly Vintage.
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Likes: 0
Liked 5 Times
in
4 Posts
I've been torn looking at 7, 8 and 9 speed setups on ebay and it seems that right now 8 and 9 speed are more available and in many cases can be had cheaper than the 7 speed parts.
Don't forget, you can use 8 speed shifters with a 7 speed setup, Just adjust the limit screws properly.
Don't forget, you can use 8 speed shifters with a 7 speed setup, Just adjust the limit screws properly.
#8
Senior Member
Join Date: Dec 2005
Posts: 329
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Yes but brand new 7sp triggers start at $30 PER PAIR. Chains $10, freewheels $11, cassettes $15... you can build a very nice new drivetrain for very little money. THe only downside is that new 7 speed is not available in the higher trim levels - XT etc. -- but for city use even the entry level stuffis very reliable. For used/NOS you are probably right - 8 and 9 is easier to find!
According to sheldon, 7speed spacing is 5mm and 8 speed is 4.8 - it will probably work but not be ideal for proper indexing - you have to work harder to keep it in tune.
According to sheldon, 7speed spacing is 5mm and 8 speed is 4.8 - it will probably work but not be ideal for proper indexing - you have to work harder to keep it in tune.
#9
Thrifty Bill
Join Date: Jan 2008
Location: Mountains of Western NC
Posts: 23,525
Bikes: 86 Katakura Silk, 87 Prologue X2, 88 Cimarron LE, 1975 Sekai 4000 Professional, 73 Paramount, plus more
Mentioned: 96 Post(s)
Tagged: 0 Thread(s)
Quoted: 1236 Post(s)
Liked 964 Times
in
628 Posts
7 to 8 is quite possible in road. I simply don't know about mtb. I doubt the dish is a big deal, and it can be redished.
My modifications are road bikes, and I've done it 2 ways:
1-Change a 7-sp freehub to an 8-sp freehub, redish and use a longer axle. I paid LBS $50 total for the change, including parts.
2-Swap out the rear wheel for a more modern one. This is by far the easiest. I generally pay $60-$125 for a wheelset, and sell the older set for $40-$75, sometimes up to $100.
.
My modifications are road bikes, and I've done it 2 ways:
1-Change a 7-sp freehub to an 8-sp freehub, redish and use a longer axle. I paid LBS $50 total for the change, including parts.
2-Swap out the rear wheel for a more modern one. This is by far the easiest. I generally pay $60-$125 for a wheelset, and sell the older set for $40-$75, sometimes up to $100.
.
Good reliable 7 speed shifters are easy to find. I have used the Shimano Tourney ones sold by Niagara for $12 for several thrifty builds. They come complete with SIS housings and cables. Tough to beat!
https://www.niagaracycle.com/product_...ducts_id=15889
Last edited by wrk101; 11-26-09 at 10:37 AM.
#10
Senior Member
Thread Starter
Yes but brand new 7sp triggers start at $30 PER PAIR. Chains $10, freewheels $11, cassettes $15... you can build a very nice new drivetrain for very little money. THe only downside is that new 7 speed is not available in the higher trim levels - XT etc. -- but for city use even the entry level stuffis very reliable. For used/NOS you are probably right - 8 and 9 is easier to find!
According to sheldon, 7speed spacing is 5mm and 8 speed is 4.8 - it will probably work but not be ideal for proper indexing - you have to work harder to keep it in tune.
According to sheldon, 7speed spacing is 5mm and 8 speed is 4.8 - it will probably work but not be ideal for proper indexing - you have to work harder to keep it in tune.
#11
Senior Member
Join Date: Dec 2005
Posts: 329
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
How about this to "trick" 8 speed shifters into working on a 7 speed wheel... get an 8 speed cassette and blow the rivets out. Only put the smallest 7 sprockets on your existing freehub (use a spacer on the inside if necessary). Set your limit screws and tune the indexing based on top gear. The spacing will be correct and you'll be locked out of the lowest gear on the right hand side. Cost=cassette and shifters only. NBo worries about freehubs or wheel spacing.
Or get these: https://www.velo-orange.com/diacosibash.html :-)
Or get these: https://www.velo-orange.com/diacosibash.html :-)