Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

Another chain question for 6-7 speed swap

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.

Another chain question for 6-7 speed swap

Reply

Old 02-03-19, 10:04 AM
  #1  
sd5782
Senior Member
Thread Starter
 
Join Date: Jan 2019
Location: Toledo Ohio
Posts: 74

Bikes: 1970s Schwinn SuperSport 1985 Centurion Ironman 1991 Bianchi Boardwalk Hybrid 1964 Huffeigh Sportsman 3 speed

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 48 Post(s)
Another chain question for 6-7 speed swap

I tried to do a bit of searching and I think I know the answer is a new chain. On a recent 85 Centurion purchase, I just switched out the freewheel from the stock 13-24 6 speed to a Sunrace 13-25 7 speed. Easy swap and fit. A bit of noise and no chain stay rub. Measuring things, the 7 speed cluster has slightly closer spacing of the chain sprockets. Kinda hard to tell, but I think the chain rivets may hit the teeth of adjacent gears.

I know a new chain is recommended with a new sprocket anyhow, and is cheap also. I will look around and see what is available locally. Research says perhaps an 8 speed, and maybe the Sram 850?
Am I on the correct path? Thanks.
Steve
sd5782 is online now  
Reply With Quote
Old 02-03-19, 10:11 AM
  #2  
delbiker1 
Senior Member
 
delbiker1's Avatar
 
Join Date: Mar 2016
Location: Sussex County, Delaware
Posts: 361

Bikes: 1991 Ochsner steel frame, 2002 Airborne Zeppelin titanium, Schwinn DBX SS aluminum, Orbea MD 40 carbon fiber

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 92 Post(s)
850 will work fine. I use the Sram 830 and it works smoothly. I think it is a bit cheaper. I believe I get those from www.bikewagon.com
delbiker1 is online now  
Reply With Quote
Old 02-03-19, 03:29 PM
  #3  
SurferRosa
Senior Member
 
SurferRosa's Avatar
 
Join Date: Dec 2018
Posts: 452

Bikes: old school roadies

Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 184 Post(s)
I often find a 9-speed chain shifts quicker and more quietly on 7-speed freewheels. I just bought one for this exact reason, a kmc x9.93 from ebay. The freewheel is a sunrace 7.

I have another bike with a sram pc-850 and a sunrace 7-speed. It shifts great, too, or i would have mounted a 9-speed chain on it as well.
SurferRosa is offline  
Reply With Quote
Old 02-03-19, 04:18 PM
  #4  
oliver1850
Member
 
Join Date: Oct 2011
Posts: 28
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
I've also had good luck with 9 speed chains on 6,7,8 speed bikes. Bought a bunch of HG53 and HG73 a few years back, been my go-to ever since.
oliver1850 is offline  
Reply With Quote
Old 02-03-19, 04:33 PM
  #5  
Bill Kapaun
Senior Member
 
Bill Kapaun's Avatar
 
Join Date: Feb 2007
Location: Mid Willamette Valley, Orygun
Posts: 10,591

Bikes: 86 RockHopper,2008 Specialized Globe. Both upgraded to 9 speeds.

Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 595 Post(s)
I've used 9 speed chain on an old cottered double when experimenting with crank length for my bad knees.
It worked fine.
I'd still toss on a 7 speed chain on a 7 speed rear. It's simply stronger than 9 speed chain of equal quality.
Bill Kapaun is offline  
Reply With Quote
Old 02-03-19, 05:33 PM
  #6  
sd5782
Senior Member
Thread Starter
 
Join Date: Jan 2019
Location: Toledo Ohio
Posts: 74

Bikes: 1970s Schwinn SuperSport 1985 Centurion Ironman 1991 Bianchi Boardwalk Hybrid 1964 Huffeigh Sportsman 3 speed

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 48 Post(s)
Thanks for the replies. May try a 9 speed to be on the safe side first
sd5782 is online now  
Reply With Quote
Old 02-03-19, 09:23 PM
  #7  
Ironfish653
Senior Member
 
Join Date: Oct 2015
Location: Virginia Beach
Posts: 818

Bikes: 1997 Cannondale, 1976 Bridgestone, 1998 Softride

Mentioned: 12 Post(s)
Tagged: 0 Thread(s)
Quoted: 264 Post(s)
SRAM 8xx-series are good, the only real difference between them is silver or gray finish.

KMC Z-51 is a go to when i'm building a 5-7sp with a mix-n-match of modern and vintage stuff. Plus my co-op has them for $9.99
Ironfish653 is offline  
Reply With Quote
Old 02-11-19, 07:59 AM
  #8  
sd5782
Senior Member
Thread Starter
 
Join Date: Jan 2019
Location: Toledo Ohio
Posts: 74

Bikes: 1970s Schwinn SuperSport 1985 Centurion Ironman 1991 Bianchi Boardwalk Hybrid 1964 Huffeigh Sportsman 3 speed

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 48 Post(s)
Okay, Some observations. This new Sunrace 7 speed is from the little I know, a copy of a Shimano; perhaps a HG. The teeth have a bend to them. With the stock chain, the pins could hit adjacent teeth. It was more obvious in the smaller gears. Stock chain width across the pins is about 7.5mm. The sram 8XX that are recommended are 7.1mm across the pins. I put one on my old Schwinn SuperSport when I converted the rear to a 6 speed, so I measured the one I have. It would probably work fine.

So, wanting to patronize my LBS, I went there. They sold me a Shimano HG 7 speed chain. I measured it across the pins at 7.4mm, so I was not going to even try it. The Sram was 7.1 while the Shimano was 7.4 for a 7 speed. Interesting. I researched Shimano chains, still wanting to patronize my LBS and got the HG53 which is 6.5mm across the pins. All seems well with no pins hitting adjacent teeth. Snow on the ground here, so only shifted (friction) on a stand, and all seemed fine.

I think the chain on it was the original and is 108 links. I kept the same chain length. Sprocket changes were a 24 to 25 increase in rear, and a 39T small in front to replace the 42T. Big big and small small seems fine although chain calculators say I want 104 links vs the 108 on it. Sure would like to see some spring weather.
sd5782 is online now  
Reply With Quote
Old 02-11-19, 01:10 PM
  #9  
ramzilla
Senior Member
 
ramzilla's Avatar
 
Join Date: Dec 2014
Location: 1/2 Atlanta GA 1/2 Fernandina FL
Posts: 2,334

Bikes: Vintage Japanese Bicycles

Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 367 Post(s)
My go to chain for all 5, 6, 7, & 8 speed bikes is the KMC x8.93. You can usually get a pretty good deal on them and, they work just fine on 7 speed set ups. I like the KMC master link too. Shimano chains are too fussy with the drive pin thingy.
ramzilla is offline  
Reply With Quote
Old 02-11-19, 01:40 PM
  #10  
sd5782
Senior Member
Thread Starter
 
Join Date: Jan 2019
Location: Toledo Ohio
Posts: 74

Bikes: 1970s Schwinn SuperSport 1985 Centurion Ironman 1991 Bianchi Boardwalk Hybrid 1964 Huffeigh Sportsman 3 speed

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 48 Post(s)
yep

Originally Posted by ramzilla View Post
My go to chain for all 5, 6, 7, & 8 speed bikes is the KMC x8.93. You can usually get a pretty good deal on them and, they work just fine on 7 speed set ups. I like the KMC master link too. Shimano chains are too fussy with the drive pin thingy.
I did not really like the Shimano pin setup either. I did want to patronize my LBS however. I have 4 tires ordered also. Probably with all the stuff I bought, I spent maybe an extra $40 locally, but I was fine with that since I was supporting a small local shop.
sd5782 is online now  
Reply With Quote

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


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service