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8-speed shifter and derailleur with 7-speed sprocket?

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smmr89 Offline
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Posts: 5
Joined: Oct 2013
Post: #1
8-speed shifter and derailleur with 7-speed sprocket?
Hello

I'm new to this forum and tuning bikes in general. I bought a bike which has 8-speed on the shifter and the derailleur moves with the shifter to 8 positions of course. However there are 7 sprockets on the rear.

Is this a problem? While riding I do find that I can't use certain gears as the pedal clicks violently which is quite dangerous. So I've been staying in the safe-range (which is in the middle gears, or high for both front and back).

Is this fixable without having to buy anything else?

thanks would really appreciate anything on this - i can upload pics if required
Oct 31, 2013 06:23 AM
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nfmisso Offline
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San Jose, CA
Posts: 2,276
Joined: Jul 2010
Post: #2
RE: 8-speed shifter and derailleur with 7-speed sprocket?
not totally fixable without purchasing a 7 speed shifter or changing to an 8 speed cassette or freewheel.

7 and 8 speed spacing is very close, often a non-matching 7 <-> 8 system can be tuned fairly well. Follow Alex's instructions in "How to Adjust your rear derailleur" above.

Nigel
Oct 31, 2013 09:03 AM
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1FJEF Offline
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Northern Mexico (Central CA)
Posts: 617
Joined: May 2011
Post: #3
RE: 8-speed shifter and derailleur with 7-speed sprocket?
I think he has other issues too. That "I can't use certain gears as the pedal clicks violently" comment sounds like stretched chain, worn rear cluster, (seriously wrong chain line?) and maybe a rear derailer issue, either adjustment, wear or tension issue.
The other thing could be a shot shifter. I have a 7 speed grip shift that I have to tune like a friction shifter as the internal pawl is broken. It is only right in 1, 2 and 7th gear! Yeah, I know, replace it, I'm just accustomed to it, lol.
8 speed shifter on 7 rear gears is just as you have set it. 7th (small rear cog) is set with the RD cable slack, so that 8 on the shifter only gives more slack, for no change. 1st (largest cog) is set with shifter in 1.
RD adjust. Or here.
Measuring Chain Wear- go to the bottom of the page.
Oct 31, 2013 09:42 AM
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smmr89 Offline
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Posts: 5
Joined: Oct 2013
Post: #4
RE: 8-speed shifter and derailleur with 7-speed sprocket?
Thanks for all the replies!

(Oct 31, 2013 09:42 AM)1FJEF Wrote:  I think he has other issues too. That "I can't use certain gears as the pedal clicks violently" comment sounds like stretched chain, worn rear cluster, (seriously wrong chain line?) and maybe a rear derailer issue, either adjustment, wear or tension issue.

Hmm this sounds complicated. I bought the bike for £15 off ebay and there was a lot to repair (enjoyable at the same time). Since, I've learnt that the bike was manufactured by SJS Cycles as a winter-racing bike about 10 years ago http://www.sjscycles.co.uk/

The frame is awesome, I love it. It is plain silver with no decals at all, except for a humble SJS Cycles stamp on stem below the seat!

(Oct 31, 2013 09:42 AM)1FJEF Wrote:  8 speed shifter on 7 rear gears is just as you have set it. 7th (small rear cog) is set with the RD cable slack, so that 8 on the shifter only gives more slack, for no change. 1st (largest cog) is set with shifter in 1.
RD adjust. Or here.
Measuring Chain Wear- go to the bottom of the page.

Thanks for this - it works exactly as you said. Now my 7th and 8th gear on my shifter is exactly the same because 8 simply gives more slack.

Struggling with the front derailleur now and from reading things online, I could be behind it for a very long time! It's a Shimano C101 at the front..!
Oct 31, 2013 02:30 PM
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1FJEF Offline
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Northern Mexico (Central CA)
Posts: 617
Joined: May 2011
Post: #5
RE: 8-speed shifter and derailleur with 7-speed sprocket?
Your link doesn't give a picture of the bike. Adjusting the front derailer is easy.
Oct 31, 2013 03:54 PM
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smmr89 Offline
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Posts: 5
Joined: Oct 2013
Post: #6
RE: 8-speed shifter and derailleur with 7-speed sprocket?
got the front derailleur working awesome now, rode the bike last night and all was smooth.

I'll post some pics of the bike later. They're not going to be on the website though as it is a really old bike, but it's the same company.
Nov 1, 2013 02:30 AM
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smmr89 Offline
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Posts: 5
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Post: #7
RE: 8-speed shifter and derailleur with 7-speed sprocket?
Nov 1, 2013 05:47 PM
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painkiller Offline
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Peoria, IL. USA
Posts: 1,383
Joined: Mar 2011
Post: #8
RE: 8-speed shifter and derailleur with 7-speed sprocket?
(Nov 1, 2013 05:47 PM)smmr89 Wrote:  here's the pics of the bike: http://forums.bicycletutor.com/thread-5318.html

Not a bad looking bike mate.


There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
Nov 2, 2013 05:54 AM
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1FJEF Offline
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Northern Mexico (Central CA)
Posts: 617
Joined: May 2011
Post: #9
RE: 8-speed shifter and derailleur with 7-speed sprocket?
(Oct 31, 2013 06:23 AM)smmr89 Wrote:  Is this a problem? While riding I do find that I can't use certain gears as the pedal clicks violently which is quite dangerous. So I've been staying in the safe-range (which is in the middle gears, or high for both front and back).
That reminded me, so I went & tried my old bike with non indexed gears and chain. It will skitter across the gears if you pedal hard & slam the shifter across the gears. This is only when shifting, & especially over shifting at low speed.
Did your chain slip & skip stop?
Nov 3, 2013 01:18 AM
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