Using 8 speed Shimano brifters on 7 speed Shimano freewheel?
06-11-14, 06:51 PM
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Using 8 speed Shimano brifters on 7 speed Shimano freewheel?
Project objective: Convert 6 speed to 7 speed (no further due to 125mm frame limit) . Swap downtube friction shifters for Brifters (hoping to use Shimano ST-2400s).
I've read many posts suggesting that I should be able to use 8 speed brifters on a 7 speed freewheel. I've also read many posts indicating that the different spacing between cogs - 5mm for the 7 speed and 4.8mm for the 8 speed - will result in less that precise shifting. So...I was wondering if anyone has attempted to rebuild a 7 speed cassette and replace the spacers. I believe the 7 speed spacers are 3.15mm. If one were to replace them with 3mm spacers, the difference would now be reduced from .2mm to .05mm.
Or is this a bit over the top? Any help would be greatly appreciated. Thanks.
I've read many posts suggesting that I should be able to use 8 speed brifters on a 7 speed freewheel. I've also read many posts indicating that the different spacing between cogs - 5mm for the 7 speed and 4.8mm for the 8 speed - will result in less that precise shifting. So...I was wondering if anyone has attempted to rebuild a 7 speed cassette and replace the spacers. I believe the 7 speed spacers are 3.15mm. If one were to replace them with 3mm spacers, the difference would now be reduced from .2mm to .05mm.
Or is this a bit over the top? Any help would be greatly appreciated. Thanks.
06-11-14, 06:59 PM
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I simply ran 8 speed shifters with a 7 speed HG cassette and it shifted fine. I dialed the RD to center on the 5th cog instead of the smallest.
06-11-14, 06:59 PM
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Over the top. Try it with a standard Shimano compatible 7 speed freewheel first. I've done it several times. And of course, why not buy a set of the new Tourney 7 speed STIs instead? My conversions were prior to the Tourney product. I now would go that way instead.
Shimano Tourney ST-A070 2 x 7-Speed STI Lever Set @ eBikeStop.com
Shimano Tourney ST-A070 2 x 7-Speed STI Lever Set @ eBikeStop.com
06-11-14, 07:59 PM
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I'm trying to talk myself into this configuration, but am concerned about alignment. Do they get more noisy as you move up to 7 or down to 1?
Last edited by Rickalodeon; 06-11-14 at 08:08 PM.
06-11-14, 08:02 PM
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Over the top. Try it with a standard Shimano compatible 7 speed freewheel first. I've done it several times. And of course, why not buy a set of the new Tourney 7 speed STIs instead? My conversions were prior to the Tourney product. I now would go that way instead.
Shimano Tourney ST-A070 2 x 7-Speed STI Lever Set @ eBikeStop.com
Shimano Tourney ST-A070 2 x 7-Speed STI Lever Set @ eBikeStop.com
06-11-14, 09:43 PM
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I am running 8 speed freewheels on a couple of my bikes with a 126mm spread with no problem. 8 speed freewheels aren't real common but they are around. I have a few more in case I want to use 8 speed brifters or dt shifters with freewheel hubs. You can keep the spread under 130mm with thin spacers.
06-12-14, 01:05 AM
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If you find that 8s shifters and 7s FW dont play nice together, try one of the alternate RD cable attachment locations in order slightly alter the pull ratio of the RD to increase travel of the RD with each of the slightly smaller 8s cable pulls. Read up on alternate cable anchors near bottom of page Derailer Adjustment
06-12-14, 04:40 AM
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I've done the 8 speed shifter with 7 speed freewheel or cassette on several commuter bikes with no problems at all. I ran my Super LeTour for over 10,000 miles with that exact setup, never adjusted the rear derailleur after the initial setup, all gears ran flawlessly.
06-12-14, 04:47 AM
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Done it with brifters and mtb bar shifters. Just tune out the top or bottom (I like the top to make sure it doesn't overshift) and the shifter doesn't care.
06-12-14, 05:14 AM
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You know... once I got my brain past the math, it occurred to me that the. 2mm difference amounts to less than 1/100 inch. WNG and Gray Jay - Thanks much for helping me come to my senses.
Also...a thank you shout out to wrk101, rjhammett, Kevin Stafford and krobinson103. I'm really looking forward to my vintage Univega upgrade.
Also...a thank you shout out to wrk101, rjhammett, Kevin Stafford and krobinson103. I'm really looking forward to my vintage Univega upgrade.
Last edited by Rickalodeon; 06-12-14 at 04:44 PM.
07-03-14, 05:29 AM
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... doing a bit of housekeeping and thought I should follow up and leave a note about the outcome of the aforementioned project. The new freewheel was tight, but fit with a little filing. I had to file the end of the screw (approx. 1mm) from the dropout adjuster.
Once the freewheel went in, the rest was a breeze. Shifting adjustment was easy and works perfectly. I was [sort of] ok with the downtube shifters, but am so happy that I made this upgrade.
Once the freewheel went in, the rest was a breeze. Shifting adjustment was easy and works perfectly. I was [sort of] ok with the downtube shifters, but am so happy that I made this upgrade.
07-03-14, 08:36 AM
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Rickalodeon, Feedback regarding a problem is always appreciated, thanks.
Brad
Brad
07-03-14, 01:37 PM
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In my experience, Shimano 8-speed shifters on a 7-speed cassette work indistinguishably from 7-speed shifters.
I wouldn't recommend this. The cable pull from the smallest cog to the next smallest is slightly greater than the rest to take up cable slack. It's harder to get good shifting if you don't start with the shifter in it's highest position. Just use limit screws to prevent shifting into the spokes.
I wouldn't recommend this. The cable pull from the smallest cog to the next smallest is slightly greater than the rest to take up cable slack. It's harder to get good shifting if you don't start with the shifter in it's highest position. Just use limit screws to prevent shifting into the spokes.
