Compatibility of Shimano Sora 8-Speed RL-400 Downtube Shifters
05-08-18, 07:05 AM
#1
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Compatibility of Shimano Sora 8-Speed RL-400 Downtube Shifters
I put these on an '85 Trek to use with an 8-Speed SRAM cassette and a Shimano RD-5800 11-Speed GS rear derailleur, but could not get the indexing to work smoothly, and that's the only option (no friction) on these shifters. Using this as FD.
A mechanic said the shifters, due to their "throw" and the rear derailleur were incompatible and suggested a mountain bike derailleur they had in stock, maybe an Acera or something like that, or to try to find an earlier model more appropriate Shimano, 105, Ultegra, etc.
I think he said Shimano changed the shifter throw angle some time ago and that's what causes the incompatibility with the newer derailleurs.
Can anyone tell me how to spot the compatible vs incompatible derailleurs? Is it to do with how the cable routes through the two points in the derailleur, the angle there? Or is it something like, just get ones made before some year?
I think I'll need a medium or long cage w/ a 32T low gear in the rear.
A mechanic said the shifters, due to their "throw" and the rear derailleur were incompatible and suggested a mountain bike derailleur they had in stock, maybe an Acera or something like that, or to try to find an earlier model more appropriate Shimano, 105, Ultegra, etc.
I think he said Shimano changed the shifter throw angle some time ago and that's what causes the incompatibility with the newer derailleurs.
Can anyone tell me how to spot the compatible vs incompatible derailleurs? Is it to do with how the cable routes through the two points in the derailleur, the angle there? Or is it something like, just get ones made before some year?
I think I'll need a medium or long cage w/ a 32T low gear in the rear.
05-08-18, 07:24 AM
#2
Senior Member
For your shifters any shimano road derailleur made for 7-10 speed should work okay (except 4700 series Tiagra). Shimano MTB derailleurs up to 9 speeds should also index with your shifters. You're right to get a medium or long cage for an 11-32 cassette.
Here's a good blog about Drivetrain Compatibility but my takeaway is that certain derailleurs are expecting the shifters to pull a certain amount of cable... so with the older shimano stuff all their derailleurs moved 1.7mm for every 1mm of cable pulled so that's why there is such a large amount of compatibility with the old shimano stuff but that system ran into limitations with 10 and 11 speeds so it's all been changed now.
Here's a good blog about Drivetrain Compatibility but my takeaway is that certain derailleurs are expecting the shifters to pull a certain amount of cable... so with the older shimano stuff all their derailleurs moved 1.7mm for every 1mm of cable pulled so that's why there is such a large amount of compatibility with the old shimano stuff but that system ran into limitations with 10 and 11 speeds so it's all been changed now.
05-08-18, 10:36 AM
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I've been riding rl400 shifters with acera rd and 8s 13/32 cassette with no issues, easy to adjust, cheap and zero maintenance.
05-08-18, 12:23 PM
#5
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Originally Posted by clasher
For your shifters any shimano road derailleur made for 7-10 speed should work okay (except 4700 series Tiagra). Shimano MTB derailleurs up to 9 speeds should also index with your shifters. You're right to get a medium or long cage for an 11-32 cassette.
Here's a good blog about Drivetrain Compatibility but my takeaway is that certain derailleurs are expecting the shifters to pull a certain amount of cable... so with the older shimano stuff all their derailleurs moved 1.7mm for every 1mm of cable pulled so that's why there is such a large amount of compatibility with the old shimano stuff but that system ran into limitations with 10 and 11 speeds so it's all been changed now.
Here's a good blog about Drivetrain Compatibility but my takeaway is that certain derailleurs are expecting the shifters to pull a certain amount of cable... so with the older shimano stuff all their derailleurs moved 1.7mm for every 1mm of cable pulled so that's why there is such a large amount of compatibility with the old shimano stuff but that system ran into limitations with 10 and 11 speeds so it's all been changed now.
Thanks all for the info. Thanks for the link @clasher, I really like Art's Cyclery's youtube channel as well.
I'll restrict my search to the above, I found an RD-5600 GS on ebay -- can anyone say if it will work with my shifters, 32T rear low gear, and FD choice above?
05-08-18, 12:38 PM
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Shimano recommends largest sprocket 27t max. They usually are very conservative.
05-08-18, 12:40 PM
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I'd recommend mtb rear der.
05-08-18, 01:07 PM
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That GS rear derailleur will work fine with a 28 tooth rear cog, and probably coild be made to work with a 30 tooth cog. A really talented person might be able to make it workable with a 32, but would be very dependent on bike, crank, rear dropout, etc.
On the other hand, any 7-8-9 speed Shimano Deore RD will easily hamdle a 32, and probably would do a 34 (at least it has done so on 4 or 5 bikes in my experience). So I'd go the easy/proven route.
On the other hand, any 7-8-9 speed Shimano Deore RD will easily hamdle a 32, and probably would do a 34 (at least it has done so on 4 or 5 bikes in my experience). So I'd go the easy/proven route.
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Last edited by rccardr; 05-08-18 at 01:24 PM.
05-08-18, 08:43 PM
#9
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Thanks, I think I'll go with this ...
RD 5701 GS - since I want a new one - and it seems to meet all of my needs, running a double.
https://www.ebay.com/itm/Shimano-105...r/112776287059
I found this which has some helpful info:
Shimano rear derailleur compatibility | cyclecycle.info
Another similar bike I have is using an MT-60 (which looks great) and is doing 8-speed shifting pretty well, though I think the lowest gear on it is 28T.
RD 5701 GS - since I want a new one - and it seems to meet all of my needs, running a double.
https://www.ebay.com/itm/Shimano-105...r/112776287059
I found this which has some helpful info:
Shimano rear derailleur compatibility | cyclecycle.info
Another similar bike I have is using an MT-60 (which looks great) and is doing 8-speed shifting pretty well, though I think the lowest gear on it is 28T.
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