Quick compatibility question

[srw]

Is an 8 speed Shimano shifter going to be compatible with a 7 speed derailleur and chain? A well-known online retailer doesn't admit to 8-speed derailleurs.

 

[theclaud]

Tell me you're not about to start major fettling on the bike for tomorrow's ride...

 

[winjim]

Cable pull's 0.1mm out.

http://blog.artscyclery.com/science...ce-behind-the-magic-drivetrain-compatibility/

 

[srw]

Tell me you're not about to start major fettling on the bike for tomorrow's ride...

I'm not about to start major fettling on the bike for tomorrow's ride.


That bike has 10-speed Ultegra. This bike has 8-speed bottom-of-the-range mountain bike gearing.

 

[srw]

Cable pull's 0.1mm out.

http://blog.artscyclery.com/science...ce-behind-the-magic-drivetrain-compatibility/

tarting with Shimano, this could be the simplest section of them all if we could just talk about everything up to 9-speed. Basically everything Shimano did up until then was cross compatible. They used a derailleur shift ratio of 1.7 on everything. While the cable pull varies from 8-speeds to 9-speeds as they moved the sprocket pitch closer together, the derailleur remains the same.

From which, and the 0.1mm difference (less than 1mm over the whole range), I think I take that it might not be perfect, but it's good enough.

There's a decent chance that before too long I'll replace the curent indexed brifters with separate brakes and unindexed shifters - I don't much like the straight handlebar brifter as a solution.

 

[gbb]

Is an 8 speed Shimano shifter going to be compatible with a 7 speed derailleur and chain? A well-known online retailer doesn't admit to 8-speed derailleurs.

8 speed ahifters/7 speed drive train work perfectly well together. Ive been running it on my Trek hybrid for several years.

 

[RecordAceFromNew]

Is an 8 speed Shimano shifter going to be compatible with a 7 speed derailleur and chain? A well-known online retailer doesn't admit to 8-speed derailleurs.

The answer is yes and yes. Shimano derailleurs have the same cable pull : traverse ratio for all 5/6/7/8/9 speed rear derailleurs made during the past 30 odd years, and 7 and 8 speed chains are the same thing.

The "small error" issue comes about only if you put an 8 speed cassette/wheel on a 7 speed setup or vice versa. The problem is usually hardly noticeable if you adjust cable tension by aligning the upper jockey wheel with one of the middle sprockets.

 

[Smurfy]

Is an 8 speed Shimano shifter going to be compatible with a 7 speed derailleur and chain? A well-known online retailer doesn't admit to 8-speed derailleurs.

Nearly all Shimano mechs give the same movement for a given cable pull, so that will not be an issue. It is the cassette spacing that has to match the shifter cable pull. For example, an 8 speed shifter will give the wrong amount of cable pull for a 7 speed cassette. If you have an 8 speed shifter and an 8 speed cassette it should be fine.

 

[fossyant]

It will work fine. The only one that won't is Dura Ace 7400 series. Wont work with any of the others !

 

[Smurfy]

If an eight speed shimano shifter is run with a 7 speed shimano cassette, and set up correctly on the 4th sprocket, the dérailleur movement will be 0.6mm short on the 1st and 7th sprockets. It's probably not enough to cause any additional noise, provided the adjustment is perfect when on the 4th sprocket.

 

[srw]

I've just realised. New chain means new cassette, doesn't it? Which since I've got a 9-speed derailleur means I might as well go for a 9-speed cassette. Which in turn means I'll need rather than just want replacement shifters.

Fettling starts tonight, with a good clean and strip-down. I've already managed to lose the bolt holding the hanger onto the frame - it pinged across the garage because I removed it from the frame before removing the derailleur from the hanger. Which means in turn that I'll need to clear out the garage at the weekend in the hope of finding it...

 

[velovoice]

I've just realised. New chain means new cassette, doesn't it?

Depends on how many chains you've gone through on this cassette and indeed if the cassette is showing signs of significant wear. You can usually go through 3-4 chains on one cassette before needing to change the cassette as well.