I bought a used Cervelo S3 about 2 years ago. I have used it 90% of the time on the trainer in erg mode and never really used the gears. The few times I have used it I have had problems with the front derailleur not working properly. And recently while trying to adjust it I realized that the front derailleur is Shimano Ultegra but the rest of the groupset is SRAM Red. 2x10. The internet told med that mixing and matching brands like this will not work (in all cases). So I think I’m going to replace the front derailleur with a new one. The problem is that I cannot find a 10speed mechanical front derailleur. (I live in Norway btw) Can I use a Force/Rival 2x11 front derailleur?
Hi assuming you are talking about mechanical Sram and mechanical Shimano
There was a time where the Sram Red front derailleur wasn’t very good, it was difficult to align and overly flexible. Many riders would change it out for the Force version as it wasn’t as flexible. I suspect that the previous owner likely did the same, but went with Shimano.
I would first check to make sure its setup right, but if you want to convert it back to Sram, Rival or Force will work with no challenges.
Yes. I assume you mean you’re using the 2-speed front shifter on a 10sp drivetrain. You can even do a Shimano FD, which might work better.
Basically, everything SRAM works for everything road-to-road and MTB-to-MTB. I think you can run a 9sp RD with a 12sp cassette.
Front derailleurs are friction shifting, not indexed, so they are largely compatible with other brands.
Yes, you can use a FD from an 11-speed groupset - it doesn’t care much how many gears you have at the back.
I have not seen a friction shifter on a bike in the last 25 years. Well maybe a few but FD are indexed.
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Well, I said front derailleurs, not shifters…but even the above is not really true. Front shifters may be “click and release”, but they are not indexed in the way rear derailleurs / shifters are. When you go form the small to the big chainring, the movement is a friction shift, not indexed.
However, chain width can play into this…you can run into situations where you get FD / chain rub that can’t be eliminated if you are using a narrower FD vs. the chain.
By that logic rear derailleurs are not indexed. It is the shifter that moves the cable (non electronic ) a specific amount to move the cage to match the spacing on the cogs.
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No, it really isn’t the same thing as RD’s are designed very specifically for use with its compatible shifter. This is not the case with FD’s / shifters.
ETA - but yes, you can use any RD in friction mode. I currently use a Campag 10 spd RD with a friction DT shifter.
My sram TT shifter would be friction for the FD if I had a FD. Shimano has some that are switchable so the front is friction and the rear is either.
Yes, I was debating if I had to elaborate on that, but then decided that there likely isn’t much between 9/10/11 speed FDs. 12 speed I’d steer clear off, too much has changed.
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Yes its mechanical 2x10 Sram Red everything except for the front derailleur. So I am currently using a Shimano FD and I never got it to work properly. And I believe it’s because Shimano and Sram shifters have different amount of cable pull? Does Sram 11 speed shifters have the same amount of cable pull as the 10 speed shifters?
The front doesn’t really care, since it’s a two position thing and the cable pull is close enough.
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I remember when I was using SRAM Red 10 speed I ended swapping the Red front derailleur to Shimano Dura Ace and for me it worked much better.
My advice would be, since you already have that Ultegra front derailleur, keep using that one and you will be surprised at how well it works.
I thought there’d be at least one “sram front derailleurs don’t work with any shifters” comment 
I’m disappointed.
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But….there is one now. 
Most TT bikes have friction shifters for the front…at least mine does! 
I think the point that was missed is that derailleurs are not indexed. It is the shifters that provide the indexing. To the original post. It most likely is not going to matter. I don’t have the specs on the spacing between chainrings on a 10sp vs 11sp, or 12 for that matter. I doubt there is enough difference that if you used one in place of the other it would impact shifting. It is the shifter that is that pulls the cable the amount needed to move the derailleurs. This is the same for the front and the rear. They have set screws that limit the movement at low and high side. If you manually move the derailleurs there is not indexing. Or I have never seen one or felt one that does. The original post does not say anything about the S3 being setup as a TT bike. I know we are splitting hairs but I felt that it is the statement “Front derailleurs are friction shifting, not indexed” is not clear.
Not really that important as long as it shifts when you want it to. I doubt there are many here that could ride a bike with 100 friction shifting and do it smoothly. I personally would never want to go back.
Thanks. Yeah the indexing is done by the shifter, and I agree that there probably is only a negligible difference between 10s and 11s chainring spacing.
The issue for me is that I need to choose between chainrub on either the smallest or biggest cogs on my cassette because the FD will not move “enough” (I’ve checked the limit screws). And I think that’s because Shimano FDs require more cable pull than Sram FDs. (Theory: Sram shifters pull less cable than Shimano shifters) I ordered a 11s Sram FD yesterday and hopefully this will work with my shifter. I’m tired of choosing between being able to climb or going fast (in silence).
Also I realized I have an S2. Not set up as a TT bike at all.