Shimano R8000 FD compatible with 5800?

[flat tyre]

I've got one bike with 5800 11sp groupset and another with R8000 11sp. I have to say that the R8000 is a huge improvement over the 5800 particularly as far as the front derailleur set up and operation is concerned. The 5800 is a bit of a pig to set up and no matter how hard I try there isn't much flexibility on the FD with chain rub occurring 2-3 cassette rings before the extreme limit (i.e.big/big, or small small). So, I thought I might achieve a fix by swapping the FD, but now I think that even if 5800 will work with R8000 FD it won't have cured the problem because there may be a difference in the chain ring spacing between the 2 groupsets. Anyone know anything about this?

[gregoryoftours]

I don't know about the various specs but those are gears that you really shouldn't be using anyway. Big/big small/small are the absolute extremes but even 1 or 2 cogs in gives a bad chain-line. Very similar ratios can be achieved using a different ring with a much better chain-line. In any case often with a road chainset the smallest 2 or 3 cogs used with the small ring will cause the chain to catch on the pickup ramps of the big ring. Have you also set up your front mech to work correctly with the front shifter trim positions, i.e. the small clicks that are designed to adjust the position of the front mech to stop rubbing but not to change gear?

[Brucey]

according to the shimano compatibility charts FD-R8000 etc is backwardly compatible and can be used with 5800 series shifters and cranksets. However what they don't advise is that you use FD-5800 with a newer crankset.

I think the issue is that the chainline is slightly different on the newer groupsets, and this means FD-5800 won't have the correct shift ratio (which varies with chainline). But then on a lot of framesets it doesn't have the correct shift ratio anyway, hence the oft-experienced trimming issues.

FWIW I think that if you can get FD-5800 to work then it might be a better mech in the long run, simply because it is less complicated, easier to clean, and (probably) less likely to get clogged up with grot. But if you can't get it to work well then the more complex FD-R7000 or FD-R8000 mechs can usually be made to work better in most cases. But they are more complex and ought to be more vulnerable to getting filled up with muck and rubbish.

Arguably FD-5800 etc could have been made to work better if shimano had installed a disc in the pinch bolt with a cable peg on it, that could be positioned in about a dozen different places (and therefore manage the shift ratio of the mech better); two cable positions just isn't enough to allow it to work with every cable run and small variation in chainline vs the mech mounting.

cheers

[Samuel D]

I've got one bike with 5800 11sp groupset and another with R8000 11sp. I have to say that the R8000 is a huge improvement over the 5800 particularly as far as the front derailleur set up and operation is concerned.

Really? I’ve found the opposite. It takes two minutes to nail an FD-5800 or similar. It takes two minutes just to untangle the cap and cable loop mess on an FD-R8000 before you start the multi-step process of adjusting it with microscopic Allen keys; that is, once you’ve dug the microscopic screws out of the road grime and freed up the microscopic pivots and levers. You can’t flick the screw head clear of muck with an Allen key as you could with a flat-blade screwdriver on earlier models. You have to dig a hole with a pick or scriber. The whole thing appears to be designed for use in a cleanroom.

Trim problems with STI shifting are usually from not following the Shimano set-up instructions precisely, in my experience. A random YouTube video is not a good substitute for this document (PDF). For a start, with the long-lever front derailleurs you need to measure the incoming cable angle with the Shimano TL-FD68 tool or equivalent.

[flat tyre]

Thanks for replies. I think maybe I might just spare myself the bother and stick with the 5800 FD on the 5800 groupset bike! I tend to agree that the R8000 looks a bit like a watchmenders nightmare, it does however in my experience seem to give more flexibility with chainring/cassette ring extreme combinations.

[Samuel D]

I haven’t measured them, but I’ve noticed the cage on the new toggle-link derailleurs appears to be both wider and to have a shorter tail. That should indeed provide more flexibility with chain angle before rub happens.

That said, the trim works better on Shimano systems if you meticulously follow the set-up instructions. I see a fair few road bikes and not many of them – fewer than 1 in 4 by my reckoning - are set up exactly right in the front derailleur. This is probably the trickiest adjustment of modern bikes. Not saying that’s your case, but it’s worth checking your FD-5800 set-up against the Shimano PDF I linked to.

Another thing: I missed your question about chainring spacing, but Shimano has indeed made the gap between the chainrings greater on newer groups, I think from the series starting with R (e.g. R8000, R7000). I believe that’s to better allow small-small gears with short chainstays and 135 mm OLN distance frames. But if your problem was chainring spacing, the chain would rub against the inner side of the large chainring, snagging the shifting aids. That’s a little different from derailleur cage rub or fiddly trim set-up.

[ElCani]

Can anyone tell me what was wrong with the pre long-arm designs? Piece of p*ss to set up and worked absolutely fine. My DA 7900 double takes 2 minutes even though there’s no cable adjuster anywhere in the cable run.

[Samuel D]

Can anyone tell me what was wrong with the pre long-arm designs?

Pass.

[Brucey]

Can anyone tell me what was wrong with the pre long-arm designs?

Pass.

short cable pull, high tension, against the whole ethos of modern cable designs...? (who cares about whether it works or not...)

FWIW I have occasionally seen the 'slow helix' turn into a much faster helix in SIS housing, where the bike has been stored with the FD cable under tension against the limit screw.

cheers

[flat tyre]

I've got one bike with 5800 11sp groupset and another with R8000 11sp. I have to say that the R8000 is a huge improvement over the 5800 particularly as far as the front derailleur set up and operation is concerned.

Really? I’ve found the opposite. It takes two minutes to nail an FD-5800 or similar. It takes two minutes just to untangle the cap and cable loop mess on an FD-R8000 before you start the multi-step process of adjusting it with microscopic Allen keys; that is, once you’ve dug the microscopic screws out of the road grime and freed up the microscopic pivots and levers. You can’t flick the screw head clear of muck with an Allen key as you could with a flat-blade screwdriver on earlier models. You have to dig a hole with a pick or scriber. The whole thing appears to be designed for use in a cleanroom.

Trim problems with STI shifting are usually from not following the Shimano set-up instructions precisely, in my experience. A random YouTube video is not a good substitute for this document (PDF). For a start, with the long-lever front derailleurs you need to measure the incoming cable angle with the Shimano TL-FD68 tool or equivalent.

Thanks, I used the manual you have linked to when I originally installed the FD, having read it again I remembered that there is a cable routing converter that needs to be positioned according to the indication on the alignment tool. I seem to have lost the original alignment tool but my recollection was that it wasn't a precise indication so I might try the alternative converter position to see if that improves the situation.

[Brucey]

you can buy TL-FD68 quite cheaply eg on ebay. Busy bike shops may have surplus gauges of this type because they were shipped with every such mech originally.

But like you say there are only two positions, so it is not that difficult to try them both.

If you know what you are doing, it ought to be possible to fangle a converter to suit even a frame where the cable routing doesn't suit either of the two positions.

cheers

[Samuel D]

Sometimes the bottom bracket cable guide has a bit of wiggle room that can be used to improve the entry angle of the cable to the derailleur, too. Doesn’t apply to frames with internal routing.