105 5800 and R7000 Crankset Compatibility

Jackofallgrades

Hi all, considering investing in a set of 105 5800, but struggle to find crank lengths of 165mm, though they are relatively available in the new R7000 guise, so was thinking of just swapping in a R7000 crankset with the rest of the groupset being 5800. Having looked around on here it seems most don’t have any problems swapping different cranksets around even between different manufacturers, so long as BB compatibility is ok. However I came across this in an article comparing 5800 and R7000:

“Shimano has also repositioned the inner ring so that it reduces the effects of cross chaining, which could make the difference for those who race but don’t want to fork out for Ultegra. It does however, make the rings no longer compatible with the old front derailleur design.”

https://www.google.co.uk/amp/s/www.cycl ... 374671/amp

Has anyone tried this? Would I need a R7000 front derailleur to go with the crankset if I did this?

akh

I believe the difference is less than 1mm, it won't cause any major issues. You might get a tiny bit of chain rub on the front derailleur cage at extreme angles. If that happens, spending 25 quid on a R7000 front derailleur should solve that problem. The levers and derailleurs are fully interchangeable.

Jackofallgrades

Thanks AKH, will give it a go.

philbar72

minimal on these chainsets. same with all last gen vs current gen chainsets. tiny bit of chain rub in 11 and 12 when unadjusted for me.
can be dialled out no problem.

mgrievedecor8

Hi jackofalltrades. How did you get on with the front derailleur?
I have just purchased the 105 r7000 semi compact crank set as currently running the old 5800 compact. I read the same quote as you earlier and suddenly thought I might need to buy a new derailleur too.

arlowood

Jackofallgrades said:

Thanks AKH, will give it a go.

mgrievedecor8 said:

Hi jackofalltrades. How did you get on with the front derailleur?
I have just purchased the 105 r7000 semi compact crank set as currently running the old 5800 compact. I read the same quote as you earlier and suddenly thought I might need to buy a new derailleur too.

To both - I would definitely fork out the extra dosh and fit the 7000 front derailleur. This is the new design (similar to Ultegra 8000) which incorporates a cable tension gizmo into the derailleur mechanism. Infinitely preferable to the old FD designs where it was almost impossible to set them up correctly without a cable stop or in-line barrel adjuster on the FD cable.

cq20

Bit of a late addition to this. I’ve fitted a R7000 chainset in place of my 5800 (various bits moving down the food chain) and have had to make no changes to the 5800 front derailleur set up. Everything works fine and no chain rub. Mind you the FD does have an in-line adjuster and took an age to setup initially