Crank/chainring compatibility 105 5800 vs R7000

[MrSlower]

Hi,
I have my old TCR,105 5800, setup on my turbo and need to change it to 170mm cranks to match my road setup.
I am having trouble in sourcing 170mm 5800 cranks so was wondering can I use 7000 cranks and swap out my existing 5800 chain rings onto the new cranks?
I think the inner chain ring spacing on the 7000 is different to the 5800 so if I can swap the chainrings out it saves me having to buy a 7000 front derailleur.

Thanks in advance.

 

[si_c]

Spoiler: This is wrong.

Pretty sure the chainring compatibility is OK - I've fitted Tiagra and R7000 chainrings across different cranksets and the Tiagra ones are a match for 5800. Sadly I no longer have my 5800 cranks to double check.

The rings are shaped slightly where they meet the crankarms so may need a bit of wiggle to get them to fit at a guess. More noticeably you may see a difference with the aesthetics of the cranks with the height of the arms meeting the rings being different.

 

[roubaixtuesday]

I have used R7000 outer chainring on a 5800 spider, having bought one in error.

They are useable, but it looks a bit odd because the R7000 has a shaped section on one arm.

I *think* it would NOT work the other way around which you need - I presume the R7000 spider would would the corresponding arm of the 5800 chainring.

5800 Chainring:

7000 Chainring, difference ringed:

 

[si_c]

I have used R7000 outer chainring on a 5800 spider, having bought one in error.

They are useable, but it looks a bit odd because the R7000 has a shaped section on one arm.

I *think* it would NOT work the other way around which you need - I presume the R7000 spider would would the corresponding arm of the 5800 chainring.

5800 Chainring:
View attachment 754506

7000 Chainring, difference ringed:


View attachment 754507

That makes sense to me, I knew there was a change to the ring shape, but I'd always used R7000 rings on a 5800 type crankset, not the other way around. So clearly my comment above isn't correct, so I'll remove it.

 

[MrSlower]

Looks like ill need a full 7000 chain set and FD.

Thanks for your help

 

[roubaixtuesday]

Looks like ill need a full 7000 chain set and FD.

Thanks for your help

I think the FD will still work.

 

[MrSlower]

I think I read somewhere that the 7000 chainring spacing is different to 5800 and the inner ring is a fraction closer inboard and it rubs on the 5800 FD. Ill try first but if it does rub ill bite the bullet Its only £20 for a new FD.

Thanks

 

[MrSlower]

7000 chainring was fitted and works great on the turbo without changing the FD.

Thanks for your help