N1CKV

I have a friend that has a partial 105 11s groupset (from Domane SL5) he's willing to part with. My bike is a 2020 Trek Domane AL2 (Claris 2X8s).
He has the brifters and rear derailleur that I could use. Both bikes are caliper brakes, I plan to keep mine as I have not real complaint.
His front derailleur is braze on, mine is clamp on so I cannot use that. He kept his 105 crankset.
Along with what he has, I know I will need an 11s chain and cassette at the minimum.

Can I keep my Claris front derailleur, crankset and chain rings, at least for now? I would have to also change my bottom bracket (currently square taper) to upgrade, and I would rather do this later if possible.
Can I reuse my cables (brake and shift)? I have never messed with bar tape, can it be reused? My bike is fairly new so these items are in great shape.

The purpose of the move to 11s would be to get a more optimal cadence in a pace line, the ~15+ rpm difference between gears is not ideal when I don't get to pick the exact pace.
If I can avoid messing with the crankset / FD I could save funds on this conversion for the time being, later I would consider upgrading that to 105 with a power meter.
One thing to note: I never use my smaller crank gear, where I live it is very flat.
In fact my other alternative would be swapping my 8s 11-32t cassette to a 11-28t, but I would like the flexibility to have gearing in the future for hilly terrain a little north of my area.

Thoughts?

himespau 

There's a chance you might need to buy new wheels, which would make the change pricey.

N1CKV

I am not against changing wheels, but my friend said my wheels are identical to what came on his SL5 so it likely is not a problem and worst case we could swap (he changed to carbon wheels). My understanding is that the 8s cassette uses a spacer to make up the difference between it and the 9-11s. Wheels were another upgrade I was looking at anyway, doing that at the same time would delay me because of budget, but definitely not a deal breaker.

Tacoenthusiast

The groupset change doesn't seem worth it, especially since you would really only be changing the rear derailleur and shifters



Just get a new cassette with tighter ratios, you can keep your current cassette and change back in about 5minutes

N1CKV

Swapping to a 11-28T cassette was my original plan. It's much cheaper, and I guess I can easily enough swap back to the original 11-32T if I'm going anywhere that hills may be an issue.
I was just looking at how much trouble it would be to get to a 105 groupset, I know my original plan is only halfway getting there, but I would eventually finish the front part if I could defer it.
It's just not in the budget or practical to swap the full groupset at the cost of all new parts (I would be more inclined to just trade up to a higher level bike).

topflightpro

Front derailleur should work. It may not work great, but it should work.

As already stated, you may need to change your wheels. You may have the same rims as your friend, but the freehub might not be accept an 11-speed cassette.

And there is a good chance you will need to replace your crankset. I'm not sure how well an 11-speed chain will sit on 8-speed rings. And even if you went to 11-speed chainrings, they may end up being spaced far enough apart that the chain can drop between them.

Granted, I've not tried any of these upgrades or changes, so it's just speculation on my part, but things to keep in mind.

ridethecliche

I would not reuse that crankset. Additionally, the R7000 FD isn't that much.

You can buy a new R7000 group for like 500 bucks so the price better be right...especially if it's 5800. The new R7000 stuff is very very good.

I'd test fit the 11 speed cassette on your wheels first if you want to make sure that aspect of things will work out okay.

trainsktg

As long as the cables aren’t too short after the swap or mangled at the derailleur ends, they can be reused, as can the cable housings and bar tape, unless the bar tape tears itself apart as you try to unravel it. Of note regarding the cables tho’, the cable ends inside of internally routed Shimano shifters (cables routed under the bartape) will eventually fray and stop up the works of the shifter, especially the rear shifter. It’s a known issue and Shimano recommends periodic replacement of the cables for this very reason. Check those cable ends before reuse and replace if you see any fraying.

Keith