Just asking because I noticed the front RS3 on my 2103 is almost at the wear bars, but the rear looks like it might have a few thousand miles left.  This is with less than 5000 miles on the tires.  I know the C14 has a reputation for being hard on front tires, but c'mon. 

I'd rather not put another RS3 on the front, but I would also not like to replace the rear RS3 at this time. 

TIA

The Z8 is a previous generation tyre. It's from the PR3 generation.
The current Metzeler ST tyre is the Roadtec 01.

You can put any modern radial tyre on the front with your RS3 rear.
I'd opt for a PR4GT, PR5GT or an Angel GT2.

I currently hace a Roadtec Z8 Interact M-Spec Front on my R1200RT with a Michelin Pilot Road 5 on the rear. Too soon to report on mileage but handles and grips well.

Thanks for the advice, guys.  Up until now I've been very pleased with Dunlop's.  I've had a few Metzler's and Pirelli's on other bikes, but for whatever reason not too interested in Michelin's.  The bike had PR4GT's on it when I got it, and while they were worn-but not worn out, I couldn't wait to replace them.  As the saying goes, YMMV.
 

Thanks for the advice, guys.  Up until now I've been very pleased with Dunlop's.  I've had a few Metzler's and Pirelli's on other bikes, but for whatever reason not too interested in Michelin's.  The bike had PR4GT's on it when I got it, and while they were worn-but not worn out, I couldn't wait to replace them.  As the saying goes, YMMV.

I have not been a Michelin PR fan since PR2 but the PR5 looks different from 3 and 4, looks a lot like the Pilot Power RS I run on my track bike. So far n0 complaints except for the high price. If I get 12000 miles I will be happy. But of course the RT does not have the power or weight of the Concours.

I don't know about everyone else, but I prefer for my tires to match front to back.  Profiles that were meant to be together always seem to feel better to me.

I've had to mix tyres on my C10 since Michelin stopped making the 150/80-R16 rear size for the C10.
I dislike the Avon front tyres and their rear is the only zero degree radial available in that size.
My fave combo on the C10 is the Avon 3D-XM rear and a Michelin PR3 front.
My next combo will be the Avon Spirit rear and PR3 front but I may try the Spirit front.

On the C14 I am currently running a PR4 front and a PR4GT rear (55 ratio) and that combination handles superbly.

If you mix older radials with zero degree radials then yes you are going to feel the difference.
You will also get the same if you mix crossply/bias-belted/radial tyres due to their different profiles and characteristics.
I've never felt any difference when mixing zero degree radials with other brand/model zero degree radials.