This is a thread that's going to cover the fitment of new aftermarket 19" wheels on my 2017 C43 which may be useful to anyone else doing similar. To start with this is what the car came with:

Front: OEM 18x7.5" ET 33 5 Spoke w/ 225/45-R18 Pirelli Cinturato P7 All Season





Rear: OEM 18x8.5" ET 49 5 Spoke w/ 245/40-R18 Pirelli Cinturato P7 All Season





We're putting on the 19x8.5" ET 35 Vision Clutch Rims w/ Bridgestone Blizzak LM-005 235/40-R19 tyres.




The measurements changes are covered in the table below to summarise.




On the front on the inner edge of the tyre we move in 2mm from the offset and we're 10mm wider which moves that edge another 5mm further in, totalling 7mm closer to the suspension. On the outside we of course move the same 2mm in from the offset, but then 5mm out from the extra width totalling 3mm out towards the fender. On the rear there is a lot more space in the wheel arch, and we've been operating on the assumption that we will run out of space on the front long before we run out of space on the rear. We're buying from discount tyre, the reps checked that this setup would work, they said it would, and we had them order in the wheels and tyres to be fitted. It's Black Friday, they're close by, they price match, and they've otherwise been really helpful. They arrived, we had them fitted and found out that the front tyres just barely rub against the steering knuckle on the suspension assembly. Still, we don't want any rubbing and obviously we're not happy with that so we went back to the drawing board.

Here are the photos from the test fit:



Here is how and where the tyres were rubbing:



We basically had 2 options, spacers or narrower tyres on the front and a staggered set-up. We didn't really want to go staggered because it means we can't rotate the wheels back to front, and we are getting a really good deal on these tyres because of a price match, so we really didn't want to do that. Narrower rims wouldn't have helped us since it's the tyres rubbing and they obviously stay in the same place no matter the width of the rim, only the offset matters. We could try and find rims with a 25-30mm offset, but they're not all too common in this size, if you can find them they're expensive, and we just really liked these Vision Clutch rims. This only really left us with one real option: spacers.

We knew we'd want at least 5mm spacers to get a little bit of clearance from that steering knuckle, but we also wanted hub centring spacers (spacers with their own hub lip) and the minimum thickness for spacers like that is generally 10mm. The hub on the car has about 12mm of depth, but about 4mm of that tapers down towards the outer edge, so we really only have about 8mm. 5mm spacers would be fine if that was the only problem, but the mating surface on the rims also has a roughly 3-4mm chamfer, so we actually don't even have that, we have more like 4mm of surface to hold the rims. This meant that even if we went with like 3mm spacers (which we think wouldn't give enough clearance to that steering knuckle), we would only have about 1-2mm of useful surface. A 5mm spacer would obviously completely cover the useful part of the hub plus 1mm of chamfer and leave us with nothing centring the wheel apart from the bolts. This may or may not be a big issue, but we'd rather be on the safe side and just get the wider 10mm spacers for more clearance and the hub extension.


Now, we know that on the inside a 10mm spacer will give us enough space as we're only just touching, but we don't yet know if there is enough room on the outside by the fender to do this with rims that are already coming out about 10mm. But we've measured and looked, and it looks like we'll be ok. The tyres have a rim protector that is basically a rubber lib that protrudes about 5mm from the wall of the tyre past the edge of the rim that protects it a little from curbs. Past that we go around 10mm in before we get to tread. From the test fit we know that the rim protector is just a little shy from flush, which means we should have around 15mm to play with. We also figured that if we're getting spacers, we may as well get the same for the rear since despite the offset difference they also have more room to come out. So, we've ordered 4 of these CTS Turbo 10mm spacers. They're advertised for Volkswagen/Audi, but they use the same 66.56 bore as us, as well as the same M14x1.5 bolts, and of course they have the same 5x112 bolt pattern so they should be compatible. Plus they were on a significant sale.


Of course, with spacers we need longer bolts. Aftermarket rims usually need conical seating bolts, rather then the OE hemispherical or ball seat bolts. These spacers come with a set of 20 longer 40mm (OE uses 28mm iirc) bolts, but they're hemispherical so we can't use them on the new rims. We'll still make use of them though since we'll use the spacers in the summer with the OE rims and we need them for that. This did mean we had to buy another 20 conical bolts for with these new rims though.

We ordered all of this on Thanksgiving so we're waiting on all of this to arrive. I'll update this thread in December once we can finally put the new wheels on.

 

Very late update,

In the end the best spacer setup was 5mm in the front, 15mm in the back for the Vision Clutch rims. I did try 20mm spacers in the rear, which is about as large as most people will advise for your wheel bearings, and you could run the 20s if you want it a bit more aggressive, but the 15s looked better in my opinion.

The main struggle with this car is that the standard rear fitment is pretty bad where the rear wheels are completely buried in the arches. With the OE rims, you could probably run huge 30mm spacers, but then you're going to put wear on your wheel bearings and I wouldn't advise that. The general consensus online is 20mm is a safe maximum, 25 is pushing it, 30+ is for when you don't care about your wheel bearings. And the thing is that with the OE rims that means that you also can't run good front fitment because it looks unbalanced with flush front wheels and buried rears. On the OE rims I ended up using the 20mm spacer in the rear and a 3mm spacer in the front.

Fast forward about a year to when I took the winters off for the second time to put the OE rims back on for the summer. After about 2 weeks with the OE rims on I got a tyre pressure warning. When I took the wheel off to look for a puncture I couldn't find it.


Instead what I found was this crack.


I don't particularly like the staggered OE setup anyway, since it's bad for rotating wheels and honestly it just understeer biases the car too so it's not like it's a maintenance for performance trade-off either. These tyres also only had another season or 2 left in them anyway So rather than sending these in to get fixed I got new rims and tyres for the summer. I'm now selling these old wheels on Facebook marketplace as they are.

In truth, J8.5 is overkill for 235 section tyres, and so they're slightly stretched on the Vision Clutch rims. So this time around I was looking for J8 rims, lowest offset within reason, lowish weight, good value, and different to the Vision Clutch rims I already had.


I ended up going with the Enkei Raijin rims in hypersilver J8 ET 35 5x112 with Sumitomo HTR A/S P03 235/40 R19 summer tyres.

The only problem with these rims is that the hub bore isn't 66.6mm, it's 72.6mm, so you need hub centring rings to make up that difference. As of right now I still haven't actually gotten the hub centring rings and I don't have any vibrations or issues, and most people say that they're optional because the hub doesn't actually do much to hold the rim centred, it's the clamping force that does that. Still, I'll get them eventually since it is generally advised to and they're cheap.

I'm running the same spacer setup as the vision clutch rims, 5mm in the front, 15mm in the rear. Comparing the ride of this wheel set to the others I was actually very surprised. These Sumitomos ride much smoother and quieter than the OE run flat Pirellis, and also significantly better than the Bridgestone Blizzaks. I was expecting the winter tyres to be the softest since they're winters, and these Sumitomos are UHP all seasons, but I was wrong. Frankly, this has made a surprisingly big difference to the car and for the price these Sumitomo tyres are basically unbeatable. The only other alternative I'd consider are the equivalent UHP continentals, which are supposed to be slightly better, but overall I'm very happy with how this turned out and it looks great. This setup is also considerably lighter than the OE setup, and also a little lighter than the Vision Clutch setup and you can feel it too.