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.
Front: OEM 18x7.5" ET 33 5 Spoke w/ 225/45-R18 Pirelli Cinturato P7 All Season
Spoiler
Rear: OEM 18x8.5" ET 49 5 Spoke w/ 245/40-R18 Pirelli Cinturato P7 All Season
Spoiler
We're putting on the 19x8.5" ET 35 Vision Clutch Rims w/ Bridgestone Blizzak LM-005 235/40-R19 tyres.
Spoiler
The measurements changes are covered in the table below to summarise.
Spoiler
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:
Spoiler
Here is how and where the tyres were rubbing:
Spoiler
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.
Spoiler
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.
Spoiler
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.
