W204 C63 PPP longer wheel bolts

[brisel]

I bought some 18” OEM rims from eBay with a view to fitting winter tyres on them. The problem is that they are the wrong offset (ET45 where the standard 19” rims are ET50) so I have bought 5mm spacers to correct that. Now, I need longer bolts. The originals are 28mm long. 60 degree pitch. I have found 33mm versions.

Is it as simple as this? Will they handle the torque and lateral forces generated?

[Scrump]

I think your understanding of et is the wrong way round. A smaller et means the wheel ‘sticks out’ more.
In your case it is only by 5 mm. Adding 5 mm spacers to the 18 wheels would give them an effective et of 40, putting the centreline of the wheel 10mm further out than your existing 19 wheel.

I also suspect the 18 inch rim width may be narrower than the 19 rim width, in which case the 18 inch wheels may actually look a bit more recessed.

It is likely that you don’t actually need spacers or longer bolts.

What is the rim width on the 19 inch and the 18 inch wheels?
(Not crucial but what are the respective tyre sizes?)

[brisel]

To fit over the brake callipers, I need another 5mm. The tyre widths are the same. The rolling radius is the same. I can’t get 19” winter tyres as they only make them for the 18” rims.

[10126 Torino]

I needed much longer wheel bolts when I bought some wheels not meant for my car , including an extra 10 mm spacer .

I bought some off Ebay and never had a problem with them although my car had significantly less power than a 63 .

[Scrump]

brisel said:

To fit over the brake callipers, I need another 5mm. The tyre widths are the same. The rolling radius is the same. I can’t get 19” winter tyres as they only make them for the 18” rims.

In which case ignore my previous post.
I thought you were fitting 5mm spacers due to the 5mm difference in et values.

[brisel]

Scrump said:

In which case ignore my previous post.
I thought you were fitting 5mm spacers due to the 5mm difference in et values.

I need the spacers because the offset is 5mm less than the existing wheels. The ET value is the distance from the centre. The ET45 rims are 5mm closer to the centre, so foul the callipers which are bigger on the Performance Pack Plus models. You were kind of right...

[brisel]

So, next question - where do I get stronger bolts from? With spacers, the bolts will have more shear risk as the heads will be 5mm further from the threads in the hub and there will be a lot of torque from the brakes and drivetrain. Plenty of 33mm bolts on eBay but no tensile strength is listed.

[Scrump]

I don’t want to turn this into an argument but a wheel with an et of 45 has the wheel centreline 5mm further away from the brakes than a wheel with an et of 50. Fitting 5mm spacers to a et 45 wheel gives it an effective et of 40.

The et is the distance in mm from the hub face to the centreline of the wheel, hence a smaller et means the wheel centreline is closer to the hub face (I.e. further outboard).

If the wheel is hitting the brakes then it is not due to the change in et from 50 to 45, that would make the wheel less likely to contact the brakes.
If you have interference then it will be due the different shape of the wheel inner face and/or the inch less in diameter.

See attached image for a wheel and tyre size app which confirms my understanding of et values.



Anyway if a 5mm spacer solves the problem that is an easy solution and we can all forget about et values!. Good luck finding appropriate bolts.

[brisel]

Well, that’s the sizes of both sets of wheels and the ET 45s foul the brake callipers. By just under 5mm.

Thanks for taking the time to look it up.

Edited by brisel on Monday 7th June 17:23