I am trouble shooting some vibration issues and trying to eliminate the spacers without which there's not enough clearance
The front tires hit the top suspension part with may be 2-3 mm clearance

Current set up
Front: 19 x 9 et 37 with 255/35/19 with 7 mm spacers

wheels I am interested in:
19 x 8.5 et 37 with 245/35/19

My understanding is---the new wheels be 12 mm narrower than the current set up and the 12 mm be split between the inside and the outside giving me 6 mm clearance on the inside, correct ?
With 245 tires, I would also clear the top suspension with 5 mm, correct?

I think I would be fine but a good friend who's well rehearsed in such things disagrees with me

Thanks

 

Im not sure that is correct, there are two factors, the rim width and the tire width. 255/35/19 are 255 mm wide and the 245/35/19 are 245 mm wide. So if you keep the rim the same tires would be 5mm smaller on each side. Assuming you are using the same brand and model of tire and they are measured the same way.

For the rims assuming they are both 37 mm positive offsite
19x9 are 228.6 mm wide
19x8.5 are 215.9 mm wide
Difference is 12.7 mm

19x9 middle is (228.6/2) 114.45 mm on each side, then you add 37 for a total 151.45 mm on the inside of the mounting surface.
19.8.5 middle is (215.9/2) 107.95 mm on each side, then you add 37 for a total of 144.95 mm on the inside of the mounting surface, which is 6.5 less mm inside of the mounting surface.

For example if the inner sidewall of the tire for the 255/35/R19 on the 19x9 is 3 mm away from rubbing the inner wall of the well.

1) Lowering the tire to 245/35/R19 on the 19x9 rims should add 5 mm of additional space to the existing 3 mm for a total of 8 mm.
2) Lowering the tire to 245/35/R19 on the 19x8.5 rimes should add 5 mm of additional space for the tire, and 6.5 mm due the smaller rim width with the same 37mm offsite for a total of 11.5 mm of inner space.

This would suggest that going down in both rim and tire width would allow you to drop the front spacers that are 7mm leaving you just a gain of 4.5 for a new total of 7.5mm

Also note the height of the tire will be a little less (89.25 mm - 85.75 mm ) of 3.5 mm

Im not an expert but I believe my math is correct. Hope this helps.

 

I checked here and confirmed the rim itself will add 6.4mm more room.
https://www.willtheyfit.com/index.ph...8.5&offset2=37