19" Rim Tyre Sizes

[156F1]

Hi, I would like to seek advice from rim and tyre gurus here.

I just fitted 19" rims (8.5J front, 9.5J rear) with tyre sizes 245/35 front and 275/30 rear (recommended by Leong Seng). Compared with 17" stock wheel, the overall radius (D) and circumference (C) are as follows:

Stock 17" 225/50
D = 328.4mm
C = 2,063.4mm

19" 245/35 Front
D = 327.1mm
C = 2,054.9mm

19" 275/30 Rear
D = 323.8mm
C = 2,034.5mm

The 245/35 front and 275/30 rear sizes are also used on BMW OEM 19" rims (except for the M5). Question is that why the rear wheel circumference is smaller than the front, thought rear should be same or larger? Also, would 285/30 (D = 326.8mm, C = 2,053.3mm) be a better fit compared to the stock 17" wheel? Or should the front be 235/35 (D = 323.6mm, C = 2,032.9mm)?

BTW, what tyre pressure should I pump? Same pressure for front and rear, or front lower as stated on the label at the driver door?

Grateful for your advice, cheers!

 

[rab]

Re: 19" Rim Tyre Sizes

Seems like the 285/30 tyre is not recommended for 9.5" width rim, minimum width is 10" so that's probably the reason 285/30 was not considered. 275/30 seems to be the best available fit.

As for why not 235/35 for the front, 245/35 seems to be the closest circumference to stock plus most people usually want the widest possible tyre available for the rim. 245 is 10mm wider than the 235.

 

[TripleM]

Re: 19" Rim Tyre Sizes

The rear circumference is smaller coz the profile used is 30 whereas the front is 35
and it all staggered set up cars that has 30mm difference in terms of tire widths between the front and the rear, the height profile at the rear ( fatter tires ) will always be smaller ( typically 5mm )

And honestly speaking , on 19 inch tires, the 35 / 30 profiles are too thin for 5-er
tho they are widely used. I think a better combo for a better ride is 40/35 as seen in M5

For 3 series, 35/30 on 19in is correct

 

[156F1]

Re: 19" Rim Tyre Sizes

Can non-M5 E60s' wheel wells (with stock suspension) accommodate 40 front, 35 rear profiles with 245 front, 275 rear widths? Anyone try before?