tire sizes

[rbrickman]

My '95 530i currently has 225/60R15 Uniroyal tires (http://4wheelonline.com/uniroyal-tires.246715) that I want to replace. What other tire sizes that are compatible with my 15x7 wheels? My car is not lowered. Do you think it is better for me to upgrade to 16s or 17s to have more options?

[632 Regal]

I went with 205/65r15 on mine, the 225 were unobtanium. You want to keep the diameter close to stock so the speedo stays somewhat accurate. Tire place told me they couldn't put them on because they are not specified for the car. I said you have nothing else available and they put them on anyway.

Check this link, can compare all different sizes and wheel size options. https://tiresize.com/tiresizes/225-60R15.htm

[rbrickman]

Thanks for the suggestion. The diameter and width of 205/65 are almost the same with 225/60.

[califblue]

here you go...
https://www.ebay.com/itm/4-New-225-60R15-Ohtsu-by-Falken-FP7000-All-Season-Tires-480AA-2256015-60-15/182362564913?hash=item2a75a7e931

[BigKriss]

yes you can go to a 17x8 wheel and run 235/45/17 tyres. Plenty of options available.

[Rustam]

15*2.54 = 38.1 centimeters tire hole diameter.
(60% of 225 ) * 2 = 27 centimeters 2 heights of tire wall.
Total wheel diameter = 65.1 centimeters.

Calculate the new size satisfying the desired rim size in accordance to this figure +/- 5 millimeters.

Additionally, this link provides a helpful chart relating rim width to a tire's: http://www.tyresizecalculator.com/charts/tire-width-for-a-wheel-rim-size-chart

This snapshot shows the portion of interest: 8611

[genphreak]

Your tyres are 627mm tall.

15" tyres are most comfortable and durable/forgiving. They can go up and down gutters with less structural and cosmetic damage.

16" tyres crispen the drive quite a bit. 17s as fitted to e34 M5 use 235/40x17 tyres (620mm dia). 16s certainly feel optimal, Only driven 2 stock e34s with 18s and both felt awful- but this may have been due to suspension troubles

Oftentimes an important consideration is where snow-chains can be fitted. On e34, 8" rims don't leave enough space for them.

But 17s are not what the e34 suspension was designed for, and a 235 doesn't protect the 8" rim very much. Going to 245/40x17 can even be done, but reduces room for error as diameter increases to 628mm. At this size, it is possible to get rub up front at full-lock and some strut extension combos, or if anything is slightly out of whack but if so, the alignment likely isn't as per M5 measurements (and also be sure you have the stiffer (750/M5) bushings or poly bushes (these are noisey) to prevent too much fore/aft slopping).

Best feeling combo I've ever found (for a sporty feel) is a 16" 225x50x16 (3 series size) on light forged 7.5" rims. This is apparently 631mm diameter. When driving on normal roads, tram-lining is minimised, the car is most nimble, rim and tyre is light and ride is acceptable for normal people- important if you have Biisteins or another brand's sport shocks. Models after E34 were engineered with large rims/lower profile tyres and drive better with them. The suspensions have been put together to be structurally lighter (all aluminium arms), and with more pivots can deal with the greater amounts of leverage that larger/wider wheels exert over the car.

[Coyote_ar]

i got 17x8 ET22 wheels up front, and 17x9 ET20 wheels in the back. 235/45-17 up front, 255/40-17 in the back. no rubbing, quite low in the front, but the back is high so not sure if they would rub if it was lower. hope that helps.

[genphreak]

Nice sizes! BigKriss also has 255s on ET20s IIRC, and he doesn't encounter rubbing. But no hope of snow chains though!

It'd be good to know if having ET22 stops the rub that a 245 can just encounter on the front. I had 245/40x17 (Dunlop Sport 01) on 8 inch ET20s- lowered to M5 height, this worked fine for me.

The trouble is that each model of tyre can have quite different tread footprints, shape profile and even carcass widths. I've read people complaining 245s don't fit up front without rubbing before

[Coyote_ar]

Hey Genphreak, havent tried 245s up front with my ET22s. But i do have quite a lot of clear space all around with my 235s, so i would dare say that 245s should clear aswell. The only point i saw that there was some light rubbing (as in only touching the letters on the side). Was when i lifted the car, if i turn the steering completely to either side, the outer wheel will rub on the chasis frame. But that happens only with the suspension completely extended (so due to negative camber the wheel goes closer to the chasis rails).

Aside from that, no rubbing anywhere up front. The rears ... i cant comment since my car's ass is quite high (about 30mm from the wheel arches) and suspension is quite stiff (got a heavy CNG tank in the trunk), so it rarely goes that low, even with 2 adults in the back.

[genphreak]

Hey Genphreak, havent tried 245s up front with my ET22s. But i do have quite a lot of clear space all around with my 235s, so i would dare say that 245s should clear aswell. The only point i saw that there was some light rubbing (as in only touching the letters on the side). Was when i lifted the car, if i turn the steering completely to either side, the outer wheel will rub on the chasis frame. But that happens only with the suspension completely extended (so due to negative camber the wheel goes closer to the chasis rails).

Aside from that, no rubbing anywhere up front. The rears ... i cant comment since my car's ass is quite high (about 30mm from the wheel arches) and suspension is quite stiff (got a heavy CNG tank in the trunk), so it rarely goes that low, even with 2 adults in the back.

Yes the chassis rail is a bug-bear for some. But strut too, IIRC.

Bare in mind, when looking at the gaps, you have to allow differing amounts of wiggle room for when the car is cornering hard and the tyre squirms on the rim, also for the lower control arm bushings to compress or extend (dep on the side forcing the turn.