Different Profile Front to Rear

You might shift the weight slightly backwards.

I can't see any major issues though, traction might be reduced though as tyre sidewalls help the tyres hook up on the road surface as they deform
 
I ran 275/30's on mine with no obvious difference. Tyres went from pilot super sports to Vredstein sessantas, pilots felt marginally better but that is probably more down to the tyre itself rather than the size change.

edit - having look on a tyre size calculator, the stock sizes are 2% bigger on the rear than front, a 275/30 is 1% smaller than a 245/35 , so a closer match.
 
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Thanks for that TomO, certainly made me reconsider, 4% inaccuracy is a bit too much for my liking. Camskill have Vredestein Ultrac Sessantas in 275/35/19 for £175 each, the cheapest stock size Continental I can find is a CS5 fully fitted from my local tyre garage for £240.
 
Some manufacturers have this as standard, Porsche wears 245/40/18s front and 285/30/18 rear, I wouldnt have thought it would cause any major problems having a few mm difference in rolling radius front to back.
 
Really you need to say the tyre specs (255/35 R19 for example).

Just giving us "30 profile" is usless. I could use 30 profile tyres on mine, but theyd have to be 205/30/R16 to fit my alloys, which would completely throw off my speedo (mine should be 195/45 R16 to give an almost perfect rolling radius).


Now Ive clicked on you own an M3, where the rear tyres are like 255 wide?, 30 profile will be fine.


The width and profile are proportional.

If you have a 195/45 R16 tyre, this can equal roughly a 205/40.

EDIT:
Using the figures you gave earlier on post 20
245/35/19 front 265/35/19 rear

To look similar, you would need to use 270/30 R19 or 275/30 R19 (would be slightly wider and taller and look slightly dragster) tyres to look similar.
But because the M3 is rear wheel drive, you will need to match the rolling radius to a certain degree so the speedo isnt thrown off, unless you have it recalibrated.
 
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My 330Ci and Z4 both ran 225/40/18 on the front, and 255/35/18 on the back.

I'd suggest that having the profile sizes matching is unimportant, but wouldn't going from 265/35/19 to 265/30/19 mean a smaller diameter of the wheel/tyre combo, and therefore increase the gap between the tyre and the arch, creating the illusion of a higher ride height at the rear?

Deviating from OEM spec might not have any negative effect, it might even make it better, but is it worth taking a step into the unknown for the sake of a £200 saving?

I might be tempted to change size if it made a better tyre became an option, but otherwise I'd probably just spend whatever it costs the get the best tyres in the right size. It'd be worth £200 for the piece of mind to me, others often think differently... :)
 
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