35i Tyre Profiles

[mcbutler]

Hi All,

Buying new boots.
I have 255/30/19 rears amd 225/35/19 fronts.
I wanted to replace the rears with a 35 profile instead of 30, thinking of comfort..
I contacted Black Circles for a quote and they asked me to confirm as cars with different widths front to back generally have different profiles as well.

Has anyone gone for 35 profile rears, is there any reason why I shouldnt??

 

[Player 1]

I keep thinking similar as well, I think it's well worth doing from a comfort point of view.
You may need to increase the front to a 225/40/19 to match. I have heard of (but never experienced, I might add) the DSC throwing errors if the front/rear wheel speeds differentiate too much from factory specifications. I'm not 100% sure if it's that fine of a tolerance though, if you do try it without changing the front, please let me know if it works!

I think fit ought to be okay? going from a 30 to a 35 profile 255 tyre would add 25mm to the diameter so will fill the wheel arch a little more but shouldn't rub, it will add a bit to the ride height but it's minimal.

The main thing to think about is that larger diameter tyres will equate to changing the cars actual speed relative to what the speedo says, that difference in profile would mean the car's actual speed would increase from 70 to 72.8mph if your speedo was 100% accurate, we all know it isn't so in reality actual speed should still be just below 70mph.
I've currently have 275/30/19 tyres on the rear and my actual speed at a readout of 70 is roughly 68.5mph, a 255/35/19 would be 1.4mph faster again so you'd be right on the limit assuming your speedo is similarly calibrated to mine, but would be okay. I wouldn't go through any speed cameras just above the limit thinking the speedo error will save you though! :wink:

Best suggestion would be to pop down a dual carriageway/motorway with the cruise at 70 whilst having a gps tracker running to double check your actual speed. Anything less than 67mph will be fine.