I'm after a bit more rubber. I want to fill my arches a bit more and get some more width on my rims.

I've been using this Tyre Size Calculator to work out the sizes.


I have 19" rims and currently have 215 35 r19 tyres - wheel diameter: 633mm.




Recommended sizes as per alloy wheel dealerships for Subarus:

17" ...............215 45 ...............wheel diameter: 625mm

18" ...............225 40 ...............wheel diameter: 637mm

19" ...............235 35 ...............wheel diameter: 647mm




The wheel diameter obviously affects the 4WD and speedo reading. The recommended sizes are all different in wheel diameter... doesnt this affect the drive? Or is it acceptable for those increases in rim size??

I would ideally like to increase my tyre size to 245 35 r19 which has a wheel diameter of: 654mm.

I already know that they will fit under the arches as I accidentlly fitted 255 35 r19 on which have a wheel diameter of: 661mm - they did fit as I've rolled my arches, but these only just cleared the sides of the arch on full lock by about 2mm.

The 245 35 r19 will fit under the arch and clear it on full lock, but will the fact that they are 7mm bigger in diameter than the recommended size affect the drive????

Thanks
Alex

 

Hi there! I'm no expert but, going to that tire/wheel size will affect the handling and overall driveability of the car..................

 

I bought the car with the 19's on it and I know that 19's are more for looks rather than 18's which would handle better.

BUT I'm keeping the 19's on so really I'm being stupid as I'm sacrificing handling for looks...

Either way I just need to know if 235 35 r19 will be ok with respects to the way the cars diffs are set up etc?

 

As long as you have the same size front and rear it should not make a difference to your diffs. The only thing is that your speedo will be reading lower than your actual speed.
Paul.

 

Dont forget that if you have wider tyres there will be times when you actually have less grip (ie in the wet) as the weight of the car is spread over a larger surface area and actually reduces friction .... just so you are aware that more rubber doesnt always mean more grip.

 

Is there anywhere that can recalibrate the speedo for the larger tyre size?

Or should I just make sure I'm doing 45mph when I go past a 50mph gatso?

 

So take it easy in the wet... which is all yr round - DOH!

 

Thanks guys I really appreciate the imput!

 

If you have a sat nav it will usually tell you what speed you are actually doing.

 

I dont have a sat nav, altho god knows I need one with my sense of direction, lol!

 

You don't say if these are for a classic or New Age Impreza, as the recommended tyres sizes are different.

If it's for a classic, then the normal size (and what the speedo is calibrated for), is 205/50x16

Comparing that to 235/35x19, then these are 5.8% "bigger", so the speedo and odometer will under-read by this amount.

What you may not realise is that you will also effectively be increasing the gearing by the same amount, so effectively your call will pull 5.8% slower in any gear (ie reduced acceleration by nearly 6%), though this won't be too noticeable in the lower gears.

John

 

Its a new age 2002.

I did think that bigger wheels meant a screw up with the gearing, but wasnt sure what the exact implication would be.


So just to recap, the bigger wheels will 'look' nicer, but I'll be loosing, GRIP, TRACTION and effectively SLOWING the car down... smart move there Alex I dont think, lol!

Anyone would think I'm more interested in appearence than overall driving experience... I should really be flogged for taking this route with my Impreza modifications!

Ok I think all my questions have been answered here - I'm going to get 245 35 r19's on all 4 wheels as soon as fundage is available!

Once again thank you all very much for the info, its much appreciated!

 

Alex,
I don't think you'd loss grip in the dry due to size as there are a lot of cars running bigger tyres and you would have to have massive tyres before you got into that.
I was once told that traction would be better with bigger wheels due to an increase in the gearing, harder to spin up, and a bigger foot print.
You may find you're quicker off the mark because you will have better traction and the longer gearing that will mean you can hold first gear for longer and get a higher speed for the same revs.
You will also get better fuel economy as the revs will be lower for any given speed.
Thanks,
Paul.

 

I like what you're saying Paul!

I mean, my main concern was that I didnt want to put tyres on of a size that could potential harm the car... if that makes sense?

As long as the 245 35 r19's dont cause anything to be totally out of sync with the smooth running of the engine and gearing etc then its all good!

The argument between things like traction and acceleration etc are secondary concerns which are not as crutial as the primary ones.