can front and rear tyres be different size?

Giselle · Postby **Giselle** » Tue Apr 14, 2015 12:34 am

I lost a tyre today so I'll have to replace it. I'll replace at least 2 tyres, because if I'm going to have different brands, I'd rather have them in pairs (brand X on front, brand Y on rear)

Turns out that the previous owner put on 185/65/14 instead of 185/60/14 (which I think it the proper size for a NA).

I have 3 options then:
1. replace 2 tyres with new 185/65/14 and be stuck with wrong sized tyres
2. replace 2 tyres with the correct sized 185/60/14, but have the other 2 as the incorrect size
3. splash out on 4 new tyres (probably the best, but certainly the most expensive option. money is short)

Is it ok to have different sized tyres on the front and back? If so, should the bigger ones go on front or back?

sorry for the dumb question :oops:

hks_kansei · Postby **hks_kansei** » Tue Apr 14, 2015 12:41 am

Front and back no problem, side to side have to match though.

The only real downsides are that the larger wheels would have a larger rolling diameter, so the speedo might be out slightly. (only relevant on the rear)

If the car has ABS it might act a bit funny, I cant remember if MX5 ABS acts diagnonally or not?

as for which end, personally I'd mount them on the rear, purely because it looks better imo.

hks_kansei · Postby **hks_kansei** » Tue Apr 14, 2015 12:42 am

For reference, I ran larger tyres on the rear of mine for about 6 months or so, no problems at all.

Giselle · Postby **Giselle** » Tue Apr 14, 2015 12:48 am

awesome thanks

maybe when I finally put in my lowered springs I should even the car out by only putting 2 in :roll:

I think 185/60 vs 185/65 will be 9mm lower

aka_juffa · Postby **aka_juffa** » Tue Apr 14, 2015 9:58 am

Here is something to help calculate the difference in tire sizes.

http://www.miata.net/garage/tirecalc.html

J.

hks_kansei · Postby **hks_kansei** » Tue Apr 14, 2015 1:21 pm

Giselle wrote:awesome thanks

maybe when I finally put in my lowered springs I should even the car out by only putting 2 in I think 185/60 vs 185/65 will be 9mm lower

No, put in all the springs or none, unless you know how the springs will make the car behave. (due to the different spring rates to stock)

The height difference will be about 9mm as you said, but that's small enough that it won't stand out much anyway.
Ground clearance is hard to notice small changes, it's more the tyre to wheel-arch gap that you notice them.

project.r.racing · Postby **project.r.racing** » Tue Apr 14, 2015 2:13 pm

in queensland the front and rears can be different sizes and makes. from side to side the have to be the same side but make can be different. as long as side to side tyres had the same construction.

but if you pair everything, then no problems. as above, put the larger diameter tyres on the rear until they are gone.