Tyre sizes for Serpentine wheels

johnnyb44 · 13th February 2020, 09:59

Hi.
I've got a lovely set of Serpentine wheels on my old 75.
They look fantastic but they often feels a little harsh. This time of the year when the roads aren't at their greatest, the pot holes and poor road surfaces intrude into the cabin of the car (noise wise) The wheels are with 225/45/17 tyres and will be needing a new front set soon. I'm thinking of going ahead with some 225/50/17 hoping the slightly higher profile will absorb some of the harshness out.
A couple of things that concern me though, will they fit within my wheel well without fouling anything (im pretty sure they will)
Will they look odd against the perfectly usable rear 225/45/17.
More importantly though is it legal to mix and match different type sizes on front and rear axles.
Another question is would a difference of a deeper profile of 5mm make that much of a difference to ride quality. If its ok to do this i will eventually replace the rears for the newer size when they finally wear out.
Best regards,
Johnny

kelvo · 13th February 2020, 13:54

It is not illegal to have different profiles front and rear axle, quite often you find performance have different widths/profile front to rear - but the main thing is the rolling radius otherwise you may have speedometer errors.

You are incorrect about 5mm ride height though in the difference between the two. The 45/50/55 etc is an aspect ratio of the tyre width, so a 45 profile is 45% of the tyre width for example, so 225/45 has a depth of around 101mm, a 225/50 has a depth of 112mm, so having these on the front may make it have a slight nose up stance.

malagas · 13th February 2020, 13:54

Quote:

Originally Posted by johnnyb44

Another question is would a difference of a deeper profile of 5mm...

I think that 's not 5mm but 5%...

Enviado do meu LEX820 através do Tapatalk

johnnyb44 · 13th February 2020, 14:30

Many thanks both for correcting me. Would never of known that if you wouldn't of pointed it out.
👍

T-Cut · 13th February 2020, 20:35

Quote:

Originally Posted by johnnyb44

Would never of known that if you wouldn't of pointed it out.

Time for some reading then: https://www.uniroyal-tyres.com/car/t...tyre-size-mean

TC

RoverP480 · 13th February 2020, 21:26

My only concern having different size tyres front and rear would be , can it affect the ABS operation? If the 75 has DSC it could be even more of a factor. 11mm radius is more than the difference between a new and worn tyre.

13th February 2020, 09:59	#1
johnnyb44 I really should get out more....... Rover 75 Join Date: Sep 2013 Location: north wales Posts: 2,705 Thanks: 1,774 Thanked 902 Times in 507 Posts	Tyre sizes for Serpentine wheels Hi. I've got a lovely set of Serpentine wheels on my old 75. They look fantastic but they often feels a little harsh. This time of the year when the roads aren't at their greatest, the pot holes and poor road surfaces intrude into the cabin of the car (noise wise) The wheels are with 225/45/17 tyres and will be needing a new front set soon. I'm thinking of going ahead with some 225/50/17 hoping the slightly higher profile will absorb some of the harshness out. A couple of things that concern me though, will they fit within my wheel well without fouling anything (im pretty sure they will) Will they look odd against the perfectly usable rear 225/45/17. More importantly though is it legal to mix and match different type sizes on front and rear axles. Another question is would a difference of a deeper profile of 5mm make that much of a difference to ride quality. If its ok to do this i will eventually replace the rears for the newer size when they finally wear out. Best regards, Johnny __________________ Replaced pcv filter, springs, plenum spy hole mod,Bonnet cable divider mod. Wax oiled.Air con recharged. Auto box oil changed , Jules plenum guard fitted .Smoked wind deflectors fitted.S/S Compensator.Club Grill Badge kindly donated by Andyg2011..

13th February 2020, 14:30	#4
johnnyb44 I really should get out more....... Rover 75 Join Date: Sep 2013 Location: north wales Posts: 2,705 Thanks: 1,774 Thanked 902 Times in 507 Posts	Many thanks both for correcting me. Would never of known that if you wouldn't of pointed it out. 👍 __________________ Replaced pcv filter, springs, plenum spy hole mod,Bonnet cable divider mod. Wax oiled.Air con recharged. Auto box oil changed , Jules plenum guard fitted .Smoked wind deflectors fitted.S/S Compensator.Club Grill Badge kindly donated by Andyg2011..

13th February 2020, 13:54	#2
kelvo Gets stuck in MG ZT 190 SE Join Date: Oct 2017 Location: Chatham, Kent Posts: 569 Thanks: 22 Thanked 163 Times in 135 Posts	It is not illegal to have different profiles front and rear axle, quite often you find performance have different widths/profile front to rear - but the main thing is the rolling radius otherwise you may have speedometer errors. You are incorrect about 5mm ride height though in the difference between the two. The 45/50/55 etc is an aspect ratio of the tyre width, so a 45 profile is 45% of the tyre width for example, so 225/45 has a depth of around 101mm, a 225/50 has a depth of 112mm, so having these on the front may make it have a slight nose up stance.

13th February 2020, 21:26	#6
RoverP480 Gets stuck in None at the moment Join Date: Jan 2018 Location: Hereford Posts: 501 Thanks: 1 Thanked 165 Times in 146 Posts	My only concern having different size tyres front and rear would be , can it affect the ABS operation? If the 75 has DSC it could be even more of a factor. 11mm radius is more than the difference between a new and worn tyre.