Changing tyre size

Wheels, Tyres, Suspension, Chassis, Faults and Fixes
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Doctordeano
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Joined: Sat Mar 18, 2017 8:13 pm

Changing tyre size

Post by Doctordeano » Tue Nov 06, 2018 2:38 pm

Hi, I wonder if you can help with a tyre question.

I have a Discovery Sport HSE Lux with 245/45/20 standard tyres fitted. The tyres are due for replacement very soon and I was wondering is there is any benefit in changing the tyre size to 255/55/20.

1. Is there any benefit changing the size with the slightly wider size and taller profile?
2. Will the change affect the drive of the car?
3. Should I stick with the same size?

Many thanks
Dean
MY16 Discovery Sport HSE Lux - Red with Black Pack


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Dashnine
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Re: Changing tyre size

Post by Dashnine » Tue Nov 06, 2018 5:05 pm

Doctordeano wrote:
Tue Nov 06, 2018 2:38 pm
Hi, I wonder if you can help with a tyre question.

I have a Discovery Sport HSE Lux with 245/45/20 standard tyres fitted. The tyres are due for replacement very soon and I was wondering is there is any benefit in changing the tyre size to255/55/20.

1. Is there any benefit changing the size with the slightly wider size and taller profile?
2. Will the change affect the drive of the car?
3. Should I stick with the same size?

Many thanks
Dean
The rule to keep the same rolling radius (for speedo accuracy) is a 5% drop/rise in profile per 20mm width increase/decrease. You're increasing both width and profile.

Going from 245/45 to 255/55 means your sidewall is 55% of 255mm (140mm) instead of 45% of 245mm (110mm) so:

1. I guess you'll get a more compliant ride with marginally more grip. You might get clearance issues with the taller sidewall.
2. Not much, but your speedo will be out by around 8%
3. Prob not worth changing for marginal gains - depends if 255s are way cheaper.

Check it out at https://tiresize.com/comparison/.
MY19 P240 HSE (on order), Indus, Black Pack, Privacy, Memory Seats, Roof Rails, Spacesaver, Cold Climate Pack, 2 x USB in 1st & 2nd rows.
MY16 HSE Black, Santorini, Memory Seats, Roof Rails, Detachable Towbar, 2 x USB in 2nd row, Delete Badging.


Doctordeano
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Joined: Sat Mar 18, 2017 8:13 pm

Re: Changing tyre size

Post by Doctordeano » Tue Nov 06, 2018 5:26 pm

Thanks for the response.. Much appreciated.
MY16 Discovery Sport HSE Lux - Red with Black Pack


Mav71
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Re: Changing tyre size

Post by Mav71 » Sun Jan 06, 2019 11:17 am

One question, Why?


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