Wrong size spare wheel?

Wheels, Tyres, Suspension, Chassis, Faults and Fixes
Post Reply
Happyhippo
Posts: 3
Joined: Mon Nov 02, 2020 4:34 pm

Wrong size spare wheel?

Post by Happyhippo » Mon Nov 09, 2020 10:33 am

Hi everyone!
I'm the owner of a 2017my disco sport D180 with tow bar and spare wheel purchased new. I'm generally very happy with the car and have had few problems. However I no longer cover the miles I used too and I'm worried about oil dilution. I've therefore ordered a P250DS for delivery 2021 at the end of current PCP.

However....in checking over the D180 to get it ready for handover I noticed that the road wheels are 19" 5021 style but the space saver steel spare wheel and tyre is only 18". Surely this can't be right? I realise that it might get me home and that I would probably have to mess about changing wheels to get the space saver to be one of the rear pair but I thought different diameters on the same axle are inadvisable not to mention being illegal. The car is now more than 3 years old but the spare has never been used.

The reason I'm particularly concerned is that I have plans to swap (if they'll fit!) the 19" wheels and spare with the 20" wheels coming on the new P 250. All because this design is no longer available in 19".

I'll be glad of members thoughts on this course of action and if illegal how best to address this anomaly with the dealer.
Happyhippo

IMG_2647.JPG

IMG_2644.JPG


User avatar
Dashnine
Posts: 3467
Joined: Sat Feb 27, 2016 10:18 pm
Location: Warwick, UK

Re: Wrong size spare wheel?

Post by Dashnine » Mon Nov 09, 2020 11:05 am

The 18" tyre is a different size to the 19" so that there is more rubber (or sidewall) between the wheel and the road, the rolling radius of the tyre on the road
will be the same. It's the same for all tyre / wheel combinations from 21" down to the space saver spare.

The second dimension of the tyre (55 on the 19" and 85 on the 18") is the height of the sidewall in terms of the percentage of the width of the tyre.

Running with the space saver spare fitted is one reason why you're limited to 50mpg / 80kph.
MY19 P240 HSE, Indus Silver, Black Pack, Privacy Glass, 12 Way Memory Seats, Roof Rails, Spacesaver, Cold Climate Pack, 2 x USB in 1st & 2nd rows.
Gone: MY16 D180 HSE Black, Santorini Black

41jules1967
Posts: 260
Joined: Tue May 26, 2020 1:44 pm

Re: Wrong size spare wheel?

Post by 41jules1967 » Mon Nov 09, 2020 11:34 am

As Dashine.
The 17,18 etc only refer to the inner diameter - the size of the physical wheel.

The overall diameter of the tyre (and hence what's in contact with the road) is determined by that, plus the sidewall, which on the 19's is 55% of 235mm + 19" inner diameter (235/55/19) and on the space saver 85% of 155mm + 18" inner diameter (155/85/18)
This means their overall diameter is within 20mm of each other and well within tolerance.
Size of the wheel only matters in 2 regards. The ability to fit over the brakes without fouling, and visual appearance.
2019 Discovery Sport 180 HSE Lux 7 seat & spare wheel - (DIY Fitted Towbar, Mudflaps, Wireless charging pad, Side Steps )
2012 Jaguar XF-S Premium Luxury
Previous - Mercedes (Various C & E Classes), 2 x Freelander2's

User avatar
Dashnine
Posts: 3467
Joined: Sat Feb 27, 2016 10:18 pm
Location: Warwick, UK

Re: Wrong size spare wheel?

Post by Dashnine » Mon Nov 09, 2020 12:33 pm

Dashnine wrote:
Mon Nov 09, 2020 11:05 am
...you're limited to 50mpg...
I wish....
MY19 P240 HSE, Indus Silver, Black Pack, Privacy Glass, 12 Way Memory Seats, Roof Rails, Spacesaver, Cold Climate Pack, 2 x USB in 1st & 2nd rows.
Gone: MY16 D180 HSE Black, Santorini Black

Happyhippo
Posts: 3
Joined: Mon Nov 02, 2020 4:34 pm

Re: Wrong size spare wheel?

Post by Happyhippo » Mon Nov 09, 2020 3:23 pm

Thanks for your help guys. From what you are saying all DS wheels are the same o.a. diameter. It's just the alloy bits which are different diameter. Assuming the 19's fit over the (probably bigger) brakes on the P250 I should be able to swap the wheels and the spare from the 2017 D180.

Andy131
Posts: 99
Joined: Sat Dec 02, 2017 3:33 pm
Location: Manchester

Re: Wrong size spare wheel?

Post by Andy131 » Mon Nov 09, 2020 6:12 pm

Just a couple of thoughts
1) if you are going to swap the wheels over you will need both cars at the same time and a couple of jacks - going to be a bit obvious at the dealership.
2) The first car is on PCP - it's not yours, fairly sure swapping the wheels over isn't allowed. Not that the PCP company should complain about a brand new set of wheels and tyres, but they have been known to be ultra picky unless you are getting another vehicle from them. Which means when you hand the new one back and it's got "lesser value" wheels they will ask for 4 new wheels and tyres at list price.

Might be better to get a set of 19" wheels from an auction website, keep the 20" in the garage and refit them when / if you hand the car back, and that way you don't panic if you kerb the wheels you are using.
And yes 18" space saver is common even if 20" alloys are fitted. 50MPH limit might be because the wheel bolt shoulders are profiled for alloy rims not steel, the space saver is a lot higher pressure (60PSI?).

Good news is when you fit the space saver the Tyre Pressure System obviously has a fit, but when you refit the repaired wheel it resets itself, within a mile or two.
2018 DS HSE Lux.
2017 DS HSE auto, for 45k nice (grey!) car.
2014 Ewok for 6 months, really really rubbish.
2008 FL2 for 185k miles, should have kept her.
2006 FL1 for 110k miles, brilliant car.
2000 FL1 for 100k miles, fell apart but started the LR bug

Happyhippo
Posts: 3
Joined: Mon Nov 02, 2020 4:34 pm

Re: Wrong size spare wheel?

Post by Happyhippo » Mon Nov 09, 2020 6:30 pm

Thanks for this! You’re probably right about swapping wheels but as we all know you don’t get any credit for tow bar a spare wheel on the resale price and it was the dealer who suggested swapping them because I was miffed at not being able to buy this design in 19”.

Past master
Posts: 1321
Joined: Fri Oct 07, 2016 5:30 pm
Location: Isle of Ely

Re: Wrong size spare wheel?

Post by Past master » Tue Nov 10, 2020 5:43 pm

You don't say whether you've ordered a spare wheel with the new car. If you have, it will be the same as the old one, so no need to swap. If not, you will also need to transfer the jack and any fittings you have, such as the bolt to hold the wheel in place. You won't have any problems physically swapping the alloy wheels. The only wheels which might not fit would be 17".
MY16 SETech 180 diesel Santorini Black
Now replaced with MY19 D180 Evoque S (new shape)

Post Reply