Running 18” alloy as spare while rest are 17”

[dynamis_dk]

So making to switch to get the seat sound upgrade and I’ve currently got a 17” fully size alloy in the ST as a spare. It’s looking like I need to go 18” if I want to retain a spare and as the ST has room, I’m minded to go for the full size just so speed limit isn’t an issue (50 max on the space saver right?)

Although I would always seek to get my 17” fixed and back in the car asap follow a flat, is it ok driving a car with one 18” alloy with rest 17”, as long as the overall tire circumference is the same?

 

[BigJase88]

Yeah that will be fine

 

[dynamis_dk]

Awesome, cheers mate. Now I just need to see if I can find one cheap

 

[Glosphil]

If your spare wheel & tyre are a different size to those on the car using it will legally limit you to 80kph (50mph).

 

[dynamis_dk]

Even if it’s a full size alloy wheel of different size but the tyre sized to match the overall circumference of the other tyres on the car?

 

[RUM4MO]

Even if it’s a full size alloy wheel of different size but the tyre sized to match the overall circumference of the other tyres on the car?

I'd say so, I know that the "full sized" but the 15" optional size of steel spare that my wife's 2015 Polo has - it has 16" alloys from factory, does have a warning on it pointing out the applied limitations of use.

What you do get from a "full sized but different size to what is on the car spare" is extended milage/usage before needing to change back after getting a repair/replacement tyre/wheel - and in my mind that counts for a lot if you are on a long journey.

Edit:- obviously your plan must be to get the removed tyre/wheel sorted out ASAP and swopped back onto the car - the same, I believe, now applies even where an exact same but steel spare is provided to replace an alloy wheel and tyre.

 

[dynamis_dk]

I had sort of presumed the speed limit imposed on the steel spares are due to a combo of smaller width and tyre design so hadn’t really given it a lot of though.

In most cases for me, using a space would be to get me home / to a repair place so I’d be looking at minimal use but it would be annoying if it occurred on the motorway, to then be stuck traveling at 50mph for the rest of the trip

 

[Glosphil]

If the spare wheel/tyre differs to those on the car in wheel diameter, tyre width or tyre profile then when fitted the car is legally limited to 50mph.

 

[RUM4MO]

Needing to drive at 50MPH for a long motorway journey beats only being allowed to drive for maybe 30 or 50 miles with a "bike slick" spare tyre on.

 

[BigJase88]

Spare space savers are usually a different rim size than the full alloy.

Sometime like a 15" spare / 16" spare.

With an 18" it will fit over the caliper no probs so there wont be an issue.

 

[Glosphil]

Needing to drive at 50MPH for a long motorway journey beats only being allowed to drive for maybe 30 or 50 miles with a "bike slick" spare tyre on.

I completely agree; but many cars have a spare wheel well that is too shallow for any wheel/tyre wider than a spacesaver. My 2018 Leon FR hatchback is one such car.

 

[RUM4MO]

Before I took delivery of my 2011 Audi S4 when it was 2 years old, I knew that it had a space saver spare wheel, but failed to take in that its battery is in the boot - in the spare wheel well, so I found and bought a good used wheel and tyre - and then was a bit disappointed!!

 

[Glosphil]

My last car, a 2012 Mk2.5 Octavia vRS, had 225/40-18 tyres but a 205/55-16 spare so limited to 50mph with the spare fitted.
I made & fitted a wood frame to raise the boot floor to allow me to fit a matching 225/40-18 tyre/wheel as a spare in the wheel well. As the Octavia had a large boot the small lose in boot capacity didn't matter.

In 6 years I used the spare twice! The second time was a 400
mile trip across France on a Sunday to catch a ferry so my efforts were definitely worthwhile.