Space saver tyre 15" for car with 17" wheels

Ant555

I have a 15" space saver but my new car has 17" wheels (I thought they were going to be 16 to be honest)

I can see from Googling that its generally OK for a space saver spare tyre to be slightly smaller for a short, lower speed trip but is 15 -> 17 inch difference OK?

What do you think?

born_again

Put tyre sizes in here & look at the difference

https://tiresize.com/comparison/

tacpot12

The size of the wheel is only part of the equation. What i most important is the outside diameter of the tyres. The link provided by born_again will help you assess the difference in the outside diameter. If there is no difference, or just a small difference (<3%), then you are ok. 

A larger difference might still mean the car is drivable (just), but the braking and handling will be badly affected. As it is a space saver, I think I would be incined to consider a difference of more than 3% might sbe enough to get you off the motorway, but you don't want to be going as fast as the space saver allows you to go on country roads. You should probably limit your speed to less than 30mph with a larger than 3% difference, and this would make you something of a liability on the road, but you can probably make it to the nearest tyre shop. 

paul_c123

Actually, the wheel size is the most important consideration - it needs to fit over the front or rear calipers. Does it fit? And also, is this a brand new car or a secondhand one - or to put it another way, is it the right space saver for the car?

BikingBud

I would start here to make sure you get the full details correct as it is not just the tyre size but also offset, PCD, including number of bolts and centre bore size: https://www.wheel-size.com/size/
The above gives options for 16/17/18 as Original Equipment rims for a B class, along with matching tyre sizes.

I prefer Will They Fit as they show the two sizes and where conflict might occur, see for the comparison of MB B class 16 and 18 rims from above:



You might then decide to see what alternative might be suitable and can also consider eBay/facebook purchase with some confidence. 

ETA - I'm old school and now always travel with a full size spare, usually given the crazy world that for some reason OEMs are not obliged to provide one purchased after market, although for one car the best price was from the main dealer.

onomatopoeia99

Ant555 said:

I have a 15" space saver but my new car has 17" wheels (I thought they were going to be 16 to be honest)

I can see from Googling that its generally OK for a space saver spare tyre to be slightly smaller for a short, lower speed trip but is 15 -> 17 inch difference OK?

What do you think?

If all five wheels and tyres were supplied with the car by the manufacturer then the spare should fit and work as an emergency "get you to the nearest kwik fit if you proceed with caution" spare.

If it's some random 15" wheel then who knows if it will even fit over the hub.