Will a 18-inch rim space saver wheel be acceptable on my car with 19-inch wheels? (XF)

[sb53]

my jag XF has 245/40Z R19 98Y tyres on it. The car has the tyre glue and i want to relace this with a space saver. 19 inch used space savers are rare and expensive - can i use an 18inch space saver given it is only a temporary fix
thanks

[Wrinkly]

1 hour ago, sb53 said:

my jag XF has 245/40Z R19 98Y tyres on it. The car has the tyre glue and i want to relace this with a space saver. 19 inch used space savers are rare and expensive - can i use an 18inch space saver given it is only a temporary fix
thanks

Stephen

All be it a "temporary time scale/fix" but I would be very concerned about safety and the balance of the car, let alone any legal matters that may crop up in an incident.

Best Wishes and Regards, John

[The Voices]

Just make sure you use the correct size of space saver tyre on the 18" rim to match the same rolling diameter as the normal alloys.

The optional space saver on many new cars is often a steel rim that is 1 inch smaller than the alloys, the correct tyre size sorts out the difference.

[sb53]

i have done some calculations (hope they are correct) the existing tyres 245/40, now i think the 40 is a % of 245 and is the distance from the rim to the top of the tyre - so 245X .4 = 98mm(x2) +19inches (482.6) 98mm x 2 + 482 =678mm, the 18 inch spare is 135/80 - 135 x .8 = 108 (x2) - 18 inch wheel is 457, so 457 + 216 = 673.
so only 5mm difference.

bought an 18 inch recovery wheel (red - i am informed the black ones do not fit) and it fits a treat. Also bought the circular tool kit and that fits with the cover going flush as it should do. Note a full size wheel would not fit.

As an aside i changed the battery - note  the negative battery lead must lie flush with the battery otherwise the battery fixing bolt will not line up. Bought a ICarsoft code machine as you have to tell the computer that it has had a new battery (apparently it reduces the charging rate which then increases as the battery gets older. 

not a cheap solution but now i have a real tyre and not a can of gunk!