One of the valves of my 18inch tyres is leaking, taking it to be repaired tomorrow. Not considering using the space saver to get there but could it ever be used with a 2inch difference or is it completely useless now?
So long as your rolling diameter remains the same there shouldn't be a problem. Depends on the tyres you've got on your 18's i guess
What is the tyre on the spare? Put the opposite side Advan into this calculator and you'll see how different they are in height after adjusting for tyre profile. http://www.1010tires.com/tiresizecalculator.asp
There should not be any difference in the Rolling Diameter of a properly fitted tyre on an 18" rim on your car. If there is, then your Speedo will be way out of whack(and defect-able). The only problem with using a stock Space-saver is if you have a bigger(324mm)front Disc Brake upgrade(as your stock Space-saver will not clear the front Callipers).
So then You put one of the back wheels on the front to clear the big brakes and put the space saver on the rear to get you where you are going to, rated at 80kph, so take it easy and you wont have any problems.
I hate to disagree here but you are better off having the space saver on a front position if possible. having 2 even slightly mismatched rolling diameters is hard on the diff and can cause issues if used to much or the diff is getting slighty older and worn. its to do with the engine trying to turn them both at the same speed but one behaving like you are forever turning, ie needing to rotate faster than the other side for the car to travel any given distance.
Picky, picky Of course your better off having the space saver on the front, but if it wont fit over a big brake kit, then you can do as i suggested to get you out of trouble, not as if your going to travel long distances to get help. The motor has nothing to do with it, it's the differential thats doing the work, thats why they are fitted with LSD's, and the Zed diffs are pretty much bullet proof anyway, Everytime you turn a corner the wheels are spinning at different rates, so i don't think a short drive with odd sizes is going to cause to many problems.
Space savers are only recommended upto 80km/hr. Take your time getting to your destination. You'll be fine
I was always under the impression that for safety reasons, particularly under braking, you should always fit a space saver to the rear if possible, regardless of car and FWD/RWD/AWD configuration.
I drove home with my space saver on the rear when I run 20" runs about 65k down the highway at 70km/h when I had a blow out . Not a big issue
