how to tell if an alloy is 5x100 or 5x114?
 

say you have a mystery alloy, how do you find out if its 5x100 or 5x114? any markings i should be looking out for?

on the underside there is:

18x7.5J
ET45

Well obviously it's an 18" wheel and 7 1/2" wide with an offset of 45mm.

To measure it's PCD try:
http://www.towingandtrailers.co.uk/s.../165/index.htm

Rule of thumb, classics, bug and early blobs are 5x100, it was around MY05 that the 114PCD came out on the STi's

but hawk wrxs are still 100 pcd

Measure from the centre of one of the bolt holes to the centre of the centre bore,if it is 50 mm,its a 5x100,if it measures 57 mm,its a 5x114,hope this helps

i try and go by that, but the situation is that i recently checked my spare, the tyre was knackered and alloy a bit on the rough side, i should've checked sooner after buying the car tbh.

so its more for my own peace of mind because if the previous owner didn't care about the condition of the spare, i just wanted to make sure the thing would go on properly in the first place! ..hence asking about checking for the correct PCD.

Jack it up, remove one wheel and try it?

But SURELY you wouldn't use that thing you showed us yesterday?

going to be honest, I am but obviously with new rubber. it is only to be a spare so if I got a puncture all I need it for is to get me to a garage to swap the rubber over.

Wow.....that wheel has had such a clout, I'd be worried about it cracking.

i'm looking at the space saver route now, my initial reasoning for the mangled spare was it only ever going to be used as a very short term stop gap to drive and get the punctured tyre replaced, as it was damaged and the wrong colour anyway.

but that got me thinking that i might look at space savers (it would only be used long enough to get to a tyre place and plus it saves a bit of weight too) but that might need unnecessary switching unless space savers have enough clearance for standard 4 pot fronts?

any issues (apart from the obvious: take it easy) if using 18's and probably what will be a 16" space saver?

i would like a full sized spare though but there are hardly any around, its either sets of 4 or nothing :(