Choosing wheels

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warpc0il
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Choosing wheels

Post by warpc0il » Tue Apr 25, 2017 7:19 pm

This answer is definitely worthy of an entry in the FAQs...
PeteH wrote:First thing is holes! Without the right holes your wheels simple won't fit. You obviously need 5 holes. But you also need those holes to be at 114.3mm "pcd". Pcd stands for "pitch circle diameter", and it is simply the diameter of the circle that the holes sit on. Many jap cars have 5 hole wheels with 114.3mm pcd. Most German cars also have 5 hole wheels, but they are on a smaller diameter, so be careful because wheels for German cars won't fit Japanese cars.

Second thing is diameter. Standard s1 wheels are 18" (inches). You can change the diameter to 19" without issues, but you will need to fit lower profile tyres in order to keep the overall diameter the same. If you want to go to 19" then post on here and someone will work out which size tyre you need. You can sometimes fit 17" wheels as well, but you'd be unlikely to want to for a road (as opposed to track) car.

Third thing is width. Standard s1 wheels are 8". Again you can go wider, but you do need to be a bit careful. 8.5" is probably fine. 9" is possible, but you will need to space them away from the car a bit so that they don't foul the suspension and body. People use spacers to do this. A 15mm spacer would be about right for a 9" wheel (people reading this will be screaming "what about offset", but I'm trying to keep it simple at this stage peeps...). If you go wider you should fit wider tyres as well. Again, if you want to go wider then post on here and people can advise.

Fourth thing is "spigot diameter". This is the diameter of the centre hole (where the badge goes). On the RX-8 it is 67.1mm, and it is usually different for every car. If you order new wheels they will usually come with a plastic "spigot adapter" to fit into the centre of the wheel to reduce the diameter to the correct size for your car. Some wheels are machined correctly for your car (so don't need an adapter), but this is rare. You should make sure that if you buy second hand wheels they have the correct spigot diameter, or the correct adapter. Fitting wheels without this adapter is possible, but it will put a lot of stress on the wheel studs, so it is not advised.

Last thing is offset. The RX-8 has a very unusual (large) offset. This is the thing described as "ET50". This just means an offset of 50mm, which is the amount by which the wheels will stick out. This can be confusing though, because it works backwards, so the larger the ET value the less the wheel will stick out (stupid eh?!). So the RX-8 has a very large ET value, which means the wheels don't stick out very far. If you fit wheels with a more normal or common offset (say ET35) then they will look like they stick out a long way on the RX-8. Again this may not be an issue, but if you want to choose a different offset then again post on here and someone will advise.

Oh, and forget "J". This is a rim description, but every rim you see will be a "J" rim.....

So to summarise, the RX-8 has 18" x 8J" ET50 114.3 wheels. If you find aftermarket wheels of exactly this description then you are fine. If you find aftermarket wheels that are close to this spec, and you like them, then post on here and someone will be able to tell you if they fit.

It's not quite as daunting as it appears, and it's good fun hunting.
Hope that helps.
Thanks Pete :thumright:
Dave
The Spin Doctor ™
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