Hi everyone,

I'm new to the forum and am interested in getting new wheels. I did some searching but since most people seem to be running 19s or 20s, I couldn't find much information on 18" wheels.

I have a G25x, and I like the concave look for wheels, so leaning towards Forgestar F14s.

It seems like 18x9 running 245/45/18 should fit for the G25x, is that right?

Also, what would be the lowest offset possible to maximize the 'concave-ness' (if that's a word) for 18x9 wheels?

Would 18x9.5 also fit, or would that cause rubbing?

Thanks for your help! This forum is awesome.

Cheers,
James

 

The amount of concave will be the same for the wheel of the same width, more often than not. I believe the widths on those wheels will affect the amount of concaveness, the Offset wont affect the degree of concavity. They either add or take away from the amount of metal on the hub area to account for it. So with that being said, you will have more concaveness on a 9.5" wheel than you will with a 9" wheel, regardless offsets. Do you plan on lowering the car at any time? Seeing as you're from toronto i doubt you're looking to do any type of lowering mods. A safe offset with a 9.5" wheel would be around +40, +45 or so in the rear and about the same in the front. With the 9" wheel, which may be more suitable for you're setup would be in the area of +35 in the front and around +40 or so in the rear. This will give you a good looking setup that isnt too far sunk into the fenders at a stock riding height

 

Thanks so much for the response. I always thought offset affects the concavity of a wheel but your explanation makes total sense, that the concavity is based on wheel width and not offset.

I am unsure whether I will lower my car for now. I was reading through some threads in the forum and maybe Swift springs if they become available for a mild drop. I do find the stock gap is pretty big for the G25x, even for Toronto standards

How does lowering the car affect my choice of wheel width and offset?

 

When you lower the car, the wheel tucks in further into the fender/closer to the middle of the car leaving more gap between the outside of the tire and the fender. This is referred to as camber. All the suspension components work on pivot points...so when you put a lowering spring on, it causes the hub to be pulled up and further away from the outside of the fender. Its hard to explain, and much easier to see. If you have some engineering background, or just good with spatial relationships then its a pretty easy occurence to understand. When i was on stock suspension, i was running a 8.5" +35 wheel in the front. When i lowered the car with Eibachs, that 8.5" +35 was now very tucked inside of the fender and i had to add a 15mm spacer between the wheel and the hub to bring the wheel further out to be more flush with the fender. When you lower your car, you generally will want to run a lower offset to keep the wheels from looking silly from being to tucked into the fender.

 

That is a great explanation. I do have an engineering background actually I have read on other threads about lowering the car will affect camber and offset, and now I understand why.

It now also make sense why people on other threads recommend lowering the car first before getting wheels.

Is there a way to actually determine the difference in offset in relation to how much the car is lowered by? Or is it more or less guesswork/experience?

Thanks,
James

 

Its more of a guess work type thing. There are ways to measure it of course. But it involves removal of the wheels and being able to compress the suspension to be in the same position it would be with full weight on it. Each lowering spring lowers the car a different amount. So lots of people just play around with different setups. If you purchase a wheel from a vendor on here, just tell them your situation and they will be able to help you choose the correct offsets. Also, there is a vast amount of information on this forum regarding offsets and lowering springs with tons of pictures of peoples setups. Just search around and you're bound to find any information you could need.

 

I'll definitely do more research and checking out other's setups in the forum. Thanks again for all the information and help.

Cheers,
James

 

Great reply!!

I'm in the same boat.. I have 09' G37x and Eibach's are getting installed on Thursday..

I'm buying the rims online, I'll probably go conservative 35mm offset and get spacers..

I've decided on a set of Ace Alloy Executives 19x8.5's with 245/40/19 tires..

The offsets offered are 20,35,38 and 40..

 

Great thread! I'm not sure why I never found this sooner, since it's been up for a few months. But, very helpful. I'm getting ready to buy rims and keep saying I won't lower it, but I get tempted every day. I really can't believe lowering it required you to add in 15mm spacers! I would have assumed something like 5mm, but 15mm seems like quite a difference. I never would have thought; good to know.

So, if I were to go the coilover route, are they easy enough to adjust height on them? I only ask because I'd love to get closer to stock height when I swap the winter (stock) rims back on, then lower again in the summer with new rims. Is this feasible?

Thanks again!