I've been looking for new 18" wheels. Currently sporting (?) chromed Vela style. The stock front offset appears to be +49 mm, the rears +27 mm. A common offset number is +35mm. Finding aftermarket 18" wheels with the exact offset has been difficult. How far from stock offset can I go?

 

Here is a basic overview of wheel offset, however there are other factors that come into play, such as the width of the wheel, the tire size you plan to run, types of brakes you have, if your car is lowered and your driving style.

Wheel Offset | Wheel Backspacing | Custom Wheel Offset Chart | Discount Tire

As the F-Type has a HPO (High positive offset) style wheel to clear things like the brakes, suspension and fenders, you are going to want to find something similar to ensure the wheel does not stick too far out (past the fender), but further out than stock, so you can get that nice flush look everyone is always looking for. If you look at the link I posted above, the zero offset style look where the tires/wheels are flush with the fenders, yet still the tires can clear the fenders when under load from the suspension or when you are driving over bumps, etc. The front and rear of the car have different needs as the front cannot house a wider wheel than most likely 9.5 without sticking too far out or hitting the suspension, even if you had a higher offset. Unless you want to run a higher camber to tuck the wheels in, but most with F-Types are not looking for that stanced look.

The rears are different as they can house wider wheels (and tires) and even come that way from the factory, but again, you don't want to be in a situation where you run too aggressive of an offset that causes the tires to rub the fender. You are less likely to hit the suspension in the rear unless you are trying to be too aggressive and run like a 12" wide wheels. Tires are another story, because as you run wider wheels, you also need to consider you will need to run wider tires and if you don't want them to be so thin that you feel ever bump or damage your wheels, it can become too much side wall without rubbing.

The +35mm ET (offset) you are referring too is most often used for the front of the car, the rears are normally in the range from +20 to +25mm, although the factory wheels on the R from 2016 had a +38 in the rear and +55 in the front. Each model year and size wheel have different factory offsets.

Safely you can run an 18, 19 or 20" wheel in the front with a 9" width and an offset anywhere from +35 to +55 without much issue, although the lower the number, the more flush it will sit and hence why so many people choose +35 for the front (with a 9" wide wheel). Go too far though and you are sticking out or rubbing the fender. Why you don't see people running much higher than +32mm. If you went with a wider wheel (lets say 9.5 or 10) you'd really need to be very careful with offset lower than +35 as you most likely will rub the fender with tires.

The rears are most often seen with a 10.5 or 11" wide wheel with +22 to +25mm offset without much concern, some run more aggressive than this and again depending on brakes or if your car is lowered, you may or may not run into issues.

As for finding wheels, I would say most would go with something custom made for your vehicle. Most forged wheel companies build to order, so you can specify you want a specific size, width and offset. In my case, I am lowered on H&R springs (about a 1.4" drop settled over 3 years) with a 255/35/20 front tire on a 20x9" wheel and +35mm ET and then I run a 295/30/20 rear tire with a 20x10.5" +25mm ET rear wheel. I have no rubbing issues and could probably clear a 305"/30 tire in the rear and 265/35 front tire if I wanted that thicker sidewall with slightly wider stance. All of that is a personal preference.

 

here's an easy site to use to compare offsets: https://www.willtheyfit.com but you will need to know your existing dimensions and what has worked for other people. I'm not sure what the width of the 18's are but for the 20' gyrodines, as skizot mentioned, fronts are 9' and 52mm stock so people safely put 15mm spacers w/o rubbing which means you can try to find wheels that are 9' wide with 37mm offset (input these values as your "existing setup"). you can play around w/ the numbers by increasing wheel widths and tire sizes but make sure the overall package doesn't poke out past what others found to be safe. and remember, the lower the offset, the more it will poke out.

 

Thank you. That's a lot of good information. I'm sticking with 18", just bought new Michelins with maybe 500 miles, custom is probably more than I'll want to spend.