Ive been checking craigslist for rims every now and then and just came across some really cool looking boss motorsports 340s. There 20x8.5 with a +14 offset and a 5 on 4.5 bolt pattern. Will these fit right on my car? and does anyone know much about these rims? i googled but couldnt find much about them

 

I cant say for certain that those will fit your car, but the 18" FRPP Bullitts I just put on ours were 18" x 8.5" with a 50mm offset. The stockers were 16" x 7"? and a 39mm offset.

14 mm seem pretty deep dish and may put the rims/tires outside of the fenders, but you will prob get better info from others on here!!!

 

+1...that offset seems to be to little IMO, the offset on my wheels are +45.
Here are the wheels Boss 340

 

Sounds like they're for the earlier cars that came with wheels more like +22 mm.

The outer flange surface will sit almost 1.38" further out than the 18 x 8.5 OE wheels. Measure the clearances that you have now carefully, and keep in mind that if your choice in 20" tires is either wider than 235 or taller than 27" overall that you'll lose a little more clearance. Up front, check also with the wheels steered.


FWIW, cars tend to drive better, can be less "nervous" or "darty" under hard braking, and have a better "feel" at the steering wheel when the offset doesn't differ too much from OE.


Norm

 

+14 isn't enough offset, the lip of the wheels will be poking out.

this link helps you figure out offsets...
http://www.1010tires.com/WheelOffsetCalculator.asp

I found a better one at one point but it's bookmarked on my other computer.

 

That is what they call a medium offset and you will have an issue with it. That spec is made to fit up to a 2004 or older Mustang and it will sit out of the fender.

 

Backspacing is the value you want to compare.
It does not depend on the rim width where as offset
has a direct relationship with the width.
If the rims are the same width as stock, the offset applies.
If the rims have a different width that OEM, then the
offset # goes out the window unless you compensate for
the differences in rim widths.
Backspacing does not care about the rim width.
Offset does....
16x7 39mm offset
17x8 45mm offset
18x8.5 50mm offset
Three different OEM rims with different widths
and different offsets but all stick under the fenders
the same on the S197.

 

You really need both numbers as well as the width.

Backspacing is a quick way of estimating clearance on the inside only.

Offset is a little better at estimating fender-side clearances, and is the number that means more with respect to how the car will end up "feeling" when you drive it.

But you can calculate backspacing from offset (and vice versa) close enough in most cases. The 1" is approximately the total of the two flange thicknesses for alloy wheels.


Offset = Backspacing - [Advertised Width + 1"] ÷ 2

Backspacing = Offset + [Advertised Width + 1"] ÷ 2


Norm

 

Explain the last two statments in detail, Norm?
It does not make sense to me and that means most
others wont get it either...

 

20 x 8.5 on the front usually sits around 30 - 35. The most you want to go is 20. 14 will put you out of the fender and rub with any kind of lowering.