Your assuptions thus far are correct for offsets (big number, rim sucked in towards car, lower offset, pushed outside of fender). To figure offsets on rims....... most of the time, it will be stamped on the wheel inside, or on the mating surface of the hub section. If nothings there, measure the wheel width overall from outter most lip to outter most lip. Remember, wheels are sized by the BEAD and NOT overall size. Ex: 17X8 wheel will be nearly 18" in dia and 9" wide. 17X8 is the measurement of the bead seat. OK, now you have the overall measurement, get a straight edge long enough to go across the entire rims diameter. Now place that straight edge accross the wheel, and use another straight edge and measure the distance from the hub mating surface of the inside of the wheel, to the perpendicular intersection of the straight edge going accross the rim. This measurement is called backspacing. Now subtract half of your overall width from your backspacing. this is your offset. But wait, its in freakin inches. Now simply multiply your offset number by 25.4 to convert to milimeters. Now you know the rims offset, and its usable info cause its in millimeters.

Lets use the 17X8 wheel for example again. Lets use whole numbers for simplicity. We measured a overall rim width of 9.0". We placed the straight edge over the rim from lip to lip, then measured down from that straight edge to the hub section of the wheel and got 5.0" backspacing. 5.0" back spacing minus half of overall width (9.0" / 2= 4.5") 4.5"-5.0"= -0.5". You have -0.5" offset. -0.5" X 25.4mm = 12.7mm offset.

~Mike.............

 

ok, i think i got it.

these are the wheels i have: http://www.americanracing.com/wheels...ated&section=P
I assume mine is the very top one (17x7) because that's the 17 one with 5 bolts (apparently, they don't use millimeters). The wheels came on my car, so i'm not positive of the offset, but i assume it's 42.

I want to keep the tires and i'd like to push the wheels out a little more (but not out past the fenders), so i'd be fine with 17x7 with a 30-40 offset?

so far these are my favorite:
http://www.autornd.com/catalog/produ...87913068caa08f
(in black )

 

No problem.
Stock Turbo II / GTUs wheels are 16" x 7.0", +40 - so the rim width and offset are identical.
You're just going with a larger diameter wheel with the 17".


No.
You're going 0.5" wider, but you're going 5mm and 8mm, respectively further in.
The 7.0", +40 is already a tight fit, so I doubt those wheels will clear everything inside.


-Ted

 

7.0", +42 is too tight for my tastes.
But we're talking about 2mm difference versus the stock 16" wheels.
It might be okay, but be prepared to run a thin spacer just to get enough clearance.

Yeah, in fact, I like a 7.0", +35 to fit in the stock wells.
I run this spec on my car currently - 16" x 7.0", +35 with 225 / 50 / 16 tires.
Clearance is not a problem.


-Ted

 

yeah, I didn't realize how far in the wheels were till I looked at that picture above, paying close attention to the wheel position.

as far as I know, there might already be spacers on the wheels. I haven't removed the wheels since I got the car, so i don't know.

 

Will these fit under the stock fender with a stock suspension?

Work Rezax
17x8 +35 front with a 225/45 kuhmo ecsta 711 tire
17x9 +35 rear with a 255/40 Kuhmo ecsta 711 tire

I've read through many pages in this thread and some say the 225 tire won't fit up front with out a spacer so should I go for a 215 up front and 245 or 255 in the rear?

 

2 questions:

1. will any 5x114.3 wheel fit an fc (assuming width, offset and diameter are ok)?

2. should offset go up or down for a wider wheel? i have 7" wheels with 42 offset (which i think is too much). if i go with 8+" wheels, should i go with a higher or lower offset?

 

might rub the strut just a hair in front... you could go with a 215, or a slight spacer(like 3-5mm) rears should be fine.

1: and assuming the hub center bore is big enough (which would be crazy if it wasn't for these cars...), yes.

2: lower offset.

http://marksink.com/tire_wheel_offset/offset.html

 

AAAHHHHH Sunken Battle Ship!!!

dont get a 7" wheel you will regret it later. get an 8 in

right now i am currently running 17x8+20 in front and 17x8+30 in the rear (same wheel just i have a spacer in the front.) 245/45 tyres, which is the reason why i had to get spacers in the front in the first place. rolling the fenders isnt a big deal, so dont be scared. here is a shot of my front wheel gap with slightly rolled fenders,

and here are my sunken battle ship rears

you can run 17x8+30 offset wheels without a spacer if you ran 225/45 or 225/50 tyres. and they will look decent here are 2 rx7s with the same wheels and tyre size running a 17x8+30 wheel


i am currently running about 2.5 deg camber in the front and 1 deg in the rear. 1/8 toe out in teh front and 1/8 toe in in the rear (will be changed by the end of this week due to massive subframe revamp.)

if i had the money i would be running 17x8+10 in the front and rear. using a 225/50 tyre for dailies, and for the track i would be using a 17x9+20 235/45

 

my current wheels are more like deep sea submarine in a trench

 

my tires are 215/40 front and 215/45 rear
will they fit on 8" wheels?

 

strech em! with great fitment stretched tyres look amazing. here is a prime example on an Rx7

 

i think we need to start a new thread with only pictures of Rx7s with great wheel fitment.

talk is great but visuals are sooo much better

 

yes.

 

yes, I agree.

 

Backspacing is the distance from the hub face to the outside lip of the wheel. Lets take your original example of a 7 inch wheel with 40mm offset. The advertised width of a wheel is measured at the tire bead lock area of the wheel. This dimension is useless when talking about backspacing. The width of a 7 inch wide wheel when measured at the outer lip is actually 8 inches. So when calculating backapscing, you must add one inch to the advertised wheel width. The rest of your calculation is right on the money. We take 8 inches/2=4 inches. We add the 40mm (about 1.5") and we get a backspacing of approximately 5.5" on a 7 inch wide wheel with 40mm offset.

Andrew

 

Um, digging up old parts of the thread?
I've already got corrected on this.
The lip isn't calculated into the offset when compared to backspacing.
Add anywhere from 1/4" to 1/2" to compensate...
It's really close enough unless you want to run really tight on the offset.
This is why I don't like to go more than +30 offset on a 8.0" wide wheel.


-Ted

 

I was just reading the thread hoping to find information and saw what you wrote in the first few pages and thought it would be of benefit to clear it up. Apperently you already did that in the 100 pages of this post. Actually being off by 1/2" is a pretty big deal, considering guys are asking about offsets that differ by 5mm at times. Someone should really clean up this thread. There is a ton of good information, but its all over the place.

Andrew

 

Yep, you're right on all counts.
Backspacing specs are usually from drag racing wheel applications.
Most aftermarket (street) wheels use offsets.
We're trying to keep the discussion on offsets.

I wish it could be cleaned up.
I'm not a mod in here.


-Ted

 

with 2.5" coilovers, rolled fenders (not flared).
what sorta offset could i squeeze a 245 or 255 under the front on a 8.5 or 9" wide 17?

 

9.0" wide?
I'd go with a least a +20 or smaller offset up front.
It's going to be really tight though, especially with a big drop...


-Ted

 

how about a 245/40 on a 17x8.5 +25 up front?
i think thatd fit decent front and rear, not sure how perfectly flush. mostly worried about biggest tire to cram up front w/o rubbing on rolled front fenders

21,000posts now ted? geez

 

That might fit, but it'll be tight.
Cross your fingers?
I don't usually like to run "half sizes".

Yeah, got nothing better else to do at work.


-Ted

 

Agreed that most modern wheels are going to the offset way of measuring wheels. However, backspacing is great if you have a used wheel and are unsure as to how it will fit on your vehicle. Here is how you measure backspacing:



When you combine backspacing information with the sectional width information for a particular tire, you will really get a good idea of where not only the wheel, but also the tire will sit in relation to suspension parts and the fender.

Andrew

 

see attached pic for chart