What better place to get help on this subject. Here's my scenario:

Narrowing 9" rearend -3" off each side. I aint worried about the race wheels, 15x10 5" BS. But I want to run a 17 wheel for street use, prefer to run the ZR-1 Style, but havent found the right BS/offset. What should I be looking for as ar as a wheel bs or offset to tuck under the fender? I was thinking a 17x11 or 17x9.5 (common sizing) but the BS I would think would have to be same as race wheels to clear, so that would be 5" +/- .5", does offsets play any part of this equation or is just another way of measuring backspacing? Please help.

Charlie

 

Offsets are another way of measuring backspacing.
a 10" wide rim with a 5" backspacing has a 0mm offset.
a 10" rim with a 7" backspacing would be a 50.8mm offset
a 10" rim with a 3" backspacing would have a offset of -50.8mm
1" is roughly 25.4mm

To put a 11" rim on with the rear shortened 3" so it will fit like a 50mm offset on a stock rear; you will need a 4 11/16" backspacing or a -26.2mm offset.
That’s 'negative' 26.2mm.

 

You can only go 1” wider, any more then that and you will need a spacer.
They can only widen the back of the stock rim so all the new width goes toward the inside.
With 1” you will need the BFH and probably tubular lca’s
If you want to go 2” you will need a 1” spacer to even it out;
1” toward the inside and 1” toward the outside.
To get it to fit just right you would widen it by ¾” and use a 1 ¼” spacer
That would get it to sit like a 50mm offset 11” rim
That’s just from what I can measure using the chart, someone who has done the actual procedure could tell you more accurately.

 

Thats what I was hoping the answer would be. Thanks. Guess when the rice took over the scales and measurements they brought with them "offset" just to **** my backspacing up Now, gotta find a 17x9.5/11 with -26mm to 0mm. Ughh.

 

I was wondering if there is a way to fit a 20" rim on a 2001 ws6. what would be the widest tires i could use? rim width? offset? i was thinking about the Foose lusoany help would be greatly appreciated.

http://www.discountedwheelwarehouse....ShowLarge=True

 

20 a little odd to me on a f-bod but......

should be the same as all the rest, you can go 11" wide w/ a 50mm offset, you could go 55mm if you do alot of inner fender hammering.

Tire size... I would go 295 / 25 / 20 - that gives you a 25.8" tire height
Stock 275/40/17 is about 25.66"

Front go 9 1/2" 56mm offset of 10" 50mm with a 275 / 25 / 20 but I dont know if they make that size.
let me re-check and Ill get back to you later

 

Take another look at that wheel package, they are 8.5" wide and for front wheel drive cars.
Good looking rims. 20" on a f-body though?
Hope you have smooth roads around you. You hit a grain of sand in the road and there ganna be bent.

 

Thanx. they make those wheels in a couple different widths, i don't want to do any mods to the fenders, and don't want the tires to rub. i got this link to try to see what the backspacing is, i'm guessing it's what "ET" is...i really like those rims. i'll be moving to phoenix AZ, don't quite know how the roads are over there...don't you think 25 is too skinny?

http://www.mhtwheels.com/pdf/specs/L...ech%20Data.pdf

 

so for a 9 inch wheel i would want like 38mm of offset?

 

what determines whether the wheel going to pop off the body or not , cause i`ve seen 10' wheels but one is travelling out of the fender border and the other one is was exactly at the fender edge and thats what i want , both wheels were with no spacers , thank u TTSSZ ur drawings really took me to the level of understanding ..
any one can answer me .. of course there is

 

Hope you don't mind another question. I'm wanting to go with a 16X8 with a 5.5" backspace (Centerlines) F & R. My front is lowered 2" and rear is stock. Will these fit my car?

Thanks for any help or advice. Jim

 

A 10" with a 42mm offset will sit very nicely in the well.
A 36mm will be almost flush with the outer lip I think.

I have 10" 42mm on the front and tried them on the back to see how they fit.
They looked perfect.

 

I would go wider the 8".

They would sit 1/2" further out then stock at the outer wheel well.
The inside of the tire would sit 1 1/2" further out from the inner wheel well.

5.5" backspace on a 8" rim is about 30.6mm offset

Go with a 9" with a 7" backspacing, 56mm offset (same as stock) if you want to stay with a thin rim. That will work with a 2" drop no problem.

 

TTSSZ, I really appreciate the info and advice. Jim

 

TTSSZ thank u for understanding what i mean exactly , another thing .. i know it is a silly question .. but i thought about it alot and i didnt arrive to a definitive answer anyways it is directed to anyone who knows the answer .. how to determine the maximum and the minimum tire size for a wheel size , for example , stock trans am 16 inch wheels are 8 inch , factory tire size is 245 , am using 255 , what is my max limit , can i go 265 , and why?, .. can i go 225 , also why ? is it just trying the tire without any formula ?

 

It’s really quite simple.
You don’t want a tire to be more then 1 ½” wider then the rim.
All you have to do is translate from metric to standard measurement and it becomes clear.

The factory will keep the tires around 1” to a 1 ¼” wider the rim.

Example……. your stock 16x8” rim has a 245mm tire stock.
The 8” rim is really about 8 ½” wide out to out. 245mm = 9 21/32”
So there is about a 9/16” overhang on each side. 9/16 + 9/16 = 1 1/8”

With your 255mm tire in a 8” rim you have about 25/32” overhang each side.
255mm = 10 1/32” ------- 25/32 + 25/32 = 1 9/16”

The 265 would be in my opinion just a little to big.
265mm = 10 7/16” that would give you 31/32 overhang on each side.
31/32 + 31/32 = 1 15/16”

Looking at a 11” rim----------

If you run a 315mm tire --- that’s 12 13/32”
The 11” rim is about 11 ½” out to out. That gives you about a 15/32” overhang on each side.
15/32 + 15/32 = 1” --------That’s a nice fit.

I have 325mm tires on a 11” rim.
325mm = about 12 25/32” ---- That gives me a 21/32” overhang each side
21/32 + 21/32 = 1 5/16” - A nice fit.

Now you should understand why you shouldn’t put a 315mm tire on a 9” rim. (9 ½” wide out to out)
315mm = 12 13/32” ------That gives you a 1 7/16” overhang on each side.
1 7/16 + 1 7/16 = 2 7/8” Not a GOOD FIT.

Confused?
Good, now on the flip side you don’t want to get a tire that’s narrower then the width of the rim.
That’s easy. So a 225mm tire is about 8 21/32” wide
The 8” rim is 8 ½” wide. So that’s about as narrow as you want to go.

(All numbers + or – a 32th or 2)

----------------------------------------------------------------------

The other factor you want to consider is the circumference of the tire.
If you want a wider tire in the back then in the front, and most of us do,
You want to choose a set that has a similar diameter.
All you have to do is look at the tire charts and match up a set.

For instance……….

275/40/17 matches well with 315/35/17 (80.61" cir. to 80.67" cir.)
275/35/18 matches well with 325/30/18 – (80.33" cir. to 80.64" cir.)
that’s the set that I run.

 

simply .... THANK YOU VERY MUCH .... i do have one other question about tire/wheel fit .. THE PROFILE 16" goes with 45 sometimes 50 ... 17" goes with 45 sometimes 40 .. 18z goes with 35 .. etc etc .. are we just considering the ratio ? 24 , 25 .. 28 etc .. OR there is something else we should consider ? traction , rigidity .. etc ? this is generally for a street use ..

same question for the drag use ? but with different inputs .. what is the effect of the profile on the grip ? cause ive seen 15" with too much rubber ( over all 30 inch , wheel +tire ) and a 16" with a little rubber but still 30" over all ..

 

thats what she said

 

I got 15x10 Weld Prostars with a 51mm offset in the rear, is that ok? I'm running a 325/50R/15 Nitto drag radial.

 

HEY FELLAS...I HAVE A 1997 Z28..I WANT TO RUN 19x10'S CHROME C6 ALL THE WAY AROUND ON MY CAR...WHAT WOULD THE OFFSET HAVE TO BE FOR BOTH FRONT AND REAR TO SIT PRETTY MUCH EVEN WITH THE FENDERS...WITH OUT RUBBING OF COURSE...THANKS IN ADVANCE...