Wheel offset calculation

[TGPilot]

Ok...How do I figure out what offset I require on my TGP (or any other car for that matter).

[GnatGoSplat]

TGP is +25mm offset stock. The bigger the offset, the more tucked in it will be.

 

Using that base figure, you can determine that a wheel with +30mm would be 5mm more tucked in. A wheel with +20mm would stick out 5mm more.

 

The offset is actually distance from the mounting surface to the center of the rim, so how much it sticks out is also dependent on tire width, depending on whether you get wider tires or not.

[TGPilot]

25mm stock? Oh crap then a 40mm offset will really hose things up!

 

Well then I guess that rules out 90% of the wheels out there for FWD!

 

I want to go +1 on the wheel size and stay at 8" or up to 9" for a better fit with 255/45/17 8)

[GnatGoSplat]

Yup, 40mm will be pretty darn tucked.

 

Look at Mustang wheels. Very close bolt pattern, slightly larger center bore (70.6mm vs 70.3mm) so it will fit on our hubs, and offset around +24mm or so.

[TGPilot]

Man every wheel I see on the web says 38+mm - 42+mm for FWD GM 5x115 for 7.5 and 8"wide wheels.

 

Not doubting you...but are you sure TGP wheels a +25mm? 8)

[GnatGoSplat]

Positive. Mustang fitments fit the TGP best, IMO.

[TGPilot]

What year mustangs? Any special package...GT or....

[GnatGoSplat]

94-04 I think. I don't know about any special package, but GT's did get bigger and wider wheels.

I know the Cobra R wheels will fit (I've seen TGP's with those).

 

EDIT: I think these would look good on my black TGP if only they weren't so crazy huge, but I like the lip.

[TGPilot]

Actually that is the style I am looking for!

 

Yeah 20" is a bit excessive...don't think the wheel without tire would fit in the wheel-well!

 

Alright...well thanks for the help man! 8)

[GnatGoSplat]

Yeah 20" is a bit excessive...don't think the wheel without tire would fit in the wheel-well!

 

Actually, it would! If you got a 245/30R20 tire, it would be exactly the same diameter as the stock 245/50R16's.

Your tires would be as skinny as the front ones on this guy's BMW. Not really a bad look, but would be a rough ride. Not to mention the tires will cost more than the wheels.

 

I would consider it if I were made of money and wanted the TGP to be a show car that's rarely street driven.

[TGPilot]

If the TGP wheel well surrounds were cut as smooth and round as that BMW that would be sweet. The only problem I see with the TGP wheel well surrounds is it seems to neck down towards the bottom of the facia. So the stock 16's look too small for the wheel well.

 

The TGP would definitely need to be lowered to kill that effect of mis-sized wheels.

 

That is a gorgeous car..the BMW!

[bluegp]

Ok...How do I figure out what offset I require on my TGP (or any other car for that matter).

http://www.tirerack.com/wheels/tech/techpage.jsp?techid=101

http://www.rsracing.com/tech-wheel.html

[z284pwr]

So basically the TGP is running on RWD wheels if its Mustangs, etc. wheels? If so what is the widest you would say to get? 9? Or stick with 8s? And I am guessing 255 is the most you would want, due to rubbing concerns on the front?

[GnatGoSplat]

I think you could safely go up to 9". Yeah, 255 is probably the widest you'd want to get, and even that might rub. I don't know anyone with 255's to comment, although different brands of tires are shaped differently so one company's 255's might not rub and another company's might.

 

Typically FWD wheels have a high positive offset and RWD wheels have a low, 0, or even negative offset. These days, some RWD cars use high offset wheels, so the only difference between FWD and RWD wheels is mainly just the bolt pattern. Mustangs happen to use the same bolt pattern as is used on most FWD cars.

[Intlcutlass]

Offtopic..

 

I LOVE the new sig Shawn

[TGPilot]

Offtopic..

 

I LOVE the new sig Shawn

 

I was going to send him a PM this morning saying the same! VERY COOL!

[TGPilot]

Not to beat a dead horse...but I want to make sure before I order $900 worth of wheels.

 

5x114 will work? :?

 

Seems that on tirerack.com if you enter 2000 Ford Mustang Cobra R it shows a +20mm. 2000 Mustang GT +25mm...

[Intlcutlass]

5x114.3 bolt up fine.

[TGPilot]

5x114.3 bolt up fine.

 

so they are 114.3? So that then means that there is 0.7mm difference in spacing? That is not an issue with the lug nuts? Sorry just confuses me...I worked for my best friend for a while in a machine shop where everything is PRECISION!

 

Alrighty...shit there are alot of selections in that size and for the make/model Muskrat! Much more than I ever thought would work on the TGP!

 

One last note...what tire do I need for the 18" platform? 245/?xx? /18 or 255 ?xx? /18 The wheel is a 8.5" width and 18" of course.

[slick]

.7mm difference for wheelt studs is no biggie. I've heard of people using 5 x 115 before with no problems what-so-ever.

 

Are most of our W-bodies very comparitive to the Mustang bolt pattern, backspacing, and whatnot?

[TGPilot]

What do you think of these Shawn?

 

The car will be painted BRIGHT Yellow in Spring so the Kazera name in yellow will look pretty cool I think.

 

 

[GnatGoSplat]

Yeah, .7mm is tiny. It's .7mm over the whole diameter, the bolt holes are only slightly shifted inwards by half that amount, 0.35mm, very tiny. I run 114.3mm with no problems. The only problems you might encounter is if they don't clear the front calipers. At +25mm offset, they probably will, and I know Cobra R's fit, I don't think the person that had them had to make any modifications.

 

245/40R18 is a perfect match in diameter and width for 245/50R16.

You can try 255/40R18 if you'd like, 10mm wider and 0.3" taller. They would definitely fit on the back, but might rub at full lock on the front (keyword is "might", I really don't know).

 

Nah, other W's use +35 to +44mm offset. GP's with B4U are special, because the body kit and flares is kind of like a widebody kit. However, crosslace are +25mm offset and many people have 'em on Cutlasses and such which normally have a 40-ish offset wheel. I don't think they stick out too much, but I've never seen a non-B4U W in person that has those wheels.

[GnatGoSplat]

What do you think of these Shawn?

 

The car will be painted BRIGHT Yellow in Spring so the Kazera name in yellow will look pretty cool I think.

 

I think they'll look good on the TGP. TGP definitely needs a wheel with lip, I guess because I'm used to seeing crosslace on 'em which has a lip. I'm not sure if I like the silver center or not, I was thinking the wheels being all black except the lip would look good. Although I'm sure it'll look pretty good either way.

 

Yellow TGP, eh? I think that'll be a first!

[slick]

So I'm assuming a set of Cobra wheels or even GT wheels just wouldn't fit right on my Z34... Damn...

[GnatGoSplat]

You could try it. +25mm vs. +40mm is just a little over 1/2". If you can afford them sticking out 1/2" more, they should work. Although if you go from 225 tires to 245-tires AND increase the offset, that's sticking out a total of about 1" more.