# Wheel Research



## LS2 MN6 (Jul 14, 2010)

I did some searching on the topic which only confused me more.

I'm looking long term to replace my wheels (I'd like to go 18" or 19")

BBS has some new wheels for the GTO, the 18" are 18 x 8 and the 19's are 19 x 8.5 with a +30 mm Offset and I think a 6.22" backspacing.

I'm almost certain the 18's are identical to stock in width and offset (hence no offset being listed). However I don't know if the 19's will rub. I think they would but I'm not sure.

235/35's would be on the 19's and whatever the stock GTO 18" size would go on the 18's.


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## LS2 MN6 (Jul 14, 2010)

They look like this:


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## Discount Tire (May 9, 2008)

The 19x8.5 +30 will most likely need fenders modifications front and rear. 

In 18", if the width is 8" then you'll want the offset anywhere from +35mm to +50mm. +40 to +45mm would be ideal.


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## LS2 MN6 (Jul 14, 2010)

Discount Tire Direct said:


> The 19x8.5 +30 will most likely need fenders modifications front and rear.
> 
> In 18", if the width is 8" then you'll want the offset anywhere from +35mm to +50mm. +40 to +45mm would be ideal.


Good to know!

I did some digging the offset on the 18's is 38mm (Another finish of the same wheel lists it). So I think that should be OK no modifications.

GTO's don't have TPMS so I can swap between two sets with no reprogramming I would assume. I'm keeping my old 17's for the winter (and eventually when the DWS's wear out I'll put on Blizzaks or some other snow shoe).


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## Discount Tire (May 9, 2008)

LS2 MN6 said:


> Good to know!
> 
> I did some digging the offset on the 18's is 38mm (Another finish of the same wheel lists it). So I think that should be OK no modifications.
> 
> GTO's don't have TPMS so I can swap between two sets with no reprogramming I would assume. I'm keeping my old 17's for the winter (and eventually when the DWS's wear out I'll put on Blizzaks or some other snow shoe).


18x8 +38 is still a tad aggressive especially in the rear. Double check for spring sag and cradle alignment. If either is a factor, you'll have tire rub on the rear fender lip.


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## LS2 MN6 (Jul 14, 2010)

Discount Tire Direct said:


> 18x8 +38 is still a tad aggressive especially in the rear. Double check for spring sag and cradle alignment. If either is a factor, you'll have tire rub on the rear fender lip.


Good to know. I guess the Pedders Repair kit I was looking at (along with an alignment) will happen before the wheels!


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## LS2 MN6 (Jul 14, 2010)

OK I did some more research:

Stock 17's are 8" wide with an offset of 48 mm.

That means the distance from the back of the wheel to the mounting point is 5.89" (4" + 48 mm)

The 18's are also 8" wide with an offset of 38 mm

That means the distance from the back of the wheel to the mounting point is 5.50" (4" + 38 mm). This would mean the wheel shifts outboard .39" from the current location (moving the wheel .39" away from the inner fender, and toward the outer fender)

The 19's are 8.5" wide with an offset of 30 mm

This means the distance from the back of the wheel to the mounting point is 5.43" (4.25" + 30 mm). This would mean the outer part of the wheel moves .07" outboard while in inner portion moves .43" inboard (since the wheel is .5" larger)

So based on this outer fender modifications for the 18's is actually worse that the 19's. But both shouldn't really be an issue as .39" isn't that much movement. However .43" inboard I think might pose a problem with strut rub? The tires are however thinner with the larger rims being 235's not 245's making up .2" on each side. Thus the actual inboard increase is only .23" for 19's as well as the actual outboard decreasing for 19's and increasing .19" for 18's.

That all makes sense right?


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## AlaGreyGoat (Jul 6, 2006)

8in wide rims are actually 9in wide. The 8in is the inside bead width.
8in with 48 mm +offset (Stock) would have a a backspace of 6.39in.
This is the MAX backspace for the front to clear the struts. I tried to run
255/45/17 tires on the front and had to run a .200in spacer to clear the strut.
The stock 245/45/17 almost rub.
8in with 38 mm +offset would have a 6.00 in backspace.
They will stick out to the outside .39in more than stock.
Should work front or back with 235 or 245 tires.
8.5in rims with 30mm +offset have a 5.93in backspace. This will stick out 
.96in more than stock.
Should also work front or back with 235 or 245 tires.

Larry


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## LS2 MN6 (Jul 14, 2010)

AlaGreyGoat said:


> 8in wide rims are actually 9in wide. The 8in is the inside bead width.
> 8in with 48 mm +offset (Stock) would have a a backspace of 6.39in.
> This is the MAX backspace for the front to clear the struts. I tried to run
> 255/45/17 tires on the front and had to run a .200in spacer to clear the strut.
> ...


The 8 inch being the bead width is good to know. I was wondering why my backspace numbers didn't quite match the ones online. Now I know why.

So a backspace of 5.94" (18's) and 6.22" (19's) shouldn't pose a problem for strut rub (those numbers are from the spec sheet of the wheels). Hmm. More to think about.


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## AlaGreyGoat (Jul 6, 2006)

Here is some good info:

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

Larry


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## Northeast Rod Run (Oct 29, 2008)

the 8" rims you are looking at with the 38mm offset is IN NO WAY going to give you strut rub problems. The reason for this is because your wheel will be 10mm FURTHER away from the strut than the stockers.

your potential problems are going to come from the outside. You might hit the fender or quarter panel lips, depending on how the brand of tire that you choose runs (really wouldn't worry too much in front though). I would suggest staying away from anything under a 40mm offset. JMHO


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