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18x8 or 18x8.5

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cbr600rr

Go Kart Champion
Location
Ottawa, Canada
Help me decide...

Looking to get RSE10 wheels. I'm stuck on deciding between 18x8 and 18x8.5. I don't plan on pushing HP past 280ish. And looking to run the stock 225s until they wear down, then switching to 235s.

What do you guys think? What would you do? I imagine the performance difference between the two set ups would be unnoticeable (except for asthetics)

2018 GTI Autobahn
 
Hammersticks

Hammersticks

Drag Racing Champion
Location
Bay Area, CA
Car(s)
'16 GTI, '18 e-Golf
Why go 8? Just to fit the stock 225’s? Resist the urge!

Here is 8.5 with 235 conti dw. I’m sure someone else will chime in but I wouldn’t go 225 on an 8.5.



Sent from my iPhone using Tapatalk
 
CDM MK7

CDM MK7

Ready to race!
Location
Canada
Personally, I'd go with the 8" if you don't plan on going past a 235 width tire. You can safely go up to a 245 on an 8", and still be good on your 225's for now. In the end it doesn't really matter all that much, but if we're nitpicking ... the 8" wheel (if we're considering the same design) will be lighter. Not that you'd ever feel that difference, though.

As far as aesthetics, that's a personal call. However, you can always mess around with spacers if you're after a specific look.
 
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Unreal1

Autocross Champion
Location
Pittsburgh
Completely depends on the specific tire, ignore the generic tire width numbers, 225/235 doesn't really matter, what matters is the actual tread width.

You want your tread width to be the same width as your wheel or slightly smaller.

For example, my Falken's are 225/40 18, but have a tread width of 8.3" which is too large to be considered ideal for a 7.5" wheel. It would even be too large for an 8" wheel. An 8.5" wheel would provide ideal performance handling for a tire of that size, even though it's only 225.

In comparison, the all-season G-Force's I just bought are the same 225/40 18 measurements but have a much smaller tread width of 7.6". An 8.5" wheel would fit the Falken's but would be way too large for the same 225 G-Force.

Find the exact tires you want to run first and then find a wheel to match its tread width.
 
THEREALVRT

THEREALVRT

Drag Racing Champion
Location
The great white north
Car(s)
Golf R
Unreal1 said:
Completely depends on the specific tire, ignore the generic tire width numbers, 225/235 doesn't really matter, what matters is the actual tread width.

You want your tread width to be the same width as your wheel or slightly smaller.

For example, my Falken's are 225/40 18, but have a tread width of 8.3" which is too large to be considered ideal for a 7.5" wheel. It would even be too large for an 8" wheel. An 8.5" wheel would provide ideal performance handling for a tire of that size, even though it's only 225.

In comparison, the all-season G-Force's I just bought are the same 225/40 18 measurements but have a much smaller tread width of 7.6". An 8.5" wheel would fit the Falken's but would be way too large for the same 225 G-Force.

Find the exact tires you want to run first and then find a wheel to match its tread width.
Click to expand...
you do realize those measurements are done with a certain width rim. if you change the width of the rim you will get a different measurement. a narrower rim will give a narrower footprint
 
flipflp

flipflp

Autocross Newbie
Location
PNW
Car(s)
'16 Golf R DSG
THEREALVRT said:
you do realize those measurements are done with a certain width rim. if you change the width of the rim you will get a different measurement. a narrower rim will give a narrower footprint
Click to expand...

You are referring to section width, which changes with wheel width.

Unreal1 is taking about tread width, which is a function of tire design and less about the width of the wheel it's mounted on.

Both are important for fitment, just not really in this case since the fitment isn't very aggressive. You're probably buying a tire for your needs (commute, mileage, weather) versus something that is going to rub a fender/strut, etc.

That said go 18x8.5. No question. The only reason that 18x8 exists is for SCCA/AutoX rules that only allows a wheel 1/2" wider than stock be used IIRC. A wider wheel is always better IMO, unless it adds significant weight, which in this case it would not.
 
C

cbr600rr

Go Kart Champion
Location
Ottawa, Canada
Here is another odd question:

What if I got 18x8 et40 on the fronts and 18x8 et30 on the rear? I'd like to keep the stock 225 tires but move to 235 summers later. I think this would be fairly evenly flush on both front and back. No need for any rear spacers?
 
flipflp

flipflp

Autocross Newbie
Location
PNW
Car(s)
'16 Golf R DSG
cbr600rr said:
Here is another odd question:

What if I got 18x8 et40 on the fronts and 18x8 et30 on the rear? I'd like to keep the stock 225 tires but move to 235 summers later.
Click to expand...

Complicates everything. No more tire rotation. If you want different offsets do it with spacers, not the wheels.
 
demi9od

demi9od

Drag Race Newbie
Location
NC
255/35/18 on 8.5" rims with a 3-5mm spacer in the rear. Most rubber you can put in the wheel well.
 
flipflp

flipflp

Autocross Newbie
Location
PNW
Car(s)
'16 Golf R DSG
demi9od said:
255/35/18 on 8.5" rims with a 3-5mm spacer in the rear. Most rubber you can put in the wheel well.
Click to expand...

Sort of an absolute statement there, and not to reignite the section/tread width discussion but you'd be surprised at how easily an even wider wheel and a 265/35-18 would fit as well, depending on the tire brand, how low you are, how much camber you're running, etc. Too many variables to speak in absolutes with wheel and tire fitments, until you're actually test fitting a setup on the car.

Not relevant to OPs question though, since he was only asking about 235/40-18, max.
 
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