Why are so many people 'upgrading' from 19x9 to 19x8.5?
10-13-2008, 03:55 AM
#1
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Why are so many people 'upgrading' from 19x9 to 19x8.5?
Stock rims are 19x9 ET29, yet I see many people upgrading to other models that are 19x8.5, and have not been able to understand how there can be a performance improvement.
When I had my track Evo, going from 17x8 (Toyo R888s in 235/45/17) to 17x8.5 (same tires) resulted in improved braking and superior cornering traction all around (backed up by Performance Box data logs).
When I upgraded from 17x8.5 (235/45/17) to 18x9 (255/40/18), again, there was an improvement in braking and traction, again, backed up with empirical evidence from data logs.
Yet, I notice many people who switch from 19x9 (OEM) to 19x8.5, and wonder if, aside from being cheaper in many cases, there are actual performance improvements over downsizing the rim from 9 to 8.5 while keeping the same tires.
When I had my track Evo, going from 17x8 (Toyo R888s in 235/45/17) to 17x8.5 (same tires) resulted in improved braking and superior cornering traction all around (backed up by Performance Box data logs).
When I upgraded from 17x8.5 (235/45/17) to 18x9 (255/40/18), again, there was an improvement in braking and traction, again, backed up with empirical evidence from data logs.
Yet, I notice many people who switch from 19x9 (OEM) to 19x8.5, and wonder if, aside from being cheaper in many cases, there are actual performance improvements over downsizing the rim from 9 to 8.5 while keeping the same tires.
10-13-2008, 04:13 AM
#2
It's all about availability. Not much out there in 19x9......
and unless you want to go with 275 tires, 19x9.5 will be too wide and/or my not be available in the correct offset to fit under the front fenders properly.
10-13-2008, 08:02 AM
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my 19x8.5's use the OEM size tires, and are about 6 lbs lighter per wheel.
besides also being stronger (forged vs cast). my goals for replacing the wheels were 1) lightness, and 2) strength. Secondary concerns were style, size, and value.
10-13-2008, 09:43 AM
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But wouldn't dropping 0.5" per side, reduce contact patch?
Like I said, going up 0.5" per rim and keeping the same sized tires on my Evo actually saw handling and braking improvements.
Is the size drop really worth it in terms of reduction in traction?
Pros of going 8.5"
1. more rim variety
2. lighter by up to 6 lbs per rim
3. cheaper (compared to 9")
Cons
1. reduced traction
Unknown:
1. Stronger? Is 8.5" really stronger than 9"
2. Price difference between 8.5" and 9" is enough to upgrade from cast to forged?
Is the size drop really worth it in terms of reduction in traction?
Pros of going 8.5"
1. more rim variety
2. lighter by up to 6 lbs per rim
3. cheaper (compared to 9")
Cons
1. reduced traction
Unknown:
1. Stronger? Is 8.5" really stronger than 9"
2. Price difference between 8.5" and 9" is enough to upgrade from cast to forged?
10-13-2008, 09:57 AM
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for tires under 50-series sidewall, the recommended wheel width is 85% of the tread section....
....a 255 tire has a section width of just over 10". So 85% of 10" means a 8.5" wide wheel is sufficient. The range of acceptable wheel widths for that tire size is 8.5" - 10"
(Reference: Yokohama)
(Reference: Yokohama)
10-13-2008, 12:07 PM
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I'm not talking about fitment, I'm talking about contact patch and grip :)
Thanks, Bob 
I do know and respect what you mean, but like I've said, there is a noticeable degradation in cornering grip, and I'm wondering if those of you who drive the car hard (in corners) notice this when going from stock 19" to aftermarket 8.5" wheels and running the same sized rubbers
All I'm saying is that I noticed this when I tracked my Evo (which did have Zeal racing coilovers), and I wonder if the difference is as noticeable on the RS4.
I do know and respect what you mean, but like I've said, there is a noticeable degradation in cornering grip, and I'm wondering if those of you who drive the car hard (in corners) notice this when going from stock 19" to aftermarket 8.5" wheels and running the same sized rubbers
All I'm saying is that I noticed this when I tracked my Evo (which did have Zeal racing coilovers), and I wonder if the difference is as noticeable on the RS4.
