ProDarwin said:
Pete. (l33t FS) said:
z31maniac said:
obsolete said:
In reply to ProDarwin :
Tramlining can get annoying.
Tramlining with 225s?
I have had it with 195s. Sidewall height plays a huge factor, as does suspension geometry.
In my experience the #1 factor is geometry.
How does the offset on these new wheels compare with stock? Is the scrub radius close?
To exaggerate: 225s on a 9" wheel at factory offset will likely drive a whole lot better than 205s on an 8" wheel with an extra inch of offset.
For reference from this blind man checking out an elephant, 205/60-13s drive great, 195/50-15s on similar offset wheels (15x6) were laborious to keep the car going straight. 225/50-15 on zero offset 15x7 wheels drove a lot better.
Yeah, the wider 15 inch tires drove better. That is still weird to think about. Gotta be something else happening.
Pete. (l33t FS) said:
Yeah, the wider 15 inch tires drove better. That is still weird to think about. Gotta be something else happening.
With negative camber, a wider tire reduces the scrub radius as the centroid of the contact patch moves inboard. The contact patch is not left/right symmetric as the camber loads one side more than the other.
If you move on from the 8's I'll trade you something for them back
In reply to GameboyRMH :
Oh if it's 9s all around it will be no less than 225/45s
matthewmcl said:
Pete. (l33t FS) said:
Yeah, the wider 15 inch tires drove better. That is still weird to think about. Gotta be something else happening.
With negative camber, a wider tire reduces the scrub radius as the centroid of the contact patch moves inboard. The contact patch is not left/right symmetric as the camber loads one side more than the other.
RX-7s had zero camber, plus or minus a tad.
I hate metric offset numbers.
Tire Rack: WHAT IS WHEEL OFFSET?
(online) Offset Visualizer/Converter
So, your current 8" wide wheels with a 3" backspacing have -38mm negative offset. The backspacing includes the 1/2" extra for the wheel lip which makes your wheel really 9" wide.
Your new 8" wheels with 0mm offset has a backspacing of 4.5"
Your new 9" wheels with 0mm offset has a backspacing of 5.0"
Looking up Datsun 240Z 1969 Alloy wheel fitment guide a 69 Datsun 240Z stock wheel size is 5Jx14 ET15. So 5" wide with +15mm positive offset has a backspacing of 3.59". I think. 
You have to calculate from your wheels and tires on your car if anything is going to rub on the inside and/or use wheel spacers if they do. Have a nice day.
offset makes understanding your geometry deviation from stock really easy
with backspace you now need 2 numbers and math to understand the same information
In reply to ProDarwin :
I guess really, I just don't like metric. Luckily, there are online calculators for just about everything which wasn't the case when I was trying to stuff new wheels and tires under my car with no help and no internet. Metric backspacing would be a nice piece of data to include with all wheel data sheets. At least I would only have to convert units once since I don't own a metric tape.
15x9, -10mm, 4x114.3 with 225/45r15s
ProDarwin said:
offset makes understanding your geometry deviation from stock really easy
with backspace you now need 2 numbers and math to understand the same information
As long as outside diameter stays the same, at least, if not then everything gets thrown out the window.
Camber adjustment might change the scrub radius more than wheel offset does, too.
In reply to Pete. (l33t FS) :
Bearing load increases as well
In reply to QuasiMofo (John Brown) :
I wonder about that. I mean, yes, statically they do, but how much of that resolves away under cornering load?
Not that there is anything good to write about having a load change signs all the time.
It's a lever that's ratio is being increased it will increase pressure. Whether it creates a negative effect depends on what the bearing can handle.
Square 9" with far too small 225/45r15s mounted and ready to sit for the winter.
That's a lot of stretch, I'm guessing they're barely any wider than the old 205s...so you'll be going to 245/40R15s then? Let me know if you'll be selling those 225s.
Pete. (l33t FS) said:
ProDarwin said:
Pete. (l33t FS) said:
z31maniac said:
obsolete said:
In reply to ProDarwin :
Tramlining can get annoying.
Tramlining with 225s?
I have had it with 195s. Sidewall height plays a huge factor, as does suspension geometry.
In my experience the #1 factor is geometry.
How does the offset on these new wheels compare with stock? Is the scrub radius close?
To exaggerate: 225s on a 9" wheel at factory offset will likely drive a whole lot better than 205s on an 8" wheel with an extra inch of offset.
For reference from this blind man checking out an elephant, 205/60-13s drive great, 195/50-15s on similar offset wheels (15x6) were laborious to keep the car going straight. 225/50-15 on zero offset 15x7 wheels drove a lot better.
Yeah, the wider 15 inch tires drove better. That is still weird to think about. Gotta be something else happening.
Definitely has to be something else going on. My first gen BRZ was 17x7 ET48 with 215/45, stock. No tramlining lowered with a proper alignment when going to 18x9.5 ET38, 255/35 Direzza Star Specs.
In reply to z31maniac :
BRZ is also a forty years newer suspension design
