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YOUR RESEARCH996.1 and impact on handling 7.5ET50 vs 8.0ET50 vs 8.0ET52
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Use car
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I use the car for "Sunday drives", 5 track days a year and 8 autocross sessions per year.
996.1 and impact on handling 7.5ET50 vs 8.0ET50 vs 8.0ET52
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Suggestion
The wheel is no longer where the car thinks it is, so you need to adjust the geo to suit.
996.1 and impact on handling 7.5ET50 vs 8.0ET50 vs 8.0ET52
Replace 2mm or the width half an inch wider
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Suggestion
Far from an expert but I bet you wouldn't notice any difference with the ET changing 2mm or the width half an inch wider with the same tyres.
996.1 and impact on handling 7.5ET50 vs 8.0ET50 vs 8.0ET52
Replace centre line of your front wheels will
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Suggestion
Changing the centre line of your front wheels will change the scrub radius of the tyre.
996.1 and impact on handling 7.5ET50 vs 8.0ET50 vs 8.0ET52
Replace due
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Suggestion · Original poster
Would the geometry alignment need to be changed due to the wheels being in slightly different places in the front?
996.1 and impact on handling 7.5ET50 vs 8.0ET50 vs 8.0ET52
Replace may be impossible
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Suggestion
In practice geo is a compromise and small changes may be impossible to detect or they may even have advantages in certain situations (road holding over bump steer for example).
996.1 and impact on handling 7.5ET50 vs 8.0ET50 vs 8.0ET52
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Hi all,
I have looked through all the threads, and have been unable to find anything detailing what happens to the handling when you change the front offset.
I have a '99 996 C2, and would like to move to 18" wheels so I can run PS4S tyres, or possibly AD09s at some stage. I am currently on the standard 17" wheels with PS2 tyres.
The 996.1 had options for 18" wheels and tyres, and these were:
* Front 18x7.5J ET50 - 225/40R18
* Rear: 18x10.0J ET65 - 265/35R18
I am having troubles sourcing Porsche 18x7.5s in Australia, and wanted to understand what would happen if I moved the front wheels to either
* 18x8.0J ET50
* 18x8.0J ET52
Running the same 225/265 tyres, how different would the handling be? Would the geometry alignment need to be changed due to the wheels being in slightly different places in the front? Is ET50 or ET52 "better"?
I use the car for "Sunday drives", 5 track days a year and 8 autocross sessions per year.
Grateful for any pointers!
Thanks, Andrew
Far from an expert but I bet you wouldn't notice any difference with the ET changing 2mm or the width half an inch wider with the same tyres.
The biggest change will be going from 17" to 18" wheels.
My C2 has 8J ET50 and it felt fine before I added 15mm wheel spacers when I also lowered my car.
Also far from an expert but here goes.
If you keep the offset the same you're not changing the geo at all. The distance from the hub face to the centre line of the wheel stays the same, so the wheel will still be where the car thinks it is.
If you keep the tyre width the same then even the contact patch remains the same (ish - different tyre/pressure will change it a little I guess).
That said, moving up to 18s with a lower profile and presumably stiffer sidewall will change how the car behaves, feels and performs (whether or not you can sense it).
If you change the offset then you mess things up. The wheel is no longer where the car thinks it is, so you need to adjust the geo to suit. The biggest impact is likely to be on the steering because the front wheel won't be turning (in the steering sense) around its centre line, or wherever the geo intends it to. If you move the wheel in board (increase offset) you effectively shorten the suspension control arms.
In practice geo is a compromise and small changes may be impossible to detect or they may even have advantages in certain situations (road holding over bump steer for example). The numbers you're talking about look pretty sensible and are unlikely to result in much change IMHO.
Thanks for the comments so far!
What is really strange is that Porsche always seemed to have 18x8.0J ET52 (993.362.136.00) available when then were working on the 996.1, yet they decided to to go with the narrower wheel.
From what I have read is that the wider front rim reduces understeer, so that could possibly be better. Maybe that change is just enough to make the car handle less predictably. I still wonder why Porsche then specified the 7.5J on the 996.1s and 8.0J on the 996.2s, and then the move on the rears to 285/30...
Ideally I'd love to have the skill, time money to buy all the various combinations and try them out. Maybe I need to find a youtube blogger who does! :-D
These minor changes will be neglible in terms of feel. I've been through more sets of wheels than most with varying widths and offsets and to be honest noticed not a huge amount of change in the way the car handles.
The biggest difference is tyres. Get them right I'd say.
Changing the centre line of your front wheels will change the scrub radius of the tyre. Have a read up on it as it's interesting stuff. Lots of different setup's to be had, each a compromise of sorts. The 996 came with many different wheel setups from the factory - nothing extreme - they all 'work'. I went through a lot of research when I had some custom wheels made.
Here is one of many resources for a brief summary :
https://en.wikipedia.org/wiki/Scrub_radius
If you want to go down this rabbit hole, this is my complete geekfest of researching wheels :
https://www.youtube.com/watch?v=iyZIx9Z2r-I
This is a source reference. Confirm exact model applicability in the original material.
