Yet another Wheel Offset Question
02-05-2015, 04:08 PM
#16
With the 928, there are handling consequences if wheel offsets are not within published guidelines. There are those who disagree, but if you look at an engineering diagram, the scrub radius is definitely affected.
The 968 seems to be more forgiving based on the PET catalog I linked, but I'd be curious to see what the geometry looks like using different offsets.
Hugo'
The 968 seems to be more forgiving based on the PET catalog I linked, but I'd be curious to see what the geometry looks like using different offsets.
Hugo'
02-05-2015, 09:33 PM
#18
Drifting
My 968 manual has 7jx16 with 57.96 in. offset and 8jx16 with 57.09 offset.
For the larger wheel it has 7.5jx17 57.40 in and 9jx17 56.92.
Now 5.7 inches makes sense, not 57...
Kevin Gross has this too which seems to conflict with my manual.
http://www.connact.com/~kgross/FAQ/944faq13.html
For the larger wheel it has 7.5jx17 57.40 in and 9jx17 56.92.
Now 5.7 inches makes sense, not 57...
Kevin Gross has this too which seems to conflict with my manual.
http://www.connact.com/~kgross/FAQ/944faq13.html
02-05-2015, 09:49 PM
#19
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My 968 manual has 7jx16 with 57.96 in. offset and 8jx16 with 57.09 offset.
For the larger wheel it has 7.5jx17 57.40 in and 9jx17 56.92.
Now 5.7 inches makes sense, not 57...
Kevin Gross has this too which seems to conflict with my manual.
http://www.connact.com/~kgross/FAQ/944faq13.html
For the larger wheel it has 7.5jx17 57.40 in and 9jx17 56.92.
Now 5.7 inches makes sense, not 57...
Kevin Gross has this too which seems to conflict with my manual.
http://www.connact.com/~kgross/FAQ/944faq13.html
Looking at the chart for the wheels and tire, not sure I understand the term 'backspacing'.
02-06-2015, 05:10 AM
#20
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From 93/94 on the 968 CS and S had the Carrera Cup 2's as standard fitment (17" of 7.5j and 9j) the offsets being 65 and 55 respectively.
What I find amazing is that without a change in rear quarter or fender lines the Turbo RS monster managed to fit in 18" 10 and 11j's with 305 tyres on the rear! Surely the drive and wheel shafts, trailing arms etc would have been altered/shortened to accommodate all this crazy goings on(?)
What I find amazing is that without a change in rear quarter or fender lines the Turbo RS monster managed to fit in 18" 10 and 11j's with 305 tyres on the rear! Surely the drive and wheel shafts, trailing arms etc would have been altered/shortened to accommodate all this crazy goings on(?)
02-06-2015, 11:03 AM
#21
From 93/94 on the 968 CS and S had the Carrera Cup 2's as standard fitment (17" of 7.5j and 9j) the offsets being 65 and 55 respectively.
What I find amazing is that without a change in rear quarter or fender lines the Turbo RS monster managed to fit in 18" 10 and 11j's with 305 tyres on the rear! Surely the drive and wheel shafts, trailing arms etc would have been altered/shortened to accommodate all this crazy goings on(?)
What I find amazing is that without a change in rear quarter or fender lines the Turbo RS monster managed to fit in 18" 10 and 11j's with 305 tyres on the rear! Surely the drive and wheel shafts, trailing arms etc would have been altered/shortened to accommodate all this crazy goings on(?)
-V
02-06-2015, 04:32 PM
#23
Okay, so I gave it a shot and test fit 18s on my 968 today. Up front were 235/40 on 8J with 50ET. Out back were 285/30 on 10J 65ET.
The rear combo looks like it'll be fine. The front combo is just too much shoulder. I'm going to try some 225/40s on the same wheel up front and see how that goes.
The wheels are OEM lightweight 5-spoke "MY02" Carrera style. Looked pretty good... if you don't mind the shine. (It's for the wife, cut me a little slack...)
-V
The rear combo looks like it'll be fine. The front combo is just too much shoulder. I'm going to try some 225/40s on the same wheel up front and see how that goes.
The wheels are OEM lightweight 5-spoke "MY02" Carrera style. Looked pretty good... if you don't mind the shine. (It's for the wife, cut me a little slack...)
-V
02-06-2015, 06:55 PM
#25
02-07-2015, 11:59 AM
#26
I just rechecked the rear clearances. Without measuring exactly, I can say that there is a ton of clearance with that setup. Again, the only modification would need to be securing the e-brake cables a little bit over towards the inside.
-V
-V
02-07-2015, 04:27 PM
#27
Drifting
Okay, so I gave it a shot and test fit 18s on my 968 today. Up front were 235/40 on 8J with 50ET. Out back were 285/30 on 10J 65ET.
The rear combo looks like it'll be fine. The front combo is just too much shoulder. I'm going to try some 225/40s on the same wheel up front and see how that goes.
-V
The rear combo looks like it'll be fine. The front combo is just too much shoulder. I'm going to try some 225/40s on the same wheel up front and see how that goes.
-V
02-07-2015, 06:07 PM
#28
Looking at the section width in mm for easier comparison, that's 255 (yours), and 235 (mine).
On your ET55 wheel (wheel width won't matter here, tire width will), 182.5mm of your 255mm tire will be "inside" the mounting plane, and 72.5mm outside of it. On my 235mm tire, 175.5 will be inside, and 67.5 outside. So even though your wheel's offset is +5 over mine, your tire will stick out 5mm further in the fender.
The radius on your wheel/tire combo is 317.9, a trivial 4.7mm shorter than the setup I tested.
So your setup is wider and (virtually) the same radius, and yet you have issues at all? No rubbing the outside front corners of the fender well, lock to lock? That's really interesting, and will make me take a second look at the fitment I tried yesterday. I didn't have it all the way on the ground, so I was seeing the wheels at the bottom of the suspension arc. If that were to occur in a driving situation then I guess I'd be airborne and have bigger things to worry about, especially if the wheels were turned.
SM, or anyone else who's done that setup, please let me know ASAP? Will save me a lot of hassle if I could know one way or the other by Monday.
But, question for the room: in hard cornering, hard enough to lift the inside front wheel, does that wheel ever reach the lowest point in the arc, or is it kept above that by tension in the sway from the outside wheel?
-V
02-07-2015, 09:15 PM
#29
Drifting
255/40 R17 is 10.04 inches wide, with a radius of 12.52. Compared to the 235/40 R18 setup I tried, which is 9.25 inches wide, with a radius of 12.70.
Looking at the section width in mm for easier comparison, that's 255 (yours), and 235 (mine).
On your ET55 wheel (wheel width won't matter here, tire width will), 182.5mm of your 255mm tire will be "inside" the mounting plane, and 72.5mm outside of it. On my 235mm tire, 175.5 will be inside, and 67.5 outside. So even though your wheel's offset is +5 over mine, your tire will stick out 5mm further in the fender.
The radius on your wheel/tire combo is 317.9, a trivial 4.7mm shorter than the setup I tested.
So your setup is wider and (virtually) the same radius, and yet you have issues at all? No rubbing the outside front corners of the fender well, lock to lock? That's really interesting, and will make me take a second look at the fitment I tried yesterday. I didn't have it all the way on the ground, so I was seeing the wheels at the bottom of the suspension arc. If that were to occur in a driving situation then I guess I'd be airborne and have bigger things to worry about, especially if the wheels were turned.
SM, or anyone else who's done that setup, please let me know ASAP? Will save me a lot of hassle if I could know one way or the other by Monday.
But, question for the room: in hard cornering, hard enough to lift the inside front wheel, does that wheel ever reach the lowest point in the arc, or is it kept above that by tension in the sway from the outside wheel?
-V
Looking at the section width in mm for easier comparison, that's 255 (yours), and 235 (mine).
On your ET55 wheel (wheel width won't matter here, tire width will), 182.5mm of your 255mm tire will be "inside" the mounting plane, and 72.5mm outside of it. On my 235mm tire, 175.5 will be inside, and 67.5 outside. So even though your wheel's offset is +5 over mine, your tire will stick out 5mm further in the fender.
The radius on your wheel/tire combo is 317.9, a trivial 4.7mm shorter than the setup I tested.
So your setup is wider and (virtually) the same radius, and yet you have issues at all? No rubbing the outside front corners of the fender well, lock to lock? That's really interesting, and will make me take a second look at the fitment I tried yesterday. I didn't have it all the way on the ground, so I was seeing the wheels at the bottom of the suspension arc. If that were to occur in a driving situation then I guess I'd be airborne and have bigger things to worry about, especially if the wheels were turned.
SM, or anyone else who's done that setup, please let me know ASAP? Will save me a lot of hassle if I could know one way or the other by Monday.
But, question for the room: in hard cornering, hard enough to lift the inside front wheel, does that wheel ever reach the lowest point in the arc, or is it kept above that by tension in the sway from the outside wheel?
-V
02-07-2015, 09:25 PM
#30
Correct no issues with rubbing whatsoever. This is with Bridgestone re-11a tires that are quite meaty (check tirerack for the specs). I've never been airborne so can't comment on that 😃. I think you are correct about needing to let the suspension settle to see how the wheels will fit because your picture shows the front having positive camber right now.
-V