991.2 Rear Wheel Width
#1
02-27-2017, 06:28 AM
Join Date: Nov 2012
Location: Southlake, TX
Posts: 6
Rep Power: 0 
991.2 Rear Wheel Width
I purchased a set to OZ Leggera HLT in 19x8.5 ET53 and 19x12 ET51 with 245 and 305 PSS. Installed them and now I see that the rear tire is really stretched out on the 12" rim. I plan to order a custom set in the near future (i.e. HRE, CCW, etc) in the factory width 8.5/11.5 but with offsets that are a bit more flush. I will then use the OZ wheel for the track.
In order to remedy the 305 stretched tire on the rear 12" wheel, I have two options and I would really love to hear from track guys which way to go on the rear wheel.
Option 1) Exchange the rear 19x12 for a 19x11 ET50 and use the 305 tire. My worry here is that the 991.2 now has 11.5 rear and I'm not sure I should downsize the width.
Option 2) Keep the 19x12 wheel and exchange the 305 tire for the same PSS in a 345/30. Same O/D.
Either solution is temporary till my custom set is delivered. Question is which rear width is better for the track and provides me more options with tires.
Thanks for reading.
In order to remedy the 305 stretched tire on the rear 12" wheel, I have two options and I would really love to hear from track guys which way to go on the rear wheel.
Option 1) Exchange the rear 19x12 for a 19x11 ET50 and use the 305 tire. My worry here is that the 991.2 now has 11.5 rear and I'm not sure I should downsize the width.
Option 2) Keep the 19x12 wheel and exchange the 305 tire for the same PSS in a 345/30. Same O/D.
Either solution is temporary till my custom set is delivered. Question is which rear width is better for the track and provides me more options with tires.
Thanks for reading.
#2
02-27-2017, 08:23 AM
Why don't you use stock specification wheels and tires and then add spacers to change the offset?
I know I'm in the minority, but I have some faith that Porsche knew what it was doing when it designed the new suspension on the 991.2 (and the earlier models, for that matter) and selected tire sizes.
In fact, all of the Porsche models with 20" wheels use the same tire widths (245/35-20F, 305/30-20R. The rear tracks vary a bit depending on RWD/AWD, but most are 1,558 rear track. the exception is the Turbo/S at 1,590, although its front track remains the same.
So, what I get from that is Porsche feels the car has enough rubber and track on a GTS car with 450HP and widens the rear track on a car that gets to 580HP. I haven't considered the GT3's etc.
I think the standard wheel sizes will give you more tire options and more appropriate tire sizes. "Stretching" a tire to fit a rim should never have happened because the specifications of the tire would have said otherwise.
I'd hate to be driving my car "to the limit" with a stretched tire setup like yours only to suffer a tire failure from stretching it beyond its specification. That could result in an accident whereas the stock factory wheel/tire setup might just have you sliding a bit before PTM kicked in to help out.
Just my $0.02 worth.
I know I'm in the minority, but I have some faith that Porsche knew what it was doing when it designed the new suspension on the 991.2 (and the earlier models, for that matter) and selected tire sizes.
In fact, all of the Porsche models with 20" wheels use the same tire widths (245/35-20F, 305/30-20R. The rear tracks vary a bit depending on RWD/AWD, but most are 1,558 rear track. the exception is the Turbo/S at 1,590, although its front track remains the same.
So, what I get from that is Porsche feels the car has enough rubber and track on a GTS car with 450HP and widens the rear track on a car that gets to 580HP. I haven't considered the GT3's etc.
I think the standard wheel sizes will give you more tire options and more appropriate tire sizes. "Stretching" a tire to fit a rim should never have happened because the specifications of the tire would have said otherwise.
I'd hate to be driving my car "to the limit" with a stretched tire setup like yours only to suffer a tire failure from stretching it beyond its specification. That could result in an accident whereas the stock factory wheel/tire setup might just have you sliding a bit before PTM kicked in to help out.
Just my $0.02 worth.
#3
02-27-2017, 08:55 AM
Why don't you use stock specification wheels and tires and then add spacers to change the offset?
I know I'm in the minority, but I have some faith that Porsche knew what it was doing when it designed the new suspension on the 991.2 (and the earlier models, for that matter) and selected tire sizes.
In fact, all of the Porsche models with 20" wheels use the same tire widths (245/35-20F, 305/30-20R. The rear tracks vary a bit depending on RWD/AWD, but most are 1,558 rear track. the exception is the Turbo/S at 1,590, although its front track remains the same.
So, what I get from that is Porsche feels the car has enough rubber and track on a GTS car with 450HP and widens the rear track on a car that gets to 580HP. I haven't considered the GT3's etc.
I think the standard wheel sizes will give you more tire options and more appropriate tire sizes. "Stretching" a tire to fit a rim should never have happened because the specifications of the tire would have said otherwise.
I'd hate to be driving my car "to the limit" with a stretched tire setup like yours only to suffer a tire failure from stretching it beyond its specification. That could result in an accident whereas the stock factory wheel/tire setup might just have you sliding a bit before PTM kicked in to help out.
Just my $0.02 worth.
I know I'm in the minority, but I have some faith that Porsche knew what it was doing when it designed the new suspension on the 991.2 (and the earlier models, for that matter) and selected tire sizes.
In fact, all of the Porsche models with 20" wheels use the same tire widths (245/35-20F, 305/30-20R. The rear tracks vary a bit depending on RWD/AWD, but most are 1,558 rear track. the exception is the Turbo/S at 1,590, although its front track remains the same.
So, what I get from that is Porsche feels the car has enough rubber and track on a GTS car with 450HP and widens the rear track on a car that gets to 580HP. I haven't considered the GT3's etc.
I think the standard wheel sizes will give you more tire options and more appropriate tire sizes. "Stretching" a tire to fit a rim should never have happened because the specifications of the tire would have said otherwise.
I'd hate to be driving my car "to the limit" with a stretched tire setup like yours only to suffer a tire failure from stretching it beyond its specification. That could result in an accident whereas the stock factory wheel/tire setup might just have you sliding a bit before PTM kicked in to help out.
Just my $0.02 worth.
#4
02-27-2017, 09:07 AM
Join Date: Nov 2012
Location: Southlake, TX
Posts: 6
Rep Power: 0 Why don't you use stock specification wheels and tires and then add spacers to change the offset?
I know I'm in the minority, but I have some faith that Porsche knew what it was doing when it designed the new suspension on the 991.2 (and the earlier models, for that matter) and selected tire sizes.
In fact, all of the Porsche models with 20" wheels use the same tire widths (245/35-20F, 305/30-20R. The rear tracks vary a bit depending on RWD/AWD, but most are 1,558 rear track. the exception is the Turbo/S at 1,590, although its front track remains the same.
So, what I get from that is Porsche feels the car has enough rubber and track on a GTS car with 450HP and widens the rear track on a car that gets to 580HP. I haven't considered the GT3's etc.
I think the standard wheel sizes will give you more tire options and more appropriate tire sizes. "Stretching" a tire to fit a rim should never have happened because the specifications of the tire would have said otherwise.
I'd hate to be driving my car "to the limit" with a stretched tire setup like yours only to suffer a tire failure from stretching it beyond its specification. That could result in an accident whereas the stock factory wheel/tire setup might just have you sliding a bit before PTM kicked in to help out.
Just my $0.02 worth.
I know I'm in the minority, but I have some faith that Porsche knew what it was doing when it designed the new suspension on the 991.2 (and the earlier models, for that matter) and selected tire sizes.
In fact, all of the Porsche models with 20" wheels use the same tire widths (245/35-20F, 305/30-20R. The rear tracks vary a bit depending on RWD/AWD, but most are 1,558 rear track. the exception is the Turbo/S at 1,590, although its front track remains the same.
So, what I get from that is Porsche feels the car has enough rubber and track on a GTS car with 450HP and widens the rear track on a car that gets to 580HP. I haven't considered the GT3's etc.
I think the standard wheel sizes will give you more tire options and more appropriate tire sizes. "Stretching" a tire to fit a rim should never have happened because the specifications of the tire would have said otherwise.
I'd hate to be driving my car "to the limit" with a stretched tire setup like yours only to suffer a tire failure from stretching it beyond its specification. That could result in an accident whereas the stock factory wheel/tire setup might just have you sliding a bit before PTM kicked in to help out.
Just my $0.02 worth.
Thank you for your feedback. I'm in the same boat with you that Porsche knows what's it's doing and that's why I don't want to mess with it too much. The custom set I'd order would have 44 front and 51 rear offset, which is the same as the stock offset plus 5mm spacers (which Porsche offers OE anyway).
The issue I'm having is choosing between an 11 or a 12 width for the rear for the track. I'm not using the stock + spacers because I want a dedicated track wheel anyway. The OZ wheels that I purchased are ultimately destined for my track wheels, but I'm running them now till my custom wheels are done. Then I'll mount the OZ with dedicated track tires. These wheels have a 30-day return policy, so I'm trying to resolve it now and figure out if I should swap the 12 for an 11 or keep the 12. The stock is 11.5 so you can see why I'm asking. I have read that for track use, you should always go with the widest in the recommended range for a given tire. The Michelin PSS 305/35-19 has a rim range from 10" to 12" so it's not outside the range but just at the top end of the range.
Last edited by amr; 02-27-2017 at 09:10 AM.
#5
02-27-2017, 09:14 AM
Thank you for your feedback. I'm in the same boat with you that Porsche knows what's it's doing and that's why I don't want to mess with it too much. The custom set I'd order would have 44 front and 51 rear offset, which is the same as the stock offset plus 5mm spacers (which Porsche offers OE anyway).
The issue I'm having is choosing between an 11 or a 12 width for the rear for the track. I'm not using the stock + spacers because I want a dedicated track wheel anyway. The OZ wheels that I purchased are ultimately destined for my track wheels, but I'm running them now till my custom wheels are done. Then I'll mount the OZ with dedicated track tires. These wheels have a 30-day return policy, so I'm trying to resolve it now and figure out if I should swap the 12 for an 11 or keep the 12. The stock is 11.5 so you can see why I'm asking. I have read that for track use, you should always go with the widest in the recommended range for a given tire. The Michelin PSS 305/35-19 has a rim range from 10" to 12" so it's not outside the range but just at the top end of the range.
The issue I'm having is choosing between an 11 or a 12 width for the rear for the track. I'm not using the stock + spacers because I want a dedicated track wheel anyway. The OZ wheels that I purchased are ultimately destined for my track wheels, but I'm running them now till my custom wheels are done. Then I'll mount the OZ with dedicated track tires. These wheels have a 30-day return policy, so I'm trying to resolve it now and figure out if I should swap the 12 for an 11 or keep the 12. The stock is 11.5 so you can see why I'm asking. I have read that for track use, you should always go with the widest in the recommended range for a given tire. The Michelin PSS 305/35-19 has a rim range from 10" to 12" so it's not outside the range but just at the top end of the range.
Personally, as I wrote above, I'd just pick a wheel that is 11.5" and be done with it.
#6
02-27-2017, 06:05 PM
What "proper width" rim are you referring to? 11.5"? You have to check several things: firstly with the tire manufacturer, to see if the 11.5" is suitable for their size and secondly whether the overall diameter is correct for the car. I'm not sure if this is relevant to you but there must be some need to keep the diameter the same on all 4 tires with the AWD models.