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Offset Issue?

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Old 08-12-2018, 03:51 PM
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Offset Issue?

Hello All!

I picked up some new wheels for my 997.1 base Carrera. The wheel specs are 19x8.5 +41 mm offset and 19x11 +50 mm offset. The tires are PS4S 235/35/19 and 295/30/19. I think the fronts stick out a tad more than I like. Would any of you know if this would be an issue with form, fit or function at my stock oem ride height. I'm concerned about any rubbing or interference during hard cornering.

Since the front sticks out from the +41 offset, is it definitely a no go for lowering? If I can lower what is the most I can go?

This vehicle will be used as daily and a few autox a year. I attached some pics for reference.

Thanks in advance!

Regards,
Swiss



 
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Old 08-12-2018, 10:08 PM
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Nice wheels and looks like a perfect lowering project. To me, the offsets don't look bad at all but lowering it will tuck the wheels just a bit further into the well which may make you happier. Will also improve the overall stance imo. I'm a die hard H&R springs fan for lowering which drops it about 1.25". Your base 997 should easily handle that as it sits taller than the S. I've had no problems lowering S cars with H&R's. If you still don't want to go that low go with Techart or Eibach. Either one will drop it about 1" even. Or if you're itching to spend more money, go with some quality brand of coilovers and adjust the drop to your taste.
 
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Old 08-13-2018, 08:22 AM
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I'm not sure who advised you on those offsets for a NB car but they're not a good fit. I've done multiple posts here and on Rennlist regarding NB wheel offsets with photos of different ones and what to avoid for a NB car. On an 8.5" wheel an et50 is perfect (vs your 41) and on the rear, running a 12" wide wheel, 68-74 is perfect.

This is what an 8.5" et 42 looked like on my car and I pulled them off after 1,200 miles. My car is also on coilovers and slightly lowered. The car had high-speed stability issues with these offsets becoming very darty vs the rock-solid feel it had prior. Tire make, model, sizes, and pressures were exactly the same with the wheels that had these offsets and the proper offsets with the only variable being the offsets.





When I had my current custom Forgelines made, I used the offsets I mention above and the car drives perfectly. If you decide to return these wheels I have a similar spoke design to your Forgestars on a set of fully forged, lightweight Champion RS171s that were fully polished then clear powdercoated for sale in the Marketplace, that will look and drive correctly on your car. The Champions look like this.



 
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Old 08-13-2018, 01:41 PM
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+40 offset

Unless you are not going to lower it, +41 will poke out. You will be fine with H&Rs as it drops more than the Eibachs with your offset. I have 9x19 et40 and 11x19 et40 on Eibachs and it pokes out even if I am using thinner tires 235/35 with bit of stretch. I'm doing coil overs this week to make it flush upfront. On stock height, +50 to +53 upfront is the ideal offset and about +50 on rears.








 
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Old 08-14-2018, 05:17 PM
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Thanks everyone for your feedback. It sounds like I shouldn't be worried about rubbing with my current offset configuration and ride height. I am concerned on the changes the offsets make dynamically in the handling department. Since the offsets decreased, the track width on both axles increased.

Carrera NB Front track width = 1486 mm
Carrera NB Rear track width = 1534 mm

My Carrera NB Front track width = 1518 mm
My Carrera NB Rear track width = 1550 mm

I've read on some forums on the correlation of changing track width's to changes in vehicle behavior (understeer/oversteer) but I'm not sure how it applies to my configuration. Would any of you know if there are any negative impacts to increasing the track width's? Petza914 mentioned decrease in high speed stability but i'm not sure how that connects to front track width. Is it because increasing the front track could cause front to "toe out" that can negatively affect highspeed stability? It sounds like the increase in track width's would help in corner stability if done proportionally from front to rear.

If this really is an issue I would want to see if Forgestar would work with me to replace the front wheels with those of a different offset.

Thanks,

Swiss
 
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Old 08-14-2018, 05:52 PM
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Originally Posted by SwissCheese View Post
Thanks everyone for your feedback. It sounds like I shouldn't be worried about rubbing with my current offset configuration and ride height. I am concerned on the changes the offsets make dynamically in the handling department. Since the offsets decreased, the track width on both axles increased.

Carrera NB Front track width = 1486 mm
Carrera NB Rear track width = 1534 mm

My Carrera NB Front track width = 1518 mm
My Carrera NB Rear track width = 1550 mm

I've read on some forums on the correlation of changing track width's to changes in vehicle behavior (understeer/oversteer) but I'm not sure how it applies to my configuration. Would any of you know if there are any negative impacts to increasing the track width's? Petza914 mentioned decrease in high speed stability but i'm not sure how that connects to front track width. Is it because increasing the front track could cause front to "toe out" that can negatively affect highspeed stability? It sounds like the increase in track width's would help in corner stability if done proportionally from front to rear.

If this really is an issue I would want to see if Forgestar would work with me to replace the front wheels with those of a different offset.

Thanks,

Swiss
Think about a 2' rod and a 4' rod. At the center you rotate both of them 20 degrees. Wjlhat linear distance did the end of the 2' rod cover vs the end of 4' rod? The 4' rod moved a lot further. This is the only thing I can think of in my case that would make the handling of the wider front track less stable, though in my case the rear track was widened as well since the rear wheels were a corresponding offset to the fronts.

19x8.5 with 42mm offset
19x11 with 52mm offset

i made no other changes to the car and wasn't expecting any driving dynamic differences so it wasn't I was hyper sensitive to and it just happened and was repeatable. I don't fully understand it because people run spacers on their 997s all the time, which would create a similar setup and they don't seem to mention this. Also, I widened the track on my Cayenne Turbo S 2" and it didn't experience any handling dynamics differences, in fact, its more stable now than it was. Maybe the suspension geometry is significantly different than the 997 since it has an air suspension and that's why.
 
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Old 08-14-2018, 10:30 PM
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This may be too simplistic of a way of looking at this but how can a wider track and if lowering, a lower center of gravity affect handling negatively? Two track oriented 997's (GT3 and GT3 RS) were sold by Porsche and both were lower than the regular Carreras. Also, the GT3 came with spacers from the factory, possibly the RS too but not sure. Could have had a more aggressive factory offset instead. Either way, wider and lower seems to be how Porsche preferred to deliver their track oriented cars from the factory. And given that it doesn't sound like the OP will push this car to its limits, the concerns here may play such a minimal role in real life as to be negligible.
 
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Old 08-15-2018, 12:12 AM
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Lots of good questions and thoughts here and I don't have the answers, only my personal experience with 5 different sets of wheels on two 997.1 C2S cars, and of those 5, the worst driving set were of the widths and offsets mentioned above, and the 2nd worst set were the chromed RUF wheels my car came with that were 10 lbs per wheel heavier than anything else I had on them, and why I sold them. Changing from these to the Champions and upgrading to PCCB brakes resulted in a major reduction in unsprung weight at each corner, and made a huge difference in steering feel and handling. On all of these sets I was running the same make, model, and size of tire.

I don't know if the Porsche GT cars have different steering rack ratios or some other factor that makes them drive better with the wider track and lower stance or why this particular set of wheels made the car handle what I'd consider poorly, but they did. With my Champions and Forgelines, the car drives perfectly straight and handles totally predictably, even up to speeds of 125 MPH or so. With these other wheels, lane changes at 85 or 90 had a completely different sensation and were not confidence inspiring.

 
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Old 08-15-2018, 10:35 AM
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Originally Posted by Petza914 View Post
Lots of good questions and thoughts here and I don't have the answers, only my personal experience with 5 different sets of wheels on two 997.1 C2S cars, and of those 5, the worst driving set were of the widths and offsets mentioned above, and the 2nd worst set were the chromed RUF wheels my car came with that were 10 lbs per wheel heavier than anything else I had on them, and why I sold them. Changing from these to the Champions and upgrading to PCCB brakes resulted in a major reduction in unsprung weight at each corner, and made a huge difference in steering feel and handling. On all of these sets I was running the same make, model, and size of tire.

I don't know if the Porsche GT cars have different steering rack ratios or some other factor that makes them drive better with the wider track and lower stance or why this particular set of wheels made the car handle what I'd consider poorly, but they did. With my Champions and Forgelines, the car drives perfectly straight and handles totally predictably, even up to speeds of 125 MPH or so. With these other wheels, lane changes at 85 or 90 had a completely different sensation and were not confidence inspiring.
OT - what RUF wheels did you have before and what offsets? I was looking for 19 RUFs for the 997 but seldom it comes by even replicas.
 
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Old 08-15-2018, 10:46 AM
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Originally Posted by jq911 View Post
OT - what RUF wheels did you have before and what offsets? I was looking for 19 RUFs for the 997 but seldom it comes by even replicas.
RUF Rear Wheels with 7mm Spacer - 11" x 19" with 70mm Offset
RUF Front Wheels - 8.5" x 19" with 58mm Offset



 

Last edited by Petza914; 08-15-2018 at 11:09 AM.
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Old 08-15-2018, 11:55 AM
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Originally Posted by Petza914 View Post
RUF Rear Wheels with 7mm Spacer - 11" x 19" with 70mm Offset
RUF Front Wheels - 8.5" x 19" with 58mm Offset


Just curious how much did it go for? Hard to come by as I've been looking for sometime now
 
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Old 08-15-2018, 12:08 PM
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Originally Posted by jq911 View Post
Just curious how much did it go for? Hard to come by as I've been looking for sometime now
I think about $5,000 but it was 5 or 6 years ago. They show up in the marketplace here and on rennlist a few times/year and you didn't want these chrome ones - they were ridiculously heavy and the inner barrels had some spotting, like the start of chrome rust, on the barrels.
 
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Old 08-15-2018, 12:14 PM
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dechrome

Originally Posted by Petza914 View Post
I think about $5,000 but it was 5 or 6 years ago. They show up in the marketplace here and on rennlist a few times/year and you didn't want these chrome ones - they were ridiculously heavy and the inner barrels had some spotting, like the start of chrome rust, on the barrels.
Those cost a fortune new and $5k is still a bargain.
 
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Old 08-15-2018, 09:37 PM
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Originally Posted by Petza914 View Post
Lots of good questions and thoughts here and I don't have the answers, only my personal experience with 5 different sets of wheels on two 997.1 C2S cars, and of those 5, the worst driving set were of the widths and offsets mentioned above, and the 2nd worst set were the chromed RUF wheels my car came with that were 10 lbs per wheel heavier than anything else I had on them, and why I sold them. Changing from these to the Champions and upgrading to PCCB brakes resulted in a major reduction in unsprung weight at each corner, and made a huge difference in steering feel and handling. On all of these sets I was running the same make, model, and size of tire.

I don't know if the Porsche GT cars have different steering rack ratios or some other factor that makes them drive better with the wider track and lower stance or why this particular set of wheels made the car handle what I'd consider poorly, but they did. With my Champions and Forgelines, the car drives perfectly straight and handles totally predictably, even up to speeds of 125 MPH or so. With these other wheels, lane changes at 85 or 90 had a completely different sensation and were not confidence inspiring.
The GT cars do have different suspension parts. Don't ask me exactly what parts are different because I don't know. Just know that they're different from the non GT cars. Also agree with your comment about Champion and Forgeline wheels. I've had them both and they're my favorite after market forged wheels for the 997 along with HRE. Only around 20 lbs. each and unsurpassed quality in terms of build quality and finish imo.
 
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