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After experiencing with some different wheel spacers, I concluded that I’ll remove any spacers from my setup suspension, I prefer the Porsche Performance Geometry better than the look. OEM Porsche Suspension on 991 came with Negative Scrub Radius setup, and here are the Cons using spacers :
“The Negatives
The main issue with a wheel spacer is that it moves the wheel to a wider position whilst the rest of the suspension arms remain in the same place. In particular, the king pin inclination axis remains in the same place. Therefore, fitting a wheel spacer moves the wheel outboard and alters the scrub radius of the car. It is important to know whether your car currently has negative or positive scrub radius and ideally how much it has. Fitting a wheel spacer will increase the positive scrub radius at the front wheels which has some unfavorable consequences.
If your car already has a bit of positive scrub radius then the wheel spacer will increase it. An increase in positive scrub radius increases the forces on the steering rack under braking conditions. Any bumps in the road will also be amplified through the steering wheel, making the steering jerky and more unpredictable. Twitching wheels when braking can cause the tire to lose grip and ultimately can cause the wheels to lock up and slide. An increase in positive scrub radius also causes the wheel to gain positive camber when the wheels are being turned, reducing grip in corners on the front wheels and producing understeer.If your car has the more favorable set up of negative scrub radius then installing a wheel spacer can cause bigger issues. The outward movement of the wheel can make a negative scrub radius become zero. This is the worst position for it to be in. A zero scrub radius can cause squirm. This is where a scrubbing action occurs on both front tyres in opposite directions which can create unpredictable handling in corners and can lead to understeer too.
Secondly, installing wheel spacers on a car increases the leverage on the wheel bearing. The larger the spacer, the larger the leverage becomes. This reduces the life of the wheel bearing as they are not made to take leverage forces and can therefore wear faster, increasing rolling resistance and power loss of the car.
Finally, the wheel spacer moves the wheel further away from the damper mounting point. This means that the wheel will have a larger effect upon the damper and will act upon it with more leverage. This effectively makes the spring and damper softer and less effective on the wheel. This means that the car can roll more on corner entry and exit and feel generally softer out on track or on the road.”
I hope I do not offend someone's delicate sensibilities, but any application of spacers that move the wheel and/or tire beyond what is, objectively, at the most, flush with the wheel opening looks silly, in my opinion.
Just FYI: 5 mm spacers were a factory option on the original 991.1. There is a specific factory alignment for 991.1 C2S with spacers, 20 in wheels and SportPASM- among the 10 or so that Porsche specifies for various 991s.
Getting the correct one on any car that has been in service for a while, by a competent tech with a new Hunter rack, is like getting a new car. In my case, having it done at 40k miles was like getting a better than new car in terms of handling for street use.
Just FYI: 5 mm spacers were a factory option on the original 991.1. There is a specific factory alignment for 991.1 C2S with spacers, 20 in wheels and SportPASM- among the 10 or so that Porsche recommends for various 991s.
Getting the correct one on any car that has been in service for a while, by a competent tech with a new Hunter rack, is like getting a new car. In my case, having it done at 40k miles was like getting a better than new car in terms of handling.
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I have seen my car aligned several times by the dealer and an independent who provides me with track support. I have never seen a setting on a Hunter Alignment machine for cars with spacers (even though I recognize that there is a separate set of alignment specs for cars without PASM, with PASM and with Sport PASM). Are you sure about that?
The only way to enhance the look to a wider appearance is to install custom "thicker" wheels using same offset as original. but a good set will be no cheap!!
Just FYI: 5 mm spacers were a factory option on the original 991.1. There is a specific factory alignment for 991.1 C2S with spacers, 20 in wheels and SportPASM- among the 10 or so that Porsche specifies for various 991s.
Getting the correct one on any car that has been in service for a while, by a competent tech with a new Hunter rack, is like getting a new car. In my case, having it done at 40k miles was like getting a better than new car in terms of handling for street use.
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Porsche technicians at my Dealer said to me that the OEM Scrub Radius on 991 is just under 10mm NEGATIVE. that means, if you are using 5mm you still negative, which is fine!
This is my alignment report after dropped my CarreraT ( RAS) with H&R springs and 5mm spacers in all corners , The technician at my Porsche Dealer introduced info to the alignment machine about the 5mm spacers, and the results were under OEM specifications and works perfect!
Based on the technical explanations regarding scrub radius the most valid point is to have alignment checked, same goes for changing the springs as this change will likely have some effect on scrub radius. Most 991s have the front wheels tucked in further with lowering/sport springs. That being said I may adjust my spacers to a more conservative setup but certainly with a wider front spacer than rear spacer to give more turn in. Friends of mine with OE Carrera T alignment and no spacers constantly chew up the outsides of their OE Pirellis and Michelins on just 1 or 2 track days. I have 3 track days on my Pirellis (one at WSIR) and T2 is the tire shredder! My tires have even wear. I add camber via the strut mount adjustment for this track and it is very helpful in conjunction with 15mm front and 7mm rear spacers. My modified set up would be 5mm rear spacers (OE option) and perhaps 10-12mm front spacers and call it a day. This gives a track width closer to the GTS with the 9” and 12” CL wheels. Later I will go with 20x9 and 20x12 wheels with an offset close to OE. Thanks again for all the helpful info! Canyon run to Malibu attached.
Based on the technical explanations regarding scrub radius the most valid point is to have alignment checked, same goes for changing the springs as this change will likely have some effect on scrub radius. Most 991s have the front wheels tucked in further with lowering/sport springs. That being said I may adjust my spacers to a more conservative setup but certainly with a wider front spacer than rear spacer to give more turn in. Friends of mine with OE Carrera T alignment and no spacers constantly chew up the outsides of their OE Pirellis and Michelins on just 1 or 2 track days. I have 3 track days on my Pirellis (one at WSIR) and T2 is the tire shredder! My tires have even wear. I add camber via the strut mount adjustment for this track and it is very helpful in conjunction with 15mm front and 7mm rear spacers. My modified set up would be 5mm rear spacers (OE option) and perhaps 10-12mm front spacers and call it a day. This gives a track width closer to the GTS with the 9” and 12” CL wheels. Later I will go with 20x9 and 20x12 wheels with an offset close to OE. Thanks again for all the helpful info! Canyon run to Malibu attached.
. I agree with you, this tread help us to share and learn great information!
Also you brought a couple of very interesting points, the first one is that not everybody have same driving needs, so alignment values must be different. for street use, alignment values must be focused to straight line, or if the track is the matter, more aggressive values should perform for cornering. and the second thing is that if somebody install Sport Springs, alignment values should be fixed right away, because as you said, the Scrub Radius is affected by the huge alteration on the resulting negative camber, caused by the shorter spring . Fortunately Porsche 991 have the fully option to setup suspension working fine with Sport springs, (H&R values like length and pressure are very similar to the 20mm OEM springs)
About your friends who track they cars and noticed excessive wear outwards of the front tires, it is not necessarily because the lack of spacers, but more because maybe they used conservatives values of -1.0 camber, which are ideal for street use,but not on the track. recommended value for track should be at least -1.2 Camber/Front or more to eliminate uneven wear!
The important thing here to understand, is as you said, that there is not any setup with spacers or without, if it is not followed by a proper alignment. Nice Picture on the Canyons!!!
here is my green Lizard for the track !
Last edited by rubioalejo; 04-28-2020 at 12:39 AM.
^Scion afraid of someone stealing the van full of coke?
Good information in this post, an alignment to how you drive your car is spot on.
People who track or drive more aggressively and don't care as much about tire wear for a long commute will get better driving and wear with the correct alignment for them.
Anyoine with a car that doesn't know when it was last done should spend the $200 or whatever for an alignment at the dealership or knowledgeable performance shop. Every used car I've bought has driven better with some fresh tires and an alignment. When I bought my 991s the guy had spent for new PS4s and skipped the alignment, but he did ceramic coat the wheels.
I have seen my car aligned several times by the dealer and an independent who provides me with track support. I have never seen a setting on a Hunter Alignment machine for cars with spacers (even though I recognize that there is a separate set of alignment specs for cars without PASM, with PASM and with Sport PASM). Are you sure about that?
Good point. No I am not sure about a specific factory alignment spec for spacers. I just assumed that given the tech advised that there were many different specs for 991.1 depending on how it was configured.
The point I wanted to make was that a proper alignment (which certainly should include tweaks for your intended use) has pay off. Folks get hung up on wheels/tires/spacers and add-ons. Getting and keeping a car aligned is easily overlooked as basic thing, like having oil in the engine.
The point I wanted to make was that a proper alignment (which certainly should include tweaks for your intended use) has pay off. Folks get hung up on wheels/tires/spacers and add-ons. Getting and keeping a car aligned is easily overlooked as basic thing, like having oil in the engine.
This^
With all the concerns over cosmetic details, ceramics, etc, tires and alignment I wonder how many never think to get an alignment just cause it has new tires and drives good.
04-27-2020, 03:11 PM
