991 GT3 Suspension Overview
04-08-2014, 04:14 PM
#31
Former Vendor
Thread Starter
04-08-2014, 08:41 PM
#33
I see no technical reason this car can't run slicks. The Cup cars run slicks and have essentially the same suspension. We'll be getting up close and personal with a 991 GT3 Cup car to really identify the differences soon.
On the Cup cars, I expect to see more spherical bearings in place of rubber, no rear steer, bladed swaybars - we'll see.
I suspect there are non-technical motives for the no-slick policy.
On the Cup cars, I expect to see more spherical bearings in place of rubber, no rear steer, bladed swaybars - we'll see.
I suspect there are non-technical motives for the no-slick policy.
You guys are definitely suspension experts!
Your web address is bookmarked.
04-09-2014, 07:54 AM
#36
Instructor
Join Date: Mar 2014
Location: Adelaide, South Australia
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Brilliant write-up and photos!
Interestingly, the front wheel carrier/hub carrier/steering knuckle is stamped "Made in Italy" with the Brembo logo on it; I wonder why Porsche didn't manufacture that in house - perhaps something to do with the double-shear design?
Scott.
-------
2014 991 GT3 - in Adelaide, waiting for new engine; seen, touched, and sat in!
2007 Audi RS4
1999 Subaru Impreza WRX STi
Interestingly, the front wheel carrier/hub carrier/steering knuckle is stamped "Made in Italy" with the Brembo logo on it; I wonder why Porsche didn't manufacture that in house - perhaps something to do with the double-shear design?
Scott.
-------
2014 991 GT3 - in Adelaide, waiting for new engine; seen, touched, and sat in!
2007 Audi RS4
1999 Subaru Impreza WRX STi
04-10-2014, 09:15 AM
#37
Rennlist Member
Join Date: Feb 2006
Location: Wishing I Was At The Track
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Take a look at this partial supplier list for the Cayman: http://www.autonews.com/article/2009...educe-fuel-use
04-10-2014, 11:37 PM
#38
Rennlist Member
Great stuff! Edmund's has suspension walk-around write-ups as well...but not as good!
04-11-2014, 06:47 PM
#39
Nordschleife Master
I see no technical reason this car can't run slicks. The Cup cars run slicks and have essentially the same suspension. We'll be getting up close and personal with a 991 GT3 Cup car to really identify the differences soon.
On the Cup cars, I expect to see more spherical bearings in place of rubber, no rear steer, bladed swaybars - we'll see.
I suspect there are non-technical motives for the no-slick policy.
On the Cup cars, I expect to see more spherical bearings in place of rubber, no rear steer, bladed swaybars - we'll see.
I suspect there are non-technical motives for the no-slick policy.
04-12-2014, 06:10 PM
#40
Former Vendor
that is possible, but I think unlikely.
If the RWS system is too fragile to handle slicks, then they cut the design safety factors too close. True enough the robustness and longevity of the system remains to be seen.
If the system can't survive slicks, what will happen as performance street tire technology continues to improve - as it has in the past?
I should trust that Porsche over-engineered in enough safety factor to handle this.
If the RWS system is too fragile to handle slicks, then they cut the design safety factors too close. True enough the robustness and longevity of the system remains to be seen.
If the system can't survive slicks, what will happen as performance street tire technology continues to improve - as it has in the past?
I should trust that Porsche over-engineered in enough safety factor to handle this.
04-12-2014, 08:39 PM
#41
Nordschleife Master
that is possible, but I think unlikely.
If the RWS system is too fragile to handle slicks, then they cut the design safety factors too close. True enough the robustness and longevity of the system remains to be seen.
If the system can't survive slicks, what will happen as performance street tire technology continues to improve - as it has in the past?
I should trust that Porsche over-engineered in enough safety factor to handle this.
If the RWS system is too fragile to handle slicks, then they cut the design safety factors too close. True enough the robustness and longevity of the system remains to be seen.
If the system can't survive slicks, what will happen as performance street tire technology continues to improve - as it has in the past?
I should trust that Porsche over-engineered in enough safety factor to handle this.
I think the no-slick warning was placed because the use of slicks changes the dictated service intervals for certain components. They don't want a failure because someone thought that the service interval for hubs are the same for slick vs non slick tires.
04-13-2014, 03:08 PM
#42
Thanks. I would agree with you! I think the no-slick warning was placed because the use of slicks changes the dictated service intervals for certain components. They don't want a failure because someone thought that the service interval for hubs are the same for slick vs non slick tires.
I think the no-slick warning was placed because the use of slicks changes the dictated service intervals for certain components. They don't want a failure because someone thought that the service interval for hubs are the same for slick vs non slick tires.
05-19-2015, 03:11 PM
#43
So does the 991 GT3 for sure not have an off-center hole in the A-arm bushing that would let one adjust caster by pressing it out? Your article on the difference between the 991 GT3 and 991 Cup Car suspension suggests that it in fact does. Is that a typo? http://www.elephantracing.com/tool-b...Comparison.htm
The GT3 also has two bores in this place as well, however the rubber bushing cannot be rotated without being pressed out. The inner bore is set as default, and the outer bore is used to offset caster when the length of the lower control arms is extended beyond a certain range.
Hi Sam, all good questions.
1- There are two ways to increase camber (a) at the strut top camber plate (b) by extending the lower control arm. Method (a) does not cause an increase in caster angle. Method (b) does increase the caster angle.
The reason this happens with (b), as the lower control arm is lengthened it does not extend straight out. Instead the diagonal member attached to the bushing in the middle of the lower control arm
forces an arc path to be followed. The ball joint end of the lower control arm is drawn forward and caster is increased.
This picture illustrates what happens:
2- The old style 996/997 GT3 lower control arms managed this by have two positions for the diagonal member to attach, thus creating two caster positions and allowing at least a crude compensation for
the lengthened control arm. Note the intersecting holes drilled in the bushing. This is what your car has had retrofit.
Buying those 996 GT3 control arms is really the long way around (read expensive) to getting the caster reducing bushings. We have a product to solve this problem. Our product provides a solid bushing
replacement that is rotatable to provide caster adjustment. It has more range than the 996 GT3 bushes, and is adjustable instead of 2 position limited.
Here is our caster adjuster installed on a regular control arm (non-GT3), but if fits the GT3 front arms too.
The caster adjuster is on our website here
3- It would be best to replace the stock bushings with well-extended lower control arms. As you experienced, tire rub can happen and you likely have excessive caster at that point.
1- There are two ways to increase camber (a) at the strut top camber plate (b) by extending the lower control arm. Method (a) does not cause an increase in caster angle. Method (b) does increase the caster angle.
The reason this happens with (b), as the lower control arm is lengthened it does not extend straight out. Instead the diagonal member attached to the bushing in the middle of the lower control arm
forces an arc path to be followed. The ball joint end of the lower control arm is drawn forward and caster is increased.
This picture illustrates what happens:
2- The old style 996/997 GT3 lower control arms managed this by have two positions for the diagonal member to attach, thus creating two caster positions and allowing at least a crude compensation for
the lengthened control arm. Note the intersecting holes drilled in the bushing. This is what your car has had retrofit.
Buying those 996 GT3 control arms is really the long way around (read expensive) to getting the caster reducing bushings. We have a product to solve this problem. Our product provides a solid bushing
replacement that is rotatable to provide caster adjustment. It has more range than the 996 GT3 bushes, and is adjustable instead of 2 position limited.
Here is our caster adjuster installed on a regular control arm (non-GT3), but if fits the GT3 front arms too.
The caster adjuster is on our website here
3- It would be best to replace the stock bushings with well-extended lower control arms. As you experienced, tire rub can happen and you likely have excessive caster at that point.
12-11-2019, 09:39 AM
#44
Rennlist Member
just read the GT3 suspension overview. for those who haven't read it, now is time.
Thanks to Elephant Racing.
https://www.elephantracing.com/tech-...sion-overview/
btw, I'm looking to upgrade my GT3 suspension set up for local DE.
Thanks to Elephant Racing.
https://www.elephantracing.com/tech-...sion-overview/
btw, I'm looking to upgrade my GT3 suspension set up for local DE.
12-11-2019, 04:50 PM
#45
Be aware, that as you evaluate all the suspension goodies or upgrades, not all of them are the same.
Example, there are many who produce adjustable thrust arm / caster bushings. But not all of them have the same range of adjustment.
This can prove to be a limiting factor if you are moving to aggressive negative camber up front.
Bruce
BRracing
Example, there are many who produce adjustable thrust arm / caster bushings. But not all of them have the same range of adjustment.
This can prove to be a limiting factor if you are moving to aggressive negative camber up front.
Bruce
BRracing