GT3 control arms on a 996
05-03-2007, 10:55 AM
#32
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damn jim, that's one beefy toe arm. is that an ERP piece? it looks twice as thick as the tarett/TRP toe arm.
Originally Posted by JimB
OK it's 5:30 in the morning here and I'm taking suspension pictures. What's wrong with that picture.
Anyway, here's a pretty good picture of what is probably about as good as 996 suspensions get. In the picture the two smaller upper contol arms are pretty clear connecting the top of the hub to the chassis. The stock parts are not adjustable. These are ERP parts and allow you to push the top of the tire out or pull it in.
The large contol arm on the bottom (with the part number marked on it) is the lower control arm. It's a little hard to see where the lower control arm splits but it's near the chassis. The eccentric bolt is pretty clear.
You can see the rear tie rod (closest to you) running from the hub to the chassis. It's eccentric is somewhat covered by the swaybar. This part is the Porsche Motorsport version but yours look similar.
The tie rod is what you use to adjust toe. Changing camber changes toe but you then use the tie rod to correct it. If you are happy with the amount of camber you have and can't get enough toe then your tie-rods are not long enough. Like others, I'm a little preplexed by that. We had problems with the front tie rods not being long enough but the only problem we had with the rears was the very weak ball joints.
Does that help?
Anyway, here's a pretty good picture of what is probably about as good as 996 suspensions get. In the picture the two smaller upper contol arms are pretty clear connecting the top of the hub to the chassis. The stock parts are not adjustable. These are ERP parts and allow you to push the top of the tire out or pull it in.
The large contol arm on the bottom (with the part number marked on it) is the lower control arm. It's a little hard to see where the lower control arm splits but it's near the chassis. The eccentric bolt is pretty clear.
You can see the rear tie rod (closest to you) running from the hub to the chassis. It's eccentric is somewhat covered by the swaybar. This part is the Porsche Motorsport version but yours look similar.
The tie rod is what you use to adjust toe. Changing camber changes toe but you then use the tie rod to correct it. If you are happy with the amount of camber you have and can't get enough toe then your tie-rods are not long enough. Like others, I'm a little preplexed by that. We had problems with the front tie rods not being long enough but the only problem we had with the rears was the very weak ball joints.
Does that help?
05-03-2007, 11:05 AM
#33
Originally Posted by JimB
BTW, you can't use tire temps to determine optimal grip. Optimal grip will result in excessive wear and excessive heat on the inside edge. Why? Because when the camber is optimal for corners it's overheating the inside edges going down the straights. If you have even temps and even wear you are leaving lots of corner grip on the table.
Jim
Keep in mind that each different type of tire has a different optimal operating temperature and the tire contstruction severly influences the optimal suspension settings. The cars suspension (spring rates, bushing rates and caster) are also major factors that effect optimal settings. Caster is the camber gain while turning. Stiffer suspensions need more static camber since they can't gain it in a corner.
If you want to learn a lot more on this I highly recommmend the Evolution Dial-In Course. http://autocross.com/evolution/modules/news/ This is taught by national autocrossing champions. They will teach everything you will ever need to know about spring rates, shock rates, sway cars, alignments, tire pressures, contact patch and turn-in. You also get to see it first hand on the skidpad, slaloms and sweepers.
05-03-2007, 11:06 AM
#34
Originally Posted by JimB
BTW, you can't use tire temps to determine optimal grip. Optimal grip will result in excessive wear and excessive heat on the inside edge. Why? Because when the camber is optimal for corners it's overheating the inside edges going down the straights. If you have even temps and even wear you are leaving lots of corner grip on the table.
Jim
Keep in mind that each different type of tire has a different optimal operating temperature and the tire contstruction severly influences the optimal suspension settings. The cars suspension (spring rates, bushing rates and caster) are also major factors that effect optimal settings. Caster is the camber gain while turning. Stiffer suspensions need more static camber since they can't gain it in a corner.
If you want to learn a lot more on this I highly recommmend the Evolution Dial-In Course. http://autocross.com/evolution This is taught by national autocrossing champions. They will teach everything you will ever need to know about spring rates, shock rates, sway cars, alignments, tire pressures, contact patch and turn-in. You also get to see it first hand on the skidpad, slaloms and sweepers.
05-03-2007, 11:21 AM
#35
I have never been so informed on here in my life you guys ROCK 
Keep em coming. i am going to try some track time in August when I get back home so I will try to put some of this to good use.
Keep em coming. i am going to try some track time in August when I get back home so I will try to put some of this to good use.
05-03-2007, 11:34 AM
#36
Excellent info!
So the only reason to change the rear toe links would be if there is a need to adjust toe more than the standard parts allow (which should be rare)?
Or perhaps if they are too weak for racing.
This is what it says on the TRG web page:
"Rear Toe Arms
These toe links feature a heim joint that eliminates the rubber bushing at the eccentric and usage of the eccentric for adjustment. Improves control of toe changes under acceleration, braking and cornering. Includes bushings for subframe attachment."
Would the heim joint help keeping the toe more constant during acceleration, breaking and cornering??
So the only reason to change the rear toe links would be if there is a need to adjust toe more than the standard parts allow (which should be rare)?
Or perhaps if they are too weak for racing.
This is what it says on the TRG web page:
"Rear Toe Arms
These toe links feature a heim joint that eliminates the rubber bushing at the eccentric and usage of the eccentric for adjustment. Improves control of toe changes under acceleration, braking and cornering. Includes bushings for subframe attachment."
Would the heim joint help keeping the toe more constant during acceleration, breaking and cornering??
05-03-2007, 11:51 AM
#37
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the toe eccentrics have been known to easily go out of alignment from track use. the reason for using the locking plates is to eliminate the eccentric. then to adjust toe, use the toe links that are offered by tarett/TRG/porsche motorsport. the spherical bearings/solid bushings prevent any deflection, i.e., toe change.
this mod is pretty much overkill for street use.
this mod is pretty much overkill for street use.
Originally Posted by MagnusB
Excellent info!
So the only reason to change the rear toe links would be if there is a need to adjust toe more than the standard parts allow (which should be rare)?
Or perhaps if they are too weak for racing.
This is what it says on the TRG web page:
"Rear Toe Arms
These toe links feature a heim joint that eliminates the rubber bushing at the eccentric and usage of the eccentric for adjustment. Improves control of toe changes under acceleration, braking and cornering. Includes bushings for subframe attachment."
Would the heim joint help keeping the toe more constant during acceleration, breaking and cornering??
So the only reason to change the rear toe links would be if there is a need to adjust toe more than the standard parts allow (which should be rare)?
Or perhaps if they are too weak for racing.
This is what it says on the TRG web page:
"Rear Toe Arms
These toe links feature a heim joint that eliminates the rubber bushing at the eccentric and usage of the eccentric for adjustment. Improves control of toe changes under acceleration, braking and cornering. Includes bushings for subframe attachment."
Would the heim joint help keeping the toe more constant during acceleration, breaking and cornering??
05-03-2007, 11:53 AM
#38
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Carlos,
The toe arm (aka rear tie rod) is the beefier version that Porsche Motorsports came out with a couple of years ago. They are pretty spendy. Around $800 I think but I haven't had any issues since I put them in. Before that I would go through several sets a year.
Carrera,
Where do I start? First I don't think I said anything about using tire pressures to determine grip. I said even tire temps don't indicate a setup with optimal grip. The article you referenced is about autocross. In autocross you are constantly turning with very few straights so using tire temps is a valid way of finding grip. It’s not as easy on the track because any amount of camber will cause the inside of your tires to heat on the straights. Therefore, if your tires are optimal in the corners, they will be heating the insides on the straights. That’s why fast track cars will never have even tire wear. At a track where there are a series of corners before the pits you will see more even temps. At a track where there is a straight before the pits they will be pretty far off.
BTW, I don’t recommend the running enough camber to achieve optimal grip unless you are going to really stay on top of your tires. And, have a big budget.
Jim
The toe arm (aka rear tie rod) is the beefier version that Porsche Motorsports came out with a couple of years ago. They are pretty spendy. Around $800 I think but I haven't had any issues since I put them in. Before that I would go through several sets a year.
Carrera,
Where do I start? First I don't think I said anything about using tire pressures to determine grip. I said even tire temps don't indicate a setup with optimal grip. The article you referenced is about autocross. In autocross you are constantly turning with very few straights so using tire temps is a valid way of finding grip. It’s not as easy on the track because any amount of camber will cause the inside of your tires to heat on the straights. Therefore, if your tires are optimal in the corners, they will be heating the insides on the straights. That’s why fast track cars will never have even tire wear. At a track where there are a series of corners before the pits you will see more even temps. At a track where there is a straight before the pits they will be pretty far off.
BTW, I don’t recommend the running enough camber to achieve optimal grip unless you are going to really stay on top of your tires. And, have a big budget.
Jim
05-03-2007, 11:57 AM
#39
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Originally Posted by karlooz
the toe eccentrics have been known to easily go out of alignment from track use. the reason for using the locking plates is to eliminate the eccentric. then to adjust toe, use the toe links that are offered by tarett/TRG/porsche motorsport. the spherical bearings/solid bushings prevent any deflection, i.e., toe change.
this mod is pretty much overkill for street use.
this mod is pretty much overkill for street use.
05-03-2007, 02:21 PM
#40
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Thanks for the info guys. I'm going to another friend of mine today and have him look at it to see if he can fix the toe without changing the arm. I too was a little surprised that there was a toe issue, or any alignment issue, using the factory X74 suspension. Granted it lowed the car about 30 mm in the back but you'd think that Porsche would have considered that.
In the event that I do decided to upgrade the upper control arms, where can I get the ERP version?
In the event that I do decided to upgrade the upper control arms, where can I get the ERP version?
05-03-2007, 02:24 PM
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Originally Posted by viper501
Thanks for the info guys. I'm going to another friend of mine today and have him look at it to see if he can fix the toe without changing the arm. I too was a little surprised that there was a toe issue, or any alignment issue, using the factory X74 suspension. Granted it lowed the car about 30 mm in the back but you'd think that Porsche would have considered that.
In the event that I do decided to upgrade the upper control arms, where can I get the ERP version?
In the event that I do decided to upgrade the upper control arms, where can I get the ERP version?
try http://smartracingproducts.com/ for ERP parts. they have some ERP parts in their catalog.
05-03-2007, 03:48 PM
#42
Nordschleife Master
Originally Posted by MagnusB
Excellent info!
So the only reason to change the rear toe links would be if there is a need to adjust toe more than the standard parts allow (which should be rare)?
So the only reason to change the rear toe links would be if there is a need to adjust toe more than the standard parts allow (which should be rare)?
05-03-2007, 03:50 PM
#43
Originally Posted by LVDell
Not really. The two HUGE benefits of having upgraded TOE ARMS is (1) the ability to keep the toe constant and not have to keep re-aligning your car all the time b/c the factory toe arms fall out of spec VERY easily; and (2) more importantly (for us track guys) is the removal (or serious decrease) in bump steer. Having toe changes at speed especially on a sweeper is ground for some serious trouble.
05-03-2007, 03:54 PM
#44
Nordschleife Master
The eccentric is what is used on the stock arms to adjust the toe but on the TRG (etc.) arms you eliminate that and adjust at the turnbuckle. Because of the design of the stock arms they are VERY susceptible to eccentric movement under stress and thus changing toe settings.
05-03-2007, 03:56 PM
#45
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Originally Posted by LVDell
The eccentric is what is used on the stock arms to adjust the toe but on the TRG (etc.) arms you eliminate that and adjust at the turnbuckle. Because of the design of the stock arms they are VERY susceptible to eccentric movement under stress and thus changing toe settings.
