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Installed GT3 Control Arms

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Old 08-28-2006, 01:08 PM
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10 GT3
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Default Installed GT3 Control Arms

Well, I finally installed GT3 control arms on my car. First, I received very little accurate information form the many threads I made and resources I caontacted. There was a challenge in getting all the parts since no dealer in the country has a complete set. There are several that show to have 1 inner bearing flange, but they are being held for a customer. There are none at PCNA and they are back ordered at the factory. I want to thank "The Racer's Group" for hooking me up when I needed it.

Here are a few notes for anyone doing this as an upgrade:

1. The inner bearing flanges are the same part on both sides.

2. The outer control arms arm the same casting on both sides, only the placement of the track arm mounting holes are different. Since these are pressed in, there are 2 different part numbers. It a pinch you could get 2 of the same side, press out the track arm mount and re-press it back in re-clocked.

3. There is only 1 way they will fit properly on a 996 Carrera (sorry I didn't track it by part numbers): The control arms must be installed with the track arms set to push the control arms backwards toward the back of the car(reducing caster). Even in the center position the wheels will rub the inner fender liners toward the front bumper when turning.

4. The 7mm shims are very expensive, but only 1,2 or 3 mm shims. Two 3mm shims and a 1mm shim cost a lot less than a single 7mm shim.

5. For Bi-Xenon cars, you will need a special 1mm shim with a mounting ring to mount the auto headlight adjuster. This 1mm shim retailers for $180 and expect to pay over $130 with a good discount.

6. I started with 7mm of shims on each side. This set the toe way in. You will need 1/3 to 1/2 turn out on the tie rod ends for every 1mm of shims to correct for the toe-in.

7. When removing the old control arm, DO NOT USE A FORK-TYPE BALL-JOINT SPREADER. All it will do is tear the ball joint boot. You will need a scissor type spreader. NAPA is the only auto parts dealer I have found where you can get these. They have 2 different parts, each about $20. They will most likely be a special order item, but are in stock at the distribution centers.

8. When installing the new control arms, tighten the ball joint nut and the track arm bolt before tighten the control arm stud nuts. If you tight the stud nuts first, the control arm may bind up.

I will update this post with additional comments about shims and camber after I get my car aligned.
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Old 08-28-2006, 06:50 PM
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Additional information:

7b) When removing the old control arm, just hit the sides at the bottom with a hammer, not too hard. It will fall extremely easy by itself. Do not use a ball joint spreader. Just WD40 and the hammer, it takes 5 seconds.

- The inner flanges can be used at the front and the rear, at the left and at the right. Same part for all corners.

- If you want to save some money, don't buy camber shims from Porsche. Most of the Porsche race shops get those machined for cheap.

- The control arms can be used at any corner. Always use the center hole. If you want to use the eccentric hole, then you need a left and a right control arm. If you want to use the eccentric hole, you must not use the control arms at the rear. When using the eccentric holes at the front, it's required to remove the fender liners permanently, and too much caster will be the immediate consequence.

- The monoball bearing flanges with the solid bushing control arms cost $1300-$1500 each. That's over $6,000 for all corners plus labor. It's better to get the ERP Racing black solid bushing and the MotorsPorts monoball inner bearing flanges ($700 ea.)

The biggest advantage to add negative camber using GT3 control arms, is the increase in track and caster over the regular 996 Carrera. Moving the upper strut mount all the way inboard, increases the space to run wider front tires (255/265/275).
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Old 08-29-2006, 01:27 PM
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Some of your points are valid for GT3's and not Carreras. I only converted the fronts. There is no problem getting 2.5 degrees of negative camber out of the rear without modifications. The GT3 does have an adjustable rear arm, but it is not a necesssary upgrade. In fact, the adjustable rear was not on the MKI GT3. Going to GT3 front control arms allows significantly more camber adjustment without adding any harshness on the street. I do agree for a full race suspension on going with monoballs and solid bushings. As a few notes:

1. You can't run the control arms in the center holes on a Carrera. Even 225/40-18's rub the front fender liners. They must be run on the eccentric mounting holes positioning the control back. This also means that you can't get the caster gains you get on a GT3.

2. With factory type suspensions such as the ROW M030 suspenion I am running, there is a problem with most of the Monoball setups: the plates won't work with larger diameter springs. I initially looked at running ERP camber plates and they aren't compatible. Smart Racing Products went back and forth several times with ERP and confirmed it. There is no problem running them with GT3 threaded coilovers, JICs or PSS9s. The funny part is that there is far less of a tire clearance issue with the stock type suspensions since the spring is shorter and suspended above the tire on the strut. You can fit 255 tires on 9" wheels without a problem. With coilover suspensions, the spring is longer and the spring becomes the limiting factor for clearance.

3. Lubricating and using a hammer didn't work on my car for removing the stock control arms. Neither would a fork type puller. The scissor type worked like a champ and is what is shown in the factory service manual. I did initially install the outers on the wrong side. I was able to easily remove the GT3 outers them by partially re-installing the nut and using a socket extension on top to hit it with a 4lb hammer.

4. Installing these control arms does sunstantually increase the front track, over .5". My car will be getting aligned over the next couple of days. With only 7 mm of shims, I immediately gained about .8 degrees negative camber. I had to take 2.5 turns out of each tie rod end to correct for the initial toe-in.
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Old 08-30-2006, 07:52 PM
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HERE IS THE UPDATE AFTER THE ALIGNMENT:

For the alignment, I speced out -1.5 to -1.8 on the front camber. With only 7mm of shims, they could get over -1.7, but reduced it to -1.6. They set the rear to my requirement of best judgement under -2 degrees camber at -1.9 per side. The right front was set a little more aggressive than the left front to keep it from tramlining and pulling to the right on the street. Coincidentally, the tracks I drive are more aggressive on the right than the left. I actually gain a little caster even with the control arms set back. The car seems to drive fine and tracks well with the road. I don't notice any additional harshness. I'll get a better impression on race tires at the track this weekend.

I swapped to my race wheels tonight (18x9 front with 235/40 MPSCs and 18x11 rear with 295/30 MPSCs). My race tires used to ride softer on the street than my street tires. Now, they feel completely different. They feel a lot harder, more attached to the road. I can feel some fo the stiffeness from the inner sidewalls that was absent before. There is definitely more grip (my goal for this execise). Turn-in is crisp, but very stable. The additional caster is more noticeable in the steering wheels. Definitely a lot more front end bite. The back end tracks more and doesn't slide at much.

Last edited by 10 GT3; 08-31-2006 at 01:07 AM.
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Old 08-30-2006, 09:47 PM
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The 996 GT3 Mk2 also uses a 1-piece control arm at the rear. The 996 RS and 997 RS use the 2-piece control arm. The benefit from using the 2-piece version is that you can lock the camber eccentrics, and set the camber with shims. In this case the car will keep the alignment longer, especially for cars with a stiff suspension.

Using the monoball inner flanges for the control arms helps to minimize changes on dynamic camber.

I'm affraid that you might have used the left control arm on the right side and viceversa. The center hole provides less caster, the eccentric hole increases caster. However, if you swap the control arms (left to right, right to left), the eccentric hole will now be located toward the headlights, and in such case, using the eccentric holes will reduce caster.

The 996 GT3 uses the same body as the 996 Carrera 4 Narrow Body. The difference with the Carrera 2 body other than rigidity is that the front uprights on the C2 come from the Boxster. Using the C4 uprights allows to install the 996TT rotors/calipers, GT3 rotors/calipers/springs/shocks.

The ride height will affect the camber you can obtain, as well as the caster reading. Using 7mm shims on a GT3 brings caster to around 8.8-9.2 degrees and camber to -1.7 minimum (strut outboard) -2.5 degrees maximum (strut inboard). These values are for a car with a ride height at 115mm measured from the workshop recommended point.


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Old 08-31-2006, 12:59 AM
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You are correct that I installed the control arms flipped from side to side (like they would be on an RS) and I am using the eccentric holes aimed toward the headlights as stated earlier in this post. Even running the eccentric holes to push the control arms back, I still gained caster(close to 8 degrees); but it is still in factory spec. The reason why this is different is indeed more of a difference in the GT3 spindles (uprights) and the upper strut mounts. If installed any other way, there are significant rubbing issues on a Carrera.

The structural difference in the front of a GT3 is mostly from the forward firewall that would normally surround the front differential. The 02+ Carreras gained 3 additional brakes for the front strut towers essentually triangulating them.

Compared to the GT3 specs you listed:
1. I run more front camber than that range.
2. I run less front toe than that range.
3. I run minimal caster in that range range.
4. I run the maximum rear camber in that range.
5. I run the maximum rear toe in that range.

As a final note, I tracked my wear at the track on the MPSC's after the camber change. Bottom line, you won't need anymore camber than this. With my Longacre probe-type pyrometer, after getting tire pressures set right I was consistantly within 3-4 degrees across the entire tire both front and rear. The only thing I noticed is that I ended up dropping my cold pressures from 31 to 28 psi in front and from 34 to 29 psi out back. With my original pressures, they were getting too hot and losing grip. Once I changed my starting pressures; on the first lap of each run group, the tires want to shift a good bit as they warm up. They will still grip more than before, but they have to be brought up to the limit gradually. After the first lap, they are ready to run hard.

Last edited by 10 GT3; 09-04-2006 at 12:56 AM.
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Old 09-04-2006, 12:48 AM
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SPECIAL NOTE FOR BI-XENONS:

Bi-Xenons include auto-leveling on the 996. The auto-leveling works by using an electrical actuator that is mounted above the driver's side front control arm. The actuator has an arm that extends down to mount on the lower control arm. As the control arm moves up and down, the actuator changes position. It send a signal back to the motors in the headlights to raise or lower the lights. You will need to adapt this to the GT3 lower if you swap and want to keep this feature.

For anyone looking to do this swap with Litronics, there is a special 1mm shim to mount the arm for actuator for the auto-adjusting headlights. If you can guess, yes it is expensive. The retail price is $135. A good dealer would get it to you for about $100. There is only 1 dealer in the country that stocks it and wants $180 ($45 over retail for it). If you need one, just have it ordered through your dealer. Mine got it in less than a week from Germany for only $118 (including tax).
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Old 09-21-2006, 08:46 PM
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Would it be easier to install these on a C4 then?
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Old 09-22-2006, 06:10 PM
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No. It would be the same and you will need the same parts, including the special shim if you have auto-leveling headlights.
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Old 10-08-2006, 09:16 PM
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What are the advantages of going to the cost and trouble of using GT3 arms vs fitting camber plates to the front?

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Old 10-09-2006, 12:07 AM
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Originally Posted by Dfer
What are the advantages of going to the cost and trouble of using GT3 arms vs fitting camber plates to the front?

Dennis
Good question. I spent a couple of weeks researchign this before making a decision. First, the biggest advantage of the control arms is the gain in track. I gained over an inch. This will improve both cornering power and turn-in. Camber plates won't provide any track gain.

You will have issues fitting camber plates if you have stock-type suspensions (non-coilovers). This is obviously an issue for me since I run a ROW M030. The inexpensive camber plates like the Weltmeister/EVO camber plates aren't designed to work over the stock springs. They are design to work on coilovers like the GT3 or X74 suspensions. If you were to try to fit them over stock springs, the springs would be rubbing the strut towers (if you could get them to fit). Remember that the way a camber plate helps you gain camber is by moving the upper strut mount inwards. With coilovers the spring is much smaller in diameter and you have a lot more room to work with.

The other thing is you will get some additional harshness on the street with camber plates since they replace the upper rubber mounts with monoballs. The cost is pretty close to the same going with either.
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Old 10-09-2006, 08:38 PM
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Thanks for that info.
I run a 2001 Boxster S which I believe has the same suspension as a 996. I have PSS9's and 5mm and 15mm spacers fitted ( to accommodate the 8/10 inch x 18 inch track wheels I have fitted.

My local club ( in Victoria , Australia ) is just changing rules to allow for camber adjusting aids such as plates and GT3 control arms. The plates appeal as one of the sites I watch has an offer for the ones they developed which are much cheaper than others ( eg TRG ) . They are about $US 329 which is much cheaper than the arms I have seen advertised. What do you pay for the arms in the US?
http://www.epiqautosport.com/pro_box...es_schnell.php
The harshness is a bit of a worry - how bad is it? Anybody got plates on a daily driver?

Cheers

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Old 10-09-2006, 10:54 PM
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i did the gt3 arms in my cayman, works great. I didn't do the work so I can't give you details of the install.
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Old 10-11-2006, 01:08 AM
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i did the gt3 arms with erp camber plates with my moton coilovers. the control arms were flipped (inadvertently) but the center holes were used. i can fit 245/40-18s and there is no rubbing but i didn't use any spacers. i ended up with ~8.5 degrees caster.
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Old 10-13-2006, 06:16 AM
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Why have plates and arms?
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