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Discussion Starter #1
Looking to get my 981 setup to be more capable at the track. Have been doing this for quite a while but first time in a Porsche !

I have 981 GTS with X73 suspension

tire are DOT R-compound tires like NT01 and in the future Advan A052 (street tire but extremely grippy faster than nt01) etc.

so far tried a maxed out alignment without changing any parts.
front camber -1.7, rear camber -2.2
front toe 0, rear 1/8 total toe in
it's ok but not quite happy with the overall performance

next step i'm looking to do is change the suspension arm to get front -3deg camber, and rear -2.8deg camber

it seems the proper setup is front/rear GT3 LCA (thinking tarett gt3), with solid inboard bushing, and solid thrust arm bushing.
change rear toe link to a spherical bearing toe link.

i have 4 questions
1. should i change the thrust arm front and rear as well? with my planned setup, i'll have solid bushing in all locations except the front thrust arm bushing (chassis side)
2. with the LCA, should i use solid thrust arm bushing in front and rear, or just rear? what's the pro and con of adjustable vs non adjustable thrust arm bushing (control arm side)
3. is there an optimal caster setting? it seems changing the LCA like this would affect the caster quite abit, should i just get adjustable thrust arm bushing (control arm side) to adjust caster back in the 9-10deg range? How should i optimize the thrust arm vs control arm interaction?
It seems to me there is more to it then just setting the caster and then the camber. or is it really just that simple?
4. i see Manthey racing in their GT4 track package also included a replacement inner tie rod. Is this necessary?
 

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I would go with the Tarett GT3 or better the Tarett CUP LCA's with the solid red thrust puck f & R, The reason is to push your track out 20mm from the internal shims in the LCA's, while adding -2.0 degrees of negative camber. A relative good setup would be -3.0 degrees of front camber and -2.6 degrees of rear. The solid thrust pucks really aid in turnin, throttle modulation and controlling rear under threshold braking. I would have your shop set the caster to as close to OEM as possible, I believe I was able to get 8.4 caster with coilovers setup which is a total of 34mm of drop from standard, yours will be more like 25mm from standard. With the solid thrust puck and the monoballs on the LCA's, you can actually set your front toe to a toe out of 5 minutes and reduce your rear toe in to 12 minutes. If you have rubber instead of solid monoballs on either end of your LCA's, then I would not recommend this as the rubber allows your LCA's to move around too much, which will cause you to experience some toe steer.

I would leave the OEM thrust arm alone except if rubber bushing is shot to allow some compliance for street drivability. Your Tarett GT3 or Cup arms will be very solid. Solid (chassis side)monoball thrust arm could be added at a later point if needed.

Lastly, by having adjustable toe links on a dropped car, you can also add adjustable bump steer to some links. Elephant offer excellent toe links with bump steer adjustments which I have. This is tricky to setup correctly by your shop as the idea is to go through your entire droop/compression of each axle to adjust the link to parallel to the LCA at midpoint of the suspension arc. Usually the shop will need to remove the springs, or attach weight to the middle of the rear end for compression and lift the car while on the rack for droop, then test the arc for midpoint and add or subtract the washers between the toe link's monoball stud and the upright. I have had a corner balance done with Ohlins coilovers, so the arc is slightly different on the drivers side even with 200 lbs added to the driver's seat. I can visually see the washers are different from the right rear to the left rear. Ideal adjustments would be a parallelogram between the LCA's and the rear toe link at the mid point of the arc and as close as possible with the adjustment washers at the 1 inch compression and droop.
 

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Discussion Starter #3
thanks for the info !

so i purchased a full set of RSS control arm and tie rod ends toe links etc. got the XL version to get to the -3 front camber target easier.

now thinking about it abit more, i'm wondering if the stock shock top hat on the X73 suspension will be able to handle the -3 camber?
i'm assuming it's just a rubber top hat? is it asking too much for it to rotate that much with the longer lower control arm to get the -3 camber?
 

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You should be able to slide the camber adjustment three bolt assembly inward enough to gain -3.0 camber with your LCA's internal 20 mm shims in place. You can also use a Tarett camber plate with a monoball, but know that these monoballs do wear out and rattle. That is the reason many chose to stay with the OEM setup. You might want to replace the rubber spring bearing before reassembly. I had my installer slot the top mounting holes on one side more to even out the maximum camber. These cars are not exactly perfect, as the alignment guys will tell you. That is why a really good alignment rack is important to getting an aggressive setup to work properly, especially the rear toe in with a lowered car.

With solid thrust pucks in place front and rear, you can have a front toe out setup of 5 minutes and 12 minutes of toe in in the rear. This setup will give you quicker turnin and at the same time prevent slight rear steer mid corner with throttle modulation due to flux from the OEM LCA's bushings. To counter any threshold braking wobble, I would also suggest a OEM (718) rear frame brace or Pedro's TechnoBrace 2 to keep the two rear frame rails exactly in place. Its only about $100 and easy to install.

Lastly, take a look at Function First Orange motor mount insert to help prevent motor movement, which also aids in turn in. I use this one as it's the least offensive NVH of the three inserts. Others also use FF transmission mounts to really stiffen up the motor/transmission, but I believe add too much NVH to my daily drives, the GT3 transmission mount gives excellent support, without NVH, my recommendation.
 

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I am running RSS non-XL arms front and rear, solid pucks, rear toe locking plates, and GT4 Clubsport tie rods. I left the upper plates and the factory position in the slots and still achieved -3.0 and -2.5 with 22mm and 7mm shims, respectively. Supposedly bumpsteer it is off a little with PASM and a little more with X73 but the car as no ill effects at the moment so I haven't bothered.

Here the Suspension and Alignment post in my track journal.

I run a 245 up front on an 8.5" wheel and the wheel/tire package fills the front wheel well. I will be installing some Rennline front camber plates to net the same camber but with fewer shims so I can get a 245 or 255 on a 9" wheel. Right now a 9" wheel doesn't fit under the fender. I have driven years on numerous monoball upper plate designs, both strut and shock, without experiencing the monoball rattle so many Porsche owners warn against. It'll be interesting to see if they start and stay quiet.

The car does have threshold braking wobble but I haven't done anything to address it yet.
 

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Is the reason the 9 in wheels do not fit the wheelwell is the wheel offset with 22mm of shims in the LCA is pushing out the track too far causing tire rub on the lip? I thought that 20mm shims was as far as most LCA's can safely handle, at least that is what Ira from Tarett told me. Is that the reason for RSS XL reinforced version to add more shims?

Try a Pedro's TechnoBrace 2 or a 718 rear frame brace in the rear to control the braking wobble. It's a cheap fix and it keeps the rear subframes in relative alignment during the droop phase of threshold braking.
 

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This is one of the reasons I like the SPL LCAs a lot. You don't need shims and the adjustment range is as much as you'll ever need.

Is the reason the 9 in wheels do not fit the wheelwell is the wheel offset with 22mm of shims in the LCA is pushing out the track too far causing tire rub on the lip? I thought that 20mm shims was as far as most LCA's can safely handle, at least that is what Ira from Tarett told me. Is that the reason for RSS XL reinforced version to add more shims?

Try a Pedro's Technobrace in the rear to control the braking wobble. It's a cheap fix and it keeps the rear subframes in relative alignment during the droop phase of threshold braking.
 

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Is the reason the 9 in wheels do not fit the wheelwell is the wheel offset with 22mm of shims in the LCA is pushing out the track too far causing tire rub on the lip? I thought that 20mm shims was as far as most LCA's can safely handle, at least that is what Ira from Tarett told me. Is that the reason for RSS XL reinforced version to add more shims?
An 8.5" wheel and 22 mm of LCA shims leave ~5mm from the edge of the wheel to the lip. A 9" wheel, some 12.5mm wider, no longer fits under the lip. The RSS LCAs are designed with long threads and spacers to positively capture a wide variety of shim stacks, even more than 22. Ideally, one would opt for the Tarett Cup or RSS XL variants which have extra length built-in to reduce the number of shims. Alas, I didn't know of the XL version when I bought my RSS LCAs and the cost to upgrade is significant.
 

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Thanks for posting your journal. After sampling a couple sections, I'm going to read it end-to-end to glean what you have learned and compare with my own observations. This is a great idea, and may do a journal myself. I keep all my service info in the aCar app, so know what I did when over the past couple of years, but no real place to coalesce that information with my observations of performance.
 

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I run an Apex SM-10 18x9' ET46 with 255/35/18s and -3 degrees at the track...
A) Did you really mean 255/35!? That is 1.5" shorter that OEM and 1" shorter than anything I've considered. That would certainly solve the tire/fender contact concern I have.
B) I run a Porsche SportTechno 20x8.5" ET57 with 245/35/20s and -3 degrees at the track... *shrug*

This is where I paused the 19x9" ET48 install to pursue reducing track width.
 

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Yep 255/35/18 front and 285/35/18 rear
From the pics, this is obviously a 987. A 987 starts off with a 1" smaller diameter rim on the same profile tire, so this would be the equivalent of running a 40-profile on 18's (or 35-profile on 19's) on a 981, as far as filling out the wheel wells and lowering the ride height.
 

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Yes it's a 987.1 :)


https://support.apexraceparts.com/hc/en-us/articles/360003019474-981-Wheel-Tire-Fitment-Guide

Performance Street/Track or Race Fitment
  • Front: 18x9” ET46 with 245/45-18 tires
    Rear: 18x10” ET36 with 265/45-18 tires
    • Requires at least 2 degrees of front negative camber.
    • 245/40-18 and 275/40-18 tires may also be used but will require at least 1.5 degrees of front negative camber.
    • 255/40-18 and 275/40-18 tires may also be used but will require at least 2.5 degrees of front negative camber.
 

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As someone had already mentioned, you likely won't need to change your thrust arms unless if you want to start playing with the thrust arm length.

Solid thrust pucks would be a good idea to keep everything firm. Adjustable up front so you can change the castor. In the rear, most don't use adjustable as castor adjustment isn't all that crucial. Changing that on the rear will also change things like your wheel base and to some degree roll centers and bump steer. A lot of complexity for not a lot of benefit.

In the front, I would say max out the castor. You need some sort of thrust puck adjustment to do that (or have adjustable thrust arms). You will, however, be limited by the wheel well (rubbing), and not the thrust puck adjustability. Keep in mind that everything affects everything. Ie, if you add, say, 20mm of shims on your front LCA, and you leave the thrust puck on stock position, your wheel might run depending on the ride height. If you add fewer shims, it might not. Wider tires will make that worse. A longer thrust arm will relieve the problem. That said, you can probably get 10-11 degrees of front castor out of a lowered car with extended LCAs and thrust puck adjustment (probably 12 degrees if you don't adjust thrust puck).

A bigger issue is bump steer. I think there's a lot of bump steer built into the stock suspension geometry. I would make an effort to look at that. Doesn't matter how good an alignment or how solid all the bushings are if your toe changes dramatically through out the suspension range.
 

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Not sure about maxing out the castor, as I prefer to keep the caster in the 8 or 8.5 area even with a lowered car. Bump steer was a concern for me when building my Cayman. My install shop questioned me regarding how often I actually felt bumpsteer happening. I have an uphill road that has severe bumps in the middle of some corners. The bumpsteer is noticeable, so from that experience I purchased Elephant adjustable toe links with bumpsteer adjustments. My shop was resistant, but did install them and adjusted the washers to provide accurate bumpsteer adjustments so I do not have rear toe steering in a bumpy track. The solid thrust puck in the Tarett Cup LCA's, which really helps turnin and mid corner throttle response. They also help in the rear preventing rear wiggle during threshold braking. Pefro's TechnoBrace also helps keeping the frame rails in alignment.

The other effect that the solid thurst puck does in the rear is to keep the axel, wheel uprights and tires from moving forward and rear. My shop said that 3 inch of wheel travel is not uncommon in Cayman's with the rubber bearings and rubber thrust puck. I agree fully with this assessment as I purchased a set Tarett GT swaybars. 5 hole f and 4 hole rear adjustability. Had them installed, heard noise from the rear on bumpy back country roads, so later I took a look to see if I could spot any rubbing. The bolt head that attaches the downlink to the swaybar in the softest setting had rubbed a gash into my LCA's to a point where their was possible issues with a crack forming on both sides. Luckily, I had ordered Tarett Cup LCA's to be installed in a couple of weeks. So I did not use my car much and changed the rear swaybar setting to the #3 hole. I then cut off the #4 hole on the sway bar to give it room. Cantrell Motor Sports said that was not necessary as the solid red thrust puck and the solid monoball bearings would take care of the rearward motion of the LCA's preventing the rub.
 

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Try a Pedro's TechnoBrace 2 or a 718 rear frame brace in the rear to control the braking wobble. It's a cheap fix and it keeps the rear subframes in relative alignment during the droop phase of threshold braking.
I can't find any quality photos of Pedro's TechnoBrace2 for the 981. It looks like it ties the frame rails together from the inside, where the inner control arms mount? Does this serve the same purpose as the new 781 bar that ties the two rear antiroll bar mounts together? Is one or the other more effective?
 

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Schnell make a rear brace that looks very good. It mounts a little forward near the suspension attachment points, which is the stiffness target and on the bottom of the OEM stiffness plate away from the PDK transmission. Schnell also make a forward cross brace for the front shock towers that is very effective. If you are reinforcing the rear, you might was well do the front as well, especially if wider wheels and stickier tires are in your future. Google rear frame brace for Cayman 981, you will see many including Pedro's TechnoBrace 2. Take a minute to review the thread in the Cayman/Boxster 981 Competition, thread, when to start struttin by dcharnet, specifically Voyager6's comments in post 2.
 

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Unfortunately "on rails" and "better turn-in" are all subjective as is typically the case with chassis reinforcements. It becomes a question of money vs subjective feel. At $100 to add the Rennline subframe stabilizer to my car it is as near a no-brainer as could be, I suppose. There are numerous people who state that a rear subframe brace addresses the braking squirm, making it even more palatable.

As I said elsewhere, it is all part of a system. At some point, the increased performance of some parts (driver included) may exceed the performance of others and it is time for a strategic upgrade.
 
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