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Discussion Starter #1
Hi all,

I've been reading lots of mixed opinions on track alignment settings and am hoping for some additional ideas, particularly camber settings. The car is street driven but i also compete in a time trial series with it so performance is the priority. I'll take tire temps over the course of this season to fine tune things, but i'm hoping for a solid baseline. Thanks!

981 Cayman S
x73 suspension
GT3 front LCAs
RE71Rs
 

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My Spyder without LCA was:
Front -1.7 camber +1/16 toe 8.7 caster
Rear -2.2 camber +1/8 toe
I'm sure you can get more camber with LCA. I probably wouldn't go more than -2.5 front camber since it's mostly street driven.
 
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The RE71R's soft rubber compound, especially in front need more camber, since you have the GT3 LCA's, add that additional camber shims to -2.6 f and -2.1 (OEM max rear). If you need more rear camber, determined by your temp probe, you can have your shop install the Elephant Eccentric rear adjustable camber bushings to give you -2.5 camber in the rear as well. If you keep your toe in front close to 0 and rear toe in to 12 minutes, your tire wear on the inside shoulders will be at a minimum compared to the wear across the face of the RE71R's.

I would swap the tires on the rims after 1/2 of the season if you are in a rain free area. Even with this camber, the outside shoulders are going to get beat up depending on your driving style. A frame stiffener in the rear would help keep the frame rails in line during threshold braking (not changing the toe or camber excessively during droop).

After all of this work, you are having balance issues, understeer vs oversteer, use wheel spacers in the rear to reduce oversteer and a small spacer in front to reduce understeer.
 
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Discussion Starter #5
Great, thanks. Good tip on the elephant eccentric rubber bushings. Those are perfect because i need to take classing points if i deviate from rubber (ie no spherical bearings) so i'm avoiding that. I found i only have 2, 6, and 16mm shims. I think i'll install the 2s and 6s to get 8mm and see where that gets me. Hopefully around 2.6-2.8 with the strut mounts full in.
 

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Tarett makes a full range of GT3 style LCA shims. I would suggest at least 12 mm of shims and with -1.5 from the top slots to give you a total of -2.7. Just so you know, those Elephant Eccentric bushings wear faster than the Tarett Cup LCA's or other aftermarket control arms bearing. They start making popping noises according to lovetoturn, a 981 owner who had to replace two of these beauties and then have an alignments as well after each failure. Check out his entries/threads from a couple years ago before you do this. Maybe Elephant has got this issue fixed by now. You can find his thread in Porsche Wheels and Tires, Wheels and Tires that worked, starting on page 11. He also mentioned these eccentric bushings in changing PASM to X-73.
 

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Correct me if I'm wrong but I believe that rear camber is limited by the ability to keep toe in check. At -2.5* you probably need toe links too. And if you kick the lower front out too much you need to keep an eye on caster. I "learned" this in the process of shopping for GT4s and track necessities.
 

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It is possible that adjustable rear toe links maybe necessary to get your rear toe in to 12 minutes, but usually this issue happens with a lowered car, below the X-73 ride height. I did not see any mention of aftermarket H&R springs, Swift or others, so until you do this or coilovers, then most likely your alignment shop should be able to complete the job without these links. I did need the Elephant rear toe links due to coilovers and a corner balance which reduced the ride height well below 30mm drop.

Caster in the front could be an issue, but with GT3 LCA's in front, there is a center thrust puck with adjustments by rotating the puck for castor and wheelbase.
 

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Apex1

I have the KW-V3's on my 981CS and the caster is +/- at 8.5 (perhaps even higher..) what would be an ideal caster setting?

Perhaps I need to get the Tarett adjustable pucks for the control arms as I don't have the GT3 LCA's, thank you!
 

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The ideal front castor is 7.8, If you can get this settings with the camber you desire, your car will steer without any effort. Some like a little more castor to get a little weight/resistance in the steering wheel going over 120 mph.

You can modify your existing LCA's with the Tarett Red center thrust puck, for both f&r. This single modification helps tighten up your turnin and front/rear motion of the LCA. If you feel the need from more camber to help prevent outside tire shoulder scrub, then I would recommend the Tarett Cup LCA's which uses the Red thrust puck.

The Tarett Cup LCA's work very well, especially with coilovers, higher spring rate/swaybar rates. The Red center thrust puck will do the job of caster/wheelbase adjustments without needing adjustable thrust arms. The Cup LCA's also have a more robust outside monoball with stud that attaches to the upright. This upgraded outer monoball takes all the weight and motion of the wheel to the LCA's, so it's important to have a smooth delivery of that motion during turnin and through the bumps, helping keep the wheel/tire attached to the ground.

I would suggest modifying both front and rear with the Cups as both ends will benefit from this unique part. Then bring on the camber to help keep the outside shoulders of your race tires in place with the internal camber shims.
 

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Discussion Starter #11
Tarett makes a full range of GT3 style LCA shims. I would suggest at least 12 mm of shims and with -1.5 from the top slots to give you a total of -2.7. Just so you know, those Elephant Eccentric bushings wear faster than the Tarett Cup LCA's or other aftermarket control arms bearing. They start making popping noises according to lovetoturn, a 981 owner who had to replace two of these beauties and then have an alignments as well after each failure. Check out his entries/threads from a couple years ago before you do this. Maybe Elephant has got this issue fixed by now. You can find his thread in Porsche Wheels and Tires, Wheels and Tires that worked, starting on page 11. He also mentioned these eccentric bushings in changing PASM to X-73.
Yeh, I'm a little worried i'll come up short on front camber with only 8mm worth of shims. I drop off the car tonight at the alignment shop so we'll find out tomorrow.

In the back i'm also concerned about how much neg camber i can get while mainting toe in. Right now i have set the rear LCA eccentric to max neg camber and the rear toe arm to max length and the rear wheels look toed out. That means that the max LCA length isn't useable with stock toe arm adjustment range and i'll have to dial out neg camber to get my toe in. Or lengthen my toe arms.

For classing reasons i'd really like to stick with rubber bushing interfaces which cost me no points. The Elephant rubber eccentric bushings look great, but i need to do more research. I tried to find the posts you mentioned above but I could not. I read through the whole Wheel/Tire Fitment thread. I'll look again.

I'll report on how this setup pans out tomorrow.
 

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As your librarian, here is part of the reference source; 981 Cayman & Boxster Competition; Tire size for 19 in wheels- Sept 11,2017 by Okindao, Post #10. You can click on his aviator to find parts of other postings, I have not found the reference he made about the eccentric's going bad, but its around that time.


lovetoturn

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#10 Jun 16, 2018 (Edited)
No spacers. The rear has 6mm of additional track via eccentric monoballs on each side plus the extra 10mm built into the offset of the OZ rear wheels, so 16mm + 16mm total in the rear. I would be careful adding a spacer to rear since it would put you at least 15 mm off the original OEM suspension geometry. The front OZ wheels add 4mm of additional track, but the real difference on my car is that with the GT3 LCAs in the front it has 13mm extra track built into the suspension and not just by adding spacers, so front is 17mm + 17mm total additional track width. On a stock car I would add 5mm or 7mm spacers and longer bolts to the front of the car and call it a day. It won't be quite as wide as mine, but will cost much less than with all of the suspension modifications, and it will be balanced with 9mm or 11mm more track on each front wheel with 10mm more track on each back wheel. I have run these OZ Leggera wheels hard at the track, seen the tires slip on the wheels under extreme braking and or cornering, been through numerous of track tires, and not had any problems at all. Highly recommended and affordable wheel upgrade for any Cayman or Boxster.

Here are a few recent photos of the car in action at COTA at this springs Club Race / HPDE. I passed numerous GT4s, GT3s, corvettes, the white and orange race car, and even a GT3 RS. A properly set up and driven mid engined Cayman is a very very capable car.
 
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Discussion Starter #13
I got the car back and ended up with -2.5 up front and -2.15 in back. That's with 8mm shims in the GT3 LCAs. The rear camber was limited by the stock toe link range.

I got 8deg (well 7.8 on one side and 8.5 on the other) castor using the eccentric holes in the GT3 LCA oriented toward the front of the car. I had 220lb of driver weight in the drivers seat which put things a little asymmetric.
 

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Drivers weight makes the alignment kind of lopsided. That's the point of corner balancing with coilovers. The big deal is how does turnin work on both sides, mid corner throttlesteer and exit speed? Understeer out of the corners or oversteer with throttle on? Also, does it brake straight with threshold braking, no wiggles in the back? What are the tire surface temps across the face? Hopefully the camber will allow your RE71R a few more track days without the outside shoulder cords showing. Remember, you can flip the tires on the wheels to get the inside shoulders some wear when they will be on the outside on the second half of the year.
 

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The ideal front castor is 7.8, If you can get this settings with the camber you desire, your car will steer without any effort. Some like a little more castor to get a little weight/resistance in the steering wheel going over 120 mph.

You can modify your existing LCA's with the Tarett Red center thrust puck, for both f&r. This single modification helps tighten up your turnin and front/rear motion of the LCA. If you feel the need from more camber to help prevent outside tire shoulder scrub, then I would recommend the Tarett Cup LCA's which uses the Red thrust puck.

The Tarett Cup LCA's work very well, especially with coilovers, higher spring rate/swaybar rates. The Red center thrust puck will do the job of caster/wheelbase adjustments without needing adjustable thrust arms. The Cup LCA's also have a more robust outside monoball with stud that attaches to the upright. This upgraded outer monoball takes all the weight and motion of the wheel to the LCA's, so it's important to have a smooth delivery of that motion during turnin and through the bumps, helping keep the wheel/tire attached to the ground.

I would suggest modifying both front and rear with the Cups as both ends will benefit from this unique part. Then bring on the camber to help keep the outside shoulders of your race tires in place with the internal camber shims.
Hello Apex1,

Sorry for the late reply but was on a business trip and before replying I wanted to confirm the values of my alignment sheet (on the glove compartment) and my car has indeed a 8.7 front castor.. this is almost a full degree more than the 7.8 figure you mentioned (could this be the reason why the steering feels a bit heavy..?)

Ideally I would like to get the front and rear Tarett Cup LCA's as these already have the trust center puck, but they are kind of pricey, so for the time being the adjustable Red center pucks will have to do it. Is the castor on the rear axle also set to 7.8? Thanks again!

Regards, Gilles
 

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No caster on the rear, just wheelbase adjustments to keep the axle straight. That is important as the old LCA's rubber coated center thrust puck allows the movement of the wheels forward and aft more than 2 inches which also impacts the toe. The toe is the key to the rear in keeping it within its allowed motion. You are trying to not have any toe out during the arc of droop/compression. If that happens then you are allowing some rear steer and need a bump steer adjustment on the rear toe link. There are articles on this subject on this site.

You should feel the difference of the solid red thrust puck in both front and the rear. In front turnin should be more accurate and in the rear, throttle steer more direct without slight movement from toe steer.
 

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Discussion Starter #17 (Edited)
I ran three sessions (a Track Night in America) on the -2.5f/-2.2r camber settings and the car felt pretty good, but i still had a lot of outside edge tire wear.

I ran the SCCA TTNT this past weekend and for classing reasons put back the stock front LCAs and ran -1.6 front and rear. The car felt really good. There are many variables, including being at a different track, lower hot tire pressures (32psi hot down from 36psi), and a little more time with the car, but i can't help think that the car felt pretty spot on. I wonder if having lesser but front/rear balanced camber was better than more camber, but less balanced front/rear. I don't really think i can draw a conclusion with so many variables.

Today i'm swapping back on the GT3 control arms and i'm debating how much front camber to dial in. Keep it the same -2.5 as last time? Maybe more to improve tier wear? Maybe less to better balance? I can't increase the rear camber unfortunately.
 

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You can add rear LCA's like in front, but you will need adjustable toe links as well. Many just stay with the less rear camber due to cost? If you really are intent on tracking the car, you may need -2.8 f and-2.5 r to prevent the outside shoulders from additional wear due to tire roll over. The additional camber will allow your outside tire face to be square with the track surface in corners. The inner wheel/tire will actually have less tire face contacting the track surface, especially when you experience body roll. That is one reason for the anti roll bars, to keep in inside tire working as much as your layout permits. The other reason for swaybars is to balance the roll f to r.

Where many track users complain about additional camber is front braking becoming skittish as both front tires will not have their full surface on the track, mostly riding on the inner 3/4 of the tire. Same with the rear, which can cause snap oversteer as again the full tire face on the inside is not contacting the track as in trailbraking.
 

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Lower hot pressures is a big difference
What tires are they ?
Even camber front/ rear shouldn’t help
 

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Discussion Starter #20
RE71Rs. Yeh, i'm trying to avoid rear toe links because classing rules/points cost. Might be worth it in the end. Now that that the time trial season is starting back up I think i'll start checkign tire temps and attempt to dial this camber in empirically.

Yeh, I get all the general stuff. I've been tracking and racing cars for about 16yrs. :) This is my first Porsche though and i'm having trouble coming up with a consensus on alignment. Sounds like -2.8/-2.5 is the goal, though. I'll hit that up front, max out the rear, and if things feel or measure weird in the back i'll take the class point for the rear toe links.

Also, what do you guys know about reinstalling lower control arms? A buddy of mine said that its not recommended because the tapered pin on the ball joint could fatigue? I'll be installing my GT3 arms for the second time later today. shrug

Thanks!
 
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