Tom@TPC Racing

Thanks for following. Cheers.

onefstm

Tom, could you post a picture of your toe arm installed? Is one of the goals to make it more parallel with the ground? Here is a pic of my factory toe arm on my lowered GT3. Would this be considered 9:00?

Thanks

Tom@TPC Racing

The photo you have posted shows the lower control arm, not the toe link. The eccentric dial(adjuster) of the stock rear toe link is usually visually obstructed by the rear sway bar. In your photo, the eccentric dial of the lower control arm is turned as such that the hexagon bolt head is in the 4 o'clock position. I assume the eccentric dial is turned to this position in order to reduce negative camber since you car's ride height is lowered, which is fine. The toe link eccentric dial is not shown in your photo.

It is not possible to have the lower control arm parallel to the ground on our GT3(including RS) street cars with decent ride height. If you raise the rear ride height to that of a base model 997 Carrera then the lower control arm will be near parallel. The 997 Cup cars and RSR's have different subframes and uprights which places the lower control arm in a near parallel position at their very low ride height. The idea of parallel control arm is for reducing geometry change as the suspension travels at an arch. When the arm is parallel at the set ride height, the geometry change is usually at minimum as the suspension travels up/down throughout the usable stroke of the shock. This is because the travel begins in the middle of the arch. Whenever I work with someone who doesn't have in depth knowledge on a particular model of car, the usual notion is always start with arm parallel for the reason I stated. Okay I get it, if you don't know, you got to start somewhere, right? Hopefully the concept is understood and not just because someone said parallel is good. In the case of our GT3/2/RS street cars(and many other cars), parallel control arm is not possible with stock subframes and stock uprights at a desirable ride height, so the only thing we can do to minimize geometry change(to improve grip and stability) is to install adjustable rear toe links. Which is the all important reason why you need toe links with bumpsteer adjustability.

To sum things up, not being parallel is not as ideal as being parallel when you actually have a choice. But over the year we have been racing and developing these cars so much that we can make it as good, if not better, than other cars with parallel arms. Today's plug: TPC Racing adjustable rear toe links will get you there by design of the part and by our tech support.

Side note: 996-series cars including Cup cars have more severe angle on the lower control arms than 997 street cars. With years of racing and development we(privateer teams) have sorted them out pretty good.

Another side note: I am being overly **** on setups here. On none-pro racing cars one can get away with a lot of f'ups and not even notice the affects because Porsche cars have a very good platform derived from motorsports. But I still work on my customers cars as if its a pro car.

Here is a photo that show both the lower control arm and toe link eccentric dials, both at 6 o'clock position.

Tom@TPC Racing

Here's another photo. This photo has better view of the eccentrics with bolt head at 6 o'clock with the rear sway bar removed. This is actually the photo of my car from back in March. I did ended up tweaking the camber dial just a little bit and changed the outter shim arrangement of the TPC adjustable toe link to achieve less than 0.5mm of toe deviation(bumpsteer) at 1.5 inch of suspension travel.

GT2rainge

This an awesome thread congratulations,really informative with plenty of great information.
It's been great to see your car evolve from when you got it to now.
I hope you don't mind me asking a couple of questions with regards rear suspension set up.
It's about bump steer and what to adjust when set it up to minimise it.
I have adjustable castor pucks and rss toe arm links, but I'm not sure how best to adjust theses when setting it up, is it best to use the spacers on the upright end of the toe link or by rotating the castor puck?
Also I've seen in the 997 cup car PDF that it shows an angle of how to set the castor pucks but it doesn't say whether this is a base setting or the optimum angle of how to have this set, if you could shed some light on this I'd massively appreciate it.
I've searched and searched but not found any info on this subject.

Tom@TPC Racing

Thank you for following my thread and for your kind words.

I will tell you the answer if you buy TPC toe links. It's customer privilege information. Just kidding. But kidding aside, the company who made your toe links should answer that question since they designed it and I cannot speak for their design.

If you were using TPC toe links...wink wink...you'll need a bumpsteer test equipment and go through the exercise of testing every shim combination on the outter pin that goes into the upright until you have found the least toe deviation for a given ride height and for a given position of the puck. My approach is the set the puck first and then play with the outter pin shims. It takes A LOT of time to keep doing this in circle(puck, pin, then puck, pin, and again). Or you could just copy the effort of someone who's done this on the same car with the same parts.

The puck position does influence bumpsteer. Different generation of Cup cars specifies different positioning. And racing series also send out technical bulletins to race teams as to the regulation positioning of the pucks for different races. I think they do this to regulate lap times of the class leading cars. Every time we get one of those tech bulletins we start from square one. By changing the castor via puck position the car also can transform for loose to tight and vice versa. In some racing series, the teams have more liberty on adjusting the pucks, in which case the more advanced teams use this to their advantage by finding a position that favor that particular track.

There are a lot of variables to determine the best puck positioning for one specific car and it will take a lot of setup time and track time to find out. I mean at some point you are chasing 0.1 second of time with a pro driver. If you're not in to experimenting with all that then my suggestion would be either put the hole in the middle(stock location) or mimic the Cup car that's closest to your car.

I hope I have shed some light on the pucks without confusing you more.

PS- Some people like to use adjustable dog bones to change camber, that'll introduce another variable especially when the front bone is different length than the rear bone. We have discussed this topic before a few pages back.

onefstm

I'll call tomorrow and buy the TPC toe links as long as you share your configuration I do not want to reinvent the wheel and would be thrilled to copy your setup.

Thanks for all the insight! I'm having so much funs with these GT3 mods.

Tom@TPC Racing

Sweet! Of course I will.


That's the spirit! I've been hot rodding cars since I was a teen and still loving it.

Spyerx

This is a pretty important point. I've seen my shop doing their alignments and it's a very, very time consuming process, back and forth, adjust, check, adjust, check everything again. Not all the inputs and changes are independent of each other and there is a balance to get to. You can't just bring one of these with all the adjustable parts to an 'alignment guy' and expect it to be right/perfect. Its also why most shops will share the basic details but if you look really closely there are a LOT of subtle details in the 'how' of the setups that differ quite a bit from just setting camber/toe/ride height. An example you've shown is the pivot point of the lower control are based on the eccentric bolt, or the placement of the lower camber puck and length of the rsr arm to control the arc angle of the control arm movement. There is a massive amount of geometry here. I've also seen the result of other shop's efforts on suspension that look very much like what you posted here. Sure it measures on the machine.... but car is not right.

I love looking at these pics you've posted and seeing all these nuances and hearing your story behind the changes. Great learning tool.

Tom@TPC Racing

Very well said, Sir. I think most people look at the rear suspension as single dimensional but it is indeed multi-dimensional.

Here's a general sequence to give the readers an idea of what's involve to do it to "full force" on an unfamiliar chassis. Often the sequence is repeated again and again to get the right numbers to start with. Then the car may or may not be competitive on track. And we make changes from there based on pro driver feedback and data. Some of the info here is applicable only to early 911's but you get the point.

Tom@TPC Racing

Our cars definitely have better cooling for the inboard pads! All four corners are the same after 5 track days. I know some people are against flipping the pads but not me. Perhaps the higher temp of the outboard is the reason for some pads delaminating. I don't think there's anything that can be done to make the temps more even. Any ideas?

chardonet

Deleted.

bmwtye

Just wanted to see if anyone else has impressions on the DSC Box and 3 axis accelerometer.

Ur20v

turbo fan wheels like they used on the rally deltas etc would do the job of cooling the out board pads...



935 Turbo Fan wheel

Tom@TPC Racing