ShakeNBake

Their principle is sound, but I agree, we need more empirical data that is apples to apples.

mooty

===> bn mech33 and keith, the PhD brains will have it plotted no prob., can't wait to see it

even if they dont show data, one can buy the product and 3d scan it. rapid prototype it then send over seas to make them fast. before you critize oversea manufacturing, the asian can make these in way way higher tolerance than western mkt, they dont chose not to due to $. but to not release data for fear of being copied makes no sense.

if you just want camber, i can assure you with tarrett and any other aftermkt arms, you get easily -3.5 with no caster issues.

finally there's theoretical benefit and actual benefit. most mortals cannot benefit much from theoretical benefit.

Alan C.

I'm sorry but I didn't imply the part being copied and produced in Asia. Mike doesn't need to release any form of intellectual property for the part to be copied. It can, as stated, simply be scanned. And if Mike developed the part by seat of the pants testing and it works then good for Mike.

doba_s

I agree. Showing data will make your product stronger.

Competition ... well they can buy a set scan it and it's good to go.

Spyerx

FWIW the Tarett toe links they're selling are ERP (look at the part number). ERP are made locally here in Socal by Cary Eisenlohr. He VERY much knows what he's doing. Extremely high quality.

What I'm trying to understand about the TPC part, so they bumped the car to measure the toe change over the suspension swing and found the ideal spacing and build a bushing for that?

jphughan

The toe links that Tarett sells individually and just calls "Toe Links" are made by ERP. The "Rear Toe Control Arms", sold as a pair, are made by Tarett. At least according to someone from Tarett who just called me to answer another question I had about them.

Tom@TPC Racing

Tough crowd... I assure you all that I have seen my boss, Michael Levitas, installed different design toe links, align, bump steer test and then track test our shop's GT4 over and over until he was satisfied and then he brought in Randy Pobst to confirm. He wrote the numbers down in his secret spiral notebook that we don't get to see. He shares the same passion in achieving the best result as everyone of you here with type-A personality. Certain things he doesn't want to disclose as a race team owner and engineer. We don't just sell car parts, we are passionate about innovations and making improvements. TPC GT4 rear toe links cost less than a set of track brake pads. To those who believe in us, if the product sucks I will shave my head run down use US Route 1 and never post on rennlist again!

There's another thread today sort of along the same line... here's my response from that thread-

For what its worth, I am writing this post as unbiased as I possibly can. There are a number of rear toe links options available on the market for the GT4 from different companies. These companies have been designing/making/marketing/selling/supporting Porsche suspension components for a long time. I work for one of these companies, and I have respect for the other companies as I know how much work it takes to go from an idea to a finished product and then provide support to each user. Back to the toe links- Any of these links will provide the necessary range of adjustment for static toe with increased rear negative camber. The reality is if the car's is not experiencing rear wiggle caused by the rear lifting during braking then any of these links will do the job just the same. And if the wiggle doesn't bother the driver enough then any of these links will do.


What is happening when the front dives/rear lifts during hard braking is the rear toe goes outward. How much toe outward depending on the amount the rear suspension is lifted from the static ride height. For example, if we have static rear toe setting of only 1.0mm of toe-in at factory ride height, with 25mm of peak rear suspension lift during hard braking, at this moment the rear toe is no longer toe'd in, it will be toe'd out. This is commonly refer to bump steer or toe steer(if you don't know what bump steer or toe steer is you will find the info by doing a google search). The result of this momentary rear toe-out during braking is corner entry oversteer.

Race shops and savvy enthusiasts have different approaches to prevents this corner entry oversteer; more rear static rear toe-in can be dialed in to anticipate for the amount momentary toe out, use stiffer springs to reduce rate of movement and total movement, use DSC module to achieve same as stiffer springs, use stickier tires to increase grip, use higher preload and decel ramp in differential to clam the wiggle, or use rear toe links with offset bushings to fix the problem at the root rather than treating the problem with the other approaches or a combination of the above(some of the above have side effects so instead do doing a lot of one thing, a combination of smaller amount of different things is usually better). Again, that is "IF" the car/driver is experiencing the corner entry oversteer. If not, then any adjustable rear toe links will achieve the range of adjustment necessary for increased rear camber.

One thing that I will guarantee is that offset bushings will significantly decrease the amount of bumpsteer when the static ride height is at/or near factory spec. Whether or not every car/driver will benefit from this feature depends on the rest of the setup of the car and the amount of braking and the tire grip. We felt the improvement on our GT4- we can drive the car deeper into brake zones with more rear stability.

In summary, I don't think there is a best set of adjustable rear toe links for everyone. But there is a best set on the market to match the setup approach for the each's car and to meet other criteria of the buyer such as ease of adjustability, material of construction, source of the spherical rod ends, availability for spare replacement parts, level of tech support, and price point.

Mech33

Great! Please share some data to back up these claims (if you are willing). Personally, I don't trust "you can feel it" when it comes to car mods.

PLC

I'm also a big fan of data. While I don't have GT4 dimensions, I can at least run a generic analysis on different toe link attachment points. Standard on the right, offset bushing on the left.



For the case I ran, a 1 inch inner position change from the offset bushing (probably more than the actual change) causes no more than 1-2% difference in toe from the standard bushing. That 1-2% is a slightly flatter curve with less toe out under suspension travel, so it is in the right direction, but probably not enough on its own to cause a significant reduction in oversteer.


(wheel travel in mm)


Obviously there may be compounding effects, so I'd be very curious to hear suggestions or see other data.

Mech33

Nice approach. This type of result is what I would expect from such a suspension geometry (a small offset creating a egligible effect on dynamic toe).

Do you have access to a GT4? If not I could take some measurements on mine to update the dimensions of your model to get toe changes specific to the exact GT4 rear suspension.

Bill Lehman

Looking at the TPC photos of the toe link, I would estimate that the offset is much closer to 3/8" than 1".

PLC

I should be able to measure on a GT4 next weekend. If you're interested in a better simulation sooner than that, I'm happy to re-run it any time with provided measurements.

After a more detailed look, I'd be inclined to agree - 25 mm was just a nice number that made a visible difference in the geometry. I'll definitely update that when I improve the rest of the dimensions.

rraustin

Just measured the TPC offset links that are sitting in a box waiting to be installed and the offset is 0.475" greater then the non-offset versions.

ML///

Will either of these toe links work with 19" wheels?

Yargk

Awesome, thanks! This is why rennlist is so great!!!!