TPC or Tarrett toe links?
#16
Their principle is sound, but I agree, we need more empirical data that is apples to apples.
#17
GT3 player par excellence
Lifetime Rennlist
Member
Lifetime Rennlist
Member
This. I will buy the first aftermarket altered geometry toe link that has data showing a significant reduction in dynamic toe, whether made by TPC or a competitor. No data exists yet. I have Tarett links for now (just for camber).
Draw it up! Should be easy in something like solidworks, no?
Draw it up! Should be easy in something like solidworks, no?
Jury is still out on if the offset TPC link is really doing anything. Geometrically it is not obvious that it has any significant impact, and TPC won't share any real toe curve data over suspension compression to prove it.
I'm on the fringe of just drawing a suspension model myself to show the theoretical toe vs offset impact over compression.
I'm on the fringe of just drawing a suspension model myself to show the theoretical toe vs offset impact over compression.
finally there's theoretical benefit and actual benefit. most mortals cannot benefit much from theoretical benefit.
#18
Rennlist Member
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.
#19
Rennlist Member
My guess is TPC doesn't actually have the quantitative toe data to share. Sharing the data would only increase sales and would have no impact on enabling copycats. I could see them doing some trial and error based on some assumptions and being convinced they could feel the differences on track with the offset. Not enough data for me, but I welcome the information and discussion should it become available.
Competition ... well they can buy a set scan it and it's good to go.
#20
Rennlist Member
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?
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?
#21
Drifting
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?
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?
#22
Premium Sponsor
Rennlist
Site Sponsor
Rennlist
Site Sponsor
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.
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.
__________________
PCA National Instructor
TPC Racing stats:
2023 Porsche Sprint Challenge 992 Cup Am Champion
2023 Porsche Sprint Challenge GT4 Pro-Am Team Champion
2022 Porsche Sprint Challenge 992 Cup & 991 Cup Champion
2020 IMSA GT3 Cup Challenge 2nd Championship
2018 IMSA GT3 Cup Challenge 2nd Championship
2016 IMSA GT3 Cup Challenge Champion
2013 IMSA GT3 Cup Challenge Champion
2006 Rolex-24 @ Daytona GT Champion
2004 Grand-Am SGS Class Champion
PCA National Instructor
TPC Racing stats:
2023 Porsche Sprint Challenge 992 Cup Am Champion
2023 Porsche Sprint Challenge GT4 Pro-Am Team Champion
2022 Porsche Sprint Challenge 992 Cup & 991 Cup Champion
2020 IMSA GT3 Cup Challenge 2nd Championship
2018 IMSA GT3 Cup Challenge 2nd Championship
2016 IMSA GT3 Cup Challenge Champion
2013 IMSA GT3 Cup Challenge Champion
2006 Rolex-24 @ Daytona GT Champion
2004 Grand-Am SGS Class Champion
#23
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.
#24
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.
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.
#25
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.
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.
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.
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.
#27
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.
#28
Instructor
Join Date: Oct 2015
Location: New York City area
Posts: 197
Likes: 0
Received 0 Likes
on
0 Posts