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Old 02-15-2012, 02:01 PM   #1
Infamous Performance
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Default New Forged Roll Center Bump Steer Kit From GTSpec! Fits all WRX and LGT!



We are proud to announce an all new product release from GTSpec



GTSPEC Roll Center/Bump Steer kit is a must on all lowered vehicles. Lowered vehicles that are not equipped with this kit are prone to poor alignment geometry. With the GTSPEC Roll Center/Bump Steer kit install, correct alignment geometry is regained and stress on the suspension components will be reduced. Our roll center kit will also produce a reduction in bump steer, re-alignment of camber/caster, increase stability, improvement in steering feel and response, and reduction in under steer. While other kits on the market are cast, the GTSPEC Roll Center/Bump kit is FORGED; known to last under harsh driving conditions.

MSRP $399

$359 delivered to Con US.

http://www.infamousperformance.net/s...-Joints/Detail

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Last edited by Infamous Performance; 02-17-2012 at 06:22 PM.
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Old 02-15-2012, 02:06 PM   #2
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Pix of the GTSpec kit vs. the Whiteline.

Pix of our install. 08 LGT with Epic Springs, Hotchkis sways and Kartboy links. Car spent 2 winters in NYC. Took 6 hours with air hammers to get the OEM ball joints out. Lol.

First impressions, makes steering input more defined than the Whiteline kit. Steering is much more responsive.

Alignment changes dramatically (2.6deg) after install.



















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Old 02-15-2012, 02:07 PM   #3
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Old 02-17-2012, 02:48 PM   #4
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JDM companies making similar products sold in Japan include:
SYMS Racing Team
Zero Sports
HKS
Pleasure
and more.
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Old 02-17-2012, 05:26 PM   #5
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Can you explain the 2.6* change in alignment? Was that right after the install, before camber and toe were adjusted, or was that post-realignment #s? And is that change for camber, toe, or caster?

I've been trying to do a bit of digging to find the difference between the two kits, as in whether one corrects for lower suspension than the other, etc.
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Old 02-17-2012, 06:20 PM   #6
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GTspec corrects for lower suspension. At least 25.4mm (1") drop before these will work.

Alignment change was after install, but before alignment done. Car in alignment prior to install. Tie rods put back on in exact same length. Toe changed 2.6 deg on each side with new kit installed.
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Old 02-19-2012, 01:49 AM   #7
AND0
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Default Tie Rod Design is Wrong

The design of the tie rods is flawed.

Putting a drop or dog leg in the tie rod does not change the steering geometry. The tie rod swings in an arc between the two articulating joints, the one in the rack and the one in the tie rod. Proper bump steer correction will change the space between the steering arm on the knuckle and the ball in the tie rod. This can be seen in the Whiteline kit. The tapered bolt that attaches to the steering arm is longer, spacing the joint downwards.

The GTSpec tie rods will have the exact same geometry as the stock arms and bump steer will change significantly from stock. I have not measured bump steer on a stock geometry Impreza, but I have read that there is very little, thus installing the GTSpec ball joints with either stock or the included "dropped" tie rods will have a large negative impact on bump steer. This is a pretty rookie error on their part and really doesn't inspire confidence in their engineering skills.
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Old 02-19-2012, 12:49 PM   #8
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The GTSpec tie rods have a longer tapered bolt, like the Whitelines. They have the longer tapered bolt and the "drop". Might be misleading in the pix I took, but that is because the GTSpec castle nut is much larger.

In order for a MacPherson strut suspension to have no bump steer, the tie rods must lie in line with the lower control arm with the inner tie rod end in plane with the inner pivot of the control arm



I will contact GTSpec and ask for some more specifics on the tie rod and ends used.
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Old 02-19-2012, 01:38 PM   #9
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so a 2.5"-3" drop/flush sitting cars, is a perfect canidate for these??? its a 2011 wrx, these where a stretched tire, now im sitting on a 265 wide tire....



letting the haters be my motivators
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Old 02-19-2012, 04:05 PM   #10
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Quote:
Originally Posted by Infamous Performance View Post
The GTSpec tie rods have a longer tapered bolt, like the Whitelines. They have the longer tapered bolt and the "drop". Might be misleading in the pix I took, but that is because the GTSpec castle nut is much larger.

In order for a MacPherson strut suspension to have no bump steer, the tie rods must lie in line with the lower control arm with the inner tie rod end in plane with the inner pivot of the control arm

Thank you for responding in a positive manner, and I am sorry to basically be bashing this product, which could have potentially filled a big gap in the market. Given that the WL product makes only a very small correction, and the 6Gun kit is unavailable? unreliable?

That the tie rod and the control arm need to lie in same plane to minimize bump steer is inexact. The tie rod and the control arm need to MOVE in the same plane. Both the tie rod and the control arm move in an arc that is inscribed by a line that drawn from the inner mount (either joint in the steering rack for the tie rod, or the bolt through the bushings in the control arm) and the articulating outer mount (the center of the ball joint for both). This line does not follow the shape of the arm. The control arm or the tie rod could be any practical shape, but they will always move in relation to their mounting points. The "drop" in the tie rod does not change this basic geometry.
That the kit spaces up the tapered spindle on the tie rod, and thus moves the mount, does start to correct the bump steer, but it clearly does not go anywhere near the full inch that would be required. In fact the longer it is the more susceptible to bending and breakage. The only way to use these extended ball joints would be to change to a race style heim jointed end in place of the tie rod and to drill through the knuckle to eliminate taper and use a much larger high strength bolt which could be spaced appropriately to minimize bump steer. This may have been the limiting factor in the original WL kit. They couldn't make an OEM style tie rod any longer without compromising strength overly much.
It is easy to write anything on the internet. Best thing would be to just measure bump steer. It's a bit tedious, but certainly do able by anyone who can measure toe. Remove or unload the spring, and cycle the wheel through it's travel and measure toe. A bump steer curve is created.
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Old 02-20-2012, 11:32 AM   #11
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Measuring bump steer in a shop without the expensive tools can be done. It is tedious. problem is all the cars that the kit fits. Wont be able to test on that many applications. Not myself at least.

I installed the kit on a 08 LGT. So far it is a vast improvement over stock. Not so much in bump steer (that was never really an issue and honestly I cant tell if it is better, I am not on a track where it would really show) but in steering response. I have yet ot notice a negative effect (not that there could not be one).

I have seen heim joint tie rod ends with ultra long bolts (no taper), I have also seen custom knuckles. Alas, these are all only available in limited supply in Japan.

I sent an email to GTSPec requesting some graphical data and more tech data. I will post up with whatever they respond. I have nothing to hide.

My description might have been "lacking", but the pic clearly shows movement in the same arc. I think someone is nitpicking, Lol.
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Old 03-20-2012, 11:25 AM   #12
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Quote:
Originally Posted by AND0 View Post
The design of the tie rods is flawed.

Putting a drop or dog leg in the tie rod does not change the steering geometry. The tie rod swings in an arc between the two articulating joints, the one in the rack and the one in the tie rod. Proper bump steer correction will change the space between the steering arm on the knuckle and the ball in the tie rod. This can be seen in the Whiteline kit. The tapered bolt that attaches to the steering arm is longer, spacing the joint downwards.

The GTSpec tie rods will have the exact same geometry as the stock arms and bump steer will change significantly from stock. I have not measured bump steer on a stock geometry Impreza, but I have read that there is very little, thus installing the GTSpec ball joints with either stock or the included "dropped" tie rods will have a large negative impact on bump steer. This is a pretty rookie error on their part and really doesn't inspire confidence in their engineering skills.
I agree. This kit will have lots of bump steer. Can't believe they would miss that in their design.
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Old 03-21-2012, 09:38 AM   #13
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It's true that the only thing that matters for bump steer is the virtual line connecting the joints/pivots, but it's also important that those joints stay within their range of articulation to prevent binding or breakage. So although the dog leg doesn't change the steering geometry, it does move the inner joint back toward the stock angular position and therefore resets some of the joint articulation angle range..

Last edited by fabrik8; 03-21-2012 at 09:44 AM.
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Old 03-27-2012, 06:53 PM   #14
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Bump for possible response from GTSPec.
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Old 03-28-2012, 10:30 AM   #15
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Still waiting. Have sent a few follow up emails.
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