Has Anyone Converted to a Short Front Spindle?
Thread Starter
Joined: Sep 2004
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From: Hou. TX.
I decided to find a salvage yard with a C5 in it and go and measure it myself. Here's all 4 spindles.
As I suspected, there's not much difference in the sizing between the C5 and late C4 spindles. Balljoint to balljoint is the same 13.5" and both have roughly the same hub height. Note the balljoint mounted into the C5 spindle. The advantage of that is more wheel clearance at lock.
Note: The late C4 spindle is the only one I didn't personally measure the hub height of. I found that 5" spec online.
As I suspected, there's not much difference in the sizing between the C5 and late C4 spindles. Balljoint to balljoint is the same 13.5" and both have roughly the same hub height. Note the balljoint mounted into the C5 spindle. The advantage of that is more wheel clearance at lock.
Note: The late C4 spindle is the only one I didn't personally measure the hub height of. I found that 5" spec online.
Last edited by JasonWW; Mar 8, 2011 at 01:17 PM.
Thread Starter
Joined: Sep 2004
Posts: 6,814
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From: Hou. TX.
I'm seeing a trend here. The larger the stock rim size, the higher the hub height.
A spindle made for a 16" rim gives you a drop of 1.25" over the F-body spindle.
A spindle made for a 17" rim gives you a drop of 1.875-2" over the F-body spindle.
Therefore, a spindle made for a 18" rim should give you a drop of 2.375"-2.5" over the F-body spindle.
What spindle is factory aluminum and made for an 18" rim? The Pontiac Soltice and Saturn Sky, of course.
The Kappa platform. Their brakes are a bit weak, but can be upgraded. The bolt pattern and hub diameter are wrong, but can be corrected.
Here's some pics I took back in 08. All alumunum upper and lower control arms as well as the spindle. Look how high that hub is! I'm betting it's center is about 5.5" above the bottom of the spindle. The steering arm is on the front as well as being lower than the vette. That's a plus. It appears the rear spindles are identical to the fronts, just swapped around like the C5/C6 vettes. EDIT: They are the same except for the brake mounting lugs. Fronts are spaced wide, rears are spaced narrower.
Online pics are hard to find, but I found these.
A spindle made for a 16" rim gives you a drop of 1.25" over the F-body spindle.
A spindle made for a 17" rim gives you a drop of 1.875-2" over the F-body spindle.
Therefore, a spindle made for a 18" rim should give you a drop of 2.375"-2.5" over the F-body spindle.
What spindle is factory aluminum and made for an 18" rim? The Pontiac Soltice and Saturn Sky, of course.
The Kappa platform. Their brakes are a bit weak, but can be upgraded. The bolt pattern and hub diameter are wrong, but can be corrected.Here's some pics I took back in 08. All alumunum upper and lower control arms as well as the spindle. Look how high that hub is! I'm betting it's center is about 5.5" above the bottom of the spindle. The steering arm is on the front as well as being lower than the vette. That's a plus. It appears the rear spindles are identical to the fronts, just swapped around like the C5/C6 vettes. EDIT: They are the same except for the brake mounting lugs. Fronts are spaced wide, rears are spaced narrower.
Online pics are hard to find, but I found these.
Last edited by JasonWW; Apr 25, 2011 at 08:24 AM.
Thread Starter
Joined: Sep 2004
Posts: 6,814
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From: Hou. TX.
Here's the solution I found to mount the upper control arm inside the frame rails.
This design allows for the longest arms possible by putting the pivot point as close as possible to the engine without hitting the exhaust. This will give me less change in geometry due to my varying ride height.
The red things are spacers and shims that fit inside the frame rails like so:
By moving the shims up or down I can change the angle of the arm. This is the anti-dive angle. I think it's supposed to be 8 or 9 degrees, but I might have to experimment a little.
The upper arms will have to be removed to adjust the rodends. Once that's done, they will be locked down and the arm stays in place. All final alignment setting will be done with the lower control arm. Just like stock, but with way more adjustment potential (thanks to the upper arms).
This design allows for the longest arms possible by putting the pivot point as close as possible to the engine without hitting the exhaust. This will give me less change in geometry due to my varying ride height.
The red things are spacers and shims that fit inside the frame rails like so:
By moving the shims up or down I can change the angle of the arm. This is the anti-dive angle. I think it's supposed to be 8 or 9 degrees, but I might have to experimment a little.
The upper arms will have to be removed to adjust the rodends. Once that's done, they will be locked down and the arm stays in place. All final alignment setting will be done with the lower control arm. Just like stock, but with way more adjustment potential (thanks to the upper arms).
Last edited by JasonWW; Mar 8, 2011 at 01:29 PM.
Thread Starter
Joined: Sep 2004
Posts: 6,814
Likes: 3
From: Hou. TX.
In addition to Randy McIntosh, it appears Jason Swindle of Unbalanced Engineering is also swapping to a shorter front spindle. Are we all crazy or is this a case of great minds thinking alike? 
Thread Starter
Joined: Sep 2004
Posts: 6,814
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From: Hou. TX.
I got the specs for the Solstice (Kappa platform) spindle.
I tell ya, for a vehicle that will not be running super wide slicks and thrashed on a race track, the Solstice spindle looks like the best choice so far. The reach on the steering mount is only 1/4" longer as well as needing a much shorter bumpsteer kit compared to the Vette spindles. It has a 2" drop built in.
I tell ya, for a vehicle that will not be running super wide slicks and thrashed on a race track, the Solstice spindle looks like the best choice so far. The reach on the steering mount is only 1/4" longer as well as needing a much shorter bumpsteer kit compared to the Vette spindles. It has a 2" drop built in.
Last edited by JasonWW; Apr 6, 2011 at 05:31 PM.
Thread Starter
Joined: Sep 2004
Posts: 6,814
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From: Hou. TX.
For those guys following this thread, does anyone happen to know the factory geometry angles?
Like how much anti-dive is in the stock suspension, what the kingpin inclination angle is, front view swing arm, side view swing arm, ackerman angle, etc...?
I can't seem to find those specs anywhere.
Like how much anti-dive is in the stock suspension, what the kingpin inclination angle is, front view swing arm, side view swing arm, ackerman angle, etc...?
I can't seem to find those specs anywhere.
Thread Starter
Joined: Sep 2004
Posts: 6,814
Likes: 3
From: Hou. TX.
I went out and bought me a Soltice spindle and hub today. It's super light compared to the stock iron unit. It also looks like the better choice over all the vette spindles. I'm still trying to decide if I should use the Solstice hub and redrill the bolt pattern/make a hub ring spacer or adapt a C5 hub to fit this spindle.
Last edited by JasonWW; Apr 6, 2011 at 05:55 PM.
Thread Starter
Joined: Sep 2004
Posts: 6,814
Likes: 3
From: Hou. TX.
I've hit a bit of a snag with the Soltice hub. It appears that the flange diameter is going to be too small to be redrilled for the 4.75" bolt pattern. The new holes will be right at the edge and I'm not sure how safe that will be.
On the up side, the hub bore is stepped. It's 70mm for the brake rotor which means the 14" Z06 rotor would drop right into place, but the wheel bore size is 65mm. So I'd need to make a spacer to center the wheel.
On the up side, the hub bore is stepped. It's 70mm for the brake rotor which means the 14" Z06 rotor would drop right into place, but the wheel bore size is 65mm. So I'd need to make a spacer to center the wheel.
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Verdad Gallardo Thread Starter
Joined: Sep 2004
Posts: 6,814
Likes: 3
From: Hou. TX.
I can get past this roadblock by adapting a C5 hub to fit into the Soltice spindle. I just need to open up the hub bore by 2mm and elongate each hub bolt bore by 2mm. The area in red needs to be machined off.
Doing this will make swapping old hubs for new ones in the future fast and easy, unlike getting the new Solstice hubs redrilled every time.
I'm a little concerned by the Solstice spindle's 1/4" longer steering arm. It's going to slow down the steering response slightly as well as increasing the turning circle of the car, since the wheel won't turn as far as stock. Now I could fix that by cutting off the steering mount and bolting on a new one made from steel. There's 2 nice holes right next to it that would make it nice and strong. (Those holes, btw, are used for a special alignment tool to adjust rear caster and serve no function on the front)
So if I'm going to make a new steering arm, I'm right back to possibly using the C5 spindle. It needs no machine work done at all to fit the hub, plus there are bolt on brake packages. So I'm torn between the two. Any thoughts?
Doing this will make swapping old hubs for new ones in the future fast and easy, unlike getting the new Solstice hubs redrilled every time.
I'm a little concerned by the Solstice spindle's 1/4" longer steering arm. It's going to slow down the steering response slightly as well as increasing the turning circle of the car, since the wheel won't turn as far as stock. Now I could fix that by cutting off the steering mount and bolting on a new one made from steel. There's 2 nice holes right next to it that would make it nice and strong. (Those holes, btw, are used for a special alignment tool to adjust rear caster and serve no function on the front)
So if I'm going to make a new steering arm, I'm right back to possibly using the C5 spindle. It needs no machine work done at all to fit the hub, plus there are bolt on brake packages. So I'm torn between the two. Any thoughts?
Last edited by JasonWW; Apr 7, 2011 at 05:50 PM.
Thread Starter
Joined: Sep 2004
Posts: 6,814
Likes: 3
From: Hou. TX.
Solstice and C5 hub specs:
Solstice
5x110mm or 5x4.331" lug bolt 12mm x 1.5
Center bore for wheel 2.56" 65.1mm
Center bore for rotor 2.75" 70mm
Flange Offset 1.53" 38.9mm
Flange Diameter 5.394" 137mm
Hub Pilot Diameter 3.54" 90mm
Hub Bolt Circle Diameter 4.4375" 112.7mm
F-body and C5/C6
5x120.65mm or 5x4.75" lug bolt 12mm x 1.5 lug
Center bore for wheel/rotor 2.8" 70.3mm
C5/C6
Flange Offset 1.66" 42.16mm
Flange Diameter 5.73" 145.5mm
Hub Pilot Diameter 3.60" 91.4mm
Hub Bolt Circle Diameter 4.57" 116mm
Hub bolt M12x1.75
Solstice
5x110mm or 5x4.331" lug bolt 12mm x 1.5
Center bore for wheel 2.56" 65.1mm
Center bore for rotor 2.75" 70mm
Flange Offset 1.53" 38.9mm
Flange Diameter 5.394" 137mm
Hub Pilot Diameter 3.54" 90mm
Hub Bolt Circle Diameter 4.4375" 112.7mm
F-body and C5/C6
5x120.65mm or 5x4.75" lug bolt 12mm x 1.5 lug
Center bore for wheel/rotor 2.8" 70.3mm
C5/C6
Flange Offset 1.66" 42.16mm
Flange Diameter 5.73" 145.5mm
Hub Pilot Diameter 3.60" 91.4mm
Hub Bolt Circle Diameter 4.57" 116mm
Hub bolt M12x1.75
Thread Starter
Joined: Sep 2004
Posts: 6,814
Likes: 3
From: Hou. TX.
Check out these pics I found:
I'm gonna get a qoute on those steering arms from Detroit Speed. Maybe that will help me make up my mind as to which spindle to use.
I'm gonna get a qoute on those steering arms from Detroit Speed. Maybe that will help me make up my mind as to which spindle to use.
Last edited by JasonWW; Apr 8, 2011 at 01:21 AM.
Thread Starter
Joined: Sep 2004
Posts: 6,814
Likes: 3
From: Hou. TX.
The Solstice front arm also happens to be the same exact length as the stock one at 14". I'm going to look into using it as well. I can make fixed mounting points for the lower arm and do all the adjustment with the uppers. It gets rid of that crappy caster bushing that's always tearing.
Uppers similar to this:
They can do all the camber and caster adjusting.
Uppers similar to this:
They can do all the camber and caster adjusting.
Thread Starter
Joined: Sep 2004
Posts: 6,814
Likes: 3
From: Hou. TX.
Okay, here are 3 different ride heights from a high ride height to a lower one and the upper control arm mount is just a guess, but it's in the same location for all three pics.
Thread Starter
Joined: Sep 2004
Posts: 6,814
Likes: 3
From: Hou. TX.
I'm thinking I can mount the upper arm a bit higher, especially if I run a tall upper ball joint. Ultimately, I'm going to have to decide on an exact ride height and work from there, but here you go. Same as above, but with the arm mounted higher.
As far as using the Solstice lower arm, I think it can be done. The only detail is that the camber bushing and ball joint don't fall on the same plane. When you overlay the arms ball joint over ball joint you can see that the front bushing sticks out about an inch forward.
If I leave the camber bushing mount where it is, I would need to rotate the arm clockwise slighty to get the ball joint in the right location. Like so:
Or I can comprimise by doing a little of both. Move the arm forward as much as I can without touching the steering boots and then rotating the arm the rest of the way until the ball joint is in the correct location.
As far as using the Solstice lower arm, I think it can be done. The only detail is that the camber bushing and ball joint don't fall on the same plane. When you overlay the arms ball joint over ball joint you can see that the front bushing sticks out about an inch forward.
If I leave the camber bushing mount where it is, I would need to rotate the arm clockwise slighty to get the ball joint in the right location. Like so:
Or I can comprimise by doing a little of both. Move the arm forward as much as I can without touching the steering boots and then rotating the arm the rest of the way until the ball joint is in the correct location.
Last edited by JasonWW; Apr 10, 2011 at 07:05 AM.
Thread Starter
Joined: Sep 2004
Posts: 6,814
Likes: 3
From: Hou. TX.
Oops, I'm thinking wrong. It's not the balljoints that need to be lined up, it's the centerline of the hubs. That's what dictates the wheel being centered in the wheel well.
The Solstice hub is positioned forward of the ball joint centerline while the stock spindle has the hub pretty much centered. That means the lower ball joint needs to be moved back a little with the Solstice hub.
It's hard to see the difference, but it's there.
I wonder if the Soltice arm can handle the stress of the weight being shifted from the end to the center? It might snap in two! I might just stick with the steel arm. All it would need is to have a new balljoint adapted. A vette/solstice lower ball joint and they are about $100 ea.
The Solstice hub is positioned forward of the ball joint centerline while the stock spindle has the hub pretty much centered. That means the lower ball joint needs to be moved back a little with the Solstice hub.
It's hard to see the difference, but it's there.
I wonder if the Soltice arm can handle the stress of the weight being shifted from the end to the center? It might snap in two!
I might just stick with the steel arm. All it would need is to have a new balljoint adapted. A vette/solstice lower ball joint and they are about $100 ea. Last edited by JasonWW; Apr 10, 2011 at 02:23 PM.
Thread Starter
Joined: Sep 2004
Posts: 6,814
Likes: 3
From: Hou. TX.
I'll probably cut up the stock lower arm or make a new one from scratch.
Here's 2 possible bag mounts. This first one is a bit off. I'll redo it based on what I know now.
Here's 2 possible bag mounts. This first one is a bit off. I'll redo it based on what I know now.
Last edited by JasonWW; Apr 12, 2011 at 04:14 PM.
Thread Starter
Joined: Sep 2004
Posts: 6,814
Likes: 3
From: Hou. TX.
I did learn a valuable lesson as far as bag mounting goes.
I was wanting to get a Slam Specialties RE6, but no one has any, so I figured I'd get a Dominator 2500 for the time being to use for mock up purposes. It was only $55.
I was wanting to get a Slam Specialties RE6, but no one has any, so I figured I'd get a Dominator 2500 for the time being to use for mock up purposes. It was only $55.
Last edited by JasonWW; Apr 12, 2011 at 03:43 PM.
