c4 front end widening.
Thread Starter
7th Gear
Joined: Dec 2012
Posts: 7
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From: West Terre Haute IN
c4 front end widening.
I've bought an 87 front suspension with the intentions of widening it approximately 2" to fit the frame of my 69 AMX. I'll be modifying shock mounts, etc. For coil overs. I know I can buy late c4 tie rods to widen the steering without affecting bump. My question is 'are the later c4s sway bars longer or is the mount closer to pivot on control arms'?
Thread Starter
7th Gear
Joined: Dec 2012
Posts: 7
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From: West Terre Haute IN
Thank you very much. I think that's all I need. I know that widening the crossmember will affect Ackermann angle. Anyone know if a 2" change will alter the angle enough to cause any problems? I know that race cars run much less than street cars. This will be a street/track car. Also, my wheelbase is only 97" and this can affect Ackermann too.
Thread Starter
7th Gear
Joined: Dec 2012
Posts: 7
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From: West Terre Haute IN
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
I know that widening the crossmember will affect Ackermann angle. Anyone know if a 2" change will alter the angle enough to cause any problems? I know that race cars run much less than street cars. This will be a street/track car. Also, my wheelbase is only 97" and this can affect Ackermann too.
Thread Starter
7th Gear
Joined: Dec 2012
Posts: 7
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From: West Terre Haute IN
I'm sorry. I used wrong terminology. I know ackermann angle will not change, but the point that they intersect at will move farther behind the rear axle. From what I understand, the ideal point is the center line of the rear axle. I've done some rudimentary calculations and for the c4 front suspension every inch it's widened moves that intersect point rearward approximately 2.5 inches. I don't think 5" will affect a racy street car horribly, but this is the first time I've ever changed suspension geometry on a car.
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Melting Slicks
Joined: Sep 2008
Posts: 2,376
Likes: 111
From: Cherokee National Forest TN
I was wondering what method you were going to use to change the track width.
Splitting the crossmember may sound like a good idea but will result in bump steer as the rack will be to short. Using longer tie rod ends only works if the control arms are lengthened.
Suggest fabbing some plate brackets to tag the frame to the stub & blend them in. Leave the stub as stock.
Have done many stub jobs & always leave the stubs as stock & work them to the frames. To much grief splitting the main cross, finding a correct rack or modifing a steering center link to fit + your sway bar problem.
If Ackerman is a concern adjust bump & toe steer = good to go.
Luck with your project.
Splitting the crossmember may sound like a good idea but will result in bump steer as the rack will be to short. Using longer tie rod ends only works if the control arms are lengthened.
Suggest fabbing some plate brackets to tag the frame to the stub & blend them in. Leave the stub as stock.
Have done many stub jobs & always leave the stubs as stock & work them to the frames. To much grief splitting the main cross, finding a correct rack or modifing a steering center link to fit + your sway bar problem.
If Ackerman is a concern adjust bump & toe steer = good to go.
Luck with your project.
Thread Starter
7th Gear
Joined: Dec 2012
Posts: 7
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From: West Terre Haute IN
I hadn't thought about bump steer being an issue by using longer tie rods since they would still be parallel with control arm, but I see what you mean. They will pivot at a different rate. The primary reason I want to widen crossmember was for engine clearance. I need the engine farther forward than the vettes run so that I don't have to set engine back 10-12 inches. Granted, that would make for great weight distribution, but this a street car and need to retain dash, etc. I will have to notch firewall about 1-2" as is, but I can live with that. I only need about 3/4" wider to fit headers. I guess I could spend a load and get custom headers made. Small tube headers will fit, but I don't think they're going to flow well enough for 600-700 blown HP. All I'm sure of at this point is that this suspension is going into the car.....shock towers are already cut out. I did this first to insure I wouldn't change my mind and try the rebuild the pos stock suspension and brakes. Btw, for an AMC, that's about $1800 for stock parts, probably another $3000 just to get to the level of a stock c4.
Thread Starter
7th Gear
Joined: Dec 2012
Posts: 7
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From: West Terre Haute IN
I know theyre wider but from what I've gather from this forum and other places, They are only wider in the control arms. I believe the crossmember is the same width. I had bought this one with that in mind, because if I was going to widen the crossmember, and use the longer arms, I wouldn't have room for wheels, even with modern offset.
Team Owner
Joined: Aug 2004
Posts: 21,543
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From: Park City Utah
I don't know the dimensions of various model racks, but I wouldn't care; I'd have a machine shop whip up a couple spacers that screw in to the rack and accept the inner tie-rod end...effectively making the rack wider and mitigating your bump-steer issue.