C3 IRS VS Jaguar
- Thread starter Ralphy
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It also crossed my small mind that with VanSteels coil over setup. It does the same, putting the spring in a position where it pushes in on the half shafts.
Plus if you install a spherical bearing at the front of the trailing arm this would also increase load.
Plus if you install a spherical bearing at the front of the trailing arm this would also increase load.
GT6Steve
Well-known member
Guys, I drive the shit out of a 69 XKE so I can testify the suspension works at speed. The more the better it seems and I've not yet had a "moment" that was not throttle induced. The 81 Vette in contrast seems to let go suddenly at the limit without a lot of warning. In fairness, the latter is probably tires more than geometry. That said, I toss them both into the corners with huge confidence but I trust the Jag (lighter) more than the Vette...
Twin_Turbo
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Don't do it, total waste of money. Very heavy and still a crappy design. If you want something compact, get a ford 8.8
Ozzy
Well-known member
8.8 irs in a Vette, what does that take to accomplish?
big2bird
Charter Member, Founder Bird-Run, Cruise-In Bird-R
I'll vouch for that. I just did brakes on a 68 E Type. You HAVE to drop it to do them. That assembly is NOT light at all. (But the car sure is).
Twin_Turbo
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voodoovette
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A 8.8 is a great choice but after going down that road myself, I decided to go with the Viper 3 GEN differential. The Viper 3 GEN Dana 44 has splined stubs that you can purchase a pair of 930 CV splined flanges from "THE DRIVESHAFT SHOP". This will let you have a nice HD IRS with strong CV joints, but of course, you will need upper control arms with this set up. The 8.8 uses a Tri-pod type of CV that is not strong enough for me and to convert to a porsche 930 CV, it will cost $800 just for a pair of 31 spline stub axles and the aluminum case of the Viper Super Dana 44 is much beefier than the aluminum 8.8 case at the pinion bearing area. All of this will make you go nuts!!:nuts:
I hate to re-invent the wheel. Looking at the Jag further makes me wonder how it would perform under high acceleration/high HP with no control from above. Also the twin springs/shocks seem to be no accident, seems needed for bump loading.
The Guldstrand setup, I am liking due to the forward control arms being mounted behind the half shaft. I am going to lose length when I move my control arms and this gives me length and the twin mounting points. Also removing toe issues.
TT with the Guldstrand do you use the bearing support in stock condition? Asking do you remove camber rod mount or not by cutting it off?
Trust me I am no where near up to the understanding you guys have.
Welding and cutting.. FUNNY!
The Guldstrand setup, I am liking due to the forward control arms being mounted behind the half shaft. I am going to lose length when I move my control arms and this gives me length and the twin mounting points. Also removing toe issues.
TT with the Guldstrand do you use the bearing support in stock condition? Asking do you remove camber rod mount or not by cutting it off?
Trust me I am no where near up to the understanding you guys have.
Welding and cutting.. FUNNY!
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Twin_Turbo
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Yes, stock bearing supports bolt to cast aluminium mounts:
The "fork" is retained
The "fork" is retained
voodoovette
Well-known member
Ralphy,
The axle is the upper link in both the C3 and Jag rear suspension, that is the problem. The axle will move slightly in and out of the differential during cornering and cause camber control problems. It works for the street but not the best for serious performance. I may be wrong, but I believe the Guldstrand also uses the axle for the upper link, if this is the case, it will also not be the best for good road course handling. I would suggest a type of slip axle, either CV or slip yoke with U-joints for the axles and a upper link, either control arm or single link with heim joints. If you use an upper link, the axle must be able to get longer and shorter as the suspension travels up and down, this is why you need a CV or slip yoke. TT has a lot more knowledge on this than me but I have already eliminated the stock rear and installed a C5 rear set up with a Viper Dana 44.
The axle is the upper link in both the C3 and Jag rear suspension, that is the problem. The axle will move slightly in and out of the differential during cornering and cause camber control problems. It works for the street but not the best for serious performance. I may be wrong, but I believe the Guldstrand also uses the axle for the upper link, if this is the case, it will also not be the best for good road course handling. I would suggest a type of slip axle, either CV or slip yoke with U-joints for the axles and a upper link, either control arm or single link with heim joints. If you use an upper link, the axle must be able to get longer and shorter as the suspension travels up and down, this is why you need a CV or slip yoke. TT has a lot more knowledge on this than me but I have already eliminated the stock rear and installed a C5 rear set up with a Viper Dana 44.
OK, VooDoo this makes more sense. I came to the conclusion TT's setup would either bind or the axle had to slide. Guldstrand still seams to have issues regarding toe. Due to the fact the forward links are un equal length. Causing the hub to rotate then moving the toe rods unequally.
Let me ask this if your rear wheels do toe, is it better if they toed out then in? Because it appears Guldstrand would toe in also.
I really, really would like to rip off TT's set up I think. However I do not know if I'm up to the task. Seems no toe or wheel base change at all.
Let me ask this if your rear wheels do toe, is it better if they toed out then in? Because it appears Guldstrand would toe in also.
I really, really would like to rip off TT's set up I think. However I do not know if I'm up to the task. Seems no toe or wheel base change at all.
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voodoovette
Well-known member
Rear suspension
Ralphy, TT is better to answer the toe issue, my belief is depending on the type of toe rod you use will provide toe problems or not. TT, correct me if I am wrong, but if you use a lower or upper control arm with toe adjustment part of the control arm, no toe control problems, but if you have a separate toe rod, as on a C4 or 5 corvette, you will have some "bump steer" just like the front suspension. If I can remember correctly, TT had a built in toe adjustment in his lower control arm, this is the way to go. If you want to go with a c4 varriant with an upper link, the cheapest way is with a slip yoke axle like the 1st/2nd GEN Vipers used. You can have these made to any length you want at most driveshaft/off road shops. If you are not familiar with them, check E-Bay under Viper axle and you will see some for sale. I suspect the Viper axles are to long, but you can get a set made for your application or buy a set off E-bay for cheep and have them shortened.:thumbs:
Ralphy, TT is better to answer the toe issue, my belief is depending on the type of toe rod you use will provide toe problems or not. TT, correct me if I am wrong, but if you use a lower or upper control arm with toe adjustment part of the control arm, no toe control problems, but if you have a separate toe rod, as on a C4 or 5 corvette, you will have some "bump steer" just like the front suspension. If I can remember correctly, TT had a built in toe adjustment in his lower control arm, this is the way to go. If you want to go with a c4 varriant with an upper link, the cheapest way is with a slip yoke axle like the 1st/2nd GEN Vipers used. You can have these made to any length you want at most driveshaft/off road shops. If you are not familiar with them, check E-Bay under Viper axle and you will see some for sale. I suspect the Viper axles are to long, but you can get a set made for your application or buy a set off E-bay for cheep and have them shortened.:thumbs:
I guess Guldstrand's web site answered the question of toe. With a racing setup over steer is a nono. Front end setup should be toed out. My first thought was that the rear should be the same. However going over Guldstrand specs shows the opposite, then I realized. The rear would be reversed, toeing out the rear will cause an over steer chassis. Kinda like a fricken fork lift. If you ever drove one you would know what I mean.
http://www.guldstrand.com/alignment.asp
http://www.guldstrand.com/alignment.asp
Twin_Turbo
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A lower and upper arms relate to camber control and really, there's no problem with using the halfshaft as the upper control member as long as the diff is tight and the stub axle has no excessive play.
Front toe out is great for handling but crap on the roads. A good example is a 3rd gen camaro or firebird, those are set up for toe out and they are awesome in the corners but on uneven roads the car will pull like crazy. Never toe out the rear, it will rear oversteer, snap oversteer. Problem is, that's exactly what our trailing arm suspensions do if the halfshafts are level, anything away from there, either up or down promotes to toe out meaning you have to set more initial toe in. Best to have the shafts a little under level swinging to or slightly over level but not further over than about the same angle it's under statically + the tolerance you set in initial toe in so that the arm doesn't swing further and goes to toe out again.
There's another problem, especially with the early C4 IRS, they have a high roll center, great for roll stability but theirs is a little on the high side, causing a jacking effect. There are plenty of guys who have experienced snap oversteer on a C4 because of it. I remember this video of a guy in some twistes who suddenly lost contol
Front toe out is great for handling but crap on the roads. A good example is a 3rd gen camaro or firebird, those are set up for toe out and they are awesome in the corners but on uneven roads the car will pull like crazy. Never toe out the rear, it will rear oversteer, snap oversteer. Problem is, that's exactly what our trailing arm suspensions do if the halfshafts are level, anything away from there, either up or down promotes to toe out meaning you have to set more initial toe in. Best to have the shafts a little under level swinging to or slightly over level but not further over than about the same angle it's under statically + the tolerance you set in initial toe in so that the arm doesn't swing further and goes to toe out again.
There's another problem, especially with the early C4 IRS, they have a high roll center, great for roll stability but theirs is a little on the high side, causing a jacking effect. There are plenty of guys who have experienced snap oversteer on a C4 because of it. I remember this video of a guy in some twistes who suddenly lost contol
Twin_Turbo
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Yes, it should work with a single shock/spring but it will load one side more than the other. The watts linkage is done because packaging an upper arm there is next to impossible.
If you add an upper arm it shouldn't match the halfshafts, it should comply with the suspension geometry of the lower arm and the halfshaft (if the shaft is fixed), meaning pivots & upper pointing to shared IC. Get it wrong and you will snap something. You could float the stub axle and adjust the arms to pull it slightly out but still geometry has to be almost dead on to minimize stub movement then. This gives you a little bit more leeway but still not a lot. There should be an old topic about this w/ plenty of pics.
If you add an upper arm it shouldn't match the halfshafts, it should comply with the suspension geometry of the lower arm and the halfshaft (if the shaft is fixed), meaning pivots & upper pointing to shared IC. Get it wrong and you will snap something. You could float the stub axle and adjust the arms to pull it slightly out but still geometry has to be almost dead on to minimize stub movement then. This gives you a little bit more leeway but still not a lot. There should be an old topic about this w/ plenty of pics.
TT, that photo almost matches my frame. Seems if I were to use 1 spring/shock it would need to be between the lower control arms. Other wise I see the opposite arm wanting to raise up, that would get all ugly!
As far as the upper A arm idea, I see binding issues even if you hit the geometry dead on. As over time things start to move. Other wise no one would need to re-align their cars.
Here is the mess I need to fix, notice the bent shock!
As far as the upper A arm idea, I see binding issues even if you hit the geometry dead on. As over time things start to move. Other wise no one would need to re-align their cars.
Here is the mess I need to fix, notice the bent shock!
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