pinion angle question

[90MarkVII]

For you roadrace types...factory style 4 link, CHE lowers, CHE adjustable uppers. The uppers have poly on one end and spherical on the other (body end).
The car is 99% street with long road trips. It has been on Hallett and will see Cresson as well as Eagle Canyon.
Suggested pinion angle?

[Mach1]

I'd put stock UCA's back in there, with stock bushings on the axle end too. The UCA's need to change length via the bushings as the body leans, without the give they will bind up. Or go to a 3 link. Set the pinion angle that allows you to put down the power on exit, with the stock UCA setup you will need to account for the angle changing under load. I'd prob start with -2 deg with stock UCA, -.5 deg with all sphericals on a 3 link.

[90MarkVII]

Thanks for looking in. I appreciate the input.

Let me revise the description.
The uppers will have rubber bushings at the differential and spherical bushings at the body. The spherical ends keep the uppers from binding.
The lowers are custom square tube from CHE that accept the air spring. The have poly/Delrin bushings on both ends.

So....with no give on the lowers, and some give on the uppers, maybe go with -1 degree?

[dee]

-1- -.5 is what I set mine at but I did no road racing.

[90MarkVII]

-1- -.5 is what I set mine at but I did no road racing.

Thanks.

[Baron Von Crowder]

Thanks for looking in. I appreciate the input.

Let me revise the description.
The uppers will have rubber bushings at the differential and spherical bushings at the body. The spherical ends keep the uppers from binding.
The lowers are custom square tube from CHE that accept the air spring. The have poly/Delrin bushings on both ends.

So....with no give on the lowers, and some give on the uppers, maybe go with -1 degree?

Perhaps explaining how it works would help with what he is trying to say, and what you are saying.

Look at the geometry of the uppers, they more or less go at an inward angle to the axle.

\ /

When the axle moves up, they have to get shorter, due to that angle. The rubber bushings up top squish to provide that, since the metal arms cant get shorter. So with your spherical bushings, there is no give on that end, they can only rotate. What you are now asking is for the rubber bushing in the axle mounting point to take all the give.

This is what happens when there isn't enough give on the body end:

[Mach1]

The uppers will have rubber bushings at the differential and spherical bushings at the body. The spherical ends keep the uppers from binding.

Actually they don't help with the fact that the upper arms need to change "length", they do this with bushing deflection.
This is from MaxMotorsports

When retaining the original four-link suspension, the best compromise between resistance to suspension bind, best control of axle position, best ride quality, and least potential damage to the chassis, is to retain rubber bushings in the rear upper control arms.

[JETFAST]

On the dirt track cars, limited modified, 101 inch wheel base triangulated 4 link, we have the same issues with the control arm bushings. they make all kinds of bushings these days, different off set and compounds. The softer the bushing the better they seem to work, but only last a couple of races, before they look like the one above, and start binding up the 4 link.

[90MarkVII]

I hear what you guys are saying.
But my options are somewhat slim if I need to correct the pinion angle...which I may need to do now and most likely need to do if I lower it any more.

[Baron Von Crowder]

I hear what you guys are saying.
But my options are somewhat slim if I need to correct the pinion angle...which I may need to do now and most likely need to do if I lower it any more.

Im of the opinion that pinon angle is inconsequential if the suspension isnt doing it's job.

this is from CHE's website:

Nylon/Delrin: Straight nylon bushings should only be used on properly
modified vehicles
Advantages:
-Low cost
-Hard, inflexible material that eliminates lateral or twisting movement
-Does not “squeak” or need any lubrication
Disadvantages:
-Limits rear axle articulation
-Will cause damage to mounting points which are not properly reinforced if they
are subject to twisting or lateral movements
-Should only be used on dedicated race cars
-Very harsh ride quality
-Very high transfer of road noise
CHE Performance Products Page 1 of 2
www.cheperformance.com Spherical bearings: Also known as rod ends or heim joints
Advantages:
-Allows free, unrestricted axle articulation
-Eliminates unwanted axle movement
-Usually designed to allow suspension adjustments
Disadvantages:
-Very Harsh ride quality
-Because they contain moving parts, they will wear out over time
-Possibility of breakage
-High cost
-Require periodic cleaning and maintenance
More Informat

[Mach1]

Props to CHE for that list of consequences, I've never come across such a solid list.

[aggie97]

bolt it up and run it. Done.

Work on the loose nut behind the wheel before turning wrenches on the car.