Suspension Joints, metallic or rubber?

Jim

New Member
#1
Fran, As I wish to use my RCR 40 on extended road trips. Have you built cars with suspension joints other than rod ball end type(Hiem). I realise Hiem joints are standard on race cars, but they appear to be another headache to me. Your comments please.
 
#2
We have an alternative at extra cost...but it will not provide the direct and accurate feel of a rod end suspension system
If you are not looking for absolute performance it is a nice compromise....but keep in mind a GT40 is in fact a race car...not a Cadillac.
Feel free to call and discuss.
 
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Randy V

Administrator
#4
This is not a silly or stupid question/subject.

As Fran points out, the GT40 is a race car, nothing less. If you want all the precision of a true racing car, then Heim/rose joints are the way to go. But. You must be prepared to perform regular and very frequent maintenance to clean and lubricate those jonts or they will hammer themselves to death...

There's nothing wrong at all with high density poly bushings or delrin bushings. Most would never know the difference in handling and they are far less maintenance..
 
#5
Guys
The joints used on all the RCR /Superlite cars from day one are Chromoly with teflon liners in them....these should not be lubricated with anything petroleum/oil based...if anything use graphite spray and install the small rubber dirt sleeves....but really they should be left unlubed

The issue with poly rod ends is that they only work in a single plane of rotation. Some suspension system components may require compound rotation or off center rotation ...these joints cannot be replaced with poly obviously..

Really a heim joint is only in rotation and using poly bushings in the end of the shocks will take the "crash" out of the system...its quite surprising the difference just changing the shock eyelets makes....you then have the best of both worlds..
 
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marc

Lifetime Premier Supporter
#6
Fran, Jim, is the answer in the bushings or shock, valve, spring combinations for him?
I think that the "crash" isn't the problem.
A race car is built as the ultimate expression of performance in all aspects of the car. No sound deadening, tight steering, max traction and brakes, as well as light enough to worry about easing off over a hump to not blow over as well, of course, sprung like a go cart. Jim, you are also missing the point of these cars. Fran can make anything you want, but you need to understand the compromises are not to make a supercar out of a race car. When my P4 is done, I expect to wear a cool suit (Its Texas) and hearing protection with or without my helmet. AC system weighs too much and I need to sweat off some weight anyway. I would recommend maybe a softer spring setup and adjustable shocks. I am not going to mind. I used to ride crotch rockets and you can take just so much of them on a long run also.

BTW all the muscle car ads for poly and stiffer bushings mean a lot of guys don't want a mushy ride.

Fran,
I know shut up and work on the car.
 
#7
Automobile manufacturers around the world use rubber in their suspension systems for a reason....it works well. Poly type bushings can add an extra level of precision in a traditional car suspension but there's a big price to pay for it - hard ride, squeaks and increased noise, etc.

In a traditional suspension, simply replacing the (worn out) rubber bushings with new bushings can make a tremendous improvement to the car's handling.

A GT40 by its basic design, does not have a traditional automobile suspension system. Even a "supercar" such as a Ferrari or Lamboghini has a somewhat traditional suspension system compared to a GT40...which basically has a traditional race car suspension (rose jointed rod). As such, if a GT40 owner wants to have a roughly original type car this means using a rose jointed rod system (at the rear certainly). And a rose jointed rod suspension system is what it is...

Personally, my GT40 rides pretty well....not harsh at all. I have the adjustable shocks set at a fairly soft setting and the springs are not too heavy. It doesn't ride like my Suburban, but it's not bad. I can live with it without shaking my teeth out when I make my usual runs to Home Depot or Target for various things. However, if I was to take it on a major road trip I would definitely have to do something about the seat padding.....or lack thereof to be more precise!
 
#8
Is it possible to just swap out just the chromoly heim joint in the end of the shock with poly bushings...or is a completly different shock needed?
 
#9
my jbl cobra uses the heim joints 100%, very precise handling and soft ride. at one time there were soft production rubber in the rear t bird uprights and the tire squirm was scary under braking, couldn't use the harder poly bushings because of what fran alludes to in his previous post about different planes. if the car is sprung so stiffly that you need softer rubber bushings i could see the point in using them, but i have never heard or felt any banging, creaking, or groaning using heim joints. terrible myth imo.
 
#10
Mark..totally agree.

Changing the bushings in the end of the shock makes a marked difference...you have to make sure that all the brackets, bolts etc all accept the larger bushing and that nothing will go into a bind situation.

And sorry Bill ...you cannot do this on an SLC....it was not designed to house bushings within the bellcranks/shock mounts....
 
#11
I think that the fear of rod end systems is overblown. If you use high quality rodends, why would you use cheap ones, then they will last a very long time as long as they are not forced into a bound position. I would be willing to guess that a rodend system will last longer that a rubber bush system, and more that likely even a poly system. It takes a LOT of wear to ruin a rodend. Poly and rubber just can't wear as long because they are so much softer.

As far as suspension performance is concerned, You can have your cake and eat it too. Rod ends don't in themselves make the car harsh. If the ride feel you desire is street soft then run soft spring rates and less firm damping settings in the shock. The rodends won't make a soft spring stiff.

Rod end setups have gotten a bad rap because people really don't know how all this, tires (and their pressures), springs, shock dampening, chassis stiffness, and roll bar settings work as one system to suspend the car.

If I was recommending a build to you I would say to run a full rodend system and then go with softer spring rates/damping settings and tune chassis roll with roll bars. Sort of a wet track setup in the dry.

Tires and wheels! There is no doubt that 15 inch wheels verses 18 inch wheels on a GT40 for example will ride softer. The 15 inch tires are just so much more compliant.

Lastly tire pressures are one of the most effective ways to make a car ride nice on long freeway runs. Just drop pressures a pound or two as see for yourself.

Rodends really don't do anything except locate the suspension pickup points on the chassis precisely. Why would you want to locate the suspension imprecisely anyway?
 

Alex

Active Member
#12
Automobile manufacturers around the world use rubber in their suspension systems for a reason....it works well.
I'm sure it has nothing to do with the fact people are gigantic pussies today....~!~Oh noez, my car doesn't have 5 cup holders and satellite navigation and bluetooth and MP3 support and heat seated and ...... how will I ever manage to drive it ~!~:laugh:
 

marc

Lifetime Premier Supporter
#13
Alex
come on, you have the beer in your lap and a stand for your iphone. Oh wait your not done with your car either. LOL!
As for heated seats ... Beans!
 
#16
Yup, tire (tyre) pressure is a no cost way to make a huge difference in street ride harshness.

For example, my '33 hot rod weighs about 2400lbs, has about a front 55 / rear 45 weight ratio, with most of the weight centered in the middle (almost no weight overhanging the ends). Combine that with stiff springs and 40/45 series low profile street tires, and you get a good handling hot rod, but a buckboard ride.

Street tires are made to carry a 3500-4500lb car, so they ride like rocks on a 2400lb car. Reducing the tire pressure to 20-30PSI allows them to be much more compliant. Since their short and stiff sidewall is made to handle a 2+ ton vehicle, their handling remains good with a 2400lb car.

I was worried about reducing the rear tire pressure to as low as to 20PSI, so I did it in several steps of 3PSI until I found a good compromise.

The down side is that it reduces gas mileage and increases steering effort. I found that 28-30PSI in the front tires is a good compromise since I have manual steering.
 
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User Resigned

Lifetime Premier Supporter
#18
I'm sure it has nothing to do with the fact people are gigantic pussies today....~!~Oh noez, my car doesn't have 5 cup holders and satellite navigation and bluetooth and MP3 support and heat seated and ......
My SPF GT40 came with heated seats. And I've put in a lot of insulation trying to fix that.

Alex -- you do realize he's talking about his '33 street rod, right, not a GT40? Also, are you really going to let the mention of "gas mileage" go by without a comment, Mr. Four Barrel? :laugh:
 
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Alex

Active Member
#19
My SPF GT40 came with heated seats. And I've put in a lot of insulation trying to fix that.

Alex -- you do realize he's talking about his '33 street rod, right, not a GT40? Also, are you really going to let the mention of "gas mileage" go by without a comment, Mr. Four Barrel? :laugh:
I do, but 28-30psi seems awefully a lot for a 2400lb car. *shrug*

In my books, if people get more than 4mpg they're doing fine!
 
#20
At first I was very apprehensive about going below 25PSI. I worried about the possibility of rim damage from road bumps or dislodging the tire bead on hard cornering. I think you need to make small adjustments to tire pressure until you find the right compromise for each car. At 20PSI, my Hot Rod's rear tires have a normal sized road patch. They don't look low at all.

When I get my SLC, I'll start around 30PSI and then play with the presssures. With the SLC's slight rear weight bias, I suspect that I'll end up in the mid 20s PSI at all 4 corners.

When running lower PSI, I do check tire pressure more frequently to keep it at the mark.
 
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