$6 el cheapo bush from SNG . It lasted about $6 worth of time.
Always easier the second time. But the big one was a biyatch. Tried torches and a press but finally succumbed to a Sawzall and an air chisel. Should have started with the chisel.
Half a bottle of anti-sieze in those arms now!
Uryk at E-type Fabs has developed a set-up that accomplishes the same thing, but looks a little more âelegantâ.
1 Like
Gorgeous work!
Iâd considered fabbing up a similar set-up, when I removed Tweetyâs rear IRS, for a much-needed fresh-up.
Itâs really pretty but those struts have zero fore/aft give right? Wouldnât that make for a stiff ride? Iâm not seeing it on their website under products. Is it not being generally offered yet?
The ride is determined by the springs: the link is just another form of control arm, not imparting any resistance to up/down movement.
They afford a solid resistance to fore/aft displacement of the wheel, itself.
Why would the factory have decided to shock mount the trailing arms originally?
The factory arms have to be mounted on large (huge) rubber bushings to give compliance when the wheelbase changes as the suspension articulates. Their geometry is really very poor, and that is being compensated for with a lot of rubberâŚit has very little to do with ride comfort.
I donât believe Uryk is selling this set-up to the unwashed masses. He shows them on his Instagram feed for the âEvolution E-typeâ cars he is building, which get a whole host of super-cool, proprietary parts that I shared on a thread a few weeks ago.
1 Like
Likely cost, and for most purposes, the need for extremely rigid fore/aft control was not worth the extra work of designing and fabbing up the requisite parts.
As is the usual for street cars, a compromise.
Totally agree with this.
Ride comfort is dictated by three main factorsâŚspring stiffness, damper rates, and binding related to the geometry. Poor geometry necessitates a lot of rubber compliance at the joints, which creates binding.
My â65 Fastback Mustang has had its suspension geometry optimized to the point where it uses NO rubber OR polyurethane bushingsâŚitâs all solid roller and spherical bearings. Itâs got moderately stiff springs, and moderately high damper rates, and yet, itâs totally comfortable as thereâs almost zero binding occurring.
At the drawing board, why would they plan it like this? Tolerances? What about the rear wheel steering stuff everyone is talking about - why did you leave well enough alone with tweety?
If everything is solid roller bearings, what about NVH; and isnât it a lot of load for these?
In the main, it was known, early in the carâs racing life ('64-'65) the real limiting factors were the brakes and the gearbox.
It became fairly obvious, fairly quickly, that to address those issues in a substantive way, was not worth the OOâs money.
It then served primarily as a street car, and when I got it back OTR, I also was quite aware of the carâs limitations, and I was willing to deal with those shortcomings.
As for use of rubber bushes rather than precision bushings/proper alignment of pivot points?
Time/money compromises.
Ease of packaging, less parts= lower cost. Turning the trailing arms inward eliminates the rear-steer characteristic, so thereâs no doubt itâs an improvement, but they obviously decided the production configuration was good enough at the cost.
As far as NVH on my Mustang, some of the solid bushings are a greased Delrin sleeve within an aluminum sleeve that seem to do a good job of knocking down vibrations. Having sea is that, some are metal bearings, but itâs simply has not been an issue.
1 Like
I had a similar set up to Urykâs in my '65 coupe race car. Was never convinced that it worked as planned. Manufactures used to do (maybe still do) rear suspensions in a fashion that induced toe in on the outside wheel in a turn to reduce oversteer - that is a tendency for the rear to try and steer the car. The stock E Type trailing arm will have that effect, by pulling the rear wheels forward (greater effect on the outside wheel because of weight shift). My race car had a bad oversteering problem that necessitated removing 100 plus pounds from the boot area before I could get it under control. I always suspected that going to the semi trailing arm made the oversteer worse. My stock coupe which I occasionally autocross does not exhibit any unusual oversteering.soâŚ?
(If you ever work on rear leaf sprung cars have you ever noticed that the front link to the spring is longer than the back? This induces rear toe in.)
Do poly bushings for the rear come apart - yes. These are brand new - damage ensued just from bolting them in with suspension at full droop.
1 Like
Correct, to the degree that many do it to increase understeer, which is a more stable and saferâin the hands of an average driverâhandling parameter.
A stock E Type, because of its lower control arm geometry, tends to not have induced toe-in, but the radius arms tend to rotate the entire IRS cage towards that.
The first time I had seen that modification to an E Typeâs IRS, was on Bernard Juchliâs highly-capable race car: that was enough to tell me it was a worthwhile modification for high-performance applications.
Datsun 510 (and BMWs, for years) rear semi-trailing arms had specific modifications to eliminate the in-built toe-out on roll, for performance use.
Jeez thatâs kind ofâŚawful? Are they SNG? Did you let them know? I think Polybush is their main supplier and theyâve had a lot of issues recently, suspension bushes that donât fit, and steering mounts with crooked mounting bolts come to mind in my experience.
1 Like
It wouldnât have cost Jaguar a penny more to locate the forward end of the trailing arms farther inboard or even in line with the inboard lower fulcrum. This wasnât about cost. They were seeking a measure of rear wheel steering when cornering. Many enthusiasts donât appreciate that and seek to relocate that attachment inboard, and thatâs their business, but what Jaguar did wasnât âwrongâ or âcheapâ, it was an engineering decision.
1 Like
some comments;
-
That IRS rides better than so many other much later designed vehicles I have been in
-
dont ever buy cheaper bushes, my small ends are not lasting anything like original metalastic
-
its handy indeed to have the correct Churchill tool for doing these bushes, they will still max out a 12 ton press
-
I made a simple tool from plate to dislocate the big end bush from its mount, has worked every time since, even on old rusty cars, used to be a beast of a job before that
1 Like
They are from SNG. They didnât argue about it. I got a new one. Didnât complain about the small one - fixed it with crazy glue â still together.
1 Like
I gotta try that!!!
I donât disagree that pulling the rear wheel forward under articulation produces toe-in, or that this is a good thing for a street car, but I disagree that the way it was done was a great design.
Having your entire rear suspension system moving around on rubber mounts, which are going to wear, and change in stiffness over time is far from ideal. Donât forget, this doesnât just allow the cage to pivot about its vertical axis, but also allows the cage and diff to rock back and forward longitudinally.
There are other ways to produce the toe characteristics you want. Here is an example of one guyâs approach on an E-type race car that he developed over many years. The trailing arms are turned inward to align with the fulcrum shafts of the wishbones, then heim joints are threaded into the ends of the wishbones to allow toe adjustments of the rear hubs. This same effect could be achieved in any number of ways.
