I just started to mount my rear axle, and was wondering what angle to drag links? The rods are 40 inches long. Do I mount them to the frame, or move them in further towards the drive shaft?
First up, they are not drag links. That is generally the term used to describe the link from the pitman arm on the steering box to the steering arm on the spindle--in other word, at the opposite end of the car. What you have in the photo is trailing arms and in the case of the Jaguar independent rear end that you have, a single link runs forward from the lower arm just inboard of the hub carrier to the frame. In the original Jag installation it runs pretty close to directly forward from the outer end of the lower arm. As the lower control arm is the primary locator of the hub carrier by way of its design (fork at each end) is is a good plan to use some sort of compliant bushing at the chassis or lower arm attachment point the way that Jaguar did it in the original installation. The lower arm pivots on needle roller bearings so its fore and aft movement as it moves up and down is pretty much non existent. Although the trailing arms in your photos are long they will still move in an arc at the hub end and may put the suspension in a bind if you use heims or such. This is what the original Jag package looks like in the factory "cage" and as you can see there is a single trailing arm with a big bush at the front. Roo ps This is not a totally HAMB "friendly" package but as they started putting putting these rear ends in hot rods in the early sixties (when wrecked XKE's started to appear in junk yards) I guess that it is OK
Thanks rooman now I know they are trailing arms. I have the rubber bushing you are talking about, and heim joints. So you are saying to mounting them to the frame would be closer to the stock jag location.
I find it is best to attach the trailing arm in the same axis as the lower contol arm. Imagine a very long bolt passing thru the lower control arm attachment and extending forward about 18" and the trailing arm bent to pivot on it with a heim. That way the trailing arm is going thru its range of motion at the same 'rate' as the control arm and won't affect its' travel.
I am part of the jag group. I have read the form, and looking for more info. My parts came from snowwhite parts. They specialize in jag parts and mounts.
OJ, I understand the engineering principle of your method still like the idea of pretty much replicating the factory installation with the trailing arm close to parallel with the longitudinal axis of the car and installed with a compliant bush at at least one end. In addition I simply don't like rigid rod ends in the street environment. Roo
What Rooman is saying is that closer to perpendicular to the half shafts is the way that they come from the factory. If it were a live axle I would say that angled in is your best bet but with the independent the factory placement is either parallel to the chassis as Roo pointed out or perpendicular to the half shafts.
I have a factory rubber bushing on the axle end and I believe a heim with a urethane on the other. Is it best to keep the arms long, or make them the length of the factory?
Longer reduces the arc that they swing in and thus lowers that amount that the bush has to move to provide compliance so if there are no other space considerations them longer is generally better. Just make sure that they will clear the frame at full bump on the uprights. The closer that you can keep the trailing arm to level relative to the pivot axis of the lower arm with the car at ride height the better as then the trailing arm will be in the middle of its arc and the fore and aft displacement will be minimized. Again, ground clearance and the height of the frame will determine how close you can get to this ideal. Don't put a long bracket off the frame and hang the trailing arm down where it looks ugly just to get the arm parallel to the lower arm pivots. The purpose of the trailing arm is to provide some longitudinal support when the wheel hits a chuck hole or such so that the inner pivot yoke does not have to carry all the load. Roo
I have the center section mounted, so I can arc the axles and make sure they don't hit. Thanks again rooman.
Having just been through this with my buddy's RPU the trailing arms must and I repeat MUST follow in a straight line with the frame. His were installed like a set of solid rear end ladder bars and every time the rear end went up or down the rear tires would toe in or out causing very premature tire wear.
The problem with Jag rear end is the trailing arm and the lower lateral arm both move on different arcs which cause a change in toe. Corvettes are worse. There is a simple fix that the OP should consider. The front pivot points should be moved inwards so it is in a straight line with the INNER pivot points of the lower lateral control arm. This effectively is creating a giant A-arm [ similar to the tension strut on lower arms on pre-73 mustang fronts] This eliminates any toe change during suspension movement. See photo attached to get the idea.
this setup as Kerry above shows is in my pick up and has done hundreds of miles with absolutely no drama
This is the problem I ran into last time. I know that jag has them straighter, and some say to do it like kerry. Do I need to keep them long? I can weld the bushings on at any angle so that is not a problem. What is different on a jag car that they can keep them straighter and shorter.
Kerry, due to the fact that the lower arm pivots on needle roller bearings and it reasonably wide based at the attachment point to the rear end I find it hard to believe that there is the possibility of enough toe change to make the tires wear excessively. If this is a problem why did the factory locate it the way that they did? In my experience (I currently own a number of Jags) most tire wear comes from camber not toe as the use of the halfshaft as the upper suspension link does induce quite a bit of camber change. I am not saying that your install is wrong (in fact it is a great idea) but I don't think that it is mandatory. With compliant bushings in the factory install the trailing arm is really only acting as an extra support as I stated in an earlier post. If the inner lower arm pivots were also capable of movement (apart from rotation) I could see the need to align the pivot points. Remember that in the original factory installation the center section is soft mounted and thus the lower arm can move back and forward as the center section moves on the mounts, hence the need for the outboard restraint of the arm. A long trailing arm as proposed by mcmopar will also swing in a very shallow arc and even if it was installed with heims and thus rigid enough to be able to displace the outer end of the lower arm I can't see that it would be enough to cause any significant toe change. The tube that comprises the lower arm is of a reasonably large diameter and I can't see it flexing very much, if at all under normal road use. After all the lower shock mounts are located on it and they are carrying the weight of the car and in the original install that is relatively high. Roo
Doesn't that fact that in a non stock application the cage is usually discarded along with the compliant mountings in favour of solid mountings (as pictured) require a rethink on the radius rod articulation and bushing type? Chris
Chris, yes, and the OP was planning to use compliant bushes in the trailing arms in his installation. Roo
Hey mate! thanks for the intelligent response [ I've been copping a bit of flack from some of the status quo "rat rodders" lately. and even getting my posts deleted] My experience is with Corvettes which are a nightmare. On my Road Race Corvette the inner bars were triangulated inwards to get the same result [the trailing arms were cut ] The purpose of those arms is to take compression loads under acceleration and tension under braking . Under acceleration the thrust from the wheels against the weight of the chassis will try to toe the wheels in. [this is why drag racers will brace a rear-end housing] If these loads weren't that great , those trailing arms wouldn't be needed. Being a road-racer , I am not a fan of spongy [OK compliant ] bushings being needed to overcome a slight flaw in geometry. By triangulating them in [ if the front pivots were perfectly inline ] you could actually weld the trailing arm to the outer lower arm, It becomes a true A-arm. If GM used the Jag design on the Corvette, the Corvette wouldn't have been such a pig in the handling dept [ they need a lot of serious manipulation to correct flaws]
Kerry, I agree that the Corvette is a whole different ball game and needs a lot of help. (And I know all about bracing housings for drag racing because I build mainly dragsters). On the subject of "rat rodders" some of their builds scare the***** out of me regarding suspension and steering horrors. Roo
I have a 2 1/2 in. bushing mounting my housing to the frame. I will take a picture of my mount tonight.
Apologies - you've got what looks like urethene bushings on your differential mount - the solid ones I was referring to were the slime green pictured. In your application I'd be using similar bushes on the radius rods (forward end) mounted in alignment with the inner pivots. And yes this effectively creates an A arm and the mount between the rod and wishbone could be completely solid. Chris
With the urethane mount, then it would be better to make a complete A arm style. So then with this logic, can I run a string line off of the needle bearings, and put my mounts there?
I'd say so. A possibly better way would be to remove the pin from the wishbone inner pivot and replace with a length of bar or studding to enable the forward mount to be constructed off it - effectively a jig - and zero misalignment. Studding works well as nuts and washers enable patterns for bracket to be fettled. Chris
Or you can simply mount it like the Jag, roughly in line with the point where it attaches to the lower arm. As Kerry noted the Corvette IRS is the one that has the real problem with toe in variation. The "A" arm configuration is better but may interfere with exhaust pipe routing etc and will involve some more fabrication in the way of crossmember, etc to mount effectively. Also due to the fact that the lower inner pivot is relatively close to the ground plane the new forward pivot for the wishbone configuration will also be low and may result in "highsiding" on those narrow and high crown Kiwi back roads. With your center section mounted on bushes I would not make the connection between the rod and wishbone rigid (as suggested by Chris) as any movement of the center on the upper mounting bushes would put that joint in a bending moment. That situation could be obviated by adding a couple of link bars from the forward bushing mounting bolt down to the tie bar that puts the lower arm pivot in double shear as that will stop any torque reaction from rotating the center section. Remember that the braking torque is being carried by that top mount and it can be substantial. I am a KISS guy and would just hang it off the frame with the trailing arm as long as possible. That said, the visibility of the trailing arm with the chassis at ride height could be an issue as I mentioned in an earlier post. You could use an early Ford wishbone for the trailing arm and then the car would look traditional in side view. Roo
At the risk of taking the discussion in an unexpected direction Roos point above highlights the fact that the pics don't indicate the existence of any torque control of the differential. My understanding is that the 4 mounting bolts on the top of the diff in the stock installation are merely there to hold the diff in place, ie support its weight within the stock cage, and not take all the torque loadings. It seems to me the bushed mounting is relying solely on those 4 bolts, in the absence of anything else. I've heard the things I'm referring to as pinion climb bars or torque bars / straps. Check out http://www.uk-hotrods.co.uk/v2/tech/jag_rear/tech_jag.php If this is already covered in the plan then I'll shut tf up! On the possibility of fixed mounting of the radius rod to the lower wishbone I was envisaging the solid mounting of the differential, and not the urethene bushed situation that we now know to be the case. Chris
What is these roads you are referring to? Mine was used at Taupo Motorsport Park, and Pukekohe Raceway. [they both make Mount Panorama look like a bush track ]
This ^^^^^^^ is exactly how I set up the front pivot points in my car. I had 5/8 rose joints [heims] on the inners, so I got a piece of 5/8 rod and threaded one end and guided it through the pivots. At the front pivot point I used a "female" 5/8 rose joint to locate tabs which were welded to the frame [ the front joints were horizontal like a formula Ford ] The actual arm used male rose joints at each end. It was a "lets try it and see" no brainer to do.
If you look in the picture, I will have a bar on each side of the carrier, with urethane mounts, and then going to the frame. I don't have them in the picture, but they will be there to help with torque, and braking loads. With them it should be locked down on all angles.
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