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Triumph TR6 - Front Suspension

I have only recently found the BBS site and am amazed by the depth of knowledge of the people contributing and am sure someone will be able to solve something I have been puzzling over.
I have a Daimler SP250 on which I am contemplating modifying the suspension by fitting what I considered to be stronger TR6 upper wishbones.
The suspension has the same upper and lower wishbones as the TR3.
Looking through various manuals, the suspension appears the same from the TR2-TR5 with equal length upper wishbones. However, the upper wishbones on the TR6 are of unequal length although the suspension geometry figures are the same as the TR5.
Can someone explain what else was altered to accommodate the change.

John
John Walker

The front suspension on the TR2/3/3A/3B and early 4 are the same. The later 4 the same upper arms and bits as the TR4A/5/250/6. I believe that the upper fulcrum pin is the same though for all TR2 through 6. The easiest way to determine if you have the early vs. the late style would be to look at the ball joint attachment. If it is a threaded rod forming part of the ball joint going through a hole in the upper arms, then you have the early style. If it is two bolts that run for and aft through the ball joint and the suspension arms, then you have the later style.

Odds are you can change out the early style to the later style, but might have to play around with caster adjustment. Since the caster is not "adjustable" on the later set up, use XJ6 ball joints which have a narrower body and the XJ shims for adjusting caster on those cars. Depending on exact shim thickness, it will take 3 to 4 shims per side to bring the XJ6 ball joint up to TR4A/5/250/6 ball joint width. Just move the shim placement as required to get the caster where you want it. You will also need slightly larger diameter bolts/nuts and to open up the holes on the upper arms to fit the larger bolts.

The lower on the TR2/3/3A/3B and earliest TR4 were all the same. The steering levers changed with the TR4 and then changed again, maybe twice, during the TR4 production run. There was also a change in the trunnions that coincided with one of the steering lever changes and the change to the later type of upper arm/ball joint set up. My guess is that it was caster related, see above fix.

The lowers on the TR4A/5/250/6 are all the same as far as the arms, spring pans, steering levers, trunnions and vertical links go, but the TR4A (not sure if it was early ones only or all) used a single stud lower pivot, while TR5/250/6 used a double stud pivot. This pretty much describes the difference in the various non-wedge TR car suspensions as long as you discount anti-roll bar fitment. Steering changes are another tale.

Hope this helps with your Daimler
SteveP

Steve-
Moss shows two part #'s for Jag ball joints. Which ones?
Don
DON KELLY

Steve

Thank you for the information, I also own a TR6 and will have to compare the two suspension set ups more closely. The unequal length upper wishbones on the TR6 appear to give a significant offset which looks like 1/2" or more, this must have been counterbalanced by some other change such as moving the fulcrum bracket forward.

John
John Walker

John, The TR2, 3 and early 4's used the "equal" length upper control arms along with non-angled trunions. The suspension in these cars was designed with pretty much 0 degrees of Caster, sometimes referred to as king pin inclination. The suspension geometry was changed mid life in the TR4 and the same geometry was used in the 4A, 5 and 6's. This suspension used the unequal length upper control arms (the shorter arm being rearward). These also used the bolted trunion which was manufactured with a 2.5 degree Caster angle. The upper fulcrum bracked was essentially the same as the earlier cars. This resulted in a steering geometry that had a 2.5 degree Caster angle on both sides. This is actually a lot of Caster which creates a very stable "tracking" capability ie, when you let go of the wheel the car should track very straight down the road as long as this is set correctly and the road is not overly crowned. This also changes the steering somewhat because the front wheels lean into a turn a bit, which actually helps the car corner easier. Also, when working with the TR4A's, 5's I highly recommend making a few modifications. One should install the lower chassis mount support brackets, welded onto the lower mounts and chassis. I would also replace the lower pivots with the newer two bolt style with the additional backing plates in the chassis brackets. You will need to redrill the holes in the chassis brackets to make this modification. If you are doing a frame off, then cut the original suspension brackes off th frame and replace them with the properly drilled newer style brackets.
Steve
Steve Yott

Don,

There are (maybe were) three different ball joints listed for the XJ from Moss. There is the OE ball joint, an aftermarket ball joint carrying the same part number with an "AM" suffix and a sealed aftermarket unit. Fit is the same with all of them.
SteveP

This thread was discussed between 05/12/2001 and 10/12/2001

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This thread is from the archive. The Live Triumph TR6 BBS is active now.