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Triumph TR3 - Increasing the caster

I have at long last road tested my steering box mod that I discussed with Don Elliot a while ago.I feel the self centering needs to be improved by increasing the caster, but I can't find any method of adjustment. The only reference I can find in my w-shop manual is that the caster is 0 deg. I have this horible feeling there is no adjustment. Any ideas........................John

Hi John:
If you have an original workshop manual look in "Front suspension and Steering" on page 6 and you will see Para 5 "To adjust front wheel alignment.
To alter the alignment the easiest way is to go to any good wheel alignment shop.They have all the equipment necessary. Fooling with a Trammel Bar is not fun.

Tnx Chuck, I'll have another look in the manual its not an original, that cud be the problem.. I have no problems with the gear, I've done almost as many wheel alignments as I've had hot meals.....John

In over 45 years, I've never had a wheel alignment done on my TR3A. In it's first life, I rallied TRusty pretty hard on rural gravel roads between about 15,000 miles to 50,000 miles. The tires were starting to wear on a slant about 60,000 miles and at 80,350 when I did my restoration I left the original parts in the front end - except for the trunnions and all the wish-bone bushes which were badly worn. I measured the center to center distance for the tie rods as given in the book and found one side to be off. So I reset the dimensions as per the book and have never needed any further adjustment. Since then, I done 53,000 miles on 4 new Michelin 165 SR 15 tires, at which time I had to change them. The wear was still uniform. I put on Kelly/Springfield CENTREDS (165 R 15) and at the same time put in new ball joints and new tie-rod ends, and then set the dimension correctly. I now have over 24,000 miles on these and the wear is still even.

The dimension is given on page 6 of Section G "Front Suspension and Steering" in the "RED Triumph TR MANUAL" as 7.68" CTS (from center to center) when on the bench with the tapered parts at 90 degrees to the adjusting rod. I use a machinists steel rule with very fine graduations to measure and set the lengths.

Don Elliott, Original Owner, 1958 TR3A
Don Elliott

Don, I don't have a problem with tyre wear. The toe in, toe out is perfect.I've measured the camber and that is well within spec's.All these measurements have been done with proper wheel alignment equipment, which bolt on to were the wheels usualy are.The equipment is '70s vintage and in many ways more reliable than some modern electronic systems which are designed for speed and non trade-operators The problem I have is the steering is tight and that is due to the spring loaded pawl modification that I made and assembled to the steering box. I think you have the same mod and you very kindly sent me a mud map of same some 12 mths ago.Because my steering is now tighter and with hardly any play due to the steering box mod, the steering does not self centre as well as it use to.If I can increase the castor, this will improve the self centreing characteristics of the car. This will be a non standard adjustment and will have no effect on tyre wear.I need to get the TR back up on the hoist and find time to explore the front suspension. What frightens me is that the last time I put her up on the hoist, it was nearly 12 mths before I had time to finish what I started. Time just gets away and I'm enjoying driving her again..........

If the steering is too tight at the ends, it's like it was before the mods were added. I would suggest that you back off on the adjusting screw till it gets smooth and loose all the way from one lock to the other while in motion and it will become self-centering. Many people who drive sidescreen TR's for the first time find the steering to be very "heavy" when parking or going less than 2 miles per hour. Maybe that's the reason yours feels tight. How is it at 10 to 60 mph ?

If you back off the new adjuster and it's still tight, maybe the coil dianeter of the spring is too big and maybe the spring is bottoming inside and making it effectively a solid peg as before.

I know racers of early TR's who have made sliding fittings that mount on the top of the shock tower to let them get an adjustment in the caster.

But I think that's not a solution because if the mods have left it all too tight, it'll still be tight after you change the caster. Adding another "fix" will not solve it.

Since I sent you the drawings, I found out that my friend in California Herman Van den Acker makes and sells a kit to do this. He supplies two springs, a long one and a short one.

Don Elliott, 1958 TR3A
Don Elliott

I will try loosening the spring preasure off again. The last ime I did that the steering felt unstable. The steering at the moment has no tightness or tight spots in any part of the steering range, its very smooth. It just doesn't want to self centre whilst driving on a straight road. I might just try and back off the preasure a bit. The steering was very light before, it just didn't feel TR-ish(smile)...........

Then maybe adjustable caster will correct the problem.

If I remember correctly, the way my friend in British Columbia did it was to make a slidable plate with 4 slotted holes in it and fit it under the upper spindle (upper fulcrum pin) that secures the upper inner "A" frame" (wishbone). It is this plate with slotted holes that is sort of like making the upper wishbones longer or shorter.

Don Elliott, 1958 TR3A
Don Elliott

This thread was discussed between 10/09/2003 and 15/09/2003

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