TR6 A TR6 with Jag ball joints

[vettedog72]

I have never read about the significant under steer in the TR6 untill lately; I thought it was just my TR6! More years ago that I care to remember, Butler Tire in Atlanta, Ga. was THE if not THE ONLY place to get TR6 front and rear wheels aligned. I tool the TR6 in for full alignment so the new tires would wear evenly.

I received a call that my axels needed to be "pulled". Quick laughing; I think I paid some $50 for that service and I can't remember the details. The rear wheels had something done as well to get rid of the squats.

I thought it wass because of this alignment process that my TR6 took every ounce of effort available to push it when the wheels were turned left or right. They would easily plow even at low speeds with a wet surface.

Now I read that replacing the upper ball joints with jag ball joints will put everything right.

Has anybody done the TR to Jag ball joint conversion and if so, tell me all about it.

 

[Brosky]

Re: A TR6 with Jag balls

I had a very sharp tech align mine 16 years ago. Of course, I've only driven 2,000 miles in that time on nice roads, so I know that mine is still in spec.

My point is that I can push mine around in the garage with the wheels turned or straight with minimal effort. Why would these ball joints make a difference? I'm curious on this one too.

 

[vettedog72]

Brosky:
Part of what I read is below. I wonder how your suspension differs from others so as not to have these characteristics?

"The TR6 suffers from a few design flaws, mainly in the frame and suspension. It has a tendency towards severe understeer, making it nearly impossible for a single individual to push a dead car either forward or backward when under full wheel lock. Stress when turning under full lock can even crack or break the front lower suspension wishbone mounting points, which are essentially small sheet metal boxes welded to the top of the frame. Correct repair involves complete removal of the old mountings after suspension dismantling, replacement of the mounting boxes in their exact locations, and the addition of strengthening gussets welded in place. The suspension can then be reassembled and aligned. Trust me when I tell you that you do not want to pay for this sort of repair."

 

[Brosky]

Whoa, wait a minute! My mistake in reading the post. I never tried full wheel lock, probably just half or so. Let me give that a try when I get it back from body shop this Friday (I hope - I hope - I hope!!!)
I'll post back with results.

 

[tomshobby]

Re: A TR6 with Jag balls

I was under the impression that the later TR6' had these weak points on the frame reinforced so they would not break.

I do not understand why the TR6's have this problem when the earlier TR4's seemed fine. My dad had a two car garage and I used to annoy a nosey neighbor by driving my TR4 in and closing the door. Then I would turn the car around in the garage and drive back out. I could never do that with my TR6. It is all the 6 can do to turn around in an intersection.

 

[DNK]

Re: A TR6 with Jag balls

A post from Allan in the haggerty post.

What I found interesting is the mention of the severe understeer that shows up when trying to push the car or drive slow with the wheels at full lock, they called it a design flaw. I have often wondered what is all the tire scuffing and fighting itself when turning slow and whats in the front suspension design that causes it. I am going with the the Jag upper ball joints (that J.K. Jackson recomends)to get more caster, Im hoping this will help.

 

[Dave Russell]

Re: A TR6 with Jag balls

[ QUOTE ]
A post from Allan in the haggerty post.

What I found interesting is the mention of the severe understeer that shows up when trying to push the car or drive slow with the wheels at full lock, they called it a design flaw. I have often wondered what is all the tire scuffing and fighting itself when turning slow and whats in the front suspension design that causes it. I am going with the the Jag upper ball joints (that J.K. Jackson recomends)to get more caster, Im hoping this will help.

[/ QUOTE ]
I can only make a general comment. The steering on all cars are designed with some "Ackerman" geometry. Ackerman causes the wheels to toe out increasingly as the wheels are turned more from the straight ahead position. Toe out on turns if you will. Because the inside wheel is turning more sharply than the outside wheel, this increases the "turn in" responsiveness when the car is actually being driven. Particularly on a basically understeering car such as the TR6.

By the same token, this toe out when turning causes the tires to scrub when turning. the tighter the turn, the more scrub. When turning tightly at low speeds, or especially when rolling around in the garage in tight turns, this toe out induced scrub is very noticeable. At higher speeds, it is not noticeable & is beneficial.

I suspect that the TR6 has more Ackerman designed into it than the TR4's, since the TR6 is more front end heavy.

I think that the amount of Ackerman is controlled by the steering arm lengths & their positions. Don't know how "Jag balls" would affect the situation.
D

 

[piman]

Re: A TR6 with Jag balls

Hello Dave,

the Ackerman is achieved by angling the steering arms. A true Ackerman angle is from the steering pivot to the centre of the rear axle and the steering arms should be at that angle.
I don't think that you can feel 'understeer' at very slow speed unless a lot of throttle is given at that point which can 'push' the front on most cars. Also the amount of rear toe in or out on an independant rear suspension alters the understeering characteristic, toe out the rear and you will get very quick turn in, i.e. minimal understeer and possibly oversteer.

Alec

 

[Simon TR4a]

Re: A TR6 with Jag balls

I have owned a 1975 TR6, and one of several reasons I sold it was the understeer; I find the TR4a handles significantly better.
While my memory is notoriously suspect I don't think there is a great difference in the factory camber and caster alignments between the two cars, the earlier TR4 had 0 degrees caster, but the TR4a has 3 degrees as I recall.

I don't think pushing the car around the garage indicates its handling characteristics as all are hard to push with a lot of lock on, even my son's gokart when he raced was tough to push if the wheels were not straight. (I also don't think its a very good idea as it must put a lot of strain on the steering components.) The TR6 is likely harder to push with the wheels at an angle because it has wider tyres.
Most cars I have driven, if not all, understeer at low speeds and become more neutral at higher speeds, and I would guess the six cylinder engine putting more weight further forward is a factor in the difference between the two cars.

I have found that a non-stock alignment with more negative camber on the front wheels improves the initial turn in response of my car. I seem to remember the point of using Jag suspension pieces was to provide negative camber, and I think it was the upper A arm being shorter which did the trick.
Perhaps someone else can confirm?
Simon.

 

[Andrew Mace]

Re: A TR6 with Jag balls

[ QUOTE ]
I can only make a general comment. The steering on all cars are designed with some "Ackerman" geometry. Ackerman causes the wheels to toe out increasingly as the wheels are turned more from the straight ahead position. Toe out on turns if you will. Because the inside wheel is turning more sharply than the outside wheel, this increases the "turn in" responsiveness when the car is actually being driven....

[/ QUOTE ]Could be worse. Consider the average Herald or Spitfire, which apparently has -- from the factory -- "reverse Ackerman" geometry. Approaching full lock, the "outer" wheel actually is turning at a tighter radius than the "inside" wheel. Talk about scrub. /ubbthreads/images/graemlins/shocked.gif

Now if you REALLY want an adventure in pushing, get yourself a Spitfire, pop some slicks on it, and weld up the diff. NOW try pushing it with any significant steering angle!

 

[tomshobby]

Re: A TR6 with Jag balls

[ QUOTE ]
While my memory is notoriously suspect I don't think there is a great difference in the factory camber and caster alignments between the two cars, the earlier TR4 had 0 degrees caster, but the TR4a has 3 degrees as I recall.


[/ QUOTE ]

The later TR4's had more camber than the earlier ones, I think it was the 3 degrees. What ever it was worked great and the cars handled very well in tight corners.

After having a front end that worked so well it is a mystery why they changed to something that was obviously inferior.

I have wondered if it had something to do with the weight of the six?

 

[Simon TR4a]

Re: A TR6 with Jag balls

Tom, I agree, I think its the fact the engine is longer so its centre of gravity is further forward.

I'm sure you meant caster not camber, 3 degrees would be a LOT of negative camber and cause some odd tyre wear patters; I know because I tried it by shimming the suspension.
Simon.

 

[tomshobby]

Re: A TR6 with Jag balls

Simon, yup, I was typing faster than the speed of my mind! /ubbthreads/images/graemlins/crazyeyes.gif

 

[ALLAN]

Re: A TR6 with Jag balls

The jag ball joints with the shims added in front of the them will give more caster. Im hoping more caster will help the car turn in better which might help it turn more easy. My 86 300zx(commuter car)looks like it has alot of ackerman steering--when turning, the inside wheel angles in alot more than my TR6 and it turns easy with little tire scrub.

 

[tomshobby]

Re: A TR6 with Jag balls

Allan, I hope you report back and let us all know how it turns out.

 

[piman]

Re: A TR6 with Jag balls

Hello Allan,

altering the caster should not affect the turn in or amount of understeer. It's purpose is to keep the steering tracking true in a straight line and also self centre's the steering after a turn.

There are many variables that can be used to lessen understeer, if that is what you want, and one of the easiest is to adjust your tyre pressures. Next is adjusting the camber of the wheels. The danger of reducing or eliminating low speed understeer is that the car can become tail happy at high speed when using little steering input. Manufacturers prefer to err on the side of understeer as it is inherently stable and relatively easy for the driver to recover in a tight situation, oversteer can be vicious. Does the Corvair bring back memories? I remember the Hillman Imp that came out in the UK in the early sixties, that was a similar configuration as the Corvair, albeit much smaller. It had a lot of negative front wheel camber and manufacturer's tyre pressure recommendation of 15 psi front, and 30 psi rear, all to avoid excessive oversteer.

Alec

 

[ALLAN]

Re: A TR6 with Jag balls

J.K. Jackson increased the caster to improve turn in and handling--and he is an expert on TR6 performance, also according to many articles I have read more caster will make the steering easier on most cars. But I do agree you will have to watch out that you dont end up with too much oversteer at higher speeds.

 

[Alan_Myers]

Re: A TR6 with Jag balls

Hi Allan,

TR6 and TR4 have almost exactly the same castor (2-3/4 and 3 degrees respectively). The biggest difference in the front end is camber. TR4 was set up for +2 degrees (laden). TR6 calls for -1/2 degree. The change marked the transition from bias ply to radial tires.

Radial tires are heavier steering at low speeds. Also, more neg camber means a larger tire contact patch and that also makes it heavier steering, especially at "parallel parking" speeds.

Both cars had roughly the same turning circle (33' on TR4 and early TR6, 34' on TR6 from 1971 on) and have similar toe (1/16-1/8" on both).

Another factor, the TR4 steering wheel was a larger diameter, 15". ISTR TR6 are a little smaller, maybe 14".

TR4 R&P was 4-1/2 turns, lock to lock. I don't know how that compares to TR6, but could be an important factor.

I agree with Alec, tire pressures are the first thing to check, then the tire design itself. I had a set put on an Aerostar - gag - that really made for some understeer and scared me a few times!.

I also had a VW that tended to get squirrely steering, whenever the *rear* tire pressure was down a pound or two!

Other factors include wear on the suspension, what shocks are being used, any sway bars that have been installed, how they are mounted and how well they are matched. The "biggie" would be to check the frame is straight and true.

So, in a nutshell, I don't think changing caster by going to the narrower Jaguar Mk IV upper ball joints and shimming one side or the other will make much difference on a TR6. Caster is already adjustable. It isn't without bending something on the TR4, unless a trick like the Jag ball joint is used.

Caster gives stability at speed. Too much can increase steering effort. But, if it's close to 2-3/4 degrees on a TR6, that's probably about best for normal street driving. Less caster would make the car "squirrelier", especially at highway speeds, unless much more neg camber were dialed in and depending upon what tires are used.

/ubbthreads/images/graemlins/cheers.gif

 

[Guest]

Re: A TR6 with Jag balls

TR6, lock to lock, is approximately 3.5 turns of the steering wheel. Now you want some adventure, try the quick-steer rack that gives you 2.5 turns. Impossible to steer at a push-roll, downright scary to steer at speed, in rain, with the wind blowing, at night, with TR6 headlights....didn't take long to sell them to an autocrosser.


Bill

 

[piman]

Re: A TR6 with Jag balls

Hello Allan,

the original post was about reducing understeer and to me adjusting caster is not the way. Caster is all about ease of driving and stability, and is a bit of an evil necessity. Zero caster will give the easiest steering as the pivot point meets where the tyre touches the ground. This will be horrible to drive so a little caster self aligns the wheels as the car runs.

The other thing to remember is that any expressed opinion about steering or more accurately, handling, (Not roadholding, that is different) is that it is subjective.

Alec