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TR4/4A TR4 Sway Bars

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We are talking about fitting the TR6 Rad Guard to a TR4 (NOT a TR4a).

I have the TR6 rad guard AND a bare TR4 (1962) frame in my garage right now. Definitely do not bolt right up, much to my dismay.

Hence, the ruminations on modification and/or fabrication.

I am committed to doing this however. The tr6 sway bar is UBER sweet compared to the flimsy TR4 model.

To acommodate the additional torsion from the thicker bar as as well as the longer "reach" of the tr6 bar (which aids in more leverage/torsion transfer), you need a bracket system way more robust than the simple manner by which regular tr4 bars are mounted.

That's my guiding thought at this point, but am open to counter point before I hack up a tr6 rad guard I paid $100 for.
 
I installed ADDCO swaybars on the front and rear of my TR6 a few years ago. The literature that came with the rear bar said not to run the rear bar with the factory front bar. They said you needed to install the ADDCO front bar. (as mentioned earlier in the post the ADDCO front bar has a larger diameter than the factory bar)

If you look at Ted Shumakers site you can see a chart with figures for sway bar diameters and rates. Notice the comments below the chart. Oversteer can result from to large a rear bar in relation to the front bar.

https://www.tsimportedautomotive.com/swaybarrateschart.html

Salesmanship or a saftey precaution?

I can tell you they improvement in handling was remarkable.

BOBH
 
doughairfield said:
tdskip,
Would that also bolt right up to a TR4?
Click to expand...
Almost certainly not, IMO. The TR4 has basically a TR3 frame with some spacers added to move the front suspension farther out; while the TR4A frame was redesigned mostly from scratch (and hence doesn't have any funny spacers). So the spacing between the frame rails is different almost everywhere.
 
bobh said:
https://www.tsimportedautomotive.com/swaybarrateschart.html

Salesmanship or a saftey precaution?
Click to expand...
Little of both, IMO, but the caution is very definitely a good one. Unless you are expecting it, oversteer can be very unsettling and quite apt to leave you sitting in the weeds wondering what happened.

Running a stiff bar in the rear also leads to wheel lift and loss of traction.

BTW, Richard Good (Goodparts) used to be willing to bend custom sway bars for the earlier TRs in your choice of diameter. Not sure if he still does, but might be worth asking if you are looking for more roll stiffness than the ADDCO bars give.

Also, you can lower the rate of either bar by using spring-loaded end links.
 
Great chart. I'll read it soon.

I drive an air cooled 911 as my daily driver and autocross it when I can. Vehicle handling dynamics at their limit are no stranger to me!

Got my first Porsche when I was not too long out of college (a couple years) and did some stupid youngster stuff on backroads and ended up in a field once or twice.
 
Worse thing you can do in a 911 is to lift off when the rear swings out. When that happened in my 911s, I usually held on tight and applied to throttle. Miss those cars, they are fun.
 
swift6 said:
TR3driver said:
Running a stiff bar in the rear also leads to wheel lift and loss of traction.
Click to expand...

And that... is oversteer.
Click to expand...

Not necessarily. For example, the 2005 VTR autocross had a wide sweeping (and banked) turn at one end. Although no one got a picture of it, my inside rear tire was light enough to spin through almost the entire turn (someone later told me they could see the tire smoke) and yet the steering was very nearly neutral (the other tires weren't loaded enough to even develop much of a slip angle). Of course my problem wasn't a too-stiff bar in the rear, but just Triumph's curious disregard of roll centers when designing their suspensions.

It's actually pretty easy to do something similar in a stock TR3. Get into a low speed corner a bit too hard and you can wind up nearly stopped because the inside rear was hanging in the air; without the rear end ever trying to come out. It can actually be quicker to punch the throttle for some torque-induced oversteer and keep both wheels on the ground.

This kind of stuff is why locked differentials (which also tend to induce oversteer) are so popular with the vintage racing crowd. With a locked diff, you can get back on the throttle sooner after a corner, without waiting for the rear suspension to unload first.
 
Loss of traction in the rear tires, by whatever means, resulting in lateral movement or lessening of understeer is oversteer. Whether you step the rear out a bit or you exit the corner backwards. Using throttle, braking etc... to induce oversteer, in order to counter understeer, is called balancing the car.
 
swift6 said:
Loss of traction in the rear tires, by whatever means, resulting in lateral movement
Click to expand...
If only one tire loses traction, then there is no lateral movement.
 
TR3driver said:
swift6 said:
Loss of traction in the rear tires, by whatever means, resulting in lateral movement
Click to expand...
If only one tire loses traction, then there is no lateral movement.
Click to expand...

...<span style="text-decoration: underline">or lessening of understeer</span>. When you felt your steering become more "neutral" you were generating an oversteer dynamic, even without lateral movement, you still had loss of traction. May have been minimal granted, but it is still an oversteer dynamic.
 
swift6 said:
When you felt your steering become more "neutral" you were generating an oversteer dynamic,
Click to expand...
Yup, if that happened, then that's what it would be. But it didn't, so it wasn't. Contrariwise.
 
If you've never heard this:

Definition of understeer/oversteer......

understeer....you hit the guard rail, wall, other car with the front end.

oversteer.....you hit the guard rail, wall, other car with the rear end.
 
TR3driver said:
swift6 said:
When you felt your steering become more "neutral" you were generating an oversteer dynamic,
Click to expand...
Yup, if that happened, then that's what it would be. But it didn't, so it wasn't. Contrariwise.
Click to expand...

TR3driver said:
my inside rear tire was light enough to spin through almost the entire turn (someone later told me they could see the tire smoke) and yet the steering was very nearly neutral (the other tires weren't loaded enough to even develop much of a slip angle).
Click to expand...
 
And your point is? My Stag is setup pretty close to neutral (I don't like understeer) until you get close to the limits of adhesion. So it wasn't developing any more oversteer (or less understeer).

Took first in the stock class; I later learned that my replacement wire wheels should have put me in the modified class where I would only have gotten second place (running against cars with bigger engines and other modifications). The Stag is by no means a sports car, but I was pleasantly surprised at it's manners on the track.

113_1372cropped.jpg


Especially since I had to stop and buy tires off the rack on the way to the event.
 
My point is that the weight balance has to go somewhere. If one tire is light enough to spin then there is weight being transfered away from it. That weight transfer and all that comes with it is going to have an effect on the understeer and oversteer balance of the car. Neither has to be dramatic or even be obviously felt for it to be happening. Understeer and oversteer are dynamic, not static, and can be effected by acceleration, braking and turning. A car set up to be more neutral will transition back and forth between the two with less drama unless there is another factor that breaks traction, neutral set up cars on wet/slick roads for example, will have very dramatic shifts.

You can disagree, but from what you have described so far, you won't even begin to sway my opinion or differ from my original statement.
 
swift6 said:
That weight transfer and all that comes with it is going to have an effect on the understeer and oversteer balance of the car.
Click to expand...
Not if the weight transfer is equal front/rear. (Or the front/rear difference happens to match the compliance of the tires.)

Which, since there is always some weight transfer from inside to outside, is exactly the condition you have to achieve to get neutral handling.
 
Even with equal weight transfer it will affect oversteer and understeer. How the weight transfer is resisted is how you can control the degree of understeer/oversteer. This is where spring rates, sway bars, tire sidewall construction/size, tire inflation, center of gravity and roll centers come into play. They are all ways to control how the weight transfer is controlled/resisted.

One wheel lifting up though, is not equal transfer of weight front to rear or vice-a-versa. The inside rear tire lifting will load the outside front tire more than the outside rear or the inside front. Less traction in the rear will generate an oversteer dynamic that will help the front steer through the corner easier. Oversteer and understeer are tools when they are controllable, devastating when they are not. The more neutral a car is the more useful they are as tools.
 
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