• Hey Guest!
    British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
Tips
Tips

TR 3/4/6 -try to talk me out of this: [suspension]

Share this page

Willie_P

Willie_P

Jedi Hopeful
Offline
I have a '62 TR4 going through a full restoration (self performed). I am now in the final chassis assembly and should have a "roller" by Dec 15th.

the front end will be lowered by at least 1", but could be as much as 1.5" (I don't have the suspension fully loaded yet, so don't know for sure).

Anyway, I want to eliminate bump-steer characteristics and complement the lowered front end of the car. Also, I will be using the car at most once a week for spirited back-road driving (Western PA, OH and WV country roads that range from smooth to rough and crowned) and the occasional autocross.

Here's what I am considering and need counterpoints (or a good strong...go for it!):

Rather than bend old tie rods, buy chrysler OEM steering arms,slotted TR6 control arms, etc as suggested in several hop-up articles (GRM/Classic Motorsports); I found CNC heat-treated "bump steer" kit available through several dirt-track and autoX mail order houses (Speedway Motors is one). Anyway, this are basically extender pins that have a tapered end that fits into the steering arm and then the extended shaft meets the modified position of your tie rod end (as due to the lower stance).

In doing this I'd also like to use heim-joints (rose joints) as opposed to the OEM/TR ball joints.

Most (if not all) of the extender/bump-steer pins come in either Pinto/Mustang II (7degree taper)or late-model GM (10degree taper), which from my crude measurements would require reaming the TR steering arm hole to match (TR appears to be roughly 3degrees - pls correct me if I am wrong).

I guess I am really asking two questions here; first being - do you like this way of reducing/eliminating bump steer (the pins). Second question - what do you think of using heim joints instead of the original ball joints (and further, should I use high-misalignment heim joints instead of regular ol' heim joints).

If it matters any; the entire front end is polyurethane and I am running a tr6 sway bar with reinforced frame mounts. I am also replacing the flex mounts in the steering column/shaft with universal joints.

i look forward to your remarks: -wp
 
Bump steer comes from altering the relative height and position of the tie rod pivot compared to the A-arm chassis pivots. (This is of course assuming un-altered steering arms). It's ok to lower the car a couple inches as long as there's no binding of any steering / suspension parts (like ball joints, tie rod ends). Bump-steer will not be a factor if modifications are limited to this. Bending of tie rods and tie rod ends is absolutely prohibited.

This "bump steer kit" is something questionable in my opinion. What exactly does it do?

Using Chrysler steering arms sounds like you are trying to lower the tie-rod-end position to compensate for the relatively higher position of the suspension. This will affect the relative angle of the A-arms and the tie rod. They MUST be kept parallel in resting position. The only way to compensate lowering the tie-rod-end position is moving the steering rack down, then you have exactly the same situation as if you left it alone in the first place.

"slotted TR6 control arms" can change a lot of parameters in the suspension depending on how they are slotted. Please explain.

This car works just fine regarding bump steer.
TR4c.jpg
 
I'll digest all that as I get time; but I am getting the impression that you (@racingenlishcars) don't really think bump-steer correction devices are necessary if only lowering your car 1" - 1.5"; accurate restatement/paraphrase?

willie
 
Willie,

It's something you have to measure when you get your final ride height. Usually you just shim the steering rack. Be careful that it's mounted really well though. That's the last part you want coming loose.
 
I have the vertically-mounted steering rack (not the one that lays horizontal to the ground surface). (i.e. - the u bolts face the front of the car as opposed to pointing upward toward the sky).

So, to my knowledge, you cannot move it up or down.
 
The simplest description of the cause of bump steer is when the tie rods are not parallel with the line intersecting the lower control arm pivot point and the lower ball joint. When they are not parallel with each other this causes the toe to change as the suspension moves through its range of motion.
If you want to change your ride height you have to go with drop spindles, which I haven't seen available for these cars,
or go with a lower spring height.
 
Lowering my TR6 has caused a couple issues. First, I have a lot of negative camber. I have tried a few things to correct it, but will be soon installing some adapted stock control arms with a heim joint for adjustability. Second is ground clearance. I installed Goodpart springs that are considerably stiffer than stock. You will want shorter heavier springs to reduce height and travel.
Are you a member of the Western PA Triumph Assoc.?
 
Doug-

We've met before over at one of Roy's spring tune-ups. I referenced the slotted upper control arms earlier in this post which I heard can assist in reducing the negative camber (there's a good classic motorsports article on this subject).

I talked to Bruce recently and will probably consult him further re: lowering of early tr4.

FYI - my car was purchased from Ed Woods and Jerry VV a number of years ago.

I just rec'd a big parts stash and Dexter and I will be working on the car over the next few weekends over at my place in Sq. Hill.

wes
 
Willie, seems like you're making rather major mods to the suspension for a street car (and occasional autocross).

Have you driven a well-sorted TR-4 with period-correct suspension mods? They handle pretty well, considering the technology.

I suggest that you drive a nicely sorted TR-4 before you go to all the trouble and expense that the above mods represent. You might just like it the way it was intended to be set up from the factory.

And, you'll save a pile of money . . . :yesnod:
 
Sorry Wes, didn't realize that was you. I'm sure Bruce or Fred would be able to help you out. Don't know what mod. differences there are between the two cars.

Bruce did say that his handling has improved considerably since installing the new control arms.
 
Your right "trunnion". I'm sorry I don't have a lot of experience in particular with these cars. I spent a lot of years in the collision business doing frame and unibody straightening and wheel alignments. Bump steer is from a suspension mounting point or steering linkage misalignment.
Changing the length of your upper or lower control arms will
change your caster and or camber but to avoid bump steer they and your steering linkage must be parallel to each other . My TR3 has spacers in the front suspension. If I were to lower it. The easiest and safest thing to do would be remove or use smaller spacers. Maybe you could try something like that. I'm not sure what springs would crossover from model to model. If you car doesn't have spacers maybe you could order a shorter set or just cut down yours.
 
Without having it in front of me, I recommend reading the article that Bill Babcock wrote on setting up TR3 front suspension (very similar to TR4) for racing. The article can be found in one of Kastner's books.
 
@vagt6:

I drove my car and others for a few years, and do like the "compliant" ride, but I'm young...30's - got a penchant for looks, and I do kinda dig the "slammed" look to the extent it won't totally ruin handling, but I swear these cars look like 4x4's when you can stick your entire fist between the fender and tire topside.

I am also using alloy lowering blocks in the rear.

MgB's (which i've owned two) always seem to ride lower (height) which is nice.

I like the tr4 photo earlier in this post - but think it's a little too low for reality of handling backroads.

there's a happy medium out there (handling AND stance) and I am gonna give it my all to achieve it!
 
Thats a good article but it sounds like they made alot of static measurements. If you are going to measure these angles
they should be done on a level surface with a set of turn tables to take any load off the suspension. The runout of the wheels should be taken into account also. There a lot of variables and a lot of play these suspensions. Thats why rear wheel drive cars are set up with "toe-in". As the car goes in motion the front wheels are being pushed and tend to "toe-out".
 
Willie_P said:
over at my place in Sq. Hill.

wes
Click to expand...

That's the area where I grew up - 217 S. Homewood Blvd. Now the admin building for the Frick Museum.
 
JFeher said:
Thats a good article but it sounds like they made alot of static measurements. If you are going to measure these angles
they should be done on a level surface with a set of turn tables to take any load off the suspension. The runout of the wheels should be taken into account also. There a lot of variables and a lot of play these suspensions. Thats why rear wheel drive cars are set up with "toe-in". As the car goes in motion the front wheels are being pushed and tend to "toe-out".
Click to expand...

I trust Larry did that.

Granted, bump steer is something that should be measured on every car, individually. These cars aren't perfect and there will be some minor differences.

Larry's article hits the gist of it, but each car is going to need some fine tuning.

Most racers either just bend the arms or move the steering rack. Do whatever works.

On springs, this is a pretty complicated topic. It depends on multiple variables including; use, weight, ride height, tire (sidewall spring rate and how sticky they are), and the motion ratio of the suspension. You want something that's as least as stiff to keep from bottoming out under <span style="font-style: italic">steady state cornering</span> (sharp bumps are a different story and that's what progressive bump stops are for).

Shock valving is the last thing to be adjusted as they are tuned for everything, including the spring rate.

There are two different camps in racing as well. Soft springs / big swaybar or stiff springs / small sway bar. It gets pretty complicated.

Here is a picture showing the set the car I crew on takes under very hard cornering (toe of Watkins Glen) https://public.fotki.com/colin1944/watkins-glen-vintag/p1030514.html
 
Back
Top