View Full Version : panhard bar for tr4-where to locate & mount

02-26-2007, 06:55 PM
hi all,
i'm planning my tr4 with the thought of installing a panhard bar. has anyone done it in a tr4 solid axle car? where should it be mounted and what is the suggested roll center height? (lsd with anti-roll bar in rear)

02-27-2007, 04:10 PM
and the car is being used for ________________?

02-28-2007, 11:13 AM
hot street,autocross,possibly club racing.

03-01-2007, 07:22 AM
The panhard rod should be as long as possible and, when the car is loaded and in motion, it should be parrallell with the rear axle when viewed from behind AND when viewed from above. For practical (space) purposes, it will also need to be very close to the rear axle, but it must not hit or bind against the rear. The pictures below are from my Spridget, which is conceptually similar to your car (I built it based on pictures from Peter May Engineering...a Spridget vendor). The arrows are pointing at the rod ends at each end of the panhard rod.

I believe that Rimmer Brothers may have one for your car, but you'll have to call.

Hap Waldrop has also mentioned a "triangle brace" that he uses instead of a panhard rod (on Spridgets). I have no info on this, but it sounds very promising. You can contact him for more info:

Generally, the best thing to do with roll centers is to get them the same (front and back). This is not really simple on a street car. The best way to spend your time is to get the car as low as practical, get the bump steer set up properly and have a good alignment with about 2 to 3 degrees of negative camber in the front. If the car is to be used for street and track, your ride height will obviously have to be a compromise.

I am not a big fan of rear sway bars on live axle British sports car. The best suggestion I can say is to be sure it isn't too thick and mount it in soft rubber bushings.



03-01-2007, 11:40 AM
The panhard rod should be as long as possible and, ... I am not a big fan of rear sway bars on live axle British sports car.

My TR3 racecar came with a panhard rod installed, but I removed it. It was short, and, as Nial says, a panhard rod should be as long as possible.

Ken Gillanders of British Frame and Engine says that if you use his rear spring locating kit, you don't need a panhard rod. This is what I did.

Paddock Wisdom says that you should eschew a rear sway bar on a live axle Triumph. Eschew it into a trash can.

03-01-2007, 03:30 PM
""""""hot street,autocross,possibly club racing. """"

well until you get to the "possibly" deal you might just make sure the end bushings on the spring packs are like new, the u-bolts tight and hose clamp the leaf packages front and rear of the housing.

Add a panhard bar if you have more lateral movement than you want on hard cornering.

The lower you attach the horizontal bar , the lower the roll center. The down side then, is the chassis bracket on drivers left gets longer and needs more thought. Prolly 2" lower than the horizontal c/l of the axle tubes would be about where U want it. Coupla vertical adjusment holes up and down make sense too.

""""""" Eschew it into a trash can."""""""

or in a handkercheif....... unless the car needs balance.

03-09-2007, 03:13 PM
I am not a big fan of rear sway bars on live axle British sports car. ......

I do use a front and rear sway bar on my TR 4.
I have very equal tire wear. My first set of racing tires lasted 2 years.
My current set has now 3 races done and 3000 mls every day traffic and not much wear at all.

If I compare my car to the "no rear sway bar" cars than it should be an advantage. Lap times show it also.

03-14-2007, 02:57 PM
I found some drawings of a panhard bar installation when I was looking for the radius rod drawings for PeterK. They're in Technicalities Volume One published by The TR Register.

I'll write the same thing to you that I wrote to PeterK:

There are no dimensions on the drawings, but you could probably figger something out for yourself. I could copy the drawings and snail mail them to you, if it's not breaking any copyright laws to do so. Or if you don't tell on me

Hap Waldrop
03-16-2007, 07:01 AM
Here's a picture of the Huffaker MGB during the restoration.
As you can see we're not quite done. You'll see the black mount for the panhard bar on the driver side and the hook up on this end for the bar under the spring mount, we have mounted the bar yet. It runs as Jerry mentioned , below the axle tube for a lower roll center. Here's a second picture this is of the Huffker watts link that is on the Huffaker Bugeye I drove, nice but way too elobrate and took a good bit of sub structure to mount it. Then there's the wishbone I discussed earlier, we have one of those on a customer's vintage Midget, same rear pick up point, the drain plug in the rear end housing, the wishbone is a simple set up that requires less sub structure to mount it. If you running a panhard bar on a Midget or MGB, at the center the car the panhard bar should pass by the drain plug of the rear housing at about the level of the drain plug, this is the roll center you should be looking for.

As for a rear sway bar, to each their own. On my racing Spridgets they are so stiff, that if I tried to run without a rear sway bar, I just lifted the inside fornt tire in a corner to the point the weight tranfered too much to the outside wheel and induced a push, making me slower in the middle of the corner, installed the rear sway bar, the inside fornt tire stayed planted, not nearly as much weight tranfer, no push, went a bunch faster. I like rear sway bars, but different cars do behave differently, but I never drove a race car that didn't go faster with me in it with a rear sway vs without one.

03-16-2007, 07:49 AM
Hap's second picture is a treat to the eye....nice work!

And it also points out the compromises that need to be considered with questions like this.

As Hap says, his car is super-stiff. This means there is less useable wheel travel (especially at non-racing speeds). So, the shorter, angled panhard rod allows a design that can focus on lowering roll center. The short rod may also push the axle left-right as it travels up and down, but that is less important, since the afformentioned wheel travel is pretty limited anyway. I have a friend who has a Lotus Seven with the same type of panhard rod.
I think that Seven has something like 700 in/lb springs in the back. /bcforum/images/%%GRAEMLIN_URL%%/shocked.gif

On semi-street cars (and my endurance racer) with softer springs and more wheel travel, the short rod might cause some weird side shifting in bumpy corners (although hopefully, race tracks have smoother corners).
So, going back to the original question, it depends on which way you want to compromise.

And I still like that wishbone deal too.....really a clever idea.

Speaking of clever ideas and roll-centers, one of the neatest Spridget axle setups is the live-axle Mumford link seen on Mallock race cars (below).
~CLICK HERE~ (https://www.not2fast.com/chassis/mumford.gif) for more info on the Mumford link.


Hap Waldrop
03-18-2007, 09:19 AM
That Mumford link looks a little bit overkill to me, too much going on, too much stuff, this is why I'm not a big fan of the Huffkaer horizontal watts link, too much sub structurre to mount it. I tend to lean towrds the wishbone or my favorite just a good old panhard bar set up. The first thing that comes to mind with the Mumford link is that running the exhaust will be a much harder chore. I think the key is to achieve lateral support with as little structure as you can to save weight.

04-18-2007, 02:31 PM
Just a further note to all,
the axle in a tr4 is ABOVE the frame and makes mounting to the frame VERY easy,light, and rigid to mount. I plan to relocate the front upper a-arm mounts to get the optimal roll center up front to go with the rear for neutral handling if possible. It also gives a tuning tool.

04-18-2007, 02:53 PM
where do you move it?
down, in, out, up?
You also could insert a anti dive with tilting the A-arm


04-18-2007, 05:48 PM
upper front arm mount on tower- in and down. revinton tr upper fulcrum relocation part RTR3112K or custom fabrication.

04-19-2007, 02:14 AM
Wouldn't give that too much camber at full bump?

04-19-2007, 10:47 AM
depends on the length of the upper control arm. I'm still working it all out.

05-08-2007, 05:37 PM
depends on the length of the upper arm. if one shortens the upper arm you end up with a bad camber curve.

05-08-2007, 10:58 PM
I am about to modify my upper arms as well. I tried slotting the holes that attach the uper bal joint but that does not give nearly enough. The inner bolt looks like it needs to be about 1/2" past the mounting boss available on the inside of the front upper arm. Have you detrmined how far in and how much lower you are going. How about details for the custom fab?



05-09-2007, 02:01 AM
depends on the length of the upper arm. if one shortens the upper arm you end up with a bad camber curve.

I have shortened the upper wishbone. The only trouble I figured out is when the suspension is full out then there is too much negative camber. But from ride height to full bump the camber gain is perfect and the bump steer is very small.


05-23-2007, 01:12 PM
this is not easy to determine since it is specific for each car,set-up, ride height,springs,tires,weight distribution,rear roll center,center of gravity,weight transfer, distribution etc. I am still working on it though.my numbers won't work for someone elses car unless it is EXACTLY the same including tires and wheels(which i doubt anyones will be the same as mine).I am not building to rules but will be stock "appearing".