PDA

View Full Version : TR2/3/3A Panhard or Rear Sway Bar on aTR3?



karls59tr
02-03-2010, 03:23 PM
What's the difference between a panhard rod and rear sway bar? Which one is that on Pied Lourde's TR3?

Twosheds
02-03-2010, 04:13 PM
A panhard rod keeps the rear from moving left-to-right as the car corners.

A sway bar increases roll stiffness.

martx-5
02-03-2010, 04:20 PM
Panhard Rod... (https://en.wikipedia.org/wiki/Panhard_rod) Laterally locates the rear axle.

Sway Bar... (https://en.wikipedia.org/wiki/Anti-sway_bars) Is actually a torsion bar between the right and left side that increase the spring rate in turns to help keep the car level.

Edit: twosheds was quicker on the draw...

Twosheds
02-03-2010, 04:32 PM
Ah, but Art has links!

Moseso
02-03-2010, 04:51 PM
Thanks for the link! Tabcon posted some tasty pics of a Watts Link arrangement he made for his car, and I wondered what the heck it does. Now I know...

karls59tr
02-03-2010, 06:37 PM
Quote from "Vintage Racing" by Terry Jackson:There is some disagreement whether a rear sway bar is needed on early TRs. Many racers say that adding a sway bar only increases the the natural understeer of the car. Some such as Hedke have added a 1/2" bar at the back with good results. Try a small bar but dont be surprised if it does more harm than good." Anyone running a rear sway bar on their TR3?

TR3driver
02-03-2010, 07:15 PM
Anyone running a rear sway bar on their TR3? I had one on TS39781LO for many years (in combination with a front bar, of course). On the street, I felt it improved handling overall, in the sense that I could no longer find that point where the car would suddenly transition from understeer to oversteer and, as Car & Driver put it, "bumble off backwards". However, on the autocross track, I felt it slowed me down overall, because it increased the tendency for the inside rear tire to lift and not be able to put power to the road coming out of a tight corner.

IMO the proper solution was a stiffer front bar (perhaps combined with some suspension mods to raise the front roll center); but I never got around to trying that. A limited slip differential would help a lot, too (got two of them on order <<GRAEMLIN_URL>>/grin.gif )

M_Pied_Lourd
02-03-2010, 07:33 PM
Karl,

As you know, there is one on mine. I would add that is was installed on my car when I bought it along with a very beefy front sway bar. This car was a vintage racer for most of it's later life.

According to the racing log books that came with my car it was first raced on May 26th, 1983 at Second Creek Raceway (North of Denver, now closed it looks like) and finished it's racing career on July 11th 1998 at La Junta Raceway CO.

I am assuming that after 15 years of racing that the rear sway bar set up on the car must have worked well.

I have yet to drive the car so I can't comment as of yet. I will be interested to see what others have to say on the subject however.

Cheers,
M. Pied Lourd

bgbassplyr
02-03-2010, 08:41 PM
Just to mess with your mind, think about a Z bar. This is a bar in a Z shape with the ends mounted in the normal sway bar locations on each leaf spring. A normal sway bar, when loaded in a turn, tries to counter the body roll by lifting the opposite end of the axle. A Z bar on the other hand, tries to force the opposite wheel onto the road.

Never tried it on a solid axle car, but on a swing axle (VW-
formula Vee), it works really well. Just look at the races and championships won by Zink Formula Vees in the 60's that were delivered equipted with a Z bar.

OK, talk me down...........

PeterK
02-03-2010, 08:47 PM
And then there's TractionMaster bars to stop spring wrap-up. I have an old set (refurbished and ready) but I still haven't decided on the front attachment point.

TR3driver
02-03-2010, 08:56 PM
Or, another way to put it, a Z-bar lifts the outside wheel. In effect, it reduces roll stiffness, without changing basic spring rate; while a sway bar increases roll stiffness.

Certainly would do nothing to solve the problem I was trying to solve; which is that the TR3 rear suspension lacks enough rebound travel. With the factory setup, in a hard turn, the inside wheel runs out of travel and hits the frame. The sudden impact is what upsets the car's handling so badly ... if you are lucky, the rear end just 'steps' sideways as the outside tire loses traction (due to the full cornering force being suddenly transferred to it), which unloads the inside spring and allows the inside tire to sit back down. It's a rather amusing effect actually, if you are expecting it.

Since the Z-bar reduces roll stiffness in the rear, it also increases understeer (which IMO a TR already has plenty of, especially if you are running a front sway bar or have increased the front spring rate).