MG Sports Cars

What size front sway bar are people using on their MGBs?
1".....7/8".......3/4".....?

I need one for my 302 V8 GT with Hoyle front end.

Cheers,
Martyn

The decision is complicated by other factors... What spring rates are you running? What ride height? Do you have a rear bar installed? (Your LE probably does, right?) Etc.

IMHO, very few MGBs should be running a 1" bar, and the ADDCO 7/8" front bar on my GT is probably too stiff for the rest of my current set-up.

I recall that Larry Shimp added a rear bar to his Hoyle suspension 302 powered GT to get it into balance.

I currently have a 7/8" bar. I had to bend it to fit under the engine crank pulley. The rad and electric fan prevented me moving it forward. Now I am fitting a new rad (again) and might be able to fit a straight bar. I have Guzman 4 link on the rear.
Just wondered about switching to a 3/4' bar at this point although the car handled really well with the 7/8".

Thanks!

Carl.....Graeme seems to remember posting a better time on the autocross than you in your car back in 2007 at Willoughby (?).
I was telling him you were asking about him.

Curtis...Looks like your trip to the UK was pretty awesome!

Nothing wrong with the bent bar. They are often bent for clearance. Unless, you now want a straight bar for appearance.

A big front bar will usually require a rear bar to balance the effect.

Tell Graeme that he is far too young to have such a lousy memory! :)

Quote:

Carl Floyd graciously invited some of his rivals to try out his car on the course - just for fun. Out of respect for his need to drive home, probably none of them drove it at "ten tenths". The results were as follows: Bill Yobi 34.82s, Graeme Harvey 35.48s, and Max Fulton 36.56s. I'm not certain, but I suspect the 35.75 time shown above for Cade Schafer's last run might actually have reflected Cade driving Carl's car. Carl Floyd 34.00

[www.britishv8.org]



Edited 1 time(s). Last edit at 11/06/2013 04:12PM by MGBV8.

FWIW, I'm running a 3/4" front and none in the rear on my RD. My belief is that going to a larger front bar might contribute to understeer
.Your GT has a different weight bias than mine...so, If in doubt about a larger or smaller bar, try it!



Edited 1 time(s). Last edit at 10/14/2013 03:10PM by ex-tyke.

I installed a stock bar up front and find it works fine. My car in stock form did not have a front or rear bar. I do not do any auto crossing, just cruise to shows.

Brad

I have the stock '73 bar mounted on the bottom of the extended rad supports with short 3" links going into the bottom of the spring pans, 13 1/2" ride height, and 480# springs and stock shocks with ATF. I'm very happy with the handling with this setup.

Martyn, very complicated. Curtis gave some of the reasons.

Sway bars are suspension tuning tools. There are chapters writing just of sway bars.
I will try to give a general idea, but I would suggest to read on sway bars. The wrong choice can cause the car to be unstable during transition at speed or have to much under steer.

Sway bars have a relation with the springs such as; spring ratio from front to rear. Most cars are set up with 1.7 to 1 spring ratio from rear to front, performance oriented use about 1.5 to1 ratio, racing is 1 to 1 meaning spring rate; example 600 lb front and 600 lb rear (racing rates)is the same front and rear. This set would make the car very unstable, so it is corrected by using sway bars and induce just a little under steer by installing a front sway bar and a small in the rear. I have used 1/2" rear and adjustable to increase the rate.
Also tires have an effect on sway bar size, if you were using racing tires, the traction would be greater and lean, under steer and feel very tight, this calls for higher rate springs and bigger sway bars.

It is a domino effect.

I hope this clarifies some of the reasons to use a sway bar.

The other scenario is street driven car with stock spring rate (factory settings) this becomes a drivers choice, how do you like the car to feel loose, (over steer) tight (under steer) Tires also play a big factor in choosing a sway bar.

Drive the car and feel the car with your hands and butt, have someone take a picture of how much the car leans, the car may feel just right without a sway bar, it may be just right for you.
If it is not, start with the stock sway bar at front 9/16 and go from there, if you get to a 7/8 at front, I would then reduce spring rate in the rear.

My RD right now has 300 lb front 200 lb rear (1.5 to 1 ratio) with a 3/4" front bar with longer arms which reduces the bar rate due to leverage, the effective rate is the same as a 9/16"

When I was testing I used a 1/2" adjustable rear bar to the minimum rate hole in the bar. The rear sway bar on the street would be to loose and dangerous at hwy speeds during transition or an emergency maneuver.

First you need to know what you have.

Thanks Bill. Information much appreciated......as always!

On my '68 roadster with a mild performance 1800 and the stock rebuilt suspension, I started autocrossing with the stock 9/16 sway bar. I found the car had way too much body roll and would lift the inside rear tire in turns, thus losing all forward accelleration and generally "sucking" as a handling sports car. I then instralled a 3/4 sway bar and it literally transformed the car for autocrossing. Much flatter in the corners, no lifting of the inside rear tire, much more predictable transitioning when changing directions, better able to throttle steer. It sounds like I'm exaggerating, but I'm not. Our autocrosses are different every time, so I can't compare before and after times, but the car is much faster. All from the heavier bar.

Now, I can't say there is any advantage to the 3/4 bar for street driving, but I didn't find the ride to be any harsher either.

Better results would had brought to you if you had installed a 1/2" in the rear.

In a road car the choice of bar often seems dependent on driver preference: do you hate the ROLL more, or the understeer?

I've found tires to be crucial as well. The wider tires hide a multitude of sins (until in the Wet!). You almost want to balance your handling on skinny tires (more sensitivity) and then put the wider rubber on.

Ride height is also a factor. Lower the car, the less front bar you need.

Overall suspension set-up is a factor as well: better shocks and better spring rates allow the independent front to do it's thing. When you install a sway bar, it's no longer independent! Ideally, you wouldnt want to use a bar!

For a road car, I like the lightest sway bar that accomplishes what you need (less roll, less over/understeer, etc.)

Usually a 3/4" front bar is flirting with needing a rear bar to balance it, and 7/8" and 1" demand it.


The racecar runs 1" front bar (which will BREAK stock links, btw!) and fabricated 9/16" bar (with short links) in the rear. This seems to give, when pushed hard, a mild bit of understeer....

$.02

M

I used to run the GT bar on the front of my '71 roadster and no rear bar. It had 1" lowered springs and smaller diameter tires (24"). Roll was not a problem and handling was neutral.

Now of course everything will be changed. On the MG-Roadmaster we have no front bar, but of course it has the Jag IRS. The handling seems to be pretty balanced but there is a good bit of roll.

Jim

Max, you comments are really interesting. Understeer is definitely more of a problem than roll with my '68. However, I think it would be about perferct if I would pony up for some stickier tires. I wish I had the opportunity to do more autocross/speed events with my cars. It's hard to justify much for 3-4 autocrosses a year.

Ryan, generally speaking as a guide to tuning it may be said that adding a sway bar decreases grip on that end of the car. So to decrease understeer you would add a rear bar or decrease the size of the front bar. What size front bar are you running?

Jim

Max, good points. Tire grip changes spring rate and bar. Everything has to work together, springs, bar/s, tire compound,wheels, bushings and driver. Some times the rubber bushings work better due to deflection.

As your post states, the bar brakes the stock links, well yes, more forces are channel through them. Sway bars links play a big role with the bar stiffness.

The best set up to start with a a road car is with the softest spring rate and big bars, this way you a get a good ride and handling, that is one way and one of the favorites of many manufacturers. The other side is to use the a high spring rate and small bars, one will give a better ride and the other will give you a stiff ride, both will produce the same effect on the road. That is for the masses, then each driver will tune accordingly, one reason why the aftermarket of performance parts exist.

What ever is done to the front affects the rear.

Spring ratio front and rear is also important in a road car. Usually road cars (stock) come with understeer for safety reasons.
So just add a big bar to the front, is only inducing more understeer, but in some cases drivers like this type of set up.

It takes hours, days to tune a suspension and parts to get it the way you like in a race cars, then tune for different tracks and driver, is not all about power. A race car is a combination of both and many other factors.

Somebody broke a stock sway bar link at one of the early MG V8 Meets. I carefully spot welded mine, trying not to melt much of the rubber inside.