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MG MGB Technical - Sway Bar Size

Does anyone have personal experience with an early MGB and a 3/4" sway bar?

I scoured the archives and didn't find an answer to this question specifically. I'm about to replace the stock sway bar on my '65 B with a larger size. I'm going for both performance and ride quality, with the emphasis slightly to the performance side. Right now the car handles incredibly neutral and I love it. But body roll is severe and I can tell the sway bar is not a good match to the rest of my set up.

Here is what I have now, and will still have after the rebuild:

Superflex Bushings
Stiffer shock valves
15" x 72-spoke Wire wheels
195/60R15 Tires

Keeping in mind that a '65 has no rear sway bar, would a 3/4" bar create too much understeer? I have a 3/4" bar on my GT right now and it feels very nice. I know the GT is heavier but only by a couple hundred pounds.

Any input appreciated!
Steve Simmons

I'm using a 7/8ths front anti-sway bar with my V8 conversion that has poly bushes and uprated front springs,and it works well. I still have a small amount of oversteer so would go for a thicker bar if I could get one. The rear springs are around 90lbs/inch.
The car was a rubber bumper, however I've changed the bumpers and lowered the car to chrome bumper height.
I lowered the back by a combination of one inch blocks and redrilling the spring hanger holes. The springs have sagged just a little over the last 50 thousand kilometers so last month I moved the spring holes back to the orrigional location. The back now sits up about half an inch higher than the front. Rather oddly the grip in the corners has improved quite a bit. It is that extra bit of roll in the back that is helping. It lends credence to those who take a leaf out of their rear springs to improve handleing.
P.N. Sherman

Hi Steve:

Heres what I have on my 73 mgb roadster:

Original dampers in good condition
CAHT-21 springs (lowers front by 1 inch from stock, stiffer spring rates).
V8 bushings
New upper and lower bushings
Kingpins not rebuilt, because they have virtually no slack.

Rear springs standard, but de-arched to lower rear of car 1 inch from stock.
Standard but fairly new rear suspension bushings.
Original dampers in good condition.

14 inch stock wire wheels 4.5 inches wide,
185/65-14 moderately sticky tires.

At the time I rebuilt my suspension to the above specs, I ordered an Evolution II front and rear sway bar kit, but the rear bar was not available at the time, so I installed the front bar, which is 7/8", not 3/4".

On my car, the front bar alone appeared to transform the handling of the car. The year before, I was usually 4-6 seconds behind the fastest B in our club at slaloms. With the new bar (plus the other front-end mods), I was at most 2 seconds behind at slaloms. I did not notice excess oversteer, understeer, or bump steer.

Then a year later, the rear bar arrived. I only noticed a marginal improvement once I installed it - the front bar appeared to have a much greater effect. I have to admit that I did a bunch of front end mods at once, so can't say it is the front bar alone, but the car handled much flatter under hard cornering (although likely the stiffer springs helped that too) with the front bar alone, and hardly changed with the rear bar added.
When I installed the moderately sticky tires after the rear bar was on awhile, I was neck and neck with the fastest B in our club.

My car handles incredibly. The ride is not harsh. The steering is positive but not twitchy. I don't have oversteer, I would say that I now have slight tendency to understeer, but less than the stock B tends to have. I am now looking forward to possibly some Minilite-like wheels with Yokohama AO32 tires to be the icing on the cake.

My conclusion is that adding the uprated front bar only made a big difference. The lack of the rear bar did not seem to be a problem. In your case, with a 3/4" bar, you'll have less difference betweeen front and rear than I had, and I found the result much better than stock.

Paul Hunts pages were helpful to me - www.mgb-stuff.org.uk, as were Doug Jacksons pages http://www.mgbmga.com/tech/mgb14.htm

Hope this helps. My bar being 7/8" not 3/4" doesn't allow us to compare directly, but I think you'll like it. If not, its simple enough to return to stock.

Erick
Erick Vesterback

The front bar is definitely the biggest improvement of the two. One thing to keep in mind is that early cars have no provision for a rear bar. Therefore going too large in the front will result in understeer which is difficult to remedy.

Rear bars can be installed, but I have rarely seen a good report on a rear bar on an early car. Even on the race track most early cars run no rear bar at all!

The stock bar on a '65 is 9/16. Therefore the logical choices are 5/8" and 3/4". I'm just concerned that 5/8" will not be enough.
Steve Simmons

I have just taken a rear bar off of an early car. They tend to make the rear end too twitchy for road use as bumps in corners throw the rear end into the air and thus sideways.

The factory tried a rear ARB on the early rubber bumper cars to help control roll but removed it again after a year or so.

The accumulated wisdom on MGB handling is to stiffen the front and leave the rear standard and soft.
Chris at Octarine Services

I have a 7/8 front bar on my '74 'BGT. This with Spax adjustable dampers and 205/50-15 sticky tires did .98g on the skidpad. Some of those laps were on three wheels, with the inside front dangling in the breeze. I've since added a 3/4 rear bar and now all four wheels stay on the ground, most of the time. It has instant turn-in. It can be a nervous-feeling car, but with street tires and the dampers on "soft" it's ok to drive on the street. I don't know that I would feel the need for a rear bar on a roadster, but it helped my GT. My MGA Coupe feels fine with only a front bar. If I can compare the two, the Coupe is less likely to lose the rear under certain conditions.
Kemper

I have a '73 with the standard bar (9/16"). I've got a 5/8" bar from a later car waiting to go on. Anyone made this upgrade and what thoughts? With standard rubber bushing? How about with solid mounts to stiffen things up?
Derek Nicholson

3/4" bar create too much understeer?

In general arbs reduce grip at end fitted increase weight transfer. However they also control camber change which should give better grip at front but not much use for a live rear.

As Chris stated above stiffen and adjust at front and leave rear soft is tried and trusted.

Arbs are only part of the overall package but some fine tuning can be made by adjusting tyre pressures
Paul Wiley

Let's see if I have this right, if you have a soft rear then size does matter? ;-)
Bill Young

I tried a 5/8" bar on my 74 roadster and it required more steering lock (increased under-steer) on the curved roads I normally drive. I prefer the standard 9/16" bar for my driving. I also tried it without a bar and I believe it handles best without a bar, but it does have more body roll with no bar. I have V8 bushings in the inner wishbone arms and Super Pro bushes in the upper and lower trunions. Sway bushes are stock.

Clifton
Clifton Gordon

Derek,

I made the slight change from 9/16 to 5/8 bar on my 1972, and installed V-8 bushings and was moderately pleased. I only use the car on the street, back roads that are occassionally rough from frost cracks. This winter I installed the purple SuperPro bushings in the upper trunions, can't wait till spring to try it out. The improvements were small, but noticeable. For my taste, I am happy with the balance of the car.
Joe

Have a 1" on the front and a 5/8" on the back of my 72B and love it. Rebuilt shocks on all four corners with uprated valves and V8 bushings. Mild oversteer-just the way I like it
gerry masterman

Where did you get your one inch sway bar Gerry? Custom?
P.N. Sherman

My 74 chrome B has v8 bushings and the stock bar with stock bushings. The front springs are new but stock. The rear leaves are from the 79 but worn. The shocks are all stock but the rear shocks leak so are always low on fluid. The rear axle is from a 79 but I did not use the rear bar. It handles great on the road and much better when the rear shocks are full.
Something to consider for discussion: Some of us may have made changes from stock at the time of building a car or when the cars original parts were worn so results must be considered to the liking of the driver and not compared to new stock.

Yes, I tried the trick of using mineral oil in the rears but they are too worn so they still leak. I may get them bushed or replaced if the money is ever there.
kids1

Have you tried ATF in the rear shocks? It sure swells the rubber in a M/C if it's added accidentally. Guess how I know?

Derek Nicholson

I have found the 3/4" front bars work well for aggressive street driving and slaloms. I use 7/8" for racing, and while I ised to run a rear bar, I found that when I went to the Quaiffe diff it handled better with no rear bar.
Bill Spohn

Derek.. Seals in the rear shocks? Are tehre seals around the shafts where they turn in the casing?
kids1

Bought my 1" bar as part of an "Evalution 2" kit off Ebay 6 years ago. Don't think is is made any more. At one time I think Brit Tek sold them
gerry masterman

You can also control body roll as well as keep all 4 tires on the ground (inside tire picked up by the roll bar) by increasing the spring rates. This might hurt the ride a little, but the car should handle better than just adding roll bar(s). I autocross my 73 B with a stock suspension with the exception of 550# front springs and 5/8 roll bar (stock for RB cars) and eat Miata's for lunch! As long as the road is smooth, the old coal cart suspension of the MGB is hard to beat!

Gregg
G Hanks

This thread was discussed between 23/02/2007 and 27/02/2007

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