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MG MGB Technical - Front Sway bar upgrade???
|Anyone had their stock front sway bar upgraded on an mgb roadster?. Just got my new project '73 MGB on the road and started to enjoy the open air driving experience but noticed right away I FEEL like I need to upgrade my front sway bar. Would poly-urethane bushes stiffen them enough or go with a thicker sway bar?...how thick? I'm not going to race it just good corner handling traits. Thanks.|
|J P Wyc|
|A 3/4" bar will make a worthwhile improvement and is ideal on a road car. It's a very common upgrade. Over here in the UK the 3/4" bars are hard to get at the moment as whoever makes them seems not to be working presently. Maybe its different in the USA.|
If the handling of a car is already well-balanced, then the addition of a stronger front stabilizer bar alone should result in more understeer. On the other hand, I think there are other resulting factors, such as in the case of the issue of traction, that may not be apparent when such general rules are too broadly applied. The premise for installing a larger front stabilizer bar that is not balanced by the addition of a rear stabilizer bar is predicated on the increase in camber that occurs during body roll. The greater angle of body roll permitted by a smaller, weaker front stabilizer bar yields a positive (+) camber increase that is not negated by the negative camber increase that occurs during suspension compression, thus reducing traction in the outside tire. The load on the outside tire is increased by increasing the diameter of the front stabilizer bar, but by reducing the angle of body roll, resulting in less total positive (+) camber increase, thus yields a net increase in front traction attained at the price of increased understeer.
Many manufacturers of stabilizer bar kits offer their products in standard diameters such as 9/16”, 5/8”, 3/4”, 7/8”, and even 1”. However, this does not mean that all bars of the same diameter have exactly the same torsion spring rate. This is dependent on what alloy they are made of and to what level of hardness they are taken to during the heat treating process. This is why it is so important to get them in sets from the same supplier, preferably one of established reputation. Naturally, these cost more than no-name imports from God-only-knows-where in Asia. Quality always costs more. Generally speaking, cheap stabilizer bars increase their resistance much more slowly as they twist and have a shorter service life. If the quality control fails during the heat-treating process, they may even be prone to breakage.
Chrome Bumper models (1962-1974) and Rubber Bumper Models (1975-1980) each require different stabilizer bars. This is due to both the differences in weight and ride heights of the two versions of the car requiring different length arms and slightly different geometry for the stabilizer bars. It is important that both sets consist of a pair of front/rear mounted stabilizer bars with rates that are balanced against each other. Perhaps the most practical combination is a 7/8” front stabilizer bar and a 5/8” rear stabilizer bar as used by racing legend Joe Huffacker.
Make sure that the pair that you purchase have the ends of the front stabilizer bar forged flat and have the mounting holes already in them.
|I would really recommend the 7/8ths or 22mm front bar. I was using a 3/4 but I found I had significant oversteer, particularly in wet weather when the tyres were not gripping quite as well. The back would really want to step out, fish tail etc. Now the car corners very flat, with no oversteer (or understeer). Perfect.|
The ride comfort hasn't been effected by the change from 3/4 to 7/8th.
Most MGB's have a little oversteer, primarily because (I think) of the much heavier (and stronger) Salisbury differential that replaced the lighter and weaker banjo diff'
My car is '75 V8 conversion. It was a rubber bumper car but has been converted to chrome, and lowered to chrome bumper height. 15 by 6 wheels with 195 by 60 Michelin tyres. The gear box is a toyota supra box and is about 25kg lighter than the old one. This makes the front end a little lighter. I've put on the lightweight fibreglass springs at the back, which makes the back a little lighter by about the same amount. I'm using antitramp bars and a panhardrod.
Of all this gear, the antisway bar made the most difference
The weight distribution front to rear is 50/50.
|I should add, I don't use a rear stabilizer bar. For cars at chrome bumper height all that is doing is lifting the inner tyre off the ground and reducing grip potentialy leading to snap over steer. A very scary event I experienced prior to adjusting the rear bump stops to the new lower ride height. Rubber bumper cars seem to benefit from a rear bar, however they have got 50 lbs of "rubber" bumper at each end and are 2 inches taller. Which is quite a handful to deal with.|
|The 3/4" front anti roll bar is well worth fitting and bery easy to do. I would not change the bushes on a road car the larger dia ARB does all you need without degrading ride or the amount of road noise you get. And as noted above, this has to indicate that a stock MGB oversteers.|
3/4 is the way to go . A7/8 bar is just a bit big for an otherwise std. B and you would find it a bit jittery on the road and if driven in anger the old understeer comes with a rush. Having said that I have driven a late B with a rear swaybar and 7/8 bar on the front and the handling was quite neutral but driven to the limit it was the front that went first. I'd go 3/4 Gary
This thread was discussed between 17/08/2008 and 18/08/2008
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