Adding a Sway Bar to the IRS
Remarkably, few MGB's had rear sway bars. No vehicle today would ship without one, especially a sports car! The sway bar is one of the most elegant inventions I know of. When a car goes around a corner, centrifugal force causes the car to roll to the outside. There is no evading those physics! But, Canadian inventor Stephen Coleman had an idea for a simple way to counteract these basic physics. On April 22, 1919, he patented the first anti-roll, anti-sway, or roll bar. As usual, most things were invented 100 years ago! They only became practical as material costs came down (maybe hard to believe but see https://en.wikipedia.org/wiki/Simon%E2%80%93Ehrlich_wager. We humans are actually getting better at our treatment of the planet. At least to the extent that we can afford sway bars (and reduce the percentage of humans living in poverty from over 50% to under 10% in the last 25 years)!
Now, I was faced with the question of how stiff a sway bar to install and how to attach it!? I use both the exclamation mark and the question mark since this project fills me with doubt and excitement! I decided that I shouldn't go from no sway bar to a massive one, especially since the front suspension still has the old lever shocks. I was concerned that I would tighten up the rear end too much and over-steer. As usual, the actual results were clouded by misunderstanding the data.
As you can see, I went with a 5/8" sway bar from an MGB that I got for $20.
I machined up some aluminum blocks to bolt in where the original S2000 upper A-arm had two wire clips. I didn't want to drill any additional holes in what seems to be a highly optimized metal part!
To fully explain, I have added adjustable coil-over shocks to the rear suspension. So, this even further tightens up rear to front. And, during the event I used 4 clicks from soft for the first 3 runs, then 3 runs at 6 clicks, and the last 2 runs at 8 clicks. Once I got to 8 clicks, I found I had neutral steering, at least in a sweeper. That is likely a different answer in a sharp, dynamic corner since shocks provide speed proportional damping. In other words, the harder you corner, the stiffer they behave. But, I would guess I reach equilibrium in a long corner.
In any case, most of what I learned is likely wrong since I later discovered that my rear sway bar dropped three bolts and was unhooked after run #2! That's correct. The yellow block and the associated link bolt fell out somewhere (I'll have to check for that before the next Autocross!). I'm fortunate that it didn't do some damage as the link was banging around between the $600 axle and the toe rod! See my previous post for more details of fixing a car in a parking lot shortly before racing!
In any case, I made a new one, and used Loctite and it's still there. So, if parts fall off, dust yourself off, pick yourself up, and Loctite them back on! And keep having #funwithcars!
Now, I was faced with the question of how stiff a sway bar to install and how to attach it!? I use both the exclamation mark and the question mark since this project fills me with doubt and excitement! I decided that I shouldn't go from no sway bar to a massive one, especially since the front suspension still has the old lever shocks. I was concerned that I would tighten up the rear end too much and over-steer. As usual, the actual results were clouded by misunderstanding the data.
To fully explain, I have added adjustable coil-over shocks to the rear suspension. So, this even further tightens up rear to front. And, during the event I used 4 clicks from soft for the first 3 runs, then 3 runs at 6 clicks, and the last 2 runs at 8 clicks. Once I got to 8 clicks, I found I had neutral steering, at least in a sweeper. That is likely a different answer in a sharp, dynamic corner since shocks provide speed proportional damping. In other words, the harder you corner, the stiffer they behave. But, I would guess I reach equilibrium in a long corner.
In any case, most of what I learned is likely wrong since I later discovered that my rear sway bar dropped three bolts and was unhooked after run #2! That's correct. The yellow block and the associated link bolt fell out somewhere (I'll have to check for that before the next Autocross!). I'm fortunate that it didn't do some damage as the link was banging around between the $600 axle and the toe rod! See my previous post for more details of fixing a car in a parking lot shortly before racing!
In any case, I made a new one, and used Loctite and it's still there. So, if parts fall off, dust yourself off, pick yourself up, and Loctite them back on! And keep having #funwithcars!
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