Torsion Bar Help. Choosing a replacement diameter.

[BajaTX]

Recently, I did a bunch of work to my '64 Baja. I removed the Bus Reduction Boxes and installed a new transaxle with '68 tubes and chromoly axles. My Baja still has the original torsion bars. I removed the cast stops(they were severely beat) and I am using limit straps to handle droop. When I installed the torsion bars and spring plates, I followed the Hibbard Baja preload recommendation of covering 1/2 of the lower rear bolt hole. I expected this to hold the rear up at a reasonable height to clear my 31" tires. The bottom of the spring plates are above where the stock stops would be. My limit straps are nice and slack. My rear wheels are in a slight negative camber position. I would like to get the wheels to even or slightly positive camber at ride height. I would like to stiffen up the rear enough to keep from stuffing the tires into my fenders on minor bumps. How do I decide what diameter bars to purchase? I am assuming that I may not need preload if I get new bars that are closer to the correct spring rate.

Thanks,

[race-desert]

Baja- there is different spline counts outside and inside on the torsion bars- there is a way to get in between from just moving the out side splines! it took me having the chart and a few hours of trail and error to find the sweet spot ride height wise!
I stuck with the stock 22mm bars because you kind of only want the spring to hold the car up to the ride height you want.. I then bought a decent revalvable type shock (foa- fox) I went with FOA for starters! you can then adjust (revalve) the compression stiffness in the shock! if you get stiffer torsions remember that when you wind them up (Compression) you have to control the unwinding of it also - which will be much "faster" with a stiffer bar and make the car" buck" for the lack of a better word! I ran stock 22mm bars FOA shocks (stock location)with med firm compression and med rebound and had a nice little cruiser for the desert and still rode great on the street!

[BajaTX]

That sounds like a good idea. I am assuming that my stock bars are worn out. That is only because I preloaded them and they are at a ride height that is lower than stock. If they are the original bars, then they are 54 years old. Maybe I just need a new set of stock diameter bars. I don't really want to spend a ton on shocks right now. I realize that there are almost infinite adjustments available on the indexing of the bars. Should I just try turning mine up some more? That doesn't really seem like a great idea to me, but it would be free...

[oldschool5er]

This shows my old swingaxle using welded hard stops to limit camber. Modern web strap setups are the way to go but they do stretch although much quieter. It used bar straps to keep the stops from breaking. I used 28mm short bars with 31" tires and rebound was controlled with Bilstein shocks. My Class11 and my 5/1600 also use 28mm. You do not have to pre-tension a 28mm, just index to your full weight ride height, what I am meaning by this is that if you use a stock bar you usually will have to index then raise the springplate up over the stop hince a pre-load against the stop until you get it on the ground. A 28mm usually will be even or ever so slightly above the stock stop without having to compress it unless you are using a welded up stop to limit excessive positive camber. There are charts out there specifically showing recomended 28mm bar index specs for Bajas. It was oldschool but it lasted 40 years in Calif deserts and Mexico race preruns. The first time it ever was opened back up was just 2 years ago. It was not a cadillac ride and the stops and shock Heim ends were noisey, but without going coilovers it survived everything thrown at it.

For a Baja with 28, 29, or 30mm bars, Sway A Way says 9-12 deg's but it all depends on weight.

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[BajaTX]

Thanks Oldschool. That is great info.

[Dale M.]

(From Sway-A-Way)

Not only does chart above lower buggy/bug/baja, it works to raise buggy/bug/baja...

Simple method to determine how much to adjust is to set buggy on flat ground and use angle finder on spring plate and get its current angle, and if you want to increase positive camber raise buggy to where it sits where you want it and get new reading , do a little math and find difference in numbers and that is amount you want to change spring plate angle...

Dale
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"Kellison Sand Piper Roadster" For Street & Show.
"Joe Pody Sandrover" Buggy with 2180 for Autocross (Sold)
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All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ...

[BajaTX]

Thanks Dale. What do you think about turning up a set of old torsion bars?

[Dale M.]

[DHale_510]

Another factor is the reduction of spring rate from the added leverage of wider wheels. Most Baja rear wheels are about 3" deeper than stock. This reduces the spring rate by about 1/3. Some dunebuggies are deep enough to reduce the spring rate by half.
If you are concerned more about handling than looks, you want to be able to land a jump without breaking things that are not springs. Landing a 2500# Baja on the rear wheels with 100#/" spring rate [per side] will take 12.5" of travel. You probably have half that travel. 22mm torsions are less than 80#/" wheel rate with stock width wheels. Even without landing jumps, you want the springs to keep things that are not springs from bending and breaking when you hit bumps and holes.
The short, early torsions are more prone to twisting permanently, but actually breaking torsions is pretty rare. destroying the stock bump stops is pretty common.
Another problem with swing axles like on your '68 is tucking the rear wheels at full extention and rolling the car. The common fix here is a 1/4" stop added to the spring plate cover strap. It reduces the travel a bit but saves the car and with the larger torsion is all a good thing.
Good recreational Bajas need less stiffness than real racers. That's why the 25 and 26mm torsions are available and popular. They generally setup with the spring plate above the stop, rather than below at the hole, this gives a much nicer light load ride. Stiffer is not harsher than soft and banging into the stops.
Dennis