The 24 Hours of Lemons Forums → Lemons Tech → The RIGHT way to cut springs (and lots of other useful stuff)
I just finished a story explaining all the free suspension tuning on the Frankenmiata. Most of this is not Miata-specific.
http://www.motoiq.com/magazine_articles … cksaw.aspx
There should be plenty of useful info for anyone with a Lemon and a calculator. Unless your car is French. I can't help you if your car is French.
-Dave
I cut one full revolution off each spring with the springs still in the car!
It's good.
KT
OK so our car is a VERY french LeCar, yes the one that rolled in Houston. It has torsion bar suspension all around and we talked about lowering it (resetting the torsion bars) as it sits pretty high. The only problem with this is that the torsion bars are pretty loose and I am definitely afraid of hitting the bump stops if we go lower. So here's the question - What is the best way to stiffen up the suspension when you have torsion bars. Stiffer shocks? Add light Coilovers? Any ideas?
Yes, you can add light coil-overs if there's room. It might be hard to find light-enough springs in a race spring catalog, but the MetroGnome (sorry, MetrO-U812) uses some kind of trailer spring for its coil-overs, so that's always an option.
Even cheaper, switch to long, foam bump stops as secondary springs and get a much bigger rear sway bar. This is what we did with the CRXXX, which also has torsion bars on the front, and it worked brilliantly. We didn't bother trying to lower it, though.
The CRXXX actually had coil-overs when we bought it, and we threw them away. Too much front spring rate makes bad understeer worse.
-D
Dave,
Nice write up.
OK so our car is a VERY french LeCar, yes the one that rolled in Houston. It has torsion bar suspension all around and we talked about lowering it (resetting the torsion bars) as it sits pretty high. The only problem with this is that the torsion bars are pretty loose and I am definitely afraid of hitting the bump stops if we go lower. So here's the question - What is the best way to stiffen up the suspension when you have torsion bars. Stiffer shocks? Add light Coilovers? Any ideas?
You can also add preload to the torsion bars and use straps or chains to limit downward travel, i.e. to keep the car low. I'd start with a big rear bar and go from there...
OK so our car is a VERY french LeCar, yes the one that rolled in Houston. It has torsion bar suspension all around and we talked about lowering it (resetting the torsion bars) as it sits pretty high. The only problem with this is that the torsion bars are pretty loose and I am definitely afraid of hitting the bump stops if we go lower. So here's the question - What is the best way to stiffen up the suspension when you have torsion bars. Stiffer shocks? Add light Coilovers? Any ideas?
you might try adding some rear shocks off of an older non monoshock dirt bike they would be "dirt" cheap used and most are adjustable for spring preload and damping
You can also add preload to the torsion bars and use straps or chains to limit downward travel, i.e. to keep the car low. I'd start with a big rear bar and go from there...
No offence, but that is, technically speaking, a terrible idea. Anything that will cause radical and sudden load changes at the tire will make the car very hard to drive. Running into a droop limiter will cause such a sudden change. Don't even think about it.
-Dave
jimeditorial wrote:You can also add preload to the torsion bars and use straps or chains to limit downward travel, i.e. to keep the car low. I'd start with a big rear bar and go from there...
No offence, but that is, technically speaking, a terrible idea. Anything that will cause radical and sudden load changes at the tire will make the car very hard to drive. Running into a droop limiter will cause such a sudden change. Don't even think about it.
-Dave
One teammate sugeested that and we shot it down pretty quick. (He's just a driver, we don't let him touch the car.) I had thought about atv shocks, but I didn't know if we would get enough travel out of them.
We are upgrading both torsion bars to some slightly modified Miata bars. You mention the rear bar, what about the front?
Think about the amount of mass an ATV shock has to control vs. the mass a car shock has to control. The forces required of an ATV shock are relatively low. I have no reason to think one would be anywhere near capable of controlling a car well. I could be wrong... (there's a first time for everything.)
Now, what are you doing with Miata parts? You have to be careful of your use of the word "torsion bar" here. Yes, a sway bar is technially a torsion bar, but since your car has torsion bars instead of springs, I can't tell what you're talking about. You using Miata sway bars? Explain...
I only mention the rear bar because all front-drive cars understeer and the cheapest way to fix that is huge amounts of rear roll stiffness. If you reach the point of too much rear bar (ie. its causing more oversteer than your drivers are comfortable with), then you can think about front bar. Until then, focus on the back.
Make the bar very adjustable, too. This will let you find the balance you want much more quickly. Back when we had a wide talent spread among our drivers, we'd run different bar settings for different drivers.
-Dave
You might be able to make an ATV, or rear shock from a motorcycle work if you're only expecting a few inches of travel, but it's probably going to take more work and money than it's worth. Used ones from older bikes are a crap shoot, and you'll likely get wide variations in their performance. The internals aren't going to fit within budget when you get to changing them out to deal with car rates. Seems like the last one we did was a couple hundred dollars just in parts, and we got to do it at the shop. You'll definitely need a friend with special equipment to re-fill them with the nitrogen they tend to use.
One thought is visiting the local micro-sprint track. They'll be used to adjustable rear torsion bar setups, and you might find someone with some stiff spares or a shock dyno that would give you some data if you're looking to get answers.
And Dave, I thought you said you couldn't help if it was French?
Who said my advice is helpful?
Who said my advice is helpful
I definitely would. Lots and lots to learn from reading articles like the one up top. A reason to love the Lemons threads
Now, what are you doing with Miata parts? You have to be careful of your use of the word "torsion bar" here. Yes, a sway bar is technially a torsion bar, but since your car has torsion bars instead of springs, I can't tell what you're talking about. You using Miata sway bars? Explain...
-Dave
Sway bars, sorry, We seem to think that stiffening both sway bars would be best since we have so much body sway. We will definitely take the rear bar into more consideration after your input though.
If you're using Miata parts, use a front bar in the back of the LeCar. A miata rear bar is a paperclip. It won't be strong enough for the back of a front-driver.
jimeditorial wrote:You can also add preload to the torsion bars and use straps or chains to limit downward travel, i.e. to keep the car low. I'd start with a big rear bar and go from there...
No offence, but that is, technically speaking, a terrible idea. Anything that will cause radical and sudden load changes at the tire will make the car very hard to drive. Running into a droop limiter will cause such a sudden change. Don't even think about it.
-Dave
Often did it on Mopars thirty-plus years ago and yes it's far from ideal.....rules prevented "export" torsion bars or auxiliary springing.....the secret was to overdamp the system and avoid bottoming the shocks. Handled well by the standards of the day. i.e bias ply tires, recirculating ball steering etc. It can be done but I agree if you can properly engineer a modern suspension solution withing the rules, you're way ahead.....
Ghetto, yes, but these can be found on TheSamba.com for a song:
http://www.autozoomparts.com/store.php/ … 74_by_empi
Absolute crap for offroad, but could give the torsion bar guys some help.
Ghetto, yes, but these can be found on TheSamba.com for a song:
http://www.autozoomparts.com/store.php/ … 74_by_empi
Absolute crap for offroad, but could give the torsion bar guys some help.
I had a pair of those on the back of my '64 beetle about 10 years ago. It helped out the sag issues with installing a 1600 into the rear. They were definitely stiff if I remember correctly.
rockwood wrote:Ghetto, yes, but these can be found on TheSamba.com for a song:
http://www.autozoomparts.com/store.php/ … 74_by_empi
Absolute crap for offroad, but could give the torsion bar guys some help.
I had a pair of those on the back of my '64 beetle about 10 years ago. It helped out the sag issues with installing a 1600 into the rear. They were definitely stiff if I remember correctly.
Yep. VW Baja people laugh at them, which makes them perfect for Lemons. 
One more question...Is modifying the suspension going to make our fabulous LeCar less of an IOE contender?
The 24 Hours of Lemons Forums → Lemons Tech → The RIGHT way to cut springs (and lots of other useful stuff)