Postby Loren » Sat Apr 16, 2016 12:52 am
I just did something weird. Seemed weird as I was doing it, anyway.
The ride of the Festy is horrible. Mostly due to the rear suspension. If you just hit a plain ol' bump, it BOUNCES over it. If you hit a one-wheel bump, because the beam axle is so stiff, it 3-wheels and then CRASHES back down. It's really not that bad for autocros (except at the dog track) as long as you're smooth. But, street manners are atrocious.
With the new coilover kit, the rear spring rate went up from about 170 to 250. Needless to say, that didn't help things AT ALL!
So, after much hemming and hawing, and tonight was my 2nd foray into research... I decided that I've wasted well over 6 hours trying to find "the ultimate spring" to give me what I need without spending a bunch of money. (for the front, I found a 175# 14" spring that I cut in half to make two 350# 7" springs... for about $30!) Wasting way more time than I'm saving money. Time to buy something, dammit!
Still, I try to be frugal, so I did manage to find springs for about $35 each (instead of $48-70 each). That means that I didn't get exactly what I was after, but had to compromise to save a few bucks.
Still with me? Good.
The current rear springs are 250# and 6" long. The coilover sleeve is set as low as it will go, and it's at a good height. To go any lower, I'd have to get creative... there's probably .5-.75" of not-too-creative space available if I needed it.
With an estimated 900# of rear roll stiffness from the beefed up beam axle, we really don't need stiff springs. HAVING stiff springs is what's making the car BOUNCE over bumps and CRASH upon recovery from lifting a wheel. (particularly over a bump) What we had before was 170# and was barely tolerable. The 250# we have now just sucks. (corners like a mo-fo, though) So, I wanted to go somewhere under 170#. Something like 150# didn't seem like enough of a change, I was really aiming for 120-130#. Wanna make yourself crazy? Try to find springs in the sub 200# range that are shorter than 10"! They can be found. But, try to find them cheap or used... nope!
Ultimately, what I ended up with was a pair of new 100# springs that are 10" long. Would have preferred a 7 or 8" spring, but this will work.
The maths say that:
The 100# spring will have a static installed height 2.2" higher than the 250# spring. I can remove about 3/4" of that, making it more like 1.5" higher. Will give the car a slight rake. Can probably live with it if it makes the car FEEL better.
The 100# spring will compress about 3" at full body roll (this could in itself reduce a lot of the wheel lift... less entertaining to watch, but could feel a lot better). The 250# spring only compressed 1.2"! That was ALL of our rear suspension movement... about an inch!
I'll be installing our full-length progressive bump stop, which will help alleviate some of that compression travel... it might only compress about 2" with that, we'll see.
Always the science project, this car!
Hopefully, the new springs will arrive Monday or Tuesday and can be installed before next Sunday. (the rear suspension is super-easy to R&R on this car, could do it by myself in about 20 minutes per side)
Loren Williams - Loren @ Invisiblesun.org
The "Push Harder, Suck Less" philosophy explained:
Push Harder - Drive as close to the limit of your tires as possible.
Suck Less - Drive something resembling a proper racing line.