Very minimal experience but I spoke to the guy at Sway-A-way when we were getting ready the truck ready for Pikes Peak. We had 2 14" coils at 450lb/in stacked and we were trying to stiffen it up. Sway-a-way said just by taking off 1 coil we would increase spring rate by 270%. Definitely felt stiffer driving around on the street, but going up PP we were basically riding on nitrogen bump stops with 300psi in them.




ps sorry about how my driver passed you guys coming down. He wasn't listening to me (co-drivers are only needed to tell if the corner is a left or a right) and drove like an a$$hat the whole way... make that whole week.

Quote
FunctionAuto
Very minimal experience but I spoke to the guy at Sway-A-way when we were getting ready the truck ready for Pikes Peak. We had 2 14" coils at 450lb/in stacked and we were trying to stiffen it up. Sway-a-way said just by taking off 1 coil we would increase spring rate by 270%. Definitely felt stiffer driving around on the street, but going up PP we were basically riding on nitrogen bump stops with 300psi in them.

Worksheet from Hypercoils shows two 450# springs stacked have an effective rate of 225#. What the sheet doesn't get into is what the "rate curve" looks like if you're using different length springs. I think I'll need to figure out how many inches of compression the softer coil has until it coil binds, because at that point, the rate instantly becomes whatever the stiffer spring is.

Quote
FunctionAuto
ps sorry about how my driver passed you guys coming down. He wasn't listening to me (co-drivers are only needed to tell if the corner is a left or a right) and drove like an a$$hat the whole way... make that whole week.

No need to apologize, after the week you had, I'm sure it felt good to beat someone at something. I think everyone passed me except the black Evo (because I asked them to stick behind us in case the wheel came apart. Happy to report I drove it onto the trailer still mostly in one piece.

Dave

Stacked springs gives you softer rate, just like cutting a spring stiffens the rate. Reason is that it is a coil that supplies "the give" in a spring. More coils = more give and vice versa.
It actually makes sense when you think about it :-).

---

Brgrds
Brian

Dave. Why?

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NoCoast
Why?

Looking for solutions to the bottoming out issue without losing the compliance in the back end. I still want the back to compress nicely under throttle...I just don't want it bottoming out and bouncing me into the trees. So, the thought was a dual spring setup might give me the softness needed for grip, but if setup right would 'activate' the harder spring before it bottoms out.

Someone showed pics of a dual spring setup that was working well for them...figured it was worth investigating how those setups actually function so I don't go blindly tossing springs on there. The small bit of stuff I've found already tells me that the rates I was considering are waaaay too soft.

Of course before committing any money to a solution I still need to get under the car to get measurements to see what the actual limitations on my setup are at the moment (shock travel or wheel well/tire clearance).

Could also be as simple as exploring different bumpstops and/or adding another set of them.

Dave

Too hot to actually work on the car in the middle of the day, so I've been looking things up. Found some interesting info on bumpstops:

http://fatcatmotorsports.com/FCMstops_comp.htm

Seems that stacking bumpstops (PVB's suggestion a few pages back I think) or simply looking for ones with a more suitable rate could be a much easier and lighter option than the dual springs. Of course stacking them means we'd need to look at the stacked spring rate calculator to get a feel for what the actual rates are. Too much math...time for a beer.

Found another site with several different types of bumpstops, all with graphs of the rates. This is looking promising & they're cheaper than a 2nd set of springs.

Ohlins Bumpstops:
http://www.resuspension.com/techinfo/ALL%20OHLINS.pdf

Penske Bumpstops:
http://www.resuspension.com/techinfo/ALL%20PENSKE.pdf

RE Suspension Bumpstops:
http://www.resuspension.com/techinfo/ALL%20COT.pdf

Dave



Edited 3 time(s). Last edit at 07/03/2011 08:02PM by DaveK.

Dave on top of everything elsde, the actual shape of bumpstops makes a big diff on their rates, conical is one thing, straight sumpin else and I've seen double conical. Wot da fawk!

You're right on the "steady as she goes" and think and read before committing. When we went to duals we all nearly bankrupted ourselves, and it was only via Socialist principles learned right there in Sweden "from each according to...to each according to ...blah blah....' that I got some of us po'drive guys together and we'd swap and barrow so we could avoid buying---until we found something that worked good.

Talk to mr Wimpy, he was running 2 springs on the long shocks on his Fau Veee.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Hi Dave, Below is an example that might be useful for your needs.

I have made the following assumptions:
1) the weight on each rear wheel at static ride height is 600lbs
2) Motion ratio is 1 to 1
3) Total available stroke is 8"
4) You are looking for something with 175lb or softer rate but less bottoming
5) Zero spring preload


Starting with 2 300# springs stacked one 12" and one 4" you get a spring rate of 150# for the first 4" of travel. This is where the 4" spring will likely be fully compressed (assuming a 2" stack height at full compression of a 4" spring). This is also approximately where the car would sit at static ride height.

From here, the effective spring rate is 300# until the bumpstop is reached and it goes up again.



If you start playing with the numbers, you will notice that it is advantageous to have one spring much shorter than the other in order to achieve a rate change where you want it. On off-road trucks with loooong springs, they use these clamps to stop the spring slider at a set point to adjust where in the travel the rate change occurs but they have much more leeway for packaging than we to.


If you are looking something less dramatic then you have to go with a softer long spring and shorter stiff spring. For example, a 12" 250# spring coupled with a 3" 350# spring gives the same 150# rate for the first 3.5" of stroke before rising to 250# for the remainder. It will also give you a static ride height that is about 5 millimeters higher than the 300x300 setup above as the 600lb static load is reached at 3.8" of compression rather than 4".


Hope this is helpful.... Make a spreadsheet (or make Grant make one :-)) and see what happens.

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Josh Wimpey
Hope this is helpful.... Make a spreadsheet (or make Grant make one :-)) and see what happens.

Very helpful, thanks!

Now the question is do I try the bumpstop fix first (buy 4 bumpstops ~$80), or the more expensive spring swapping (buy 4-6 springs to try out different stuff)...hmmm.

Thinking I need to see what the tire/wheel well clearance is first, and if I end up needing to go with longer shocks I'll experiment with the dual springs, but if I don't have much to be gained with extra suspension travel, the bumpstops may be the easier option since those have variable spring rates.

Dave

_________Amount of Shock Piston Showing

Fender___JVABw/____JVABw/_____Stig w/
to Hub___spacer_____no spcr_____no spcr
20.000________________________________Full Droop, when RTA contacts rear beam
18.000___8.500________________________JVAB Shock w/spacer at full droop
17.750_________________________9.000__Stig Shock w/no spacer at full droop
17.000___7.675________________________
16.875_____________8.500______________JVAB Shock w/no spacer at full droop
16.000___6.750________________________
15.000___5.750_________________6.500__
14.000___4.750_________________5.375__
13.000___3.750_________________4.375__
12.000___2.750_________________3.375__
11.000___1.750_________________2.375__
10.000___0.500_________________1.500__
_9.750________________________________195/70/15 BFG w/20mm spacer rubs bumper/spash guard
_9.375___0.000________________________JVAB Shock w/spacer bottomed out
_9.250_________________________0.375__Stig Shock w/no spacer bottomed out
_9.000________________________________195/70/15 BFG w/20mm spacer rubs front edge of fender Lip
_8.375_____________0.000______________JVAB Shock w/no spacer bottomed out
_7.500________________________________195/70/15 BFG w/no spacer rubs in wheel well

JVAB Bilsteins 260/90 valving
Stig Magnesium 350/110 valving

Spring Details

___14 Number of Coils
_0.461 Wire Diameter
_2.961 Spring Diameter (Mean)
13.675 Free Length
_6.339 Solid Height
_7.336 Compressible Height
__175 Spring Rate

Looking at the rear springs, there's evidence that I'm fully compressing the springs, as there are marks/scuffs between the coils to indicate they've been hitting. This could explain the severe bottoming out issue...right? As soon as the coils are fully compressed, I have no more travel. If I have 8.5" of shock travel, but only 7.3" of spring to compress, that means I'm bottoming out the spring before the shock has a chance to. I have been running helper springs to allow me to drop the car just a little bit more than simple spring sag would allow, but at a 14.5" ride height, the helpers are already compressed down to ~0.75".

Stock ride height is ~12.5-13 and I think I'd like to end up somewhere in the 14-15" range. The higher the car sits, the more the rear end allignment goes wonky.

So, I'm seeing that I need springs that have more void space. Hypercoil has some "ultra high travel" springs which are advertised to have one (or more) less coils so there's more void space.

Another question that's popping into my head is: ame I better off swapping the 1" spacer at the top of the shock for the short one. The way I see it is I'd lose ~1" of droop to gain 1" of compression travel. I think this would be ok, since I've got more room for the tire to pack on into the wheel well, and the bumpstops (not on the car during any measurements) will take up some space making the wheel unable to actually hit those "fully compressed shock" measurements.

Dave



Edited 1 time(s). Last edit at 07/11/2011 12:18AM by DaveK.

Quote
DaveK
Looking at the rear springs, there's evidence that I'm fully compressing the springs, as there are marks/scuffs between the coils to indicate they've been hitting. This could explain the severe bottoming out issue...right? As soon as the coils are fully compressed, I have no more travel. If I have 8.5" of shock travel, but only 7.3" of spring to compress, that means I'm bottoming out the spring before the shock has a chance to.
Dave

Yes, and this will cause bulged shock tower tops, and bendy parts elsewhere very quickly...

Also cause horrible handling :-)

You need another 3" to 4" or so of spring or something with more void between the coils as you suggest.

A good way to test if the springs are going into full compression is to put a zip-tie around a single coil and then go out and hammer over some rough and jumps. If the zip-tie breaks, you have spring coils clanging together. If not, you are OK. of course, bulged strut towers & bendy bits elsewhere are good tell-tales as well.

If you are binding the springs look at these.

http://www.integrashocksandsprings.com/pages2010/springs2010.html

I got a set, and they are real nice, much lighter, and have more travel for the same length of spring...since i really doubt you can get more than a 14" spring back there.

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Do It Sidewayz
If you are binding the springs look at these.

http://www.integrashocksandsprings.com/pages2010/springs2010.html

I got a set, and they are real nice, much lighter, and have more travel for the same length of spring...since i really doubt you can get more than a 14" spring back there.

Unfortunately it looks like they're only making 2 5/8" springs, so that's a no-go.

The other issue I'm running into is that most of the 'low coil count' springs are barrel type springs and I'm not sure I've got clearance for those when the car approaches full compression. Thinking I could probably do a 4" normal spring and a 12" barrel spring and not have tire clearance issues if I stick the 4" spring up at the top...but that's 4 springs I'd need to order.

Dave

Quote
DaveK

Quote
Do It Sidewayz
If you are binding the springs look at these.

http://www.integrashocksandsprings.com/pages2010/springs2010.html

I got a set, and they are real nice, much lighter, and have more travel for the same length of spring...since i really doubt you can get more than a 14" spring back there.

Unfortunately it looks like they're only making 2 5/8" springs, so that's a no-go.

The other issue I'm running into is that most of the 'low coil count' springs are barrel type springs and I'm not sure I've got clearance for those when the car approaches full compression. Thinking I could probably do a 4" normal spring and a 12" barrel spring and not have tire clearance issues if I stick the 4" spring up at the top...but that's 4 springs I'd need to order.

Dave

Are you using a 2.5" ID spring? if so, big deal. A 3" i could understand.