I took my left side coilovers off today and intended to swap the springs front to rear. However, I was surprised to see that the front and rear have different rate tender springs. Looked up the spring denotations on the H&R site and found the following.

Front.
140-160 = 914 lb/in
100-60-50 = 286 lb/in

Rear.
140-140 = 800 lb/in
80-60-20 = 114 lb/in

So I finally figured out that the first number is the free length in mm and the last number is rate in N/mm. The middle number for tender springs is the inside diameter in mm. Whew.

Now, the question is do I just swap both front springs with both rear springs or just swap the main springs from front to rear. I find it interesting that they use a longer tender spring up front than they do rear. I wonder why. Any feedback from racers that use tender springs?

 

That IS weird. Really weird.

Are they completely compressed (to coil bind) when the car is on the ground? If so, I wouldn't sweat it much.

 

Yeah, they are basically completely compressed.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by chrisb &raquo;</TD></TR><TR><TD CLASS="quote">Yeah, they are basically completely compressed.</TD></TR></TABLE>

Then they're not doing anything - they're just a spacer, if you will. Something to keep the springs from un-seating when they're unloaded.

Still...interesting that the rates are different. Perhaps H&R used whatever they happened to hve on the shelf?

 

But here is another interesting point. They quoted me as having 950# front springs and 800# rear springs. Yet as shown above the front springs are only 914#. However, the front has higher rate tender springs. So does the rate of the tender spring affect the overall rate? I would think so.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by chrisb &raquo;</TD></TR><TR><TD CLASS="quote">So does the rate of the tender spring affect the overall rate? I would think so. </TD></TR></TABLE>

No, because that spring is fully compressed when the car is on the ground. Its unly usefull when the inside front/rear is at extension - keeps the spring seated on the seat so it doesnt make *clankclank* noises

RJ

 

The tender springs are doing exactly nothing during the race. If you're running swaybars on both ends, the inside isn't unloading enough to unseat the springs.

Those rates are so close I doubt you'll feel a difference by swapping them. Remember that Ratcliffe and I were running a 400lb difference front to rear with rear bars as big as yours.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">

No, because that spring is fully compressed when the car is on the ground. Its unly usefull when the inside front/rear is at extension - keeps the spring seated on the seat so it doesnt make *clankclank* noises

RJ</TD></TR></TABLE>

You are thinking of Helper Springs I believe. These have only enough spring rate to push up or down on the spring to keep it aligned. These (114# or 286# springs) are acting like a progressive rate spring from my understanding. I've seen these on a lot of Porcheys (but always swip swap the names vs. their meaning tender vs. helpers).

 

Interesting. But i figure they're still at full compression when the suspension is loaded.

 

A short 114ish lb spring is very likely going to be fully compressed static on that car. If not, it'll be really close.

 

I don't have a clue here man, just making stabs in the dark but if what you are saying was true, wouldn't we also say the percentage of preload on your springs does nothing as well (and maybe I am inaccurate on this as well)? If I were making my typical uneducated guesses, I'd think that it plays a role in transitions??? No clue though - just guesses from the cheap seats.

 

Whether a coilover suspension utilizing a tender spring along with a main spring is a superior setup vs. the typical Koni setup with a single main spring with an optional zero rate helper spring is very hotly contested. Like Adam says, a ton of Porsche race cars use this dual spring setup. An acquiantance of mine that owns a Porsche race shop in Tempe, AZ is a big proponent of dual spring setups. Personally, I just don't fully understand them.

 

when you add springs in series, the reciprocol of the sum of the reciprocols of each spring is the new spring rate. a 200# spring and a 400# spring in series is going to be 133#. (1/x = 1/200 + 1/400 = 3/400, x = 133) notice how the combined spring rate is LOWER than the lower spring rate. but thats only until the weaker spring is fully compressed, at that point, the spring rate shoots up to the 400#.

the spring rates you listed when combined in series are 218#f/100#r. combining both left and right corners in parallel (you ADD spring rates in parallel) is actually 436#f/200#r. considering your car is front engine, FWD or FF, lets assume 1500# resting on the front axle, and perhaps 1000# and evenly distributed one both sides of each axle. (i actually dont know off the top of my head what the front/rear weight distribution is, feel free to fill in some more realistic numbers). the front springs would lower about 3" and the rear 5" as the car is resting on the ground. so, if your front 218 spring has MORE than 3" of travel, than yes, youd have a transition of spring rate during its normal bump travel, likewise in the rear for 5".

that was in interesting review of high school physics... any questions?

 

tyson, are those wheel rates or just the spring rate? i'm curious because i think the secondary spring may already be compressed at static ride height (depending on it's length) due to the motion ratio of the suspension. a quick check of the eibach catalogue on ground-control's website shows that a 250lb/in 2.87" free length 2.5" diameter spring coil-binds with only 440lbs of force. with a 914lb/in main spring i would guess that the secondary spring will either be in coil bind at static height, or really close too it. don't the front springs essentially "see" over 1500? i'll have to pull out my automotive math handbook tonight and look all the formulas up and post them up.

a dual spring setup has a very tuneable progressive spring rate (unlike a "progressive" spring that usually doesn't get to a high portion of the spring rate before the shock bottoms out) which can be used to tune the car for various surfaces. the vehicle dynamics involved scare me a bit though. i've just finally gotten a good grasp on setting a car up with a single rate spring and would have no idea which end should be more progessive or less or how progressive each end should be.

nate-who might start playing with it next year....maybe...

 

I Like to keep things simple and use a single spring. Assuming you have a shock package that can handle the spring rates I would go with 1000-1400 rear and 600-700 front. Im starting at 1000 rear and 600 front with my new Bilstein setup. For reference the Motons were 700 front and 1400 rear.

Just my 2 cents.
Alex
King RAT Motosports LLC
Hypercoil Reseller.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kingrat &raquo;</TD></TR><TR><TD CLASS="quote">I Like to keep things simple and use a single spring. </TD></TR></TABLE>

what's the fun in that?

nate

 

I have Bilsteins from the H&R Type R road race coilover setup. I don't know much about the shocks but the guy who sold me the car said he would not go over 1000# with the rear springs without having the shocks revalved. The thing is that I am supposed to be running Beaver Run and I can't afford and probably don't have the time to order any springs. I hate messing with car setup as I don't understand it. I just know that the car understeers everywhere and all the time and it causes me to get dramatically slower as the race wears on.

I just wish I knew if I should swap the tender springs front to rear (put the shorter but higher rate tender spring on the rear) when I swap my higher rate main spring to the rear.

 

I wouldn't worry about it. ~100# bias is not going to buy you that much. Run Beaver on the current setup and order some springs for next time. H&R now makes 2.50" ID springs if you want to stick with them or go with Eibach ERS.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kingrat &raquo;</TD></TR><TR><TD CLASS="quote">For reference the Motons were 700 front and 1400 rear.</TD></TR></TABLE>

HOLY CHIT! And this guy, if memory serves, told me he had the rear of the car toed out a little bit.

What was that like? Other than, um, "challenging to drive?" If you had to check up to avoid someone did the car whip around on you?

I'm a lot more interested in this stuff now than I was last week, as my Konis are on a truck, on their way to Lee to get revalved...

 

i didnt say anything about wheel rates. maybe you got confused in the numbers, i guess you didnt understand that the combine spring rates i calculated is when both springs are totally uncompressed. you can then calculate given more realistic corner weights and disregarding any other bushing or flex, how much compression at static weight alone, which will tell you if the "tender" springs are any effect in bump compression. and yes, once one spring is totally coil binded, it is totally out of the spring rate equation and the new spring rate goes to whatever spring force is left.

but the important part of the numbers is that understanding a combined spring rate of 200# and 900# springs will be LESS than 200#.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by chrisb &raquo;</TD></TR><TR><TD CLASS="quote">I have Bilsteins from the H&R Type R road race coilover setup. I don't know much about the shocks but the guy who sold me the car said he would not go over 1000# with the rear springs without having the shocks revalved. The thing is that I am supposed to be running Beaver Run and I can't afford and probably don't have the time to order any springs. I hate messing with car setup as I don't understand it. I just know that the car understeers everywhere and all the time and it causes me to get dramatically slower as the race wears on.

I just wish I knew if I should swap the tender springs front to rear (put the shorter but higher rate tender spring on the rear) when I swap my higher rate main spring to the rear.</TD></TR></TABLE>

if you're worried, leave out the secondary springs. we all know what will happen with 800fr/900rr.

tyson, i'm a ****. i should slow down and read what i've typed before i post it. what i was getting at was that with the motion ratio's of our cars, a secondary spring with that low of a rate and that short of a free length is most likely already fully compressed at static ride height. even though we have a pair of wheels supporting a theortical 1500lbs, the springs are actually seeing nearly 3000lbs of force. with a 440lb spring rate you would compress the springs well over 6" if the shorter spring never bound up. basically i'm saying, "yeah, i understand, but let me ramble on and on about it and point out the obvious." on me.

nate

 

-----------
What was that like? Other than, um, "challenging to drive?" If you had to check up to avoid someone did the car whip around on you?
-----------
It was Like balancing on a knife edge. Ultimately ver very quick, but the margin for error (as I demonstrated frequently last year) was small. I like my new setup better. Its easier to drive, but not quite as tight in the corners. Should be fun at summit in H3!!!

You definitely need custom valving above 800lbs, otherwise you'll quickly ruin the shocks. I had Morriss Dampers dyno the Motons then re-valve the Bilstein component as close as they could get so I can up the spring rate if need be. It wasnt cheapest option at about $600 per shock, but worth the money in my mind.

KR.

 

Chris

If you car is understeering you might be able to control it by adjusting you rear camber. I tried from 1 degree negative to around 2 degrees neg in the rear.

The more camber the less understeer/more oversteer I got. Its a very fine adjustment to make though. as for toe I ran 1/8th to 1/16th toe out up front and a 1/16th toe out in the rear.

Also can you adjust your sway bars? and whats your front camber?

Alex.
KRM.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kingrat &raquo;</TD></TR><TR><TD CLASS="quote">Should be fun at summit in H3!!! </TD></TR></TABLE>

Oh good.

Could you be nice and maybe not lap me. That'd be good.

 

Quick Rice .. add the ``any car driven by Kingrat gets an automatic 2 class bump'' to the rulebook!