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Helper/Tender springs

 
Old 04-23-2019, 09:56 AM
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Default Helper/Tender springs

Currently, at the advice of Brian at Karcepts, my car doesn't have any helper or tender springs. I've never had any issues with the main springs coming unloaded, except when jacking up the car—in that case the springs will float, and I sometimes get the loud 'bang' as one or both of the rear springs re-seats itself. This is with JRZ RS-Pro shocks, Karcepts spherical upper mounts, and Hyperco springs, 700/550.

I happened to be flipping through the JRZ manual yesterday though, and noticed that it specifies the springs should always be under preload at full droop. So I checked with JRZ, and they said they recommend using tender springs. (Not zero-rate helpers, but tenders.) However I assume that advice wouldn't be S2k specific. They mentioned that if for example you drop a wheel off a curb on the track, this would allow you to still have some spring force and traction at that corner. Which makes sense, but looking at how far I have to jack the car up before the main springs are fully extended, I would have to drop a wheel off a cliff before that became an issue. Soooo I'm not really seeing why tender (or helper) springs would be useful, except to avoid that bang when taking the car off jack stands.

Now, if you went to a true tender that was just barely fully compressed at regular ride height, so it was designed to actually become active once that corner became un-loaded, that would certainly have an effect.. Basically then you'd end up with dual spring rates—stiffer normally, and softer on less-loaded wheels (ie the inside under cornering, or the rear when braking). I could see that potentially being useful, but I'd think the car would have to be set up around it. Also, with the limited bump travel in the rear, I'd think a significant tender spring might limit the bump travel of the main spring.

Anyone care to weigh in? Right now I'm considering just getting a pair of helper springs to fix that bang that always makes me jump out of my skin (and seems like it couldn't be good for the perches) when the rears re-seat themselves, and otherwise not worrying about it since the car drives fine.
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Old 04-23-2019, 10:12 AM
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I have never used them with my setups on this car. Have never had an issue (never even had them pop when lowering as they seem to just sit flat and not get out of place). Curious to see what others reply here as well.

For reference, I have run koni yellows with koni sleeves and koni upper perches with the stock top hats, and right now am on TCKlines with koni sleeves, no top perches and just the stock top hats.
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Old 04-23-2019, 10:33 AM
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If you're riding kerbs you'll find you hit the droop stops often. If you have zero preload you'll also find that the last portion of the travel is barely used because the rebound damping means that the extension is so slow your chassis just drops into the hole/bump instead of the wheel and suspension following the road.

Springs that come loose under full droop also have a penchance for jumping out of their seats and going sideways which usually breaks something - you can't think of the spring as just a static piece as you're looking at it with the car jacked up, it's vibrating both radially and laterally when in use.
There's no real reason not to use tenders or helpers unless you just don't have the room.
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Old 04-23-2019, 10:50 AM
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Originally Posted by BuggyofMildDiscomfort View Post
If you're riding kerbs you'll find you hit the droop stops often. If you have zero preload you'll also find that the last portion of the travel is barely used because the rebound damping means that the extension is so slow your chassis just drops into the hole/bump instead of the wheel and suspension following the road.

Springs that come loose under full droop also have a penchance for jumping out of their seats and going sideways which usually breaks something - you can't think of the spring as just a static piece as you're looking at it with the car jacked up, it's vibrating both radially and laterally when in use.
There's no real reason not to use tenders or helpers unless you just don't have the room.
Are you sure that's the case for an S2000 in standard STR or time attack prep though? My car has very little roll under normal conditions—I can't be absolutely certain, but I don't think I'm coming anywhere close to reaching full extension of my main springs on the track, even when riding curbs or what have you. (I'm judging this based on how much body roll I feel and can see in pictures from outside, compared to how far up a corner of the car needs to be jacked before the spring is fully extended.)

I agree that there shouldn't be any downside to helper springs, aside from a bit of weight (potentially unsprung weight if you put them below the main springs). Tender springs though would change the dynamics of the car, lowering the spring rate on less-loaded wheels. That could be good or bad. (Unless you're talking about tenders with such a low spring rate that they're effectively acting as helpers.)
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Old 04-23-2019, 10:58 AM
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Originally Posted by BuggyofMildDiscomfort View Post
If you're riding kerbs you'll find you hit the droop stops often. If you have zero preload you'll also find that the last portion of the travel is barely used because the rebound damping means that the extension is so slow your chassis just drops into the hole/bump instead of the wheel and suspension following the road.

Springs that come loose under full droop also have a penchance for jumping out of their seats and going sideways which usually breaks something - you can't think of the spring as just a static piece as you're looking at it with the car jacked up, it's vibrating both radially and laterally when in use.
There's no real reason not to use tenders or helpers unless you just don't have the room.
Are you sure that's the case for an S2000 in standard STR or time attack prep though? My car has very little roll under normal conditions—I can't be absolutely certain, but I don't think I'm coming anywhere close to reaching full extension of my main springs on the track, even when riding curbs or what have you. (I'm judging this based on how much body roll I feel and can see in pictures from outside, compared to how far up a corner of the car needs to be jacked before the spring is fully extended.)

I agree that there shouldn't be any downside to helper springs, aside from a bit of weight (potentially unsprung weight if you put them below the main springs). Tender springs though would change the dynamics of the car, lowering the spring rate on less-loaded wheels. That could be good or bad. (Unless you're talking about tenders with such a low spring rate that they're effectively acting as helpers.)

Edit: although, thinking about this some more—my springs are 700lb/in and 550lb/in. My corner weights are just over 700lb. Sooo presumably at rest, the springs are each compressed by only about an inch. Is that right? Or are they somehow preloaded independently from the weight of the car? If it really is only an inch of compression when flat, then yeah, I could totally see the main springs coming unloaded if you hit a small dip on the inside of a corner or similar. Hmm.
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Old 04-23-2019, 11:10 AM
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Maybe I am thinking about it wrong, but it doesn't seem like we'd see full droop on track unless an entire end of the car is off the ground due to the anti rollbars tying the wheels together.

Anyway, I am here to listen also. I've got Penskes with 850/600lb springs that come unseated at full droop (but not below the vertical retaining portion of the upper spring seat), it has been fine for two years now, but always open to changes.
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Old 04-23-2019, 11:49 AM
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I am feeling the same. Most autocrossers I have talked to about this subject do no run helpers. Never had them on my last car either (9 years modified and autoxing without helpers) with no issues. The sway bar would add loading under hard cornering and would prevent full droop and on big dips if you are running much rebound setting they will only drop so far in such a short amount of time. I cannot think of ever hearing of people having any real issues due to this. That does not mean issues cannot occur of course. That is just my experience.
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Old 04-23-2019, 12:38 PM
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I have helpers on my ProParts/TCKline Koni setup. The only reason for this was jacking the car up/down. I change tires a lot and really don't want to be bothered with that noise or any issues with the spring becoming unseated. Even if I attack a curb and momentarily lift one part of the car, my rebound valving will not allow the suspension to hit full droop.
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Old 04-23-2019, 12:47 PM
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Originally Posted by engifineer View Post
if you are running much rebound setting they will only drop so far in such a short amount of time.
This is true, and is part of the problem as I understand it. Say at rest your springs are compressed by 1", and under hard cornering the inside springs expand (obviously) so at this point they're only compressed by 0.5" (for example), and then you hit a dip larger than half an inch, like a somewhat aggressive curb. For the first half inch, your spring is going to be pressing down as usual, so despite the damper's resistance, the tire will quickly be pressed down as intended, to maintain contact. However, once your spring runs out of travel, your tire is still above the ground, and at this point it only has momentum and gravity pulling it down, vs the full rebound resistance of the damper.

So yes, it's unlikely that the wheel is going to shoot way down such that the spring comes out of its perch in that situation. (That would be more of an issue if you're lifting a wheel on corners I would think.) However, what will happen is that your inside wheel won't be making good contact through that dip, so you'll be sacrificing grip. Also, the drop in grip will come fairly suddenly as the spring reaches full extension and the wheel floats. On the other hand, if you have a tender spring, there will still be some spring force pushing the wheel down even once the main spring has reached the limit of its travel, so you'll maintain better contact with the road in the scenario described.

Now, let's say that in addition to your 700lb/in main spring, you have a 100lb/in tender spring with 3" of travel between full compression and full extension. When the car is sitting flat with 700ish lb on that corner, that spring will be fully compressed, and your spring rate will be that of the main spring, as if the tender weren't there. When you're going around a corner as described above, and the inside wheels are only loaded to ~350lb instead of the full 700, the tender spring will still be fully compressed, not doing anything. However, when you then hit a dip, and an inside wheel's load drops below 300lb, the tender spring will start to expand, and the new effective spring rate at that corner will be given by

Combined Spring Rate =
(Spring Rate 'A' x Spring rate 'B')
÷ (Spring Rate 'A'+Spring Rate 'B')

So 700x100 / (700+100) = 87.5. (Which makes intuitive sense, since it must be lower than what the tender spring would be alone, if it were sitting on a solid perch.) The advantage here, as I understand it, is that at least you're still pushing down on the wheel somewhat, rather than having it totally float, so you're maintaining better contact with the ground. I guess the downside, aside from cost, complexity, and it needing to fit, would be that for small dips that would not have caused the main spring to float, but which are enough to allow the tender to expand, you're sacrificing spring rate. So I guess that's the tradeoff. I also have to wonder how much 87lb/in of springs actually helps in those dips, when they're fighting rebound damping tuned for 700lb/in.

Edit: of course, you could go with a stiffer tender so that it has more of a useful effect, but that also means it would start expanding sooner, so the downside of the tradeoff would also be magnified.

Last edited by Nate Tempest; 04-23-2019 at 12:52 PM.
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Old 04-23-2019, 01:05 PM
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Too much over analyzing here for something that offers a real function with no draw backs other then a few bucks. The idea is not too add spring rate altering the shock dynamics, but rather just keep the spring seated on the perch at full droop, picking up the gap between your spring and perch retaining the ride height flexibility you want. Its possible not just when jacking up the car but on more abrupt elevation changes to pick up both wheels enough to unseat the springs. I added some Eibach 0 rate helper springs to my coilovers when I changed the springs out for the shorter stiffer ones and needed them at that point. Just get them and forget about it. Could save you some annoyances or problems down the road.
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