Any Suspension Gurus?

"ESSSIX GmbH - Accountant/Wagon Thumper" (thedlo) 05/03/2016 at 13:34 • Filed to: suspension, spring rates, race car

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Specifically with regards to spring rates, and stacking springs (tenders etc.).

I’m getting ready to order springs for my S6 Avant, and I think I found the set up I’m going with:

In the front: 175-550lbs progressive tender over a 600lbs main spring(8" total). Paired with a Koni Race strut with comp and rebound adjustment.

In the rear: same tender (175-550lbs) over a 550lbs main spring (8" total). Paired with a QA1 strut with comp and rebound adjustment as well.

(the different struts front and rear are because nothing really just bolts up to the car, and these 2 are the only ones that fit with minimal fabrication)

So far from what Ive read progressive tenders make the ride nice and smooth during normal driving, and when you load it you’ll get that higher spring rate feel when it counts/matters. Now I know the adjustable struts can greatly affect the characteristic of the springs, but that is all guess work till they’re on the car.

For reference the Avant weighs about 4000lbs with me in it. (When everything is installed I’ll get it corner balanced)

Im hoping to have the suspension sorted by the end of the month, I would like the Fikses to go on at the same time too. Currently Im waiting on a new face and 3 lips (LOL) and then they’re ready for the new Michelin pilot super sports I got on Craigslist for $600(!?).

Cheers.

itschrome > ESSSIX GmbH - Accountant/Wagon Thumper 05/03/2016 at 13:41

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whoa man, NSFW tag that last photo. daaamn..

sorry no real help just really liked your car..

OPPOsaurus WRX > ESSSIX GmbH - Accountant/Wagon Thumper 05/03/2016 at 13:41

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brutha please, forget all that fancy blah blah blah and just get this

https://www.arnottindustries.com/part_AUDI_yid1…

RamblinRover Luxury-Yacht > ESSSIX GmbH - Accountant/Wagon Thumper 05/03/2016 at 13:47

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I know just enough about springs to be dangerous, so I have what may be a foolish question: wouldn’t a progressive tender that had a higher top rate than your main spring make more sense? I.e. wouldn’t a lower top rate mean you run out of tender spring a long, long time before you get seriously into the main spring? I would think the ideal mix would be starting with the tender compressing, then the overall balance shifting to your main spring so they both reach minimum height around the same time, but then again I know barely more than jack and shit about tender spring setups.

d15b > ESSSIX GmbH - Accountant/Wagon Thumper 05/03/2016 at 13:51

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I’m a fan of progressive springs, especially if it isn’t a RACECAR.

RallyWrench > ESSSIX GmbH - Accountant/Wagon Thumper 05/03/2016 at 14:32

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Most of the time, helper springs are a smaller diameter and end up fully compressed pretty quickly, even just under the car’s weight, and primarily exist to keep the main spring from rattling on or coming off its seat under rebound (ie over a crest) as some coilover setups tend to do. Also, the helper spring will likely be mostly compressed at ride height, probably even before the car is on the ground depending on how much travel you have to play with when setting the ride height, so you don’t even get most of its progressive rate. The helper has to bind before the main even comes into play, so that can make for some odd transitions if it’s too stiff. In short, helpers are a compromise at best. A 600lb spring on a 4000lb car shouldn’t ride too badly if you set the dampers soft. What’s keeping you from just getting longer main springs? Eibach makes an almost infinite selection of lengths for popular diameters.

ESSSIX GmbH - Accountant/Wagon Thumper > RallyWrench 05/03/2016 at 15:25

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I fell in love with the idea of progressiveness of the tenders. (tho im sure you know: tenders do not compress under normal vehicle load like helpers.) I know I could just dial in the rebound, but I feel this can afford more comfort at the same time. The tenders Im looking at are for Eibach: 0200.250.175-550 and the main spring (F) 0400.250.0600

ESSSIX GmbH - Accountant/Wagon Thumper > RamblinRover Luxury-Yacht 05/03/2016 at 15:41

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Think of it as a hand off from softo to hard be for you get to the main hard spring. So on a smooth road the spring rate is low, but once you load a corner lets say, it goes from soft to hard “progresivly” instead of all at one (for the case of linear springs). So to recap: a tender is open at normal load, and it closes at a predetermind load, in this case 550lbs, fromt the point that it closes the main spring takes over at 600lbs.

ESSSIX GmbH - Accountant/Wagon Thumper > OPPOsaurus WRX 05/03/2016 at 15:44

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Haha I might put air on a ‘82 sl380 I just got... might even throw the fikses on! Same bolt pattern as the audi!

I did find out recently that they have a coilover/bag combo, so you ride on coils, and raise the car when needed! But I cant justify putting mony into air lol. Not unless its an allroad to begin with LOL

RamblinRover Luxury-Yacht > ESSSIX GmbH - Accountant/Wagon Thumper 05/03/2016 at 15:54

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I understand perfectly well the idea of a progressive spring rate - what I was unclear on was what the minimum operating height of the tender spring was. Most coil springs can’t go coil to coil smoothly or in some cases even safely, which was why I asked what I did - whether a different choice permitted a cleaner transition zone and whether the tender was supposed to fully collapse. In any case, if one spring is on top of the other it’s not quite so simple as the first spring compressing all the way first. You’d have a compound deflection.

RallyWrench > ESSSIX GmbH - Accountant/Wagon Thumper 05/03/2016 at 16:01

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I’ve run into the tender/helper disconnect before, people refer to them differently. I was taught that the wimpy little “keeper” springs are tenders, and the ones with actual rate helpers. Still, they’ll end up partially compressed under the car’s weight so you don’t have as much of that progressiveness to play with as their length would suggest. So your tender is 2" long, and the main 4"? I don’t see you getting much advantage out of it depending on your ride height setting. But, the nice thing is if it doesn’t work just right you can get a longer main.

ESSSIX GmbH - Accountant/Wagon Thumper > RallyWrench 05/03/2016 at 16:28

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Haha funny you should say.. that make ways more sense, but even Eibach calls them tenders... Weird. No the tenders are 4.25" I could go to 250-550 and that would be 4.84"

Based on what other who have gone the fab route, you need “8 of spring, and then you set the ride height accordingly. Im not looking to stance, probably looking to keep the look I have now, if anything a little less in the rear. (keeping it reaked though)

RallyWrench > ESSSIX GmbH - Accountant/Wagon Thumper 05/03/2016 at 16:36

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Huh, ok. That makes more sense then. I thought Eibach’s numbering system was 0100=1.00" and so on, ie 0200.250.175-550 is 2" length, 2.5" diameter, 175-550lb rate,and a 4.25" spring would be 0425.250.175-550. Maybe that means travel and not free length.

ESSSIX GmbH - Accountant/Wagon Thumper > RamblinRover Luxury-Yacht 05/03/2016 at 16:36

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Ah you’re absolutely right! Thats where spring spacers and thrust washers come into play, I learned! Im learning suspension is amazingly complex, and like you said most know enough to be dangerous LOL.

The cars weight shifts, the springs take that energy, wichcraft happens, and then you go around the bend faster without rolling over.

RamblinRover Luxury-Yacht > ESSSIX GmbH - Accountant/Wagon Thumper 05/03/2016 at 16:40

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I’m not doing anything too complex with the Ranchero’s suspension. Wait, that’s a lie. I’m not doing anything too complex with the springs (400lb/in QA1 springs on QA1 coilovers front, pieces to make that fit, SIII XKE springs on old XJS shocks in back, done and done) but I’m making the top mount points adjustable.

ESSSIX GmbH - Accountant/Wagon Thumper > RallyWrench 05/03/2016 at 16:43

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Yea, it made sense to look at it that way. Anyways so what do you think now? Make sense? I couls also go for a higher rate for the main spring But I was told that there shouldnt bee to big of a difference between the main spring and the tender else it will be obvious when you fully compress the tender and are one the higher main spring rate. That way its more like a hand off from one to another.

RallyWrench > ESSSIX GmbH - Accountant/Wagon Thumper 05/03/2016 at 17:11

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That does make more sense with a longer tender. I was picturing a very short setup on a very low car. You’re right on the spring rate difference, it shouldn’t be too great. My earlier statement should have said too soft instead of too stiff when referring to weird transitions. Obviously a large difference between the max of the progressive spring and the main rate would negate any benefit of having a progressive spring in the first place, because you’d just have a big hole in the middle. In any case, I’m really interested to hear how it comes out.