Rear spring length, suspension droop, ride height, etc

[aeronaut]

Trying 800#, 6" springs in the rear.
On this current setup, I'd really like to go another 1/2-3/4" lower ride height, but I don't like the spring not being completely captured at full suspension extension.

But, I'm here:

springrear.jpg

How do you folks running 5.5" rear springs and/or low ride height prevent the spring from coming out from under the capture points?

I see Rogue now has these....do they work? Other options?

Screenshot from 2020-09-05 13-52-53.png

[eacmen]

Unless you're launching the car in the air Evil Kneival style I wouldn't worry about it. Just make sure they are lined up as you lower the car to the ground after jacking it up.


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[aeronaut]

Yea, Shenandoah at Summit Point. They call it the 'ski jump' for a reason. All four off the ground under the bridge.

[eacmen]

Yea, Shenandoah at Summit Point. They call it the 'ski jump' for a reason. All four off the ground under the bridge.

I've driven Shen with short rear springs. Was not an issue.


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[aeronaut]

I have too. But if I can buy insurance that a spring won't unseat, I'm all in.

[eacmen]

I have too. But if I can buy insurance that a spring won't unseat, I'm all in.

Only solution i can think of is find RSMs that will shorten the damper travel to limit full droop. However if the damper isn't designed for it, that may compromise the performance.

I haven't seen the RE product before, but Looking at it i can't see how that white part is held into place. Seems like it would fall out rather easily. I could be looking at it wrong tho.

I suppose a tender spring will work but it will also add to the overall stack height 1/2 inch or so, thus raising the car.


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[aeronaut]

I struggle to see how the RE piece would hold in any situation also.
I have thought about extended RSMs. GC makes some.

I don't see how tender springs would work in this case, nothing to hold them in place either. But the 1/2 raise would be adjusted out using adjusters (already in place), and/or a 1/2" shorter spring.

My concerned was heightened when I raised the car, lowered it, and heard a rear spring 'pop' into place. It was obvious it had slipped off the top perch and gotten caught until enough car weight forced it into place.

[MINIz guy]

I run a 120mm rear spring with a helper spring so nothing is unseated at full droop. The helper spring and coupler add about .75" to the stack height. It doesn't coil bind as it is a 913lb/in rate spring. I believe everybody else that it shouldn't unseat on track, but I'm just lazy and don't want to deal with making sure everything is centered when raising/lowering the car.

Other details are GC weight jacks, wheel arch at the top of the tire for ride height.

I have run a 140mm 800lb rear spring at the same ride height without the need of a helper spring. The nub on the body just holds the alignment cone in place. I have also run a 100mm 971lb spring with a helper to get the rear really low, but it will coil bind.

[aeronaut]

Great info, and very helpful, thanks!

[eacmen]

I struggle to see how the RE piece would hold in any situation also.
I have thought about extended RSMs. GC makes some.

I don't see how tender springs would work in this case, nothing to hold them in place either. But the 1/2 raise would be adjusted out using adjusters (already in place), and/or a 1/2" shorter spring.

My concerned was heightened when I raised the car, lowered it, and heard a rear spring 'pop' into place. It was obvious it had slipped off the top perch and gotten caught until enough car weight forced it into place.

FWIW every time I lower the car to the ground The rear spring always "pops" into place. As long as you pay attention while lowering the car its safe IMO.


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[aeronaut]

FWIW every time I lower the car to the ground The rear spring always "pops" into place. As long as you pay attention while lowering the car its safe IMO.


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Of course. Raising/lowering on the lift isn't the concern.
Both rear wheels off the ground while on track is the concern. And that does happen on several tracks, or during an off.

[eacmen]

Of course. Raising/lowering on the lift isn't the concern.
Both rear wheels off the ground while on track is the concern. And that does happen on several tracks, or during an off.

Hopefully someone with more experience can chime in but I don't think even on those tracks the car is in the air long enough to reach full droop and the damper rebound is acting against the spring from pushing the tire down too quickly. The anti roll bar also acts against the wheel from reaching full droop.

I don't want to say its not something you should worry about but I have had several specialty racing shops work on the car and none of them thought its an issue.

You could also switch over to true rear coilover and this problem goes away.


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[pshooter]

The right side of my car is fully off the ground over the curbs entering the bus stop at the Glen. I've never had an issue. At NYST I get all 4 off the ground over wheelie hill no issue.

[olemiss540]

I have seen someone here use a 3" long heater hose section clamped over the top spring centering nipple as a spring retainer of sorts. Seemed like a smart idea to me!

[aeronaut]

I like!

[jayjaya29]

You could install droop straps from the lower shock bolt to the body somewhere. I've seen people use seatbelts or ratchet straps.

Personally, I run mid 1980s 911 Koni shocks (Koni 8210-1159SPORT) which have way less droop then the e36 m3 konis. Keeps the spring compressed throughout the entire travel of the suspension.

[aeronaut]

I had a set of those p-shocks years ago, and let them go!!! I'd forgotten about them.

I think I have an interesting/cheap fix on the way. If it works, I'll report back.
But good reminder on the straps, thanks.

[NeilM]

The E36 has a weirdly narrow window of rear spring length, spring rate, ride height adjuster design and target ride height that all work together acceptably for track use. Use a longer spring and you may run out of ride height adjustment, but a short spring can go loose at full droop.

My car had the dreaded loose spring syndrome that could allow a rear spring to unseat and fall out at full droop if the entire back end of the car was lifted for tire changes (jacking one corner at a time allows swaybar pressure to retain the lifted corner's spring). I also drive at Grattan Raceway (near Grand Rapids, MI), where the notorious jump between T4 and T5 can definitely be an all-wheels-in-the-air event. After much experimentation, and no small amount of discarded parts, here's what works for me:



Springs: 6"/700# Hypercoil 60mm (https://www.bimmerworld.com/Hypercoi...l-Springs.html)
Tender spring: 60mm "zero rate" Hypercoil (https://www.bimmerworld.com/Suspensi...ing-Set_2.html)
Spring coupler: 60mm (https://www.bimmerworld.com/Suspensi...ide-Set_3.html)
Shocks: TC Kline/Koni DA (https://www.tcklineracing.com/webdoc.../Details47.cfm)
Lower spring perch: Rogue Engineering articulating, length adjustable from below (https://www.rogueengineering.com/Rog...Pair_p_76.html)
Upper spring perch: Rogue Engineering alignment perch (https://www.rogueengineering.com/Rog...rch_p_123.html)
RSM: Rogue Engineering, standard configuration (https://www.rogueengineering.com/Rea...le-_c_406.html)

Notes
• If using extended conical perches at both top and bottom you need to check that they won't hit each other at full compression (ask me how I know...)
• Obviously you don't have to use an articulating perch, but it's a nice-to-have. Worth noting that the useful adjustment range with this type of perch is reduced by the need to maintain clearance for the conical seat to angulate without its edge striking the control arm.
• Softer spring rates may need a longer free spring length to maintain a rational ride height.
• Stiffer spring rates may need a shorter free spring length, depending. Both Hypercoil and Swift offer 5.5" springs in 60mm.

I don't imagine for a moment that this is the only solution to the E36 rear spring equation, but it's one solution. It should work for a decent range of racing spring rates.

Neil

[eacmen]

I just realized this was an E36 thread. Ignore everything I said as I am in an E46.


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[aeronaut]

I just realized this was an E36 thread. Ignore everything I said as I am in an E46.


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I'm pretty good at putting my car type in my first post when I ask a question like this..and failed to this time. Pisses me off when other don't. LOL.

- - - Updated - - -

The E36 has a weirdly narrow window of rear spring length, spring rate, ride height adjuster design and target ride height that all work together acceptably for track use. Use a longer spring and you may run out of ride height adjustment, but a short spring can go loose at full droop.

My car had the dreaded loose spring syndrome that could allow a rear spring to unseat and fall out at full droop if the entire back end of the car was lifted for tire changes (jacking one corner at a time allows swaybar pressure to retain the lifted corner's spring). I also drive at Grattan Raceway (near Grand Rapids, MI), where the notorious jump between T4 and T5 can definitely be an all-wheels-in-the-air event. After much experimentation, and no small amount of discarded parts, here's what works for me:



Springs: 6"/700# Hypercoil 60mm (https://www.bimmerworld.com/Hypercoi...l-Springs.html)
Tender spring: 60mm "zero rate" Hypercoil (https://www.bimmerworld.com/Suspensi...ing-Set_2.html)
Spring coupler: 60mm (https://www.bimmerworld.com/Suspensi...ide-Set_3.html)
Shocks: TC Kline/Koni DA (https://www.tcklineracing.com/webdoc.../Details47.cfm)
Lower spring perch: Rogue Engineering articulating, length adjustable from below (https://www.rogueengineering.com/Rog...Pair_p_76.html)
Upper spring perch: Rogue Engineering alignment perch (https://www.rogueengineering.com/Rog...rch_p_123.html)
RSM: Rogue Engineering, standard configuration (https://www.rogueengineering.com/Rea...le-_c_406.html)

Notes
• If using extended conical perches at both top and bottom you need to check that they won't hit each other at full compression (ask me how I know...)
• Obviously you don't have to use an articulating perch, but it's a nice-to-have. Worth noting that the useful adjustment range with this type of perch is reduced by the need to maintain clearance for the conical seat to angulate without its edge striking the control arm.
• Softer spring rates may need a longer free spring length to maintain a rational ride height.
• Stiffer spring rates may need a shorter free spring length, depending. Both Hypercoil and Swift offer 5.5" springs in 60mm.

I don't imagine for a moment that this is the only solution to the E36 rear spring equation, but it's one solution. It should work for a decent range of racing spring rates.

Neil

Thanks Neil, excellent information as usual.
When I first asked this question, I didn't realize there was such a thing as a coupler for spring-to-helper.
That opens up a lot of options, and a lot of trial-and-error.

[hello1]

hello and hope you and your family are safe and healthy. Sorry to trouble you but can you let me know how thick the genesis spring coupler you used between the main and helper spring is? Trying to see how much that coupler thickness is between the main spring and helper compared to a regular style spring coupler/isolator. Thank you so much

The E36 has a weirdly narrow window of rear spring length, spring rate, ride height adjuster design and target ride height that all work together acceptably for track use. Use a longer spring and you may run out of ride height adjustment, but a short spring can go loose at full droop.

My car had the dreaded loose spring syndrome that could allow a rear spring to unseat and fall out at full droop if the entire back end of the car was lifted for tire changes (jacking one corner at a time allows swaybar pressure to retain the lifted corner's spring). I also drive at Grattan Raceway (near Grand Rapids, MI), where the notorious jump between T4 and T5 can definitely be an all-wheels-in-the-air event. After much experimentation, and no small amount of discarded parts, here's what works for me:



Springs: 6"/700# Hypercoil 60mm (https://www.bimmerworld.com/Hypercoi...l-Springs.html)
Tender spring: 60mm "zero rate" Hypercoil (https://www.bimmerworld.com/Suspensi...ing-Set_2.html)
Spring coupler: 60mm (https://www.bimmerworld.com/Suspensi...ide-Set_3.html)
Shocks: TC Kline/Koni DA (https://www.tcklineracing.com/webdoc.../Details47.cfm)
Lower spring perch: Rogue Engineering articulating, length adjustable from below (https://www.rogueengineering.com/Rog...Pair_p_76.html)
Upper spring perch: Rogue Engineering alignment perch (https://www.rogueengineering.com/Rog...rch_p_123.html)
RSM: Rogue Engineering, standard configuration (https://www.rogueengineering.com/Rea...le-_c_406.html)

Notes
• If using extended conical perches at both top and bottom you need to check that they won't hit each other at full compression (ask me how I know...)
• Obviously you don't have to use an articulating perch, but it's a nice-to-have. Worth noting that the useful adjustment range with this type of perch is reduced by the need to maintain clearance for the conical seat to angulate without its edge striking the control arm.
• Softer spring rates may need a longer free spring length to maintain a rational ride height.
• Stiffer spring rates may need a shorter free spring length, depending. Both Hypercoil and Swift offer 5.5" springs in 60mm.

I don't imagine for a moment that this is the only solution to the E36 rear spring equation, but it's one solution. It should work for a decent range of racing spring rates.

Neil