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progressive rear springs with linear front springs

sloopy

2-digit whp
Joined
May 25, 2020
Location
Dallas, Texas
I have a 1992 240 wagon with ben's coilover setup. 250 lb/in front, 150 lb/in rear. I was curious about using a progressive spring in the rear as it might help keep the car more level with a large load in the rear. I believe the lesjofors sport spring kit is linear rate front, progressive rate rear. I wonder why? Has anyone run this kind of setup before?
 
Progressive in the rear can help with load capacity but the lesjofors rear springs are very soft and will have you sat on your bump stops with two passengers in the back.
 
Any advice on choosing a progressive spring rate? Let's say I like my 150 lb/in rear springs. I see a 125-300 lb/in spring from landrum (LANJ125-300). I guess this means it's 125 lb/in uncompressed, and progressively increases to 300 lb/in when fully compressed. Is this increase in stiffness linear? As in, assuming there is 10" of compression, will the spring be 212.5 lb/in at 5" of compression? When choosing a progressive rate, should I choose a rate that will put me near my comfortable 150 lb/in with the normal weight of the car sitting on it?
 
Is there ia 150-300lb spring? I don't think a progressive spring is linear. You'll use up the soft progressive spring section with a heavy load and then you are using the stiff 300lb part of the spring. Personally, I would want something like the 150lb rate but only stiffen up to 200lb. Remember the rear spring rate is 1.5 times the spring you use.
 
I haven't seen a 150-300 lb/in spring yet. I'm having trouble finding a nice catalog of progressive 5" od springs. Anyone know of a good resource?
 
Progressives can?t be linear. They are non-linear.
The progression also can?t be a beautiful straight line or curve. As the wires touch they increase, up to the bump stops. If they were allowed to fully bind, they would break. Ask any valve spring.
They are a compromise spring.
I personally like a lot less of the soft section than most progressives have, say one coil. I made some for a corolla, but on volvos i use linear springs, 200-275 in rear, 300-425 in front.
 
In most cases the soft end is fully closed with the weight of the car. They do not really give you a soft section for normal use getting harder with extra load like you would expect. They do help with droop travel and can provide a slightly less harsh ride.
 
In most cases the soft end is fully closed with the weight of the car. They do not really give you a soft section for normal use getting harder with extra load like you would expect. They do help with droop travel and can provide a slightly less harsh ride.

What do you mean they help with droop travel?
 
What do you mean they help with droop travel?

Loaded spring with 3? travel at 150# spring and 5? at 300 has used up most of the 3x150 with the weight of the car and isn?t an 8? spring it?s more like 6. Pothole unloads tire, ride height stays same, but you get to use your extra 2? of spring. Easing the harshness of the drop.
 
Progressive in the rear can help with load capacity but the lesjofors rear springs are very soft and will have you sat on your bump stops with two passengers in the back.

How much did they weigh? :eek:) Is it really so bad? They don't seem to be significantly softer than what I already have in the rear (150 lb/in). Is it just really low? I don't have a stock height reference anymore so I don't know what the alleged 40mm lower would look like.

Here is the spring data for the lesjofors sport spring kits:

Lesjofors 4595804
240 sedan sport kit (35 mm lower)
---
front: 29 N/mm (166 lb/in)
rear: 26-35 N/mm (147-200 lb/in)


Lesjofors 4595805
240 wagon sport kit (40 mm lower)
---
front: 29 N/mm (166 lb/in)
rear:23-33 N/mm (131-188 lb/in)
 
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Here is my car with the B&G springs and Koni struts/shocks and 205/65-15 tires

<a href="https://ibb.co/6XwMmqm"><img src="https://i.ibb.co/CP8czSz/IMG-20220902-172256489.jpg" alt="IMG-20220902-172256489" border="0"></a>
<a href="https://ibb.co/vLZgtNw"><img src="https://i.ibb.co/VM2rKFj/IMG-20220902-172328443.jpg" alt="IMG-20220902-172328443" border="0"></a>
<a href="https://ibb.co/1d7m4J2"><img src="https://i.ibb.co/X3jCGkJ/IMG-20220902-172335792.jpg" alt="IMG-20220902-172335792" border="0"></a><br /><a target='_blank' href='https://poetandpoem.com/Robert-William-Service'>robert w service biography</a><br />


I don't know much about the spring specs but the car drives great and isn't draggin' ass when I'm towing my trailer. I also haven't driven a pure sports car but it feels pretty balanced in the corners to me. When I start hearing some tires squealing it's definitely in the rear so I'm pretty sure it would oversteer if it ever slid out. For that reason I have no interest in a stiffer rear anti-sway bar.
 
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