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do unweighted overload springs affect handling?

If a car is standing on it's wheels those springs will never be 'unweighted'.
Can they change grip levels? Yes, offcourse they can.
But what do you consider to be substantial? It's not like the car will start to oversteer in every corner. Not if you drive the car sensibly.

When a car factory sets up the chassis of a car they try to find a good balance between comfort and grip and they also try to optimise traction and dial in some understeer ( the tendency to understeer is safe for the averidge driver). For this they make choices for front and rear springrates.

By installing overload springs you are modifying the balance of that factory setup. (mind you, all setups including the stock setup, are chosen compromises)
Overload springs are harder springs so they lower comfort when not carrying loads and make the car oversteer easier. But only when you are cornering the car hard on wet or slippery surfaces.
Also in corners without load the traction will be less if the car only has an open differential. The inside wheel will have the tendency to spin easier when you are rounding a corner (more so on wet or slippery surfaces)

If your particular car already has a anti-sway bar installed on the rear axel then you could install the overload springs and to compensate completely remove the anti-sway bar. That way the car would still have the better load carrying capability but also enough grip and traction to be safe and reasonably nice to drive while not loaded.

Another way to increase load carrying capability would be to install inflateable shock absorbers. The air in those shocks acts as additional springs. By adding air you could adapt the ride height yourself whenever you need to carry a heavier load. Then when the car is empty again you just lower airpressure in the shocks again. I think Monroe sells these kind of shocks.

The Sachs Nivomat shocks do this automatically. Volvo offered them on many models. But those shocks are expensive.
 
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I haven’t noticed any compromises with handling grip. Around town the rear definitely feels more sprung than the front, but at speed on smoother roads with bumps and dips that compress the suspension it feels more balanced and neutral. The rear of a 240 has a lot of unsprung weight, which I think is what contributes to what I feel when I drive (is the suspension compressing because I am on uneven roads pushing the axle up and compressing the spring, or is the weight of the car compressing the spring on some smooth windy backroads) If you were concerned about this you could tweak your sway bar setup, i.e. go bigger in the front and or smaller in the rear.
 
Tried overload springs w/Bilstein HD and TC shocks in my wagon (which also has a 25mm front and 22mm rear anti-sway bars)
Removed the springs because they were to stiff over bumps with no cargo and created too much oversteer.
They felt great on straight roads with no bumps and when loaded with cargo.
 
Those are a progressively wound spring. I doubt they have any affect on the car's handling under normal driving conditions.

That is exactly the feedback I heard from a local TBer who runs these on a 245.

On th other hand, I'm running a Swedish made 14mm rr sprng and learned that if I got over a speed bumb I need to slow way down or go airborne. The 14's combined with Lesjofors 14.2 mm(advertised as 14.5mm) up front make for a fun ride, with no problems hauling cargo.

:-P
 
I never found the old single rate ipd overloads all that crazy?
The Volvo 240 replacement exhaust goes over the axle so no big deal there?
Only raises the rear a tiny bit, tho you kinda want the rear to sit slightly low on these for balance, as long as it doesn’t bottom out…
…so ya, little compromise unloaded?

The late model front springs are a bit taller/stiffer 92+ 240s (typical Volvo they finally got the ‘all around compromise’ mostly right after making the stupid cars for 20+ years for snow/breakaway predictability, comfort etc etc right before killing off the model :roll:) & even the late n/a models got a little larger front sway bar, wagons still have a nice small rear bar.

You can do the airbag dance (& Volvo offered it with speshl shocks (I have the pump & controller) , and it can pick the thing up a bit so the headlights aren’t aimed at the sky, but it won’t necessarily make the damping or spring rate appropriate for the load with just a bag alone. Better than nothing?

For that you probably need some sort of hydra pneumatic nitrogen rubber dampened bomb & complicated valving or pump like the Citroen or MbZ wagons used, for better and worse?

Or the very expensive Sachs-Boge branded nivomat sprung shocks used in the Volvo with internal pumps?

Interesting compromise by Sachs/Boge; but kinda sux that the regular spring is so weak in that design for wear parts in the implementation & that the pumping action is part of the shock in some ways (imo just the shock absorber should be the wear part, reasonably priced & rebuildable?…not wearing out other suspension rubber with where the shock is maybe mounted or stressing out other parts & the waste or having to buy essentially a whole pump/shock/spring variable valving thing & have it deflate instead of just being able to install regular junkyard shocks & airbag as needed?
 
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Timely thread since I have been thinking on doing the same to my 744. I put used wagon springs + new Bilstein HDs on it but now if sags some; the fact I have been carrying parts and tools in the trunk lately does not help much. So I have to decide if (a) I just need new wagon rear springs to put it back the way it was or (b) get the overload ones.
 
In my 740 pickup with ipd bars, overload rear coils, Bilstein HD's, stock LSD (all new this past year suspension bushings, balljoints, etc.) the handling is very good. With no load in the rear I've only experienced unwanted oversteer when taking exit ramps at excessive speed in pouring rain, dry pavement I can go through 20-25mph highway exit ramps at 50-60mph & it's all good.
 
when I did my Mercedes spring swap, those were super stiff if I didn't have any weight in the 245.Bouncy but still managable.
I used it for a work vehicle, 500lbs of tools almost always in it. If I recall those were 16mm non progressive springs.

A long time ago I hadf my 745 having with overloads, and all the ipd rear bits in it. I would always load it with tools. sometimes another 500lbs of other stuff and plywood on the roof racks.

Then I had the bright idea of putting load E tires in the rear. no weight in it and the car was very squirelly above 60mph.
 
when I did my Mercedes spring swap, those were super stiff if I didn't have any weight in the 245.Bouncy but still managable.
I used it for a work vehicle, 500lbs of tools almost always in it. If I recall those were 16mm non progressive springs.

A long time ago I hadf my 745 having with overloads, and all the ipd rear bits in it. I would always load it with tools. sometimes another 500lbs of other stuff and plywood on the roof racks.

Then I had the bright idea of putting load E tires in the rear. no weight in it and the car was very squirelly above 60mph.
...long way around the block? :lol:

700 guys...JY 200 rear series springs make good poor mans overloads for those, actually?
Surprised you cheap lazy 700 guys couldn't be bothered to figure that one out...
200 springs very by year/options obviously...diesel, turbo, early, late...
I used 240 sedan springs on 700 sedans & early (pre 1980 & soft) 245 rear springs as a 'light' overload on 7x5s with good results.

245 I kinda had to buy/find the overloads. Previa coils are a bit much, stock car racing springs with perches are doable but I like the pigtailed springs as volvo did them...call me weird?
 
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