Cheap L300 torsion bar upgrade

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Growlerbearnz
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Cheap L300 torsion bar upgrade

Postby Growlerbearnz » Fri Sep 07, 2018 2:57 pm

The stiffness of the torsion bar remains the same regardless of where you set the ride height. Consider how the torsion bar works: the back end is fixed in place, the front end is attached to your upper wishbone. Apply weight to the wishbone and the torsion bar twists until the springiness of the bar opposes the weight on the wishbone.

When you rotate the fixed end to wind up/down the ride height, the wishbone end rotates by the same amount- you haven't added any extra twist to the bar, you've only changed the orientation of the wishbone. There might be some minor effect because the wishbones are on slightly different angles (more/less leverage on the torsion bar) but it's going to be subtle.

I can't recall, did you fit the new torsion bars and new shock absorbers at the same time? I have the 24mm bars but I kept my old shock absorbers. The ride is only slightly changed off road, definitely not too harsh. The main thing I notice is that it bottoms out more gently (whereas with the 20mm bars it bottomed out with a bit of a crash) and feels like it rebounds a bit higher.

I suspect it's your shocks that are creating the harshness- if you still have your old shocks, maybe try swapping them back in and see how it goes.
Nothing says "poor workmanship" more than wrinkles in the duct tape.

sk66
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Cheap L300 torsion bar upgrade

Postby sk66 » Sat Sep 08, 2018 9:00 am

I guess that makes sense as there is nothing else really supporting part of the weight... but it does seem to me that you have to twist the adjustable end more than the resulting adjustment at the opposite end. Maybe because the wheels/weight have greater leverage (distance/arm) on the torsion bar... if it was a direct 1:1 I would expect that to be the opposite. But maybe that's just an impression I got; I haven't measured or studied the mechanics/geometry. Are torsion bars constant rate springs, does it even matter? You're probably right... if there is any difference it will probably be subtle at best.

I changed them in short sequence, torsion bars first. The shocks almost certainly made an additional difference, and being gas charged (dual chamber) probably makes a difference as well. But I didn't do a lot of driving in between. The OEM's were worn out; next to no resistance. So I don't have a reference for "as designed" OEM characteristics.
Steven
1991 L300
Harrisburg, PA

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Growlerbearnz
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Cheap L300 torsion bar upgrade

Postby Growlerbearnz » Sat Sep 08, 2018 3:41 pm

sk66 wrote:Are torsion bars constant rate springs, does it even matter?


Torsion bars are almost perfectly constant rate. The bump stops are designed to decelerate the suspension progressively at either end.

Ah, the joy of modifying cars- fit all the fun stuff, create a whole new set of issues, swap parts out until compromise is reached. I find my front suspension is still a bit too bouncy for road use, even with the new torsion bars. I'm currently waiting for a set of Rancho RS9000XL adjustable front shocks to arrive, the idea being that I can set them to stiff when towing the caravan, medium for around town, and soft for off road. We'll see how well they work.
Nothing says "poor workmanship" more than wrinkles in the duct tape.

sk66
Posts: 133
Joined: Thu Oct 06, 2016 3:24 pm
Member's Photo Album: http://www.delica.ca/Photos/
Vehicle: '91 Delica L300
Location: Pennsylvania, USA

Cheap L300 torsion bar upgrade

Postby sk66 » Mon Sep 10, 2018 2:35 pm

Growlerbearnz wrote:the idea being that I can set them to stiff when towing the caravan, medium for around town, and soft for off road. We'll see how well they work.

Medium for everything :-D . I highly doubt I would crawl under the van to adjust them unless it makes a BIG difference.
Steven
1991 L300
Harrisburg, PA


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