The Stovebolt Site Forums The Shop Area The HiPo Shop Modified front suspension & driveability issues

my son is having issues with handling after lowering the suspension on his 49 3100. He wanted the lowered look so we installed a dropped front axle and removed some leaves from the springs on front and rear. Installed modern style shocks, front sway bar and power steering conversion with a 70's integral steering box. The truck now seems too light and bouncy in the front end. Would air bags or air shocks help or any other solutions? Dave V

How much pressure are you running in the tires? You also might need a stiffer valved shock to dampen the spring action.

Do you have any shims between the axle and the springs? When I got my dropped axle from Sids, he recommended (IIRC) 7 degrees.

My '51 3100 was lowered by the PO years ago, but he did it the old school way. He heated the original springs till it sank to where he wanted it, which is how it still is. It rides fantastic. It takes bumps, even railroad crossings, better than my last 4 trucks, which have been '82 - 95's. The shocks are the OEM type, too. Original everything.

Not sure of tire pressure. Will check that and stiffer shock availability. As far as shims, would this be to change caster (positive or negative)? Dave V

Hi,

I removed a couple of leaves from each side on the front of my '56 and it was too soft. Ended up putting one back. If you added teflon liners between the springs, it can make it more bouncy as well since the friction between the leaves is much lower. My preference is to get lowering springs. I did that on the rear and am very happy with it.

Yes,caster shims are to change caster angles,it's all to do with KPI (king pin inclination)
My understanding is positive caster will produce lighter steering but will also affect the steerings ability to self center.
Negative caster will ultimately make the steering slightly heavier but it will track much straighter.

I sent an e-mail to Sid to see what he recommends for caster shims. Dave V

I let corrosion and 60 years of hard life relax my springs for a softer ride.
Carl

[quote=jockbolter50Yes,caster shims are to change caster angles,it's all to do with KPI (king pin inclination)
My understanding is positive caster will produce lighter steering but will also affect the steerings ability to self center.
Negative caster will ultimately make the steering slightly heavier but it will track much straighter. [/quote]Other way around. Positive caster produces heavier steering and better self centering, negative caster makes for easier steering, but less self centering and stability. Most vehicles use positive caster, but there are a few exceptions, mostly '60s Ford products.
The KPI doesn't really have much to do with caster, it's related to camber, steering axis inclination, included angle, and scrub radius.

I stand corrected Bill,my understanding was negative caster meant the axle would be tilted back towards the cab and positive was forward to the radiator.
I was also led to believe the KPI was the kingpins relation to vertical on the fore and aft plane too.....

To use an old quote: If you believe all you hear,you'll eat all you see"
I guess I should've researched it myself.....

Dave,my apologies for the mis-information,thankfully Bill (Longbox) put me straight.
'Scuse the pun!

I suppose that also harks back to the Stovebolt mantra.... "knowledge is the best resource"

I received a reply from Sid. He says to use 4-6 degree positive caster (thick part of wedge to rear of truck). I've been thinking backwards I guess. I thought putting the thick part of wedge to the back would give it negative caster. He did give a NAPA part # for the 4 degree shim so they should be easy to get. Thanks Dave V

Installed the 4 degree caster shims last night and used a caster/camber gauge after installation. Reading 1 3/4 degrees positive on each side. Did not have the gauge to do a before reading. Will check into stiffer shocks today and install before I test drive it. Will reveal results then. Dave V