So, on a scale of "Meh" to "Dude, you're gonna die by death wobble"

[glaser06]

Agreed on the jeep. I've got a '92 MJ that has to have near perfect balance to be road worthy because of the lift. My solution was 2 sets of wheels for it, one for driving and one to beat on wheeling.

I wish I had room for a balancer, my lift, parts washer, blast cabinet, power coat oven, etc barely fit as it is!

P.S. I like the 2x4 analogy. I'm a mechanical engineer working in metallurgy and vibratory analysis, so being able to break like that is something I'm always looking for. Probably one of the only ones on here to own 3 different types of handheld tachometers... that's before my automotive toolbox gets opened!

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[glaser06]

Oh and my tires have never been mounted at a tire shop. I always do that myself! (That's why I have 4 trucks!)

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[The FLU farm]

Jeez, glaser06, your Jeep is new compared to mine. Okay, at least 41 years newer.
Wish you lived closer. I'd gladly balance tires in return for getting to use your blast cabinet and powder coating stuff. But I do have a mechanical handheld tachometer that my dad gave me.
As far as the 2x4 analogy goes, apparently Hunter liked it enough to start using it in their classes, maybe even literature.

If you mount your own tires, you know to clean the bead areas of the rims very well, right? That's another thing tire shops rarely bother with, and can lead to balance issues.

 

[Barrman]

I brought up tire balance because of my M715. It is a closed knuckle D60. Not the same as yours. No stabilizer shock either.

Running ndt tires, I got death wobble 43-47 mph when in a turn. Also 52-55 mph if one front tire hit a bump. I could narrow the speeds it happened, but it still happened no matter what tire combination I had. I put a 396 big block in and found nailing the throttle would accelerate me out of the wobble. Something the stock engine couldn't do.

Then I got Michelin Xzl tires. All death wobble gone no matter the speed. All good for 3 years. While at a m715 gathering in Colorado I had a flat and another truck owner had a Michelin xl all mounted up. I had it on the right front. I drove to town to get fuel and got the worse death wobble ever in that truck as soon as I hit 30 mph. I put the borrowed tire on the back and one of my xzl tires on the front. All good again and no vibration at any speed up to 64 mph. Little tire differences can make huge differences in solid axle vehicles is my point.

 

[LastFbody]

Useful thing I learned is that with 100% stock suspension you can measure from the center of the hub to the top of the wheel well to see if all is well. On a Blazer (dont know about pickups) its supposed to be 22 1/2 inches on the front and 21 1/2 on the rear.

 

[glaser06]

I don't mount, but the shop I used before I moved did all my mount and balance (I put on vehicle). They were good about cleaning and inspecting the rims and tires and would let me watch while they did it. Also the only shop East OTP Atlanta I found that could properly do the 4 wheel alignment on my Fiero.

Swapped tires tonight.... mostly because my new Roboimpact came in today! If y'all don't have one, man you're missing out. No change in how the truck wobbles though :/

And yes, I inspected the hubs, tightened in the correct pattern, looked for missing weights, and checked pressure (glad none were low, I've only got the bike pump at the moment). Drove to wally world and still shook like before, only on braking and deceleration.

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[glaser06]

Somewhat related question. From center of hanger to top of arch, who has the most out of shape springs? I'm gonna measure mine tomorrow but I'm thinking I'm at least 2" below. How far is considered too far?

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[glaser06]

the military wrap is just a redundant system in the event the spring eye breaks I can assure you that wheel balance can cause issues with changing speeds. After many years of doing front end work I have seen this many times, also an easy way to check your spring bushings is to have to have some one move the steering wheel back and forth while you watch for movement at the spring eye. the rubbers can look good when they actually wont do their job.

I'll have to check my bushings out, I'm willing to bet they're shot. I'll also look for the spring eye damage while I'm under there. Didn't know the military wrap coming undone wasn't a big deal. Thanks.

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[rustystud]

I more meant the DS front hangar where the spring was coming unwound....

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That is normal. That second spring is meant to loosely wrap around the main spring as a safety measure if the leaf ever breaks

 

[The FLU farm]

Somewhat related question. From center of hanger to top of arch, who has the most out of shape springs? I'm gonna measure mine tomorrow but I'm thinking I'm at least 2" below. How far is considered too far?

It'd be a lot quicker and easier for everybody involved to use the method that LastFbody described above.
Center of hub to top of wheel well is a fairly universal way of measuring ride height, doesn't require getting underneath the vehicle, and works regardless of tire size.

 

[glaser06]

Hmmm...22" on drivers side, 22.5" passengers side center of hub to lower fender height. Less than 3/4" between spring and bumpstops. This about what everyone else has?

I'm having trouble believing that is stock height unless these are supposed to be reverse arch springs from factory.

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[doghead]

The sag over time.

How much spade between axle and bumpstop?

New front springs make a huge difference in ride quality.

 

[glaser06]

Where are the measurement points you're talking about doghead? I measured the ~3/4" between the bottom of the bumpstop and where it contacts the spring pack.

 

[Ilikemtb999]

Fenders can easily sag/move/misalign over the life of a vehicle. Measuring from bump stop pad (or end of bump stop if original)to the spring plate is more accurate

 

[snowtrac nome]

those trucks came new with springs that way, reverse arch springs were supposed to give a better ride

 

[The FLU farm]

Hmmm...22" on drivers side, 22.5" passengers side center of hub to lower fender height. Less than 3/4" between spring and bumpstops. This about what everyone else has?

I'm having trouble believing that is stock height unless these are supposed to be reverse arch springs from factory.

Checked the front of the M1008, which is at 22.5 and 22.75 inches. It's a low mileage unit.
For kicks, I also measured a 3/4-ton Suburban with a 6.2, which is at 22 and 21.75 inches.
Neither one has a droopy front front clip, which would be very evident when looking at the reveal by the door.

As mentioned, yes, GM designed them with reverse arch springs up front, which is why the shackles are in the rear.

 

[glaser06]

those trucks came new with springs that way, reverse arch springs were supposed to give a better ride

Where did you find this? All the civilian stuff I know has the springs arched at 1-1/8" positive.

 

[The FLU farm]

Where did you find this? All the civilian stuff I know has the springs arched at 1-1/8" positive.

WHAT?!? It's time you check the body builders books of the era, look up old road tests...or believe us.

 

[glaser06]

http://www.truckspring.com/products/GM-Pickup-Replacement-Leaf-Spring-(3-Leaves-Front)__22-402.aspx

http://www.rockauto.com/en/catalog/...350cid+v8,1053098,suspension,leaf+spring,7544

Positive arch unloaded is 1.125". Near flat installed, can't find measured pictures/specific specs on install. The K5-K30 all used the same front spring sets thru the 1980s, so I would assume the amount of arch would vary depending on motor (SBC, BBC, or Detroit). A 305 equipped K5 base likely had 2-300 lbs less weight on the front axle (dry engine weight 575 vs 650, plus smaller radiator, no 2nd alternator, and a much smaller frame sitting atop it) meaning a "more positive" installed arch. Can verify this from personal experience, pulled many off in my younger years.

 

[The FLU farm]

The K5-K30 all used the same front spring sets thru the 1980s, so I would assume the amount of arch would vary depending on motor (SBC, BBC, or Detroit).

Darn, that would mean that someone stole the third leafs off of my M1009s, and the 3/4-ton Suburban.
Bought a '91 K-30 new, so thankfully that one still had its third leaf.
But then there's an '85 3/4-ton Suburban, a project vehicle which I picked up new, and it was missing its third leaf, too.