Am I thinking about this correctly..."static" flex?

[AJMBLAZER]

I'm almost done with making the 11.00R16's (38x11ishR16's) fit on Big Ugly and have done a little bit of flex testing via my jack and the truck's weight.
The rears will clear fine.
The fronts I have concerns about but I've lifted the truck up by the axle so high that the whole truck is off of the stands under the frame. To me this means the suspension is compressed fully...correct?

No rub so I think I should be good...

 

[Bent77]

The only thing you didn't mention is full wheel travel when steering and "bump compression" if you will.

When I first trimmed mine and tested it the way you mention, the first time I had the wheels turned and dropped the weight on the front, it munched up the tire.

Also probably most important is the relation of your bumpstops when you had it jacked up.

 

[Hogback Fabrication]

You will need to trim more than you think you have to.

I tested mine by driving one tire up on the trailer fender (~3 vertical ft.) and had no clearance issues. I've had it out a few times since then and it rubbed the on the first trail. So I cut it more. Still rubbed the next time out.

You just can't load the suspension with a ramp/jack like it will be loaded on the trail.

You're probably better off cutting more than you need. Otherwise you may let the tires do the clearancing for you

 

[original balzer]

You will need to trim more than you have to.

I tested mine by driving one tire up on the trailer fender (~3 vertical ft.) and had no clearance issues. I've had it out a few times since then and it rubbed the on the first trail. So I cut it more. Still rubbed the next time out.

You just can't load the suspension with a ramp/jack like it will be loaded on the trail.

You're probably better off cutting more than you need. Otherwise you may let the tires do the clearancing for you

Agreed what most people forget to take into account is the weight transfer. When your on a trail as opposed to just lifting one tire up in a flat driveway, the weight of the truck shifts around. I think the term is center of gravity?
Just try to visualize noseing down into a ravine at an angle. The axles will be forced to move differntly because the weight is shifted forward from the downhill angle. In this situation the front axle will be forced to do more of the work(flex) Alternatly as your cresting a large rock and nose up the weight shifts to the rear makeing the rear do more work.

Now the difficult part for me to understand is exactly where and how much wieght is moved as our trucks and blazers are not balanced exactly front to rear. Ill just leave that to smart guys.

Balzer

 

[Hogback Fabrication]

Now the difficult part for me to understand is exactly where and how much wieght is moved as our trucks and blazers are not balanced exactly front to rear. Ill just leave that to smart guys.

Balzer

While analyzing the weight transfer is probably possible, its way easier to just cut out what's in the way

 

[AJMBLAZER]

Hrmmmm...need a ramp or something...wait...I have a barn foundation in my yard...


Have to see how much it compresses. Right now I have a good inch of clearance between the front tires and the back of the front fenders.

So basically all the forklift flex shots we see are...half the story?

 

[Hogback Fabrication]

So basically all the forklift flex shots we see are...half the story?

Pretty much. Depends on how you wheel it.

 

[AJMBLAZER]

Don't wheel it hard or much anymore but don't want that wonderful tearing noise.

That and these tires are getting harder to find.

 

[Bent77]

if you figure up travel to the stop, and where the tire will be in the well, eyeball the tire arc while turning.

Cut off anything w/ in 4"...

 

[dyeager535]

Try jacking up the opposite corner of the truck as far as it will go.

Someone suggested that to me before, haven't had a chance to try it yet. No way you can test compression with one jack on your driveway.

 

[tRustyK5]

Rear is so much easier because there is no steering in the equation and the wheelwells are reasonably generous.

I test by either ramping the truck backwards or using a forklift to pick up a rear tire. Either way will transfer a bunch more weight over the front springs and compress them further.

At some point there is only so far you can trim before you're into truggy territory...and that's where effective bumpstops come in. I installed my Alcan's (6" lift plus 1" BL), have the sheet metal carved back as far as possible...and the 40's still hit the firewall (diff 1.5" forward too)

I got 51" under a rear tire, and still didn't have a tire lifting. Front tire on stuffed side was hard against the firewall, and 4.5" extended bumpstop was missing the target due to the axle 'steering' as the suspension flexxed.

Rene

 

[AJMBLAZER]

Well, I ended up cutting more after doing the '86 K30 imitation of flexing on the barn foundation. The rears were a-okay but the front I ended up taking a lot more out. Looks booty fab right now but I'll fix it soon. Had to get it so I could get down the road to the alignment shop right now.

I sorta trimmed along the bottom of the fender right next to the inner fender liner and then up and in to the edge. Not sure how high but at least 8". It ends just below the little round hole mine has on each fender lip about 8-12" up.

 

[vortec]

The fronts I have concerns about but I've lifted the truck up by the axle so high that the whole truck is off of the stands under the frame. To me this means the suspension is compressed fully...correct?

the weight of the truck alone will not fully compress the supension. if that were the case, hitting a dip, rock or bump would jar the *bleep* out of you. i think of the resting compression (flat surface, truck weight only) as a mid-point (i don't really mean exactly the middle) between full droop and full compression. take all the weight off (tired off ground) and you have full droop. cram the suspension to the bumpstop or limit of shock travel (bumpstock should come first), and that's your realistic max compression. as some guys have mentioned already, you can get full, or near-full compression on one side at a time if you drive up a steep burm or ramp with one side. one way i've seen, but don't recommend, is using chains or straps and a come-along or winch to pull the axle and frame towards each other. that just seemed really dangerous and overly complicated, and didn't really replicate any normal driving condition, even offroad.