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When are rear blocks too big?

M

mark268

NAXJA Forum User
Location
Indiana
Ok, here is the question, is running 3" rear lift bocks too big? I know it will give axle wrap but will it be THAT noticable? I am wanting to stay under 2" if at all possible but I will not know untill I have the new front springs on.
 
mark268 said:
Ok, here is the question, is running 3" rear lift bocks too big? I know it will give axle wrap but will it be THAT noticable? I am wanting to stay under 2" if at all possible but I will not know untill I have the new front springs on.
Click to expand...
ahhh blocks...If your running around town and not trail riding they are fine, other than doing premature damage to your rear springs. If you hit the trail with blocks especially 3" ones and even worse if they are aluminum, expect to be doing a trail repair before long. Yes the axle wrap is bad, yes if they are aluminum they will break, and yes they will cause a spring(on an XJ) to sag a little before its time.
 
I wouldn't go blocks, BUT.... blocks are basically the same thing as perches. same size, same everything (as long as they are steel) so I dont get why it causes negative arching or damage. that said, I have a buddy with 3" blocks and he has -arch now...so ????? Just get full springs- you can add on later.
 
BUT.... blocks are basically the same thing as perches. same size, same everything (as long as they are steel) so I dont get why it causes negative arching or damage.
Click to expand...

blocks increase the distance from the center of the axle (center of rotational force, torque, on the leaf spring) to the leaf spring. Because torque is equal to RFsin(x), the larger the distance(R, radius) the larger the force on the spring which decreases their lifespan
 
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NCSUcherokee said:
blocks increase the distance from the center of the axle (center of rotational force, torque, on the leaf spring) to the leaf spring. Because torque is equal to RFsin(x), the larger the distance(R, radius) the larger the force on the spring which decreases their lifespan
Click to expand...

Plus the more spring wrap, under both acceleration and braking. On a rippley (sp?) surface, the braking can become really scary as the springs alternately wrap up and unload. This can also break leaves.
 
Blocks are no big deal if you install an anti wrap bar. I think the blocks on my dad's dodge are over 3" from the factory. Of course, the springs were designed with this in mind. This just takes me back to put on a wrap bar and everything is hunky dory.
 
OneTonXJ said:
Blocks are no big deal if you install an anti wrap bar. I think the blocks on my dad's dodge are over 3" from the factory. Of course, the springs were designed with this in mind. This just takes me back to put on a wrap bar and everything is hunky dory.
Click to expand...

Wouldn't it just be easier to skip the cost of the blocks and fabricating the wrap bar and just use a set of leafs that give the desired lift height? For the extreme and/or the home fabricator, the wrap bar makes sense. For the person desiring 3" of lift, just sell your stock springs if they are fairly new (there is a market for them), save the $$$ for 3" blocks, and get a set of 3" springs for $300.

Nay
 
I think blocks are fine to, as long as you have the traction bar as mentioned. For leafs we all know that a flatter pack will flex better. That's what just about every XJ ower complains about when it comes to leaves. So if you use a set of blocks, do two things, make them a little longer that your perchers and use the T-bar. Check out my web-site on how I added an 1".

One leathal combination and I can say from direct expierence where blocks are not a good thing. I had OEM leafs, short AAL, Ext shackels and1.5" block. They flex was great and they road great for a couple runs. The I tried a steep incline called Hollywood Hill, total spring wrap! :eek: I was so happy to get up high enough to stop and fix the problem so I could limp home.
 
NCSUcherokee said:
Because torque is equal to RFsin(x), the larger the distance(R, radius) the larger the force on the spring which decreases their lifespan
Click to expand...
Your point is right, but your formula isn't:

Torque equals Force x Distance(radius) x sin(theta)

T=FDsin(theta) not T=FDsin(x)

x is traditionally a variable, eh? :loveu:

Buck.
 
Well, if you guys want to get all technical - sin(theta) = 1 in this scenario. The force will always be at 90 degrees, and the sin of 90 degrees = 1. So just eliminate it altogether. T = F x D. Quit confusing the poor guy. Blocks suck! Just spend the $50 for a add-a-leafs.

That being said, I ran 3" blocks on my Bronco II for quite a while and had pretty much ZERO axlewrap. It flexed twice as much as an XJ in the rear too.

Jared:patriot:
 
you know that is what i meant. show me where the theta key is and i will use that next time...

since when is theta a constant(non-variable) anyway?
 
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