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40" Tires Requirements

If you come to terms running 37s and no lockers, you’d be just fine with those axles

It’s something to consider. The step to 40 is a massive investment. Doing it for just pavement use doesn’t make sense for most of us
 
Bent77 said:
If you come to terms running 37s and no lockers, you’d be just fine with those axles

It’s something to consider. The step to 40 is a massive investment. Doing it for just pavement use doesn’t make sense for most of us
Click to expand...

So you mean that Suburban axles are not enough to handle the 40" ? and max is 37" ?
And I have to look for 1977–1991 1Ton (K30/V30) front & rear axles only ?? Otherwise I forget to install the 40" safely with the Suburban axles ?


For example this truck here, if I can get the axles from it ?

s-l1600.jpg


s-l1600.jpg
 
SVPAM_SVPAM said:
So you mean that Suburban axles are not enough to handle the 40" ? and max is 37" ?
And I have to look for 1977–1991 1Ton (K30/V30) front & rear axles only ?? Otherwise I forget to install the 40" safely with the Suburban axles ?


For example this truck here, if I can get the axles from it ?

s-l1600.jpg


s-l1600.jpg
Click to expand...
Those are 3/4 ton axles


The previous post, first axle? it’s a light 3/4 ton semi float 14
https://ck5.com/forums/resources/axle-identification-chart.10/

Not trying to be onerous, but why 40s and not something else for street use? If you went 37s on those Burb axles, you could save some cubic cash

Of course if you have cubic cash...
 
Bent77 said:
Those are 3/4 ton axles


The previous post, first axle? it’s a light 3/4 ton semi float 14
https://ck5.com/forums/resources/axle-identification-chart.10/

Not trying to be onerous, but why 40s and not something else for street use? If you went 37s on those Burb axles, you could save some cubic cash

Of course if you have cubic cash...
Click to expand...


Sorry to re type my question

So you mean that Suburban axles are not enough to handle the 40" ? and max is 37" ?
And I have to look for 1977–1991 1Ton (K30/V30) front & rear axles only ?? Otherwise I forget to install the 40" safely with the Suburban axles ?

Kindly confirm
 
I wouldn’t run 40s on the Burb axles, no
 
SVPAM_SVPAM said:
Are you sure about that ? Have you tried it in your truck ?
The I will be fine with 2 or 4" lift kit only and fender trimming

Off course with axles replacement
Click to expand...

A “lift” just reduces how much you need to cut to fit. The question is how much do you feel comfortable cutting? That will determine the minimum lift and other modifications needed to make it work.

40’s can fit on a stock height truck, you just have to cut more
 
Last edited:
To the OP:
If you read back through this thread, you'll find most of the answers you're looking for. You may be wondering why everyone is asking why you want 40s. Yes, big tires look great and yes, you can run them with minimal mods IF you can accept that you are ruining the rig and driving experience. Is it worth 100lb steering, terrible handling and frightening highway speeds so the kid in the passing car says "wow look at that"?

Here's what I'm running and its happy on 37's. I'm confident I could run 40's.

37x12.50 R17 ProComp MTs
6" suspension lift with minor trimming
Dana 60 front/ 14BFF rear. 5.13 gear sets
Highsteer/Crossover steering w/ Hydro assist (braced steering box)
Vortec 8.1L/ 4l85 / NP241c.

This has taken me time and $$$ to get to where I am. I would recommend working your way up in phases.
1) Drive Train -> Power and reliability. If you plan on cruising on the freeway you likely want a big block or modern LS motor. (8.1 was suggested earlier in the thread and I can confirm, good choice)
2) Axles. Don't settle for anything less than a 14BFF/D60 combo
3) Steering. Crossover is just about paramount for 40s. Hydro assist is a plus
4) Lift/Tires.
I put tires/lift last because that stimulus check burning a hole in your pocket is best spent on reliability and durability mods IMO

You'll regret cutting corners. Build it once, build it right.
 
Jon81K5 said:
To the OP:
If you read back through this thread, you'll find most of the answers you're looking for. You may be wondering why everyone is asking why you want 40s. Yes, big tires look great and yes, you can run them with minimal mods IF you can accept that you are ruining the rig and driving experience. Is it worth 100lb steering, terrible handling and frightening highway speeds so the kid in the passing car says "wow look at that"?

Here's what I'm running and its happy on 37's. I'm confident I could run 40's.

37x12.50 R17 ProComp MTs
6" suspension lift with minor trimming
Dana 60 front/ 14BFF rear. 5.13 gear sets
Highsteer/Crossover steering w/ Hydro assist (braced steering box)
Vortec 8.1L/ 4l85 / NP241c.

This has taken me time and $$$ to get to where I am. I would recommend working your way up in phases.
1) Drive Train -> Power and reliability. If you plan on cruising on the freeway you likely want a big block or modern LS motor. (8.1 was suggested earlier in the thread and I can confirm, good choice)
2) Axles. Don't settle for anything less than a 14BFF/D60 combo
3) Steering. Crossover is just about paramount for 40s. Hydro assist is a plus
4) Lift/Tires.
I put tires/lift last because that stimulus check burning a hole in your pocket is best spent on reliability and durability mods IMO

You'll regret cutting corners. Build it once, build it right.
Click to expand...


I understood that I have to go for DANA 60 in the front come from K30 or V30. Any additional truck I can focus on to find it ?

14 bolts rear and I can get it from any 4WD 70's-90 Suburbans correct ?

For steering what do you think about this kit ?
https://skyjacker.com/shop/steering-stabilizer/hydro-7000/7255-steering-stabilizer-dual-kit/

Anything else I need to consider ?
steering reinforcement kit ?

Kindly send me link

Also, what about suspension hangers is it highly recommended ?
 
SVPAM_SVPAM said:
I understood that I have to go for DANA 60 in the front come from K30 or V30. Any additional truck I can focus on to find it ?

14 bolts rear and I can get it from any 4WD 70's-90 Suburbans correct ?

For steering what do you think about this kit ?
https://skyjacker.com/shop/steering-stabilizer/hydro-7000/7255-steering-stabilizer-dual-kit/

Anything else I need to consider ?
steering reinforcement kit ?

Kindly send me link

Also, what about suspension hangers is it highly recommended ?
Click to expand...

A 14 bolt full floating axle again could be had in a K20, K30 or V30. As it's been stated multiple times before, not all are the same and only one from a K20 will bolt into a K5 without modifications. Remember full floaters have the axle hubs stuck through the wheels. SOME K20's came with a Semi-Floating rear axle and will not have the hubs sticking through the wheel. NOT all 4wd Suburbans had 14B full floating axles, many K20 Burbs had the semi-floating 14b axles.

ANY steering stabilizer will not help turn 40's at all. As the name implies it only stabilizes the steering, not assist it at all. 40's are going to require a steering box brace and frame support and hydro assist. If anything putting two of those shocks on the tie rod is going to make it HARDER to turn with 40's up front. The steering reinforcements are well documented here and are as close as your keyboard if you search for it. Try searching "steering box brace" "steering box frame repair"

Suspension hangers? I'm beginning to think you may not totally understand how everything fits together. Ordinarily, most suspension kits are going to reuse all stock suspension mounting points (hangers as you referred to). Now you could lift the rear by using a stock spring, no block and a shackle flip. The shackle flip changes the rear suspension hanger so the shackle hangs down from the hanger instead of being inverted above it. That typically nets 4" of lift with a stock spring. That's another well-documented change that many here have done in the past and it's easy to find in a search when you look for "shackle flip" .

We have no problem helping, but it seems like the advice is falling on deaf ears because the same info has been presented by multiple folks but yet the same questions are coming up. Really going to 40's is no easy task and takes a monumental effort to beef up everything to deal with the added mass and size and still make it safe to drive on or off-road. You really need to go through the build threads of the guys that have already been down this same path and made those exact modifications required to run 40's and not cause the truck to be an unsafe pile to the driver or the rest of the driving public on the roads.

Here's another one. He's got a TON of thought and modifications made in order to run 40's on his Suburban.
Dave's Sub
 
Man you guys all nailed it here. I have spoken to this member through email about his build goals (he reached to me about 10 days ago) and the difference between running 35's and a 4" lift to 40"s is a MASSIVE upgrade.

This is probably the number one question I get on my channel and instagram etc. How to run big tires. Whenever I tell guys they need to budget about $15k minimum to get there they look at me like I am crazy.

Axles (and enough money to get them working properly) steering, drivelines, gearing, frame strengthening, etc etc. It is a substantial investment.

But totally worth it.
 
I think you guys scared him off :haha:

To the OP:

You haven't answered a key question, what is the intended goal of the rig? DD? Primarily off road? Rock bouncer?

If all you want to do is run 40s for shits and grins, then sure - chop up your fenders and slap em on. Don't count on anything lasting...

Will it work? At least temporarily
Will it look cool? Not likely
Will it drive easily? Nope
Will it be fun? If your idea of fun is rebuilding your rig everytime you take it out and having the ride quality of a 1600s horse drawn cart (probably same capability), then sure!

Like others have stated (and based on your posts - you haven't) - READ READ READ, and then READ some more. Take the time, slow down a bit, and research. It's ok to ask questions, we were all new at some point, but try to do what you can to research prior to. Build your rig to suit your purpose.

If you REALLY want to run 40s: cheap, quick, and quality - pick two.
 
I posted a build thread about my blazer. If you want to follow along.

I'm going through the process now of putting one ton axles and 40×17×13.5 tires.

Still have a lot to get through. But best advice is to read the build thread and use the information that is useful to what you're trying to accomplish. There's a wealth of info on this site. Just take your time and plan it the way you want it.

https://ck5.com/forums/builds/project-side-chick.647/
 
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