40's on 392?

[Billkowski]

Not that it matters to a lot of people but wouldn't 40s just obliterate that sub 5 second 0-60? I figured that was one of the primary reasons they bought it.

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[Philip]

Nope. Bigger tires are heavier, harder to spin, and harder to stop. Plus, assuming you have built your jeep to properly support 40’s, you’re probably pushing an additional 1,000+ lbs in additional components to support the added weight and torque a 40” tire will put on your vehicle.

I have two 392’s: one on 40’s w/ 4:88’s and one on 37’s w/ 3:73’s. Now I haven’t drag raced them… but I would expect to see the jeep on 40’s run a 1 to 1.5 second SLOWER 0-60 speed… and a quarter-mile race wouldn’t even be close. I could have gone with 5:38’s, which would improve the 0-60 time… but this would have a negative impact my smiles-per-gallon at highway speeds.

 

[Tank2112]

Nope. Bigger tires are heavier, harder to spin, and harder to stop. Plus, assuming you have built your jeep to properly support 40’s, you’re probably pushing an additional 1,000+ lbs in additional components to support the added weight and torque a 40” tire will put on your vehicle.

I have two 392’s: one on 40’s w/ 4:88’s and one on 37’s w/ 3:73’s. Now I haven’t drag raced them… but I would expect to see the jeep on 40’s run a 1 to 1.5 second SLOWER 0-60 speed… and a quarter-mile race wouldn’t even be close. I could have gone with 5:38’s, which would improve the 0-60 time… but this would have a negative impact my smiles-per-gallon at highway speeds.

Would be interesting to put 37" tires on 392 with 4:88's for 0-60 run.

 

[Philip]

Darn 5-lug vs. 8-lug wheels prevent this from happening ?

But it would be fun!

 

[Moabtj]

Following…working on 40’s on mine currently wither” Toyo RT Trail 4 1/2” MC springs and WFO long Arm

Update 40s have arrived

 

[TRMFAM]

Are you doing any metal / body trimming to clear 40’s?

 

[Philip]

Nope, but I did have the frame notched so I could clear the front shocks.

 

[1996cc]

Looks great. I’m surprised you just didn’t move the lower shock mount out versus notching the frame?
And what’s going on with the drag link here, looks like it’s about to fall out?

 

[ShockerRacing]

Are you doing any metal / body trimming to clear 40’s?

Yes, I had to trim about an inch behind the rear tires, and a little in front of the rear. I only rubbed during faster obstacles and places like the sand dunes.

 

[TRMFAM]

Yes, I had to trim about an inch behind the rear tires, and a little in front of the rear. I only rubbed during faster obstacles and places like the sand dunes.

Thank you! Did you happen to do a video of the trimming process? How you determined the amount to take off, flexing, etc? I know you are pretty good at that!

 

[1996cc]

This is all I trimmed on the front just the passenger side.

This is what I did on the rear-

 

[ShockerRacing]

Thank you! Did you happen to do a video of the trimming process? How you determined the amount to take off, flexing, etc? I know you are pretty good at that!

So Scott Blum gave me some pointers to go off of, but in my case the tires had already left rubber on the metal so I had an idea of what needed to be cut. I’ll share a short so you can see the arc I used for the cut. You can see the red line in the video, and that’s what we followed. On the passenger side I still need to take a little more off. I also used a little seem sealer on the edge when I was done cutting and painted the edge with some Mojito spray paint:



Heres a screenshot showing the line of what I cut off on the front side of the rear tires.

I didn’t have to do any cutting up front other than to remove the crash bar on the passenger side.

 

[Philip]

Looks great. I’m surprised you just didn’t move the lower shock mount out versus notching the frame?
And what’s going on with the drag link here, looks like it’s about to fall out?

This was a 6-figure build I did a bunch of things to clear the 40’s… but only mentioned what was cut away. For the front shocks, I changed my spring rates, added AGM sliders, notched the frame and moved the lower shock mounts. I also needed to replace a few boots and install an HD Antirock in the front… but I tacked those at home.

 

[TRMFAM]

This is all I trimmed on the front just the passenger side. This is what I did on the rear

Thank you, great pics...sharpies rule!

 

[Philip]

Oh, I should also mention that I’m running Cooper Stt Pros, which run a little under 40”. My shocks and bumps are also adjustable so your results may vary

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