TJ Suspension Lift Question - Coils????

[CLBJeep]

In the middle of swapping out the RC short arm kit (6" lift) with a long arm kit from TNT customs. I haven't decided yet what springs to get with it. I hear everyone running 3.5" - 4.5" coils, but then they add spacers. Is there an advantage with this setup verses the 5.5" coils? I don't have a body lift or engine lift and would like to keep it that way, but looking for some suggestions from other TJ owners. I'm thinking that once the 5.5" springs settle it should be just about right. I'm worried that the 4.5" coils won't allow much run for up-travel articulation. Also, as part of the lift design they suggest adding the frenched-in rear shock mounts (see picture). Thoughts on this design vs shock hoops? i'm worried about frame strength. Thanks for your input in advance.

Clint

shock mount.JPG (26.94 KiB) Viewed 13214 times

[TSEJEEPERS]

Clint I can not answer your questions about the coils but, I did french my shocks into the frame.
I have not had any problems so far.
When I lengthen my rear wheelbase and installed the fuel cell there was no room underneath to mount the shock as verticle as I wanted.
With stock width axles there was no room to outboard them without cutting into the frame. I would think you will be in the same situation.
There are a number of companys that make a kit to do this, or you could use the Ford mounts for alot less money too.
If you have room in the rear to install a shock hoop by all means do it that way but I would think that you would not have the room.
I would also think with a coil sprung suspention that area would see alot less stress than a leaf spring vehicle.

[Duke Winch]

You didn't state what size tires you are running. This will dictate what direction you should go with springs. 4" lift springs with a 1" body lift will let you run 35" tires. 5.5" springs would probably accomplish the same thing. Remember you want to keep your center of gravity as low as possible.

I wouldn't worry about up travel too much as your shocks will be the limiting factor and shocks should never bottom out at full stuff, use bump stops to prevent this. I'm running 4" springs with a 2" body lift and sheet metal removed and run 38" and probably can fit 39.5" I think, (we'll see in the spring). I have 13" of rear travel and 9.5" on the front and can about drive off the end of a ramp without lifting a tire, which is a function shock travel and good suspension geometry more so than the amount of lift.

There is a whole thread on the project I did that might answer some of your questions. It also has some pictures of the Ford shock mount which is cheep,stupid strong and easy to modify. I frenched it instead of the frame. Here is the link

viewtopic.php?t=1650

Duke

[CLBJeep]

Thanks for the info thus far Tom and Duke. Tire size would be good info . 35" tires is what I run currently. Don't see me going any higher than that till I go full width 60's.

[Fraser]

For what it's worth, I'm using ~4" Rubicon Express coils (I don't recall if I went with the 3.5" or 4.5", but I'm thinking they were the 3.5"). I use a 3/4" spacer up front for leveling purposes, to compensate for the weight of the winch and lack of rear mounted spare wheel/tire. I also have a 1" body lift for added tire clearance without also raising the center of gravity of the frame and all other attached components. I selected front shocks based on maximum travel available with a factory style top stud mount, turned out to be 11.25", (Rancho RS5234, OE for the rear of a 97-04 F150), then I set the bump stops to allow up-travel just shy of max shock compression, which allows about 4" straight vertical up-travel at the center of the coil. At the rear I'm using shocks that still fit the stock location (Rancho RS5241, 8" travel). With bump stops set using the same philosophy as the front, there is about 2.5" straight vertical up-travel at the center of the coil. If you were to move the rear shocks from the inside of the frame (stock location) to the outside of the frame and keep stock axle width and 'standard' offset wheels, the inside of the high tire will rub the shock when the axle articulates, hence the reason for recessing the shock into the frame as suggested by your lift instructions. Realize that 8" of shock travel inboard of the frame is equivalent to somewhat more travel ('x') outside of the frame. You'll have to make the call whether additional travel beyond 'x' is worth the frame mods it will take to accommodate it. I have stock width axles, no spacers, 8.25" wheels with 3.25" backspacing and 37x12.50 tires. The fenders have been trimmed a bit.

Here is a pic with the left front at full straight vertical compression, note there is still some travel available in the shock.

P3200237.JPG (872.81 KiB) Viewed 13179 times

Here is a pic of the right front at full stuff with the left front at full droop, you can see that in a more-or-less stock configuration, the shock will be further compressed with the axle articulated.

P3200231.JPG (888.98 KiB) Viewed 13179 times

Hope this helps somehow. Conclusions up to you...

[CLBJeep]

Thanks for the info Fraser. So your rear shocks still use the bar-pin stock mount like mine, or did you change this? Sounds like the outboard shock setup would be more efficient for full width guys like Tom, Matt & Duke. It's a lot more fab work then I feel qualified to tackle, and bumpstops are easier to deal with for travel limiting. Since I don't have a belly-up skid, I'm going to shoot for the 5.5" coils first and see how I like it. If too unstable I'll go down to the 4.5" coils.

One other question Fraser....Are your upper rear coil mounts still in the stock location, or did you modify them to position the rear coil vertical? This would change the size coil I need in the rear to make everything sit level.

[Fraser]

Correct, I still have the bar pins for rear upper shock mounts. However, I do have limiting straps to keep the stress off of the shock mounts at full extension. And the rear upper coil buckets are still in their factory location. I've considered moving them rearward to make the coil more vertical, but simply haven't, no real compelling reason to do so other than it seems like that's how they should be.

[Fraser]

Clint - pic as requested. I started with a Skyjacker front track bar. It comes with a conical insert to change the tapered factory hole to a straight one. I'm not a big fan of the single shear aspect and the bolt gets loose regularly. If I were doing it again I would cut off the factory bracket and make a new one so the bolt could run horizontally front to rear in a double shear set up. Steve Vohs has his this way, perhaps he could snap a pic of that for you.

[Duke Winch]

Here Ya Go...

Gusset.jpg (2.11 MiB) Viewed 12823 times

[CLBJeep]

Thanks for the pictures guys. looks like I can go either way, but I do like the double shear setup. Guess it all comes down to the same ole question, "how much do I want to spend?"

[Duke Winch]

I made the double sheer bracket out of some scape steel, so cost was more grinding wheels, nut and bolt and rod end than anything else.