So I have been doing a lot of reading on how to setup my chassis (truck is still not even apart yet) and making my plans for how I want to proceed. My only issue I seem to not quite understand exactly how to determine my final ride height. There are lots of opinoins out there on the interwebs but since this is a Ford Truck site I fgured I would ask here... so How do you guys figure the final ride height for your trucks once you start building?

I know a few important things are suspension and tires so my plan is to run 18" rims with something around a 245/45/18 tire and I have a Jag IFS/IRS that I will install. Oh and this is all going on a 53 effie.

Any advice or tips/tricks is greatly apreciated. I hoping to finalize my plans soon so I can start working on the truck this winter into spring.

Thanks

 

Hi find holmseys thread on here he has detailed pics of fitting jag suspension on his 55, will give u good idea what it all involves, find it through www.uk-hotrodding .co.uk, in garage link.

 

Yeah I read his threw more then once. I did not find anything specific on the ride height in his layout.

 

Ride height is a tough thing to describe. But, what it amounts to is you need to mockup your tire and wheel combination, set your body and frame at the height/rake you want, then modify your frame and/or suspension mounting points as required to allow a minimum of 4" of travel. How you arrive at depends alot on the type of suspension you are using.

Below is how I detemined the frame height above the centerline of a MII type front crossmember:
A. Half the diameter of front tires equals the distance from the ground to the centerline of the spindle. (lets say this dimension is 14")
B. Mock up the spindle on the MII crossmember and lay it down with the bottom off crossmember on the floor and mesure the distance from the floor to the centerline of the spindle. (lets say this dimension is 9") The idea here is that the lower arms on a MII suspenion should be level when fully loaded. The springs need to be swapped out until you reach this condition.
C. Subtract B=9" from A=14" and you get 5". This is the distance from the bottom of the crossmember to the floor at ride height.
D. Measure the distance from the bottom of the crossmember to the notch in MII crossmember which will mate with the bottom of the frame. (lets say this is 6")
E. Add C=5" to D=6" and you get 11". This is the distance from the floor to the bottom of frame directly above centerline of MII crossmember.

Below is how I determined the minimum dimension to the bottom of the frame directly above the rear axle:
F. Half the diameter of rear tires equals the distance from the ground to the centerline of the rear axle. (lets say this dimension is 15")
G. Half the diameter of the rear axle equals the distance from the axle centerline to the top of the axle housing. (lets say this is 3" /2 = 1.5")
H. Determine the minimum clearance you want to allow for vertical compression of the frame. This is the dimension between the top of axle housing and the bottom of the bump stop below frame. (lets say 4") Your rear suspension system (leafs, coils, coilovers or bags) need to have the appropriate load capacity to maintain this clearance when fully loaded.
I. Allow for the thickness of the bump stop. (lets say 1.5")
J. Add F=15" + G=1.5" + H=4" +I=1.5" and you get 22". This is the minimum height of the bottom of the frame directly above the rear axle.

Now you need to mock up the frame based or the above dimensions. Front of frame above centerline of MII with bottom at E=11" and rear of frame above centerline of rear axle with bottom at J=22". This is were the frame would end up without any modifications.

At this point I would suggest the cab, bed and front fenders be reattached, if they aren't already, in order to get a look at this "ride height". If it's too high or too low on either the front and/or the rear you will have to make modifications to the frame or MII crossmember (c-notching, z-ing, etc) or suspension attachment points to get the ride height/rake you want.

The toughest part is to figure out what your suspension system will do when fully loaded. It's trail and error unless you are reusing an existing suspension system. In that case you can use it to compare the frame heights above with the existing frame heights. The difference between the two is the dimensional difference between existing and new attachment points of the suspension to get the new "ride height".

Sorry this post is sooooo long, but, I said it was a tough thing to describe!

 

WOW Bruce thanks. That is a really good explanation. Really good stuff.

 

No problem.....just take your time and think it through.....do the math.....and make some dimensioned sketches.

 

Hi there, here's a option that can do with your Jag front. The picture show's the way I installed my front end. The way I aligned the centre was by marking the chassis where the centre of the old leaf spring was, then ripped the old unit out and then using a floor jack under the jag front aligned the centre of the wheel hub to the mark on the chassis. Then you have a starting point where to graft the front end to your chassis. If you look in my gallery you will see a picture of the pickup on how the centre the wheel is. Once I put my shocks in it will drop the height about two more inches.

Cheers
Aussie 53

 

Thank you!

 

Well I am at the point of "final: install of my 9 inch rear axle install. I have measured, adjusted , measured and am now going to install the axle. I had to move both the spring perches and shock mounts to suit the frame which required welding on the axle tubes. Fingers crossed the tubes are straight. I am going to rough assemble 3rd member and axles to see if they go together easily. I don't have a dial gauge but if assembly does not go well I will have to check axle for warpage.

 

F100newb
Before you install the Jag IFS remove the stock plastic spacers and use XJ6 springs. There are lowered springs available from King Springs in Australia. The springs are about the same cost as new replacement springs but the shipping from Australia is a little costly (about $200 for springs and shipping).

My Jag IFS was from a XJ12 and sat two high with engine, trans, and front sheet metal. I took out the factory plastic spacers and added the lower springs. It lowered the front about 3 1/2 to 4 inches.

So, install the Jag IFS and see the outcome. If you are happy your done. If you want it a little lower you can add the lowered springs.

Hope this helps.
Dan

 

I welded on my spring perches and shock mounts when installing my 9 inch diff, with no warping or twisting.
Good luck with your project!