Rear Frame Rail Notching How To!

[Alky V6]

A friend talked me into doing a more simple frame notch. I'm only going to thin out the frame section enough to clear the new tires. Try to retain some box to the frame for strength.

What would you consider to be a minimum tire to frame rail clearance?

 

[Dusty Bradford]

A friend talked me into doing a more simple frame notch. I'm only going to thin out the frame section enough to clear the new tires. Try to retain some box to the frame for strength.

What would you consider to be a minimum tire to frame rail clearance?

With a slick 1/4" min because the side wall moves so much, especially when turning.

The pics on the Monte website are cut back as far as mine and it's still not enough to fit a 29.5x10.5 in as far as I like. It fits a 295/65 radial pretty well.

 

[Alky V6]

With a slick 1/4" min because the side wall moves so much, especially when turning.

The pics on the Monte website are cut back as far as mine and it's still not enough to fit a 29.5x10.5 in as far as I like. It fits a 295/65 radial pretty well.

That's the same tire I'm trying to fit. MT 29.5x10.5-15W. I'm using a 10" rim w/a 4" backspace. The tire is just touching the front section of the frame on my car before mod. Are you using a different backspace? Different width rim?

 

[Dusty Bradford]

Yes. I have a 15x11 with 6 inch bs. I want the entire tire under the fender. If you have to raise the back of the car up to fit the tire, your better off with a smaller tire so you can set the car height down.

 

[Alky V6]

Yes. I have a 15x11 with 6 inch bs. I want the entire tire under the fender. If you have to raise the back of the car up to fit the tire, your better off with a smaller tire so you can set the car height down.

The IC I'm going to start out with requires a small drop in the rear from what the car was before. It will put the fender lip close to the tire, but it will not require me to put the tire inside the lip.
I'm also going to try to pull the fender lip out about an inch. Has anyone tried that before? Is it a bear to do?

 

[Dusty Bradford]

Dusty you didnt happen to take any pictures of the car did you?

I do have a pic of it now.

This is 25.2 cert spec.

 

[Alky V6]

Now, that's what I struggled with for awhile. I finally decided that if I were to go through all that trouble and expense, that I would just do a complete tube frame chassis.
I'm in the process of making lower control arms.
http://www.turbobuick.com/forums/fa...ion/283145-hd-lower-control-arms-scratch.html
The 29.5x10.5-15Ws fill the fender opening pretty good and I wanted a way to adjust the rear axle if needed.
I also need to adjust the axle over to the left about 1/4" somehow. Any ideas? I'm thinking of doing it with the spacer bushings of the lower control arms. Does anyone know if that will work?

 

[Dusty Bradford]

Now, that's what I struggled with for awhile. I finally decided that if I were to go through all that trouble and expense, that I would just do a complete tube frame chassis.
I'm in the process of making lower control arms.
http://www.turbobuick.com/forums/fa...ion/283145-hd-lower-control-arms-scratch.html
The 29.5x10.5-15Ws fill the fender opening pretty good and I wanted a way to adjust the rear axle if needed.
I also need to adjust the axle over to the left about 1/4" somehow. Any ideas? I'm thinking of doing it with the spacer bushings of the lower control arms. Does anyone know if that will work?

It's definately to the extreme but has to meet 25.2 spec. The most important bracing to keep the fenders from wrinkling on the G-bodies will need to tie the frame and cage area in front of the lower control arms to the upper mounts and spring perch. You can cut the frame all the way to the back rail and be fine with the right bracing.

I moved my rear over by shortening the upper left arm. I measured the length and then adjusted the the upper right arm to be equal length. I was able to move the lowers to center the tire in the fenderwell and set the wheelbase. This put my pinion angle at -3.5 which was good enough for me. I may have got lucky. You sure don't want the uppers putting the rear in a bind. I then use the ARB to get the car going straight.

 

[Alky V6]

Thanks Dusty. I really appreciate the chassis tuning tips.

 

[Scott Atk]

The most important bracing to keep the fenders from wrinkling on the G-bodies will need to tie the frame and cage area in front of the lower control arms to the upper mounts and spring perch. You can cut the frame all the way to the back rail and be fine with the right bracing.

Dusty, Is this a bolt on version of what you're talking about? It connects the front of the lowers to the front of the uppers.

Hotchkis Sport Suspension 1401 - Hotchkis Sport Suspension Trailing Arm Mount Braces

 

[Alky V6]

I trial fitted the lower control arms with the offset spacer bushings and it did move the axle to the left a bit. Still short a little bit though. I think it's fighting the uppers so I ordered some upper control arm rear spherical mounts so that I could offset those mounting points also.
With the axle centered properly, the edge of the tread will be even with the fender lip on both sides.

 

[Alky V6]

The AFCO shocks and springs came in and they've been fitted.
The shocks are the T2 double adjustable 7 in drag shocks and the springs are 14 in - 125 lbs/in rate. The tires are keeping the car from settling down completely, so I'm not sure yet if I'm going to need spacers for the springs. It's now time to cut the frame.
I'm still waiting for the spherical uca rear mounts. They should be in any day now. I'm going to cut the frame before I determine whether to offset the uca mounts or not.

 

[Alky V6]

The TRZ roll bar has been fitted and the rear axle removed for detailing and painting.
I'm going to weld the roll bar mounting shaft into place and install upper to lower control arm links to tie in the control arm frame mounts before I cut the frame. The roll bar mounting shaft will also be tacked to the spring and shock pads and crossmember. Some simple fabricated brackets will tie the roll bar mounting shaft to the mid section of the crossmember. I'll try to take some pics tomorrow.

 

[Alky V6]

My crowded corner of the shop. It tends to become the catch all for odds and ends in the shop.

 

[Alky V6]

The roll bar mounting set in place.

 

[Alky V6]

The welding is done and a coat of flat black spray paint on the new parts.

 

[Alky V6]

The frame mounting support bars.

 

[Alky V6]

The roll bar installed.
Next is to lay out the cutting guide lines for the frame notching.

 

[Alky V6]

I'm sitting here trying to figure out how I can cut straight lines for the frame notching. I'm definitely not an artist with a plasma cutter.
I think I figured it out. I'm going to fabricate two templates that will fit the contour under the frame rails on each side, connected by three even length rods that will span between the templates. One at the front, middle and rear of the templates. The three rods will be telescoping so that different depths of frame notching can be chosen. The templates will first be set to mark the cut lines. Then the templates will be adjusted in so that the templates can be used as guide plates for the plasma cutter head.
The real trick is going to be designing the templates so that they can be used for the bottom cut and the upper side cut. I can handle the end cuts. Piece of cake.:biggrin:

 

[Adam Connell]

If you want a straight cut, tack weld a straight edge onto the frame to use as a guide. Might take a lil time to set up right, but it will cut way down on grinding time. Hell, if you can get the straight edge to clamp on and not get in your way then that saves even more time!