UMI Releases New Product: Rear Frame Notch Kit for the 1978-1988 GM G-Body

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Ace Burt

Greasemonkey
Jul 23, 2017
143
43
Texas
Being I have done this from scratch I think this is a great price for a pre-cut kit plus you can save the cost of shipping by ordering from Summit or Jegs.
What size tires and wheels were able to use afterwards? Contemplating doing this myself.
 

565bbchevy

Geezer
Aug 8, 2011
8,447
113
Michigan
What size tires and wheels were able to use afterwards? Contemplating doing this myself.
The largest tire in 15" I have ran was a 295/65 M/T drag radial but they are very tall and I later changed to my current 295/55 M/T's these are on 15 x 9.5 rims with 5.5 backspace, I could go a little wider but I like my tires not to stick out at all.
If you are going with a larger diameter rim you can get by with wider tires because the section width decreases as you increase rim size.
IMG_1470.JPG
 
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UMI Performance

Master Mechanic
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Thread starter
Jul 9, 2011
351
28
Philipsburg, Pa
Hey Guys, getting caught up. Kits are not built to order and are stocked but doesn't mean we could sell more than what we have in stock and need to make a new batch. Also new products sometimes have bugs to work out and we run low quantities in case something isn't right.

For wheel widths, I can't say what would work for you. But on our car we will be running a 18"x11" with a 315 tire. I would assume this is max and will still be snug.
 
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Ace Burt

Greasemonkey
Jul 23, 2017
143
43
Texas
The largest tire in 15" I have ran was a 295/65 M/T drag radial but they are very tall and I later changed to my current 295/55 M/T's these are on 15 x 9.5 rims with 5.5 backspace, I could go a little wider but I like my tires not to stick out at all.
If you are going with a larger diameter rim you can get by with wider tires because the section width decreases as you increase rim size.
View attachment 72661
Thanks, I am going to run either 17 or 18" wheels, I haven't decided yet. Would I run the same back set with a larger wheel diameter? BTW, your car looks sweet!
 

Ace Burt

Greasemonkey
Jul 23, 2017
143
43
Texas
Hey Guys, getting caught up. Kits are not built to order and are stocked but doesn't mean we could sell more than what we have in stock and need to make a new batch. Also new products sometimes have bugs to work out and we run low quantities in case something isn't right.

For wheel widths, I can't say what would work for you. But on our car we will be running a 18"x11" with a 315 tire. I would assume this is max and will still be snug.
Thanks, Is there a standard way to measure for clearance? I have never had a car I needed to alter to run bigger tires and wheels so this is new ground for me.
 

Ace Burt

Greasemonkey
Jul 23, 2017
143
43
Texas
Hey Guys, getting caught up. Kits are not built to order and are stocked but doesn't mean we could sell more than what we have in stock and need to make a new batch. Also new products sometimes have bugs to work out and we run low quantities in case something isn't right.

For wheel widths, I can't say what would work for you. But on our car we will be running a 18"x11" with a 315 tire. I would assume this is max and will still be snug.

I got my notch done using the kit. I put a post on the chassis tech forum with a bunch of pics detailing the process and some stuff we did to make it stronger as well and narrow. I don't want my tires to rub but I want as much tire as I can get under it as well. What I am getting for feedback so far is roughly 5.5 backspacing and I just need to measure for clearance when its all back together. Do you have to cut up the fender wells also?
 

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