Frame Notch, How Much Backspacing Gained, Info?

GNVYUS 1

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Joined
Dec 15, 2002
Those that did this, can you comment on anything from labor, any issues, gains in tire width etc?

I'm gonna probably do this now that my body work and frame tweaks are done. Thinking of running the MT ET Street R tires at 325/50/15 to handle the crazy torque and new QA1 doubles up front to help transfer.

Thanks
 
I gained just about what was removed from the frame . We basically cut the frames width in half , about on the seam . What we cut out was replaced with 1/4" plate . After the frame is notched , put a straight edge on the flat of the new frame side and massage the inner wheel tub that is where the tire will hit . The wheel tub curves in just above the frame and needs to be " adjusted " .
 

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I gained just about what was removed from the frame . We basically cut the frames width in half , about on the seam . What we cut out was replaced with 1/4" plate . After the frame is notched , put a straight edge on the flat of the new frame side and massage the inner wheel tub that is where the tire will hit . The wheel tub curves in just above the frame and needs to be " adjusted " .
 

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Looks like a 1/2 gain maybe from one picture but hard to tell.

Gnfanatic, are those 325/50/15 SS streets, and on a 10" wide wheel?
 
It was at least 1" or I would not have done it . These are 10" wheels.
 

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Thanks guys

What was your backspacing wheels specs..
4.5" BS?

Can you comment on the traction difference from the prior tire?

Like I'd assume you might've been 275/60/15 so these are hooking way better and it doesn't spin from a roll if you hammer down the throttle?
 
I have a slightly narrowed ford 9" rearend ( 1.5" each side ) so my back spacing would be different from stock .
These tires , MT 275/60-15 , have been on the car since I bought it so no comparison . Getting the car on 4 wheel scales so we could adjust the upper & lower control arms and HR bar plus front coilovers made it so we can get the car to launch pretty good on the street . The 9" also has a taller upper control arm mounting point and adjustable lower control arm mounting points which helps with setting the instant center .
I can still light'em up at a 40mph roll , just got to be careful with the right foot . lol
 
They no longer make the MT Street SS 325/50/15, I just talked to MT tech, only Street R is that size.
 
Nothing wrong with the Street R it's street legal . I run the Street Radial Pro .
 
Radial Pro is definitely not in my cards here in IL, I wanna drive it as often as I can and our nights sometimes are in the 50s and damp. Also that tire has to be a wigglefest on the highway and hated the old school MT Bias Ply Street Rs from the mid-late 2000s etc.

The MT tech said the Street SS have steel belts under the tread and the Street R have nylon which allow the tread to contact the road better. The Rs also don't have as many grooves so they technically have more tread area touching the road but of course they don't do well in the rain at all.

I ordered the frame notch kit from GNS, it'll add another week to my body shop vacation but at this point, the years over, I'll get maybe 5-10 drives in this fall so I'm gonna plan for next Spring.
 
Dynoman has a nice set up! If you are doing some fabrication and notching the frame, it is good to beef up the back end of the frame and control arm area as well. These gbody frames flex alot, anything you can do to mitigate that will help 60' time / improved drivability results.
 
UMI makes a lower relocation control arm bracket and I'll see what else I can do, a local chasis shop, Trick Chasis, offers a frame brace kit, they don't install so my new local chasis shop, Hochman Speed, will need the car. I'll do all this after I'm done this Winter so I can drive there finished with the front arms and notch with 325s.

If all this has to reduce the spinning enough to grab after a good chirp etc.
 
Trick Chassis is AWESOME. My car has a lot of there stuff. Hi quality parts but fabrication is still required to make everything fit nicely.
 
I'll add that too the list thanks, with T Tops I'll need more than just the old school GNX rear seat brace. Hahaha
 
Radial Pro is definitely not in my cards here in IL, I wanna drive it as often as I can and our nights sometimes are in the 50s and damp. Also that tire has to be a wigglefest on the highway and hated the old school MT Bias Ply Street Rs from the mid-late 2000s etc.

The MT tech said the Street SS have steel belts under the tread and the Street R have nylon which allow the tread to contact the road better. The Rs also don't have as many grooves so they technically have more tread area touching the road but of course they don't do well in the rain at all.

I ordered the frame notch kit from GNS, it'll add another week to my body shop vacation but at this point, the years over, I'll get maybe 5-10 drives in this fall so I'm gonna plan for next Spring.
The ss tire sidewall sucks on the street in a high torque situation with 0 prep to the road.
The 2 tires are incomparable.
The r is the tire to run if you have to run a radial on a unpreped road 😉
What most guys dont understand is that radials really need to be on a radial prepped track to work and grab their advantage over other tires.
You would have to oversize greatly on a radial to get it to work along with an ace driver and proper boost control
 
Those that did this, can you comment on anything from labor, any issues, gains in tire width etc?

I'm gonna probably do this now that my body work and frame tweaks are done. Thinking of running the MT ET Street R tires at 325/50/15 to handle the crazy torque and new QA1 doubles up front to help transfer.

Thanks
You need to go taller not wider😉
 
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