65 Mini Tubs and frame rail?

65AFX · Oct 9, 2018

Thinking of doing mini tubs on my 65 coronet. I will be cutting the outer lip off of the frame rail and butt the inner wheel well up against it.
a) Do I need to put a lip on the inside of the frame rail for strength?
b) If I don't, what do I weld the floor too?

bearman · Oct 9, 2018

i'm watching and listening

Mike67 · Oct 9, 2018

I'm not familiar with a 65s design, some pics of the wheel tub from inside the trunk and inside the wheelwell might help. But typically they are sectioned, split down the middle, or in my care just to the inside of the seam, the outer tub is moved in towards the rail and a filler (3-4")is welded to join the two halves back together.
Pics are off of my 67 & I still have my back seat.

65hemi · Oct 10, 2018

Mine were split in the middle, moved in, and a filler piece added in. This is the finished look.

gkent · Oct 10, 2018

And nobody has answered your question !!!

I've often wondered that myself - as well as what strength is left in the rail once you remove that lip. When I did mine I didn't go to the rail for that reason. Instead I went about 3/4" from the rail - pretty close to the outer edge of the lip. HOWEVER, some who have removed the lip have done the tub buy cutting the floor close to the lip, now measure over the appropriate amount and make another cut in the floor (usually down the middle of the rail) so that the tub with floor section still attached can be moved inboard. Cut off the lip, butt weld the floor section down the middle of the rail and weld the tub to the side of the rail.

Not sure about your year but on my '69 the frame rails are not parallel so that means the filler section in the tub will have to be put in in sections.

gkent · Oct 10, 2018

You could also go to USCarTool's website - they have a series of photos doing an early b-body.

dvw · Oct 10, 2018

Like stated earlier. The rail bows outward at the top. If you want to trim the flange , cut only the top portion. I left about 3/16" for strength. This will give you about 15.5" to the lip. Want more? Cut the floor above the rail and lay the outer portion of the rail inward until it's flush with the outer lower portion of the rail. My car has almost 600 low 9 second passes. The 1/4 panels are still lazer straight after 6 years of 1.2x 60 ft.
Doug

HEMI-ITIS · Oct 10, 2018

My 63 Plymouth has tubs That are fit to the 1/4 panel with the lips removed from the 1/4.The tub comes down on the inside flush with the chassis rail.With being said,mt street tire is an MT ET Street 16.5 x 31 that does rub a tad on the inside on certain turns and driveway aprons.I normally race with a 10.5W.
I will also add they were done when I bought the car and the rear window regulator was NOT reattached to the tub rendering the rear window in a fixed position,stock glass.

conv67bdere · Oct 10, 2018

Got pictures documenting my mini tub work on my 67 Belvedere confrontations in my build thread . . .

Feel free to check out my work . . Even got the trunk brackets welded back to the tubs

andyf · Oct 10, 2018

65AFX said:
Thinking of doing mini tubs on my 65 coronet. I will be cutting the outer lip off of the frame rail and butt the inner wheel well up against it.
a) Do I need to put a lip on the inside of the frame rail for strength?
b) If I don't, what do I weld the floor too?

Don't cut the outer lip off unless you really need that much room. If you do cut it off then you've dug yourself a deeper hole to get out of. If you are staying with leaf springs then you need to keep the frame rails stiff enough to do their job. If you are switching to coil overs then the frame rails aren't carrying much of a load out past the axle.

HEMI-ITIS · Oct 10, 2018

andyf said:
Don't cut the outer lip off unless you really need that much room. If you do cut it off then you've dug yourself a deeper hole to get out of. If you are staying with leaf springs then you need to keep the frame rails stiff enough to do their job. If you are switching to coil overs then the frame rails aren't carrying much of a load out past the axle.

Do you still feel that to be with a cage in the car?? And thanks for joining us over here!! :thumbsup:

Mike67 · Oct 10, 2018

My rails are tied together w/ a piece of 1 1/2" dom and shock mounts added to cross bar, down bars on cage are welded to the pan directly over the rails

andyf · Oct 10, 2018

It all depends on what else is being done to the car. The OP didn't provide any details so it is impossible to answer his question. If there is a full cage in the car then the rear rails aren't so important. On a high end race car I'd expect the factory rails to be eliminated and replaced with tubing. The OP didn't mention a cage. If there is a cage then you could cut the outer lip off and box in the top of the frame rail. If the top of the frame rail was boxed in with some 10 or 12 gauge plate then the cage could attach to the top of the hump and that would be pretty strong. If it was me I'd add a crossmember at the same point and then hang the shocks from that new crossmember. That gives you a lot of strength and then the trunk floor doesn't have to carry much load at all. But it all depends on what you're trying to accomplish and who is doing the work on the car. Of course, if a pro is doing the work then there is no need to ask questions on the internet.

5.7 hemi · Oct 10, 2018

If you go to the rails, which you should when doing a mini tub, you weld the pan back to the rail, that’ll put back the strength and when you weld the inner tub you’ll weld that to the pan and spot weld the overhang to the rail.

dvw · Oct 10, 2018

Mine is fully tubbed. Obviously not as stiff as the factory wheel well. Still using the factory rails as well. No issues with flex in 6 years that I can detect.
Doug

65AFX · Oct 10, 2018

Thanks to all.
If I decide to do the Mini Tubs I'll fabricate a piece of .083" X .750" wide material and weld it on the inside of the frame rail. This will replace the
outer lip that I'll be removing. My frame rails are straight, no bow at the top.

5.7 hemi · Oct 10, 2018

I wouldn’t bother doing that, the whole purpose of the mini tub is to get rid of that lip.

HEMI-ITIS · Oct 10, 2018

My wheel lip is eliminated as well.

Mike67 · Oct 10, 2018

dvw said:
Mine is fully tubbed. Obviously not as stiff as the factory wheel well. Still using the factory rails as well. No issues with flex in 6 years that I can detect.
Doug
View attachment 665641 View attachment 665656

Jeezx how nice would it be to have such clean wheel tubs???? I'm not looking forward to scrapping all the old rubber out from mine....

dvw · Oct 10, 2018

I haven't removed the rubber from the bottom of the 1/4 panels in 600 passes.
Doug

65 Mini Tubs and frame rail?

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