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Questions on front susp.

742 views 5 replies 4 participants last post by  OneMoreTime 
#1 ·
I got a Mus. II front susp for my 40 chev coupe. It's used but never was on the road. It was welded to a truck frame and we cut it off. It's 60 inch track width, and my 40 was 57.5. I'm going to use 15x4 front wheels and change the rack to manual. I was considering narrowing the crossmember a couple inches, but then got to wondering if it would be ok with the narrow wheel. Also if I do narrow it, what width rack would I need? Any opinions or thoughts on this would be appreciated. Also I'm going to build my own frame out of 2x3, 1/8 inch wall.
 
#2 ·
Front suspension

You have a very ambitious project on your hands. I just got done with one like it. Over in the build/projects section maybe you can find the thread for my '39 build. I used 2 x 4 with a wall of 3/16". It's a street car, the weight is low and no flex. I used a Welder Series front crossmember. It would be in your interest to visit that site and download the installation instructions so that you can get the ride height, width and anti dive angle correct. Lots of good info there. I also used an '88 T'Bird power rack because it was cheap ($100), compatible with the GM pump pressure wise and a non-sport unit is 3 turns lock to lock.
 

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#3 ·
If you narrow the crossmember you can't just automatically get a narrower steering rack like you'd need to keep the pivots correct and not get bumpsteer, there are only so many racks available. Plus you're getting less room for headers, starter and such...I'd try to avoid doing that. 4" are some pretty thin wheels, it might just work as-is. If you have to narrow something, maybe just take an inch out of the lower a-arms and move the top inner pivots in a bit.

2x3x.120 is probably the most commonly used material for frames but you might consider upping to 2x4, at-least through the main part within the wheelbase on a street vehicle that doesn't have a cage to help support it. 3/16 is some heavy stuff considering most car frames are 12-gauge (.104) stock, but that would be a matter of preference. I helped build a 2x4x3/16ths frame a couple years ago but it was for an LSR car where the guy wanted lots of weight, and down low for c/g. Mocking up the x-member with suspension components tied in position and tires/wheels mounted, and body supported where you'd like will give you a basis to design/dimension a frame around. You've probably noticed there is lots and lots of info and examples around re: frame building, 39 Master's pic above is a good one. All you really need is some imagination and drive and to first be a competent welder, and if you really screw it up just scrap it and start over...material is not that expensive.
 
#4 ·
Car will have a cage, if not I would use 2x4, .125. I've built several drag cars, so I'm familiar with all that's involved. I'm used to doing everything myself, if you can't afford to have it done, learn how to do it yourself was always my motto. Plus I never had a project that wasn't budget. I plan to make several passes down the strip also with this, so it will be built safe. My rear end now is 56.5 total width. I measured the front susp, it is 60in. It has a T bird power rack, I was planning on a Mus II manual rack. The Mus II's had a 55.8 track width. The 40 came from the factory with a 57.5 TW. I don't see why I couldn't use the Mus II or pinto rack and narrow the cross member accordingly. The center is rectangular box tubing, I could make my own jig, use a angle finder on each rotor, and take say 2.5 inches out of the center. I don't see how it would cause bump steer considering they make shorter crossmembers than mine. If I did screw something up, I could just buy another shorter bare CM. Is my thinking wrong here? Sorry so long but I wanted to explain in detail what I'm thinking.
 
#6 ·
I would think it would be possible to narrow the 60 inch crossmember to the 56.5 dimension. Just be careful to get the distance between the lower control are mounting holes dead on the money.. the location of the uppers will depend on that dimension.

I used the 56.5 crossmember on my project and I have some fixing to do to get my alignment correct to sit me..


Sam
 
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