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Front suspension height
Posted by: owlboy ()
Date: August 05, 2020 10:51AM

Hello All,

Building a 1935 Chevy 3 window coupe and, over the outcries of some, want to use a LM Corvair front suspension. I bought the factory shop manual to find the height of the crossmember but, while it goes into detail about setting the suspension settings by weighting the car to get the right fender height or something, I can't find the actual height dimension of the crossmember. I'm obviously missing the logic of this technique. It seems to me there would exist an infinite number of suspension heights with the same ride height for the car. Is this to compensate for spring rate change over time?

What I really need is the distance from the ground to the bottom of the front crossmember from a car with properly adjusted camber and caster so that I might locate the crossmember on my frame at the same height.

I've poked around but can't find this number and any help would be greatly appreciated.



Thanks in advance,

Bob

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Re: Front suspension height
Posted by: MattNall ()
Date: August 05, 2020 11:15AM

Finally you post! Welcome to the CCF!

That measurement is your choice! Adjust it by changing springs to get the ground clearance you desire.

With all wheels on the ground and setting where you want it... Then tighten upper and lower Control arm nuts.

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

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Re: Front suspension height
Posted by: owlboy ()
Date: August 06, 2020 01:03PM

Hi,

Thank you for the quick response. I've been lurking here for a long while and relly didn't want to bother people but I haven't been able to find a solution to my dilemma.

I was thinking in the neighborhood of 6-7" but was afraid I might not be able obtain the proper camber and caster adjustments. That's why I thought I could "work backwards" from a properly adjusted car with the proper spring compression.

I think the weight distribution should end up reasonably close to a car with a trunk full of dead bodies. I know there are some heavier springs available and I am not opposed to having some made once I have an idea of the final weight.

I have one original front suspension and one really nice one I picked up at a swap meet with disc brakes (of unknown spindles) and with chromium plated springs that supposedly came off of a street rod. So's, I will start with that one if you think the 6-7" clearance is reasonable.

I really appreciate your help as I want this to work.... over the outcries of the naysayers who want me to use a Mustang II suspension. I remember the Yenko Stingers at Pikes Peak and a lot of autocross racers so I see no reason this shouldn't work out well. I want to keep my car 100% Chevrolet.

Thanks again,

Bob

p.s. I did own a '66 so I kinda feel like a "Corvair guy" at heart.

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Re: Front suspension height
Posted by: Chris Lampe ()
Date: August 06, 2020 01:17PM

Oh-oh here goes, putting on flame suit now.

I would think the Mustang II would be a better option over the Covair in your particular application. The Corvair is going to require a great deal of additional steering effort over the Mustang II, the Mustang II should have power rack and pinion where as the Corvair has Armstrong steering.

Chris
Rowlett, Tx
NTCA - North Texas Corvair Association
CORSA
'64 Monza 'vert

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Re: Front suspension height
Posted by: RexJohnson ()
Date: August 06, 2020 01:30PM

If you know what the stock distance from the ground to the crossmember is and adjust for tire height differences that you might have you would end up with the full suspension travel. When people start cutting springs you loose upward travel. You would then adjust springs to maintain this ride height. In a Corvair you have to cut the springs to get the stance that you want but when you are building the car you can raise or lower the whole assemble to obtain the stance you want while maintaining proper suspension travel and ride quality.

RJ tools
Salem,Oregon

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Re: Front suspension height
Posted by: owlboy ()
Date: August 06, 2020 02:08PM

Hi Chris,

That is an interesting point.The usual complaint with using the Corvair over the Mustang was that when used with a rack and pinion the turning radius was excessive. This was because most racks didn't typically have enough travel for the Corvair steering arms.I would be using the faster (shorter) length arms.

Also, Flaming River makes longer travel racks and pinion set ups which I was thinking would solve that problem. Additionally, they have power rack and pinion setups if that was an issue. They make front and rear steer systems.

I spoke with Flaming River and they seemed to think it was doable.

I would double check the numbers out on Autocad before I fired up the welder.

The one suspension I have with disc brakes does have a rack from something welded to the front but I suspect it is one of the hack jobs I've heard about.

I was planning on the rack and pinion but will definitely check out the orientation.

Thanks,

Bob

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Re: Front suspension height
Posted by: owlboy ()
Date: August 06, 2020 02:28PM

Hi Rex,

Since I can mount the assembly anywhere in relation to the frame rails (within reason) I was hoping someone might know what a stock crossmember height would be and I would locate mine at the same height. That way's I don't get jammed up on the spring length.

I know their are spring shops that will make just about anything but I think I might run into coil/perch issues which might limit the available spring diameter options.
Additionally, I don't know if spring rates are only a function of coil length (installed height) vs diameter vs coil spacing or if there exists different alloys and heat treatments which would create different spring constants.

I was going to try to mock up the suspension by removing the shocks and spring and replacing the spring with a piece tubing of the same length. Unfortunately, I don't know the spring compression length normally (not under jounce or rebound).

Thanks,

Bob

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Re: Front suspension height
Posted by: thewolfe ()
Date: August 06, 2020 03:45PM

I have succesfully fitted a mustang ii rack to a corvair suspension and it involves more than just quick arms. Unless you like excessive bump steer. The pivot points on the mustang rack are wrong for a corvair so you have two options... move the tie points of the steering arms out by modifying them, moving the tie points out. And also shortened to approximate the length of a quick steer arm. Disc brakes are required because the drum brake backing plates get in the way. Also wheels large enough for the rod ends to ride inside the rim. This is the route I took, with 17" rims. Option 2 is to get a custom rack made with the pivot points in the correct location and use quick steer arms. The flaming river mustang ii manual rack has more travel than all the other ones I looked at - 6.5" compared to 5.5" but not as quick a ratio. I had one of the 5.5" travel racks before switching to the flaming river unit and that shorter travel rack was not enough to get the steering arms all the way to the stops which made for not the best turning radius. Don't have that problem with the FR rack. Either way you go you will also need bump steer adapters and go through the laborious process of setting it up.

One way to lower the car without cutting springs is to install a longer lower ball joint or fit an s10 drop spindle. I don't have experience with the drop spindle but do with the ball joint mod. A chrysler k772 ball joint will lower the front by 1". This requires cutting a hole in the lower control arm, welding in a sleeve, and reaming the spindles to fit the larger shaft. Extended ball joints are also available for even more drop.

Nate Wolfe
Portland OR
65 Corsa 180

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Re: Front suspension height
Posted by: MattNall ()
Date: August 06, 2020 04:42PM

I just checked one of my cars Rear Vair powered One coil cut and at 1" compresion 550 lbs.

Bottom of crossmenber is 4" from floor.

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

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Re: Front suspension height
Posted by: owlboy ()
Date: August 07, 2020 10:10AM

Excellent! That what I needed.

Thanks

Bob

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Re: Front suspension height
Posted by: American Mel ()
Date: August 07, 2020 10:19AM

Owlboy - " I want to keep my car 100% Chevrolet."

I LOVE this statement ! ! !
It drives me nuts to see Morphadited cars at cruise-ins, and car shows.

-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
WA. state, 1 mile south of the Canadian border,
I am not at the end of the world, but you can see it from here.
Have; '66 Monza Coupe - 140, 4-spd. Daily driver beater
'67 Monza Vert. - 140, 4-spd. Daily driver beater
'67 A/C Moredoor Monza
Have had; '61 Monza coupe, 80hp, PG
'62 Monza Wagon, 4spd.
'63 Spyder,
'65 Corsa
.
non-vair
'04 Dodge Cummins Quad Dually, approaching 400K
'03 Honda Del Sol
17'Terry
[corvaircenter.com]

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Re: Front suspension height
Posted by: owlboy ()
Date: August 07, 2020 11:19AM

Hi Nate,

Perfect! This is better than I expected. I was happy just to get the dimension for the crossmember height but what you've done is exactly what I want to do. You've saved me a ton of thinking and research!. When I talked to Flaming River they said if I supplied them with the pivot points they should be able to set me up. Sounds like what you're calling "option 2".

I was concerned about the bump steer issue as well and thinking there might exist a "sweet spot" location for the rack vertically which might minimize the toe in variations. I was going to draw up a series of drawings in Autocad to see how the steering arms vary throughout travel, but I see they make a bump steer guage, reasonably priced, that might be easier. I don't know anything about them but they look like they might short circuit the process.

Your installation looks professional, clean, neat and all around beautiful.

My one suspension already has disc brakes but the guy I bought it from didn't know their origin. I'm hoping to pick some numbers off of them somewhere and figure out what was used.

Thanks again for the good info.

Bob

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Re: Front suspension height
Posted by: thewolfe ()
Date: August 07, 2020 05:39PM

One other thing to note. Moving the tie points out on the steering arms also corrects the ackerman you get with quick steer arms. Without doing that the tires will scrub on tight turns.

Nate Wolfe
Portland OR
65 Corsa 180

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Re: Front suspension height
Posted by: owlboy ()
Date: August 12, 2020 09:31AM

Hi Nate,

Went back and looked at some more posts on the scrubbing problem, going back to 2017. I'm going to have to read up some more on the subject. I also wasn't considering tire width as a variable. It looks like Flaming River and I are going to become close friends by the time this is done.

Bottom line: I think I know I can use this suspension. No one has complained about A-arm strength or the inherent A-arm design as being a problem. It might be easier to go the Mustang II route but that would take the fun out of it and I enjoy working through the design/engineering problems.

For me, it has always been as much or more about the journey than the destination.

I appreciate everyone's input and you guys have got me headed in the right direction. Like everything, there's a lot more going on than at first glance.
Everyone's information flattens the learning curve. I, for one, have always learned from other people's experience and don't feel the need to pee on the electric fence myself!

Thanks,

Bob

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