Steering, Suspension, & Brakes

tips, technology, tools and techniques related to non-driveline mechanical components

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roverman
Art Gertz
Winchester, CA.
(2838 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Front Suspension for Jensen Healey
Posted by: roverman
Date: June 30, 2016 02:59PM

I suppose this car shares some vague similarities to Sunbeam Tiger ? 340 Mopar V8 will weigh about 450 lbs. ? Original upper/lower a-arms, need to go. Lower arm uses a strut and no camber adj. Plan is to graft tubular Mustang II , upper/lowers, and "F" body GM spindles, with bolt-on steering arms,(front steer). Geometry is my big question. My C5 Vette LCA/side view, seems to be aimed close/at the CG ? Accentuated roll castor-gain ? How much anti dive ? Likely to use adjustable QA! coilovers. Car will likely have up to 54% weight/front ? RX7-II IRS. Skilled suggestions please ? Thanks, roverman


roverman
Art Gertz
Winchester, CA.
(2838 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Front Suspension for Jensen Healey
Posted by: roverman
Date: July 02, 2016 03:55PM

Anybody ? Not building a race car, but would like geometry to be in "ballpark', and tunable as required. Onward.


Nexxussian
Erik Johnson
Alaska
(61 posts)

Registered:
04/20/2015 10:32PM

Main British Car:
1974, MGB, Citroen Color Rover V8

Re: Front Suspension for Jensen Healey
Posted by: Nexxussian
Date: July 05, 2016 04:42AM

Art, that's quite the hybrid combination you describe. ;)


From what experience I have of building my own race cars and hot rods, my starting points are:

* Ackerman, viewed from above, a line drawn from the outer tie rod through the "king pin" (with ball joints use a line between the upper and lower ball joints to simulate this) should intersect with a similar line from the other side, roughly in the center of the rear axle.

* King pin inclination (use the same "King pin" line mentioned above, but viewed from the front instead of the top) should intersect with the contact patch somewhere near the center of the tire.

* Anti Dive, I try to keep that below 4, I've not encountered a binding issue, but this seems to be one adjustment that is easy to overdo.

* Caster, I tend to start with 4 positive and add more if it seems to need it with, tires under 27" tall.

* Toe, with all new, tight hardware, and front tires narrower than 9" tread width, I prefer slightly toed out.


Some of those may seem psychotic. Like the toe, on the model A, I run 1/32" per side ( 1/16" total ). It preloads the steering gear enough that you don't get an "over center" feeling when you turn after the joints have some wear, and the tires are wearing even. :)

These are only my personal preferences, on what I've worked with, please take them as such as I have never tried the combination you proposed; therefore I can't comment if ANY of that will work for you.

I would tack the mounts in first and measure Ackerman and camber gain, BEFORE installing the springs.

Best of luck.

Care to share how you settled on such an eclectic suspension combination?



Edited 1 time(s). Last edit at 07/05/2016 04:45AM by Nexxussian.


roverman
Art Gertz
Winchester, CA.
(2838 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Front Suspension for Jensen Healey
Posted by: roverman
Date: July 05, 2016 11:29AM

To clarify, no C5 parts on this build. I was only noting how C5 side view of LCA, was aimed upward at rear, not quite to CG ? "F" body GM spindles ? New, forged, workable BJ inclination. Light enough, bolt-on steering arms,(convert to front steer). Direct fit brake kit like Wilwood /etc. Mustang II tubular UCA/LCA's, proven design, value, will fit spindles, and coil-over shocks. Series II RX7 rear diff and suspension clip, proven design and strength,(can upgrade diff to "turbo" if must). I will negate dynamic steering and add aftermarket bushings and adjustability, with simplified mounting to unit body. Many pounds lighter than Jag IRS. Thanks, roverman.


Nexxussian
Erik Johnson
Alaska
(61 posts)

Registered:
04/20/2015 10:32PM

Main British Car:
1974, MGB, Citroen Color Rover V8

Re: Front Suspension for Jensen Healey
Posted by: Nexxussian
Date: July 05, 2016 02:07PM

Make sure you get everything from reputable sources.

I don't know about the spindles, but about 2005 I was shopping for aftermarket M2 suspension bits and there was quite the range of price and quality.

I ultimately went with Fat Man, as I got better customer service from them than others ( if someone's customer service blows before the sale, what's it going to be like after? ).

If you are eliminating the brace rod to the chassis on the LCA I recommend adding a tab to the rear LCA mount so that bolt is in double shear, at the rear mount bushing.

During my research I found quite a number of "copies" (ok, "counterfeit" ) that were built cheaply and had the LCA rip its' mount out of the crossmember, with the cracks starting at the rear of the mount.

That connection takes most of the load in braking, it's why Ford used that brace rod.

I'm not saying a M2 based LCAs can't be successfully made without a brace rod, there are tens of thousands of them in service, it just makes that connection that much more critical.


roverman
Art Gertz
Winchester, CA.
(2838 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Front Suspension for Jensen Healey
Posted by: roverman
Date: July 05, 2016 03:01PM

Erik, your point is well taken. Properly designed gussets and triangulations are well worth the weight and bother, to prevent disaster. This is the reason for choosing stronger spindles. At about 3.5x times the power of oem, and double(?) the G-loads, likely better to slightly overkill on strength. Some of the more complete M2 a-arm kits include the much needed LCA braces. Onward, art.


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