Suspension Question for the Brakes crowd

[GRpufnstuf]

SO, I'm talking about my 1973 620 "Olive"

 

I got Beebani UCAs and '79 620 spindles, hubs, rotor etc, '80 720 lower controll arms (i read they are the same as 620 disc and couldn't find 620 in time.)

 

Got it all on my truck and can't get it aligned while maintaining the ride height (lowered) that I'm looking for.  The upper arms aren't quite long enough so the camber gets funky when the suspension starts moving "up".

 

I have a long background in Aircooled VW tinkering and don't mind some negative camber at the rear.  But in the front it just looks bad and does not suit the style I'm going for.

 

MY QUESTION:

 

Are the 1980 720 Lower arms slightly longer than the 620?  I'm asking here because things got changed for a disc brake upgrade, I don't think the suspension section will have dealt with this directly.

 

remedies I can think of:

 

I can modify the lower arms to move the ball joint inboard (cheapest)

 

Swap for 620 lowers if they are in fact different (cheap)

 

Swap the spindles to D21 drop spindles which will leave my suspension in a non camber position and get me the ride height I want.  But it will cause a wheel size change that I don't want, I like my 14" steelies. (semi expensive)

 

Or finally go back to Kingpin and use an ebay brake swap that will also cause the wheel size change. (EXPENSIVE, especially if i factor in the parts I've invested in for the ball joint/brake swap)

 

thanks!

[heretic]

I was under the impression they are exactly the same... 1978-1982(ish) .... control arms, brake calipers, rotors, spindles... the whole enchilada...  

 

This evening if you like, I can measure my LCA from center of pivot to center of BJ.  

 

 

MY QUESTION:

 

Are the 1980 720 Lower arms slightly longer than the 620?  I'm asking here because things got changed for a disc brake upgrade, I don't think the suspension section will have dealt with this directly.

[GRpufnstuf]

Hey heretic that would be great!  I was under the same impression and it's probably exactly right.

Whenever you can do it is great.  I'm not rushing to fix this but a solid starting point would be great.

 

I'll be dropping a message to Beebani to see if there is a measurement problem on his end or maybe they are built for drop spindles or...

But I'd rather have my ducks in a row so as not to be wasting his time

[heretic]

will do..... the spindles shouldn't be a factor in this issue....my son & I both have dropped spindles & twin piston V6 D21 brakes on our 78' 620's it was a direct bolt on & both trucks have zero issues.

[datzenmike]

Part numbers for the 620 and 720 lower control arms are totally different They look similar but don't show up as being used on both. Maybe get 620 ones.

 

If you do, compare them and let me know.

[GRpufnstuf]

Copy that Mike.  I'll put some feelers out, I haven't seen any 620s in my local Sunland area) pick a parts

[GRpufnstuf]

..... the spindles shouldn't be a factor in this issue....

 

The only real issue is that my truck is riding 1.5" higher than I would like, but with a "correct" alignment.  Lowering it any more, using the torsion adjusters, gives uncorrectable negative camber.  That's why a 2" drop spindle would fix it, I'd probably even have to come up 1/2" to get the height I want and that would improve things even more.

[heretic]

approx 14.5" from center of pivot to center of lower ball joint along the length of the control arm.

[heretic]

got it..... Have you thought about getting a second opinion on the alignment?... I would lower the front to where you want it & then take it in.

 

what size tires are you running (width & ratio) & how low are you wanting it?

 

The only real issue is that my truck is riding 1.5" higher than I would like, but with a "correct" alignment.  Lowering it any more, using the torsion adjusters, gives uncorrectable negative camber.  That's why a 2" drop spindle would fix it, I'd probably even have to come up 1/2" to get the height I want and that would improve things even more.

[]2eDeYe]

FYI Factory camber is -1 deg.

 

I know the mazda guys will slot the upper control arm ball joint holes for camber adjustment. Maybe that is an option?
 

[heretic]

Do you know the stock spec on caster?

 

FYI Factory camber is -1 deg.

 

I know the mazda guys will slot the upper control arm ball joint holes for camber adjustment. Maybe that is an option?
 

[ggzilla]

Factory alignment specs for 1974 620

 

Toe-in: 1-5 mm

Camber: +0°15' to +2°15'

Caster: 1°50' +- 45'

Kingpin inclination: 6° 15'

Steering angle inner wheel: 35° to 37°

Steering angle outer wheel: 30° to 32°

[heretic]

THANKS ggzilla much appreciated

[ggzilla]

Factory camber is about 1 degree positive

[]2eDeYe]

I thought it was 1 deg negative. Will have to check my shop manual it's been a while.

[GRpufnstuf]

Hey I'm back.  So I lowered the front and I'm getting pretty good negative camber at the ride height I want.  I'm currently toed out about 1/4" so I'll remedy that quick like.

 

It looks like I'd start to go positive camber at factory ride height.   When I had the truck on the lift the wheel were hanging they looked either zero or positive.

 

I measured center of pivot to ball joint center and got 14.5" as well.  I'm now looking for a set of the 620 lowers to compare and then modify if they are the same.

 

I don't think I can flip the upper ball?  I thought the bolt holes weren't "square" though I guess I could make new holes there.  I'd rather move the lower inboard.  If the upper comes out any more I'll be into some tire rub on the wheel opening.