8 replies to this topic

[RazerX]

In replacing shocks I was working on the rear of the car and
pulled the UCA.  I sighted down the holes
in the bushings and noticed they were not perfectly lined.  So I got a dowel that is the same diameter as
the bolts and put in one bushing and sure enough did not go perfectly into the
other.  I would say the bushings were
off, a few degrees from perfect alignment. 
 I then used the dowel to pass through
the subframe holes where the UCA mounts. 
That dowel passes through 3 holes perfectly but won’t go into the fourth
and seems to be off between 1/16 to 1/32.  Hence it seems the bushing has moved a few
degrees to be consistent with the imperfect holes in the subframe.  

 

I know perfect would be best but will this really have any
material impact on the suspension movement and geometry?    Or will
this small bit just be absorbed into the bushing flex.

[RazerX]

I am guess I am asking those who build cars and have successful teams if they would swap the subframe based on this slight imperfection.  Yes i can still make the alignment i want. 

[SaulSpeedwell]

I vote for not worrying about this, and here's why:  The (flimsy, narrow "wishbone") rear UCA is mainly a lateral link keeping the wheel from folding inward/outward (camber).  It is doing almost nothing in terms of controlling toe or resisting brake torque - that is all being carried by the (wide, brick shithouse) LCA.

 

Of course, where there is smoke there can be fire, so make sure you don't have any damage, fatigue, bent/twisted upright, etc.  But if the car aligns straight and you have good symmetrical +/- range from the alignment bolts, I wouldn't worry about a minor misalignment in the UCA pivot axis.

[RazerX]

I vote for not worrying about this, and here's why:  The (flimsy, narrow "wishbone") rear UCA is mainly a lateral link keeping the wheel from folding inward/outward (camber).  It is doing almost nothing in terms of controlling toe or resisting brake torque - that is all being carried by the (wide, brick shithouse) LCA.

 

Of course, where there is smoke there can be fire, so make sure you don't have any damage, fatigue, bent/twisted upright, etc.  But if the car aligns straight and you have good symmetrical +/- range from the alignment bolts, I wouldn't worry about a minor misalignment in the UCA pivot axis.

 

Thanks Saul,  I appreciate the advice.  

 

I suspect a twisted upright for 'weird' camber settings (front camber bolt mark points outward, while rear points inward).  This "weirdness" after replacing the LCA and bolt.  I have checked the rear subframe with the tool and seems fine by all other measurements i have done.  So I will replace the upright and if the weirdness persists, then the subframe.

[SaulSpeedwell]

Thanks Saul,  I appreciate the advice.  

 

I suspect a twisted upright for 'weird' camber settings (front camber bolt mark points outward, while rear points inward).  This "weirdness" after replacing the LCA and bolt.  I have checked the rear subframe with the tool and seems fine by all other measurements i have done.  So I will replace the upright and if the weirdness persists, then the subframe.

 

Yes, high chance of bent upright.  That piece is hard to "see" a bend in, but it is very ductile and bends easily such that the toe (and thus the camber) changes.  If the dents are in front of the rear wheel, you should see toe-out at your camber target, or not enough camber at your toe target.  

 

My experience is the upright bends first, then the LCA bolt, then UCA stuff, then subframes .... and the LCA is the strongest piece back there. 

 

Let us know what you find.

[steveracer]

Really?
So if I bent a hub AND the LCA bolt, it's safe to assume the upright is bent also then?

[SaulSpeedwell]

Really?
So if I bent a hub AND the LCA bolt, it's safe to assume the upright is bent also then?

 

I'd say it is very likely.  On a straight car, the rear alignment bolts are pretty close to "synchronized" (similar clock position) for reasonable toe settings like 0-4 mm toe-in.  If your alignment bolts are whacked - like one is pointed at 10:00 or earlier, and one is pointed at 2:00 or later, then the most likely reason is a twisted upright.

[steveracer]

Hmmmm...

You mean on a particular corner I assume. That makes sense. Per side, mine are pretty close, but from left to right they are, curiously to me, sync'd.

As in both sides are at 5:00, instead of 7:00 on the left and 5:00 on the right. When I've measured the subframe it comes out equal.

 

How much room is there to shift the subframe on it's bolts?

[SaulSpeedwell]

Right, for a given REAR corner, we're comparing the front bolt to the rear bolt.    Put another way, whenever I get a new car (or donor), I set all the bolts to 12:00 in all 8 places, center the rack, set front toe to zero, and start measuring everything.  This will tell you right off the bat what is bent or suspicious, and whether this car is going to be a fight to get enough camber into.  Write it all down, take pictures, and if/when the car gets bent, you'll have something to refer back to.

 

If I can get the car aligned straight with everything from 11:00 to 1:00, I feel good.  If I have some bolts at 2:00-3:00 and some at 9:00-10:00, I know we have a major problem.  If the car is "shorter" on on side by 1/4" or more, I know we have a problem.

 

But, note that the adjuster cams are ecccentric, so they change things fast to either side of 12:00, but they do almost nothing from 2:00 to 3:00 or 9:00 to 10:00.

 

Other adjuster bolt voodoo:

-The "loose" nut-side cam washer (the one not welded to the bolt head) can and will get sloppy on the bolt.  This will make alignments fussier.

-CLEAN the subframe and cams with brake cleaner, etc.  You want this part of the joint to grip.

-GREASE the underside of the NUT, so you can put final torque on the bolt without it "grabbing" the loose cam, which will keep your alignment from changing while you torque down, plus keep the nut-side cam from getting sloppy on the ID after only 1 or 2 alignments.

 

Caveat:  Greasing the nut means you could be more likely to overtorque the nut, so don't go crazy on it. 

 

 

Getting meaningful changes from "bolt slop" is mostly an apocryphal tale, in my experience.