Front end alignment

**kool-aide** · 09-04-2008, 02:09 PM

I had my front end aligned today after my control arm bushing install.

The place said the caster on the driver's side was 4.1 or something like that. Since the OEM value is supposed to be 4.3 to what ever i wasn't to concerned by the number, close enough.

My question is why can't the caster be adjusted? I asked the guy at the shop and he said it could be struts or something blah blah.

I said I had new shocks and he kind of just said the number is not something to be alarmed about. I just want to know why there is an alignment value you can't change? I mean what if I was out far enough to cause a problem. If you can't adjust it what are you supposed to do. This is the kind of logic that screams, uh no, some one is full of it, lol...

**kool-aide** · 09-04-2008, 02:32 PM

according to the trusty Haynes manual, lol...

The lower control arms are used to adjust the camber and caster. The whole time I was out there fighting with the lower control arms. I kept asking why are there slots in the cross member. Even on the after market cross members there are slots. Well, I guess if you read the whole book instead of skimming and skipping, lol...

I am now full of dangerous information

**Too Fast** · 09-04-2008, 02:49 PM

I have been doing alignments for over 20 years, our F-bodies camber/caster is adjusted by the slots on the lower cross member, where the lower control arms mount. He is right about the 4.1 being nothing to be concerned about as caster is not a tire wearing angle. It is the angle between the upper and lower pivot points, on our case the upper shock mount and the lower ball joint. Caster gives directional stablity. Most cars are not able to have their caster adjusted, it is a reference angle to check if something in the suspension is bent. As long as caster is within .5 degree from side to side, the car will usually not pull. If it is off more than that, it can pull to the side that is more negative, ie, if it has 4.0 on the left and 5.2 on the right, most cars will pull to the right.

Steering axis inclination is another reference angle to check for bent parts, it is not adjustable.

Camber is the way a tire leans in (negative) or our (positive). Usually negative camber gives better handling, but if you much beyond .5 degree negative usually you will get inside edge tire wear.

Toe is the most important for tire wear, most cars specify almost 0 toe or sometimes slight toe in (for rear wheel drive cars) or some FWD cars specify negative toe (toe out, or if you look at the front tires from the front when they are straight ahead you will see each tire pointing slightly out with the steering wheel centered).

Hope this doesn't confuse things!

**kool-aide** · 09-05-2008, 01:45 PM

cool thanks. Well The last time the shock went in it was not dead center on the two bolts under the brake fluid resevior. It was off by about 1/8 maybe a tad less. It was frustrating, but I just bared down and wrenched away, didn't feel good about, but nothing i could do at the time.

**mrr23** · 10-03-2008, 10:28 AM

Originally Posted by Too Fast

I have been doing alignments for over 20 years, our F-bodies camber/caster is adjusted by the slots on the lower cross member, where the lower control arms mount. He is right about the 4.1 being nothing to be concerned about as caster is not a tire wearing angle. It is the angle between the upper and lower pivot points, on our case the upper shock mount and the lower ball joint. Caster gives directional stablity. Most cars are not able to have their caster adjusted, it is a reference angle to check if something in the suspension is bent.

not entirely correct. caster does wear the tires through corners. it's minor, but it's called camber roll. but not enough to worry about in this case as it's close to factory tolerances. caster allowance is 4.30* - 5.30*

for the 93-02 cars, the pivot point is the upper ball joint to lower ball joint because the spindle is connected to those points. for the 82-92 f-bodies it is the upper strut mount to lower ball joint because the spindle is bolted to the strut and lower ball joint.

Originally Posted by Too Fast

As long as caster is within .5 degree from side to side, the car will usually not pull.

depends on where you live. on the coastlines, the caster will need to be .5* higher on the right to offset the road crown. on flat terrain, like in the middle of the US, then not as much offset is needed. i'm here in florida and most of the ones i have done only needed about .3* higher on the right.

Originally Posted by Too Fast

If it is off more than that, it can pull to the side that is more negative, ie, if it has 4.0 on the left and 5.2 on the right, most cars will pull to the right.

you are correct that it will pull to the side with the lower number. just incorrect in your example. 4.0* left and 5.2* right will go left as the lower number is on the left. and this assumes camber is equal on both sides.

**Too Fast** · 10-04-2008, 01:21 PM

Originally Posted by mrr23

not entirely correct. caster does wear the tires through corners. it's minor, but it's called camber roll. but not enough to worry about in this case as it's close to factory tolerances. caster allowance is 4.30* - 5.30*

for the 93-02 cars, the pivot point is the upper ball joint to lower ball joint because the spindle is connected to those points. for the 82-92 f-bodies it is the upper strut mount to lower ball joint because the spindle is bolted to the strut and lower ball joint.

depends on where you live. on the coastlines, the caster will need to be .5* higher on the right to offset the road crown. on flat terrain, like in the middle of the US, then not as much offset is needed. i'm here in florida and most of the ones i have done only needed about .3* higher on the right.

you are correct that it will pull to the side with the lower number. just incorrect in your example. 4.0* left and 5.2* right will go left as the lower number is on the left. and this assumes camber is equal on both sides.

Picky picky picky. But you are correct. Especially with my brain fart on which way the caster pull is on my own example LOL.

**mrr23** · 10-04-2008, 04:17 PM

yeah i get picky with alignment things. that's all i do is run a business that only does alighment/suspension work. wasn't trying to be mean.

**Too Fast** · 10-05-2008, 05:50 AM

I always wondered why the trucks have a caster difference. I first started noticing this about 10 years ago. Yeah, here in midwest we pretty much have flat roads. I did not think you were mean LOL.

**mrr23** · 10-05-2008, 05:53 AM

i do semis for a living as well as small vehicles. about 60% are semis.

**Too Fast** · 10-05-2008, 04:54 PM

^^^Saw that I got a response this morning from you right away, don't you mods have anything else to do in life, especially on a Sunday morning? LOL LOL LOL!