Caster just out of factory spec after alignment? + a few questions

[mikzsan]

Hi, I just had my Honda Accord aligned and i just want to double check if it is of any concern that there is some slight variations to the factory spec after alignment. I cant really find anyone with suitable knowledge on this on the regular car forums i frequent.

The measurements I'm concerned with are:

At rear:

Setback: initial reading = -8.5mm, final reading = -13.6 mm

Is this acceptable/normal that the magnitude actually increased during the alignment? Is this value also acceptable in general?

At front:

Caster initial left +2.24, initial right +2.58 , final reading left = +1.81, right = +2.62. In the service manual it calls for minimum 2.5 castor (target is +3.5) as well as no greater than 0.45deg difference between both sides, which I am not complying with now.

Is this a concern to go back to the shop?

MY SAI(given as kingpin) angle also wasnt adjusted ...at initial reading, one side was 6deg, the other was 2.85 , and target was 8.58 for both sides, but no final value was given at all. Is this angle even adjustable?


I am greatly appreciative for any insight into this. I can't thank you enough for any guidance.

regards,
Mike

 

[evelrod]

I think you have answered your own questions. You don't necessarily need a genius, just someone with integrity who can read!

In racing it is not uncommon to have variations, done to suit a particular track or driver.
I would not be happy with such variations from spec on my street car.

Did you have this done in the "outback" under a "shade tree"? Find another shop?

Rod

 

[MikeHalloran]

There's no warranty on alignments, but they should be able to get closer than that.

It's time to go back, to a different shop.



Mike Halloran
Pembroke Pines, FL, USA

 

[yoshimitsuspeed]

Most alignments guys/shops don't know and or don't care.
I don't know how serious of an issue those numbers are but the fact is they were unable to set them to specs. Either something is wrong with the suspension like old, or bent parts or they were just too lazy to put them to spec. If there was a mechanical reason they were unable to get it to spec they should have told you. I'm guessing they just didn't want to bother with it any more. I would harass them a little bit if I was you. Preferably try to get a refund or partial refund. You could try to get them to do it again but would you trust them to?
If you decide to have someone else look at it or for the future. Try to find a reputable shop nearby. It might be a bit more expensive but if you find a good shop that racers and tuners speak highly of you will probably have a much better outcome.

 

[Windjammer96]

Today's computerized alignment machines are fairly idiot proof. However, they are also fairly easy to knock out of calibration.

Simple comparative measurements with a tape, will confirm set back and caster differences. ie measure the ball joint center to a common points on both sides of the vehicle. SAI isn't usually adjustable but camber is. A carpenter's level located vertically on the tire side will do for rough comparison; rotating the strut shaft via the big nut, and watching the bubble will decipher a bent strut shaft.

Finally, I'd get an alignment from somewhere else, and compare the results. If they are the same, you have problems, and the alignment tech "should" be able to show you what's wrong. If the second alignment is much more sensible, bring the print out to the previous store and get your money back.

 

[GregLocock]

Half a degree of cross castor would cause a noticeable, if not objectionable, steering pull on a flat road, on a typical roadcar.

A wise man might use cross castor to compensate for the average road crown seen on his roads.

Bear in mind that castor is sometimes measured relative to the ground plane, and sometimes relative to the design plane of the car. Make sure you know which.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[AlexEsteves]

I'd like to discredit both factory alignment specifications and MOST alignment technicians. I have personally seen many techs who don't care or don't understand the effects of their poor alignments. I've also aligned vehicles that pull or dont properly compensate for road crown when they are within factory specs.

Caster by itself is not a tire wearing adjustment so the only effect to consider is whether the car pulls or not. Increased caster only increases the vehicles tendancy to center the steering wheel (straightline stability), so naturally if one side has significantly more than the other it will tend to pull to the side with the lower numerical value. in this case the left. As Greg mentioned most technicians do this to compensate road crown, the amount needed is contingent on the road your on.

SAI is not directly adjustable on any street car.

As far as bent suspenion components are concerned- these will usually show up on other reading than just the caster or SAI. EG: a bent strut on a mcpherson setup will make camber impossible to correct (unless you have aftermarket caster camber plates or some other form of aftermarket camber adjustment).

Alex Esteves, Pasadena CA.

 

[mikzsan]

Wow thank you for all for the insight. I don't notice any pulling sensation in either direction. I had them re check everything (with no charge), and they noticed the toe was a bit off in the rear and readjusted it. The visual camber in the rear does not match what their adjusted specs state. The LHS looks at least -1.00 or more and the other side looks close to 0. However on their spec sheet the LHS reads less negative than RHS.

I won't worry about it anymore after reading these responses, except to say , I won't go back to the same place next time. I will go to a specialist. If they come up with similar numbers, then I know its less likely to be operator/machine error.

Thanks again.

 

[cibachrome]

Caster does quite a bit more than affect leads and pulls. I doubt that many even know that 'caster', besides a 'trail' is also viewed systematically as the partial derivative of camber with steer. The effects on understeer and steering torque and torque gradient are far more significant than what has been mentioned. And, don't confuse the primitve method(s) commonly used by alignment 'specialists' and equipment to check it, with those facilities which can accurately measure the gradient in the operating region where it is most important.