like the subject says...how sensitive is the FD steering/suspension to the crown in the road?

when i first got my car i noticed it had a tendency to pull to the right...the original owner said he never noticed this (this was after i paid him and so i wouldn't think he had any reason to lie since he has the money already). now i know a lot of the roads have crowns for drainage...so i'm thinking maybe i'm just not used to the handling characteristics of the FD. in my regular old honda accord i notice the crown in the road, but i think the alignment compensates for it.

tonight i'm going to try to fine some really flat road to see but just wanted to get a feel from you guys.

thanks.

 

oh, i believe these are my specs

front left right
camber -1.0 -1.0 deg
caster 6.4 6.4 deg
toe -0.00 0.00 inch
total toe -0.00 inch
set back 0.06 deg
SAI 14.6 10.4 deg
included angle 13.6 9.4 deg

rear
camber -0.7 -0.7 deg
toe 0.03 0.03 inch
total toe 0.05 inch
thrust angle 0.00 deg

 

My car pulls both directions based on the road conditions. It pulls pretty hard too. My sig shows what suspension parts I have. I think it pulls so much cause the steering is tight. The tight steering I guess would not only make it responsive to the driver but to the road too. I have to be careful on any backroads or on the interstate where exits merge and the pavement changes. That pulls me good.

 

I used to have that problem. It was a combination of radial pull and bad alignment.

I went to several race shops and did alignment three times. Oh and tried to exchange the tire but they told me nothing was wrong with it (bull-cough!). Each time, the alignment guys blamed the tire place, visa versa and the race shop said it was the crown of the road.

The problem with tire shop alignments is that can vary .5 degree or 1 dree for each tire!
Maybe ok for a SUV but not my baby. I took it to Tri-Point and they aligned to the "exact" numbers have have written down for autocross!

Even better then that is going by Pettit's recomended alignments, since they have a version for 16", 17" & 18" wheels, as well as street and AutoX setups.

 

ur sai and included angle are way off. they should be very close to each other. im not sure of the specs. has ur car been in an accident or anything? has the engine cradle been moved? this normally causes these to be off and can be the reason y u r pulling. ad if u want to compensate for road crwon u give the right side a little more negative camber then normal. no more then a half degree difference for the left side. imo i would make the guys that are doing the alignment align everything, including sai and included angle. thats what ur paying for. so u should get it. other then that it seems fine. good luck and hope this helps.

-Angel-

 

i found this

"SAI is not adjustable on most vehicles. SAI can be affected by loose, worn or damaged suspension parts or by frame damage."

so anybody know if this can be adjusted on our cars?

 

Sai = Japanese martial arts weapon?

Pettit alignment for street 16" wheels
(front) (rear)
toe = 1/16" in toe=0
camber = -1.2 camber= -1.1
caster = +6.0 caster = +6.0
keep rear thrust angle set to zero

 

my car only pulls to a side if he road is steep in one direction other wise it goes straight

 

more info for those interested:

Included angle is the sum of the camber and SAI angles and should be within 1/2 degree from side to side. On a unibody vehicle, the two angles that tell the most about the condition of the suspension are SAI and Included angle. If SAI is off, either the vehicle structure or a suspension mounting part is bent or out of proper specs. If the included angle is off, there is a bent or damaged suspension part. SAI and included angle should be within tolerance before any other alignment adjustments are made.

SAI = Steering Axis Inclination(SAI) angle

 

The angle formed by a line that runs through the upper and lower steering pivots with respect to vertical. On a SLA suspension, the line runs through the upper and lower ball joints. On a MacPherson strut suspension, the line runs through the lower ball joint and upper strut mount or bearing plate. Viewed from the front, SAI is also the inward tilt of the steering axis. Like caster, it provides directional stability. But it also reduces steering effort by reducing the scrub radius. SAI is a built-in nonadjustable angle and is used with camber and the included angle to diagnose bent spindles, struts and mislocated crossmembers.

 

I also have problems with my FD pulling from side to side when the road has rutted tire tracks and a crown down the center of the lane. On a newer paved road that isn't rutted the car drives perfect, let go of the steering wheel and it is like autopilot kicks in, straight as an arrow. On older rutted roads I have to almost fight the car to keep it straight.

My other car is a 240SX with the HICAS steering and I have never had this problem with it. I was thinking that the reason the FD is all over the place is because it has a wider wheelbase and tires then the average car so it doesn't sit in the bottom of the tire ruts in the road, but on the sides. I know that people who own Vipers where I live also complain about their cars pulling from side to side when driving on the old surfaced roads that see a lot of traffic.

But maybe it is something to do with my alignment, but why does it drive straight on smooth roads?

 

It also has a very quick-ratio rack and pinion steering which makes it more sensitive to surface contours.

 

A car that is properly aligned SHOULD "follow" the crown of the road, i.e. pull slightly to the right. The key word is SLIGHTLY.
There was a man in Wichita named Bob Murra who was an alignment/front end GOD. He did work at one time for all the top drag racers of the period. He used to set my cars up, and it was incredible the difference it made.

 

You guys have this all wrong. Are you letting go of the wheel and the car is "drifting" to the right? Or is the wheel being "pulled" out of your hand? Alot of people confuse this.

I work for Mercedes Benz and do all the alignments at our dealership. If your car is pulling there are adjustments that can be made to correct this. "Drifting" is normal and it is possible this can be corrected but it depends on your specific car and road conditions. Usually I adjust the right front caster 1/2* higher then the left. This should cure the problem on a good condition car.

As for the original poster's car. I'm sorry to tell you but your car has been in an accident and was not straightened properly, or maybe your bushings are totally shot, but I'm 95% sure it was an accident. If the alignment shop knew what they were doing they would have told you that. SAI and IA cannot be adjusted per say. Changing camber and caster will affect your SAI and IA readings, but since all your other angles are in specs that isn't your problem.

As for comparing a honda accord or any other car for that matter to your FD alignment and handling, you can't. Its has totally different suspension geometry, is set up for handling, and has alot more adjustment. Most cars don't even have a caster adjustment. Caster is the most important angle when is comes to the vehicle tracking straight down the road. Hope that helps.


Good luck
Justin

 

an update for anybody who's interested or has similiar problem:

went to a couple of body shops to see if they could measure my frame for possible damage. they looked at my specs and said the alignment is actually"really good" and shouldn't be pulling. also told me sai doesn't affect the car's handling. they said it's probably not worth it to check out the frame (about 150-200 bucks, 3 hours work). recommended i switch my tires cause often times tires have a radial pull and that it's probably the crown in the road. so i switched tires and it does seem to be better, don't know, could be placebo effect.

oh, and just to clarify, like 93 R1 said, it's a drift to the right when i let the hands off the steering wheel, not a pull where i have to overcompensate to make it go straight. so my pull is a drift. guess i'm just **** about things...it is a 9 year old car after all....

thanks for all the input.

 

This is some good info here. A pulling of the wheel can also be a weak/damaged sway bar, and/or control arms. I'm currently fixing the fomer problem myself, which is causing my wheel to pull.

 

93 R1 what would you do if the car tended to drift to the left when you let go?

 

my car pulls like crazy when there is ruts from big trucks. i have alot of stiff suspenion work and makes the stearing really tight. when going from a nice smooth road to a road that has ruts it will scare the **** out of you because it will pull the wheel hard. i think its worth it though. my car seems like its on rails at times.

 

Mine was a constant pull noticable at speeds over 30mph. With the lazy left hand on left leg, two finger steering wheel hold it was extremely apparent. With one full hand at 9pm or two hands it was not noticable. If you let go of the steering wheel, the car would exit the freeway or make a right hand turn at the corner. I was told this was a radial pull. I had the tire shop swap tires, or so they said. Since I didn't watch them they could have put the same tire back on or swapped rims after swapping tires. I could not tell you if the rim itself was defective.

I have since done a more accurate alignment, have new rims and tires and no longer have a pull. I can let go of the wheel and only get a slight drift if the road is crowned, otherwise it's strait.

You can also check out the sway bar end links and mounts, since those can easily be bent/tweaked and crushed when you bottom out the front end. There is another thread on this but I pulled up 50 results on the search.

 

If your car is DRIFTING bump the caster up about
.2*-.4* on the right. Or drop it that much on the left.

Radial pulls are alot more common then you may think, even with brand new tires. I've seen alot of problems with Michelin Pilot Sports