Toe in/out impact?
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5,406 Posts
Sorry, I don't have the exact incremental change at the tip of fingers, but you can figure out the general affect by looking at current angle of the steering tie rods. Since the steering rack is behind the king pin if the steering rod droops downward or are level (from chassis to upright) then raising the car will cause more toe-out. If the current angle is slanting upward, then raising the car will cause more toe-in (up the point where the steering arms are level).
Thus it is always recommended to check the bumpsteer after altering the ride height.
Cheers,
Kiyoshi
Thank you. That makes sense. Will check...
I've noticed today that my front tires are rubbing against the wheel wells and I need to raise the front ~1/2 inch for now. Got nice holes in my wheel wells now (top front). The car was corner weighted in the past w/ healthy amount of positive rake... maybe too much. I just don't have the time to visit my mechanic before my next 1-day driving school. Everything will be sorted after that event w/ my mechanic. I want to raise the front before the tires put holes in my headlight housings. The rubbing only occurs at this particular track (NHMS). I have ~5mm of tolerance on the toe from the current setup (at zero). Do you know roughly how much the toe could change w/ ~1/2 inch change in height... roughly?
I'm a real amateur on the topic of adjusting toe. I would think the ride height is changing by more than 1/2 inch almost every second when driving. This leads my ignorant mind to think that the toe wouldn't change much w/ 1/2 inch change in ride height. If it does change a lot, my god, why bother setting a toe... the car would spend rarely any time at the set toe. Again, I really don't know this stuff and am very curious now.
Thank you.
J
I've noticed today that my front tires are rubbing against the wheel wells and I need to raise the front ~1/2 inch for now. Got nice holes in my wheel wells now (top front). The car was corner weighted in the past w/ healthy amount of positive rake... maybe too much. I just don't have the time to visit my mechanic before my next 1-day driving school. Everything will be sorted after that event w/ my mechanic. I want to raise the front before the tires put holes in my headlight housings. The rubbing only occurs at this particular track (NHMS). I have ~5mm of tolerance on the toe from the current setup (at zero). Do you know roughly how much the toe could change w/ ~1/2 inch change in height... roughly?
I'm a real amateur on the topic of adjusting toe. I would think the ride height is changing by more than 1/2 inch almost every second when driving. This leads my ignorant mind to think that the toe wouldn't change much w/ 1/2 inch change in ride height. If it does change a lot, my god, why bother setting a toe... the car would spend rarely any time at the set toe. Again, I really don't know this stuff and am very curious now.
Thank you.
J
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1,175 Posts
Static toe angles affect straight line stability, cornering turn-in characteristics, and tire wear; so it really is pretty important to have them set correctly. Remember the average car spends more time going straight down the road than it does under high lateral g's.
That said, a ride height adjustment can also have a dramatic effect on wheel camber, which, in turn, can affect maximum cornering speeds.
That said, a ride height adjustment can also have a dramatic effect on wheel camber, which, in turn, can affect maximum cornering speeds.
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7,117 Posts
in general terms all the above is correct lowering the car will cause the front to toe out, raising will cause toe in.
front toe in will give more on center feel, more toe out will give crisper turn in. (personal preference more than ultimaly performance)
rear toe will affect handling, how much toe -in you want will depend on your driving style (if you like it a little loose or not)
5mm will not be dramatic, and a little added front toe in will not affect handling much, more feel. i think youre fine.
front toe in will give more on center feel, more toe out will give crisper turn in. (personal preference more than ultimaly performance)
rear toe will affect handling, how much toe -in you want will depend on your driving style (if you like it a little loose or not)
5mm will not be dramatic, and a little added front toe in will not affect handling much, more feel. i think youre fine.
Finally had it raised/realigned today...
Holy cow. Everything was soooo out of whack. Even my caster was, and still is, way off. Long story short, after 5 hours, we called it a day (1/2 of it spent setting the height and corner weighting). I realized just looking at the car and the wheel gap give false perception of a positive rake. What looked like a 10mm+ rake actually turned out to be only ~2mm rake. Can a competent mechanic use strings to accurately measure caster?
Holy cow. Everything was soooo out of whack. Even my caster was, and still is, way off. Long story short, after 5 hours, we called it a day (1/2 of it spent setting the height and corner weighting). I realized just looking at the car and the wheel gap give false perception of a positive rake. What looked like a 10mm+ rake actually turned out to be only ~2mm rake. Can a competent mechanic use strings to accurately measure caster?
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1,966 Posts
You might want to just max it out, then maybe move a washer on one side if it pulls.
When changing the caster, do the coilovers have to come out?
My caster is at 2.70 degrees left and 3.30 degrees right. This is beyond recommended cross caster tolerance. When changing the caster, do the coilovers have to come out? I would hate to have the car aligned all over again! My cross camber is 0.26 degrees in the front and 0.27 degrees in the rear. Is this a big deal. Front and rear toes looked good. The one thing that I've noticed when driving the car on the highway and on the track this week was that the front end just wants to move. A slightest steering input cause the front end to change direction very quickly. My turn-in at the track was sloppy as a result.
The big question is, do the coilovers have to come out when adjusting the caster.
Thank you.
Jay
My caster is at 2.70 degrees left and 3.30 degrees right. This is beyond recommended cross caster tolerance. When changing the caster, do the coilovers have to come out? I would hate to have the car aligned all over again! My cross camber is 0.26 degrees in the front and 0.27 degrees in the rear. Is this a big deal. Front and rear toes looked good. The one thing that I've noticed when driving the car on the highway and on the track this week was that the front end just wants to move. A slightest steering input cause the front end to change direction very quickly. My turn-in at the track was sloppy as a result.
The big question is, do the coilovers have to come out when adjusting the caster.
Thank you.
Jay
fpitas, I found your 7/10/09 post...
According to that diagram and the picture you provided (and my recollection of my car), all the shims/washers are on the front mounting point of the upper control arm (and the rear mounting point is basically "floating" w/ no resistance from washers front or behind). Is this a correct observation on my part? Also, if I want to increase my caster, do I move the shims/washers to the front or rear of the mounting point?
Thanks again.
Jay
According to that diagram and the picture you provided (and my recollection of my car), all the shims/washers are on the front mounting point of the upper control arm (and the rear mounting point is basically "floating" w/ no resistance from washers front or behind). Is this a correct observation on my part? Also, if I want to increase my caster, do I move the shims/washers to the front or rear of the mounting point?
Thanks again.
Jay
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1,966 Posts
Jay,
You need to move the upper arms rearward to increase caster. That means swapping washers from the rear of each bushing to the front. Not sure if it's necessary, but I did remove the coilovers.
As you said, there are larger washers at the front bushing, and much smaller diameter washers used at the rear bushing. It is important that all the washers are used, and the proportion should be the same front and rear; i.e., if there are three washers behind the front bushing, there should be three washers behind the rear bushing etc. There must always be at least one large washer between the front bushing and the frame.
Note that I said all the washers must be used. This is important so that tightening the bolts doesn't pull on and bend the frame, which will break the adhesive in that area. The last washer will require some force to get it in place. That's not too bad with the large washers at the front, but it gets tricky with the small ones at the rear. A handy alignment tool for washers is a pointed bolt. Take any old bolt of the right diameter and grind or file a point. Once the washers are near the right place, push the pointed bolt through to align them.
As I suggested, many people just max out the caster. For street use, if the car "pulls" left or right you can then move a washer on one side to correct that. For example, if the car pulls right, you would decrease caster on the left (driver's side) by moving a washer to the rear of the bushings on the driver's side. Before you move caster washers to correct pull, be sure camber and toe are correct.
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100 Posts
Castor
Castor affects more than the straight line stability. With regard to strings and castor.... a castor gauge is required to measure the castor (or alignment rack). If your car is too "darty" it is possible that you have too much toe-out in the front. Doubtful that castor is responsible for the twitchy turn-in.
Castor has an affect on straigt line stability and the rate of camber change as the wheel is turned. If the geometry is not maladjusted the outside wheel should gain negative camber (become more negative) and the inside wheel should be come more positive in camber. Greater positive castor increases the rate of camber change with steering wheel movement.
Static negative camber affects the tire contact patch and ultimately will limit braking. Positive castor will add more negative camber to the outside front wheel in a turn which will partially compensate for body roll. Body roll adds positive camber to the outside tire in most suspension designs and makes the inside wheel have more "negative" camber.
To increase stability maybe set the rear camber at about -2.5 degrees each wheel with 1/16" toe in each wheel. The front is likely limited to -1.0 to -1.5 degrees negative camber each wheel and total toe OUT of about 1/16".
The camber can be changed but it is a fair amount of work due to the challenges accessing the rear upper A-arm mount. Changing the castor will change the toe quite a bit so it will need re-aligning. Try and keep the steering rack centered when adjusting the toe. If the rack is off center the geometry is altered.
Castor affects more than the straight line stability. With regard to strings and castor.... a castor gauge is required to measure the castor (or alignment rack). If your car is too "darty" it is possible that you have too much toe-out in the front. Doubtful that castor is responsible for the twitchy turn-in.
Castor has an affect on straigt line stability and the rate of camber change as the wheel is turned. If the geometry is not maladjusted the outside wheel should gain negative camber (become more negative) and the inside wheel should be come more positive in camber. Greater positive castor increases the rate of camber change with steering wheel movement.
Static negative camber affects the tire contact patch and ultimately will limit braking. Positive castor will add more negative camber to the outside front wheel in a turn which will partially compensate for body roll. Body roll adds positive camber to the outside tire in most suspension designs and makes the inside wheel have more "negative" camber.
To increase stability maybe set the rear camber at about -2.5 degrees each wheel with 1/16" toe in each wheel. The front is likely limited to -1.0 to -1.5 degrees negative camber each wheel and total toe OUT of about 1/16".
The camber can be changed but it is a fair amount of work due to the challenges accessing the rear upper A-arm mount. Changing the castor will change the toe quite a bit so it will need re-aligning. Try and keep the steering rack centered when adjusting the toe. If the rack is off center the geometry is altered.
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