Caster alignment question

[The Bloody Panda]

I'm wanting to get my caster dialed in properly and I'd like to run 2.5 degrees positive since I've got a manual steering rack. However, I'm not going to an alignment shop and my angle cube isn't giving me any consistent readings. Does anybody have any idea of approximately how many threads should be exposed on the T3 tension rods to achieve 2.5 degrees positive caster? Thank you very much for all the help.

[gotzoom?]

The only way to accurately do it is with an alignment rack or really accurate (ie: quality digital) protractor. If your strut case is at a 90 degree angle to the road surface, you have zero degrees of caster. You would need to have the road surface perfectly level, then measure the angle of the strut case from that level surface if you don't use an alignment rack.

Considering you can get a full frontend alignment for probably $70-80, I'd just do it right. It's a lot more difficult to set the toe accurately without an alignment rack and that has a big impact on your tire wear.

[The Bloody Panda]

I currently have no money set aside for fancy tools and I'm not comfortable with letting anyone touch the car to do an alignment on it. I've been building it for 8 years and driving it for 4 years but no one has ever driven it except for me. The thought of letting someone else put tools on my precious terrifies the hell out of me. I figure if I just match the length on the tension rods I should be good since the car is totally straight and accident free. Currently I have both tension rods maxed out so that I'm running maximum positive caster. This has been fine but I'm really wanting to lighten up my steering wheel since I recently injured my wrist and don't want to strain it any further. Besides, I think I might actually prefer some factory spec caster for manual steering at this track I'm going to be drifting at because it has a very steep bank that loves to rip the wheel out of my hand when I drop off of it, especially if I'm hitting the brakes at the same time. Of course, maybe there is something else going on there but I'm sure that less positive caster would make turning the steering wheel easier. If I can't get an idea of how many threads to expose I'm going to lengthen each tension rod by 25mm and see if I'm rubbing on the foot well. However, I figure someone on here might have factory caster settings done professionally with T3 tension rods, then I'll just make my thread exposure match there's.

[totta crolla]

You will need to get the front re-aligned once you have changed the caster.

[The Bloody Panda]

I have a good method for doing the toe setting and my camber will not need adjusted.

[totta crolla]

I have a good method for doing the toe setting

A man after my own heart, personally I hate paying someone to do an alignment every time I change something and I too have a method to replicate
a good laser alignment that was done years ago.
By the way there is a reference to the stock caster arm length in the AE86 fsm and if you have a stock arm you should be able to work out the T3 length from
that.
My fsm is in pdf format and I cannot cut n paste from it but basically it shows a measurement from where the inner nut buts up against the retaining washer
to the centre of the first threaded stud on the arm ( measure back from the nut to the first stud you come to)
The stock measurement is : 371.9 mm + / - 0.5mm

[gotzoom?]

The problem with doing it by thread count, measuring between two points, etc is that you assume that the car is perfectly symmetrical. It probably wasn't when it was built and it certainly isn't after 25 or so years of driving. Unfortunately, the caster adjustment on our cars also changes the wheelbase. If you end up with a different wheelbase on each side of the car, that can lead to some strange handling characteristics. Race shops are accustomed to doing race alignments and typically don't charge any more for the job. They just do precision alignments to your spec rather than reading the service manual and doing what it says in there. Since you built it, you can talk to the tech and explain exactly what you want done and show them how you have things set up. I don't like having to get the car aligned after making a suspension change any more than the next guy, but I also don't want the car doing something unexpected when I'm at speed.

[The Bloody Panda]

The car is very predictable and super forgiving at speed. I don't think I'll have any problems if I do it myself. I've been doing it myself anyway for the past 4 years of track driving. I may end up with clearance issues after the first adjustment, which is yet another reason to not take it to a shop because I could end up having to pay them 3 times before I find the perfect balance between what I want and adequate clearance. Hopefully I can get what I want the first alignment though and not run into any clearance issues. My car has aged really well and I know that the camber settings are identical on both sides when I adjust them to the same hash marks on the camber plates. So at least I know that's still super straight. I'm betting the caster alignment will be the same on both sides. Originally I shortened the tension rods to the max and did a precise amount of turns on each side to set the caster. I had no weird driving characteristics being exhibited what so ever. I'm simply going to do it that same way again and will take totta crolla's advice about matching it up with the stock measurement and go from there. Besides, I may not be able to get it as precise as a race shop alignment, but I can certainly do better than Tire Discounters or the like and that's good enough for me. Which is why I never even considered going to a run of the mill tire shop, when my friend got his S13 done he took it to Tire Discounters and they couldn't even simply dial in his camber, caster, and toe like he wanted. Nevertheless, the alignments that they provide at those shops produce a car that handles completely acceptable to me.

[Deuce Cam]

Unfortunately, the caster adjustment on our cars also changes the wheelbase.

Would caster/camber adjustable top hats potentially change that? I know the power steering equipped 86's were equipped high caster top hats from the factory and the manual steer cars were equipped with low caster top hats. From what I understand all the aftermarket camber plates for our cars mimic the geometry of the oem low caster top hats.

I recall reading about someone getting camber plates - that were also caster adjustable - from ground control in the auto x thread on the old site. Was that you?

[The Bloody Panda]

Wasn't me, mine only adjust camber. I have the Tein suspension.

[Cavi Mike]

Caster. Castor is a type of oil.

If you're looking for your car to handle a specific way, you need to adjust it and then go drive it around and see if it suits your driving style. Just because you read somewhere that some guy runs +2.5degrees of caster doesn't mean it's going to make you a better driver.

[The Bloody Panda]

Thank you for the spelling correction, driving advice, and assumption. You are very wise and assumed correctly. I did read somewhere that some guy runs +2.5 degrees of caster and thought that if I ran that same setting all the doors in the world of driving would just fly open for me.

Honestly though, I fractured my wrist a long time ago and it never healed right. I recently re-injured it and have decided to lighten up my steering wheel by running less caster. So, your assumption was close.

[totta crolla]

From my experience with caster it is best set up with fine tuning on the road.
A long drawn out process because there are a few variables but essentially any pulling left or right can be tuned out with small caster adjustments.
To the op:
The biggest change in manual steering weight will be by changing the steering arm length, I guess you are using stock manual rack length arms ?

[The Bloody Panda]

I agree with you about fine tuning it on the road. I lengthened the tension rods last night so now I need to drive and see if I have adequate clearance, wheel return, and no pulling to one side. Fixing any of those issues will be simple, it's just a matter of time.

I am currently using power steering knuckles. I know that they're increasing the weight of the wheel a lot but I figured I'd mess with the caster before doing anything hasty. If the wheel is still too heavy but I have sufficient return to center, good clearance, and no pulling to either side at least I know my caster is optimized. So then I'll have no choice but to lose my decent amount of steering angle and swap to manual knuckles, but I'll at least install some sort of spacer kit on the manual rack to get back a little bit of that lost angle. It would be a shame though to lose my current angle since I consistently use all of it when drifting in 2nd gear.

[gotzoom?]

For drifting, you probably want as much caster as you can get. Ground Control makes camber plates with caster adjustment, as well. They're about the same price as other quality units. I was able to get to zero caster easily (for autocrossing) and 4 degrees easily using the stock tension rods and GC plates. You can probably get more caster than that if you need it, with those camber plates and stock tension rod adjustment.

[Deuce Cam]

^Do you have a link or part number for the gc plates? I couldn't find anything for an ae86 on their website.