If you guys will help me out one more time I promise I won't ask any more questions about my Mustang II front end. I have been playing with the GM pump and Mustang rack combo ( Not MII ) and have made progress in the handling. I would now like to add some caster to help straight line highway driving a bit more. I presently have 4 or 4.5 degrees positive caster. What would anyone recommend for a max caster angle . Keep in mind that 50% of my driving is I-state and of the other 50% hardly any is city driving ....mostly country roads. Thanks, John
What camber settings are you using? I think a 1/16 toe in and 4-4.5 pos caster with 0 camber on the p*** side and a 1/2 degree on the driver side and about 28 psi in the tires to start. remember when the springs settle all will change slightly. pitman thanks for the Link!
I'd think that 4 or 4.5 + caster would be right at the max that you would want. I'm with 34 Toddster in that I like a bit more + camber in the left wheel than the right. Usually 1/4 degree more + in the left wheel depending on the crown of the local roads. You live in an area with a lot of crown or curve on the road surface you usually drive on and you will want up towards the 1/2 degree difference he suggested. More less difference depends on if the car is drifting to the left or drifting to the right. Still, what is the rig doing that you don't like? not tracking? Not returning to center or just a bit darty?
It is very sensitive on the highway. I've realized lately that some of the problem is the ruts worn in the pavement by heavy truck traffic. The car wants to go side to side when the ruts are deep apparently riding up out of the deep center. I've been playing with the Saginaw pump and have made some improvement by reducing the flow to the rack, but I believe I need more caster to improve handling even more. It is presently set for 1/8 toe-in, +1/2 degree camber ,and 4 degrees + caster. I read lots of threads where guys with manual steering are running as much as 6 degrees. I know that more caster makes it steer harder, but I have plenty of power ***ist and I want a heavier road feel on the highway. John
There are not a lot of drawbacks to high caster with power steering, 3-7 seems to be a reasonable range for trial and error testing. I would add that be sure you are close to 1 inch in scrub radius. You definitely don't want a negative radius. With differing KPIs and wheel backspacing this dimenstion is often overlooked. jm2c Hoop
I'd try more restriction to the pump before the caster. What you have caster wise should be more than enough.
Between PS ***ist and Caster I think the OP is trying to increase on-center feel. Caster has 3 primary effects, weight jacking, camber gain, and defines unless the spindle is offset the mechanical trail. Self aligning torque will be a factor of Mechanical Trail, plus Pneumatic Trail modified by the scrub radius. Here is a chart I made for mechanical trail for a couple of tire diameters. And a diagram showing the Torque generated by the trail. Jacking and camber gain are minimal at highway speeds because of very small turn angles. So I believe what we may be doing here is better defined as changing trail, not caster. In karting we used caster primarily for jacking, and used spindle offset to keep trail independent of caster. We wanted trail split for turn in and jacking to unload the rr. Hoop
Thanks Hoop89 it looks like I am going to have to do some homework on that info. I can make most cars drive straight and drive well and can usually tell someone else how to do it but I'm not big on the theory part of it.
+1/2 is quite a lot of positive camber. I use up to +1/4º at a max for cars that have noticeable scrub steer at lower speeds. Going to -1/4º Camber might help you with your on center feel. Running less toe in will also help calm the hypersensitive turn-in and nervous feeling. Drop it down to 0º camber and reset your Caster to +3º with an 1/8" or less toe in to see what that does. Not a big fan of more than 3º positive Caster on these front ends unless you are running a very short tire, like under 24" tall. Also, depending on the design of your front suspension and lower control arm, you may just be experiencing something other than an alignment issue. Take a look at this video with a popular set of "strutless" lower control arm conversions installed.
Generally Mustang II uses 1° positive Caster (not Castor as I have seen it here before), 1/2° positive Camber and 1/8" toe in +- 1/8".
This is how you add caster to the MMII: When tightening the upper a-arms, push the ball joints toward the rear of the car, causing the rear t-bolts to "narrow" in toward the engine & the front t-bolts out away from the engine. Then "narrow" in the FRONT t-bolts only to straighten out the camber.
There are some misconceptions from the folks in that thread - especially concerning tires. Mustang II's came with Firestone 50 Steel Belted radials (a**** others) not Bias Plies as stated over & over. For some comparison, these are the factory Ford specs with power steering 1974 (first year) ~ Caster -1/4 to +1 3/4, preferred +3/4 Camber +1/2 to + 1 1/2, preferred +1/2 Toe 0 to +1/4°, preferred +1/8° 1978 (last year) ~ Caster + 1/8 to + 1 5/8, preferred +7/8 Camber -1/4 to +1 1/4, preferred +1/2 Toe 0 to + 1/4°, preferred +1/8°
Boy, there is a lot of information here ...thanks. I am trying to get a better feel when driving on the interstate. As I said I know that some of the issue has to do with the road itself. But the steering has always been very fast and very light with hardly any road feel. I have a decent size tire on front ....215-70/15 . I have been studying the GM pump and have a very good understanding of how it works. I've made several changes including resizing the venturi orifice size in the flow fitting which has made a significant improvement in the pump match to the rack. I found an excellent explanation of how the Saginaw pump works at different driving conditions. If I can find the site again where I found it I'll post the link. There seems to be some differences of opinion as to how to set up one of these front ends. I will reread and digest all of the information before I realign, but right now I'm thinking about increasing caster to 6 degrees, reducing toe-in to 1/16 inch and possibly reducing camber to 1/4 degrees . Thanks for all the input. John Found it , very good explanation on the Saginaw pump on pages 9-5 and 9-6. http://www.midweststeering.com/pdf/Service/Saginaw 800 PS Comp.pdf
It sounds like you are concerned with "tramlining" or the tendency to follow the ruts in the road. Many people have success with increasing caster so it's worth a try. Stiff low aspect ratio tires generally complicate things but that doesn't seem to be the case here. A cambered tire wants to turn so less camber helps. Toe-out definitely aggravates this tendency. You want about .5 -1 inch of scrub radius. Good luck Hoop
If your running bias ply tires try a set of radials. I had the same problem you state, 2 hands on the wheel running up and down the edges of the trucker ruts on the Interstates.Changed to radials and 1 hand on the wheel smooth as silk down the road. I was the last holdout in our tri- 5 club to change as I could not belive tires could make a difference and thought all along there was something wrong with my 57.
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