Power steering rack ratio options ?

[ProfessorB]

Hello y'all. I presently have a Mrk III with power steering. I do NOT know the "ratio" of the rack but the "lock to lock" number seems to be a little less than 2.5 turns. Bottom line is that the steering seems TOO responsive.....just a slight movement of the steering wheel results in 8 inches of "sideways" movement. It's TOO twitchy. I believe I have the 87-93 Mustang power rack. Im thinking there are other Ford power racks (Fairmont? Thunderbird? Whatever?) that may have the same dimensions but have a slower "ratio" ? Any help is GREATLY appreciated. Thanks

[CraigS]

I agree. I am an avid autocrosser so took out my 3.0 turns rack and installed a 2.5 one spring. Loved it at an autocross, but hated it on the street. Kept going w/ it until maybe September. Thought I would eventually get acclimated to it. Tried changes to front toein, and caster but no luck. Finally gave up and took it out to put the 3.0 back in.

[weendoggy]

I run a 2.5ratio, 14" wheel and TypeII pump. Last 25yrs it's been fine, long trips and open track sessions. Personal feel. You need to dial in pressure and flow to get it right. A 2.5ratio with 15" wheel is a different feel. A lot depends on what you want. All Mustangs weren't 2.5 and you can still find rebuilt 3.0 ratio racks.

[Jeff Kleiner]

You sound like you may be a new owner and not the original builder so lets start here: Fox Mustang racks are 20:1, approximately 3.0 turns lock to lock (Used in the 4 cylinder cars) and 15:1, approximately 2.5 lock to lock and what was used in the 5.0 powered cars. There is also a 15:1 ratio which has travel limiters making it 2.25 turns (note that it's still the same ratio, not quicker). Assuming that yours hasn't had travel limiters added to reduce the lock to lock we'll assume that it is one of the 15:1 ratios. As Craig said going to the slower ratio will calm things down but other factors can be at play, primarily alignment. Power steering requires a different alignment than manual. For P.S. we want to see 7 to 8 degrees of positive caster (vs. around 3 for manual steering) along with .5 to.75 degree negative camber. This amount of caster will greatly increase straight line stability and promote self centering. Toe in needs to be 1/16" to 3/32". Very important to assure that it is set for toe in, not toe out. With zero toe in or if toed out the car will be very "darty". Don't forget tire pressure either; no more than 24psi. My own Mk3 with power steering, a 2.5 turn 15:1 rack and these alignment specs is rock solid with 1 hand at 80 MPH. Before changing any components I suggest that you first make sure that it's aligned properly for the configuration. If that still doesn't get you to where you're comfortable then consider a change to the slower ratio rack.

Good luck!

Jeff

[ProfessorB]

You sound like you may be a new owner and not the original builder so lets start here: Fox Mustang racks are 20:1, approximately 3.0 turns lock to lock (Used in the 4 cylinder cars) and 15:1, approximately 2.5 lock to lock and what was used in the 5.0 powered cars. There is also a 15:1 ratio which has travel limiters making it 2.25 turns (note that it's still the same ratio, not quicker). Assuming that yours hasn't had travel limiters added to reduce the lock to lock we'll assume that it is one of the 15:1 ratios. As Craig said going to the slower ratio will calm things down but other factors can be at play, primarily alignment. Power steering requires a different alignment than manual. For P.S. we want to see 7 to 8 degrees of positive caster (vs. around 3 for manual steering) along with .5 to.75 degree negative camber. This amount of caster will greatly increase straight line stability and promote self centering. Toe in needs to be 1/16" to 3/32". Very important to assure that it is set for toe in, not toe out. With zero toe in or if toed out the car will be very "darty". Don't forget tire pressure either; no more than 24psi. My own Mk3 with power steering, a 2.5 turn 15:1 rack and these alignment specs is rock solid with 1 hand at 80 MPH. Before changing any components I suggest that you first make sure that it's aligned properly for the configuration. If that still doesn't get you to where you're comfortable then consider a change to the slower ratio rack.

Good luck!

Jeff
Jeff you are correct. I AM new and did NOT build the car. I really did want to (build one myself). Everything (with the exception of the bodywork) looked like SO much enjoyment and satisfaction. But there's no way I could have built my car for the money that I paid for it. It was an incredible deal.....complete with 427 Windsor. I put this post up looking for advice.....and can recognize good advice when I see it. I AM going to dial in alignment first.
But, to describe my "symptom"..... I was approximately halfway thru a nice sweeping bend at about 50 mph. Not too fast for this bend, but probably 10 mph faster than most normal car drivers would do. The car was slightly over the centerline and so I used the steering wheel to "correct". With only a tad bit of movement I was soon slightly over the side line. I again corrected and was...yup...over the centerline again. So I was going back and forth on steering wheel correction rapidly...probably three or four corrections. The car never did slide or slip or lose traction. Later that day, I went thru that SAME corner in my half ton GMC pickup truck. Same exact speed as I did in the Cobra earlier. Well, it just seemed a whole lot easier ! I even "sawed" on the steering wheel a little bit.... it did not "dart" the way the Cobra did.
Maybe I'm not Ken Miles.....maybe I DO need a slower steering rack. In that case, is the "3 turn lock to lock" my only option? I thought that there, perhaps, might be even more options (maybe from a Fairmont or T-bird) ?

[Mike.Bray]

Jeff you are correct. I AM new and did NOT build the car. I really did want to (build one myself). Everything (with the exception of the bodywork) looked like SO much enjoyment and satisfaction. But there's no way I could have built my car for the money that I paid for it. It was an incredible deal.....complete with 427 Windsor. I put this post up looking for advice.....and can recognize good advice when I see it. I AM going to dial in alignment first.
But, to describe my "symptom"..... I was approximately halfway thru a nice sweeping bend at about 50 mph. Not too fast for this bend, but probably 10 mph faster than most normal car drivers would do. The car was slightly over the centerline and so I used the steering wheel to "correct". With only a tad bit of movement I was soon slightly over the side line. I again corrected and was...yup...over the centerline again. So I was going back and forth on steering wheel correction rapidly...probably three or four corrections. The car never did slide or slip or lose traction. Later that day, I went thru that SAME corner in my half ton GMC pickup truck. Same exact speed as I did in the Cobra earlier. Well, it just seemed a whole lot easier ! I even "sawed" on the steering wheel a little bit.... it did not "dart" the way the Cobra did.
Maybe I'm not Ken Miles.....maybe I DO need a slower steering rack. In that case, is the "3 turn lock to lock" my only option? I thought that there, perhaps, might be even more options (maybe from a Fairmont or T-bird) ?

Seeing how you didn't build the car I would highly recommend starting with the basics like going over it checking nuts & bolts for torque, looking for leaks, etc. For this particular issue, as Jeff said the front end alignment needs to be checked and adjusted if required (use his recommendation for specs). And don't forget the rear end alignment.

Once you know the car is "right" you can evaluate how it drives. Some things to remember when comparing it to your GMC truck.

It's a very short wheelbase car, 92" or something like that. That short of a wheelbase naturally wants to "dart" which to means it's just very responsive.

It only weighs about 2200 lbs so power to weight ratio is hugely different from any OEM car you've driven.

It's got a lot of rubber on the ground and tires with not a lot of flex which increases the responsiveness.

It's stiffly sprung so there's not a lot of roll in the chassis like in your truck.

A 427W has a LOT of power and torque. It will do strange things, like torque steer on you. You can easily end up facing the other way before you know what happened. Don't ask me how I know.

Aggressively getting on the gas during cornering can make things very exciting in a hurry. Especially if you have a traction lock rear end.

Obviously the more you drive it the more comfortable you'll feel. Best advice I ever received was when I had a Cobra years ago. I was told to start out driving like I had an egg between my foot and the gas pedal. Try to be either on the gas or the brake, hard accelerating and then suddenly lifting off the gas can cause it to dart from torque steer. Be very careful about mashing the gas when not going in a straight line. Don't overcorrect.

I think once you know the car is set up correctly and you have confidence in it you'll get comfortable in a short period of time. It's just such a different feel compared to an OEM car.

Mike

[ProfessorB]

Seeing how you didn't build the car I would highly recommend starting with the basics like going over it checking nuts & bolts for torque, looking for leaks, etc. For this particular issue, as Jeff said the front end alignment needs to be checked and adjusted if required (use his recommendation for specs). And don't forget the rear end alignment.

Once you know the car is "right" you can evaluate how it drives. Some things to remember when comparing it to your GMC truck.

It's a very short wheelbase car, 92" or something like that. That short of a wheelbase naturally wants to "dart" which to means it's just very responsive.

It only weighs about 2200 lbs so power to weight ratio is hugely different from any OEM car you've driven.

It's got a lot of rubber on the ground and tires with not a lot of flex which increases the responsiveness.

It's stiffly sprung so there's not a lot of roll in the chassis like in your truck.

A 427W has a LOT of power and torque. It will do strange things, like torque steer on you. You can easily end up facing the other way before you know what happened. Don't ask me how I know.

Aggressively getting on the gas during cornering can make things very exciting in a hurry. Especially if you have a traction lock rear end.

Obviously the more you drive it the more comfortable you'll feel. Best advice I ever received was when I had a Cobra years ago. I was told to start out driving like I had an egg between my foot and the gas pedal. Try to be either on the gas or the brake, hard accelerating and then suddenly lifting off the gas can cause it to dart from torque steer. Be very careful about mashing the gas when not going in a straight line. Don't overcorrect.

I think once you know the car is set up correctly and you have confidence in it you'll get comfortable in a short period of time. It's just such a different feel compared to an OEM car.

Mike

Umm, I think you missed my point. Yes, I didn't build the car. But also, yes I have been under around and thru the car and, with the exception of actually measuring camber, caster and toe-in (plan to do so) I have been over it with a fine tooth comb. Prior to this, I had a Triumph TR6 (even shorter wheel base). And yeah, yeah, yeah I am aware of tire grip differences, power differences, etc. I was not accerelating OR decelerating thu this curve. Neither my GMC nor my Cobra lost any tire traction. But the truck had A LOT SLOWER STEERING RATIO AND IT WAS EASIER FOR ME TO CONTROL. Period. I wanna find a power rack with a less aggressive steering ratio. That is what I want.

[Mike.Bray]

Umm, I think you missed my point. Yes, I didn't build the car. But also, yes I have been under around and thru the car and, with the exception of actually measuring camber, caster and toe-in (plan to do so) I have been over it with a fine tooth comb. Prior to this, I had a Triumph TR6 (even shorter wheel base). And yeah, yeah, yeah I am aware of tire grip differences, power differences, etc. I was not accerelating OR decelerating thu this curve. Neither my GMC nor my Cobra lost any tire traction. But the truck had A LOT SLOWER STEERING RATIO AND IT WAS EASIER FOR ME TO CONTROL. Period. I wanna find a power rack with a less aggressive steering ratio. That is what I want.

Sounds like a 3 turn rack will solve your problem! Sorry I tried to help, I'll go away.

[ProfessorB]

Mike....after re-reading my comment I wish I hadn't made it. I guess I'm pretty cranky today (got some other stuff going on today). Thank you for your help and your patience with me.

[ProfessorB]

Mike....after re-reading my comment I wish I hadn't made it. I owe you an apology. I guess I'm pretty cranky today (got some other stuff going on today) but thats no excuse. . Thank you for your help and your patience with me.

[CraigS]

While I still prefer a 3.0 rack, in the meantime a couple of things may help. 1- drop front tire pressure to 18-20#. This is just an experiment although I always ran mine at 20#. 2- alignment. You want as much + caster as you can get. 7-8deg is common, but if you can get 9 do it. Toein must be IN. Common spec is 1/16 to 3/32 total but 1/8 total may help. As close to zero camber will make a slight change too. 3- What tires are on the car. Typically the higher performance tires will have more grip but also a faster response. Good old 'all-season' like a Nitto 555G2 will have somewhat slower steering response. Also a new full tread depth tire has a slower response than the same tire at 4/32 depth.

[ProfessorB]

All good advice...which I plan to incorporate. I do also plan to change the rack as well as follow all this other advice. I have been to a few autoparts webites and the details can sometimes be lacking. For instance...the actual ratio is often not listed, so in those cases I have been using "lock to lock" for comparison. Using that standard (lock to lock) is "3 turns lock to lock" the most lock-to-lock I will find?

[CraigS]

Yes, 3.0 is the most common. I know ratio could be argued to be more accurate but I can't measure it. I can easily measure L to L turns. Back in the day it used to be recommended to take a small vice grip w/ you when you pick up a rack to check it before paying. These are numbers I had saved from 2011 for Autozone racks.
#6406; 3.0 turns lock to lock
#6439; 2.5 turns lock to lock
#64163 2.25 turns lock to lock
It looks like AZ doesn't sell racks now but maybe the numbers will show up at other websites.

[ProfessorB]

Yes, 3.0 is the most common. I know ratio could be argued to be more accurate but I can't measure it. I can easily measure L to L turns. Back in the day it used to be recommended to take a small vice grip w/ you when you pick up a rack to check it before paying. These are numbers I had saved from 2011 for Autozone racks.
#6406; 3.0 turns lock to lock
#6439; 2.5 turns lock to lock
#64163 2.25 turns lock to lock
It looks like AZ doesn't sell racks now but maybe the numbers will show up at other websites.

Thanks Craig. - Yeah, I found the "lock to lock" number a general way to compare them. Plus, I've seen seen some manufacturers not even list the ratio....but everyone seems to list the "lock to lock" number.
That being said, does anyone know of a lock-to-lock number higher than 3? (Perhaps 3.5)?

[Jeff Kleiner]

Thanks Craig. - Yeah, I found the "lock to lock" number a general way to compare them. Plus, I've seen seen some manufacturers not even list the ratio....but everyone seems to list the "lock to lock" number.
That being said, does anyone know of a lock-to-lock number higher than 3? (Perhaps 3.5)?

Not for power. Seriously, as mentioned earlier make sure your setup is correct (alignment, etc.) before throwing parts at it. There are literally thousands of FFR roadsters out there with power steering that don’t have issues.

Jeff

[ProfessorB]

[QUOTE=Jeff Kleiner;546792]Not for power. Seriously, as mentioned earlier make sure your setup is correct (alignment, etc.) before throwing parts at it. There are literally thousands of FFR roadsters out there with power steering that don’t have issues.

Jeff[/QUOTE
Agreed Jeff. (About a correct set up before "throwing parts at it") But for the sake of curiosity, what is the slowest ratio (in terms of lock-to-lock) of the manual racks?

[CraigS]

I don't remember the L to L of manual but just in case you are thinking of that as an option, I wouldn't. I powered my MkI and was happy w/ it. A few years later I bought my MkII w/ FFR manual rack. Thought it might work out. For me anyway, no way. As I gathered parts to go to PS, I bumped front tires to 30#, set caster and camber to zero. That helped a bit but I was planning my parking spots carefully. Also my concern was, if I ever needed to do an avoidance turn, would I be able to turn quickly enough.

[weendoggy]

As I mentioned, flow and pressure have a lot to do with the 'feel' and you can throw in pulley size too. Much more than just how many L to L the rack has. Good luck finding your sweet spot.

[Jeff Kleiner]

Not for power. Seriously, as mentioned earlier make sure your setup is correct (alignment, etc.) before throwing parts at it. There are literally thousands of FFR roadsters out there with power steering that don’t have issues.

Jeff
Agreed Jeff. (About a correct set up before "throwing parts at it") But for the sake of curiosity, what is the slowest ratio (in terms of lock-to-lock) of the manual racks?

I don't know what the ratio is but I had a Mk4 come in to me for body & paint a few years ago with a really slow manual rack. It must have been 3 1/2-4 turns. I remember that it was honestly just miserable to drive. You felt like you were never going to quit spinning the wheel just to make a turn. While the owner was building the car I tried to convince him to go with power steering but he didn't want any part of it. Know what? After taking the car home and driving it for a few months he converted to power steering. Just sayin'

Jeff

[rich grsc]

Comparing lock to lock, vs ratio, is like comparing how far you can throw a ball, vs how fast you can throw it. Related, but not the same

[ProfessorB]

Comparing lock to lock, vs ratio, is like comparing how far you can throw a ball, vs how fast you can throw it. Related, but not the same

Agreed. Also, another factor to complicate things is the actual "travel". I viewed some racks online and there were a few (small) differences in travel. Most racks listed 6 inches of tavel but a couple were 5.75 inch. So, 3 turns lock-to-lock for 6 inches of travel is a faster ratio than 3 turns for 5.75 inches of travel. I really wish every rack had the listing for ratio so I could compare apples to apples.

[CraigS]

I didn't think there were more than 3-5 racks that would fit an FFR. Are you looking at custom racks?

[Jeff Kleiner]

...is the "3 turn lock to lock" my only option? I thought that there, perhaps, might be even more options (maybe from a Fairmont or T-bird) ?

Fox based Fairmont, Thunderbird and Mustang all use the exact same power rack and are all the same 20:1 ratio for the slower version. Do you understand the what the ratio is? 20:1 means that 20 degrees of steering wheel rotation=1 degree of steering angle at the tire. 15:1 means that it takes 15 degrees of steering wheel rotation to achieve that same 1 degree of steering angle at the tire. As Rich said, and has been pointed out previously---ratio is ratio regardless of steering wheel rotation lock to lock. I can take a 20:1 ratio rack and add or subtract limiters to make it 3.0 turns or 2.0 turns but the ratio remains the same.

Jeff

[Hoooper]

A slower rack sounds miserable. 15:1 is already too slow for such an agile, light car. Seriously, make sure your alignment, tire pressures, etc. are ALL dialed before making any changes you will regret in the future

[rich grsc]

I have no idea why anyone would want a truck (slow) steering on these cars. These are performance cars, learn to drive one, or you will never enjoy it. I love that it seems I just 'think' about lane change and with a small movement I'm changing lanes​.

[Benchwarmer]

Thanks for posting this question. I've been trying to find this info myself. I'm trying to add power steering to my MK3 also. I'm not sure if it's easier to go hydraulic or electric.