PDA

View Full Version : Mustang II for a 53-54 Loewy coupe--which ???



bradnree
12-18-2005, 06:57 PM
Which company have you used for a Mustang II IFS for your 53-54 ?? Which stage did you buy or help install ??...Thanks....BRAD

DEEPNHOCK
12-18-2005, 07:09 PM
Brad...

Fatman Fab makes a kit for a Stude.. But you will LOSE turning radius, ride quality, and the respect of your peers (ask me, I own one)...
Rene Harger at Phantom Auto Works in Knoxville, TN makes a Vette suspension conversion (with Rack & Pinion) that is pretty neat....
But...
For the life of me... I cannot figure out why someone would succumb to the magazine siren song of swapping a Stude suspension. Just add a Jim Turner disc brake conversion and you will have the most accurate (Ackerman) suspension setup that has been manufactured in the last 50 years (and copied by GM,in the F body Camaro and Firebird, as the 'long arm/short arm' suspension....
I am a hot rodder at heart, and own a blasphemous belly button powered Stude... And even I won't promote a Stude suspension swap to a brand X......(Except for Phantom's setup)
Jeff[8D]



quote:Originally posted by bradnree

Which company have you used for a Mustang II IFS for your 53-54 ?? Which stage did you buy or help install ??...Thanks....BRAD


DEEPNHOCK at Cox.net
'37 Coupe Express
'37 Coupe Express Trailer
'61 Hawk
http://community.webshots.com/photo/42559113/426827941Lsvfrz
http://community.webshots.com/user/deepnhock

N8N
12-18-2005, 07:50 PM
Well... I can kinda understand the desire to swap. The Stude suspension, I'm told, needs to have the pivots lowered on the upper control arms for ideal geometry, and there's no built-in anti-dive. Certainly when cornering, the inside wheel will have some, um, interesting camber. You could get the same effect as lowering the pivots by cutting the springs which would look cool, but then you would have fender interference problems (and not everyone likes that "in the weeds" look, even though I do.)

That said, any front end swap or subframe - mustang II or other - will probably be wider than the stock Stude, exacerbating any fender clearance issues or causing you even more work to narrow it.

The stock setup really isn't *that* bad, and truth be told, if you upgrade the suspension too much and try to take advantage of it too often you will probably start some serious frame/body flexing.

Now if you really want the best of both worlds (vintage style and modern chassis) Art Morrison is making a complete frame for a Stude C-K body... but it ain't cheap...

nate

--
55 Commander Starlight
62 Daytona hardtop
http://home.comcast.net/~njnagel

Mike Van Veghten
12-18-2005, 08:06 PM
Stock Stude front end.
Upper arm attachment point lowered....yea.
Little Anti-dive....yea.
No (VERY LITTLE) camber adjustment....yea.
All one gets by cutting spring coils is a lower front end.
Stronger thAn ball joint pivots....yea.

As to the Pinto (Mustang!) stuff, while not my cup-o-tea...do as "you" please, it's "your" car, "you" have to be happy with it....no one else.

I did my own C4 Corvette front end. The Ackerman is only a coupla inches off, much better than many "conversions". I have light weight components, I have designed in pretty good overall geometry, good camber, caster adjustments, a modified non-power Mustang rack & pinion.

Again...it's your car...do as you please.

bradnree
12-18-2005, 08:35 PM
thank you for all of the tips on the front end. Also, I just found steeltechsolutions.com on ebay selling disc brake kits for Studes. They have interesting pages on rear axle ID with drawings for many brands. I would like to have power steering too...thanks...BRAD

DEEPNHOCK
12-18-2005, 08:52 PM
b]Turner Disk Brakes ( http://www.turnerbrake.com/ )..........
are far superior....in this person's opinion.
He can deliver quality product in a timely manner.
Jim Turner is a class act, and his setup is top notch and worth every friggin' penny you will spend.
Ask me... I own both setups.
Jeff[8D][/b]

quote:Originally posted by bradnree

thank you for all of the tips on the front end. Also, I just found steeltechsolutions.com on ebay selling disc brake kits for Studes. They have interesting pages on rear axle ID with drawings for many brands. I would like to have power steering too...thanks...BRAD


DEEPNHOCK at Cox.net
'37 Coupe Express
'37 Coupe Express Trailer
'61 Hawk
http://community.webshots.com/photo/42559113/426827941Lsvfrz
http://community.webshots.com/user/deepnhock

DEEPNHOCK
12-18-2005, 09:07 PM
You want to spend $15k+ for a frame with a Mustang II suspension???
That's what Morrison's setup is.
He has a great business and his mandrel bent rectangular tubing stuff is great, but only one in a thousand here will ever write the check.
The stock Stude suspension geometry numbers are great, You just can't slide the upper inners around like a ball joint setup.
Now... The smart cookie will replace the lower studs in the crossmember with a quarter inch+ thick steel plate and longer studs that will accept a spacer plate between the lower a-arm mounts and the crossmember mount (new/lower) plate. This will, in effect use the coil spring as the fulcrum point and lower the front suspension without cutting the spring. (Lower the inner mount will raise the lower trunion...thus lowering the ride height) Think this is a new idea? They used to do this on 1950 Ford's all the time.
Bump steer? Stude had it figured out....
Ackerman? Stude had that figured out too....
The 'Vette setup is a marginal compromise in both those areas..
Just pulling splinters out from bench racin'...
Jeff[8D]




quote:Originally posted by N8N

Well... I can kinda understand the desire to swap. The Stude suspension, I'm told, needs to have the pivots lowered on the upper control arms for ideal geometry, and there's no built-in anti-dive. Certainly when cornering, the inside wheel will have some, um, interesting camber. You could get the same effect as lowering the pivots by cutting the springs which would look cool, but then you would have fender interference problems (and not everyone likes that "in the weeds" look, even though I do.)

That said, any front end swap or subframe - mustang II or other - will probably be wider than the stock Stude, exacerbating any fender clearance issues or causing you even more work to narrow it.

The stock setup really isn't *that* bad, and truth be told, if you upgrade the suspension too much and try to take advantage of it too often you will probably start some serious frame/body flexing.

Now if you really want the best of both worlds (vintage style and modern chassis) Art Morrison is making a complete frame for a Stude C-K body... but it ain't cheap...

nate

--
55 Commander Starlight
62 Daytona hardtop
http://home.comcast.net/~njnagel


DEEPNHOCK at Cox.net
'37 Coupe Express
'37 Coupe Express Trailer
'61 Hawk
http://community.webshots.com/photo/42559113/426827941Lsvfrz
http://community.webshots.com/user/deepnhock

BeeJay
12-19-2005, 08:26 AM
I'm using a Scott's Rod Shop front end. They will custom make them for what you need. Uses Must II spindles and rack. Tube "A" frames and coil-overs. Working fine for me. Have built two with this set-up. Drive well even on MI roads. Drives really well on the roads in other ststes I have been in.
Bob

Own '53 Commander Starliner. Red w/beige top. 350 Chev/700R4. Tilt,cruise,A/C.

Kdancy
12-19-2005, 05:02 PM
These guys were mentioned in the other thread. Sound like they would be worth checking out--- http://www.unisteer.com/home.php

53commander HDTP
53 Champion HDTP
61 Cursed Purple Hawk
64 Champ long bed V8
64 GT

Mike Van Veghten
12-19-2005, 06:23 PM
Jeff,

Stude Ackerman, no idea, never layed it out.
Stude bumpsteer....Stude missed, at least on my 2 (59 & 60) Lark wagons. I layed it out without a spring on my virgin 60 2dr wagon before I cut it up!! While not as bad as the Chevy II/early Mustang, it's not nearly as good as it could have been.

I spent a lot of time designing, laying out the details for my C4 Vette goodies, cutting out sheet steel, positioning and welding the bracketry/steering to achieve a near zero bumpsteer, the correct chamber change in corners, an amount of anti-dive that was a guess per a "roundy round" (computer) chassis program I borrowed, the ride height where I want it and as I mentioned, the Ackerman is about 2" too long.....not enough to hurt anything. Espically concidering the NASCAR guys run it so long it almost doesn't exist!
Believe me, no more comprimise here than any other "properly" designed and setup front suspension.

And If I may add, in "my" humble opinion....better thAn most.
See...the occasional Autocross is in the future for this particular wagon.

Take a close look at MOST chassis builders full chassis........they F-up big time..including Morrison (where I bought about half of my parts).
They have NO anti-dive, they have NOT done the correct geometry for correct chamber in corners (lean angles), bump steer....what's that.

When I asked the guy that helped me why...."most people won't spend the money for the correct setup. Each different wheel base, ride hieght, requires different geometry, that costs money".

He was right in all statements...........unfortunatly.

jjones
12-19-2005, 07:09 PM
Like Deepinhock, I am a hotrodder at heart and have a Fatman's kit in my M-5. It went in as advertized, handles well, tracks straight, and rides well. Turning diameter (outside) is better than the old straight axle at 37 ft., 6 in. and it doesn't try to rip my thumb off when I hit a bump. In short, its a great improvement over the straight axle and I am very pleased with it. With that said, I agree with Deepinhock, improve the existing suspension and upgrade with Turner brakes. Of course, it is your car, and your nickel, so...

jj

N8N
12-19-2005, 07:24 PM
Jeff...

I think I'm following what you're saying, although at least on the cars I've worked on, those aren't studs but regular Grade 5 bolts... just handwaving in my head, it seems like that might actually work OK - same effect as cutting the springs but without raising the spring rate. Only downside would be reduced ground clearance at the lower inner pivots. And, of course, there's still no anti-dive. If you don't lower the rear you'd actually be increasing caster which would make the car track better, but then again you might be throwing a little more weight to the front... meh. If I thought about this too much I'd end up staying up all night drawing and calculating <G>

Only gotcha that I see is that to *really* do it right, you'd have to lower it enough that the upper A-arm would never go "over center" in normal driving, as at least one theory is that that is why sagging front springs rip out the upper control arm mount bolt holes (got some Grade 8 fender washers on mine there...)

nate

--
55 Commander Starlight
62 Daytona hardtop
http://home.comcast.net/~njnagel

dclewallen
12-20-2005, 04:30 PM
A question on Jeff's idea of a plate spacing the lower control arms. Is there any certain thickness that would be best and after such a mod. is ther any change in the alignment specs? I'm not up on suspension mods but I would like to improve the steering and handling on my 53 Starliner [if I ever get it back from the body shop]. Thanks,

Darryl C. Lewallen

Alan
12-21-2005, 11:19 AM
It is best to leave things alone if you are not shure of what you are doing and do not have a good grasp on alignment techniques and a good 3D computer program. I bought a circle track program and pluged the Stude specs in it, the program crashed. Called the tech line they laughed at me. You have to remove the complete front end sheet metal run a lazer through the pivot points to the ground it is a 2 or 3 man opperation to get all the points. Then the Stude is so far out of modern specs that the program will not even accept the numbers. Don't even try unless you want to tear your last 3 hairs out.

DEEPNHOCK
12-21-2005, 11:59 AM
Well said Mike....
My diatribe was that there is no easy pill to take to solve a suspension problem, and that the stock Stude suspension is not all that awful bad. Sure, trunions aren't in all the hot rod magazines, but it works pretty well if you take the time to take care of it. Bump steer is about as minimal as you will get, without resorting to a drag link/ idler arm setup. I like some of the Vette adaptations, but like you said, the results are going to depend on the input and workmanship.
Jeff[8D]


quote:Originally posted by Mike Van Veghten

Jeff,

Stude Ackerman, no idea, never layed it out.
Stude bumpsteer....Stude missed, at least on my 2 (59 & 60) Lark wagons. I layed it out without a spring on my virgin 60 2dr wagon before I cut it up!! While not as bad as the Chevy II/early Mustang, it's not nearly as good as it could have been.

I spent a lot of time designing, laying out the details for my C4 Vette goodies, cutting out sheet steel, positioning and welding the bracketry/steering to achieve a near zero bumpsteer, the correct chamber change in corners, an amount of anti-dive that was a guess per a "roundy round" (computer) chassis program I borrowed, the ride height where I want it and as I mentioned, the Ackerman is about 2" too long.....not enough to hurt anything. Espically concidering the NASCAR guys run it so long it almost doesn't exist!
Believe me, no more comprimise here than any other "properly" designed and setup front suspension.

And If I may add, in "my" humble opinion....better thAn most.
See...the occasional Autocross is in the future for this particular wagon.

Take a close look at MOST chassis builders full chassis........they F-up big time..including Morrison (where I bought about half of my parts).
They have NO anti-dive, they have NOT done the correct geometry for correct chamber in corners (lean angles), bump steer....what's that.

When I asked the guy that helped me why...."most people won't spend the money for the correct setup. Each different wheel base, ride hieght, requires different geometry, that costs money".

He was right in all statements...........unfortunatly.


DEEPNHOCK at Cox.net
'37 Coupe Express
'37 Coupe Express Trailer
'61 Hawk
http://community.webshots.com/photo/42559113/426827941Lsvfrz
http://community.webshots.com/user/deepnhock

DEEPNHOCK
12-21-2005, 12:03 PM
I've ridden in (and driven) a couple of Ccab's and a CE that had a Mustang II aftermarket suspension in them and they rode just fine. Big improvement over a beam axle, like you said... Brought the nose down a bit on the Ccab, too.
Jeff[8D]



quote:Originally posted by jjones

Like Deepinhock, I am a hotrodder at heart and have a Fatman's kit in my M-5. It went in as advertized, handles well, tracks straight, and rides well. Turning diameter (outside) is better than the old straight axle at 37 ft., 6 in. and it doesn't try to rip my thumb off when I hit a bump. In short, its a great improvement over the straight axle and I am very pleased with it. With that said, I agree with Deepinhock, improve the existing suspension and upgrade with Turner brakes. Of course, it is your car, and your nickel, so...

jj


DEEPNHOCK at Cox.net
'37 Coupe Express
'37 Coupe Express Trailer
'61 Hawk
http://community.webshots.com/photo/42559113/426827941Lsvfrz
http://community.webshots.com/user/deepnhock

DEEPNHOCK
12-21-2005, 12:11 PM
He does some awesome suspension pieces....and his prices!
Yeow!![:0]
http://www.scottshotrods.com/
(I love their website front page... They spent beaucou bucks on a Chevy pickup roadster thing... I looked at it (the red one with the tan interior) and said "All that bodywork and the hood looks like a stock Ccab.... And who would haul hay in an upholstered pickup bed! Sheesh;)....
Jeff[8D]


quote:Originally posted by BeeJay

I'm using a Scott's Rod Shop front end. They will custom make them for what you need. Uses Must II spindles and rack. Tube "A" frames and coil-overs. Working fine for me. Have built two with this set-up. Drive well even on MI roads. Drives really well on the roads in other ststes I have been in.
Bob
Own '53 Commander Starliner. Red w/beige top. 350 Chev/700R4. Tilt,cruise,A/C.


DEEPNHOCK at Cox.net
'37 Coupe Express
'37 Coupe Express Trailer
'61 Hawk
http://community.webshots.com/photo/42559113/426827941Lsvfrz
http://community.webshots.com/user/deepnhock

DEEPNHOCK
12-21-2005, 12:16 PM
I never said it was the proper thing to do, only that I had seen it done in the past. Yeppers on the ground clearance thing, and on the camber change deal...
But it could be a poor man's alternative to a subframe kit.
Jeff[8D]



quote:Originally posted by N8N

Jeff...
I think I'm following what you're saying, although at least on the cars I've worked on, those aren't studs but regular Grade 5 bolts... just handwaving in my head, it seems like that might actually work OK - same effect as cutting the springs but without raising the spring rate. Only downside would be reduced ground clearance at the lower inner pivots. And, of course, there's still no anti-dive. If you don't lower the rear you'd actually be increasing caster which would make the car track better, but then again you might be throwing a little more weight to the front... meh. If I thought about this too much I'd end up staying up all night drawing and calculating <G>
Only gotcha that I see is that to *really* do it right, you'd have to lower it enough that the upper A-arm would never go "over center" in normal driving, as at least one theory is that that is why sagging front springs rip out the upper control arm mount bolt holes (got some Grade 8 fender washers on mine there...)


DEEPNHOCK at Cox.net
'37 Coupe Express
'37 Coupe Express Trailer
'61 Hawk
http://community.webshots.com/photo/42559113/426827941Lsvfrz
http://community.webshots.com/user/deepnhock

DEEPNHOCK
12-21-2005, 12:32 PM
Before changing anything on any suspension, irregardless of marque, you should bone up on what you have, how it works, and how to repair it. What exactly is wrong with the steering and suspension on your Starliner? Does it have power steering? Radial tires? New springs and shocks? Rebuilt trunions and inner bushings? Each of these things makes a big difference and all together makes it a different animal altogether.
I'm not pushing an agenda here, just cautioning spending bucks on change just for the sake of change...
Jeff[8D]


quote:Originally posted by dclewallen

A question on Jeff's idea of a plate spacing the lower control arms. Is there any certain thickness that would be best and after such a mod. is ther any change in the alignment specs? I'm not up on suspension mods but I would like to improve the steering and handling on my 53 Starliner [if I ever get it back from the body shop]. Thanks,

Darryl C. Lewallen


DEEPNHOCK at Cox.net
'37 Coupe Express
'37 Coupe Express Trailer
'61 Hawk
http://community.webshots.com/photo/42559113/426827941Lsvfrz
http://community.webshots.com/user/deepnhock

BeeJay
12-21-2005, 01:57 PM
Regarding Scott's prices: I bought two at the same time at an NSRA event. They were giving a good discount and free shipping. Cost me about $1900 each. The last junkyard Must II front end that I put under a '48 Chev PU cost almost $1700 by the time I stripped, sandblasted, rebuilt, and repainted everything. I figure that the $200 difference was worth it considering the labor involved. Admittedly the $2400 asking price is a little steep, but a pair of Aldan coilovers runs about $450, A new Must II power rack will set you back $200, A pair of new S-10 calipers runs $100+, New Granada rotors add $50 or so, throw in ball joints, bushings and steel material and maybe it;s not too much.

BTW, they shipped my first one next day air from Calif to Mich. 800+ pounds.

Bob

Own '53 Commander Starliner. Red w/beige top. 350 Chev/700R4. Tilt,cruise,A/C.

dclewallen
12-21-2005, 04:30 PM
Jeff, My Starliner has a totally stock front susp.. It's got a Ranger truck rear but it's hooked up to all stock stuff. The car rides a little stiff, corners quite well and the steerings not that bad [Ross box]. Just thought the plate idea could be an improvement, one that I could do as I'm a machinist by trade. Thanks

Darryl C. Lewallen

DEEPNHOCK
12-21-2005, 07:20 PM
I am not sure, but dig around for an old Fenton catalog..
The Speed and Custom shop in Punta Gorda Florida used to sell them, but they packed up and moved to Michigan and I don't have their web address..
Jeff[8D]


quote:Originally posted by dclewallen

Jeff, My Starliner has a totally stock front susp.. It's got a Ranger truck rear but it's hooked up to all stock stuff. The car rides a little stiff, corners quite well and the steerings not that bad [Ross box]. Just thought the plate idea could be an improvement, one that I could do as I'm a machinist by trade. Thanks

Darryl C. Lewallen


DEEPNHOCK at Cox.net
'37 Coupe Express
'37 Coupe Express Trailer
'61 Hawk
http://community.webshots.com/photo/42559113/426827941Lsvfrz
http://community.webshots.com/user/deepnhock

64Avanti
12-22-2005, 02:04 AM
Alan,

I have a program that will accept the Studebaker suspension points. I have not had the time to take measurements.

I hear a lot of complaints about the Studebaker suspension. Most of these complaints come from people who never drove a Studebaker with low mileage. A Hawk with the heavy duty suspension and rear sway bar radial ply tires and good shocks handled much better than almost any American car of the 60's. (A 63 or newer Corvette or 65 or newer Corvair with good tires was better.) The R3 cars had the upper inner pivot point lowered to increase the camber gain and you can notice the improvement.

Even most of the restored Studebakers I have driven have not had enough attention payed to the steering and suspension.

Another big problem is that many people have sagging front springs. This hurts the geometry. Of course if you lower the front by cutting the front springs you have the same problem. There are better ways to lower the front. I will have some parts to do this in the coming year.

David L

Alan
12-22-2005, 03:08 PM
Dave, It wasn't the suspension points it was the king pin parts, all new computer programs are for ball joint piviot points. The program wants you to put in the centerpoint of the pivot and king pins don't pivot.

Roscomacaw
12-22-2005, 03:11 PM
I recently had the opportunity to drive a '63 Wagonaire that had had extensive work done to it in the power, suspension and braking department. Better yet, I got to drive it thru twisty mountain hiways that I was well familiar with. I was amazed at the way that boat handled!!![:0]
It wasn't so much that the hot 289 was so willing (and it was) as how the Turner brakes and totally rebuilt, resprung (HD springs & shocks) and properly aligned front end made that car drive! DAMN! It was truly exhillarating to sweep thru the curves at 60+MPH as tho it was on rails. And this even tho the rear shackle bushings were litterally letting the rear springs flop to and fro![}:)]
My friend and fellow Stude nut, Ken Pyle, had performed all the work (including a masterful engine rebuild with Mike Van Veighten's tweaked heads installed) on the front end and brakes - installing factory PS in the process. Since Ken's vehicle storage ability is limited, I stored the car at my place until it's owner (who was away, involved in rescue work post-Katrina) could come and pick up the car. I put a couple hundred miles on it at the request of the owner to get my opinion as to how it all turned out. Needless to say, I had nothing but praise.

http://images.andale.com/f2/115/106/906179/1134113837857_S2400208.JPG

BTW, Ken specializes in Stude work (he does brand X stuff too, to keep the rent paid[xx(]) and I'd recommend him if you want an engine rebuilt right and reasonable. He doesn't pick up OR deliver but having him do your engine is worth the trouble to get it to him.;)

Anyway.... the point I was trying to make is that a freshly built Stude front end is a delight to drive! Do it right, keep it greased, enjoy it for life![:0]:D

Miscreant at large.

1957 Transtar 1/2ton
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe
1957 President 2-dr
1955 President State
1951 Champion Biz cpe
1963 Daytona project FS

Roscomacaw
12-22-2005, 03:27 PM
I forgot to add that Chuck Collin's Delrin A-arm bushings have got to be an improvement if you're willing to go with them.
I personally don't buy the argument that they make the car noisier.[}:)] I've never thought of the 50, 51 & 52 cars as unreasonably noisy over the later ones. And those earlier cars had METAL bushings on the inner A-arms.[:0]
In fact, witness that R3-R4 Avantis had those early 50s vintage metal bushings were brought out of retirement by engineering to stiffen up their front suspensions! Delrin's gotta be alot better than rot-worthy rubber!;)

Miscreant at large.

1957 Transtar 1/2ton
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe
1957 President 2-dr
1955 President State
1951 Champion Biz cpe
1963 Daytona project FS

Mike Van Veghten
12-22-2005, 04:48 PM
So it runs..........cool!

Was the overall engine performance up to expectations? Resonable power on request?

Mike

64Avanti
12-22-2005, 07:34 PM
Alan,

The program I have will handle king pin type suspensiona.

David L

Roscomacaw
12-22-2005, 07:46 PM
Mike, It was yet to recieve it's New Edelbrock when I was driving it. It sports Ted's R2+ cam, semi-cup pistons, large dual exhausts and a high stall torque convertor. What it needed (and still hasn't gotten, since Mike's son has just gotten hitched and as I said was away in New Orleans for some time), is to have it's distributor reworked to match the cam.
It sounds meaner 'n hell with that cam but it's low end performance was uninspiring (of course, I never did try holding the brakes and bringing the revs up before launching it. (Truth is, the miles I put on it were all but the very first and I wasn't pushing it too hard.)
I CAN say that after about 30MPH it was HANG ON NELLIE!!!![:0][:p]:D. I only had it to 90 once or twice and it felt like it wasn't even trying yet. LOTS more zip just waitin' to be unleashed! Lots more![:p]

I'm dyin' to hear when the kid gets around to having Bud Alenic reset the distributor curve and apply the Edelbrock in place of the WCFB that's there now.
The car also needs a vacuum resevoir for the power brakes to be effective at low speed. That and an Avanti starter to handle the high compression that engine sports now. ( I don't know what it is or if maybe it's the starter being tired but it has a tough time turning it over once it's hot. I should have thrown my amp meter on it to see what it was drawing but I never did.)

I can say that the kid and dad were both tickled pink with the way the car runs and drives. So much so that they thanked Ken after they'd had it back for awhile.:D

Miscreant at large.

1957 Transtar 1/2ton
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe
1957 President 2-dr
1955 President State
1951 Champion Biz cpe
1963 Daytona project FS