Front Axle / Front Suspension: Front suspension design

[Corley]

OK you experts, tell me what advantages there are to the swept back front suspension components as shown in the top half of my expertly skilled drawing below. (I like to show off my artistic talents from time to time.) This, of course, is a top view, and many cars use a straight on approach as is illistraighted in the lower half drawing. Also, what are the drawbacks to both...

Of course this is not a simple answer, and there are many things at play in front suspension design, way too many to address here, so try to keep on subject here, we are asking only about the swept back upper and lower arms mounting position, as opposed to the non-swept designs. I know all later Studes used this swept design, why? Your opinions may help settle an argument/discussion I've had on this subject with a friend....

Thanks in advance, for any knowledgeable input, and if you don't know, feel free to speculate, please just let us know if you are only guessing.

[PackardV8]

OK you experts, tell me what advantages there are to the swept back front suspension components

In every suspension design, there are tradeoffs. More of one sometimes means too much of another or not enough of the other.

Angling the front A-arms rearward in general makes the suspension more compliant to bumps. The Volkswagen trailing arm front suspension is the extreme example of this. However, it can increase the tendency to dive upon hard braking.

Perfectly perpendicular A-arm mounting generally makes the suspension equally resistant to dive, lifting, rolling, but slightly less compliant.

The current suspensions with tall, complex spindles can do amazing things with suspension geometry; combining movement formerly considered impossible. They can lean tires to the inside of the turn, while also suppressing body roll to the outside.

jack vines

[Mike Van Veghten]

The other thing to concider...is packaging.
If one were to take the Stude arm length and straighten it out, there would be no room for the engine. And like Jack said, the longer arms are much more compliant to the road surface. Shorter arms would be much more harsh and more difficult for the designers to dampen to the customers satisfaction.

When I put the C4 Vette suspension into my 60 Lark, 2dr. wagon, my first thought was to "not" cut the frame. But after setting the control arms in place with the spindle attached, it would have put the tires mostly outside the body..! So I cut the frame off and made my own subframe with about a 3"+ "U" section to allow the tires to stay under the body and use the Vette suspension as designed.

http://public.fotki.com/-Mike-/60_lark/

While I've got a small Chevy going into this car, there is plenty of room for a Stude to go back in, or most anything else. My problem will be to be able to work around the suspension to plumb the engine, install the steering etc.
The factory, would have a nightmare doing this for general consumption.

Mike

[Corley]

I'll offer up another drawing, this one shamlessly stolen from one of LeRoy "Tex" Smith's books, that shows how one can offset that dive / lift mentioned in Jacks post (post#2). But really, that's not the question here, just an interesting side topic... (Lucky for you, I didn't exercise my artistic skills on this one, just my theivery skills.)



Mike (post#3), I don't think Jack mentioned long vs short A-arms, so you may be reading something into his post. Longer arms MAY be more compliant, but that doesn't seem to me to be a given, when you consider the minor difference in length and all the other components involved.??? JMHO Also, if Studebaker were to straighten the arms, leaving the length alone, the front would go in about 1/2 an inch, and the back would come out about 1/2 an inch to maintain the same track width (just guessing there). I'm not at all sure that would present any engine plumbing issues, but there, I'm being too picky I think.

[PackardV8]

Corley, help us out here. Exactly what are your questions and why would moving the mount to square the arms to the body be a good thing to do?

jack vines

[Corley]

Jack, I certainly do NOT advocate moving the mount to square the arms to the body, and I do NOT advocate it is a good thing to do or a better design. All that talk was in response to Mike's engine plumbing post. The question was as stated, what is the advantage of using the swept back approach? Your answer was that it made for a more compliant suspension, and I agree it does do that. Mike's answer was it makes for more engine room, and I can't really see that point of view.

However, most of the after market Pinto/Mustang II front suspension swaps do not use the swept back approach, I suppose because the original Pinto/Mustang II did not do it that way. Ford apparently didn't think the swept back idea was worth doing, and Studebaker did think it was worth doing I guess, so I wonder why? By the way, like you, I'm firmly in the camp that say's it makes the suspension more compliant to bumps, ruts, and obsticles, and like you I think the early VW bug takes this to the extreme, and works really well. But, I still wonder what anyone else may think could be a different reason to do it??? My friend seems to think it is only about improved cornerring, I just can't see that, but maybe I am wrong and am open to being convinced it is for some other reason???

I like to look at things and figure out why they were done the way they were, and learn something from that exercise... But that's just me...

Anyway Jack, thanks for your response and interest.

[48skyliner]

There was a recent discussion on here somewhere about Ackerman angles, which addressed some of the issues. When you start varying the steering axis angle(formerly known as kingpin inclination), Ackerman, scrub radius, anti-dive and anti-squat, and then throw in the angles you are asking about, it gets really complicated. I honestly believe some designers use the pivot axes level and parallel to the vehicle centerline because they know how to analyze it! I think the only consideration at Studebaker was getting everything into the engine compartment - can't believe they were the least concerned about handling.

Carroll Smith's book "Tune to Win" is a good reference. I built a model, as Smith had suggested, and was able to easily find a set of dimensions that met my requirements. But with the added complexity of the angles you are describing, a three dimensional model is the only way I could solve the problem. I do have friends who could do it for me on their CAD programs. When we built the Stiletto, we had an extremely wide motor (transverse straight six) and we had to build the frame and A-arms to fit around it. I was only concerned with no track change on compression and rebound, didn't care about camber change with these skinny round tires.

If you don't mind building some A-arms, you should be able to make just about any geometry to work. My friend Sean, who built the suspension shown here, has built some custom A-arms for guys racing Porsche 944 and 968, which replace the cast aluminum arms and are fully adjustable like those shown here. I am sure he would be glad to consult with you if you want try your hand at some fabrication.

[sals54]

I think its important to remember the roads that these suspensions were designed for. Compliance was probably MUCH more of a concern back then, than handling. Freeways were yet to be born when these suspensions were built. The cars needed to be sturdy and able to take a lot of punishment from the pot holes, dirt, gravel, uneven surfaces, debris, etc. It seems to me they survived pretty well, all things considered.
I dare say, if you were to take one of these modern cars, with superior handling, back to the roads of the early 50s, they would get severely torn up before 25,000 miles were clocked.

[t walgamuth]

I don't have a lot to contribute to this discussion but will offer the following observations:
1. Studebaker was building fully independent suspension in 39 and in 39 used a transverse front leaf spring which dictates a straight out a arm.
2. I disagree with the idea that handling was not in their mind when this was designed.
3. The Studebaker engines had a rear pan design so pushing the axles back in relation to the a arm pivots does allow a more compact overall design while the longer a arms allow a more compliant ride perhaps.
4. Starting in the forties and fifties the us mfgrs pushed the engine further and further forward IMHO as a way to build cars less expensively....less front end less metal etc.... while leaving more room in the passenger area. Moving the seats forward also would have given a better ride.
5. Now the only cars with the engine back from the front wheels are front engine sports cars which still have the tranny attached to the engine instead of a transaxle.

[Skybolt]

I think its important to remember the roads that these suspensions were designed for. Compliance was probably MUCH more of a concern back then, than handling. Freeways were yet to be born when these suspensions were built. The cars needed to be sturdy and able to take a lot of punishment from the pot holes, dirt, gravel, uneven surfaces, debris, etc. It seems to me they survived pretty well, all things considered.
I dare say, if you were to take one of these modern cars, with superior handling, back to the roads of the early 50s, they would get severely torn up before 25,000 miles were clocked.

That's one of the most important factors to consider. One could not drive a front wheel drive Honda Accord, as an example, on most of the roads before the 1970's. In Australia, where I'm from, one was lucky to have a car last 100K miles before the 1980's. Road conditions are much better now and this allows suspensions to be designed with a more road going design as opposed to a light duty truck. I took a 1964 Cruiser up a hill that was used to test 4x4's in Broken Hill, NSW. Australia. The only thing that got a scratch was one of the mufflers which received a dent on the front from a large rock I couldn't avoid. There is no possible way most modern passenger cars could do that. No way at all. Given the demanding conditions of the time these cars have more than adequate suspension for just about anything you could throw at them. Adding a few upgrades to the handling like sway bars, radial tires, alloy wheels, gas shock, etc.. makes for a very comfortable ride and they still handle what most of us need and could go further down the beaten path than I would like to, or care to, take many modern cars.

I just thought of a prime example. When I bought my first Studebaker, a 1961 station wagon, in 1981, I lived down a dirt road. In the wet season it was at times impassable. Sometimes you only found out when you got stuck. The ruts and channels in the road took special care to avoid getting stuck even in dry weather. So that is the road. Now I went back during a dry period a few years back. The road is now taken care of by the local council and not the property owners so it's in better condition. In 1998 I took my 1975 3.0 BMW down it to visit a friend and on the way out hit a rock which put a compression crack in the alloy oil pan. That car was made for beautiful German roads not where I was taking it. I would take my 59 Lark down there in a heartbeat but I could not sit at 120+mph hour after hour on a freeway. So there is always a trade off. Because I have no intentions of sitting at 120 mph all day I will take the suspension that will take me anywhere I might like to go knowing it will bring me back home again.

[Mike Van Veghten]

Corley wrote -

""Mike's answer was it makes for more engine room, and I can't really see that point of view.""

It's NOT a point of view..! It's fact. If you look at my pictures (my Lark) and notice how close to the center of the car the control arms are, you'll real quick that a LOT of room is taken up by straightening the arms 90 degrees to the centerline of the car.

As Jack notes, suspensions are a trade off of MANY items. Space limitations is one of them. Many cars have arms that are "about" 90 degrees to the CL of the chassis, many do not.

The designers do what they have to do to fit everything.
You may notice....the better handling "A-Arm" cars...those control arms basically stick straight out..!

Mike

[Alan]

If you look at the front suspension of a early 50's Chevy, it is identical to the Stude in most ways.

[PackardV8]

If you look at the front suspension of a early 50's Chevy, it is identical to the Stude in most ways.

Including the '53-62 Corvette.

While much has been learned about suspension design in the past sixty years, for occasional street driving, there's really nothing wrong with the Studebaker/Avanti/Corvette suspension.

jack vines

[64Avanti]

The fact that the lower a-arms are swept back has no influence on the suspension geometry. So I suspect that making room for the engine was the driver for the design. I also don't believe that compliance had anything to do do with it.

[Corley]

OK, time for "TRUE CONFESSIONS". I started this topic for an entirely different reason than stated. (Sorry if you consider it trickery, but in reality, that's exactly what it was.) Here is what I did:

I posed a question, asking for expert opinions. I also said, "... if you don't know, feel free to speculate, please just let us know if you are only guessing". In this case, the question didn't matter, and could have been "is the world round?". What I was after, was an indication of how many people would clearly indicate that they were in fact NOT a suspension expert, but were SPECULATING, or GUESSING. Albeit guessing can be an educated guess, it is still not expert opinion, which is a different thing all together.

64Avanti (whom I suspect just won the lottery, him being from San Jose and all), came the closest, when he said "So I suspect that...". Now I know for sure that the other posters: a) Either consider themselves "Experts on suspension", or b) simply can't read and comply with what is asked. I SUSPECT (and it is only my opinion), they are not, in fact experts on suspension.

Before you get all hot and bothered by this trickery, let me defend myself by saying it was meant in good fun, and only to point out that when we do post, we are usually not experts, we only just have our opinions, same as everyone else. And contrary to what some may believe, one opinion is often just as good as another opinion. Of course some people do know a lot more about certain things than others know about said subject, but it's always nice to see when someone realizes and let's us know they are not an expert, their reply is only an opinion.

There are some on this forum (and all forums I suppose), who would almost demand that their opinion is the only truly corrrect one. Not many, but "some" forum members. I would encourage them to be nice guys and leave room for everyone's opinions to be heard. That's just what I think, my opinion.

(By the way, all the research I've done on the suspension question posed, has come up dry, so your opinion, whatever it be, is just as good as any other one to me. It may be right, it may be wrong, I can't say, I'm not an expert.)

Happy New Year ALL! Please play nice on the forum next year!