Watts Link for improved street manners

DevGittinJr

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One final comment to make on using Dean's car as a "perfect" model...

WHOA! WHOA! WHOA! WHOA!

Everything you said makes sense, and the .02% is a very good point that I was overlooking. But I wasn't using his car as a model, nor was I even implying that he's necessarily right. A few of you are on a whole other level of knowledge, pertaining to the s197 and vehicle dynamics in general, than the rest of us. I was just trying to maybe understand why someone who more than likely is at least on your level, seems to see it differently, and you gave us some solid food for thought as to why that may be.
 

SoundGuyDave

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LOL!! I think you mis-understood where I was coming from, or what I was trying to say. That usually means that I just wasn't being clear.

I wasn't suggesting some sort of bro-mance over Dean, or Dean's car; but let's face it... It's one of the best-sorted, most well known cars in the S197 community, and both it, and particularly HE, are fast. What I was really trying to point out was that he is driving in a race series that has a SERIOUS rule book. About 15 pages are devoted to performance-enhancing drugs! HALF the art of racing is in maximizing any and every allowance that the rulebook gives you, and damn the cost.

You may not have necessarily been implying that he was right, but I'm also not necessarily implying that he's wrong either.

He's a pro-level driver, and successful. I'm a good, but not great, club-level racer. That the objective reality of the situation. I have put a good amount of time into trying to understand the vagaries of the S197 because I race one, but I do so without his resources and financial backing. Every part that I put on the car was paid for in my own sweat. I've made some bad choices, or put parts on the car that I thought would do one particular thing, and they didn't. I've also made some reasonably good choices, given my financial ability. I have single-adjustable AST 4100-series dampers, not 3-way Sachs or Motons because I flat can't afford them.

In the end, all I'm really trying to do is pass on the knowledge, and dispel pure myths or gross inaccuracies when I can.

We all WANT to be Dean Martin (or Randy Pobst, or Boris Said, or Leh Keen, or...), and there's nothing, really, that says one of us can't be that good. But when I see posts from one guy who only does "Coffee and Cars" to another guy who's doing his first HPDE-1 day in a month, and the discussion is all about "gotta have a Watts, and a Torque Arm, and a Supercharger, and..." it just drives me a bit batshit.

When it comes time to buy parts, though, if you have a reasonably solid understanding of how the suspension actually WORKS, you can make in informed decision about whether part A or part B makes the most sense for your particular situation. If you don't have a resonable grasp on what the hardware can do for you (both benefits AND drawbacks), then you're only left with the anecdotal "noise" emanating from the interwebz, with dubious amounts of value. If you search hard enough, I'm sure that you can find a guy claiming a half-second lap decrease just from changing his valve-stem caps to a more aerodynamic design... As can be seen from this thread (and countless others like it), there's a LOT of misconception surrounding some parts or classes of parts, and it seems to go hand-in-hand with lack of understanding of basic suspension operation and theory.

Best we can do in this little corner is try to shine a light on the tech end of things, and let those that want to actually understand how this stuff works. If they do, suddenly a lot of "must have" choices vaporize, and the "right choice" suddenly becomes clear.
 

DevGittinJr

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I wasn't suggesting some sort of bro-mance over Dean, or Dean's car

Actually, I'm kinda crushing on Nate Stacy's car. Seriously though, there are lots of good drivers out there. The reason why the things Martin says carry so much weight (at least with me) is he's not just a good driver. He was a chassis engineer with Ford until '04. There's a very good chance he helped develop this chassis, and there are probably very few people that know this chassis better than he. I learned after the first time I replaced the entire suspension on this car, not to just blindly follow what the PWC guys are doing though.

In the end, all I'm really trying to do is pass on the knowledge, and dispel pure myths or gross inaccuracies when I can.

"Sometimes you gotta blow your whistle and throw a flag."
 

Norm Peterson

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I also take your point on the "essentialy nonexistant" change that imparts. I'm going to stick with my statement, where any effect from this is going to be lost in the "noise" of other things like tread squirm or carcass deformation.
Heh . . . I'd defy anybody to notice axle steer caused by lateral axle shift in the S197 even if it was the ONLY effect present.


Norm
 
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El_Tortuga

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And there we have it. Several points to consider when looking at "awesome results with a Watts install."

1) Bushing compliance. This is particularly true if you go from a stock PHB to a Watts, which will be equipped with either poly or rod-end bushings. Just losing that compliance will tighten up the rear end "feel" dramatically. Between stock bushing compliance and tire carcass squirm, all the other factors are just lost in the "noise."

2) Roll center location and migration: When installing a Watts, it usually winds up changing the roll center as well, unless the pivot bolt is in EXACTLY the same vertical location as where the PHB crosses the axle vertical centerline. Migration of the roll center is indeed an issue, and is what causes the "different feel left to right" that some report with a PHB.

3) Other mods. Generally speaking, a Watts install isn't done in isolation, but is in conjunction with other things, like dampers/springs, control arms (bushing deflection!!), or even a torque arm. So once you throw somebody's entire catalog at the car, what, exactly, is responsible for the effects you observe?

4) Confirmation bias. Let's face it, this is human nature. If you just dumped a thousand bucks and a bunch of man-hours into a project, it's natural to say something on the order of "OMG!!!!1111 It's incredible!!" on a subjective level. On an objective level, there may have been no change, but the perception is still that there was one.

Pros/cons: A Watts is absolutely superior at acting as a lateral location device for the rear axle. There is (+/- bushing deflection) NO lateral shift whatsoever under bump or droop, the axle just moves vertically. A Panhard does move in an arc, which allows some shift to occur. Again, taking bushing deflection out of the equation, and applying the ole Pythagorean theorum, we find that that lateral movement is something on the order of 0.050" or so, not the "INCHES!!!1111" that are sometimes bandied about. So, why NOT go with a Watts? First, weight. The PHB is lighter, both sprung AND unsprung. Second, complexity. The PHB is simple to set up, and stupid-simple to maintain. The watts has a lot more moving parts. Third, price. You can find a nice rod-ended PHB for around $160, but Watts links can push past a grand.

I'm honestly not trying to push anybody one way or the other, it all comes down to what YOU want to do with YOUR car. Autocross folks that hit slaloms will feel that roll-center migration a lot more than road-course drivers ever will. And not everybody is running wall-to-wall meat in the rear wheelwells where that slight axle shift can cause rubbing... All I'm trying to suggest is that you think it all the way through, understand what the parts are doing, and then make an informed choice. Nothing more.

WL has more pivots = more bushings. Unless you are on spherical bushing, wouldn't that negate a chunk of the potential L-R positional control?

Poly ended adj PHB does well enough for me. Am running 315s without any rub.
 

tjm73

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Funny. I got a newsletter from Maximum Motorsports with this video about this very question.

 
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JeremyH

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Coming from the older stangs I never liked the feel of the 3 link in my 07. I run the watts link for street use and prefer the feel. Especially on the crappy roads in my area. I don't corner carve and never will, my decision was based on feel for street use on less than spectacular roads. For that is makes a huge difference for me in rear end feel.
 

SoundGuyDave

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Here's the text from the email:

Maximum Motorsports said:
MM's exclusive new undercar video debunks the notion that a Watts Link is better than a Panhard Bar for late-model Mustangs. In the hard cornering situations shown in this video, an MM Panhard Bar on a Fox/SN95 Mustang allows only 0.079" of lateral axle movement relative to the chassis. The real story is the movement caused by tire sidewall flex: a whopping 1.75" in this test.... [read more] Want the details and expert Tech on how we reached this solid conclusion and why winning racers agree? We've dedicated a whole page of our web site to the topic!

The points to take away are lateral motion is 0.079" on the axle. Tire sidewall deflection is 1.75". That makes the PHB component of the net shift such a vanishingly small portion of the total that it's essentially non-existent. Speaking purely in terms of lateral shift, there is therefore NO appreciable difference between a PHB and a Watts.

"Feel" is of course subjective, and not subject to argument, as it is a personal opinion. "Feel," however, is also the sum of a wide variety of factors, including (but not limited to) bushing compliance, tire carcass shift, chassis torsional flex, roll center height, IC location, roll-steer characteristics, etc. In other words, everything depends on everything else.

The bottom-line take-away, though, is that a Watts is not a "magic bullet" when considering lateral axle location. We've done the math here, we've looked at the physics of it here, and now we have outside confirmation from a pretty unimpeachable source. Yes, MM sells PHB's, but the guys over there are racers and engineers first and foremost.
 

stevbd

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The MM video is an interesting and convincing discussion of a totally different subject - total lateral deflection of a PHB vs. Watts link during hard cornering on a smooth racetrack. The subject of this thread - and a topic which thus far remains frustratingly unanswered from any science or tech perspective - is whether a watts link is a real improvement in bumpy road manners during daily driving.

I think the still outstanding question is whether there is some scientific or engineering reason why a watts link might allow the rear tires to maintain better contact with the road over bumpy surfaces compared to a PHB. Anecdotally this seems to be the case but obviously a lot of us are looking for a tech discussion.

Let me emphasize, I am not a cheerleader for or against a WL. I am just considering this device and would love to have some engineering explanation for what is going on over rough road surfaces, pros and cons, before dropping $1K to experiment.

Apologies if I am coming across as grumpy, but let's be clear that so far no one has brought any science or tech to the specific question at hand.

And respectfully, I disagree that "feel" is not subject to good faith argument and some degree of quantification. For example, these Bilstein shocks I put on my car improved the "feel" over bumpy roads compared to worn out OEM shocks in a way that can't be clearly measured with a tape measure but which can be explained from a technical perspective and which is undeniably real and significant. There is a lot of (admittedly anecdotal) evidence that a WL also improves "feel", and it seems like a disservice to the discussion to just ignore those reports.
 

tjm73

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I don't believe a panhard rod or a watts link has much of anything to do with maintaining better tire contact. Tire contact is controlled by the shocks, springs and sway bar. A panhard rod or a watts link only controls lateral axle movement. I could be wrong and they may have a small impact.
 

SoundGuyDave

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The MM video is an interesting and convincing discussion of a totally different subject - total lateral deflection of a PHB vs. Watts link during hard cornering on a smooth racetrack. The subject of this thread - and a topic which thus far remains frustratingly unanswered from any science or tech perspective - is whether a watts link is a real improvement in bumpy road manners during daily driving.

I think the still outstanding question is whether there is some scientific or engineering reason why a watts link might allow the rear tires to maintain better contact with the road over bumpy surfaces compared to a PHB. Anecdotally this seems to be the case but obviously a lot of us are looking for a tech discussion.

Let me emphasize, I am not a cheerleader for or against a WL. I am just considering this device and would love to have some engineering explanation for what is going on over rough road surfaces, pros and cons, before dropping $1K to experiment.

Apologies if I am coming across as grumpy, but let's be clear that so far no one has brought any science or tech to the specific question at hand.

Here's the point that I would make to all that: The ONLY function that a Watts or PHB has is to locate the axle laterally. And while the video showed a "smooth race course," you could still see that there was negligible axle motion due to body roll (which is identical, mechanically, as a one-wheel bump), therefore you could use this as a model to ascertain if the lateral axle motion is the culprit in your "unsettled feeling."

My personal suspicion is that spring rates and damper valving, along with the nature of a live-axle suspension are the real causes of your complaint. If you were thinking it was the body swaying back and forth over the axle, I think we can pretty well consider that one "busted."

And respectfully, I disagree that "feel" is not subject to good faith argument and some degree of quantification. For example, these Bilstein shocks I put on my car improved the "feel" over bumpy roads compared to worn out OEM shocks in a way that can't be clearly measured with a tape measure but which can be explained from a technical perspective and which is undeniably real and significant. There is a lot of (admittedly anecdotal) evidence that a WL also improves "feel", and it seems like a disservice to the discussion to just ignore those reports.

I agree with you 100%. Feel, while not QUANTIFIABLE, is absolutely a QUALIFIABLE thing to consider. No argument whatsoever, and I will further agree 100% that it matters, period. A comfortable car to drive is a pleasure, and a skittish one not so much. The point that I was making is that there are a LOT of factors (some which I listed above) that make up the whole of the "feeling." It may be (for example) that the roll center is what is driving your complaint. If so it's EASIER to change with a Watts than it is with a PHB. But if you don't investigate the variables, you'll never really know whether that shiny new bit of kit (whatever it is) will actually cure what ails you, or whether it'll just be a piece of hardware you bolted in to "no effect." It could also be rear-tire tramlining over broken pavement that's creating that unsettled feeling, in which case no suspension piece in the world is going to fix it. A different tread pattern would, though.

Since the discussion was about the Watts, I think we can rule out lateral location as the culprit, therefore the choice of Watts or PHB is immaterial. Whether the Watts gives you something else that might fix your problem (bushing compliance? Roll center height?) is another matter entirely.
 

Norm Peterson

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Maybe we need to stop looking at the 1-wheel bump situation as resulting in purely vertical travel of the involved wheel & tire and consider it as an arc about the opposite-side tire contact patch. Yes, it's another 0.0x" kind of "error", but perhaps it's the sum of all these little "error functions" that people notice on more of a subliminal level.

There will be some vertical tire loading asymmetry on a force basis, where the vertical component of PHB force is concentrated much closer to one rear wheel than the other (the PHB is horizontal only at unique combinations of static settings, bump/rebound travel, and roll). I'm pretty sure that this is a jacking effect that adds to the effect of vertical roll center migration, in the S197's case reducing geometric LLT + PHB force unweighting of the left rear in left turns (understeerish) and increasing it in rights. More small/smallish effects, but I don't think they're cancelling each other.

Axle roll steer becomes a tiny bit more understeerish in left turns, at least relative to right turns. This is a function of asymmetric rear RC height migration, separate from the LLT through the RC's effect.


I'm not sure how this affects a sensation of 'skittishness' other than it possibly being because the summation of all these little asymmetries doesn't "zero out".


Norm
 
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Smokievol

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Just to provide some more scientific analysis.
My WL wattlink has improved the street manners of my mustang
Installed for two weeks now. Have had the same suspension mods for 3+ years now. Koni yellows with Steeda sport springs and BMR relo brackets.
 

Norm Peterson

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Just to provide some more scientific analysis.
My WL wattlink has improved the street manners of my mustang
In what respects, exactly?

Drive it some more first, then try to describe specifically what it's doing better than the PHB before it was, and what it's not doing that the PHB did do.

Was your PHB the OE PHB or was it an aftermarket offering?

I'm being serious here.


Norm
 
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tjm73

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The placebo effect is strong in this thread.

See also: confirmation bias.

Similar thoughts happening over here too.

How was this scientific exactly? Please describe your scientific method.
 

stevbd

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Let's try this discussion from the other direction. Has anyone who says the WL is over-rated actually driven one on a bumpy road?
 

Smokievol

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I guess you guys don't always pick up on tongue and cheek humor.
In my thread I also did not use the word Greatly, it has improved the manners, but I was expecting more.
I'll follow up with more biased seat of the pants feedback later on.
 

2008 V6

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This thread sure did bloom –
An aftermarket watts link will be a vast improvement over the stock panhard bar – less compliant bushings / stiffer, lower roll center dependent upon setup.
A properly set up panhard bar needs to be located lower than the original / stock setup, long as possible and parallel to the ground at ride height.
This is crucial - Determines the roll center and the length determines lateral movement.
A Panhard will loose ground clearance for the entire length of the axle as opposed to the watts 1/2 axle.
Lateral movement for a Watts VS Panhard bar is kinda a wash (Not much suspension travel) but the weight savings of a Panhard bar I consider to be significant though a fraction of the axle weight.
Unless the 170+ or so LBS of our axle components can be controlled properly with spring / shocks and less compliant bushings, our boats will jump, bounce, squirm, skitter, skip all frigin over the place on bumpy surfaces -Thus a heavy straight axle linked to a frigin heavy boat with so so / cost effective suspension design..
I have a 1994 GT Mustang also – never a street car – Maximum Motorsports everything including torque arm. One of 8 cars to receive this setup from what I was told by MM don’t know how many left in one piece. It handles exceedingly well but it ain’t no BMW or Corvette on bumpy surfaces because of the frigin heavy straight axle and poorly designed platform.
I like Mustangs because they are cheap to Replace / fix when you bend them.
Work with the platform you have. Everything has it’s advantages and disadvantages. If you don’t want a cheap high HP straight axle car - pre 2016 MUSTANG, – spend more – buy a better platform - Corvette or similar Vehicle. Panhard VS Watts debate has been going on longer than I have been alive both have pros & cons.
Did I piss anyone off yet LOL.
 
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