Fays Watts link

[Kaldar142]

Great product either way, definitely improves ride quality

 

[gzmo]

I'm trying to understand exactly what this does, so if someone could explain it for newbs like me, that would be great

 

[SoundGuyDave]

The Watts link is used to positively locate the rear axle, and keep it from shifting side-to-side. The car is OE with a Panhard bar, which attaches to the frame at the passenger side, and the axle at the driver's side, but as the suspension moves up and down, that allows the axle to shift *slightly* from side to side as the bar describes an arc. The Watts link eliminates that motion entirely, and some designs allow you to adjust the rear roll center with relative ease.

TANSTAAFL: The Watts is heavier, more expensive, and tends to concentrate all of the forces on a single point, which if improperly designed, fails with dramatic consequences... I am NOT saying the Fays exhibits this issue, but it is endemic to the Watts design.

Clear as mud, eh?

 

[gzmo]

Damn, that clears up a lot lol. Thanks for the info. I'm looking into it seeing if its something I do or do not need right now.

 

[Sleeper_08]

For an interesting explanation of the Watt's link which was invented in 1784 you can go to here;

http://en.wikipedia.org/wiki/Watt%27s_linkage

 

[Sam Strano]

TANSTAAFL: The Watts is heavier, more expensive, and tends to concentrate all of the forces on a single point, which if improperly designed, fails with dramatic consequences... I am NOT saying the Fays exhibits this issue, but it is endemic to the Watts design.

Clear as mud, eh?

It is heavier, but not as much as many folks think. Fays2 links (which I have on my car and supplied Sleeper08 with) use billet aluminum bellcranks, and aluminum arms. The frame is steel, as are the axle clamp. But then again, the stock PHB and brace are as well. And the entire frame, bellcrank, two of the 4 rod-ends and half the arms are all sprung weight. There very very little increase in unsprung mass. And even having said that an entire Watts is less than 30 pounds boxed up. It's more like 27 or so including all the hardware. The stock stuff is around 10 pounds. So yes, there is weight---it's not 50 pounds. It's far from all unsprung, and if you are going to carry it down low and to the rear ain't a bad place.

As for the stresses being up on a single point. That's true. But it's also why a grade 8 bolt 3/4" in diameter is used for the propeller/bellcrank. That way, WAY bigger than any bolt that holds the PHB in place. In fact the Tensile strength of that bolt is over 50,000 PSI.

Yes there were some bolt failures on Saleen watts links, but they were largely due to binding IMHO. The Fays2 bellcrank uses not only one, but TWO sealed bearings to insure the bellcrank does not bind and put any undue stress on the bolt.

I have Watts links on both my Mustang and my Camaro. I wouldn't trade them for PHB now that I have felt the difference. No way, no how. PHB's are nice and cheap but not exactly a perfect design.

 

[SoundGuyDave]

It is heavier, but not as much as many folks think. Fays2 links (which I have on my car and supplied Sleeper08 with) use billet aluminum bellcranks, and aluminum arms. The frame is steel, as are the axle clamp. But then again, the stock PHB and brace are as well. And the entire frame, bellcrank, two of the 4 rod-ends and half the arms are all sprung weight. There very very little increase in unsprung mass. And even having said that an entire Watts is less than 30 pounds boxed up. It's more like 27 or so including all the hardware. The stock stuff is around 10 pounds. So yes, there is weight---it's not 50 pounds. It's far from all unsprung, and if you are going to carry it down low and to the rear ain't a bad place.

As for the stresses being up on a single point. That's true. But it's also why a grade 8 bolt 3/4" in diameter is used for the propeller/bellcrank. That way, WAY bigger than any bolt that holds the PHB in place. In fact the Tensile strength of that bolt is over 50,000 PSI.

Yes there were some bolt failures on Saleen watts links, but they were largely due to binding IMHO. The Fays2 bellcrank uses not only one, but TWO sealed bearings to insure the bellcrank does not bind and put any undue stress on the bolt.

I have Watts links on both my Mustang and my Camaro. I wouldn't trade them for PHB now that I have felt the difference. No way, no how. PHB's are nice and cheap but not exactly a perfect design.

100% agreed. If the points cost wasn't so high, I would have one on my Mustang right now. I just thought it would be a good idea to point out both the pluses and minuses when comparing the two systems. The PHB does a decent job, but not as good as a Watts. Period. As for the weight penalty, yes, it's in the perfect place if you're going to take the hit, but that 20lb difference (vs an aftermarket competition PHB) is still 20lbs, and on the fat pigs we drive, trying to find another place to pull that weight off is problematic. IIRC, that's about the entire weight of the air conditioning system...

 

[Sam Strano]

Fair enough, but the AC doesn't help the balance, stability, ride, or predictability of the car... This does. 17x7" wheels are lighter than 18x9.5's, but we'll all take that hit. Saving weight is great, but like anything it's a balancing act.

 

[Sleeper_08]

As my car is used for track days and thus not subject to "points" concerns and I switched to the Fays2 after one season with a PHB. My backside is less tuned than other but to me it made a big difference in how the car felt- especially on quick left to right transistions.

I will say that I do get some rattles and clunks from it on rough roads but am willing to live with them.

 

[irishpwr46]

As for the stresses being up on a single point. That's true. But it's also why a grade 8 bolt 3/4" in diameter is used for the propeller/bellcrank. That way, WAY bigger than any bolt that holds the PHB in place. In fact the Tensile strength of that bolt is over 50,000 PSI.

Yes there were some bolt failures on Saleen watts links, but they were largely due to binding IMHO. The Fays2 bellcrank uses not only one, but TWO sealed bearings to insure the bellcrank does not bind and put any undue stress on the bolt.

not trying to be a smartass or anything but from what i am looking at, the tensile (pulling) strength wouldnt be an issue. from what i see it looks like shearing would be a problem. (though it is very hard to shear a 3/4" bolt, these things do happen). im not trying to put down the system or anything, im just wondering if the way im looking at it is right. the bolt in question is in the middle correct? would this be a problem that tensile strength would be brought into play? im trying to learn about road racing and such and i really just want to know if im looking at this correctly or if im going to be thought an idiot for my questions

 

[Sam Strano]

Maybe someone can find the shear limit on a Grade 8 bolt.... I was simply pointing out the it ain't weak, and in fact is about double what the big 3/4" rod-ends are in that regard.

And let's say anyone had a true reason to be worried. Replace the bolt say, yearly. What can it cost? $10? Small price to pay for peace of mind if you are truly worried about it. Not one of those bolts have broken. And fwiw, that includes a lot of cars that can pull well constant 1.2g + steady state and have broken a lot of other things up and including shearing an axle shaft just outside of the differential.

 

[DusterRT]

not trying to be a smartass or anything but from what i am looking at, the tensile (pulling) strength wouldnt be an issue. from what i see it looks like shearing would be a problem. (though it is very hard to shear a 3/4" bolt, these things do happen). im not trying to put down the system or anything, im just wondering if the way im looking at it is right. the bolt in question is in the middle correct? would this be a problem that tensile strength would be brought into play? im trying to learn about road racing and such and i really just want to know if im looking at this correctly or if im going to be thought an idiot for my questions

No, you're correct. That bolt is loaded in (single) shear, not tensile. Figure it's probably good for 30-40,000# of force though. It would take quite a shock to break it.

IIRC, the Saleen watts setup has a 5/8" bolt in its pivot. After seeing a couple failures it was enough for me to sell the Saleen setup (I found it locally for a steal of a deal but hadn't installed it yet). I'd have a lot more faith in the Fays2 3/4" bolt, and have yet to hear of any failure with those units.

 

[irishpwr46]

Maybe someone can find the shear limit on a Grade 8 bolt.... I was simply pointing out the it ain't weak, and in fact is about double what the big 3/4" rod-ends are in that regard.

And let's say anyone had a true reason to be worried. Replace the bolt say, yearly. What can it cost? $10? Small price to pay for peace of mind if you are truly worried about it. Not one of those bolts have broken. And fwiw, that includes a lot of cars that can pull well constant 1.2g + steady state and have broken a lot of other things up and including shearing an axle shaft just outside of the differential.

1.2g? wow. thats crazy. next summer im hoping to be sufficient enough to get my car to succesfully negotiate a road course and get some sort of decent numbers. hopefully i will get a chance to pick your brain a little more as my education continues

 

[Sam Strano]

What's more.... is there is proof out there in youtube land because we've posted a number of video's with data overlaid that show the lateral and longitudinal forces we make. All you have to do is head over there and type my name in, you'll get lots of video's from this year. There is even a vid clip of me running an SCCA National in the wet (on the dry tires) and getting more than 1g lateral. That car is an f-stock class Shelby GT. Yes, it's on sticky Hoosiers which is a huge part of the grip, but it's also limited. We can't run a Watts on that car (do on other cars just no video of those), and as we move up in class which I'm going for 2010 in my Mustang GT (with a Fays2 link incidentially) we get even more grip because now the tires aren't stuck on only a 8.5" rim, but on 10's. I can do even more things like change springs, change swaybars, change limited slip units, etc to make even more grip.

 

[Pony DNA]

I have Watts links on both my Mustang and my Camaro. I wouldn't trade them for PHB now that I have felt the difference. No way, no how. PHB's are nice and cheap but not exactly a perfect design.

Sam Strano
6x SCCA National Champion
Owner: Strano Performance Parts

Hi Sam,

LOL! I see you have done a 180 with regard to the value of running a Watt's link on your S197 chassis just as I had to do once I drove a car with a Watt' link installed. It was just a matter of time I suppose.

Cheers/Chip

 

[SD07GT]

Hi Sam,

LOL! I see you have done a 180 with regard to the value of running a Watt's link on your S197 chassis just as I had to do once I drove a car with a Watt' link installed. It was just a matter of time I suppose.

Cheers/Chip[/QUOTE

Hey Chip

What do you think of not having an adjustable roll center ? If you had one that was adjustable do you think it would make a difference with your set up ?

Thanks

 

[Pony DNA]

Hi Sam,

LOL! I see you have done a 180 with regard to the value of running a Watt's link on your S197 chassis just as I had to do once I drove a car with a Watt' link installed. It was just a matter of time I suppose.

Cheers/Chip

Hey Chip

What do you think of not having an adjustable roll center ? If you had one that was adjustable do you think it would make a difference with your set up ?

Thanks

Hi SD07GT,

In theory I think I'd prefer to have adjustable roll center height on my Watt's link but I find myself pretty happy with the performance of the Saleen Watt's link in my car which obviously has a fixed RCH. I made an adjustment in rear anti-roll bar size and rear spring rate but it seems to work just fine with the fixed RCH.

If I knew what I know now and Griggs had offered the "quiet" version a couple of years ago I might have been inclined to buy a Griggs Watt's link. Of course that's a lot of "ifs" going on. But in all honesty the fixed RCH is not a problem for me, a mere suspension performance nut.

Cheers/Chip

 

[Sam Strano]

Hi Sam,

LOL! I see you have done a 180 with regard to the value of running a Watt's link on your S197 chassis just as I had to do once I drove a car with a Watt' link installed. It was just a matter of time I suppose.

Cheers/Chip

PHB cars can and do still work.... It's just the Watts links are more predictable. And in fact, early on I didn't love it because I had to sort out the cars around it. I never had an issue with Watts links (well, some I suppose, I think certain designs suck). But in principal I always agreed with how they work. Functionally a poor watts link is worse than a good PHB setup, but all else equal I wouldn't trade the Watts link.

 

[pcdrj]

Maybe someone can find the shear limit on a Grade 8 bolt.... I was simply pointing out the it ain't weak, and in fact is about double what the big 3/4" rod-ends are in that regard.

And let's say anyone had a true reason to be worried. Replace the bolt say, yearly. What can it cost? $10? Small price to pay for peace of mind if you are truly worried about it. Not one of those bolts have broken. And fwiw, that includes a lot of cars that can pull well constant 1.2g + steady state and have broken a lot of other things up and including shearing an axle shaft just outside of the differential.

3/4-16 Grade 8 SAE

Shear - 40200
Tensile - 53408

Binding will greatly reduce the strength of the bolt. Ever twist off the top of a hex bolt? I like the Grigg's Watt's link because is has a small reinforcement plate above the load center to support the bolt. Also, corrosion and disimilar metals can create bind spots very quickly so keeping it lubed is very important.

I helped install one of the first Fays' link in a buddy's car and that thing was heavy. They current design looks much cleaner and lighter.

 

[Kaldar142]

How should you keep rod ends lubed? WD40? Lol