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tomp · Post by **tomp** » Fri Sep 16, 2005 5:31 am

Ive been reading up on suspension preparing to lower front/rear roll centers in conjunction with car lowering. In Tune-to-Win Carroll Smith says to be effective the watts linkage pivot should be mounted on the chassis not the axle and the linkage bars should be parallel with the ground at normal ride height. So, the question is whats the difference between the two arraingments in operation?
-Tom Phillips.

Mats · Post by **Mats** » Fri Sep 16, 2005 5:45 am

Believe it or not, the question is answered in the book.

At least as I recall it..?

tomp · Post by **tomp** » Fri Sep 16, 2005 10:50 am

Really? Must be in a different section. He had a really short chapter on watts linkage. My copy is really really old, maybe he expanded on this on a later version. Do you know about what page I might find that on?
-Tom Phillips.

81GTV6 · Post by **81GTV6** » Fri Sep 16, 2005 5:56 pm

Huh?

Im lost, but this sounds interesting. Anyone wanna attempt to bring me up to speed?

tomp · Post by **tomp** » Fri Sep 16, 2005 7:16 pm

The typical alfa watts linkage has the center pivot mounted to the axle and the radius rods attached to the car chassis. Carroll Smith says this is backwards. The pivot should be mounted to the chassis and the radius rods should attach to the axle. Plus at normal ride height the rods should be parallel. I was tying to get Mats to clue me in on where in the book he explains this in case my old copy dont gots the explanation.

Mats · Post by **Mats** » Fri Sep 16, 2005 8:48 pm

Strange, I'll re-check my copy.

But now I'm off to a friends wedding.

tomp · Post by **tomp** » Sat Oct 01, 2005 2:20 pm

Hey Mats, Did your copy of Tune-to-Win explain why the linkage arms should be connected to the axle and pivot mounted to frame?
-Tom P.

Mats · Post by **Mats** » Sat Oct 01, 2005 2:22 pm

Mine says the same as yours

tomp · Post by **tomp** » Sun Oct 02, 2005 3:34 am

Ok, thanks. saved me from buying a new copy.

MALDI · Post by **MALDI** » Sun Oct 02, 2005 2:15 pm

To hazard a guess, I'd say it has to do with stress on the frame. With the links connected to the frame on opposite sides of the car they could potentially give long moment arms to twist the frame when lateral loads are applied (i.e. cornering). With the center point connected to the frame these moment arms are reduced to zero and the lateral loads are concentrated on the centerline.

This link has some nice images of the two styles at work (scroll down to the bottom):

http://www.miracerros.com/mustang/t_suspension.htm

Mats · Post by **Mats** » Mon Oct 03, 2005 12:08 am

I would guess it has absolutely nothing to do with stress and all about the fact that you would get a roll center that is moving with the body of the car instead of one that is fixed in height (to the ground).

MALDI · Post by **MALDI** » Mon Oct 03, 2005 3:45 am

Mats you certainly deserve your title of "Guru!".

From a web site that sells Watts links for Mustangs:

"With a body mounted Watts Link System, the crank is mounted to the subframe / cradle which allows the crank centerline / rear roll center to move with the suspension resulting in a more consistent rear roll couple. When the crank is mounted to the rear differential cover, the rear roll center is essentially fixed and the rear roll couple changes with suspension travel."

http://www.raceindustry.com/productshow ... y_id=11583

Now is there any difference for a de Dion versus a solid rear axle? I would guess not.

Mats · Post by **Mats** » Mon Oct 03, 2005 11:40 am

Not one. Not in this perspective anyway.

tomp · Post by **tomp** » Thu Oct 06, 2005 4:04 pm

Yeah, seem obvious now. Very interesting to imagine the roll center rising and dropping with the chassis rather than the axle. Thanks for the link Mats!
Tom P.

Mats · Post by **Mats** » Fri Oct 07, 2005 9:34 am

Thank MALDI, he's the link guy.

watts linkage reversed?