More precisely, somewhere along the line it got setup to run oval track, would turn left great, wouldn't go right very well. I don't think he's figured out the problem, yet.

An interesting note from this weekend, a local guy with a nice DSP E30 was doing fun runs with us and managed to spank Sam and I by three tenths raw time. Not bad for a grocery getter. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/nutkick.gif)

I've definitely not given up on trying a roll center change. With the extra throttle sensitivity of my car and more engine braking vs. an LS1 car I think it might be an interesting experiment.

Just for the record, can you sell the Hotchkiss rear bar separately now, or is there another hollow 25? I don't see the Hotchkiss or Addco bars listed; only the Strano bars.

I already reinstalled my old Hotchkiss bar, since the Hellwig adjustable bar doesn't clear the Watts bellcrank.

This post has been edited by sgarnett: Oct 7 2008, 04:28 AM

Sam sells Addco's hollow 25mm bar. I bought one from him and made it adjustable with sliding end links.

No, I do not think it is desirable. At least not at the height I was lifting mine. It would reliably do it in only the fastest wide open flat out sweepers... which was 6000 rpms and second gear in my car.

It illustrates a point though. As you lower the pinion more weight transfers to the rear and specifically the outside rear while cornering.

Sam said he won't want to change his suspension around and I assume that means sway bars. He does know what he wants out of his car.

So, the lesson is that this Watts Link this may not be what everyone wants. Or needs. I think the valid point of reducing jacking effect is a meaningful advancement. However, 650+ dollars to just reduce something live axle cars have been dealing with for decades is a ton of money in comparison to the benefit. With the recent probable rule changes upper control arms could be a bigger advancement. I am sure there is someone that posts on this forum that will sell you a nice set.... If only I could remember that guys name..... I am sure he has a web site.... nope. I got nothin.



As for lifting the inside front tires. I think other changes will need to be made to compensate for this. (Yes, I used "compensate" on purpose.) This goes back to my previous point of this may not be want you want to do. I suspect for most having a 1/2" adjustment in roll center with NO other changes can get the car more neutral or more where the driver wants the feel of the car. (Again this is expensive for just that little thing.)

I do have a plan on the compensating control for the tire lifting. I'll report the results. In the meantime they are evil secret plans, eyes only and stuff like that. I might just be going the wrong way anyway.

(oooh, you know what. I think I just contributed something useful.)

No, you've got it backwards. Lowering the Watts pivot reduces lateral weight transfer to the outside rear while cornering. That's why a bigger rear bar is required, and why I think your rear bar is still too small for your current setting (or, your pivot height is still too low for your current bar). If you are lifting your inside front, you are getting 100% lateral weight transfer at that end.

Also, assuming you didn't change the ride (CG) height or anti-squat geometry, if you are transferring more weight to the rear, it is and can only be because you are accelerating harder. With the roll center lowered, combined with a bar that is probably still too small, you were probably able to use more throttle without losing the tail, though I suspect it was pushing a little.

From a lateral weight transfer perspective, if the inside front is lightly loaded, then so is the outside rear and vice-versa.

This post has been edited by sgarnett: Oct 7 2008, 02:04 PM

Ah, yes. Thank you for correcting me, Sean.

It certainly did not feel like it was pushing. At the Test and Tune on Saturday I kept lowering the pinion until the push went away.

And yes. I did have boat loads more throttle at corner exit.

In other words, you kept increasing the push until the push went away.... There's a piece missing from this puzzle.

Got pics? Did you weld on a slot, or make a slider that clamps around the tube? Is the Addco bar CM (with associated welding issues)?

The piece might be slamming into the bump stops.

Cut the eyes off the ends of the bar and welded on a square tube with a slot machined in it. I had to make some brackets that bolt onto the body to use rod ended links. I'll try to remember to take some pics when I get home, it's sitting in my "car room" because I didn't like the lowered roll center.

Ah! Now that makes sense!!! With all else unchanged, lowering the rear roll center reduces rear lateral weight transfer (which will also help hook up the rear under power) but it will increase the roll. That's why a bigger rear bar is needed (and possibly spring and shock changes if the roll center is dropped a lot).

Remember, roll and weight transfer are not the same thing. You can have a lot of roll with little weight transfer and vice-versa.

Once the car lifts the inside front enough to park the outside rear on the stop, it will stop pushing, but not in a good way (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif) Until you hit that outside rear stop, there's lot's of roll (and camber loss at the front) but little weight transfer. When you hit the stop and the rate spikes, weight transfers suddenly to the outside rear even though there will be little additional roll.

That's not in any way an indictment of the Watts link.

It's also not an indictment of lowering the roll center, though the required swaybar/spring changes are at the heart of Sam's objection to it, and of course some may not like it. I also haven't tried it nearly as low as some, might not like it, and may never try it. Some is good doesn't always mean that more is better.

Brian, I'd suggest either buying the hollow Addco 25mm bar (that would be my choice), OR raise the pivot until the push comes back, and then keep raising it until the push goes away again (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif)

This post has been edited by sgarnett: Oct 7 2008, 04:22 PM

Wanna sell it?

Ha, no... no bump stop slamming.

I went from an extended 19mm rear swaybar (think 17 or 18mm at most) to a 22mm solid bar.

--> I miss spoke before. (Sorry, hangover issue)

I lowered the pinion on until the looseness went away and the car got [to what I call] neutral.

Not until I do the same thing to one of Sam's 22 bars.

My car doesn't have a watts or any other mechanism for changing RC on it, at least not right now it doesn't.

Once I took one run in John's car I went out on the 2nd one and literally tried to make the thing transition as fast as possible and mostly the rear just stuck which was nice. I bet the rear letting go had more to do with some bumps in a very fast slalom/lane change than with any inherent issue with the RC change. The mid-corner push had everything to do with the RC height change, though. I'd be more incline to compensate for the RC change with spring vs. bar because I'm already torching my T2R coming out of slow right-handers.

But, I'm still not sure I'm gonna mess with it yet anyway on my car.

The Hotchkis has always been available separately for the rear--it's the front one that's not. And I don't have either on my website, I just can't possibly keep up with every single thing out there, and try and concentrate on parts that work best for the masses.

I have both bars, and I *BEG* you guys to ask me about things you don't see on the website. I might not be able to help, but chances are I can.

I have it narrowed down to two things... The trouble is finding the time to work on it and then running it to shake it down, not tracking down the problem... (IMG:http://www.frrax.com/rrforum/style_emoticons/default/sad.gif)

Here's a question specifically for those who have tested and at adjusted the Watts on race tires with no other changes:

To get the car back to "balanced", where did the pivot end up relative the center of the PHR that was removed?

The RC height moves around in roll with the PHR, as well as the distance from the roll center to the CG. That also changes a little in trail braking, by about half as much as the tail rises, but of course it changes a lot more as the turn-in is initiated. So, the balance isn't static, and to some extent we choose the swaybar (and etc) so that the car is manageable at worst case.

The RC height shouldn't move much in roll with the Watts. The roll center height will actually change a little more in trail braking, but the distance from the roll center to the CG will NOT. It also shouldn't change as the turn-in is initiated.

In other words, I wouldn't expect the Watts and PHR to behave exactly the same with equal static rear roll center height. That's kind of the point (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif) So, I wouldn't be surprised if the Watts pivot needs to be a little higher to achieve approximately the same average balance or feel. That seems to be consistent with the descriptions of dialing in John's car above, but I don't know where it started or how much it had to move.

Again, I'm specifically interested in how the RC height had to change (if any), relative to where it was before, without any other changes (ignoring things like wheel bearings, of course).

I'm only going to get one testing opportunity this year on a semi-decent surface, and there won't be any opportunity for tuning until next year. I missed several testing opportunities because of my wife's major surgery, our last great-surface event was canceled due to a garbage truck rodeo (seriously) failing to clean up the site on time, and what's left will be on a small, slick site that's too misleading for testing.

This post has been edited by sgarnett: Oct 9 2008, 02:55 PM