RX7 Handling Issue

[rx761]

Just wanting to get some help on what people might think the problem is before I start going through a list of things. Last race out I developed a weird feeling in the left rear of the car. It only happens on right hand turns, when the car is leaning on the left side tires. It seems to be rolling way to much in the left rear. When I was driving around the paddock I wiggled the car back and forth, and it felt as if the rear body of the car was sliding back and forth on the axle. It actually feels like I am driving with a left rear tire going down. I checked the rear wheel bearings and they were fine, tires are fine. I pushed down on the left rear of the car but the bounce did not seem any different than normal. Does this sound like a bad spring or shock? Anything else in the axle beside a bearing? Just looking for some hints as to what to look for or where to start looking. Thanks

[dickita15]

Is it a stock rear suspension? Does it still have a watts link or has it been changed to a panhard rod?

[rx761]

No it is not stock. I have Tokico adjustable shocks. Eibach springs and Watts link.

[TomL]

From your description of everything seeming okay except that the body moves relative the axle, it's most likely a problem with the watts link. If it's an aftermarket, adjustable watts link setup, I'd look very carefully at the center pivot. I've seen more than one of those that cracked or even broke off. The car will then feel very sloppy. Other possibilities include decaying rubber bushings (stock watts) or damaged rod end (aftermarket). I've also seen the upper watts bracket on the chassis fatigue and break.

Look on the bright side, though. I had a buddy run almost an entire enduro, 75 minutes worth, with the center watts pivot broken off completely. And he almost won. So it's not THAT big a problem.

[Dano77]

My car tore the bracket from the chassis on the right hand side and it didnt feel too wierd till the arm started dragging onthe track and the car filled with tire smoke.

Coluld also be a bad shock,or a spring that is falling off the axle and binding up on the left side.

Sounds very odd though,let us know what happened

[rx761]

Yeah the car does have the stock watts link, so I will start there. Thanks guys.

[joeracerx95]

From your description of everything seeming okay except that the body moves relative the axle, it's most likely a problem with the watts link. If it's an aftermarket, adjustable watts link setup, I'd look very carefully at the center pivot. I've seen more than one of those that cracked or even broke off. The car will then feel very sloppy. Other possibilities include decaying rubber bushings (stock watts) or damaged rod end (aftermarket). I've also seen the upper watts bracket on the chassis fatigue and break.

Look on the bright side, though. I had a buddy run almost an entire enduro, 75 minutes worth, with the center watts pivot broken off completely. And he almost won. So it's not THAT big a problem.

Once the center pin on the Watts link shears off there is zero lateral control of the axle (ask me how I know).

When this happens the only side to side control on the axle is when the tire hits the inside of the wheel well or the driveshaft hits the side of the center tunnel. Measured in inches this is a good 10" side to side movement. This is not a small problem, it basically makes the car undrivable and eventually will result in one of the tires failing due to the wear on the sidewall or the driveshaft failing. The good news is that the blinding smoke that pours off the back of the car will do a good job of keeping your competitors behind you, while it lasts.

If this was your problem, you would know it. But as others have said, any one of the bushings in the Watts links or the trailing arms could cause issues. Since it's a problem turning one way but not the other I would check the trailing arms on the left side first.

[TomL]

I was joking about it not being a problem, obviously. But the story about my friend running 75 minutes with no lateral axle control is true. With wide tires, the side to side motion is limited by the tires hitting the inner fenders and is only 2 or 3 inches each way. Squirrelly, but not undriveable. I've done it, too. I broke the chassis bracket on my panhard bar completely off (like, dragging on the ground) half way through a race one time and had the same experience - it slowed me down by a second or two a lap, but I was able to maintain my second place to the end.

[G-Man]

I'll echo "check the Watts linkage." I just found the top stud on the center bracket snapped. Not sure how, but it must be a garage injury. Bad jacking? Just time?

[joeracerx95]

I'll echo "check the Watts linkage." I just found the top stud on the center bracket snapped. Not sure how, but it must be a garage injury. Bad jacking? Just time?

When the car is lowered the Watts link moves into a position that puts in under constant twisting stress. Eventually the top, bottom or center pin is going to become fatigued and will fail. That why some people change the fasteners to Nylock nuts and then don't fully tighen them. Mazdatrix makes a part that removes the stress on the top and bottom pins. http://www.mazdatrix.com/getprice.asp?partnum=MZ-1-WATT

Unfortunately there isn't any cure for the stress on the center pin. My feeling is that it is better to let the top or bottom pin be the one to fail because if the center pin fails you are screwed. The piece that holds the top and bottom pin is easily replaced. Without a jig, there is no way to accurately align and reattach the center pin to the axle housing. The correct solution is to replace the entire axle housing. Because of this, when the center pin on my car broke, I used that as an excuse to change to a Panhard rod. Just my opinion and experience.

[Matt93SE]

When the car is lowered the Watts link moves into a position that puts in under constant twisting stress. Eventually the top, bottom or center pin is going to become fatigued and will fail...
...Without a jig, there is no way to accurately align and reattach the center pin to the axle housing.

any chance the center pin could be realigned to have less stress when welding back into place?
zero experience with RX7s here, just curious if that's possible so it can be fixed on the cheap..

[joeracerx95]

any chance the center pin could be realigned to have less stress when welding back into place?
zero experience with RX7s here, just curious if that's possible so it can be fixed on the cheap..

I was just thinking about that yesterday because of this discussion taking place. This is pure guesswork but maybe if you took the detached pin and while it was inserted into the link bracket while the car was at the resting ride-height, that might be the most stress free angle for it to be at. That would make the bracket your jig. I have no idea if you could even get in there with a welder at that point.

Unfortunately the design of the whole rear end is just flawed for a race car, too much binding occurs no matter what you do if you are using the stock parts.

[rx761]

Turns out the problem was worn out bushings in the watts link, as well as in the upper & lower control arms.