Improving handling on a P5

[Monstermile]

I am good with describing what is wrong, or not the way I would like, but not too good with putting a type of handling description with it (understeer, oversteer, bodyroll, etc). The thing I notice with the P5 is when in a slalom type situation, the rear doesn't seem like it wants to keep up with the front. So if I cut hard right, the rear doesn't feel like it is keeping up. It is not losing traction, but it just feels wishy-washy. I would like that when in that situation that the rear is right there when cutting left to right.

What is my first course of action to achieve this feel. It seems like with the P5 that the rear is the culprit for alot of bad handling characteristics IMO. Also noticed in sharper turns that the rear just seems to never be there as well.

When I had my Focus with Eibach springs and dampers I could take turns and slalom with confidence that the end wouldn't come out and I never had to let off the gas. I wanna be able to do the same with the P5.

Do I need to start with a rear sway bar, or is the only way to improve this is with upgraded springs and dampers as well as sway bar??

 

[jmauld]

I'm not positive about what you're trying to describe. Does it feel like the rear end is coming around with you in a slalom? If so, here's something for you to try. On your next run, be a little gentler on the steering inputs and as soon as you feel the backend sliding, ease into the throttle. The result may surprise you.

Whatever you do, don't lift if it feels like the back end is coming around. Unless you like spinning.

 

[flat_black]

Spinning is fun! =) Hehee.

To be honest, the P5 will benefit from a larger rear sway bar, and the tail end will follow nicely, but the tabs on the stock struts aren't really that beefy, so there's a chance that you'll snap the tab right off, which is a Bad Thing (tm). I would suggest to you getting MP3/Mazdaspeed struts and Racing Beat coilovers (The RB's mostly because they're matched to the MSP/MP3 and only drop it a little, while increasing the spring rate). Then drive it around a bit, and see if it behaves well within your expectations. If the rear still is latent in coming around to follow your front wheels, try a stiffer rear sway from AWR, 19mm and 21.5mm are your options. =) Good luck!

 

[mp5]

Ill do my best to describe what happens to the rear end as cornering gs increase. On a typical car as cornering gs increase the tires contact patch actual is traveling in a different path then the rim due to flexing in the tires side wall. To try to explain this in words, if you are traveling slow and you turn your wheel 10 degrees, the rim turns 10 degrees along with your tires contact patch. As speed increases, and you turn your wheel 10 degrees, your rim still turns 10 degrees but your tires contact patch might only turn 9 degrees due to the deflection in the side wall of a tire. And as speed increases further, you might only get 8 degrees at the tires contact patch for the same 10 degree turn of your wheel. So when you take a turn at high gs the rear rim follows the direction of the car, but due to the deflection in the side wall of the tire, the tire is pointed away from the direction of the turn (if you are making a right, the rear contact patch is actually traveling to the left). This adds to a cars tendency to over-rotate in a turn.


On the Protge line, Mazda uses a multi-link suspension on the rear that changes the toe as cornering loads increase. This causes the rim to actual turn in towards the direction of the turn a few degrees so that the tires contact patch follows the intended path of the turn (no longer does the rear contact patch point in the opposite direction of the turn). This change in toe is in proportional to the lateral load on the suspension. This is done to reduce the tendency to over-rotate in a turn and try to keep the car balanced at the limit.


This is what is causing the sensation that you describe as the rear not keeping up. As you transition from one the direction to another as in a slalom course, the rear goes from increased toe in one direction, to normal toe, to increased toe in the opposite direction. Another words, if you take a hard right, then switch to hard left, the rear goes from steering right, to going straight, to steering left in order to always keep the tires contact patch in the intended direction of travel (which is straight). This helps keep the cars handling at the limit balanced and predictable. The sensation you feel is the rear ends lack of change in direction of travel compared to what you feel in other cars(most cars rear contact patches go from turning left to straight to turning right in the example above).

But to answer your question, springs and dampers will go a lot further in improving handling than a rear sway bar but both will help.

 

[mp5]

One option you might want to try is running a higher tire pressure in the front then in the rear. This will allow the rear tire's side wall to deflect more and somewhat negate the effect of the Pro's rear suspension design. This will provide a handling experience more like what you are acustomed to but will lower the handling limit somewhat.

 

[blynzoo]

To kind of paraphrase what mp5 said, you are used to the back end swinging out more. It feels like it is not following because in most cars that do not accomodate with toe changes the rear will run "straighter" (at less of a turn angle) than the front wheels. Having said that, the p5's rear is actually more exact (but not perfect) in tracking.

To take it to the extreme (and goofy), imagine if every time you turned your car locked the back wheels and you did an e-brake style slide. If you ever drove a car that did not do this, it would feel like the rear was not "following" as it should, like just the front of the car was moving and the back was sitting still.

BTW, mp5 that was a fantastic explanation. Good job.
And yes, I know several folks here who are running 32/29 psi F/R.

 

[Monstermile]

WOW!!! Excellent feedback and great explanations. Very impressive. Guess there is more to the Pro suspension then I realized. I think I'm prolly gonna go with my original path and try new springs first to see if that gives me closer to the results I'm looking for. Most likely MP3 or RB springs. If that doesn't cut it new dampers will be in order.

Thanks for the input.

 

[PaulMP3]

i will have my mp3 springs for sale soon. Keep an eye on the 4sale page. They have been in my garage for 6 months now.