Roll Center, Roll Couple, Roll Axis, How to lower Efficiently?

[low_psi]

Non-competition based setup= Good alignment, OEM Racing Beat swaybars, Tokico struts and good linear springs of decent spring rates that don't drop the car too low.

There's a fun and rewarding package that most people will enjoy.

If you want to get more into it... find adjustable components and adjust everything from the sway bar endlinks to track width.

 

[xelderx]

Non-competition based setup= Good alignment, OEM Racing Beat swaybars, Tokico struts and good linear springs of decent spring rates that don't drop the car too low.

There's a fun and rewarding package that most people will enjoy.

If you want to get more into it... find adjustable components and adjust everything from the sway bar endlinks to track width.

This is the right direction to go in.

Before trying to adjust a bunch of things or move things to improve performance, replace parts with higher end components. Stock Protege struts are extremely basic and made for comfort. Replace them with something more perfomance oriented. Springs and swaybars are the same way. Once you get the replaceable components upgraded you will have a better platform to build on if you chose to go farther. This will also help you in getting a feel for how the different suspension components affect the handling of the car so that you can make better choices if you feel that a certain area needs something different. There is no master plan that works for every car and driver. Somethings you will just have to experiment with and see if it fits what you want.

 

[122 Vega]

I'm not a girl, that's a picture of my wife.

Britt

im a suspension noob in terms of modifying suspension but what about wider tires? would that maximize cornering grip, Some stx girl on the forum said less rotational mass is what makes handling better

 

[122 Vega]

Excellent advice from xelderx. Do one thing at a time so you can notice what everychange makes. It's funny at an autocross when guys will make one run then come back and make several changes to thier double adjustable shocks then after every other single run. How do you know what works? At a track Day, if you make an adjustment, like at PIR, I will run at least three laps (1.93 miles each) before I decide if it helped or hindered me.

Britt

 

[Felipe340]

Ok low psi, heres the updated picture I promised. Hopefully this will begin to clear up why this seems like an issue worthy of discussion.

 

[low_psi]

Your picture only shows the lowered position of the lower control arm, you also have to lower the upper strut mounting point. The new CG will also be lower.

Refer to my drawing on Page1 and you'll see the roll couple doesn't always increase when lowering. The CG will drop almost the same as the ride height since the majority of the vehicle mass is sprung.

 

[Felipe340]

In my picture the ground is raised on the right side along with the tires and the struts are compressed (the black lines on the bottom are the ground), thus demonstrating the lowering of the vehicle. Since the ground is raised, strut mounting point height and CG remain the same, even though they and everything else are actually closer to the ground. I thought this would better demonstrate differences by keeping relative points based on height in the same positions visually, sort of like constants.

 

[low_psi]

The ground is the best constant IMO The CG and RC are the only points of interest really. Anyways, our graphs don't mean a whole lot since they aren't contructed using the geometry of our cars.

What's important is figuring out exactly how much the RC moves in relation to the CG of our car and how much changes in their relationship mean. A lower CG means lower total weight transfer, a lower RC & IC means lower jacking forces, stiffer springs increase the roll stiffness... seems like quite a few good things.

I doubt a larger roll couple is going to adversely affect the car's performance more than running out of strut travel. By the time you've run out of strut travel you're probably on the wrong end of the camber and bumpsteer curves because the car is soo low. There are bigger issues to deal with than the roll couple IMO.

 

[dmitrik4]

Non-competition based setup= Good alignment, OEM Racing Beat swaybars, Tokico struts and good linear springs of decent spring rates that don't drop the car too low.

along these lines, something else to keep in mind is that a fun street/curvy road ride doesn't necessarily equal a good autoX car, and vice versa.

as xelderx mentioned, just upgrading the OE components will likely pay more on-public-road dividends than anyone will use 99.9% of the time. i am really enjoying this thread so far, as it's something that a serious autoXer will want/need to know, but it is a bit of overkill when discussing street setups.

anywho...who's going to be the first to crawl under their Pro with a tape measure and a ruler?

 

[aMaff]

anywho...who's going to be the first to crawl under their Pro with a tape measure and a ruler?

well, I'm in Mass. and ol' blue's in GA, so...NOT IT!

 

[low_psi]

haha, I already measured the front. just need to put it into Mitchell and see how things work out.

 

[Felipe340]

Sorry, been busy lately updating a database for an office in my spare time. I mean ALL of my spare time. Anyway, when I get a little time I'll try to do the measurements of a bone stock car. The only thing is measuring the CG takes a lot more than a ruler and a level, like individual tire scales and such, so those numbers would just have to be assumed to be higher than the RC. The assumption on this would also have to be that it is adjusted at the same rate the ride height is, so what are the most common lowering numbers for the most common springs? Calculation of changes would rely on these numbers.

 

[low_psi]

check the link in my sig for spring info.

 

[low_psi]

Well I measured the front MR, but the numbers didn't work out properly. I don't see it being less than 0.90 though.

I need to measure the rear too... probably around 0.75-0.8

I'll get to this one day when I can pull the springs off and use plumb bobs

 

[low_psi]

Bump, anyone else get around to this?

I've come up with:
Front MR= 0.95
Rear MR= 0.85

 

[FunkRider]

Bump

Did anyone ever get numbers?

Right now I'm trying to figure out why Mazda adjusted the roll centers for 2001+ 24mm lower in front, 21mm higher in the rear vs the 99/00 cars.