Making the 2 Handle Power

[JamesCH]

The weight transfer is basically necessary for cornering. The more cornering force, the more weight transfer there is going to be. Basically the weight transfer from one side to the other counter acts the roll created. There are things which you can do to lower the amount of weight transfer for a given cornering force, but springs and sway bars make no difference.

To pit it simply, if you picture a car just sitting there not moving. Now imagine the ground pushing from left to right on the bottom of the tires. This will cause the car to roll around the CG. That force is applied at the ground and the CG is above the ground. This will give an overall torque to the chassis. As everyone knows every force has an equal and opposite force. Well the opposite force to the car rolling is the weight transfer on the tires. The left tires will have more load than the right. This difference in the load causes the equal and opposite torque on the chassis through the CG.

The higher the side load (cornering) on the tires the more weight transfer is required to oppose it. Also from this the springs and sway bars have nothing to do with the weight transfer of the car. They will effect how much roll the car will see, but now the loading.

So it isn't really a matter of the weight transfer being beneficial, it is just necessary. Not sure if that answers your question.

If I understand you correctly, you're trying to say that ultimate grip is sometimes sacrificed for better handling balance, which results in a faster car. Springs/bars balance the front and rear axle's grip by making one axle transfer more weight than the other, but they do not change the total amount of weight transfer for the whole car.

Edit: what doesn't make sense is your statement " for a particular car you need a certain amount of weight transfer to achieve the maximum cornering for the tires" when, in fact, less weight transfer is better provided that the balance of the car isn't upset.

 

[zps2004]

To the first part yes.

To add some more confusion onto this a little further I am going to give another example. If you are familiar with corner weighing a car, you know that the weight on the front left is linked to the rear right, and the front right to the rear left. If you have adjustable ride height suspension and you go to corner weigh your car, if the front right is really heavy then your rear left will be heavy as well. This is the same as when a car is in a corner. If you add a stiffer front sway bar in the front of the car, there will be more weight transfer on the front axle. So on a right turn, the front left will be loaded more, and the front right will be loaded less. For the front, as we have agreed on, there will be less traction. Since the front left is loaded more the rear right will be loaded more than before, and the left rear less than before. So the rear of the car will have more grip than before since there is less weight transfer.

I think your are reading my one statement incorrectly which is why you are confused. When I talked about there being a certain amount of weight transfer for maximum grip for the tires I meant that with respect to the second statement, springs and sway bars play no roll. If you lower the CG or make the track width wider, then you will have less weight transfer for the same maximum grip of the tire, but the springs and roll bars play no roll in the overall amount of weight transfer for a certain amount of grip/cornering force.

 

[Joker2]

To the first part yes.

...play no roll. If you lower the CG or make the track width wider, then you will have less weight transfer for the same maximum grip of the tire, but the springs and roll bars play no roll in the overall amount of weight transfer for a certain amount of grip/cornering force.

... or role or pun intended (confused).

And yes you are correct, dampers play a role but springs and ARBs do not (nearly as much)...Which is why Autocrossers run obscene amounts of compression damping (in high grip concrete events anyway) as they need to control the very quick transitions in slaloms or turn-ins. Road-racers need less. speed and surface irregularities of-course factor in (rate-wise).

Furthermore, ultra high performance summer tires like my RE-11s or AD08s have stiffer sidewalls to further increase the spring rate per corner, further increasing the response rate to steering inputs. Quicker transitions result from higher spring rates, almost independent of ride height, assuming similar roll-couples. Does damper tuning control the rate change in roll! Sure it does. What about spring rates? It seems that some higher end applications run very high spring rates over 1,000 lbs per inch and then use an ARB to tune instead of to control roll rate.

For reality check, note that E-Stock Miatas and C-stock RX-8s perform slightly better than street touring classes. R-compounds in stock vs. the tires I mentioned, as evidenced by their high PAX. So lowering a Miata or RX-8, changing springs and dampers and roll bars does not seem to overpower stock springs, good dampers and r-comps. Hmmmmm... let's think about this and re-read the posts above as there is a bit of science at work here.

 

[JamesCH]

ZPS: we are in violent agreement. Total weight transfer is a function of track, CG height, mass, and acceleration only. Individual axle weight transfer (aka handling balance) is a function of their relative roll stiffness.

Speaking of track, to help the Mazda2 handle the extra power I would run wider tires in the front with more offset. 10-20mm wider tires and I'd aim for 5-10mm more offset on each wheel. Just to rectal pluck some numbers.

Here's something to think about: does adding weight down low (i.e. bolting weights to the bottom of your car) to lower the CG, increase or decrease weight transfer?

It hurts weight transfer, the moment arm of the CG is reduced less than the force exerted on that moment arm increases, netting a larger amount of weight transfer.

 

[zps2004]

What about spring rates? It seems that some higher end applications run very high spring rates over 1,000 lbs per inch and then use an ARB to tune instead of to control roll rate.

For reality check, note that E-Stock Miatas and C-stock RX-8s perform slightly better than street touring classes. R-compounds in stock vs. the tires I mentioned, as evidenced by their high PAX. So lowering a Miata or RX-8, changing springs and dampers and roll bars does not seem to overpower stock springs, good dampers and r-comps. Hmmmmm... let's think about this and re-read the posts above as there is a bit of science at work here.

You can run high spring rates, you mainly just need to have the dampening to control them. High rates are very much necessary when you start making some good downforce. Otherwise it is difficult to tune the handling because the suspension will be very different due to the change in ride height.

Also it has been proven many times that over a 1 minute autocross R-comps will be about 1.8-2 seconds faster than one of the good street tires. That much more grip will outweigh a tuned suspension pretty easily.

 

[zps2004]

ZPS: we are in violent agreement. Total weight transfer is a function of track, CG height, mass, and acceleration only. Individual axle weight transfer (aka handling balance) is a function of their relative roll stiffness.

Speaking of track, to help the Mazda2 handle the extra power I would run wider tires in the front with more offset. 10-20mm wider tires and I'd aim for 5-10mm more offset on each wheel. Just to rectal pluck some numbers.

Here's something to think about: does adding weight down low (i.e. bolting weights to the bottom of your car) to lower the CG, increase or decrease weight transfer?

It hurts weight transfer, the moment arm of the CG is reduced less than the force exerted on that moment arm increases, netting a larger amount of weight transfer.

It isn't an argument, it is a discussion.

Thinking it over in my head the individual weight transfer for each axle I believe is not a function of their roll stiffness. Here is why. In my Miata lets say I can hit 1G on my RE-11'son a skidpad, there will be a certain amount of weight transfer for the front and the rear to accomplish this. No argument there. Now lets say I put in stiffer sway bars and springs such that my roll stiffness in the front is twice as much and in the rear it is twice as much. No other changes in track, or height. Assuming that around the skidpad that the camber is the same as it was before (i know it won't be due to less roll), I will still be able to pull 1G on the skidpad, and the overall weight transfer will be the same.

To look at it in a different way. Take my Miata again making 1G on the skidpad. If add spacers lets say 2" for each wheel. When I get to 1G on the skid pad there will be less weight transfer on both axles with the wider track, but the roll stiffness will be the same.

Here is some good info on it I found.

http://www.gencoupe.com/articles-ch...ess-weight-transfer-what-you-should-know.html


Now adding weight to the bottom of the car should decrease weight transfer because of the lower CG height, but it is completely not worth it unless you have a minimum weight to reach for your class. The CG will be lower, but the overall weight of the car will be higher so it is more mass to move. Plus the additional load on the tires will cause them to be less efficient overall from the load VS Grip plot. Less weight is always a good thing, unless you have a class minimum weight.

 

[JamesCH]

It isn't an argument, it is a discussion.

Thinking it over in my head the individual weight transfer for each axle I believe is not a function of their roll stiffness. Here is why. In my Miata lets say I can hit 1G on my RE-11'son a skidpad, there will be a certain amount of weight transfer for the front and the rear to accomplish this. No argument there. Now lets say I put in stiffer sway bars and springs such that my roll stiffness in the front is twice as much and in the rear it is twice as much. No other changes in track, or height. Assuming that around the skidpad that the camber is the same as it was before (i know it won't be due to less roll), I will still be able to pull 1G on the skidpad, and the overall weight transfer will be the same.

To look at it in a different way. Take my Miata again making 1G on the skidpad. If add spacers lets say 2" for each wheel. When I get to 1G on the skid pad there will be less weight transfer on both axles with the wider track, but the roll stiffness will be the same.

Here is some good info on it I found.

http://www.gencoupe.com/articles-ch...ess-weight-transfer-what-you-should-know.html


Now adding weight to the bottom of the car should decrease weight transfer because of the lower CG height, but it is completely not worth it unless you have a minimum weight to reach for your class. The CG will be lower, but the overall weight of the car will be higher so it is more mass to move. Plus the additional load on the tires will cause them to be less efficient overall from the load VS Grip plot. Less weight is always a good thing, unless you have a class minimum weight.

Two things:

Read this article: http://www.neohio-scca.org/comp_clinic/hand_out_reprints/LoadTransfer reduced 2.pdf specifically the example on page 5, and the think about the statement I highlighted. Same total weight transfer, balanced differently between two axles, results in different cornering abilities.

Adding weight, even if it lowers the CG, will INCREASE weight transfer. Check out the white text in my post. I've done the math.

 

[A-sher]

I didn't spend the time reading through this, Neither do I know anything about the 2's brakes, but looking into swapping over the brakes from other models might be beneficial. I know for the 3 you can swap ms3 brakes to the front and the 5's brakes to the back as up upgrades. So maybe the 3's brakes will swap on. Sorry I'm fairly knowledgable on the older models but I haven't really looked into the 2's yet, just some thought though.

 

[Chris_uk]

ok so ive read through this and feeling very confused now haha bit to in depth for me, so on a basic level, will dropping my MZ2 sport 2007 UK model with the Eibach or whatever springs, say by 30mm or maybe 40mm be ok and not wear my shocks out, ive seen that people say anymore than 30mm and it wears them out quicker, is this true?

 

[Slow Paul]

Whew, what a read. I'm happy all this in-depth discussion is going on in out little section of M247. I'm learning a lot, so keep it up. My .02, I have sticky Kumho XS and Konig Britelites and the braking characteristics of my M2 have improved quite a bit. In addition, I have added the CorkSport torsion bar, and that too has made a pretty noticeable difference in the goings-on in the rear. My next step is struts/shock, but I too am waiting for Koni to bring some to market.

 

[Chris_uk]

anyone want to maybe help me out? last thing i want to do is go in blind lol

 

[JamesCH]

Stock shocks aren't usually up to the task of controlling properly designed drop springs (read: stiffer springs) the more you drop, the stiffer they should be. If the general consensus is "don't go lower than 30mm" I would believe it. Also, as discussed, dropping the car could result in increased roll. Personally, I think 20-25mm would be plenty of drop, but whatever suits your taste.

 

[Joker2]

Here I go again:

The linked posts gloss over the physics involved, thereby allowing the reader to infer that by understanding those articles, he/she is in possession of the knowledge base required to fully understand what is required to achieve a proper set-up.

What is a proper set-up?

First one has to define the "Mission Profile" in airplane design speak. This means, what specifically one is trying to achieve? The mistake most tuners (amateurs and pros alike) make is that they are quite vague in their profile eg: I want a car that is decent daily driver and does well at the occasional track day or autocross. This is poor mission profile as the expectations are opposed in scope: comfort and balance in DD and very focused handling requirements/characteristics in track or autocross. What about handling on the edges of the "flight envelope"? How does the car handle snow or wet track days? Is it easy to adjust for those conditions, or does one need a NASCAR trailer full of springs and dampers to match the course and climate conditions?

To the original poster, what are the demands (chassis-wise/suspension-wise) that require attention with a higher horsepower set-up? Is the concern that by accelerating quicker we need to improve braking ability, or chassis control, and how? Besides vague statements like: my Spec Miata does this or that, what exactly does one need to fix on the 2? If one can define the shortcomings (backed up by data acquisition and analysis) the one can focus on goals (discussed in some of the posts above).

If I autocross or track my car 10 times a year, I may look for brake pads that are easy to swap for those events. I may run a different brake fluid all year round (more expensive) to improve system stability. I may run adjustable dampers providing I can be diligent enough to record performance oriented data to allow me to choose a DD setting and a track/autocross setting providing my dampers are good enough for that task (most are not). I may choose spring rates (matched to dampers) that favor street compliance over poor roads, speed bumps, expansion joints, over spring rates that favor track work. I may run softer ARBs and higher spring rates over softer spring rates and higher ARB rates (to better deal with poor road conditions). I may run high performance summer tires during the summer and switch over to r-comps for the event and winter tires for days/months averaging temps under 50F.

In summary, the mission profile is well defined: daily driver takes precedence over all else.
The flight envelope is also well defined: 10 track days a year but I will settle for mediocre results due to my compromise. The edges of the flight envelope determine the limits of each system set-up. Think of this as running 20 lbs of boost on daily driver, then dumping some race gas in and running 35 lbs of boost for 1/4 mile or autocross with alternate ECU map.

That being said: now I can dive into fine tuning consisting of spring rates, ARB rates, tires, bushings, alignment settings, etc. Get into fine details using the posts above and more, to the limits of your comfort level.

I think that one can successfully compete in any car, in any venue, providing it is/gets set up do reach the driver's expectations.

 

[Slow Paul]

That's some good stuff there. It's made me somewhat rethink my own mission-profile.

 

[Chris_uk]

all i was is to basically increase the cornering at speed, as with stocks it tends to sway a lot onto the other side, ok so maybe i shouldn't speed as much but hey ive heard just by lowering the 2 and adding a front strut bar that it improves handling heaps and bounds, so my question, for mainly daily drive and some added B road fun, eibach 30mm lowering springs and say corksport strut bar FTW? im not going to autocross and not looking to go in depth here, just some basic stuff for me, also will me lowering it by 30mm be ok for say having a car full of people? dont want to be running on my tyres lol

 

[Joker2]

all i was is to basically increase the cornering at speed, as with stocks it tends to sway a lot onto the other side, ok so maybe i shouldn't speed as much but hey ive heard just by lowering the 2 and adding a front strut bar that it improves handling heaps and bounds, so my question, for mainly daily drive and some added B road fun, eibach 30mm lowering springs and say corksport strut bar FTW? im not going to autocross and not looking to go in depth here, just some basic stuff for me, also will me lowering it by 30mm be ok for say having a car full of people? dont want to be running on my tyres lol

Better Dampers can control the roll if this is desired. The car is designed to under-steer for safety reasons. A front strut bar will do nothing except for increasing stresses on strut-towers a bit. If you get one that triangulates to the firewall, you can claim increased stiffness, again at the cost of increasing stress at mount points. There is very little travel available on this car before you ride on the bumpstops (read extra springs) so lowering to the point where you are constantly on bumpstops may not yield the results you are looking for. If you want to lower the car and still have the suspension working, you will need to consider different bumpstops, with a bit higher rates, a bit shorter, revalved dampers and higher rate springs. Now the ARB will not work as designed and that needs to be tweaked also.

Without going into depth, Mazda is paying a few decent engineers to develop a package that consists of matched springs, dampers, ARBs, ride height, NVH, etc.
The aftermarket tuning crowd will replay the same old songs: stiffer, bigger is better (they sound kind of funny). That introduces a mismatch that only time, driving and money can re-balance. Stay stock until you get a better understanding of what does what for your car, it is pretty good from the factory, and quite safe.

I won an autocross in the rain with only better street tires. Yes the car had lots of roll, but my Miata in that event would have overwhelmed the tires with her 700 in.lbs. front springs and >1" front ARB. While the 2 has lots of understeer/push by design, she is also tail happy at times. Lowering springs will overwhelm the dampers, and decrease the cornering at speed.

Tighten the nut behind the wheel first, by driving the car at its limits at autocross or track days or similar events (rally is awesome for learning car control) with some decent instruction.

Get the book "Go Ahead Take The Wheel" by Dave Grant and read it slowly. If you want to spend 3,000 quid (if that is the proper term) on mods, you will get much faster and safer by spending that dough on instruction.

I practice what I preach (mostly) by getting lots of seat time and instruction. Last event, I beat some serious cars: Lotus Elise, Mustang GT, Honda S2000, a few M3s, Lancer Evos, etc. all in a Chrysler Crossfire. The day I beat a Viper in the Mazda 2 at an autocross/autoslalom, that dude never showed up again.