TeamRX8

iTrader: (25)

^ that was in 2007, not so special now ....

USMC_Skip

sub'd can't wait to read the nov issue

Aipex8

iTrader: (1)

I looked up the MFD after seeing it in the latest Modified. Looks like they make an MFD2 that does the same stuff as the MFD, but also connects to the OBD port. Check it out:

http://www.arkdesign-us.com/mfd2-multi-function-dash-2

ganseg

iTrader: (5)

Ok, I read other magazines too... In the Nov Grass Roots Motorsports on Page 122 of the article on an MX-5, they say "Our experience with the RX-8 and later Miatas has taught us that too much negative camber at the rear end actually binds up the car, so we set the rear suspension to -1.5 degrees..."

When I had my used KW3s installed, I had them set it to -2 all around and have been happy, but I have only had one track event to really try it out. Do others know what they are talking about?

They also put a big sway bar on the front of the MX5 and none on the rear. This sounds like an Rx (I mean prescription) for a lot of understeer, but I am the rookie here.

ganseg

iTrader: (5)

I posted on GRM too. Per Schroeder replied with "Bind-up is referring to too much rear grip---to the point where the car feels pushy or tight as it's understeering." I don't know if they had a big sway on the front of the RX-8, why not run less bar on the front rather than reducing grip at the rear?

TeamRX8

iTrader: (25)

Sure, if you want it to roll over in the corners like a pig in the mud

chiketkd

iTrader: (5)

You're asking some good questions...

However, someone giving you the answer is not going to be as meaningful/rewarding as you finding it out yourself. Read books on setting up race cars, test different springs, shock settings, swaybars, alignments, ride heights etc on your car. See what works and what fails horribly. Develop as a driver. Develop your car. In the end, you'll draw your own conclusions and be the wiser for it.

RX8SHNKVI

iTrader: (1)

Subscribed

Modified Dave

Interesting stuff, ganseg. I've done some work for GRM in the past. Great guys and a great mag. I read it every month and have been for the last decade or so.

Regarding the rear wheel camber issue GRM raised, I'm not sure if the car in question was using race shocks and springs, nor do I know their toe settings or tire choice, so it's difficult to comment on that. But since we know the rear of these cars (both the Miata and the RX-8) gain camber quite aggressively during rear suspension compression, it does make sense to run less static negative camber. I think their -1.5 degrees of rear camber is a good starting point, from which you can dial in your own settings using a tire pyrometer to see how much of the contact patch you're really using. Ideally you want to see about 10 degrees more tire temp on the inner third of the contact patch with the tire running in its optimum temp range right across the board.

With respect to running a big front sway bar and no rear bar, understeer is caused when you have more rear grip than front grip and this front/rear grip balance is affected by much more than just sway bars. Front and rear spring rates and damper settings as well as wheel alignment (both camber and toe) also play a big roll, as does weight distribution and even front/rear downforce when running at higher speed circuits. In the case of my RX-8 on BC coilovers w/ stock sway bars, the only way I've been able to dial out the excessive oversteer it's been suffering from during track testing is to disconnect the rear bar and increase the spring rates, add some preload, and dial in a little extra rear toe-in, but ultimately the inconsistent rear grip issue I've been struggling with has to do with rear suspension travel rather than front/rear roll stiffness. So take my setup with a grain of salt, but it does illustrate the fact that running with the rear bar disconnected doesn't necessarily mean understeer-city.

Coincidentally I've recently been discussing suspension design and sway bar tuning with Peter Cambridge, formerly the senior chassis development engineer for Prodrive and the man responsible for developing their RX-8 demo car and their PZ-type suspension kit for it. During our discussions, I mentioned to him how my RX-8 was generating much better rear grip and overall balance with the rear sway bar disconnected. He responded that when he was working on the Aston Martin road suspension he had a long chat with George Howard-Chappel who runs the Prodrive race team and that in his view traction is everything, so they did not run a rear sway bar on their race cars. They also did not run tender springs on the rear, just a single main spring that they let go free in extreme rebound.

Of course Prodrive would have had the rest of their suspension package carefully dialled in to work with no rear bar, so don't think that disconnecting yours will magically make the car handle like a Prodrive racecar. It's simply an indication that there's more than one way to dial in a suspension, and how you dial it in will depend on the tracks you're racing at as well as your driving style. At high speed circuits I always disconnect the rear bar on my race car because I prefer the car to have a bit of understeer at the limit, which allows me to drive into corners more aggressively and confidently and then I get it to turn with trail braking and throttle modulation. But other guys in similar cars run a rear bar because they like a looser setup. For autocross, which is a totally different animal, I'm much more interested in transitional response and low speed rotation, so well matched sway bars with some added rear stiffness is what works best for me (along with different alignment settings and tire pressures and damper settings). I haven't done much autocrossing in the 8 yet, so time will tell what works best for me in this car when dodging cones.

TeamRX8

iTrader: (25)

If you are making an RX-8 work without a rear swaybar it's only because you're masking some bigger setup problem.

Zoom4Three

The reference in the article was directly related to our experience setting up my past SCCA Stock class Solo cars over the last 12 years. The RX8 we were referring to in the article was running under stock class rules which requires stock springs and stock rear bar. The front bar, alignment and air pressure are your main tuning tools in this class.

The "binding-up" comment was referencing throttle induced understeer from apex to trackout using Hoosier A6's which have a lot more longitudinal grip (forward bite) than 140+ treadwear tires when warm. The power-on understeer was the overriding handling trait that we worked to correct during the three years John Rogers and I competed in B-stock with the car. We had to balance this trait against transitional oversteer at the limit when hammering through slaloms etc.

We found adding a slightly stiffer front bar (Hotchkis MX5 bar) coupled with reduced negative rear camber struck a balance we were happy with on most autocross courses. Our tire temps and shoulder wear also confirmed that the set-up was in a "happy place". Another consideration was the ProSolo drag-style launch. Adding unneeded rear negative camber would hurt 60 ft times.

Since you are running KW's, 140+ tread wear tires and tracking the car, your optimum set-up is going to vary from ours. Hope this clears things up a bit.

Chris Harvey
GRM/Tire Rack MX5 STR

PS - The only time we removed the rear bar from the STR MX5 was during anti-roll bar back to back testing. We found no time benefit or significant improvement in handling balance although the drivers could feel the balance shift slightly. Most of the season was run with the rear Hotchkis bar set in the "soft" setting.

ganseg

iTrader: (5)

Dave and Zoom4Three, thanks for your thorough and thoughtful responses! I am genuinely interested in this and have read several books (Carroll Smith, Ross Bentley) and experimented with my cars. Unfortunatley this has to be within a limited budget of time and money, so hearing other's experience is huge. I get about one or two track weekends a year and have driven on four tracks with about 12 events total. Thankfully my current setup is good for the two high-speed tracks (Brainerd long course and Road America), but I want to experiment with less understeer for the more technical tracks. When I go to a more technical track, I may lower my rear neg camber a bit to see if I can "handle" it! Right now it understeers more than stock but that gives me a comfort zone in the 70+ mph corners on the faster tracks I drive. (I think my front spring rate is 450# and my rear is 285#. ( Stock sways, nt01s, track pads, -2 camber and slight toe in all around.)

Modified Dave

100% agree. I am trying to work around the stock front bar and rear travel limitations at the moment. I hope to make a decent size adjustable rear bar work with the Moton Clubsports and a big adjustable front bar. Work in progress, as always.

ganseg

iTrader: (5)

INPUT!

Here's a direct answer from John Rogers at The Tire Rack--even more info for you.




Gary:

Let me set this up a little more. Our experience was based on the Miata/RX-8 competing in SCCA "stock" class autocross, which used stock springs rates, aftermarket dampers, larger front anti-roll bar and stock rear bar. We maxed out the front negative camber, which usually landed around -1.4 to -1.5 degrees per side. Our early attempts at alignment set the rear to match whatever we could get in the front. But ultimately we found the car had some steady-state understeer. The rear had too much lateral grip relative to the front, resulting in insufficient yaw rate. Some slip angle is needed for the tire to generate significant cornering force, and the highest ultimate cornering power comes when there is a few degrees of yaw at the rear of the car.

We ultimately found that reducing the negative camber at the rear by about half a degree versus the front took away a little ultimate lateral grip at the rear. Just enough to allow the rear to yaw a few degrees, which helped the car to rotate (even at steady state). Cornering speed increased, and ultimately allowed the driver to unwind the wheel and pick up the throttle sooner since he wasn’t waiting on the gentle push of the front tires. We had also played with the rear toe setting, but found going beyond zero toe would make the car too loose in transitions, so we returned it to zero. Backing off the rear negative camber proved to strike the best balance between steady state and transition handling.

Admittedly, using the KW coilovers on your RX-8 brings another variable to the equation that we didn’t face with our “stock” Miata or RX-8. KW changes spring rates. The stock springs on the Miata and RX-8 are relatively soft, especially in the rear. I haven’t checked the progressive rate of the rear springs, but I suspect that KW increases the rear rates a little more than the front. This effectively moves work off the front to the rear, helping solve the understeer problem. So it’s possible that there is less need to reduce rear negative camber than in our “stock” car. As we put this project together we decided to start with something (the alignment) we know, measure and tune from there. During our testing for this project, we compared the OE suspension with the KW coilovers, leaving the Mazda anti-roll bars on the car. In this configuration, we found the balance of our MX-5 to be pretty good, even with the approx. ½ degree front to rear stagger in negative camber.

I’m not sure if you have changed the anti-roll bars on your RX-8. But for this project it was only with the addition of the larger anti-roll bars that we found a need to tweak our alignment set up further. But as far as steady-state cornering goes, the small stagger in negative camber continues to work well. There is no shortage of rear traction during cornering, and steady-state understeer is almost non-existent. We have had to add in a little rear toe in to solve a power-on oversteer issue. But I suspect we’re now cornering and accelerating hard enough that there is some additional bushing flex causing dome dynamic alignment changes, etc.

TeamRX8

iTrader: (25)

That input was posted here many years ago, forever buried in the annals of the RX8Club archives ... I suppose since it didnt get posted with any association to TR or GRM it lacked the ZOMG factor

WTBRotary!

iTrader: (6)

Sub...

ganseg

iTrader: (5)

under my skin is right. If you take 10% of the time you and a few others spend degrading posts and put some of your good input into posts instead, we all would be far ahead. I am not an idiot just asking random questions and bothering people. I want to learn and maybe others will learn at the same time. Three or four people made the effort in the last 24 hours to be helpful. If I had searched, I would not have gotten back to what you learned 4 years ago.

When I want to enjoy my time online, i have to go elsewhere. Sadly I have to read thru all the lambasts here to get to the worthwhile stuff.

TeamRX8

iTrader: (25)

I never said you were, that's all in your head

I'll change that to "under your oversensitive skin", thanks

You can go somewhere else if it makes you happy, but you will never find the wealth of RX-8 information that already exists here

ganseg

iTrader: (5)

I agree. Why don't we improve on it instead of taking away from it? When I had an MR-2 spyder, same situation on spyderchat only worse. Everyone who would post their car for sale would get squatted on. Nearly every new person would get squatted on. The site had great info, and again it was the only one. But it was painful reading it, not funny.

I don't want a site where everyone just asks without engaging their brain. I do want a site where people are decent to each other and support each other. I also wouldn't mind having more people become interested in the 8. That will help availability of parts and prices. Maybe the 8 wouldn't be on the chopping block.

I know you have a lot to offer. I know this site has a lot of great info. The year I have had with the RX-8 has been one of the most fun I have had with a car and this site has made a huge difference. This thread is really cool. What is there to be negative about?

Modified Dave

That's an interesting read from John at TR. Thanks for adding it to the thread, ganseg.

Here's a surprising tidbit of info from Peter Cambridge, the former Prodrive suspension guru I mentioned earlier. While developing the Prodrive shock/spring package for the RX-8, Mazda Japan sent him a lot of information about the car, some of which he couldn't share with me but their recommended alignment settings for track use struck me as quite surprising, especially in light of the GRM/TR method of setting up their stock class Miata (though that's an autocross setup, which tend to be quite different from race track setups).

According to Peter, "At a trim height of 355mm front and rear (15mm lower than standard UK car), from the wheel centre to arch lip:

Front
Total toe 10' in
Camber -1deg 45'
Caster 7deg 41'

Rear
Total toe 30' in
Camber -2deg 00'

These settings assume the car is running stock 18" Bridgestone tyres."

Toe-in on the front is not something I was expecting to see, nor the aggressive toe-in on the rear or the fact that they've recommended more rear negative camber than front. All I can assume is that they've found these settings to work best with the relatively narrow OEM Bridgestones at whatever race track they do their testing at, whereas we're all accustomed to setting our cars up for considerably wider and/or stickier tires with big front sway bars.

Still, I thought this was worth sharing if for no other reason than to illustrate the fact that there's a wide range of suspension setups that can be made to work, so it's really up to each of us to acquire the necessary tools to dial ours in for best performance for our particular set of modifications, driving style, and type of driving (autocross, HPDE, RR, drift, etc). I never head to the track without a tire pressure gauge, tire pyrometer, camber gauge and toe plates, a lap timer/data acquisition system (I've mostly been using a Vbox Driftbox for it's ease of use and yaw sensor), and a laptop to record all my settings and changes to them. Keeping good records really does help a lot when trying to dial in a suspension, not to mention it can save you some work when you go back to the same track but don't remember what your dampers were set at or what sway bar stiffness worked best.

olddragger

iTrader: (3)

we at the Ga RX8 club have literally thousands of miles on track. Well over a combined 50,000 during the past 6 years. One members car has 7-8K on track and over 100K on the oridginal engine.
One member, if I am not mistaken, is currently in the lead for TTD with NASA SE.
We run Road Atlanta, Roebling Road, CMP, Barber in Birmingham, etc.
We have tried many different suspension set ups and alignment settings.
Wide variety--from oem to anything goes.
Currently mine ( I have a little over 300hp to the wheels)
Kw's
RB front and rear bars and front end links
running 18x9.5 rpf 1 wheel with" R6 245/35/18's
-1.7 up front
-1.5 in rear
minimum toe in front and rear
cant remember the castor
Lets just say the car is much more capable than I am. It is very confidence inspiring.
Transistions are beatiful--not only in the esses but in braking to throttle and throttle to braking all in the same turn.
By the way I am oem on the body--no spoilers or lips.
Hard fast line braking is among the best and trailbraking I think IS the best. So after years of driving, this is the set up I have settled for.
Now like others have said---you have to do your own homework in your own car. No substitute.
And here is my point --In our club--- no two cars have the same set up--none. Wonder why?
And now I have to get on a John Deer tractor and suck up leaves---sigh.
OD

Modified Dave

olddragger, so you're running some front toe-in? Very interesting. I tend to dial in some front toe-out on just about any car I take to the track as a way of aiding turn-in response, but maybe turn-in response is already so good on the 8 that I've gone in the wrong direction here. I assume you're using the toe-in to help with high speed stability, given that you're running at some high speed circuits?

Road Atlanta = pure awesomeness, btw. That is a big boys track if there ever was one. You've got some great road courses down there in the duuurty south And it would appear I only have 7100 posts to catch up to you. Heh.

olddragger

iTrader: (3)

Lol---thanks Dude and yes high speed stability is my preference. With my Fi set up i am seeing fairly high speeds (Approx 140+ or so) so braking and high speed maneuvering is not to be ignored by someone wearing bifocals.
I have never had a need for more turn in--the 8 is so dang smooth and with trail braking ( one of the great under recognized strengths of this car) a twitchy sudden turn in response was not for me. I end up steering with a lot more than the steering wheel
I have seen these discussions time after time and mostly really good advice is given, but, rarely do I see the suspension mentioned in dealing with lift throttle, throttle manipulation during steady state cornering, rapid throttle on/brake on episodes, rapid chassis recovery or uneven surfaces. Thats real life on the track and very important as you know.
I am sure you also know that anything can happen-- and you have to drive the piece of track you are given
My point being --whether you are at a 1.7 or a 2.0 chamber-- if everything else is ok then it is not going to matter much at all. The most important thing IMHO is getting used to the car and being honest about your driving style/ability. More times than not its the driver that makes the difference not minor changes to suspension settings.

Good luck on your adventure dude--i will be envious and following along vacariously
OD

Redshift

iTrader: (2)

Dave, forgive me if it's in the thread or the magazine (I've read both) but a couple of quick questions regarding the ARK MFD.
I've been looking for a neat way to integrate proper water temp, oil temp and oil pressure for a while. I have the Racing Beat pod, but haven't bought any gauges yet (in next seasons budget.) but I don't like the idea of losing that space (it's where i keep my parking pass for work) so was intrigued by the neat all-in-oneness of the ARK unit.
So, the questions:
1) Have you done any testing on the accuracy of their senders? I've seen some manufacturers seem to be all over the map.
2) While it looks small, how big is the display unit really, and how many places in the cabin would it fit? I'm trying to keep a fairly stock look to my cabin (thus the Racing Beat pod) but not sure I like the stuck on the back of the ashtray lid thing, but can't figure out if it would fit elsewhere in the cabin relatively neatly but still visible.

ganseg

iTrader: (5)

Have you seen this:
https://www.rx8club.com/showthread.p...49#post3762549