Hi George, Could you expand upon rake vs. corner balancing? It would seem I would want to focus on corner balancing and adjusting the rake angle would upset that. Could you provide a little information on the goal of adjusting rake vs. corner balancing?

 

Knowing full-well that I'm setting myself up to be chastized by Mark, here is my thoughts on the above:

Set the overall ride height first, with the objective of getting a predictable car. Too low and you will be too far into the bump stops and/or corrupt the suspension geometry, both of which can lead to an unpredictable car. Use zip ties to figure out if you are deep into the bumpstops. If you know someone who has a good handle on the optimum ride height of the car, listen to them. If not, let some good drivers who are good at identifying handling ills (not all fast drivers can do this, by the way) drive your car and listen to their suggestions.

Set the rake next. If the car is pushing or loose in steady state corners, consider raising just one end of the car by one turn and see what happens. Do this while your bars are set to neutral. If you have to max both bars out to get the handling under control (i.e., front max stiff and rear max soft, or vice versa) you probably should consider changing the rake or the spring rates (this is assuming you have a reasonable alignment). While doing this you need to remain aware of transient vs. steady state handling balance, since you use shocks to tune transient balance, of course. If you end up with some really wacked out rake, then you probably have some other issue, like poorly choosen spring rates or sway bars.

Now it’s true that mucking around with the spring perches affects alignment, but don’t let that stop you from experimenting. One of the best things Eric Meyes likes to say is – “Don’t be afraid to change things.” I agree with that whole-heartedly. If raising the rear of the car make it handle better and go faster, do you care if your camber changed by 0.2 degrees? I don’t, at least not for that day. Eventually, of course, you want to take temperature readings and fine-tune the alignment, but don’t let the cost of an alignment or three keep you from experimenting.

Once you think you have the front and rear ride heights dialed in, then bring the car in and get it corner weighted and aligned, hopefully after you’ve had a chance to get some tire temp data so that you know what you want your final alignment to be. Then, if you bars are still set to neutral, you should be able to use them (and shock settings) to achieve the final balance you want, since it will likely change a little with the new alignment & corner balance.

Setting up a car is a confusing balancing act of many variables, and what I say above is a simplification of all the things I played with last year, and I still have further to go. But I have been taught that ride height & balance are some of the biggest “*****” at your disposal in terms of making major changes to the handling of the car, so get those things under control first.

Hope this helps.

 

Also, a quick follow up on why rake affects balance.

Best I can tell, there are two competing forces that affect how the balance of the car is changed when the rake is changed: Roll center height, and bump-stop engagement.

If you are into the bump stops, even a little, at max-g, then raising one end of the car has the effect of lowering the spring rate of that end. This happened to me in my CSP-ish Miata of yore. Had an oversteer problem, raised the rear a turn or two, and the problem went away. I know I was into the bumps on that car.

On the other hand, if I understand suspension geometry correctly, raising one end of the car raises the roll center of that end, and hence increases weight transfer across that axle, thus decreasing grip of that axle. If I have that backwards I’m sure somebody will correct me.

So, if I am correct, the effect of raising one end depends on where you are with respect to the bump stops, which is why I say give it a try and see what happens.

 

Wow. Somehow, I'm disapointed in not being told

FAIL!!!

In fact, I feel... a little... lost.


LOL, just kidding, of course. Good luck on your path.

 

I tried searching and couldn't find an answer from a reliable source, so I figured I throw this out to the STX crowd. Does anyone have a set of stock RX-8 front and rear bumpstops that they could measure?

I'll be doing a coilover install sometime in late January/early February, so if no one has an answer by then, I'll measure mine with a vernier caliper and post my findings.

Thanks.

 

I'm looking into the exact same issue. I do have some OEM bump stops handy - what are you looking for - overall height?

 

OK, I'm bored and guessing you want height.

Front & rear are different. I have two pairs - yellow and red. Unfortunately I can't remember which is front & rear, but I'm sure that can be established.

All values taken with verneer calipers, with the metal top hats still attached.

Yellow: 72 mm tall
Red: 75 mm tall

The yellow bump stop has a larger OD, and is stiffer than the red. I'm guessing the yellow is the front, but that needs to be validated.

 

Excellent! Thanks George, the heights were the values I was looking for. I'm sure someone will chime in soon with which color is for the Front vs Rear.

 

Just got a Corbeau FX1 Pro along with their Sliders and Brackets.

Brackets = 10.5lbs
Seat = 18lbs.

 

Have you had a chance to drive the car yet? My Bride really transformed the car for me.

How is headroom? Do you sit any lower?

 

I've took it on a few test runs through my neigheborhood and loved the way the car felt. It felt so much faster! You can really get a feel for what the car was doing especially when it starts to get loose. I love it

I actually sit higher than the OEM seat! Which isnt good. I'm only 5'8 130lbs So I've never had a problem with head room. Now with my helmet I do not fit unless I take the bottom pad out of the seat...But then its not very comfortable! Not sure if I should find a slimmer pad, or find a way to lower the seat brackets...

 

I pull the pad from the Brides when I race, to get me as low as possible, and to get the center of my helmet below the top of the seat. However, I found that when I sit directly on the bottom of the seat and use the factory seat belt, I slide forward under braking - quite a bit, in fact. It was unsafe. However, once I added the lap portion of a racing harness, all was well. Now, I don't use the factory seat belt while autocrossing - just the lap belt.

I don't drive that way on the street (I use the pad & the factory belt) nor would it be acceptable for track use, but it works well for autocross.

[edit] If you can, I reccomend looking into a lower mount. It really helps from a driver/car interaction standpoint. I'm 6' so you probably don't need/want to go as low as I am (my friends tell me I look like a kid in his dad's car when I run around without the pad) but dropping an inch or to from the OEM position would probably be a good goal for you.

 

Btw, if anyone is selling a lightweight set of 17x9 wheels, please shoot me a PM. At this point I'm considering everything from the Enkei RPF1, Kosei K1-TS to the WedsSport TC005. Let me know what you have and what you'd like for them.

I hoping to secure a set of STX wheels in the next 2-3 weeks.

 

Mark, thanks for the tip on the extension. Seems like something we should all be doing. Either that or run a lap belt through the seat holes, like I do, but that's a pain to use on the street every time, since you also need the torso restraint of the OE belt.

 

Thinking of getting the Sparco Chrono sport. Seems like it might be a good compromise between DD and autox use. I had a Corbeau FX1 in my STI and it was a little much for DD. 17Lbs. but i dont see a bracket for the RX8 on their website.
Anyone have any experience mounting Sparco seats?

 

Rawrx8 does, he fabbed up his own brackets for his sparco seat, then a company locally offers it too (at a much higher cost then poking Rawr til he does it ) Shoot him a PM and I'm sure he'll send you pictures of his bracket.

 

I've been using my Corbeau FX1 Pro for about a week now. Longest drive has been about 30 minutes, and it has been fine and not uncomfortable at all. I would say that anything over a 2 hour drive might be much. But theres just the 4 bolts and it only takes 10 minutes to swap the OEM seat back in.

 

Maybe my *** is just bigger than yours. My legs would start to fall asleep after about a half hour.
I have the brackets and sliders left over from the old seats for the scoob. Might have to take my seats out and se if it's possible cut and weld to make them work with the rx8.

 

Check out the Sparco ProFi XL. It's a little larger than most.

 

Look like the Kirkey with a cover starts at $430 shipped. Same price as the Sparco I posted. And every Kirkey seat I've ever sat in has felt like a torture device.

 

It would be nice if I could just go down to the race seat store ant try them all out.

 

Memoryfab used to sell low-profile rails for Sparco seats that fit the RX-8. I bought one last year, but never used it as I choose to go with a Bride seat instead. I still have the rail but it looks like I may use it this year, so it's not for sale.

Odd thing is, the Memoryfab website now just lists a phone number. It may be worth a call, but if memory serves correctly the wait for rails could be 6-8 weeks. At least, if you have to wait, this is the time of the year to do it.

 

I wonder if one of these might work in the RX-8 for the airbag light? It would only cost $10 to try and if it fails you could easily turn around and sell it on an Evo/Subaru forum:
Link: http://www.rallysportdirect.com/shop...vo-p-3978.html

 

I've had the Kirkey Road Race seat in two cars and love it, planning on moving it to a third car. I can't speak to how it would work in double duty action though, mine were all dedicated racecars.

 

Thanks for bringing this up. I'll probably get one for the passenger side to save a few lbs - much cheaper than another Bride.