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Spring rate vs Ride comfort vs Performance database (FD3S)

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Old 01-23-16, 11:26 AM
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Originally Posted by LargeOrangeFont View Post
Keep in mind I am speaking from an FC standpoint, and they like a bit less tire stretch than an FD from all I have seen.

To Blue TII's and lookatme's point, you set the car up for the tires you are running.
both statements are true. this one time, we had the car set the PTE lap record at sonoma/sears point/infineon, which was on 225/45/15 hoosier R6's (i think) on a 15x7" wheel. we then decided to run the USTCC races because they were doing the WTCC sideshow, which was pretty neat*

USTCC runs Kumhos, and we had a choice of tires, and after looking at the three we picked i think a 235/40/17, as it was the shortest and widest (i wanna say we could have done a 225/40/17 or a 245/??/18)

well long story short, even after a test day, car just did not work! they used the motocycle (or maybe NASCAR) configuration, which instead of going from turns 7-8-9-10, uses a straight at 8 and then at 9 there is a 30mph right/left complex into 10. its there to keep expensive/fast cars off the walls. anyways at the end of our race it was so bad that the braking zone for 9 started before he left turn 7.

for the tire stretch bit, a 225/45/15 R6 is faster on a 15x8 than a 15x7, and it is also faster on a 15x9. the 205 R6 on a 15x9 seems to be just past the point of diminishing returns, i think 15x8 or 15x9 would be drivers preference, and the one they liked would be faster.

*for that weekend, the pits smelled like perfume, and the language was italian, which was kind of neat.
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Old 01-23-16, 06:36 PM
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Yeah, I tried 235/40-17 up front on 8.5" wheel on the TII to get it lower with full suspension travel and it felt nice on the street and flat didn't work racing (parking lot, hillclimb and Kart track events).

I went back to 255/40-17 up front on the 8.5" wheel, but I did like the change from 275/40-17 on 9.5" wheel to 255/40-17 in the rear. So, 255/40-17 front and rear with 8.5" wide front and 9.5" rear for the more progressive slide in/out of slip angle.

Put these wheel/tires on the RX-8 and I preferred the 255/40-17 on 9.5" wheel up front for that awesome steering response.

The FC rear suspension is ok in geometry if poor in execution, but the front is just a strut is a strut is a strut.
--------

This thread is on FD suspension which is totally different. The front has a pretty good camber gain so you don't have to lock it down like a strut and it can handle low profile and very stiff sidewall tire well.

If I put race tires with rounded carcass profile on the FD (like Z221 Ventus TD) racing wears the tires to a square profile. FD is so easy on tires!
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Old 01-23-16, 07:20 PM
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Originally Posted by BLUE TII View Post
FD is so easy on tires!
once you get the tire temps inline, the tires last much longer.
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Old 01-31-16, 08:07 PM
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On my FC I was running 255/40/17 on 17X9 front and rear. The car was fast but I was very busy at the wheel and waiting on the car off every apex. No one will be able to convince me that a 10 inch wide wheel would have fixed any of that.

I now run 275/35/17 on 17X9.5 and the car is faster. I'm back on the gas earlier in every corner and carrying more speed down the straights (GPS verified). Yes I know the wheel is not wide enough, I will probably go to 17X10.5 in the future.

These wheels were a little over $400 shipped for a set and are 21 lbs, so I don't care they are not optimal.

My FC is not bad on tires at all.

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Old 01-31-16, 08:56 PM
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the z06 looks and I would guess feels like my 11/11 set up, the gtr looks and feels like my 8/6 set up by listening to the comments.
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Old 01-31-16, 09:01 PM
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Originally Posted by lOOkatme View Post
the z06 looks and I would guess feels like my 11/11 set up, the gtr looks and feels like my 8/6 set up by listening to the comments.
You are reaching now buddy.
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Old 01-31-16, 10:00 PM
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Originally Posted by LargeOrangeFont View Post
You are reaching now buddy.
I am just saying that I felt the same way as the driver was describing. 11/11 was exhausting and the car was loose. The 8/6 is a stroll in the park when driven fast.

I mean I felt the same exact way and with about the same comments. The car was loose or seemed to skip around or float around, the 8/6 rock solid at high speeds and a ton of grip.
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Old 02-01-16, 12:10 PM
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Except if you have ever raced a Z06 you know they are very softly sprung with swaybars making up for it. They drag the front splitter in straight line braking.

Coming from an FD they seem like boats. Very fast boats.
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Old 02-01-16, 01:10 PM
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Originally Posted by BLUE TII View Post
Except if you have ever raced a Z06 you know they are very softly sprung with swaybars making up for it. They drag the front splitter in straight line braking.

Coming from an FD they seem like boats. Very fast boats.

Edit.

Last edited by Tuning4life; 02-01-16 at 02:09 PM.
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Old 02-01-16, 07:12 PM
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Originally Posted by LargeOrangeFont View Post
You are reaching now buddy.
Nothing new, what about this:
Originally Posted by lOOkatme View Post
I was scared driving one section at 90-100mph with the 11/11 and the car was all over the place. a mess. I put the 8/6 on and I was full throttle up to 140mph and the car was rock solid, felt like I could go even faster.
Hilarious...

Last edited by ZDan; 02-01-16 at 07:21 PM.
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Old 02-02-16, 07:18 AM
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Ohlins DFVs is what ive been using. I've found them to be just as comfy as my stock oem suspension and on 3 click from full soft they are definitely more comy...and a more refined drive.
Are they just as comfortable or more comfy than my wife's 2015 toyota yaris going over concrete shitty uneven crappy roads.....simple answer "No". However on tarmac roads the ride comfort is sublime.

Ohlins dfvs on a wet track day...and they did just fine...some would think the 11kg spring rates combined with r888s in the wet is suicide but the ohlins dfvs are very well behaved all round.
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Old 08-08-17, 08:21 AM
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Originally Posted by ZDan View Post
11kg/mm springs provide 78mm droop travel up front and 60mm in back with 2mm preload, so not really a problem there.
If you're talking about the suspension just not moving enough due to spring stiffness, suspension travel over bumps is going to be a much stronger function of high-speed damping than spring rate.
If you're talking about available travel while cornering, the stiffer spring rate will have *more* compression travel available for soaking up bumps because it doesn't use up as much for cornering loads.

Kind of agree, but I think the f/r wheel rate bias is a bigger issue.

This is totally the opposite of my impression. If anything, it feels like the damping is quite low relative to spring stiffness. My "happy place" *on the street* with the 11/11 springs was ~8 clicks in, vs. the 10 clicks recommended setting. At the track I was at 5/6 clicks with 11/11, 4-5 clicks front with the 13kg/mm front springs.

Not so much. Frequency varies with square root of unsprung mass, so adding a 220 lb passenger only lowers the natural frequency on that side of the car by about 6% (sqrt(1820/1620) = 1.06) , little to no effect on the driver's side, average difference 3% lower frequency.



With 11/11 and 12/12 springs, you have rear wheel rates that are 28% stiffer than front. With 8/6 springs, front rate is 4% higher than rear. THIS IS A HUGE SWING IN FRONT/REAR WHEEL RATE, 32% less rear bias!

That's my main gripe with the Ohlins springs, IMO they should really be more like 11/8 for street-oriented but trackable, or 14/11 for track-oriented but streetable. I don't think 11/11 is a good compromise setup!


You wouldn't be just comparing a relatively stiffer vs. relatively softer setup. The front/rear wheel rates between those two setups are VERY different and that will dominate subjective impressions of handling demeanor. For sure the 11/11 will feel *stiffer*, but with 32% stiffer rear wheel rates vs. fronts compared to your 8/6 springs, it will also feel more twitchy and less confidence-inspiring. Doesn't mean you can conclude that "stiffer is worse". Would be WAY more valid to compare 8/8 vs. 11/11, or 8/6 vs 14/11 or 11/8.

I have been racing an rx8 a lot with a 9/6 set up and the cars balance is great. I have been getting 3-5 positions in my class of 35-40 people. its more of a autocross type running and the rx8 does well. I take the rx7 out and the rear seems too stiff, I can get it to slide (rear coming around pretty easy) without much braking to almost no braking, doing trail braking. The car just loves to slide the rear around. I am going to try a different set up.

I think I might try 11/8 with a 94 rear oem bar (my buddy has one).

The 8/6 does exceptionally well but I need a higher ride height on my drivers side and I am maxed out with the 8/6 set up. I also think the car is a little stiff in the rear with the 93 rear sway bar (front roll couple).

so when I get the time I might try a 8/6 set up with a 94 rear bar (much smaller), and perhaps try an 11/8 set up with a 94 rear bar. Hopefully the stiffer spring rate set up with a much softer rear will be more compliant than before. will report findings back when I get the rear bar in my hand.
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Old 08-09-17, 07:34 AM
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Originally Posted by lOOkatme View Post
I have been racing an rx8 a lot with a 9/6 set up and the cars balance is great.
...
I take the rx7 out and the rear seems too stiff, I can get it to slide (rear coming around pretty easy) without much braking to almost no braking, doing trail braking. The car just loves to slide the rear around. I am going to try a different set up.
What do you have for tires? They can and do go bad sometimes. I had Pilot Super Sports that went off so bad the car became nearly undriveable. Still had half the tread on them, too.

I think I might try 11/8 with a 94 rear oem bar (my buddy has one).
You might first just try running with the rear bar disconnected. You can do this by just removing the nut on one side. I have disconnected/reconnected the rear bar a number of times for balance at the track. I zip-tie the link so it doesn't just flail around when disconnected.

Last edited by ZDan; 08-09-17 at 09:59 AM.
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Old 08-09-17, 09:55 AM
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Old 08-09-17, 09:58 AM
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Originally Posted by ZDan View Post
What do you have for tires? They can and do go bad sometimes. I had Pilot Super Sports that went off so bad the car became nearly undriveable. Still had half the tread on them, too.


You might first just try running with the rear bar disconnected. You can do this by just removing the nut on one side. I have connected/reconnected the rear bar a number of times for balance at the track. I zip-tie the link so it doesn't just flail around when disconnected.
its possible the tires are bad, they are 5 yrs old but still have a lot of tread left. RE-11's.


I can disconnect the rear bar easily and put the current set up close to the stock roll couple bias. I do like having a rear bar for slaloms as when I disconnect the rear bar on the rx8 the rear doesn't like to rotate around the cones well. which makes me think the rx7 is to stiff in the rear for swaybar. I might step up the spring rates with a good split and hopefully the car soaks up the bumps as well and gives me a little extra ride height. plus its free since I have all these springs.
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Old 08-09-17, 10:23 AM
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Originally Posted by lOOkatme View Post
its possible the tires are bad, they are 5 yrs old but still have a lot of tread left. RE-11's.
Those tires are bad. A ~200 treadwear tire will fall off significantly after 2 years and some heat cycles, regardless of how much tread is left.
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Old 08-09-17, 12:28 PM
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Originally Posted by lOOkatme View Post
its possible the tires are bad, they are 5 yrs old but still have a lot of tread left. RE-11's.
i don't know the number of heat cycles those tires have on them, nor how many an RE-11 will take, but chances are you are way over optimum, and those tires are done.

dead tires do not respond to tuning correctly, and they will give false results.
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Old 08-09-17, 03:24 PM
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Yes, new tires will only help but...

Still, lOOkatme is comparing his RX-8 and his FD RX-7 and his comparisons of what his cars are doing follow my experiences with racing my own RX-8 and FD RX-7.

The FD will always be a nimble car that is maneuvered with the gas pedal as much as the steering wheel.

But really, I admit the brake pedal input is important too.
How you release the brake pedal and the timing with corner turn in will determine if the rear end stays tucked in or is allowed to come out and play.

When you want the rear tucked in, you need to release the brake pedal gently/progressively and wait to turn in until after the chassis weight has settled back onto the rear tires.

You can embrace the FD nimbleness or try to numb it out, but from the specs/spring rates of the fast competition FDs I see online the chassis appears to be fastest when one embraces the nimbleness.

The RX-8 has 11.5" longer wheelbase and a different handling characteristic. It is the unflappable, faithful dog.

As a result, the 8 has one of the highest cornering mph of a production car.

As a result, you have to provoke the RX-8 rear end out with bigger inputs.

I like both, though I tune the RX-8 to be more nimble since that is what I have gotten used to from the FD.

Over pressure the rear tires, crank the rear damping higher, when running my staggered wheels/tires put wider wheels/tires up front instead of rear, put DOT Rs up front and 300 treadwear in the rear, make passengers ride in back seats and making sure I have a full tank(s) of gas are all tricks I have used to get the RX-8 more nimble.
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Old 08-09-17, 04:25 PM
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Old 08-09-17, 04:30 PM
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Originally Posted by BLUE TII View Post
Yes, new tires will only help but...

Still, lOOkatme is comparing his RX-8 and his FD RX-7 and his comparisons of what his cars are doing follow my experiences with racing my own RX-8 and FD RX-7.

The FD will always be a nimble car that is maneuvered with the gas pedal as much as the steering wheel.

But really, I admit the brake pedal input is important too.
How you release the brake pedal and the timing with corner turn in will determine if the rear end stays tucked in or is allowed to come out and play.

When you want the rear tucked in, you need to release the brake pedal gently/progressively and wait to turn in until after the chassis weight has settled back onto the rear tires.

You can embrace the FD nimbleness or try to numb it out, but from the specs/spring rates of the fast competition FDs I see online the chassis appears to be fastest when one embraces the nimbleness.

The RX-8 has 11.5" longer wheelbase and a different handling characteristic. It is the unflappable, faithful dog.

As a result, the 8 has one of the highest cornering mph of a production car.

As a result, you have to provoke the RX-8 rear end out with bigger inputs.

I like both, though I tune the RX-8 to be more nimble since that is what I have gotten used to from the FD.

Over pressure the rear tires, crank the rear damping higher, when running my staggered wheels/tires put wider wheels/tires up front instead of rear, put DOT Rs up front and 300 treadwear in the rear, make passengers ride in back seats and making sure I have a full tank(s) of gas are all tricks I have used to get the RX-8 more nimble.
Spring rate increases effect front roll stiffness.

so stock front roll stiffness with stock sways is 70.3% range.

with my 448/336 rates and stock sways the front roll stiffness drops to 66.6%.

if I install the rear bar of the 94 model year, 93 is 17.3mm 2.55mm thick, 94 is 13.8mm .8mm thick, this ratio changes to 73.2% front roll stiffness with 448/336 which seems about right.

the stock 94 with stock bars has a front roll stiffness of 79%.

in 95 they increased the rear bar to 15.9mm and a thickness of 1.85mm. this has a front roll stiffness of 74.3%.
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Old 08-09-17, 06:21 PM
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By all means tune the suspension and chassis to your liking.

But the FD isn't a GTR.

Meaning the modified FDs racing are typically faster than the stock FDs racing and they deviate from Mazda's front and rear roll stiffness ratios as well as spring rates.

If I had it to do over again with my current knowledge, I would get a stock Miata (or Kart if possible) and learn to drive without changing anything beyond tires and maintenance/adjustments for at least 5 years and then graduate into something faster and spend the money I had saved the last 5 plus years at that point.

Wait... but then I wouldn't know how to rebuild a rotary...
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Old 08-09-17, 08:28 PM
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Originally Posted by BLUE TII View Post
By all means tune the suspension and chassis to your liking.

But the FD isn't a GTR.

Meaning the modified FDs racing are typically faster than the stock FDs racing and they deviate from Mazda's front and rear roll stiffness ratios as well as spring rates.

If I had it to do over again with my current knowledge, I would get a stock Miata (or Kart if possible) and learn to drive without changing anything beyond tires and maintenance/adjustments for at least 5 years and then graduate into something faster and spend the money I had saved the last 5 plus years at that point.

Wait... but then I wouldn't know how to rebuild a rotary...

Will keep driving it and see how she responds.
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Old 08-10-17, 10:51 PM
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Originally Posted by BLUE TII View Post
By all means tune the suspension and chassis to your liking.

But the FD isn't a GTR.

Meaning the modified FDs racing are typically faster than the stock FDs racing and they deviate from Mazda's front and rear roll stiffness ratios as well as spring rates.

If I had it to do over again with my current knowledge, I would get a stock Miata (or Kart if possible) and learn to drive without changing anything beyond tires and maintenance/adjustments for at least 5 years and then graduate into something faster and spend the money I had saved the last 5 plus years at that point.

Wait... but then I wouldn't know how to rebuild a rotary...
Agreed. The car was never designed to have the level of grip you are able to achieve now so at some point to gain speed you will end up deviating away from the stock ratios and rates.

All I know how to to with a rotary is to remove them . I learned a ton driving the car with the NA rotary for a couple years. Since the car has been so reliable adjusting and tuning the suspension has netted some good gains. I feel like I'm getting close to the max effort of my setup now before I make another big change.
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