Suspension Upgrade Time: KW or Ohlins or FCM? - Page 7 - RX8Club.com



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Old 06-19-2017, 03:09 AM   #151
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I have spoken with GWR and Ohlins. GWR essentially said the behavior is to be expected when you push any suspension to its limits, and I should have purchased their Race version to extend those limits. Ohlins said something to the effect of, "You know, GWR sells a race version that is probably a better choice for your application."

Short of spending a bunch more money, it seems there isn't much left to do. Here are the options as I see them:

1. Buy the GWR adapter and other hardware needed to bump the rear springs to 280 lbs. That buys me more rear bump travel and a F/R ratio of 1.6 A side benefit is the ability to use any spring rates going forward, assuming I am willing to pay for re-valving. I have not actually priced this, but let's call it the $500 option. Tein (Blech!) makes a tapered spring in 280, but it is 250mm high, which is too tall for the shock body, which leads us to...

2. Buy a set of Tein (blech!) 336 lbs tapered (70-100x200) springs for the rear, and bump the fronts up 1K to 504 lbs. F/R ratio would be 1.5. If I use all Tein (blech!) springs, the cost would be $275 for the springs. Swift fronts would bump the price about $60. Ohlins told me I can increase spring rates 35% before a re-valve is required. The rears would exceed that. Re-valving costs $250 each plus shipping both ways. This option looks like at least $800.

3. Do nothing, drive the car for joy instead of speed, and put the money into the kitty for the Miata's turbo.

.
What's the question? Hopefully we can help. We set up gobs of DFV's and have fixed many issues with them... there are lots of factors here. Tell me how you're set up and what you're experiencing/trying to tune out. We've got lots of tricks up our sleeves from spherical screw in top mounts to remove hysteresis in the rear, to helper springs to increase rear inside wheel grip in corners where the suspension unloads. Suspension is interesting because it's got a million variables but our in-house chassis dynamicist is more than able to help.



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If there's interest from the masses, we'll consider an FPSpec Long-Stroke version just like we did for the S2k.
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Old 06-19-2017, 09:49 AM   #152
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The issue is oversteer everywhere on the track.

I have solved that to some degree by using little to no rear bar, but that induces corner entry understeer, and there is still a problem with snap oversteer in certain (not fully discovered) conditions. I *think* that snap happens due to inadequate rear bump travel, but it surprises me, so I'm never quite paying attention to all the variables, when it shoots around. That's why I'm toying with the idea of more rear spring.
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Old 06-21-2017, 06:31 PM   #153
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Important piece of information for this thread:

Ohlins' published spring rates for their RX-8 coilovers are incorrect. The actual spring rates are 80N / 8K / 457lb front, 50N / 5K / 286lb rear.

That front to rear ratio of 1.60 is pretty close to the natural frequency that has yielded a neutral car for me in the past. So, it has never been an issue of needing more rear spring. It is something else in the setup. For now, I will focus on rear bump travel and adjust ride height and (especially) preload to work on dialing in the car.

.

Last edited by Steve Dallas; 06-22-2017 at 07:18 AM. Reason: Because BOLD
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Old 06-21-2017, 10:02 PM   #154
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The issue is oversteer everywhere on the track.
Ain't you never heard? Loose is Fast!
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Old 06-22-2017, 07:14 AM   #155
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Only if you are Jimmie Johnson!

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Old 06-22-2017, 02:01 PM   #156
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Ohlins' published spring rates for their RX-8 coilovers are incorrect. The actual spring rates are 80N / 8K / 457lb front, 50N / 5K / 286lb rear.
.
DOH!

Well that helps explain why it doesn't just understeer like a fwd sedan from the factory.

My best guess to explain your oversteer is that you are ending up on the rear bumps before the fronts. Or the bump stops are not equal under load at least.

I don't think you can avoid using the bump stops at all without going too stiff. But you can shorten them, or use packers to alter the engagement point front to rear.
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Old 06-22-2017, 02:17 PM   #157
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Yeah. I was using the wrong inputs into the equation all this time. That perfectly explains why nothing was lining up with suspension theory. Now, I fully suspect lack of rear travel is what is getting me, so I will be focusing on preload and ride height to see if I can move the needle back there. I don't really want to go to stiffer springs on this car, since it will only be seeing the track a few times per year from here on out.
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Old 06-22-2017, 03:43 PM   #158
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Well it seemed to me that you enjoy posting about it more than fixing it whether or not it's on the bumpstops is basic suspension tuning 101 with a piece of wire or zip tie on the shaft. Otherwise it seems to me like more front bar is needed assuming it's neither transitional nor on bumpstops and you don't want more front spring rate. If it's not that then it must be transitional; a shock tuning/valving issue. Or lastly, it's a driver input or execution issue. More importantly, it doesn't take fussing over theoretical calculations to figure any of that out. None of that is intended to be uppity, just that it really is that simple
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Old 06-23-2017, 08:34 AM   #159
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Well it seemed to me that you enjoy posting about it more than fixing it whether or not it's on the bumpstops is basic suspension tuning 101 with a piece of wire or zip tie on the shaft. Otherwise it seems to me like more front bar is needed assuming it's neither transitional nor on bumpstops and you don't want more front spring rate. If it's not that then it must be transitional; a shock tuning/valving issue. Or lastly, it's a driver input or execution issue. More importantly, it doesn't take fussing over theoretical calculations to figure any of that out. None of that is intended to be uppity, just that it really is that simple
Guilty as charged!

Honestly, I haven't taken the 8 to the track, since last September, because I have a very well-sorted Miata, that is the Easy Button of track cars. The 8 has been a touring car / daily driver since then. I have started to miss it on the track, however...

I know how simple it is. The problem is time. I am almost always instructing, when I am at the track, and that means jumping from car to car to car, with no time take a leak, much less to mess with such things on my car. Having the wrong spring rates in mind made the process frustrating, because nothing was responding as expected.

The good news is, I am building a house 15 minutes from the track. That means I will be able to run home after a session to make a change in my own garage, then run back and test it.

I'll get it there. Eventually.
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Old 07-11-2017, 09:51 PM   #160
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sorry to bump this
But are the rear kw variants adjustable on -car or do the have to be removed?
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Old 07-12-2017, 07:23 AM   #161
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They are adjustable on the car, and they even come with remote adjuster cables.
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Old 07-12-2017, 08:59 AM   #162
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Cheers
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Old 07-12-2017, 09:39 AM   #163
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They are adjustable on the car, and they even come with remote adjuster cables.
Uhhh, I was under the impression that they don't and KW don't list any such part on their website.

With the KW Variant 3, the compression is on the bottom but the rebound is on the top. I can feel the top of the rear dampers when I put my fingers in a hole near the top of the shock towers at in the truck so you don't really need cables. If you enlarge the hole slightly you can get to the top of the damper and use a 2mm hex key (or get a couple extra adjuster ***** and just leave them installed).

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Old 07-12-2017, 09:43 AM   #164
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Huge reading comprehension fail. I skimmed his post and assumed he was asking about Ohlins, since this thread morphed into an Ohlins thread over time.

Ohlins are adjustable on the car, with include remote adjusters. I have no idea about KW.
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Old 07-12-2017, 10:42 AM   #165
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Huge reading comprehension fail. I skimmed his post and assumed he was asking about Ohlins, since this thread morphed into an Ohlins thread over time.

Ohlins are adjustable on the car, with include remote adjusters. I have no idea about KW.
They are but KW don't have extension cables.

Speaking of which, is the adjuster on the tops of the rears of the Ohlins a hex key? If so, what size?
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Old 07-12-2017, 10:54 AM   #166
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It is a small half-moon rod. You either attach a **** with a set screw or the remote adjuster with a set screw. You can adjust by feel with the **** (with stripped interior) or use the remote (with interior intact), which is much easier.
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Old 07-16-2017, 08:21 PM   #167
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Uhhh, I was under the impression that they don't and KW don't list any such part on their website.

With the KW Variant 3, the compression is on the bottom but the rebound is on the top. I can feel the top of the rear dampers when I put my fingers in a hole near the top of the shock towers at in the truck so you don't really need cables. If you enlarge the hole slightly you can get to the top of the damper and use a 2mm hex key (or get a couple extra adjuster ***** and just leave them installed).
So you mean you can put extra adjustor ***** on to build it up so it is easier to access?
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Old 07-16-2017, 09:36 PM   #168
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No need. I can touch the top of the shock with my finger tips. Have to do it through two holes behind the fabric inside the trunk. Just plunk an adjuster **** on there permanently and you should be good.

A tiny dot of Loctite blue should keep them from bouncing/vibrating up and bouncing around the top of the shock towers.

I'll know on Tuesday when my ***** come in.

A rotary tool with a sanding or grinding bit to enlarge the holes slightly would probably help. Cutting holes in the fabric is also a good plan.

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Old 07-16-2017, 10:58 PM   #169
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No need. I can touch the top of the shock with my finger tips. Have to do it through two holes behind the fabric inside the trunk. Just plunk an adjuster **** on there permanently and you should be good.

A tiny dot of Loctite blue should keep them from bouncing/vibrating up and bouncing around the top of the shock towers.

I'll know on Tuesday when my ***** come in.

A rotary tool with a sanding or grinding bit to enlarge the holes slightly would probably help. Cutting holes in the fabric is also a good plan.
What happened to the ***** they came with?
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Old 07-17-2017, 06:32 AM   #170
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It only comes with 1. You're supposed to walk to all 4 corners with the one **** and adjust. I'd rather not deal with the risk of dropping my one **** and having it trapped out of reach at the top of the shock tower until I can drop the unit to retrieve it.
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Old 07-17-2017, 01:01 PM   #171
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FYI, barely used set of Ohlin street/track DFVs are posted in the FS area
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Old 07-19-2017, 06:12 PM   #172
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It only comes with 1. You're supposed to walk to all 4 corners with the one **** and adjust. I'd rather not deal with the risk of dropping my one **** and having it trapped out of reach at the top of the shock tower until I can drop the unit to retrieve it.
Do the fronts foul on the strutbrace with the ***** on?
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Old 07-19-2017, 06:31 PM   #173
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I think it just barely fits but I just use a 2mm hex key in the front.
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