Well as Lady Luck would have it, came up about 1mm too small for the slot opening at the top for my initial selection to fit.





I don’t see anything in the DSP class rules that allows modifying the slot and fortunately I found a 0.25” smaller OD option after ordering this material. So rather than monkey around with trying to oval or taper the top slightly, ordering that option instead seems like the prudent thing to do. Should still have enough internal clearance. I likely would have done this instead, but had presumed that it was a non-standard size and not readily available.

... and this gives you an idea on what is needed for the gas bolt clearance, which the 2812 Koni is a 2mm smaller OD body with a smaller head gas bolt that’s countersunk with no protrusion. So it cleared without issue, but must have been close.

 

autocross has some pretty ridiculous rules. actually scca in general.

that shock body looks like a very tight fit for the stock rear shock caps, even if the gas bolt wasn't there. probably not enough room for the shock body to move side to side with suspension travel.

 

Well in that position the body is pulled all the way over to the bottom opening just for obtaining an indication of maximum clearance. In reality it doesn’t get that close to using the full opening, but does get close enough that you’re just better off accounting for full clearance and having peace of mind. You also have to remember in the OE non-inverted configuration the body never gets that high in the mount even at full compression due to the way it mounts with the bushings and also the 3” long bump-stop that compresses a good amount, but not fully to nothing.

The new size needed is a pretty crazy price in stainless steel due to the odd size not being so popular. Steel DOM is like 10x less instead of the more typical 3x or so. While I would have preferred stainless for not needing to paint it etc. it makes more sense to go with steel like OE, which is easier to fabricate along with the substantially lower cost. This slightly smaller diameter will also make including the top chassis bracket mount easier to accomplish. It will all work out ok, just need to execute now that the path is clear.

otherwise I understand how it seems that way, but rule allowances are not always so clear cut as how people will use them for a competitive advantage. So you think it’s just 1mm, but somebody might use it to cut out 10 lbs somehow. Which is just an extreme example to make a point. The limit has to be drawn somewhere relative to what level of preparation is allowed. In the next higher prep level I could just cut or grind that area out to make it fit, just not at this prep level. In reality it doesn’t matter what organization it is; SCCA, NASA, and so on. You can make the same claim in any of them, just the point of subject being different is all.


.

 

if the shock body is mounted to the spherical bearing, what's the chance of the shock body rotating within the rear shock cap. ie when you're adjusting the spring perch or just from the shock travel. i guess the bottom spring perch should be stationary so that would keep the spring and the top perch in one spot, unless the spring unload completely even with the helper spring.

 

Maybe you don’t understand; with the new top section that issue goes away. That’s why I didn’t just cut a window in the OE top along with making a prayer for it not to move. Because if it did the end result is not good; bent shaft, blown seal, damaged body are all likely, in addition to inconsistent/bad handling in the turns. I only cut the window in the OE top to remove the upper chassis mount bracket for the new top piece to slide over for a fitment check along with verifying the actual clearance needed to back up my geometry calculations. So when this is done the top 3/4 or so of the mount will be a straight larger OD tube and flat top rather than tapering most of the way like the factory top piece. It will have full clearance for the gas bolt in any position. Won’t have to give it any second thought.

 

lol, yeah i understood exactly what you were doing. but i had thought of just cutting a hole for the gas bolt but now thinking the shock body can rotate, that's a no go then.

 

It was discussed with you several months ago in this same thread

 

Install my MCS
Good product
Overall straightforward on front , but runing into some small issue on rear as u can see rear shock shaft is 2mm bigger then stock !!! Not big deal
But I think this should inform headup and the spring holder should have better design then this

 

i can't tell if the rear spring cup is plastic or delrin but if you want aluminum, here's a good option.

https://www.sakebombgarage.com/fpspe...-nc-miata-rx8/

 

Thanks for recomand
I think the spring holder is made from delrin

 

theres a local guy that ran the good-win racing delrin spring cup and he has broken a couple sets already. although he did us them with the metal top hat instead of the aluminum top hat that good-win recommend

 

Lets I am afraid too , cross finger this derlin cup will last event of this year !!!!

 

There are also beehive springs available in certain higher rates that will fit there and eliminate needing those altogether. You won’t have the same fine tuning rate range though. Pretty much 100 lb/in rate changes.

so the material for round 2 on the rear hat mods should be arriving soon. Also in discussion with a company to make the bolt-on aluminum spherical bearing carrier for the top. I’ll probably have some extra sets made, but am not entirely sure if the larger size needed for a 3/4” spherical is going to fit on top of the OE hat top. My thought is to make another set or two of the modified hats and make them available.

.

 

I use the Penske spring cups, but you need to use 2.5" springs. It's pretty thick delrin, and I've tracked and autocrossed with no issues.

 

actually it’s pretty common for adjustable race shocks. Hard to maintain the same small OE diameter shaft end and put a valving adjuster mechanism up through the center of it. Usually 12mm or 14mm is common for race shocks. OE is 10mm. You just have to drill the bushing out. Not too difficult as long as you have the equipment. You really need to have a spherical/pillowball there rather than a bushing though.

can’t quite make out the front spring rate, but looks like maybe 10 kg front and 8 kg rear? Seems kind of light compared to what I thought MCS typically recommends for track use.

.

 

testing MCS 2wNR with new stock 2018 275/35/18 dunlop Z3

love how car response well with just 1 single click
i was having too much oversteer at apex so i soft rear bump 2 click
and i dial in one more click on front rebump for 1 slick to what i like the car to handel

what i dont like is rear ride high is too high with spring perch all the way to button

after all i improve almost 2.5 sec today compare to my mazdaspeed shock and spring set up with nankang AR-1 happy for the result. i thinik i can do better with more seat time

 

Well here’s the deal with that:



Part of the issue with these adapters is the assembly height, which takes away from fitment space of the spring assembly. The inverted shock setup allows trimming the tube extension out the bottom of the OE mount all the way back to the weld surface. This provides about 3/4” or so more fitment length for the spring/perches. Which you can see on the pic above that you could have at least trimmed that some to get the delrin adapter down flush to the mount flat surface. Anything you gain there is going to allow for a lower ride height with the same total spring length.

However, if I were going to run this type of setup, I’d cut that protrusion all the way back to the weld, then have a new adapter perches machined out of carbon or stainless steel for the shortest fitted length possible, and instead stitch weld it to the mount surface to provide the maximum amount of spring fitment space. The adapter perch doesn’t need to be removable unless you intend to convert the mount back for an OE spring, which most racers are never going to do.

 

yeah we modify the rear top hat to spring cup. i didnt like any of those conversion adapter. you also have some extra height because of the tender springs. even when fully compressed, its still almost an inch tall with the adapter between the two springs.

https://www.rx8club.com/rx-8-racing-...6/#post4855335

 

Must have missed that, looks good. If the shock is dimensioned properly there should still be enough room for the tender spring. I’m convinced to use tenders rather than zero helpers. You can likely get shorter ones, but it will diminish the benefit imo.

 

^- That's what I did, except the rings I used to capture the spring are inside the spring inner diameter. With a 6" long spring, I have a ~ 150lb rate assist spring with something like a 25mm block height and I have no issues getting the rear ride height where I want it.

 

Thanks for sharing I think I will find another top hat for this project

For design of Rx8 runing tender spring is benefiting


Cool , right now ride high rack ratio is wack
Due to the rear ride high

 

Perhaps it was lost in translation ~~~

what length you can get away with depends on rate and shock dimensions. You need enough spring length not to coil bind at full compression. John V is not running MCS shocks. His spring rate is quite a bit more than yours appears to be and he has much shorter Penske shock than what you have. That will accommodate a shorter spring before coil bind. I’m thinking you might need at least a 7” spring, but it’s hard to be sure without verify the full dimensions.

Did you understand that at least part of your ride height issue is that the rear OE shock mounts need to be modified where the delrin spring adapter sits?

based on my own experience with cycling the rear suspension with the shock mounted without the spring and observing how the shock position/angle changes throughout the travel, I have to think that the shock body is contacting/rubbing against the inside collar of that adapter in some situations.
.

 

Swift spring had less coil, then other spring
So binding will not be a issue

I am aware my rear ride high issues is from
Spring adapter, will build a some thing similar like truck junkies

Theird around 11 years ago I was working for a gram am team who race NC Miata and rear shock get contact in upper mount

 

Ok, wasn’t intending to question your skill or experience. Sometimes the language difference makes it unclear if we understand each other clearly.

 

No problem
You guys,know more Rx8 then me
I just love track and rotary engine in general !!!