SCCA Solo C Street Discussion

[autoXracer]

The Miata's and RX-8 have been modifying bumpstops in stock class for ages. I don't know the science behind it, but aren't those bumpstops designed for specific spring rates?

[qoncept]

Originally Posted by autoXracer

The Miata's and RX-8 have been modifying bumpstops in stock class for ages. I don't know the science behind it, but aren't those bumpstops designed for specific spring rates?

Is there a really an allowance in the rulebook for modifying bumpstops in stock class?

I came around to the sport shortly after STX was created and the stock class rules didn't make much sense to me for a long time. Why race tires and struts in a STOCK class? It didn't dawn on me at the time that you can basically replace any wear item, and that tire treadwear rating was never a consideration until STX was created.

...but what's up with the swaybar allowance?

[7thgear]

there is no science behind it


they are not magical mushrooms


a "bump stop" is simply another spring, except that its not made of metal and is extremely progressive in its rate.


it solves a very real problem with relative ease and ridiculously low cost.... having a car comfortable over bumps while not rolling over on itself in corners.


if one was to tune with bumpstops, then you simply install bumpstops that either offer more resistance, or more linearity, or less resistance, or those that sit higher, or sit lower, etc.


think of it as a secondary spring and all the mystery will be dispelled




as for stock rules, you can do anything you want with your bumpstop (even go so far as to replace it with a zip-tie.. autstintx or dwx? :o) except have it engage sooner than the stock one does (which actually would yield the most benefit)


I suppose a bumpstop that is stiffer but more linear would be an advantage to our cars, but someone has to make them first.

[vroom4]

Couldnt you just get raw materials from mcmaster carr of different density and test them? Not like its a hard geometry. I dont think Im on the bumpstops 99% of the elements, so Im not sure it would help.

[7thgear]

Originally Posted by qoncept

...but what's up with the swaybar allowance?

it's a very fair way of letting drivers of stock cars reduce some of the pains of driving a stock car (by changing the f/r spring ratio) without giving them any real advantage.

[7thgear]

Originally Posted by vroom4

Couldnt you just get raw materials from mcmaster carr of different density and test them? Not like its a hard geometry. I dont think Im on the bumpstops 99% of the elements, so Im not sure it would help.

we've been over this
http://www.ft86club.com/forums/showp...postcount=1084

you're most definitely on the bump stops in some capacity during normal operation of the vehicle, let alone 1g transitions.


it is designed as such

[vroom4]

I know YOU have come to a conclusion, and Im not really interested in arguing it. I will do my own testing, not just math, next season when I have to pull off my konis for a rebuild.

[7thgear]

ya'll really hate math ehh




when it comes time to upgrade/change my dampers i'll stick a go-pro in my wheelwell and run without the dustboots, that will be definitive proof.

[xwd]

You can't lengthen the bump stops but you can make them stiffer which is what Miata guys do especially since the suspension is so damn soft from the factory.

In running CS on Hoosiers last year I ran the MCS shocks with no bump stops and used the zip tie method to figure out where I was ending up, and there were only a couple courses where I would have been on the factory bumpstops, given where the zip tie ended up. That is also on a fairly bumpy Turner Field lot.

The FR-S with its softer front springs maybe would hit them more, but it's hard to say.

I have no doubt people are hitting the bump stops from time to time, but nothing like a Miata which is basically designed to ride on them all the time.

[mla163]

Miata suspensions are extremely soft compared to the twins.

[TrqlessWonder]

Originally Posted by qoncept

Is there a really an allowance in the rulebook for modifying bumpstops in stock class?

...but what's up with the swaybar allowance?

Yes, there are allowances for bumpstops. It's not as completely wide open as shocks/struts are.

As for the swaybar, that's more of a historical item, iirc. Back when any kind of swaybar allowance was introduced, it was not unusual for a car to not have a sway bar of any sort at either end. Some of the faster cars coming out had a front bar, so they opened it up for parity. Adding in the possibility of a rear was more of a nod (rules creep) to the FWD types, as the (more) common swaybar adjustment is at the front for RWD and at the rear for FWD/AWD, so only being able to do the front didn't give FWD cars much options, other than disconnecting or trying to find a smaller front bar. It's almost a moot point now, but a couple of years ago, FWD and RWD in the same class used to be a regular matchup, and it kind of sucked that the Genesis that was cleaning my clock in GS could get real benefit from a bar, but my Civic really couldn't. Also a common situation in the old DS before they reclassed all the RWD cars to FS.

[TrqlessWonder]

Originally Posted by Kido1986

This is JUST for fronts mind you, it will cost additional to convert your Koni rears (or purchasenew ones already converted). Lee from Koni is a well respected member on RRAX and does great by everyone who he talks to.

Haven't met him myself yet, but yes, Lee's reputation is three steps beyond impeccable. I did a quick look around, and my initial estimate is in the ballpark for a full set. ProParts will convert them to doubles for $400 a corner. So, start with a $900 set with the fronts as full struts, add $1600, and voila...$2500-ish. Not exactly cheap, but you could do worse.

I'll just take credit for multiple years of not being on Hoosiers anymore. Yeah, that's how I'll trick myself into it...

[jdrxb9]

Originally Posted by TrqlessWonder

...
As for the swaybar, that's more of a historical item, iirc. ... only being able to do the front didn't give FWD cars much options, other than disconnecting or trying to find a smaller front bar. ...

All true afaik - in my previous autocrossing go-round, a lot of folks ran base model (thinner) front swaybars on our Neon ACR's - so nice to now have an auto-x car I don't have to worry about putting on 2 wheels!

[Biggins]

I know there are some Nationals recaps scattered throughout, but I'll try to be quick with mine. My car was the fastest orange C-Street FR-S at Nats!
@7thgear would probably be proud since my co-driver and I used a borrowed Solostorm for data for the first time ever. However, it was too confusing and never allowed me to focus. I'd consider using it for a test-n-tune, but never again at a big event. The only thing it showed was that my co-driver have different driving styles that both work and garner the same times.

I did not change a thing on the car all weekend and it felt great: 235/45/17 Hankook RS-3 at 32F/28R, Konis at 0.5 turn from stiff front, 0.5 turn from soft rear, Perrin 19 bar at stiff setting.

We peaked at the practice course on Monday probably because the times didn't matter. We both did a couple sessions and were consistently in the mid 41s with a couple high 40s on the quicker layout. The car was loose but good. I was happy with my pace considering this was my first time autoxing on concrete.

Day 1: My co-driver and I both laid day our fastest runs on the first run that would have put us both around 15-20th, but cone. Neither of us could get the finish right on our last two runs, so we ended up mid-pack (27 & 38). We both definitely had a run in the 61s but could not get the finish right. The car was not the problem.

Day 2: I think the better gearing from using the 235/45s helped my car, but the course did the FRS/BRZ no favors. I both overdrove and underdrove, and I fell back to 31st with no runs with which I was happy. However, my codriver had the 4th fastest time for a FRS/BRZ (66.4) on day 2 despite a moment in a sweeper. He moved up 8 spots to slot just ahead of me (grrrr). We were both disappointed, but I'm glad I made the nearly 18 hour drive.

I do not know what is next... I sticking with CS for now, but I do not think this is THE car for the class. The only changes I have listed are tires (and I don't know my answer yet) and potentially some RPF1s. I might also get my own GoPro. I have about four more events before it gets cold, then the long offseason begins. Hopefully, some house projects will distract me enough.