Bump Stops for NC3 Street Autocross class

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Bump Stops for NC3 Street Autocross class

Postby RickM848 » Sun Mar 17, 2019 5:17 pm

Hi Brian,

I’ve just started Autocrossing my stock 2014 MX-5 GT PRHT (with stock Bilsteins), and would like to make some small inexpensive improvements but remain in the Street Autocross class. I’m looking forward to a Novice training class next month.

I’m confused about the GWR Bump Stops recommended for Autocross. I read there were two setups for STOCK Class Autocross 06+ MX5s: 58mm Red Soft front, 58mm Medium White rear, AND Racing Beat front sway bar, or the Medium Front and Hard Rear with the Racing Beat front sway bar.

This is my daily driver, and I’d like to improve the turn in rotation and reduce understeer but not destroy the ride. I’d probably have a local shop install these, the sway bar and an alignment - suggestions for the alignment would be appreciated too!

Thanks!

—Rick
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Re: Bump Stops for NC3 Street Autocross class

Postby RickM848 » Sun Mar 17, 2019 5:36 pm

I’m even more confused. In Street class do you have to run an aftermarket shock to be able to change the bump stops, or is it legal to do with the stock shocks?

—Rick
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Re: Bump Stops for NC3 Street Autocross class

Postby Brian » Mon Mar 18, 2019 10:33 am

Nothing you can do legally to Street class car is going to destroy the ride, I am baffled that anybody worries about that, the medium rear stop is to help balance the front bar but the impact on ride just driving around and not tossing the car hard enough to get deep in the stops is insignificant. I drove our ND2 to work today with medium hard rear stops, setup for CS with stiff front bar, rides like stock car or even better (since we are on KONI instead of stock Bilsteins). Again, driving in a straight line you are not getting deep in the stops, just floating above them with KONI set to soft giving you really nice ride.
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Re: Bump Stops for NC3 Street Autocross class

Postby Brian » Mon Mar 18, 2019 10:35 am

RickM848 wrote:I’m even more confused. In Street class do you have to run an aftermarket shock to be able to change the bump stops, or is it legal to do with the stock shocks?

—Rick



In SCCA 'Street' you can change the stops with stock shocks or aftermarket, but pretty much everyone wanting to be competitive goes with our KONI Sport shocks for numerous advantages in performance over the stock shocks. First, the lower pressure koni lower the car a bit, gives you a lot more negative camber which you really need to get the tires on the ground in the turns. Second, the Koni are adjustable so they further help us re-balance the car with the screwed up SCCA Street class rules that allow us only one sway bar change. Third, when the KONI rear set to full stiff and the car driven aggressively the KONI can actually 'jack down' and sit on that stiffer rear stop a little which further helps balance the front stiff sway bar pretty well (with front KONI set much softer, I did 1.5 turns from stiff at the front and never touch it, rear KONI goes to full hard for autocross events and I dial it full soft as soon as event is complete.).
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Re: Bump Stops for NC3 Street Autocross class

Postby RickM848 » Mon Mar 18, 2019 11:02 am

Thanks Brian,

I think I'll just get an alignment right now and work on improving my driving this year, then plan on upgrades next season. So many things to consider.

--Rick
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Re: Bump Stops for NC3 Street Autocross class

Postby RickM848 » Fri May 31, 2019 5:06 pm

Brian,

I ended up getting the KONI adjustables, and installed them with front red 58mm bump stops, and rear white 58mm bumpstops with 15mm of packers, RX8 red dot FSB, and new wheels with RE71R’s.

Wow! I had no idea the change would be this dramatic!

Thanks for your advice!

—Rick
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Re: Bump Stops for NC3 Street Autocross class

Postby Brian » Fri May 31, 2019 5:19 pm

Glad that is working out, have fun at next event!
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Re: Bump Stops for NC3 Street Autocross class

Postby RickM848 » Sat Jun 01, 2019 2:05 pm

Brian,

The left rear KONI appears to be leaking oil where the two double nuts secure the top washer/rubber bushing.

—Rick
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Re: Bump Stops for NC3 Street Autocross class

Postby Brian » Sat Jun 01, 2019 5:27 pm

RickM848 wrote:Brian,

The left rear KONI appears to be leaking oil where the two double nuts secure the top washer/rubber bushing.

—Rick



Send us pics, usually just the assembly lube gets pushed out of a new shock.
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Re: Bump Stops for NC3 Street Autocross class

Postby RickM848 » Sun Jun 02, 2019 1:48 pm

The oil that leaked was clear. It was all over the adjuster and my fingers when I adjusted them to near full stiff for today’s Autocross, and again when I set them to 1 turn from full stiff for the ride home. I went out a minute ago to take a photo and the adjuster shaft was dry, so I hope that was the end of it.

The RX8 red dot front sway, KONIs adjusted as you recommended with red 58mm front, white 58mm with 15mm of packers rear,, and RE-71R’s at about 28F/30R (measured hot on an 85 degree day) was such a tremendous improvement on the track! I had started out with too much tire pressure but now have a starting point to work with. The car rotated very well and I’m super happy with the setup!

I’ll report back if the shock continues to leak.

Thanks Brian!

—Rick
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