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PostPosted: Fri Dec 19, 2014 1:01 pm 
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I have a minor dillema I am pondering. I built my Locost to be a comfortable street car. The wheel rates are around 180lbs/in on a 1,350 lbs car (that's total weight, probable 1,150 sprung weight). I am an avid autocrosser and regularly run my ES 1999 Miata. I do wish to try competing in my Locost. It is by no means is a DM car, but we have a local Street Unlimited class which it would be fairly competitive in. I would like the ability to quickly and effortlessly boost the coilover spring rates by at least 100lbs. Any ideas on how I could do that? I have traditional outboard coilovers on the front, and the entire Miata subframe on the rear. I have the stock Miata sway bars attached front and rear. I have tried an autocross but the ride was too soft, but to be fair that was prior to the front sway bar install. So far I am scratching my head at:
1) some form of pushrod system in parallel to the coilovers, but don't think I have the space or the willingness for such a complicated modification.
2) a torsion bar addition that could be attached somehow
3) a redneck solution of a rubber infill to jamb up a few of the coils on the springs, like you can buy for towing a trailer
The solution needs to be switchable so I can drive to and from the autocross, and not wreck my back with a hard ride.
Any thoughts?
Thanks
Martin


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PostPosted: Fri Dec 19, 2014 1:17 pm 
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Martin,
I would spend more time on the sway (roll) bars. When I raced FF, all the cars had adjustable roll bars, and we would disconnect them completely for running in the rain. You only need to remove one vertical link for that. The hotter cars would have cockpit adjustable roll bars front and rear, for fine tuning as the track conditions changed. It was actually a fairly simple set up with a push/pull cable, a detent lever in the cockpit and one vertical link attached to a sliding block. Not that hard to fabricate, and you may find it useful for what you are trying to do.

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PostPosted: Fri Dec 19, 2014 1:29 pm 
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Thanks Martin,
I have been wondering where the cut off point might be in terms of just going with a massive sway bar (and disconnecting for the street driving), and having to face the reality that I need a higher spring rate. I was erring on the sring rate adjustment as I have the sway bars from a Miata, being a much heavier car. I did think of adding another stock Miata bar as I have one lying around....but was thinking that was too radical. I guess it would be proof of concept though.
Martin


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PostPosted: Fri Dec 19, 2014 1:34 pm 
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Even softly sprung a Locost is an awesome autocross car. The weight is what makes the difference, but are you trying to be nationally competitive or just better than some guys you know who run at the events you attend?

I run my rear sway bar on the streets and disconnect it when I autocross my S2000. It's a very simple one bolt removed and add a zip tie procedure that I do in 5 minutes or less.

So doing that in reverse and having a very stiff sway bar for the course and disconnecting it for the drive home would seem like a simple solution.

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PostPosted: Fri Dec 19, 2014 5:21 pm 
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carguy123 wrote:
... I run my rear sway bar on the streets and disconnect it when I autocross my S2000...

I've always found the opposite, that the end of the car with the bar slides more easily, so I had a big rear bar for autocross to help the car rotate and disconnected it for high speed track events.

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PostPosted: Fri Dec 19, 2014 5:26 pm 
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KB58 wrote:
carguy123 wrote:
... I run my rear sway bar on the streets and disconnect it when I autocross my S2000...

I've always found the opposite, that the end of the car with the bar slides more easily, so I had a big rear bar for autocross to help the car rotate and disconnected it for high speed track events.


Yes it depends upon the car and how it's set up.

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PostPosted: Fri Dec 19, 2014 6:21 pm 
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On my open track/street car (65 Mustang), the only change made to street drive it is to reduce the rear shock setting from 5 (full hard) to 3 (medium). Setting 5 on the street will rattle your teeth out, but softening the rears smooths out the ride completely. It's not a locost approach, but you may want to consider what adjustable shocks could add to the different ride settings you are after.


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PostPosted: Sat Dec 20, 2014 2:26 am 
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On my open track/street car (65 Mustang)


Nice, :cheers:

I've seen some type of bump rubber kind of thing that actually fits on the coils or maybe between the coils. I found them will searching for bump rubbers.

I think you should be able to find a good compromise on spring rates, unless you are running slicks or something. Do you raise and lower the coilovers for events or have a spare set of wheels for different tires?

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PostPosted: Sat Dec 20, 2014 8:10 am 
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I've seen some type of bump rubber kind of thing that actually fits on the coils or maybe between the coils. I found them will searching for bump rubbers.
Iffen y'all watched NASCAR like good little rednecks are trained to from birth, you'd know those are "Spring Rubbers" that they put in between coils on the springs. It limits movement and decreases the number of "free coils" to stiffen the car.
http://www.speedwaymotors.com/Shop/Open-Wheel-Coil-Spring-Rubber-Inserts/15.html
Hassleweed, I don't know if they'd do the trick for you, but they'd be quick and easy to install and fairly cheap...

:cheers:

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PostPosted: Sat Dec 20, 2014 10:10 am 
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Adding some more detail to Marcus' question about running a different set of wheels/tires:
I've seen mention of 13" wheels fitting early Miata rotors/calipers. If 13's will fit your suspension and you can run Hoosier A6s, their 13" tire is just under 21" in diameter. This will lower the CG and improve the handling in addition to any other suspension adjustments you make. (Don't know if there would still be adequate ground clearance.)

As carguy123 says, a stock 7 can be very competitive. Before Lotus 7s were outlawed in A/SP, I drove one to a ProSolo class win with the only change being a set of Pirelli P7s on the 13" wheels with an OD of less than 21". The lower CG being the key.

Ron


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PostPosted: Sat Dec 20, 2014 12:32 pm 
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Thanks for the feedback guys. I'm all for trying the redneck solution, thanks for the link. I'd like to figure out a homemade version as I have less than 3/4 inch gap.
I see how the smaller wheels would make the most significant difference though. I run stock 15 inch Miata rims and sit a good 4.5 inches clear for road use. Coming down 3 inches with the same geometry would be massive. Anyone have a good source for cheap 13 inch wheels?


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