SCCAForums.com

Discussion on suspension springs is now up:

http://grmotorsports.com/news/category/project-cars/other-cool-cars-hanging-around-the-grm-office/1992-miata-sts2-project/

--Andy

Wonderful stuff! I'm glad I'll be able to step in an join a spec Miata STS2 class with ease when I finally kill the Contour.

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-Philip Maynard

No weenies!

Andy Hollis wrote:

Discussion on suspension springs is now up:

http://grmotorsports.com/news/category/project-cars/other-cool-cars-hanging-around-the-grm-office/1992-miata-sts2-project/

--Andy

what are the motion ratios of a miata? this pogo effect you're worried about was not evident in chang's STX car (600+lbs/in wheel rate) or in my STS car ( 400+lbs/in wheel rate). yes, the tire was a major factor in overall spring rate, but even the soft mx's had no problem. once i got to the point where tire's spring rate was softer then the main spring's rate i discovered that the only side effect was the car became more sensitive to tire pressures. with DA shocks, i don't think you need to worry about "over springing" the tires at all. evidence thus far suggests that it makes no difference.

nate

ps. the only time i noticed the pogo effect was one winter just after putting the snow tires on. i only had about 25psi in them. the car felt like a basketball going down the road. bumping the tire pressures up to the high 30's fixed it.

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Nate Whipple
NER
188/88 DSP ITR

Andy,

I have a few questions if you don't mind answering them...

What bumpstops are you using and how much did you cut off of them?

What ride height did you run on the 700/450 springs in CSP and are you expecting to run the same ride height in STS2?

 

Thanks,

Geoff

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90 Miata/89 CRX - STS2 #90/190

solo-x wrote:

[

what are the motion ratios of a miata? this pogo effect you're worried about was not evident in chang's STX car (600+lbs/in wheel rate) or in my STS car ( 400+lbs/in wheel rate). yes, the tire was a major factor in overall spring rate, but even the soft mx's had no problem. once i got to the point where tire's spring rate was softer then the main spring's rate i discovered that the only side effect was the car became more sensitive to tire pressures. with DA shocks, i don't think you need to worry about "over springing" the tires at all. evidence thus far suggests that it makes no difference.

nate

ps. the only time i noticed the pogo effect was one winter just after putting the snow tires on. i only had about 25psi in them. the car felt like a basketball going down the road. bumping the tire pressures up to the high 30's fixed it.

You may be right, Nate (I hope so).  Your experiences certainly make theoretical sense, and one can't argue with empirical results (unless they just like to argue!). 

Motion ratios on the Miata, in round numbers, are .7 F and .77 rear.  But I did not measure those myself.  That's second hand info from Stan Whitney.

--Andy

GChambers wrote:

Andy,

I have a few questions if you don't mind answering them...

What bumpstops are you using and how much did you cut off of them?

What ride height did you run on the 700/450 springs in CSP and are you expecting to run the same ride height in STS2?

 

Thanks,

Geoff

The bumpstops are what remains of my OE 92 factory rubber ones, cut down to about 1/2" thick.  But don't take this for gospel for your car.  As I said in the article, the goal is to make it so that the bumpstops come into play (and protect the suspension parts) just before the suspension contacts the chassis, or shock bottoms out, which ever comes first.  To find this point, you must remove the springs and bars, loosen the a-arm bolt to allow free rotation, and move the suspension through its full range.  A tie wrap on the shock shaft will be helpful in finding the desired bumpstop contact point.

As for ride height, I measure that directly on my shocks so that's probably not useful to you.  And I'll probably have to run higher anyway due to taller tires.

--Andy

I figured you would need a little more ride height for the taller tires. Thanks for the tip on the bumpstops!

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90 Miata/89 CRX - STS2 #90/190

Andy-

I still don't see you registered for the San Diego Tour or the Fontana ProSolo.....how's the project going? 

-JW

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*Banned Again* Permanently

STS3gCivicSi wrote:

Andy-

I still don't see you registered for the San Diego Tour or the Fontana ProSolo.....how's the project going? 

-JW

Motor still at the shop.  Header is on its way here.  Have all the VLSD diff parts, just need to put them together and on the car.  Have a bunch of stuff that has to go back onto the car to be legal (seat belts, seats, soft top, etc.).  Probably a week's worth of dedicated work, but it will have to wait 'cuz I'm off to the convention tomorrow and heading out the door Monday with the Civic to run Ft Myers (regional double-header and the Tour).

I'll register when I get around to it. 

--Andy

PS: Did tire testing last weekend (on the Civic); learned a lot; article to follow soon

Here's the latest, this one on sway bars:

http://grmotorsports.com/news/022006/sts2-miata-anti-roll-bars.php

Got a message from ART today...motor should be done this afternoon!

Hmmm...leaving for CA in exactly one week.

I feel a thrash coming on!

--Andy

Andy Hollis:

Got a message from ART today...motor should be done this afternoon!

Hmmm...leaving for CA in exactly one week.

I feel a thrash coming on!

--Andy

Nice! 

So what time at Steve's, and how much beer are you providing?

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-- Drew
AS S2000

alvanderp:

Andy Hollis:

Got a message from ART today...motor should be done this afternoon!

Hmmm...leaving for CA in exactly one week.

I feel a thrash coming on!

--Andy

Nice! 

So what time at Steve's, and how much beer are you providing?

Actually, all the work will be done at my place.  Call me if you are serious.  I'm cleaning up the place right now and unearthing the car (I think you know what I mean...), so I probably do the motor install tomorrow.

--Andy

alvanderp:

Nice! 

So what time at Steve's, and how much beer are you providing?

Working on Andy's car won't make you any faster, and you will still buy me chicken.

 

And to Andy: Can't wait to see this thing in action!

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-Chad
Texas A&M Sports Car Club
LT4 Track Project
http://www.mowhineracng.com

Andy Hollis:

alvanderp:

Andy Hollis:

Got a message from ART today...motor should be done this afternoon!

Hmmm...leaving for CA in exactly one week.

I feel a thrash coming on!

--Andy

Nice! 

So what time at Steve's, and how much beer are you providing?

Actually, all the work will be done at my place.  Call me if you are serious.  I'm cleaning up the place right now and unearthing the car (I think you know what I mean...), so I probably do the motor install tomorrow.

--Andy

Same reaction, different forums.  Though, I'm not available 'til Thursday night, rumor has it there is an event in CS for test time... =P

Same pay scale? =P

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Zack
# Whatever
Car: Who ever'll hand me the keys

mtbprelude:

Same reaction, different forums.  Though, I'm not available 'til Thursday night, rumor has it there is an event in CS for test time... =P

Same pay scale? =P

CS is the stretch goal.  If I can at least get the thing running, I can shake it out there. Finish doing the removal of CSP stuff early next week.  TEC3 is now out.  I'm cleaning the engine bay right now...

--Andy

Andy Hollis:

mtbprelude:

Same reaction, different forums.  Though, I'm not available 'til Thursday night, rumor has it there is an event in CS for test time... =P

Same pay scale? =P

CS is the stretch goal.  If I can at least get the thing running, I can shake it out there. Finish doing the removal of CSP stuff early next week.  TEC3 is now out.  I'm cleaning the engine bay right now...

--Andy

Stretch goal = achieved!

Ran the car today, albeit on suboptimal tires since I was too lazy/tired to change 'em and load up the trailer this morning, after the previous evening's last-minute diff thrash.  Actually drove the car 1.5 hours to the event.  Just like the good old days.  Drive in, put on helmet, race, drive home.  Nice.

Car still has a totally stock exhaust and intake.  I'll tackle the exhaust tomorrow.  Time to melt some metal!

--Andy

PS: This last week has been quite the thrash.  Details to be written-up when I get a chance.  Some very entertaining moments... ("Oh look, I just dropped the diff onto the concrete floor..")

Andy Hollis:

Car still has a totally stock exhaust and intake.  I'll tackle the exhaust tomorrow.  Time to melt some metal!

Are you 100% retired? I need more time to play! (of course if I didn't spend so much time working on this site lately I could be playing )

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I am Chris Hammond.
Going2Colorado.com

Andy, will this car run at San Diego, or are you codriving a different car?

Andy Hollis:

Just like the good old days.  Drive in, put on helmet, race, drive home.  Nice.

I love that aspect of it. No PITA of a trailer and tow vehicle, and an ST car is just a lot of fun to drive on (smooth) public roads. I'd imagine this is going to be a great summer cruiser when you're done, even if it's a bit stiff and loud.

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-Philip Maynard

No weenies!