Altering the ride height - is it that big of a difference?

[Gerry]

One of the classing rules that really stands out to me is that the minute you alter your ride height from stock in any way, you're now in the modified class. So how much of an advantage do stiffer and shorter springs really give?

[Loren]

Depends on the car and on how well-engineered the lowering and stiffening is.

It's certainly not as easily quantifiable as tires, where we can say "the difference between really good summer street tires and all-season tires is about 2 seconds on a 60-second course, and race tires are 1-2 seconds faster than that". If you start with a car that already has good suspension and proper ride height, the gains from lower and stiffer springs will be less than doing the same to a car that has a lesser factory suspension. And, in either case, choosing the wrong spring rates, ride height, bump stops, swaybars, shocks, etc... can easily make the car handle WORSE than stock.

But, that's where we chose to draw the line on suspension mods in stock because it's fairly easy to monitor. It's a simple litmus test.

[jev61]

If you can lower your ride height without altering or changing your springs you may find an advantage because a Miata gains negative camber with a lower ride height.

When I converted my car to the Sport Package option, I tried three different shock combinations until I found the set that gave me the lowest ride height. A stock Miata is often limited to ~1.2 degrees of negative camber up front, a Maita with height adjustable coil overs can offer you double that much negative camber up front.

You can also Google center of gravity and weight transfer to learn more. And Loren's excellent series of suspension articles explains these things very well.

[blacksheep-1]

If you lower your new edge or SN95 Mustang without changing lower ball joints you might as well kill yourself.

[Jamie]

...that's where we chose to draw the line on suspension mods in stock because it's fairly easy to monitor. It's a simple litmus test.

Replacing springs, which is measureable, or ride height, which is not? Certainly, you can measure a car's ride height, but there is no factory figure to compare it against -- or at least not one in any factory shop manual for any of the cars parked at my house. It's a measurement with a subjective tolerance. Under FAST rules, I can run a 13" wheel with the lowest profile tire possible and degass the shocks...all legal, unless someone comes along and arbitrarily decides I've exceeded a "factory tolerance" that doesn't exist.

[Loren]

...that's where we chose to draw the line on suspension mods in stock because it's fairly easy to monitor. It's a simple litmus test.

Replacing springs, which is measureable, or ride height, which is not?

Both. The bit about ride height is in the rules to keep people from getting sneaky and messing with spring perch height and other means to lower the car without "changing the springs".

But, that's not the question that was asked here. The rule isn't being questioned. The value of altering ride height is being questioned.

[jev61]

...that's where we chose to draw the line on suspension mods in stock because it's fairly easy to monitor. It's a simple litmus test.

Replacing springs, which is measureable, or ride height, which is not? Certainly, you can measure a car's ride height, but there is no factory figure to compare it against -- or at least not one in any factory shop manual for any of the cars parked at my house. It's a measurement with a subjective tolerance. Under FAST rules, I can run a 13" wheel with the lowest profile tire possible and degass the shocks...all legal, unless someone comes along and arbitrarily decides I've exceeded a "factory tolerance" that doesn't exist.

I can't speak for a '01 Miata, but the Factory Service Manual for my '99 lists ride height ranges front and rear.

When I suggested lowering without changing or altering springs, I didn't mean to suggest lowering the spring perch as NA Koni's allow. I was referring to my experience using different shocks, as the factory Hard S Bilstein's raised my ride height about .5 inch more than the Koni's or Tokico's. I measured the lowest ride height with my original worn out Soft S shocks.

[Gerry]

The rule isn't being questioned. The value of altering ride height is being questioned.

Yes, this exactly.


Thanks, all, for the input. I guess one very hard to answer question would be this mathematical equation:

Lowered car + stiffer springs = x seconds faster
^^ solve for x

?

[Jamie]

Both. The bit about ride height is in the rules to keep people from getting sneaky and messing with spring perch height and other means to lower the car without "changing the springs".

But, that's not the question that was asked here.

You brought it up:

...that's where we chose to draw the line on suspension mods in stock because it's fairly easy to monitor. It's a simple litmus test.

So I asked. And since Joe's FSM actually has ride heights, it's not subjective for a '99. Interesting that the later FSM doesn't have it. Nor does it have a spring perch height -- so unless you do like SCCA rules do, and declare it must be in the same relative position on the shock body as a stock perch, there's still nothing to say when a difference is too much.

I'm pushing the point because you're stating there's a "simple litmus test" when it's not necessarily true.

Lowered car + stiffer springs = x seconds faster
^^ solve for x

There's not a modification out there that comes off that cleanly. Even the "2 seconds per 60" rule of thumb for R-compound tires is just that -- a non-statistical aggregate observation. Using the same method, it's been my observation over time that an SCCA ST car seems to be about the equal of the same car prepared to Stock rules -- thus, well-matched springs, shocks, and sway bar atop street tires seem to be worth about the same as R-compound tires on a stock suspension, or 2 seconds per 60 over a stock-suspension car on street tires. Even more so than the tires, though, that's course- and driver-dependent, and with no statistical rigor behind it. YMMV.

[Loren]

I'm pushing the point because you're stating there's a "simple litmus test" when it's not necessarily true.

So noted.

[Gerry]

There's not a modification out there that comes off that cleanly. Even the "2 seconds per 60" rule of thumb for R-compound tires is just that -- a non-statistical aggregate observation. Using the same method, it's been my observation over time that an SCCA ST car seems to be about the equal of the same car prepared to Stock rules -- thus, well-matched springs, shocks, and sway bar atop street tires seem to be worth about the same as R-compound tires on a stock suspension, or 2 seconds per 60 over a stock-suspension car on street tires. Even more so than the tires, though, that's course- and driver-dependent, and with no statistical rigor behind it. YMMV.

This is exactly what I was looking for. Thanks.

So now it's just a matter of whether or not I'd be willing to daily drive a lowered car (not as low as it was when I bought it) and if I'd want to spend the money. That's for another time in another thread


So in short: yes, lowering your car, in general, gives a significant but hardly quantifiable advantage.

[Loren]

So in short: yes, lowering your car, in general, gives has the potential to give a significant but hardly quantifiable advantage.

Fixed that for you.

The guys Jamie is talking about spend thousands of dollars testing various configurations of suspension parts and settings, wheel and tire sizes and different wheel and tire options. Those are the guys who can ultimately see about the same 2 seconds that you could see by leaving the suspension completely stock and moving to race tires. And the mods they're making are more than just suspension. They also include headers, intakes, ECU mods and various other things that are NOT allowed in SCCA's very strict Stock classes.

I'm not saying you can't or won't see an improvement from changing your suspension. Just trying to temper your expectations. It's not going to just magically make you 2 seconds faster. In a Miata, it's not likely to even make you 1 second faster.

You'll get most of what there is to get out of a Miata with good tires, shocks and alignment... and driving it properly. Maybe a bigger front swaybar.

[nc4me]

You're doing so well in the stock class that I would not change if I were you. I think you should only change if you want the car to be lower for personal reasons (looks or to get rid of some unwanted lean). Otherwise leave it alone. If you do make changes make sure you make informed changes from people that have gone that route so make an improvement in handling. Like Loren stated, some suspension setups can make you slower.

[shakedown067]

Couldn't agree more. Tires/shocks/alignment, stay in stock and keep building seat time (pay no attention to what I'm doing to my car).

[Native]

I just stiffened/lowered my car. I don't think it's helped (yet) and I couldn't swear it hasn't slowed me down. I suspect the limits are higher, and I just haven't figured out how to access them yet.

So I'll second (or 4th) what Loren, Chris and Eric have said above.

[aw614]

What is the deal with lowering the perch on koni yellows? I know some setups had it like on Hondas, but other than lowering the car a bit without springs, does it do anything to impact handling on an otherwise stock car like if the damping settings are the same on both perch heights, but one is lower. And is there any harm and running the stock springs on the lower perch setting?

[twistedwankel]

I have a stock hand pump up lever on my 8's driver's seat that makes the car seem lower and me taller. It also has a tilt wheel so I can pretend it's a bus and I am Ralph Kramden.

I cannot imagine anything worse than a florist (or other unrelated skilled person) thinking they can come up with a better suspension than the automotive engineers can - even tho' they are a very skilled driver who can deliver.

Guess that's why I still run the original struts/springs on my '04 Rx8 with 66k miles on them. If they aren't leaking they must not be built in Washington DC. I did put $240 dampers on my '86 GT including Quads because the original ones were leaking after 123k miles and 25 years I still keep getting a tiny bit faster every time I drive it because there is still more speed in the car than I have mastered. Ask Joe V what happened when I went to 245 tires instead of 225 wide ones on the same stock rims with the original alignment.

I was told the reason that the cars shipped across the ocean are lashed/cranked down is to keep the polished strut shafts from being exposed to the sea mist and getting rust pits which tears the seals making them junk from day one. I don't live near the sea and keep the car in a dry garage.

But what do I know I'm still driving on the factory spec alignments to keep tire wear dead flat even. Virtually no neg front camber or toe changes even tho' allowed. I've opened the Prepared box a few times before and it gets very very expensive. Kind of like a bad marriage.

Old guy's 3 cents.

[Jeremy]

I just stiffened/lowered my car. I don't think it's helped (yet) and I couldn't swear it hasn't slowed me down. I suspect the limits are higher, and I just haven't figured out how to access them yet.

Now you need a turbo. That'll help you "access" the limits.

[snookwheel]

It also has a tilt wheel so I can pretend it's a bus and I am Ralph Kramden.

Old guy's 3 cents.

You gave away the 'Old guy'. With the Krambden reference! Right there with ya

[blacksheep-1]

Code: Select all

There's not a modification out there that comes off that cleanly. Even the "2 seconds per 60" rule of thumb for R-compound tires is just that -- a non-statistical aggregate observation. Using the same method, it's been my observation over time that an SCCA ST car seems to be about the equal of the same car prepared to Stock rules -- thus, well-matched springs, shocks, and sway bar atop street tires seem to be worth about the same as R-compound tires on a stock suspension, or 2 seconds per 60 over a stock-suspension car on street tires. Even more so than the tires, though, that's course- and driver-dependent, and with no statistical rigor behind it. YMMV.

This seems to hold up fairly well, back when we were NASA and you received points for mods the mustang guys would use springs and go to a DOT slick, the S200 guys would run sway bars and a DOT slick (same size and make) and run fairly competitive times. The mustangs would of course, blow through the tires faster because of the weight and live axle issues, but they were evenly matched. We were never really challenged by anyone running race slicks with a stock suspension. Look at the (over 3L) "production race tire class" vs the "modified street tire class" car vs car, the well sorted (and driven) mod car is almost always faster. I'm not sure if that holds true for the under 3L.