What is faster: Lowering a car or getting a set of great performance street tires?

[X12]

I just had a debate with a friend and now am curious what the factual consensus is. I believe that by lowering a car's center of gravity it will be faster than a car that has a pair of great street performance tires; say for instance the Falken Azenis RT-615s. When I say lowered, I mean completely lowered and the best - unless something is better than the 615s - street tires. What do you guys think? Please put some thought into this. Anyone with the knowledge of physics that can explain this, please don't hesitate to chime in.

-X12

[nik]

Tires are the only part of the car that (should) make contact with the ground, and will yield the greatest improvement in my opinion. The job of the suspension is to keep the tires on the ground, and if the tires suck the car will still be slow, no matter how low the car is (assuming its properly lowered with rcas and everything... and then you're looking at ~$2k vs ~$500....)

[Mazda_Gremlyn]

Are you talking lowered with matching shocks and proper springs rates vs really good street tyres? I think a really well set up suspension is worth a lot, but you also have to consider what you are starting from. Are you having traction issues in corners, constantly kicking your tyres loose? If you are on a decent street tyre to begin with, lowering might have the edge when switching to a high end street tyre. If you were talking about switching to full races tyres, it'd be hands down the tyres.

If you're looking for your next thing to do to prep for autox, I'd recommend tyres before suspension. Its better to learn to control the car in stock form with good tyres before you go and play with the suspension, that way you know whether the changes you make cause the car to handle better or worse.

[X12]

Thanks and I'll go ahead and try to clarify a few things. This is not pertaining to autocrossing but just performance driving in general. The two sides are:

1. Lowering springs and decent stock tires and that's it. No shocks, no camber, toe, none of that. Just the lowering springs with adjusted spring rates.

OR

2. Stock suspension with say Falken Azenis RT-615s street tires NOT
R-compound tires.

The scenarios are for the same car. In the case of the debate with my friend, we were talking about a 95 Civic Hatchback.

-Andrew

[froggy47]

I would vote for the tires, but I have no "engineering analysis" to go with it.

You could go extreme low - think of a go kart - but with flintstone tires I don't think you would perform very well.

[freshspecbluegt]

If you're looking for your next thing to do to prep for autox, I'd recommend tyres before suspension. Its better to learn to control the car in stock form with good tyres before you go and play with the suspension, that way you know whether the changes you make cause the car to handle better or worse.

Oh my god, Colin did you write that or did an alien take over your body! Haha just kidding, seasons over I'll take a break from trash talking, we had enough fun with it Saturday.

PS: I love the fact that you spell "tyres" like we're back in the old country. I love the way the colour of your car really comes out when the light shines off your bonnet, plus all of your race tyres fit so nicely in the boot.

Ross

[MX5bob]

Thanks and I'll go ahead and try to clarify a few things. This is not pertaining to autocrossing but just performance driving in general. The two sides are:

1. Lowering springs and decent stock tires and that's it. No shocks, no camber, toe, none of that. Just the lowering springs with adjusted spring rates.

OR

2. Stock suspension with say Falken Azenis RT-615s street tires NOT
R-compound tires.

The scenarios are for the same car. In the case of the debate with my friend, we were talking about a 95 Civic Hatchback.

-Andrew

Lowering springs on their own won't make the car a faster autocross car.

Also, while the springs are lowering the center of gravity, that's not all they're doing. You need to know what's happening to the roll center. Lowering too far will place the roll center too low and hurt the way the car handles.

Then there's bump steer, although that doesn't seem like a huge deal in Solo 2 in SD and SoCal. Maybe in bumpy lots it would.

[X12]

Thanks a bunch guys.

-X12

[Mazda_Gremlyn]

Ceteris paribus, tyres >>>>>>>>>>>>>>>>>>>>>>>>> springs.

And Ross, I already have good tyres, you know the ones that fit in the boot. So of course my next logical step is suspension mods :P Oh and there are NO KONI GROUNDCONTROLs FOR MY CAR :D

[brian]

what kind of street car has to worry about bumpsteer?

[nik]

what kind of street car has to worry about bumpsteer?

The one's that are raced on weekends!

[freshspecbluegt]

Oh and there are GROUNDCONTROLS FOR MY CAR :D

Yeah I know I looked at their website, call them and tell them to make some.:D

[brian]

hard to believe that street cars have bump steer issues with such little wheel travel. care to explain?

[MX5bob]

hard to believe that street cars have bump steer issues with such little wheel travel. care to explain?

What does wheel travel have to do with bump steer? It's a matter of altering the pivot points in relation to the tie rods. Mazda thought enough about it to make a different tie-rod for the '93 LE, which was the lowest model from the factory. The LE wasn't lowered that much either.

Aside from that issue, the orginal question would still get the same answer. Sticky tires are worth more than lowering springs on an a Solo 2 car. In fact, good shocks are worth more than lowering springs. An underdamped spring doesn't do that good of a job adding mechanical grip. Add lowering springs to stock shocks and you've got a poor combination.

[chapmanr]

I can speak from some experience here...go with the tires!

When we first starting axing, the CRX has a full Jackson suspension kit on it already. Nonethless, we never approached respectability until we put on good r compound tires (which were Yoke a008rs, in the day).

As an aside, the Jackson suspension felt good on the street but was fairly awful for an autocross car. Tuner packages often go for stiff (which you can readily feel at any speed) over real performance. Best to consult a shop with some performance expertise, in my unbiased opinion. On the CRX, I've got components from four vendors in the suspension (a result of a lot of research), and I will match it against any tuner package any day. Of course, with mix and match you can also really mess up the car if you don't do it right. For example, stiff springs with OEM shocks will seldom work right.

Mazdagremlyn, Mazdaspeed has some cool coilvers for your car. The guys at Mazda work with the true experts when developing these pieces (Bilstein, AMCI), so they really work from a performance standpoint. If you're in the market, give em a call.

On the bumpsteer issue, there may be some confusion between bumpsteer as technically defined and hitting the bumpstops while cornering, which also has some effect on steering:>

[MX5bob]

Mazdagremlyn, Mazdaspeed has some cool coilvers for your car. The guys at Mazda work with the true experts when developing these pieces (Bilstein, AMCI), so they really work from a performance standpoint. If you're in the market, give em a call.

On the bumpsteer issue, there may be some confusion between bumpsteer as technically defined and hitting the bumpstops while cornering, which also has some effect on steering:>

Mazdaspeed has also used the factory-backed 6's racing as a test bed, so the stuff isn't just slapped together for eye appeal and profit.

As for bumpsteer and riding the bumpstops, you don't want either one in a Miata or any autocross car. :D

[frosty]

I'll throw in my 2 cents since I just got new tires (Falken FK-451s; not as good as Azenis) to replace my OEM tires. I knew there would be a difference in grip but it still amazes me.

There's a certain right turn on a road I used to take at 30 mph with a little excitement and taking up an extra lane. This morning I did it accelerating hard from 30 to 40 and stayed in the right lane after making the turn. :eek: It felt easy.

[brian]

What does wheel travel have to do with bump steer? It's a matter of altering the pivot points in relation to the tie rods. Mazda thought enough about it to make a different tie-rod for the '93 LE, which was the lowest model from the factory. The LE wasn't lowered that much either.


it'd be kinda difficult to tell if he will for sure have bump steer issues with the lower springs. however, even with the lower springs, he's still in the stock range of travel, from droop to bump stop, so he shouldn't encounter any more bump steer than he might already feel now, if any at all.

[MX5bob]

it'd be kinda difficult to tell if he will for sure have bump steer issues with the lower springs. however, even with the lower springs, he's still in the stock range of travel, from droop to bump stop, so he shouldn't encounter any more bump steer than he might already feel now, if any at all.
But it's not the wheel travel that makes the difference. It's the change in the relation between end of the steering linkage and the rest of the suspension. It's the geometry of the double wishbone suspension and the tie rods.

Longer explanation here from Longacre Racing's site:

http://www.racerpartswholesale.com/longtech3.htm

As for performance driving in general, stiffer springs are not better than stickier tires. Poorly damped springs will make things worse, not better.

[Mazda_Gremlyn]

My only problem with the Mazdaspeed coilovers is that they aren't really race-worthy. They have the least increased spring rate (50-60% over stock) of all the coilovers on the market for our car and the shocks aren't adjustable, and also cost $1640 vs. something like the KW's which are $1400 or D2's which are all of $1000, both at least 32-way adjustable.

[MX5bob]

My only problem with the Mazdaspeed coilovers is that they aren't really race-worthy. They have the least increased spring rate (50-60% over stock) of all the coilovers on the market for our car and the shocks aren't adjustable, and also cost $1640 vs. something like the KW's which are $1400 or D2's which are all of $1000, both at least 32-way adjustable.
The Spec Miata shocks aren't adjustable either, but folks seem to find them race worthy. :D

Spring rate is only one thing to consider. Even a well-valved non-adjustable shock is better than a poorly designed adjustable. For instance, a lot of non-autoX Miata drivers like the KYB shocks, but I think they are only marginal when new and soon they just suck. :p

Can't argue about price. That's something Mazda Comp isn't great about on a lot of the racing parts.

[chapmanr]

MX5Bob hit the nail on the head..one shouldn't judge a package solely by its specs like spring rate.

I've driven a couple of M6s. I think you could improve the car greatly with with sway bars, staggered tires sizes (bigger in front) and a higher rate spring in the back.

Its great to have adjustable shocks; they're the best quick suspension adjustment available. But, I'd go for a quality non-adjustable shock like a Bilstein over an off brand that is a bazillion ways adjustable. Especially if the Bilstein had been revalved for the application.