relativley technical post about tires, trying to find best grip

[chmercer]

I was reading about how wide tires dont necessarily offer a better contact patch because contact patch can roughly be calculated by the pressure = weight/area formula. so unless the load is increased, the wider your tires get, it only stretches out the contact patch and does nothing to help your grip. i guess this would explain why F1 cars can run super fat tires all around since they make about a million lbs of downforce.

soo, a s14 weighs roughly 3000 lbs with driver, equalling 1361 kg.and roughly, each tire is taking 1/4 of the weight so 340kg per tire (this would be kindof a skewed figure since more would be put on the front driverside tire etc etc. but i dont have all the numbers so this will have to work for now ) and i run around 32psi so thats 2.25kg/cm^2. 340/2.25=151cm. so if i have 205 tires, so my contact patch would be roughly (very roughly) 7.36 cm by 20.5 cm, assuming my calculations are correct.

SOOO.. if i get wider tires, all that will happen (disregarding the small increase in weight from heavier tires) is that my contact patch will get wider and narrower, but overall have the same area. as far as i can tell the only benefit of wider tires is that they heat up more evenly because there is physically more rubber, is this right?

so the only way to increase grip would be to a) change the compound of the tire to somthing softer, that grips better as it heats up, or b) create more downforce aka pressure on the tire via spoiler.

the conclusion that i have come to is that wider tires are only useful for when you are doing extremly heavy driving for elongated periods of time, because the only benefit of them is that they spread the heat evenly throughout the tire and dont melt as quickly. So i *think* a tire around 205-225 would be good for me since i dont do endurance racing / road racing / etc. and i should just choose the softest compound that my wallet can handle, given the rapid treadware. the only thing left would be creating downforce via spoilers, which is a completly different animal because i have no idea how to calculate how much downforce is created by any spoiler.

since i think i have one half of the tire equation figured out, does anyone know where to find information about front spoilers, wings, canards, and the like, for use on street cars? i can find info on F1 stuff but none of that really applies to my car.

anyway, please tell me if i have anything incorrect or whatever and point me in the right direction

WOW big post, thanks anyone who has the balls to read through the whole thing lol.

[s13sr20chris]

i can tell you what happened to me. everyone said that aero doesnt matter much on the street. i still wanted some downforce. then i did research and found that to have real downforce(excluding giant wings) your car has to have mega low ground clearance. i figured i could handle a stiff ride and i can. what i cant handle is having to drive all around the city to avoid speed bumps and potholes. a really low car could easily high center or worse on a speed bump. so i abandoned my quest for street legal downforce. just to have a usefull front splitter you need some serious lowering. might be alright for a "once in a while" car. the most aero you could reasonably use is better airflow for radiator, intercooler, brakes, and other heat exchangers. thats my opinion on it.

[chmercer]

i was more trying to figure this out for when i go to the track and stuff. i can adjust my suspension so i can change the ground clearance to be reasonable for street use or really low for track. i was wondering if you knew of any webpages with tech about front splitters, spoilers, etc? you say you have researched so maybe you remember some of the good URLs? also does my information seem correct about the tires?

[s13sr20chris]

http://autozine.kyul.net/index.htmlclick technical schoolthats the only one i can remember offhand. your tire info sounds right to me, but i am no susp/tire guru. if you have good coilovers then i think an aero package for the track may be feasable. a reputable front fascia with a splitter made of plywood should work wonders. thats according to a recent scc article on cheap road racing.

[chmercer]

plywood? jigga wha? lol, that sounds a little ghetto to me but whatever

[s13sr20chris]

no really. plywood is natural carbon fiber. check out the old scc article. they might have it on their web site. they just cut it out. made some straps to hold it up. and attached it too the fascia. they did it to a sentra at scc. i swear its not really that ghetto.

[Nismo_Freak]

plywood is natural carbon fiber.

Hahhahahahha it's so natural cause they cut down plywood trees!

In reality they are equally natural... just pieces of elements bonded together

[Jookmasta]

hey nismofreak, does ur SPL store have any parts for us KADE owners?

[Doogz]

Excessively lowering your car will cause extreme changes to the suspension geometry and will more likely than not make your car handle like crap. Generally speaking, the closer together your car's instant center is to its center of gravity, the better it will handle. With most street cars' little stubby lower control arms, the IC will drop much faster than the CG when lowering the car thus causing crappy handling. While you may never have great aerodynamics with your car sitting up fairly high, i think decent areo and good handling are better than great aero and poor handling.

[chmercer]

what i am trying to do is develop some kind of road racing aero setup. I wouldnt be cruising around .5 inches off the ground when in town. whos to say that i couldnt drop my car to the ground with correct alignment with aftermarket control arms? i dont see how you couldnt have good handling on a super lowered street car with the correct parts.

edit - not exactly sure what you mean by IC and GC?

[Exar-Kun]

hey chmercer, you forgot something you can change about the tiresthat helps grip...

tread design. the less "void" area of a tire, the more effective tread meets the ground, thusly more grip. Look at the Pzero corsa versus another street tire, like an ecsta 712...the Pzero crosa has very little void, versus the ecsta has high void.

you get the idea.

as for downforce, minimising the airflow under the car can be usefull, but on an s14 you have a "box" shape car, which unfortunately doesnt allow for smooth streamlining(one the rear 1/2 at least).

and unfortunately, most of us dont have access to a wind tunnel to actually test changes. You'r best bet would be to lower the car about 1" or so, adjusting as necessary(based on field experience, dampening, etc) and getting a nice air dam that smooths out airflow, and has some form of front spoiler to create a bit of downforce up front.

top secret, JUN, and INGS all make very good near-race ready parts, that have been researched to provide more downforce.

a spiler will have to be in the wind tunnel(drag area) on the back to produce good downforce, that means it will ahve to be either A. high B. very sloped(angle of attack) or C. places far enough back to catch the downdraft

hope that helps-chet

[Doogz]

CG=center of gravityIC=instant centerRC=roll center

was just too lazy to type them out again.

Actually, i am mistaken, i got out my suspension notes and the distance between your Roll center and center of gravity is what makes the difference. The lower control arm makes an angle and from the top of the strut(and one other point i can't recall) makes another angle and when they connect, is your IC. From there you take that point and connect it to the center of the tire to make another line. Where that line crosses the center of the car is your RC. The less distance between your RC and CG is important. As you can see i really exagerated the angle but in most cases the RC will drop much faster than the Center of gravity of your car and result in sloppier handling.

I drew a crude diagram of it and if anyone wants to see it or put it up somewhere and insert a link to it then please leave your email and i'll send it to you.