more cons then pros

 

so im thinking of getting the motegi traklites 205/50/16 i think the wight is 12.1 and a tire at 21lbs but even then its .1 lbs heavier then stock i want to get the 205/55/15 motegi traklites with 10.6 and a 21lbs im almost 2lbs lighter

 

lighter will be better if the tire/wheel combo is lighter.... but if you go from a 195 to a 205, you have more contact patch and will get slightly less MPG as an FYI

 

Bigger rims make G20's look like secks on wheels!

 

yea true but i would like to find a 195/55/15

 

that isn't a very popular or easy size to find

205 50 15 is much more commonplace

 

Yes, there are many cons to this setup. And some pros.

Firstly, the wider contact patch of a wider tire will improve maximum traction level (assumes equal quality tire on the new setup). This doesn't necessarily apply to other cars (vw, some hondas) that have really poor suspension geometry because many of them can't take advantage of a wider tires as their camber curves don't keep the tire flat on the road. But G20s have a pretty good setup so it will make a difference. It should be noted that a wider tire patch will also increase overall fuel consumption.

If you've gone to a larger rim, and lower profile tire, you'll notice an improved response to steering input (once again assumes equal quality of tire). This is independent of overall steady-state traction levels, but important in the transition manouvers.

Now here's the thing that most people don't understand, and it has to do with polar moments of inertia (PMI), which more simply put, is effort required to accelerate and decelerate rotational mass. Moving to a larger diameter rim will increase the distance away from the centre of rotation of some of the mass of the overall wheel/tire combination.

Why is this important? Because the physics formulas for PMI include radius(squared) in them. This is a non-linear equation. Moving once ounce of weight double the distance away from centre-of-rotation will in fact take four times the effort to rotate.

So if your 15" wheel/tire combo weighs 15 lbs, and you move to a 17" wheel/tire combo of equal overall weight, with the same overall outside tire diameter, congratulations - you have just made your car slower!

But then of course, bigger rims with low profile tires are totally baller, and will get you all the chicks!

 

yea i changed it to a stock rim size to a lighter 14 in rim

 

whoa well said audi man:thumbsup:.

:2cents:although bigger rims/tires will give you more top end. smaller ones makes your ride torquey:2cents:

 

bigger rims = baller
smaller rims = racer

 

Big brakes don't fit under small wheels.

 

The same theory of PMI applies to bigger brakes. Most people don't need bigger brakes. They're only required if brake-fade is an regular issue, and that only happens if your brakes are overheating. So if you are doing track days, yah, big brakes can help. Other than that, they only serve to add rotational mass, which not only serves to reduce your acceleration, but also your deceleration.

Yes it's true - big brakes can actually increase your stopping distance.

If your actual goal is to stop faster, get better tires.

Of course, fancy spoked alloy wheels, with BREMBO-logo'd brakes underneath are pretty bling.

 

well the goal when upgrading unsprung pieces are:

Lower weight than before
Lower Sidewall
and increased footprint potential
and has colin said, increased room for brakes



One thing that alot of people forget is that when you get larger dia rims you will lose the amount of rubber you need mounted to the tire. Rubber weighs something too. So its hard to decipher if one setup is truly heavier than another until you get some tires mounted and compare.

For example my stock p10 rims are 3lbs ligher than my 16" aftermarket. BUT after I got them both mounted with tires, the 16" turned out to be slightly lighter.

 

There's also a sprung to unsprung weight issue - more unsprung weight makes the car more stable in turns. This is good at the track, and on the street with the right suspension. But more unsprung weight doesn't mean just add bigger rims - it's a function of sprung to unsprung. Lighter 16's by two pounds (like a set Rays for the track track) and some carbon fiber up top (sprung) works better than bigger below, same up top. The factory does kind of know what it's doing. Lighter is better obviously if you want that extra bit, which might add up to an extra tenth at an autocross event. Unfortunately the car is still front wheel drive, no matter what you do, and the CV's just can't handle that much input. And you lose at lest that tenth with the understeer from the front wheel drive. It's probably not worth it. There are lots of torn to crap CV's/flattened bearings and big rims from street and track. Bigger brakes means more unsprung, true, but brakes can be upgraded more easily with a good street compound, stainless lines, or even a bigger master cylinder - like the Q45 upgrade HowTo. Which is more than enough stopping power for a track afternoon.

 

There's also a sprung to unsprung weight issue - more unsprung weight makes the car more stable in turns.

Actually no.

Generally speaking, weight on any part of the car will slow you down. Weight up high is worse than weight down low. Unspring weight (wheels, brakes, etc) is worse than sprung weight. And rotational mass is worse than static mass. The absolute worst weight is unspring, rotational mass (like wheels).

The only time that adding weight MIGHT help would be to correct a massive imbalance (front to rear, or left to right) in the corner weights of the car. When I autocrossed my old Audi 200tq, I actually ran with a full tank of gas (80 litres!) to help balance it out. However, this shouldn't be considered a solution, only something that helps minimize a fundamental flaw in the car as a performance vehicle.

 

wow i didnt know my thread will create controversy lol but yea im going with american racing estrella and yokohama h4s tires

 

More weight unsprung -is better- not adding weight to any part - more sprung weight almost always makes turning worse. Ability to turn is a function of these two types - more unsprung is better. Any serious sports car has big shoes (they can actually use them, and the weight being unsprung,hauls around all the parts bouncing around on shocks - and the inertia helps, where as with the sprung part, it hurts), high rigidity and as much of the sprung weight down low as possible. Ever seen an engine that sits at a weird angle in an engine bay? A Lancia, BMW, or Alfa? That's why. Then you have to add in turning radius, springs, shocks (damping and rebound) and torsional stiffness. I was saying a 17" wheel adds weight, but doesn't improve anything, while a lighter pair of 16"s makes more difference if you're going to autocross. A set of Rays might weigh 14 or 12lbs while the stocks weigh 16lbs on the p11. You might do slightly better to add a carbon fiber hood and trunk and put in a rear shock cross mount. I'm not totally sure any of it's worth it either way on a FWD car... But... there you go.

 

what the.. ?

Im not going to argue, since I know the answer, but read this article..

"Effects of Unsprung Weight

The sprung weight of a wheel controls a trade-off between a wheel's bump-following ability and its vibration isolation. Bumps and surface imperfections in the road cause tire compression--which induces a force on the unsprung weight. In time, the unsprung weight then responds to this force with movement of its own. The amount of movement is inversely proportional to the weight - a lighter wheel which readily moves in response to road bumps will have more grip when tracking over an imperfect road. For this reason, lighter wheels are often sought for high-performance applications. In contrast, a heavier wheel which moves less will not absorb as much vibration; the irregularities of the road surface will transfer to the cabin through the geometry of the suspension and hence ride quality is deteriorated.

Pneumatic or elastic tires help by providing some springing for most of the (otherwise) unsprung mass, but the damping that can be included in the tires is limited by considerations of fuel economy and overheating. The shock absorbers, if any, damp the spring motion also and must be less stiff than would optimally damp the wheel bounce. So the wheels execute some vibrations after each bump before coming to rest. On dirt roads and perhaps on some softly paved roads, these motions form small bumps, known as washboarding or "corduroy" because they resemble smaller versions of the bumps in roads made of logs. These cause sustained wheel bounce in subsequent vehicles, enlarging the bumps.

High unsprung weight also exacerbates wheel control under hard acceleration or braking. If the vehicle does not have adequate wheel location in the vertical plane (such as a rear-wheel drive car with Hotchkiss drive, a live axle supported by simple leaf springs), vertical forces exerted by acceleration or hard braking combined with high unsprung mass can lead to severe wheel hop, compromising traction and steering control.

Though this is usually not considered important, at least in the popular literature, there is a positive effect. High frequency road irregularities, such as the gravel in an asphalt or concrete road surface, are isolated from the body more completely because the tires and springs act as separate filter stages, with the unsprung weight tending to uncouple them. This can improve overall safety."

 

As I read that, it seems to support what I was saying. So I guess we're both saying the same thing.

 

man if its weight and size that you are worry about then you are going to be stock with all four spears on your car and thats a good look lol.

 

Try actually reading the posts.

 

tell that to your self lol try reading from page one

 

whats the benefit of bigger rims

Other than looks, nothing. In fact, there are more cons.

1. Easier to bend wheel when you hit a road imperfection.
2. Wheels cost more.
3. Tires cost more.
4. More clearance issues when you lower the car.
5. Typically heavier.

We run 16x7 +40 wheels with 205/50-16 tires on the P10. We have it lowered on AMR coilovers. We still think they are too large & we can't get the car to go lower without clearance and rubbing issues. We're now trying to find some 15x8 +38 to +42 wheels to run some cheap ass 205/50-15 Falken Azenis RT-615 tires. They'll be cheaper, lighter, have more width to make better use of the tires, have better clearance, & look far sexier. (^_^ )

 

Well, there are benefits if you have the torque and hp - higher friction means a better launch off the line and more control in turns for the track. Plus the gentler ride on the street thing... Life is about compromises.