Prepparing a Yaris for FSP (Solo 2)

[eclip5e]

Originally Posted by Russelt3hPirate

haha, awesome! what are you doing here?

Trying to convince Yaris drivers that the platform is a solid contender as a race platform in the <2.0l engine demographic.

[Russelt3hPirate]

Originally Posted by eclip5e

Trying to convince Yaris drivers that the platform is a solid contender as a race platform in the <2.0l engine demographic.

sweet me too! too bad they aren't 5x114.3 or we could test some 17x10's and 275s :)

[eTiMaGo]

how in the world would 10" wheels fit on a yaris??? And with such a light car, would there be enough weight on the wheels to maintain a good grip?

[03Z33]

It's doable with some pulling of the fenders, or an overfender... but I'm not sure they are needed

For autocross duty, I'd be all over a set of 13x9 Watanabes or Panasports with some sticky Avons or Hoosier A3S06's!

[eTiMaGo]

Hmm yeah with a wide body kit it could be physically done.

But what I am worried about is the downside of using really wide wheels? Isn't there a point at which the weight of the car is just not enough to ensure maximum grip on the tires?

[the_saint]

Depending on the offset you might not need a widebody kit. I have seen a 9" wide wheel on a stock fendered Yaris/Vitz.

[eclip5e]

Originally Posted by eTiMaGo

Hmm yeah with a wide body kit it could be physically done.

But what I am worried about is the downside of using really wide wheels? Isn't there a point at which the weight of the car is just not enough to ensure maximum grip on the tires?

Any non-spec size wheel will accelerate the speed at which your wheel bearings are worn, especially non-spec offset.

As for power/weight ratios, this could be a problem, but more importantly, there is a point where adding wheel/tire width no longer adds to grip levels, and only adds weight.

[Russelt3hPirate]

i was joking about the 10" wheels.

contact patch doesn't increase with tire width or wheel width, it's dependent on vehicle weight.

lateral grip will increase b/c the contact patch is now "wider" but the contact patch area isn't larger.

I dont think it'd make much sense to have more than an 8" wheel but i'm pretty sure a 15x7 will do the car plenty justice :)

[the_saint]

I'm not trying to argue anything about "wider is better"...but wouldn't a wider tire=larger contact patch area? I mean from a purely mathematical stand point.

[Russelt3hPirate]

Originally Posted by the_saint

I'm not trying to argue anything about "wider is better"...but wouldn't a wider tire=larger contact patch area? I mean from a purely mathematical stand point.

nope, contact pacth area is dependent on weight

contact patch shape is dependent on wheel and tire width

[03Z33]

I'm just going by what I see at the higher levels of "cone dodging" (autocross). You normally see the faster cars running aggressive wide tires, with very sticky compounds (slicks or DOT R's like A3S06, etc..)

There is a balance you need to achieve between the wheel width, tire width, and weight of the car. Most times, a narrower stickier tire will yield superior results to a wider tire that isn't making good use of its full contact area (and additional weight). The best way to find these things out is to go out with a tire pyrometer or some chalk and try out different setups, pressures, etc...

[Russelt3hPirate]

Originally Posted by 03Z33

Most times, a narrower stickier tire will yield superior results to a wider tire that isn't making good use of its full contact area (and additional weight).

now, i understand you like narrow tires ;)

anyway I know from personal experience that a 275 on an 8" wheel is faster around an autox couse than a 245 on an 8" wheel. (same rolling diameter too btw).

when limited by wheel size it is most beneficial to run the widest tire possible simply for the lateral grip

when limited by rubbing or fenders or anything else, it is beneficial to run the widest tire possible simply for the lateral grip

turn in and some response is sacrificed but the increase in lateral grip is worth it when you're looking at the times at the end of the day.

I plan on having a set of 15x7s for autox with some 225s, which is similar to what my buddy runs on his xA. Might actually just steal his wheels for a day. ;)

The Yaris will be a fun toy, i'm excited :)

[03Z33]

See, I totally agree with the above and have first hand experience to back it up.

I ran stock size 245/40/18 tires (Yokohama AVS Sport) on the stock 350Z wheels which are 18x8 for a few track events. Then I came up on some chep AVS Sports in 275/35/18 (almost same OD, just wider) and they looked pretty funny bulged out on a 8" rim but they worked suprisingly well! My tire guys hated having to mount these even more then some of my strethed tires

I should have my 16x8's mounted today or tomorrow, I'll report back on the fittment. I really think 13-15" would be best for autocross, anywhere form 7-9" wide should fit (depending on offset and tire size) and you may benefit from narrower to save some weight.

[Russelt3hPirate]

what wheels are you getting? offset?

[03Z33]

This set is just for looks 16x8 +15 rear and +25 front (deep dish)

[Russelt3hPirate]

Originally Posted by 03Z33

This set is just for looks 16x8 +15 rear and +25 front (deep dish)

and 185s :(

is there a reason you're increasing your rear track greater than the front?

have you looked into the adverse effects of changing the vehicles scrub radius? especially on a FWD car.

my friend has some 15x7 +22mm Team Dynamics that we will be testing out.

[the_saint]

Originally Posted by Russelt3hPirate

....is there a reason you're increasing your rear track greater than the rear?

have you looked into the adverse effects of changing the vehicles scrub radius? especially on a FWD car.

Originally Posted by 03Z33

This set is just for looks 16x8 +15 rear and +25 front (deep dish)

one character

[Russelt3hPirate]

Originally Posted by the_saint

one character

??