BRZ vs Mustang - Here is the review the haters have been waiting for.

[fatoni]

Originally Posted by p911gt3

The reason people are mentioning a larger area contact patch with bigger around tires is because the contact patch is 2 dimensional. In theory a 1 inch increase in diameter with no increase in weight should net a slightly longer contact patch.(that was a pretty scientific statement huh?) As in most things, this should also be subject to the law of diminishing returns.

IMHO, people forget that there is also a tendency of the contact patch, at rest, to shorten when the tires are widened. In the end, I think we need to program a simulator to calc the contact patch at rest and a variety of loads. Maybe by saying this someone will build one for me

that contact patch will have to be narrower in order to make that physically possible though.

on another front, all this talk about how the mustang has better rims and tires so it isnt fair is stupid. thats like saying that its not fair that the brz is hundreds of pounds lighter. the mustang is cheaper so why do you think spending more money on the already more expensive competitor is fair?

[p911gt3]

Originally Posted by fatoni

that contact patch will have to be narrower in order to make that physically possible though.

on another front, all this talk about how the mustang has better rims and tires so it isnt fair is stupid. thats like saying that its not fair that the brz is hundreds of pounds lighter. the mustang is cheaper so why do you think spending more money on the already more expensive competitor is fair?

It is quite likely that you are right, but why would the contact patch need to be narrower in order to make the contact patch longer? Shouldn't the contact patch always be a similar number of degrees/radians of the circle long? Yes there are tons of variables such as the flexibility of the rubber, the weight of the whole wheel tire unit, temperature etc. If you are indeed right, I will need to make sure to give you one of these

[fatoni]

Originally Posted by p911gt3

It is quite likely that you are right, but why would the contact patch need to be narrower in order to make the contact patch longer? Shouldn't the contact patch always be a similar number of degrees/radians of the circle long? Yes there are tons of variables such as the flexibility of the rubber, the weight of the whole wheel tire unit, temperature etc. If you are indeed right, I will need to make sure to give you one of these

since i can compromise the integrity of a tire with my hands (tens of pounds) and cars weigh thousands of pounds, i think its safe to say that the cars weight is going to have a larger impact. but i dont think that even matters really since with any tire you are going to have to deal with tire structure and thats going to make the differences even smaller.

bottom line is that (while not perfect) contact patch size is a function of the weight of the car and how much weight each inch of contact holds (tire pressure) if tire pressure and weight dont change, a longer contact patch has to be more narrow because it can only be so large

[KeepGuessing]

Originally Posted by DarkSunrise

1) Proof of "numerous confirmed duplications" of RSX-S 0-60 in less than 6.4 seconds

Where's numerous accounts of BRZ runing 6.4 seconds without a roll-out?

Where's ANY account of BRZ running 6.4 seconds without roll out...Show me that while you're at it..

Until then 6.4 is an absolutely arbitrary number that has ABSOLUTELY no relevance..as 6.4 was done by Motor Trend..Who records their 0-60 time..using a rollout...

Motor trend has confirmed this which is why their 0-60 times are always much faster than every other standard test performed on vehicles..

and in response to MID 6 second 0-60's..

http://www.caranddriver.com/reviews/...take-road-test

The '05 Type-S sprints to 60 mph in 6.2 seconds

http://www.caranddriver.com/comparis...ype-s-page-6-1

Our underdog victor offers the worst 0-to-60 time (6.4 seconds)

http://www.automobilemag.com/reviews...s/viewall.html

our test car clocked a 6.5-second sprint to 60 mph

Those are along with Road&track/MT..Evo didn't have a review i could find...Edmunds only had MFC estimates.

2) You honestly think because this dyno shows 167 whp that it couldn't be an RSX-S?

Yes....I do honestly think because the Graph shows LESS power than the BRZ..it'd be a different car or a RSX-S that had been run ragged..why?
Because i'm assuming (unless you don't know how dyno's work) that these tests were done in the same conditions or AT LEAST similar conditions on the same type/brand of dyno....So that rules out variation from brand/type drum size and other environmental impacts...

That leaves us with the parasitic loss of rotational inertia...In which, the RSX-S has less and the Subaru has MORE....Meaning the subaru LOSES more between it's path from the output shaft to the rubber.

Now if we have 2 cars that are BOTH 200HP (actually one is 200 (RSX-S) one is 198(BRZ)) on the same dyno their results should not only be closer...but the RSX-s should have a slight advantage in peak HP production from THOSE indications alone...

Which is why it's simple to come to the conclusion it is either not a RSX-S but a RSX+ a part or two...Or a RSX-S who's worn to crap.

Originally Posted by KeepGuessing

..Or maybe this was just some old sloppy RSX-S on the drums...

but i'm assuming you missed that part..

3) The RSX-S isn't a 210 hp car, the rating changed from 05-06.

And the relevance of that is ZERO, because whether or not the 210HP is a pre-post standardization rating..The result is MORE power than 200ps..So the RSX-S is either 210HP or 207HP, both of which are more than 198hp, unless that rule has changed at some point in time that unless it's value is 230 or higher it doesn't count.

In today's rating system, it's 200. In fact, the 02-04 RSX-S was rated at 200 under the old system, meaning in today's rating, it'd be in the 19X range. Also understand manufacturer's ratings of their cars will also vary. Trying to argue a RWD BRZ can't ever dyno more than a k20a2 RSX-S is ridiculous. In fact, the chart above proves it already happened.

One I don't remember anyone specifying we would compare the older less powerful RSX-S to the new car..That seems kind of silly don't you think there bud?

In todays system it's 201hp when calculated for proper humidity etc etc (which to reiterate..IS STILL more than 200ps)....THAT is a SAE standardization in order to protect consumers with cars off the lot..So companies couldn't take advantage of them with inflated numbers here and there..

Big thumbs up to clearing up the fact big business can't lie to us about power ratings they produced in a ice cold room in an oxygen rich environment...

Now guess what didn't change with the SAE standards? Metric ratings...
which brings us to 210ps to the BRZ's 200ps....
So yes..Manufacturer ratings will vary..Good thing you've said that, because the only reliable source of data we'd have would be the data collected from repeated experiments...

And guess what that would be? Multiple dynomometer readings...

Multiple dynamometer readings are easily available for the RSX-S..K20A and K20Z...easy easy peezy..

however the "2" we have availible to us for the BRZ avg out to 168WHP...but even with the generous 173WHP rating of inside lines dyno...That puts it square in the cross hairs of what the older series RSX-S dyno regularly..

Actually that 164 of Cobb tuning to the 173 of Inside line is the EXACT parameters in which Pre-05 RSX-S's dyno on avg.....
Meanwhile the 05+ RSX-S...Dynos on avg, a tad bit higher than both of them..

now we take a big circle back to the "RSX-S should have a slight advantage on power production than the BRZ simply because their power production is so similar yet the RSX-s spins the front tires" And if you want to throw in the old RSX girl into the equation then you get the "the RSX-S produces slightly less, but due to the nature of FWD should put about the same power to the ground"..but since no one mentioned the OLD RSX-S there's no need to bring it up.

So what we're left with....Is a RSX-S that gets more power to the ground, accelerates faster to 60...and has more revs and tighter gears to work with...Making the whole "you won't notice the dip because the GIGANTIC 7Ftlbs of torque will quash that discrepancy" incorrect....

[p911gt3]

Originally Posted by fatoni

since i can compromise the integrity of a tire with my hands (tens of pounds) and cars weigh thousands of pounds, i think its safe to say that the cars weight is going to have a larger impact. but i dont think that even matters really since with any tire you are going to have to deal with tire structure and thats going to make the differences even smaller.

bottom line is that (while not perfect) contact patch size is a function of the weight of the car and how much weight each inch of contact holds (tire pressure) if tire pressure and weight dont change, a longer contact patch has to be more narrow because it can only be so large

I think in this case it appears we both agree that weight of a car will play a large part in this. We also agree that lengthening the theoretical contact patch is not a magic pill in terms of increasing the area of contact as load on each tire will change changing the forces creating the patch.

Now if only we could get someone to build us a simulator so we could see the physics at work!

[carbonBLUE]

i really wanna hit people...

keepguessing are you going to buy a brz or frs? if not why are you here? i think its only to troll...

[KeepGuessing]

I am seriously considering a BRZ for my wife....But the more I read about it being the second coming of Jesus Christ, the less I want her or myself to be associated with the target group.

And thanks for the a-typical "omg you don't like it more than you like your own mother!!?!?!? Troll!!!!" response.

[Dimman]

How did we go from Mustang has moar powah than BRZ, to RSX has moar powah than BRZ?

I can't keep these comparos straight anymore. Focus ST is about F1 cars being RWD and this is now a pissing match between an out of production FWD car and the BRZ?

How about we compare the the RSX-S to the Focust ST?




(on another forum...)

[carbonBLUE]

Originally Posted by KeepGuessing

I am seriously considering a BRZ for my wife....But the more I read about it being the second coming of Jesus Christ, the less I want her or myself to be associated with the target group.

And thanks for the a-typical "omg you don't like it more than you like your own mother!!?!?!? Troll!!!!" response.

well if you want a well controlled little coupe for you wife that she can find the limits and become comfortable in very easily. Also a car that wont fly wildly out of control when you surpass those limits, also its safe and has a ton of airbags
then get a BRZ

you dont have to associate(not trying to tell you to get off the forum or not) with this forum or other frs, brz people on the road, thats your choice, same with if you like the car or not

you wont see a lot of us in the AZ area anyways, this forum will be useful for DIY work to save money and learn about the car in years to come :P

some points
1. 34 mpgs highway with the auto
2. has plenty of airbags
3. has homelink in the BRZ
4. great handling and lots of smiles
5. enough room for a weeks worth of groceries
6. low maintenance (usually toyota and subarus are pretty reliable)
7. tires are pretty cheap for a decent pair
8. navigation (brz) for long trips
9. nimble (easier to avoid deer considering you live in the 4 corner state area)
10. auto has a "snow" mode in case you go to colorado or utah, or if it snows in AZ

i could go on...

[Big T]

If I had a dollar for every time someone in this thread mentioned "contact patches"....

[Spaceywilly]

What you say would be true if the tire was perfectly circular since a circle will only intersect with a line at one point regardless of diameter as you said. But the tire deforms where it meets the pavement so it is not a perfect circle. The amount of deformation is affected by a number of things such as vehicle weight, tire pressure, and sidewall stiffness. Given that all these things are equal, and only the tire radius is allowed to change, the same amount of deformation in a tire of a larger radius would result in a larger area in contact with the road.

Picture this shape : (_)

As you increase the size of the round part of that shape the flat part at the bottom would increase in length.

Originally Posted by KeepGuessing

I am seriously considering a BRZ for my wife....But the more I read about it being the second coming of Jesus Christ, the less I want her or myself to be associated with the target group.

And thanks for the a-typical "omg you don't like it more than you like your own mother!!?!?!? Troll!!!!" response.

Do you really buy cars based on the people other people associate with it? Who cares?

[Deslock]

Originally Posted by ZDan

do I have to say this again?
1. Bigger tires don't necessarily give a bigger contact patch.
2. Bigger contact patch doesn't necessarily give greater grip

Bigger contact patch at the same loading per square inch will generally give more grip, but that means a heavier load hence commensurately greater grip is *required* just to pull the same cornering g's if all the load is coming from mass and not aero.

I had said that the FR-S/BRZ has more tire width per weight vs. the Mustang. You said:

Wider tires o generate more lateral grip and it's not due to "increased contact patch". How much more is generally overstated and it is going to be something less than a straight linear relationship.

Taller tires do not inherently generate more lateral grip.

Generally, a shorter/wider contact patch is better for handling, and a longer/narrower contact patch is better for drag racing.

For a given tire construction, "contact patch" is a strong function of inflation pressure and weight, not so much tire width and diameter.

I agree with most of that (and yes tire width, tire PSI, and vehicle weight have a larger impact). I think you're reading a bit too much into my comment... again, my point was simply that you can't only look at tire width per weight.

BTW, an interesting page: http://www.performancesimulations.co...on-tires-1.htm

This has gotten off topic; feel free to PM me if you want to discuss it further.

[KeepGuessing]

Originally Posted by Spaceywilly

Do you really buy cars based on the people other people associate with it? Who cares?

At what point did I say I go out shopping for cars and ask sales reps for "what the demographic looks like"?

Like it or not there's a stigma that goes along with alot of automobiles, and it becomes an issue when you actually have to weight the pro's and cons of is this car fun enough to make up for the fact that you'll look like the droves of 28 year old trance blasting morons who are hell bent that "center of gravity means this car is better than a porsche bro!!" and end up getting pulled over by the police 2-3x as often because of the rest of the ownership base.

I've ran into that problem with vehicles in the past...Not happening again.

[carbonBLUE]

Originally Posted by justaquestion

I'm not following...

If you take a 2" across sphere, and place it on a flat surface, the contact patch is identical to a 9999999 mile across sphere.

So if you have two symmetrical tires, that share 100% the same dimensions, minus the diameter, then their contact patch should be equal.

What am I missing?

ohh wow your special, get two balls of the same size, set one ball on a table, that would be the tire off the car standing upright unloaded, now take your hand and press on the second ball, the ball will absorb the pressure and compress, this is replicating a tire when its on a car and the car's weight is on the tire thus giving a larger contact patch

now on test two get a volley ball(smaller ball) and a basket ball(larger ball)
inflate both balls to the same PSI and dip the bottoms in paint
press both balls onto a large piece of paper, now press down on both balls with equal force
measure the diameter of each paint print

the result should show that the volley ball has a smaller contact patch than the basket ball, its 3rd grade science project i hope you can complete it...


you can even further the test by putting more pressure on the basket ball to resemble a higher load for larger diameter tires that are usually used on heavier cars the measure the difference in diameter vs the volleyball with less load