Spinoff: FWD, not bad, just different.

[Dimman]

@rice_classic

The thing about when we say 'it's physics' is that physics isn't opinion.

The issue is about tire loading and weight transfer. Due to packaging constraints you will see FWD car in the 65:35 to 60:40 range for f:r weight distribution. Whereas front engine RWD may range from 60:40 to 47:53 (LFA, I believe) or less. Mid and rear engine even more rear biased.

Now if you look into tires you will learn about the 'traction circle' and about tire efficiency, which is how much lateral/longitudinal load it can resist compared to the vertical load on it.

Next step to consider is weight transfer. On acceleration the weight gets transferred rearwards. On FWD this reduces drive wheel traction and maximum acceleration potential. Under hard braking more weight goes forward. But since braking is through all 4 wheels the much higher load on the front tires compared to low load on the rears reduces overall grip because of tire efficiency.

Steady state cornering on 'square' tire setups, same problem. The extra weight over the fronts causes them to become inefficient before the rears. The FWD inherent understeer.

Corner exit is a combination of overloading the outside front through the same forces as cornering, but coupled to the limits of the friction circle (a tire cannot provide both maximum lateral and longitudinal grip at the same time) and underloading the inside front. Again an efficiency imbalance.

There are ways to minimize all these things but there is a fundamental physics handicap inherent with FWD.

But I think I said in another thread application CAN trump this. Example I gave was Ford Focus ST vs Ford LTD...

[fatoni]

Originally Posted by Dimman

@rice_classic

The thing about when we say 'it's physics' is that physics isn't opinion.

The issue is about tire loading and weight transfer. Due to packaging constraints you will see FWD car in the 65:35 to 60:40 range for f:r weight distribution. Whereas front engine RWD may range from 60:40 to 47:53 (LFA, I believe) or less. Mid and rear engine even more rear biased.

Now if you look into tires you will learn about the 'traction circle' and about tire efficiency, which is how much lateral/longitudinal load it can resist compared to the vertical load on it.

Next step to consider is weight transfer. On acceleration the weight gets transferred rearwards. On FWD this reduces drive wheel traction and maximum acceleration potential. Under hard braking more weight goes forward. But since braking is through all 4 wheels the much higher load on the front tires compared to low load on the rears reduces overall grip because of tire efficiency.

Steady state cornering on 'square' tire setups, same problem. The extra weight over the fronts causes them to become inefficient before the rears. The FWD inherent understeer.

Corner exit is a combination of overloading the outside front through the same forces as cornering, but coupled to the limits of the friction circle (a tire cannot provide both maximum lateral and longitudinal grip at the same time) and underloading the inside front. Again an efficiency imbalance.

There are ways to minimize all these things but there is a fundamental physics handicap inherent with FWD.

But I think I said in another thread application CAN trump this. Example I gave was Ford Focus ST vs Ford LTD...

two things. physics (well, technology) is changing. i see cars like the gtr and camaro turning times that are way too fast for something that heavy. second, the problem is that we arent living in a world of absolutes. we are all here on a forum for a 25k car. we live in a world where physics takes second place to price. anybody taking the frs to a place where physical limitations are an issue has spent their money on the wrong chassis too. in the real world, for the people of this forum, its about bang for the buck.

if we talk about preference, ill stick with rwd. if we talk about performance, ill stick with whatever is faster at any given price point.

[rice_classic]

Originally Posted by ZDan

Title of thread and first post invites debate, practically beg for it.

Title, not content. In the first post I even concede to the benefits of RWD as I was deliberately trying to keep this from becoming a debate because it isn't and that point was conceded in the first post. The only debate that was "begged for" was why FWD shouldn't be dismissed as a platform.
Your points were all made not only by myself but others in the beginning so why beat the dead horse?

Originally Posted by ZDan

Your initiating the thread doesn't make it *your* thread. It's a topic for discussion. We're having one.

The first sentence in this thread is: "I didn't want to crap up the GM thread so I respectfully started something new."

Just sayin'

Originally Posted by ZDan

If you want to make a declarative statement, whether true or not, and not have any one contest it, this probably isn't a reasonable place to expect that to happen...

Actually, that's what makes this place great but the darkside is that we can't have our cake and eat it too. So fine then let's not let things go uncontested...

Originally Posted by ZDan

1: Anyway, even if fwd were just as fast/quick as rwd, it would still suck.

2: Because FWD doesn't really teach you how to DRIVE.

3: whereas fwd will tolerate WRONG inputs and just scrub scrub scrub.

4: People who learn to drive with rwd learn a lot more than those who learn to drive with fwd.

5: Same experience vs. same, my money's on someone who learned with rwd going faster sooner in an fwd car than vice versa.

6: Fwd is a great way to build cars more cheaply. Other than that, it sucks.

7: I seriously doubt people raised on rwd have similar issues looping their first performance fwd cars

#1: is just a put down, no argument there, not point to be made... nothing being "discussed".. just an opinionated jab with no value which qualifies essentially as trolling. Like jumping into a Vortech thread and saying "even if it makes the same power as the turbo it'd still suck." Remind you anybody?

#2: Duh. FWD/RWD/AWD.. none of them teach you how to drive. A driving instructor does that.

#3: That is incorrect and a deliberate misrepresentation.

#4: This is nothing more than conjecture and ridiculous conjecture at that. It seems like just another "jab".

#5: Repeating the same jab again with more conjecture.

#6: Another comment without any useful advancement of the "discussion" ending with another jab.

#7 was a real beauty this one is and illogical. It's like saying people who learned to drive with FWD cars have similar issues understeering their first performance rwd cars. The logic doesn't compute.

[rice_classic]

Originally Posted by Dimman

The thing about when we say 'it's physics' is that physics isn't opinion.

To be clear I'm not arguing physics (because very little "physics" was even presented) and all the stuff about weight transfer, weight bias, motion ratios, friction circles, slip angles, contact patches... all old news to me. Not my first rodeo. I am not making the argument that FWD is a superior platform and I never was. Just that it is capable, fun and shouldn't be "dismissed" because of those reasons.

Originally Posted by Dimman

Steady state cornering on 'square' tire setups, same problem. The extra weight over the fronts causes them to become inefficient before the rears. The FWD inherent understeer.

This is true too and easily dealt with.

Originally Posted by Dimman

Corner exit is a combination of overloading the outside front through the same forces as cornering, but coupled to the limits of the friction circle (a tire cannot provide both maximum lateral and longitudinal grip at the same time) and underloading the inside front. Again an efficiency imbalance.

It would seem to me that the goal is to not overload your tires.

Another simple way of saying it is that your drive tires can turn and they can accelerate but they can't do 100% of both at the same time. The imbalance can be dealt with surprisingly well.

Originally Posted by Dimman

There are ways to minimize all these things but there is a fundamental physics handicap inherent with FWD.

But I think I said in another thread application CAN trump this. Example I gave was Ford Focus ST vs Ford LTD...

And once again, there's no argument here.

[Dimman]

Originally Posted by rice_classic

To be clear I'm not arguing physics (because very little "physics" was even presented) and all the stuff about weight transfer, weight bias, motion ratios, friction circles, slip angles, contact patches... all old news to me. Not my first rodeo. I am not making the argument that FWD is a superior platform and I never was. Just that it is capable, fun and shouldn't be "dismissed" because of those reasons.



This is true too and easily dealt with.



It would seem to me that the goal is to not overload your tires.

Another simple way of saying it is that your drive tires can turn and they can accelerate but they can't do 100% of both at the same time. The imbalance can be dealt with surprisingly well.



And once again, there's no argument here.

Ok then, let's sort out the problems. (My first love was a '92 5 speed Civic Si hatch. Don't tell anyone...)

I've always wondered why a 'reverse stagger' isn't common on performance FWD. The only factory car I can think of was the last Pontiac Grand Prix with the V8 option.

[ZDan]

At the risk (certainty?) of making myself look like even *more* of an ass...

Originally Posted by rice_classic

So fine then let's not let things go uncontested...

That's the spirit!

My comment #1 was somewhat tongue-in-cheek, totally intended to be incendiary. Mission accomplished?

Regarding comment #7, for decades, people were brought up learning to drive with rear wheel drive vehicles. In the 70s/80s when more and more cars went front wheel drive, I don't recall any rash of incidents of rwd-experienced drivers having difficulties adapting to fwd.
Fast-forward to the S2000, and then again to the FR-S/BRZ, and scads of drivers brought up on fwd are crashing these cars left and right.
If you don't know how to drive, fwd is more forgiving.
If you were brought up driving only fwd, you might be in for a rude surprise when you get behind the wheel of a responsive rwd car.
If you were brought up driving only rwd, you really don't have any worries transitioning to fwd.

These are my subjective impressions only, of course! But when I was growing up and the transition to fwd was *happening*, it was no big deal.


Regarding the physics of it, Dimman hit all the points. There aren't many, not much to interpret. Just basic facts.

FWD is inferior in braking due to overloaded fronts, RWD makes better use of its four contact patches.
FWD is inferior in cornering due to overloaded outside front, practically non-utilized inside rear, RWD makes better use of its four contact patches.
FWD is inferior in acceleration in normal dry/wet conditions due to severely unloading the drive wheels, RWD loads up its drive wheels on acceleration.

I know, not your first rodeo, so this is all old news to you...

Regarding wet conditions, my experience has always been that fwd sucks in the wet. Though grip is reduced vs. dry, there is still enough grip to get significant weight transfer such that wheelspin is more of a problem with fwd vs reasonably-decently-balanced rwd.

A quick/dirty analysis of problem confirmed my experience. Above ~0.64 effective static coefficient of friction, a 52/48 FR car will be able to put more power to the ground than a 62/38 FF car (100" wheelbase, 20" c.g. height).
Less available grip than that, FF car has the advantage.

The all-season tires we just got for our Mazda3 pulled 0.75g in wet skidpad testing, fwiw, so 0.65 c.f. isn't a particularly high hurdle.

It is *very* sensitive to weight distribution, though. Moving it forward 1% and comparing 53/47 FR (FR-S/BRZ numbers) against a 63/37 FF, the FF has the advantage with less than 0.73 effective coefficient of friction. Basically equal in "good" wet conditions, with the nod to fwd in more adverse wet conditions (cold, surface fluids like oil coming to surface, etc.).

Anyway, the FR cars I drive are 50/50 or better (more rearward), so my experience has been that they do great in the wet, better than fwd.

It is worth noting that "better" f/r weight distribution for acceleration is typically *more* even on an FR car, but LESS even on an FF car. A 50/50 FF car wouldn't be able to get out of its own way!

Anyway, truth told, we have an FF car ('05 Mazda3s, leather interior), and we do love it.
I am a fan of some fwd cars:
original Mini
CRX
Dodge/Shelby Charger/Omni
Integra GS-R/Type R
etc.

Still, they'd all be eleventy times cooler with the entire drivetrain moved aft several feet!

[wheelhaus]

ZDan, you're making some good obvious points, and some overly generalized statements, but again this isn't meant to be a debate. It's about discussing why FWD is so successful (in racing applications) when every bit of common sense and RWD elitism (which you sir, have in spades) says otherwise.

[ZDan]

Originally Posted by wheelhaus

It's about discussing why FWD is so successful (in racing applications)

I thought we covered that on page 1. Rules structure determines what will be the optimal setup. If rules are structured such that the fwd formula has the advantage over the rwd formula, fwd wins.

Similar to LeMans, they structured the rules to give diesels an advantage, and lo and behold, they got what they wanted, diesels winning LeMans.

Doesn't mean diesels are inherently "better" race car or sports car engines.

[rice_classic]

Originally Posted by ZDan

My comment #1 was somewhat tongue-in-cheek, totally intended to be incendiary. Mission accomplished?

Gmhooker is that you? Sheeze, you just admited to being a blatant troll.

Was going to respond to everything else about how much you're "missing it" but then I realize at some point I need to stop feeding the troll.

[rice_classic]

Originally Posted by Dimman

I've always wondered why a 'reverse stagger' isn't common on performance FWD. The only factory car I can think of was the last Pontiac Grand Prix with the V8 option.

It's quite common in Japan. Some Autox-ers in the states do it and even some fwd road racers. The big incentive for not staggering the tires is the cost and logistics. By having the same size tire on all for corners I can rotate them easier between all 4 corners to increase life and extend heat cycling so there's a big cost and logistical benefit of not staggering.

[Dave-ROR]

Originally Posted by Dimman

Ok then, let's sort out the problems. (My first love was a '92 5 speed Civic Si hatch. Don't tell anyone...)

I've always wondered why a 'reverse stagger' isn't common on performance FWD. The only factory car I can think of was the last Pontiac Grand Prix with the V8 option.

FWIW we run a 'reverse stagger' on our chumpcar. Japanese tuners have done so for.. decades? Class rules often play a roll (for me at least - we run staggered because we have to keep OEM springs, dampers and sway bars). I ran square setups on my FWD cars and had zero understeer because of spring rate, roll bar and alignment tuning.

RWD is the more ideal platform, but you can make FWD cars handle very well, be a blast to drive and turn in fast laptimes. Hell I'm still slower in my BRZ than my ITR, perhaps I just can't drive (very likely). Maybe I learned on FWD first.. oh wait I didn't.

[Dave-ROR]

Originally Posted by ZDan

Regarding comment #7, for decades, people were brought up learning to drive with rear wheel drive vehicles. In the 70s/80s when more and more cars went front wheel drive, I don't recall any rash of incidents of rwd-experienced drivers having difficulties adapting to fwd.
Fast-forward to the S2000, and then again to the FR-S/BRZ, and scads of drivers brought up on fwd are crashing these cars left and right.
If you don't know how to drive, fwd is more forgiving.

True in the mass market where understeer setups rule the boardroom. Not true is more specialized cars. Most S2000 guys who wrecked cars that I knew of blamed the car because of it's "mad vtack yo" while flooring it leaving a red light in a turn. Sure, FWD would have been safer, but the driver was still an idiot. I thought this thread was about well setup FWD cars, maybe not

If you were brought up driving only fwd, you might be in for a rude surprise when you get behind the wheel of a responsive rwd car.

... or a well setup FWD car.

If you were brought up driving only rwd, you really don't have any worries transitioning to fwd.

Except when they 1) understeer into something because they bought an appliance, 2) lift throttle at the limits and snap-oversteer into a tree. I can't tell you how many RWD guys I've been on autocross and track with that LIFT when the rear slides out, a horrible idea anyways but it can bit a lot harder in a well setup FWD car, and even harder in a MR/RR car. Sadly these drivers are why almost all cars are setup for "safe understeer" now

FWD is inferior in braking due to overloaded fronts, RWD makes better use of its four contact patches.
FWD is inferior in cornering due to overloaded outside front, practically non-utilized inside rear, RWD makes better use of its four contact patches.

I've never done studies on the braking side so I won't comment. RWD often lifts the inside front, instead of the inside rear that a FWD car will lift. Certainly acceleration out of a corner is best in a RR car, then MR, then FR, then FF. LSD is basically a requirement for a FWD track car IMO.

Regarding wet conditions, my experience has always been that fwd sucks in the wet. Though grip is reduced vs. dry, there is still enough grip to get significant weight transfer such that wheelspin is more of a problem with fwd vs reasonably-decently-balanced rwd.

Hmm I don't get wheel spin in either without trying and get it with both trying.

The rest of the post still isn't on topic, that FWD can handle, be fun to drive and quick. :shrug: No one is argueing that FWD is the *better* platform.

[Dimman]

Originally Posted by Dave-ROR

FWIW we run a 'reverse stagger' on our chumpcar. Japanese tuners have done so for.. decades? Class rules often play a roll (for me at least - we run staggered because we have to keep OEM springs, dampers and sway bars). I ran square setups on my FWD cars and had zero understeer because of spring rate, roll bar and alignment tuning.

RWD is the more ideal platform, but you can make FWD cars handle very well, be a blast to drive and turn in fast laptimes. Hell I'm still slower in my BRZ than my ITR, perhaps I just can't drive (very likely). Maybe I learned on FWD first.. oh wait I didn't.

A late model RSX-S vs a BRZ on the same tire would be a very good fwd to rwd comparo. Very close to the same weight, power, geometry, target market... Someone should do this. Oh, and with telemetry, show where each one has their own advantage.

What are the class restrictions on the ITR? Do you think you could improve times significantly with more front tire?

[wheelhaus]

Originally Posted by Dimman

A late model RSX-S vs a BRZ on the same tire would be a very good fwd to rwd comparo. Very close to the same weight, power, geometry, target market... Someone should do this. Oh, and with telemetry, show where each one has their own advantage.

What are the class restrictions on the ITR? Do you think you could improve times significantly with more front tire?

Modified magazine just published a comparison between a FRS and a Civic, not sure which version. IIRC they wanted to compare mods for effectiveness between the FF and FR platforms and track test them; the same logic dorsnt always carry over. I haven't read it yet but they usually have good technical insight and should make for an interesting article.