Evo: GT86 VS MX-5
 

Cool. Thanks.

Interesting data in this video about the new Miata giving up time to the GT86 on the straights.

C&D just had its annual Lightning Lap at VIR. The new Miata was more than 2 seconds slower than the BRZ. ND Club-Spec Miata @ 3:20.8 vs. BRZ @ 3:18.6.

I think the data is showing that the Twins will be faster at longer tracks (e.g., VIR), and the ND Miata will be quicker at tighter/twistier tracks (e.g., SOW).

Still all about the tires. The reason the BRZ is better at so called faster tracks is because handling is not as important, so tires are not as important.

What are you trying to say? So the brz IS faster at longer tracks. But at shorter tracks?

I think what he's trying to say is that on shorter tracks tire grip becomes more important and that the twins give up tire grip, well on stock tires anyway.

The new Miata also has a stronger torque-to-weight ratio than the Twins, so I'm guessing it's pulling out of slower corners better (in addition to having more cornering grip as you mentioned).

The Twins are probably making up ground towards the end of straights where they can stretch their legs and use their aero advantage.

I like this comparison the best so far, very positive on both, less negative on one over the other in any category.
Highlighted the biggest detriment of the 86 for me stock, the built-in understeer and I'm glad to hear praise for the ND's engine, I was a little worried that the SkyActiv would fall flat.

:bellyroll:

I'm saying both cars are awesome, and if you put them both on the exact same tires the results are going to be identical. Every one of these comparisons have been close enough to point to the tires being the only real difference. The lighter weight of the miata is gigantic and helps in tighter corners and tracks but it doesn't look like it makes more of a difference than the difference of the tires.

The fact that C&D actually had the BRZ lapping faster than the Miata is surprising and it points to the BRZ engine is better and that the tires are a gigantic weakness.

People that laugh at pointing to the tires are living decades ago, tire technology is truly amazing, and the right tires can make even the worst car handle really well.

An 86 'upgrading' to the same class of tire that comes on the Miata was worth 0.2 seconds around Willow Springs, the track that the ND came out on top by ~1s.

Skip to 6:00 to get to the point, note that the S04's tested are listed as performance tires, the S001's spec'd as OEM on the new MX-5 (same tire around the world so as tested in the UK as well) are listed as low rolling resistance per Tirerack.
[ame="https://www.youtube.com/watch?v=FSqWD5BSeoY"]Testing Tires with Subaru BRZ, Ford Mustang & BMW 328i! The Downshift Ep. 65 - YouTube[/ame]


Yup the tires would have put them neck and neck in this EVO test for sure, but the Miata has 83% of the weight and ~95% of the engine of the 86 and as mentioned in every video a much more competent suspension setup off the showroom floor (double wishbones give it a noticeable advantage in front end grip as explicitly called out in this video that the 86's front end is lacking in comparison). Tires won't overcome that in a test of handling as shown above where the 86 is on similar rubber to what the ND comes spec'd with (actually bigger rubber at 215 vs 205) and only get marginal improvements.

The Primacy's are seriously underrated.

To be fair, there are tests that show the GT86 gains 2 seconds on a ~1:20 course upgrading to RE050A's (also same class of tires on a stock ND Miata), so there's evidence going both ways. Not all max performance tires are the same. I don't have any personal experience with the S04's in the TireRack test, but they could just be particularly crappy MP tires for the category.

Maybe so, but the S001's were chosen as the baseline OE tire (in run flat options) for the BMW in that video, now a good chunk of the time (0.7s) gained going to another Max Performance tire (Yoko V105) was from ditching run flats but I think part of it is also ditching a tire classified as low rolling resistance.

"Max Performance" Tire also includes the MPSS (which can give some 'extreme's' a run for their money), you're right there are great tires and mediocre tires in every class, most people who care aren't futzing around with ~300TW options so it's hard to guage where the S001's fall in line, but the fact is that Bridgestone calls that a LRR tire and the S04 description babbles on about performance applications...

Edit:
http://www.tirerack.com/tires/tires....+Pole+Position
http://www.tirerack.com/tires/tires....l=Potenza+S001

Watching the video a few notes:

The cars as equipped for the test were essentially a draw at the track. The MX-5 is absolutely tiny inside with the top up and that body roll, wow. It was also noted that the Miata was optionally equipped with an LSD.

The presenter made a very clear point that the GT86's Primacy's contribute to it's both its' under and oversteer. In his words:

"the tires are made for sliding". "The GT86 will maintain a slide in a way the Miata will not". "The MX-5 will also slide around but you can't do it on power alone".

Most importantly the conclusion at 9:10:

"In the end just one tenth of a second separates the two cars. The MX-5 may be 40 horsepower down on the GT86, but it's much lighter and it has grippier tires. So the Mazda is the faster of the two just, but the GT86 was more fun. "

If the MX-5 gets an optional LSD upgrade then equal tires should be considered for the GT86 which would obviously make the 86 quicker at probably any track than this Miata.

Yeah you could be right. I don't put much emphasis on treadwear ratings, but it's notable that Bridgestone makes all 3 tires and rates the RE050A's as 140 TW vs. 280 TW of the S001 and S04PP.

It could be that the RE050A's are much stickier MP tires than the S001 and S04PP.

My personal experience is that the 86's understeer is suspension and alignment induced, adding grip reduces the oversteer and amplifies the understeer if no other changes are made.

But I'm just another fool on the internet.
:cheers:

The Miata is a great car, I'm not saying it isn't. If it came in a hard top and I could actually fit in it I would probably be buying one.

And tire "classes" are not good guidelines. So much variability even from the same tire manufacturer.

That is a great video.

I remember watching a similar comparison video to that Mustang and BMW one a few months back where the car (FR-S or BRZ) became slightly faster than a stock WRX around a course once it put on high performance tires where beforehand it had around a 2 second disadvantage.

I can't seem to find it again though but it was probably compared to the older WRX with the EJ engine rather than a newer one with the FA20 engine.

Obviosly at way different tracks, but at VIR, according to the new Car and Driver, the BRZ beats the Miata by 2.2 seconds.

But both were beat by a Jeep Grand Cherokee, haha.

Road and Track, that 2+ second advantage was also seen in the video I posted as the Bridgestone RE11's, as well as the ZI SS in the road and track article were designed for competition use in various 'Street Tire' classes (SCCA, NASA, etc.) vs. the more road oriented tires sold as OE and used as intermediate steps in the comparisons. Also worth noting that both those compounds have been phased out and replaced by faster rubber (ZII SS and RE71R).

http://www.roadandtrack.com/car-cult...ransformation/

Thanks! So that was it; an article rather than the video that I misremembered.

I will have to thank your post for finding that once I have more than ten posts. :P

First of all body roll is not a bad thing necessarily. At least not in terms of performance and ultimately the MX-5 is going to be more forgiving on bad roads.

I do agree that tires could have changed the outcome, but it is what it is. These are the stock tires that come on the various trims that the press gets. If you start modifying the stock equipment for a test then where does it stop?

Perhaps Toyota/Subaru could sell a "track edition" that has better brakes, lighter materials, better tires, etc.

Didn't say it was bad, just that it was there in large amounts.

To your point, the LSD on this Miata wasn't stock equipment, it was optional and added for the test (just like you mentioned, where does it end?).

Subaru offers a BRZ Ts model which would be faster as it comes with everything you mentioned and all very similar to the U.S. Club edition MX-5 Mazda has been sending to the press in the USA. The BRZ Ts includes Bilstein shocks, 18" 225 section Michelin Pilot Super Sports and a Brembo BBK. Unfortunately, that car is only available in Japan ATM.

http://www.autoblog.com/2015/04/03/2...rz-ts-w-video/

Some quotes from the review

"I drove a few laps of the Suzuka's truncated east course in the standard BRZ before familiarizing myself with the tS (and, later in the day, running the full 3.6 miles of racetrack). For all the work put into improving lateral stiffness, the most noticeable change is the grip from the better tires. The added traction had me pushing harder and driving faster through the esses of Turns 3 through 7, and boosted my confidence carrying speed through the breathtaking Turn 15.

Where the standard BRZ's rear end gets loose with aggressive throttle prodding, the sticker contact patches on the tS keep the car in line at far higher loads.

...Overall the BRZ tS was significantly easier to control than the one that's currently on sale in the US. Especially because I was learning the track as much as the car, I noticed that mid-corner corrections were easier to execute in the tS, with high-feedback from the steering and chassis putting me in close connection with the rubber and the road.

'll admit, going into the day I was a little concerned that a stickier BRZ would be more competent but less fun to drive. I've always admired the way a bit of softness in the Subaru makes it more charming on real-world roads when more serious sports cars sometimes leave me cold.

I needn't have worried. I never climbed out of the cockpit without a grin stretching across the too-small Japanese-style helmet framing my face. The magic STI made in tuning this car, with the company's deep knowledge and team of 50-plus engineers, is that the is tS hasn't lost or changed the BRZ's essential character. Home-brew tunings may strike that same balance, but they're just as likely to upset it – yet another reason to get a tS clone stateside ASAP."

another review here: http://www.motortrend.com/roadtests/...s_first_drive/

And an older comparison of fully prepped and tuned 270 HP Turbo NC MX-5 vs. a GT86 with TRD upgrades and most importantly Michelin Pilot Sport 3's. Almost no power mods as TRD only had intake and catback at the time. The MX-5 with impressive HP output and built suspension manages to be 1.8 second faster lap 1:10.7 vs.1:08.9.

Still for an 8 minute long video, the first 4 minutes the reviewer spends most of the time talking about the difference the tires make for the GT86, and then mentions it again at the end of the video. On this car, for lap times, the Primacy's suck and majorly hamper the car's performance. Good thing for us, that's a cheap and easy fix to an already very capable car.

https://www.youtube.com/watch?v=ytxJvuTy8As


Looking at Fastest laps, what looks to be a stock GT86 on Primacy's turned laps 2.1 seconds slower at Blyton Park (driven by Tiff Nedell of all people) 1:12.8 from the test above's "TRD" GT86 on MPS3's (1:10.7). Working on confirming the source. The Primacy HP tires handicap the 86 more than its' suspension configuration. http://fastestlaps.com/laptimes/50dc6427ab072.html

I think I agree with both viewpoints: The Primacy tires ARE the biggest weakness of the 86, and they ARE underrated.

They are underrated because they happen to be available in one specification of the Toyota Prius, hence "it comes on Prius tires". That's not really a fair representation of these tires; they aren't comparable to your average all-season econobox tires. Yet, they aren't comparable to many UHP/MP summer tires, either, as evidenced by the various tests showing 2+ second improvements on ~90-second lap times.

So you guys are all correct. :thumbsup:

While the tires are undoubtedly an important factor in the two cars performance there are other reasons that the MX-5 may be quicker around a tight course and the twin faster on a long course.

Tthe MX-5 has a very flat torque curve which may make powering out of corners easier. It is lighter so braking distances will be shorter and cornering speeds may be even higher than the twin. All these would give it an advantage on a track with multiple turns and short straights.

On a long track, the higher HP and redline of the FA20 will come into play. The extra weight is not such a disadvantage once you get it moving and if there is less braking. The final advantage for the twin on the faster and longer course would be the superior aerodynamics of the coupe compared to the convertible.

I hope to see both of these cars mixing it up in the world of motorsports for years to come.

Rampage nails it!

This, aero will be better on the 86. Makes a pretty significant difference on longer straights.

Notice how the Miata (I'm sorry, I'm never going to stop calling it that Mazda) loses a lot of ground in the hard S corners? Lots of body roll makes transitions much harder.


The low CoG of the twins is also coming into play with the roll, it's not like the Miata is that nice on rough roads...


For some reason I can't quote DAEMANO's post, but the Miata has the option of the LSD from the factory while outside of Japan, the twins don't have an option for better tires.


I've been searching far and wide for track times from the tS with no luck. We all know the tS is going to be quite a lot faster than a normal BRZ, but I really would like to see the numbers...

Thou tire is a factor, but actually base gt86 will be on the same time as ND with it's 16x6.5 205/55/16 tire (not primacy hp, Yokohama Db 205s)........Cuz that 16inch base tire/wheel along makes 86 roughly 1 sec faster.

You would think so. But surprisingly, the Miata's CoG is only half an inch higher than the 86 (C&D measured 18.0 and 18.5, no I don't have the links handy). The 86 is also a bit wider, so the difference in "aspect ratio" works out to something like 5%. The body roll is mainly due to spring and sway bar choices. In Japan, some of the trim levels don't even come with a rear sway bar.

And the ND has enormous amounts of suspension travel. The body roll is by design, and definitely intended to improve the ride quality. But I agree, it means transitions are going to be slower, and it will punish non-smooth inputs.

^^

Yep agreed, body roll is generally never a positive. It's just a byproduct of suspension compliance at a given CG height & track width.

There are very few scenarios at the track where you'd want to prolong weight transfer, and that's really at the far extremes.

The point I continue to not agree on is that these types of comparisons are biased because Mazda offers the option from the factory of Brembo's, LSD, etc and Subaru/Toyota and (in the US/Europe) the comparisons are done with the stock tires. It is what it is.

It could very well be that the Miata has too much body roll, but the point that stiff always equals better is what I was trying to make. It is simply not true. Some bodyroll can result in adding more mechanical grip which can be a good thing. In the case of the Miata it does seem some as simple as a better sway bar could really improve the car.

I read somewhere that the tires for the Toyota 86 is not standard across all areas in Australia, and that the lower trims for the car in parts of the world sometimes don't have Torsen Limited-Slip Differential (such as the automatic 86 GT in Australia).

Hate to nitpick, but it's not the body roll that's adding grip in that scenario, it's the suspension compliance.

Body roll is an effect of weight transfer, it doesn't affect weight transfer. It definitely has poaitivrs and negatives. I know I've replied this to you before and somehow you never belive me, so I will try to spell it out a bit more.

So first off, you are correct that more compliant suspension ie lower spring rates gives more mechanical traction. More body roll is an effect of having more compliant suspension if you don't control it with sway bars.

But with double a arms, body roll has a benefit of giving you better camber curves. If you look at all the posts on the miata forums, the miata gains more than 1:1 camber for body motion, which is a very good thing. You want as little camber for braking and acceleration, and the appropriate camber for cornering. You want all four tires to be at like 5 degree camber with respect to the ground, which means negative camber for the outside compressing tire and positive camber for the inside extensing tire.

If you deal with a constant radius circle, you actually get maximum lateral grip with the softest springs possible and body roll to maximize the work of the unequal length a arms.

Now the negative to rolling around a lot is it takes longer in transitions and drivers don't like it. In autox where you have lots of transitions, sway bars usually take of tons of time wheras they usually do nothing or hurt on road racing. Drivers, especially amateur drivers really don't like it because it takes time to load up the weight so you have to be purposeful and have finesse when putting in driving input. That's why amateur drivers usually like super stiff front sways, because that responds to driver input faster. Also why amateur drivers like super stiff compression on the shocks. It will turn in quicker but your maximum traction suffers. What drivers like is not always faster.

You say but race cars don't roll much! But they do. The missing part of the equation is the ride height. Lower cog is super important, and the point at which the losses of too stiff suspension and loss of suspension camber control overtakes the gain of lower cog is about 2-3" of bump travel. But now in the era of aero, the benefit of aero overtakes any suspension and the best ride height in our aero era is basically as low as rules will allow.

If you look at videos and pictures of race cars, you will see the roll as much as their ride height will allow until their front splitter would hit the ground. If you look at f1 cars from the pre aero like 1950s you will see they have 2-3" of bump travel and roll the maximum possible.

So where does that leave the mx-5 and fr-s? So because both are street cars, they both have about 5" of bump travel for clearance and cargo purposes. Mazda, as it is usually focused on road racing, set up a suspension for road courses. So it has soft springs and big roll to take advantage of the double a arms and the huge ride height since it has to have it anyways. So people complain about the roll but drivers like pobst can turn out good numbers. It however will hurt the car on autox

The fr-s were designed for driver feel and not for time. The McPhearson fronts basically get nothing from roll so they have a super flat car with no roll and high low speed compression damping that drivers love.

Side note the reason why hp is more important than than torque and hp/weight ratio on high speeds is that air resistance is like subtracting a net jp from the car. So at 80mph its like -50 hp from the car. -50 hp out of 170 to 120hp is significabtly worse than 150hp.

Also the miata has to run w top down on road courses and its cod is terrible compared to a hard top.

I didn't quote the long post, but you're still basically looking at it backwards. The reason that the dynamic camber curve of double-wishbone suspension is advantageous is that it compensates for the positive camber induced by body roll.

Not just that, but body roll introduces its own weight transfer and reduces total overall grip. Also the more body roll you have, the longer your weight transfer takes.

Again I'll state this simply. There are no performance advantages to body roll. You want suspension compliance for grip over surface irregularities, but not the body roll that comes with it. Body roll is just the negative byproduct of building in suspension compliance. Thankfully it's possible to reduce body roll without affecting suspension compliance by lowering CG height, adjusting roll center, etc.

You'll never hear of a race car engineer trying to build in as much body roll as possible on a chassis. If they did, you'd see race cars tipping over everywhere. The whole concept is frankly a bit absurd.

Did you even read what I wrote? Do NOT use common sense to talk about vehicle dynamics. I explained every single one of the objections you brought up. Please explain why it is not valid. Please do some real reading on vehicle dynamics.

Sorry I am typing on phone so there are typos and I can't format this point by point but I'll go point by point

Uneven length a arms more than compensates for body motion. For each degree of body roll compression, the miata suspension gains more than 1 degree of camber. This is very good as tires want 0 camber in a straight line and like 5 degrees of camber in curves (-5 on outside and +5 on inside). There is no way to achieve this with McPhearson. I can't find the nd numbers but the na/NB miata get about 5 degrees of camber for 3 degrees of roll. So if you roll the cars 3 degrees you end up with -2 degrees on the outside and +2 degrees on the inside. If you have a macphearson you will get more like 2 degrees per 3 degrees of roll so you will end up with +1 on the outside and -1 on the inside, which is bad. So w a miata if you run -1.5 static you get -3.5 and +0.5. W a macphearson you'd run more like 3 and end up w -2 and -4 which is not as great and also a static -3.

Roll angle does not affect total weight transfer in any meaningful way. The fundamental equation for total weight transfer (lateral acceleration x cg height x weight/track width) does not include roll. If you want to talk about instantaneous vs geometric cg centers, the effects are trivial. The fact that you think roll affects weight transfer makes me think you havent read up on vehicle dynamics as that is one of the most common incorrect assumptions that all books and instructors take time showing how it is wrong.

Soft springs more roll and lower compression damping all affects how long transitions takes. And yes it is bad, but there are tradeoffs for each.

You think about suspension completely backwards. You don't tweak roll with cog and compliance. Compliance is limited by cog. You need as soft as springs as possible, but you need to not bottom out. So with 2" bump travel you end up w 2.5 wheel rates and a super stiff ride. This causes you to have not too much roll. If you still need to reduce roll to not scrape you use roll bars.

That is why race cars don't maximize for roll. You have a low cog and low bump travel and low clearance. They roll as much as possible given those constraints.

Street cars have different constraints as they have way more bump wtravel than is ideal because of practicality concerns. Because of that they can roll more than you see race cars do. and if you have double a arms it helps

Roll angle is trivial to decrease. Just throw in bigger anti roll bars. There isva reason most road racers don't really care for it too much and a lot pull out oem roll bars and why autoxers put in huge ones.

I know you hate me and think I some sort of troll, but you really should believe I've done my reading.

Whoa I think you need to step back and relax, you're taking this way too personally. I don't hate you and it doesn't matter whether you're a troll or not. Just debating facts here.

I'm surprised in all of your reading you haven't come across explanations of how body roll adds weight transfer. There are plenty of materials out there that explain it. In fact, your formula citing to CG height states it right there, you just don't realize it yet. If you think through the effect of body roll on CG, you'll see it.

http://www.autozine.org/technical_sc.../body_roll.jpg


As for the camber curve on the Miata being greater than the degree of body roll, of course. You have to take into consideration at what angle the tire is reacting the way the suspension engineer wants (temps, grip, wear), as well as deformation of the tire. None of that changes the accuracy of what I said.

No offense, but I'm not going to touch your statement that "compliance is limited by COG". Your statements about CG height and swaybars are kind of missing what I was saying. It's more than I want to address right now.

At the end of the day, if you want so hotly to believe that body roll is a good thing for handling and somehow adds grip, that's fine by me. It doesn't really matter what you or I believe, so let's just agree here to disagree.

Jeez.