Comparing car lap times: Equal tires?
 

What is your opinion?

I say that if you are comparing factory cars (ALL OEM) an initial test or comparison should be made as the cars are delivered from the factory for baselines and off-the-lot value etc.

However!

For sake of the Poll;

Question: If comparing cars in which braking, accelerating, cornering and lap times (especially lap times) are compared for the sake of comparing the car; is it or is it not logical to put the cars on equivalent tires?

My position: YES. The tires should be the same if not of equivalent performance to most closely get an accurate representation of the different cars as a "whole" that are being compared.

example:
At my local track a completely stock S2k in my hands can do a 2:06 lap time on Potenza S03's. A FRS on Prius tires does a 2:10 lap time. Considering the performance difference of the tires do I, or do I not have a legitimate representation of the performance difference between the 2 cars? I say I do not.

If the FRS was on Potenza S03's (in OEM size) and then turned a 2:08.5 lap time I could definitively say the difference between a stock S2k and a stock FRS is 1.5 seconds and presents an accurate representation of the performance of the 2 cars.

I think it's common knowledge that some manufacturers put really really sticky summer tires on their cars stock so that in magazine reviews they will come out with better numbers even though the suspension design may not be as good as some of the competitors.

Knowing that, I think comparing the grip level the tires provide when looking at lap times is important. I think it's telling that the twins on stock tires are pulling skid pad times and lap times that are comparable to some other performance cars on much stickier tires.

Nathan

As long as the fact is disclosed, then I don't have a problem with it. Tires imo, being wear items will have to be replaced anyway, sure it doesn't have to be when the car is purchased though. And if it is disclosed, it is something you can consider having it replaced soon after purchase if there is a lot to be gained from it.

It all depends on what you want out of a review. Tires have a huge effect on performance - heck, I could show you how a RWD car on winter tires could easily outhandle an AWD on summer tires through some snow, but the result would prove nothing about RWD vs. AWD and everything about winter tires vs. summer tires.

To take two cars directly from the manufacturer and compare them "just as they are" usually says nothing about the cars themselves. But mags aren't about to buy several sets of tires for every review to make sure the tires variable is taken out of the equation. Instead, they test them as is and add some fluff piece at the end about "could use better rubber", or something similar to make a statement.

So for that reason, the tires should be matched as closely as possible - no new size orrace-only tire, just something with a similar rolling resistance should be fine. But I can't imagine many car mags could afford those kind of costs.

Absolutely put them on the same tires. Especially considering factors like these: it's funny you mentioned the Potenza S03, because that tire (AFAIK) is discontinued. So if you were trying to compare an E36 M3, MR2 Turbo, S2000 or any other car that came with these OE tires, you'd have to change them to something else. Putting both cars on the same tread compound gives a "constant" in the comparison that allows the true performance of the car to be tested.

In my opinion, there should be three constants: track conditions (time, weather, temp, altitude), driver, and tires. These ensure the cars are being tested properly and fairly. It also allows us to find faults in the car's systems that may not have surfaced otherwise. For example, if anyone remembers the Car and Driver test where the NISMO 370Z lost it's brakes during a test and crashed into a wall. Nissan/NISMO ended up offering a performance brake pad option for the NISMO Z after that snafu. Had they changed brake pads or fluids this may not have surfaced. In fairness, perhaps after that they could have compared it to other cars while using the NISMO pads to test its performance.

Admin, fatoni's vote was counted thrice! :lol:

It's OK if one wants to compare "showroom" cars. But if you want to compare the cars, and not "showroom packages", you must use similar tires.
And before anyone would complain this is "unfair" (like not handicapping the weakest horse but allowing it to carry the same weight as the best/fastest one would be regarded as "unfair"): some manufacturers purposely put high grip tires to hide their car's (chassis) deficiencies, and make them look better. Toyota did the opposite.

Same tires FTW. One of the things I loved about hot version and the Tsukuba 5 lap battles was that each car wore semi slicks. Even in the rain LOL...

i dont know why you keep bringing me up. i didnt even vote. this whole poll misses the only point i was trying to make. i could just as easily make an example out of the v6 mustang and its 114mph speed governor as an example of manipulating the ecu for an accurate comparison.

manufacturers dont put good tires on cars to hide things, they dont use good tires to look good in comparisons. they use good tires because they want to sell a good car. the post before you, its shown that tires are going to show issues rather than hide them.

Even if you use the same brand/type of tire, different cars will have varied sizes. There could even be compound differences across tires in the same line based on size. I don't think it would be worth the expense. If one car is on 285/35s and another is on 205/50s, it still won't tell you much.

1: ecu programming is not as common as the replacement of rubber in your car. Especially because tires are wear items that you will replace on every car and ecus are often never changed by the customer. And besides, taking the top speed restriction out of an ecu is not as imoactful as changing to different tires.

2: you're naive if you think that car makers don't put extra-grippy tires on a car to mask other deficiencies in a platform. In fact, because tires are such a predominant performance-affecting variable, I'd even better that some car-makers purposefully cut corners with their platform because they know that tires will make up the difference. If we ignore both of our extreme arguments, however, the reality is probably somewhere in the middle - tires have a profound affect on performance and should be negated as much as possible to determine the capabilities of the chassis.

1: this isnt about what is common. it is about what is accurate. looking at things like the c&d lightning laps with the mustang on that limiter for over 9 seconds sounds like it is a pretty big deal.
2: sticky tires generate more force than less sticky tires. what situations are you talking about where less stress is going to show platform deficiencies? the closest thing to a test like this ive seen has been done by the folks over at 949racing and fecompetition. in that test they say this: " In this configuration, the car has way more grip than it does suspension control. Its fast, but sways through corners in a manner that isn’t confidence inspiring when trying to go fast." about using sticky tires on an otherwise stock frs. if companies really thought like that, i would wager that we would see much wider tires coming off the lots.

fatoni, that was a joke; obviously you can vote at most once.
Please don't forget about my "what is stock" question: is it the Michelin Primacy HP equipped GT 86, or the Bridgestone Turanza equipped one?

Manufacturers would do lots of things to hide deficiencies, IMO. Tires, "sport" suspensions, electronic stability controls... this way they can put apparently impressive numbers with a completely unremarkable chassis. Of course, it won't always result in stickier tires being used, and it's not always about performance.

The post before me was talking about the undersized brakes of a stock (incl. tires) NISMO 370z, from what I understand. And it was a good thing that such issue was discovered.

TheRipler, still it would be better than comparing Turanzas with Yoko A048s, or something.

On one of the spectrum, if you work for a car magazine whose audience is the general public, then you should compare cars as they come from the factory (stock tires). Then again, to the general public, track times should mean next to nothing anyway.

On the other end of the spectrum, if you're into autocross or tracking, then you should absolutely compare cars on equivalent tires. Why wouldn't you? Tires are probably one of the most commonly changed-out consummables on cars that see track time and can make a significant difference in handling and laptimes. For any kind of competition event, tires are largely equalized across the board anyway.

I would initially agree to equalize the tires to compare cars but from a realistic standpoint it is a modification to change tires from stock. People on this board are biased because, well, it's an FR-S/BRZ board and the car comes with pretty lame tires so of course most will say "well just swap out some good rubber!"

If you look at the Miata the stock suspension is extremely soft and rolly where you could swap in some shocks for the similar price of a set of high performance tires. The 350z/370z both came with terrible brake pads from the factory so naturally most owners would say to swap in some decent pads.

Still, as far as modifications go, tires are one of the only ones that can be applied to every car, not just a specific car, which is why I agree that they should be equal among car comparisons in the end.

It's been fun having a devils advocate with such tenacity.

The part in bold actually proves the premise regarding the tires. The point is "What are you testing." Are we at the Bonneville Salt Flats? If so, then yes, if one the of the cars has a speed governor and the other doesn't should we remove the governor? UH DUH! of course we should otherwise there's NO POINT IN DOING THE COMPARISON. (sorry for yelling).

So here I am at dinner the other night with 10 other S2000 and former S2000 owners (old group that gets together once a week) and we're talking about lap times at a new track in town. They wanted to know what my best lap time is at the track in my FRS since I'm an instructor there. I told them my best is a 2:10. They recently did a track day as a group and only 2 guys has stock cars (except tires) and the fastest of the two was on Dunlop Star Specs but the rest of the car unchanged and I think he did a 2:06. Is the FRS 4 second slower at that race track than the S2000? No. Is the S2000 4 seconds faster? No. All we can definitively determine is that

- The FRS is 4 seconds slower with HP Primacy tires than an S2000 with Dunlop Star Specs. We learned that there's a difference in lap with those two variables and those 2 drivers.If we put both cars on Dunlop Star Spec's (which I want) and did laps with the same driver in each car and then the FRS did a 2:08 to the S2k's 2:06 then and only then could we definitively say the S2k is 2 seconds faster than the FRS.

And the comparison holds water because like stated above, we can't compare the cars with OEM tires because the OEM tire for the S2000 is not produced anymore. So then what? (rhetorical).


As it stands now a vote of 33 to 5 for similar tires is essentially proof enough.

you arent funny

however the car they test comes is stock. look at each review and see what they used.

its strange that in an attempt to isolate tires from other things that change the car you actually lump them together with electronics and suspension. you act like when a manufacturer uses good tires its sandbagging but when you want to use good tires its fair.

what is it that you think the chassis is responsible for? what makes one chassis inferior to the next? saying companies use suspension, tires and electronics to hide deficiencies has me confused as to what youre thinking

it sounds like you never understood my point at all. im not saying switching tires isnt a useful tool. im saying that its one of many useful tools. you dont need to be on the salt flats to run into that limiter. if i can approach 114 in an ae86 at sow and surpass it in a stock itr, the 300 hp mustang will be on that governor a lot. i never said the comparison doesnt make sense. it just makes as much sense as a lot of other comparisons. tires will change lap times, so will that governor. i agree that tires and drivers are variables. what i have an issue with is that you make an argument like brake pads, shocks, weight etc. arent variables. i dont know how to respond to that.

a poll is never proof of facts or reason. its a proof of opinion and nothing more. even if it was, this is an frs forum. the data was bound to be biased from the start.

again, this poll was never about the issues that i had with peoples reasoning. the problem i had was that people are using a specific argument and only accepting a part of the conclusion that the argument leads them to.

fatoni, so if I'd buy a Bridgestone Turanza equipped GT 86 and I want to switch to Michelin Primacy HP, and compare my car with others (let's say a Mustang with PZeros, or a high grip tires in any case) - I shouldn't do that because my car won't be "stock", and it wouldn't be fair; I should keep the all seasons instead.
OTOH, another person who bought an identical GT 86 but with Michelin Primacy HPs can do it, because his car is "stock".
So the exact same car is both stock and modified. Thank you.

I don't have to artificially single out the tires; as I've already said several times, they're singling out themselves since, you're supposed to change them - and quite often, with different types (it can even be required by law). Do that with e.g. suspensions and bye-bye warranty, or worse. In the same time, there's no guarantee that:
- when testing, the exact same model of tire as provided when the car was bought is still available
- the dealer would keep delivering the car with the same tires, during its entire lifetime

An example of hiding deficiencies is the first A Class. Its rollover issue was "fixed" not by a new chassis, but with wider tires, modified suspensions and ESP. Even if the end result was meeting standards, I would still call that chassis "inferior", from a stability point of view.
But it can be e.g. a hot hatch, as well - take a "pedestrian" chassis and "make" it into a sports car, instead of designing a dedicated one. Or a Mustang which puts down excellent skidpad results, due to it's PZero tires.

Sandbagging? As in hiding one's strength?

By the way, we are understanding your point perfectly; we just disagree with it (but not with the idea of comparing cars with the dealer provided tires, if that's what you want to measure). It's you who doesn't even care about the points we're making.
And by the way, when you want something specific you'd normally use the single proper tool for the job, not all the tools you have, at once - or none at all, fighting the issue barehanded ;)

would you mind explaining my point to me then, because what you are saying doesnt provide any evidence you know where im coming from.

what about a "pedestrian" chassis is inferior to a "sport" chassis? i still dont get your point on that topic. as far as i can tell for performance, a chassis is to provide stiffness to allow the suspension and other components to do their job. in every type of vehicle stiffness is a good thing so they all have the same goal

If you don't understand your own point and must have others explain it to you, then you have a problem :p

So a very stiff bus chassis would be more than adequate for a sports car? I don't think so...

my problem is that your arguments are childish and incoherent. there have been a number of players in this talk and what usually happens is that we end up with different opinions and bow out. you, on the other hand, keep bringing me back up. instead of discussing my points you talk about me.

no a bus isnt a good sports car for many reasons but things like the original fairlady, integra, coopers (old and new), cobalt, nissans multicar platforms, evo, wrx, civic, etc have all been adequate sports cars. despite coming from pedestrian backgrounds.

But you can't let it go either, can you? ;) Remember who started it, on the vs 370Z thread...
And even now, you were talking to me as if I would be unable to understand your point and just pretended I did. Surprised about the response?

My arguments might not be expressed very well but are quite consistent, IMO. They can be grouped into two main lines:
A. tires are not a constant, and they're meant to be changed (no OEM code, same cars can be delivered with different tires etc)
B. why same tires comparisons are valid (depending, of course, in what we want to measure).

And yes, those cars you're mentioning are/were quite good sports cars, because a manufacturer can hide / work around such deficiencies (completely consistent with what I've said). Provided we're not talking about a bus chassis ;)
It also depends on what kind of car you're building, of course. You can't get a Golf (random example) and make an Elise out of it.
But you know such things very well.

A few clarifications about the 370Z:

-the brake rotors are not undersized, nor have they ever been. They're 14" people, that's more than large enough for a vehicle of that size/power!
-The upgraded Nismo brake pads and fluid did not solve the brake problem. It merely delayed it's onset.
-The brake problem the 370Z suffers from is a lack of air flow over the brakes.


As to this poll, I voted no. If you think all an automaker does it randomly slap on some tires as OEM and then sells the car that way then you are incredibly naive. When a new car is going through R&D the automaker includes tire selection while developing the vehicle's suspension. If there is a sport suspension with a more aggressive tire utilized you better believe they test those tires as well.

And that is why when you comparison test one car against another (or 2 or 3) in a magazine you use the tires THE VEHICLE WAS DESIGNED FOR.

Of course it is always worth noting what tires are on the vehicles being tested and often times the car magazines point out whether or not a tire is holding back a vehicle's performance. It is not to say that you cannot improve a vehicle's performance by putting on more aggressive rubber. However that is an AFTERMARKET modification and car magazines aren't often in the business of comparing stock vehicles against modified ones.

Kunzite, if an auto manufacturer offers more than one OEM tire for the BRZ/FRS (Bridgestones and Michelins) then the car is stock equipped with EITHER OF THEM. How hard is it to understand that one vehicle can have more than one tire choice stock? That's a decision made by the manufacturer.

2004+ S2000s (essentially the AP2) came from the factory on Bridgestone RE050s. And yes that tire is still produced.:thumbsup:

Disagree with that. A great set a tires can hide so many handling deficiencies.

Certain cars are actually tuned to work with specific tires.

like what kind of deficiencies?

About NIZMO 370Z brakes issue: you're right, thanks.

I definitely don't think a manufacturer would randomly change the tires. But do we know the criteria for their choice? I think the Michelins were a deliberate, well tested choice (made by Toyota&Subaru themselves); but why exactly were they chosen? Because the car won't drift with high grip tires? Because other components (e.g. brake pads, fluid, lines) would have to be changed as well? Because of EPA, threadwear etc? Because they have a good relationship with Michelin and are already using such tires in other products?
The Bridgestones could be just some all season tires which were suitable. We know very well the car is untouched...

The tires the car was designed for... which are those, for the GT 86? The Bridgestones or the Michelins? :p
Sorry for pulling your leg; but the thing is, we don't actually know which tires would be those. Maybe (very likely IMO) the car was designed to cope with much better tires; but in the end was shipped with the Michelins for various reasons.
Anyway, I hope my whole "Michelin or Bridgestone" tirade is able to prove a point: that even if comparing "stock" cars, it's important to know which tires were used; because tires are not a constant.
From this to "but how fast it would go, with the same high grip tires as the others" is only a step.

I can see a magazine (and its readers!) being curious about how the GT 86 would compare, with the same tires. Obviously, the dealer's tires should remain as a baseline.

Of course both are stock :) But IMHO the "modified" car (Bridgestones replaced with the Michelins) is better suited for a "stock" comparison, than with it's Bridgestone tires.

I couldn't agree more. If the BRZ was offered with Dunlop Direzza Z1 Star Specs you better believe that is how I would order mine!

BTW if you want a good comparison of the BRZ on stock versus aftermarket rubber check out the article on that in this month's Road & Track:

http://www.roadandtrack.com/special-...transformation

It's pretty sweet stuff. The FR-S goes from being slower around a track than the WRX and MS3 by well over a second to beating them both handily!

As an AE86 successor, this car carries an expectation to be able to drift, and with 200hp and super-sticky tires, would have left a lot of people disappointed. Also, those tires were chosen to give beginner drivers more feedback than your high-grip performance tire which gives less warning when it's at the limits of adhesion.

To say that the car's outright performance is held back by it's tires is an understatement. If the S2000, MX-5, or any other car were built with similar principles in mind, it would likely have mediocre touring tires as OE, too. Put the FR-S on RE050A's and stack it up against the S2000 and MX-5 (with the same driver, same track conditions) to get a sense of it's true performance against its competitors.

there are grippy tires that are equally if not more informative at the limit than the primacy. i do agree that it is a tire designed to let you enjoy the limits at a much more reasonable speed though.
the miata is the successor to the miata. mazda made a deliberate decision to not give it any more grip than it had in the 80s. also the miata was built to appeal to a wide audience and because of it, they suck in stock form. to get a sense of the miatas "true" performance youre probably going to need at least a set of rx8 sways.

yeah yeah yeah... but as soon as you saw the tire S03 mentioned you knew... you knew.

One in every group I guess.:bellyroll:

1: Yes, it is about what is common. And it certainly is about accuracy. But you found *one* example in the C&D Lightning Lap where the ECU speed limiter impacted a car's performance. You know how many lap results were affected by the tires on the car? Every singe one of them - I can even point to every single review where they've tested different tires on the same car (I shouldn't even have to find sources for this) and had drastically different lap times around a track. That's a big deal. Is the ECU speed limiter a big deal? Not even close to being relevant for 99% of the car tests that happen in magazines.

2: I don't even know what we're arguing about here. Tires make a profound difference in performance of a car, are chosen because of a specific price-point the automaker is trying to hit and at the same time maximize traction and control that wouldn't otherwise be possible with the chassis, and are easily the fastest wear-items on any car (besides oils and filters, I suppose).

DarkSunrise said it best - if you're the general public that doesn't care about lap times, then keep everything stock. If you're an autoXer, you would appreciate the comparison of cars on similar rubber. I'm fine if you're in the former group, but it doesn't mean those of that would like better comparisons are wrong in any way.

Cut a couple of tenths 0-60.

A few more tenths 1/4 mile.

Braking distance.

Skidpad rating.

If anything, I was surprised how well the Fr-S did with the summer Prius tires.

just changing tires and nothing else isnt any more fair or informative than keeping things stock. my providing one example of an ecu isnt any less valid than the one example of swapping tires on your one frs. take a look at miatas. on equal tires the na8 is faster on equal tires but when you look at the rules, the na6 is the faster car in the classes. changing tires doesnt make any more sense than changing other things too. thats all ive ever been saying.
its impossible to equate those things to a chassis alone. if you change the tires on any chassis those numbers will change. quarter mile times, braking distance and skidpads have next to nothing to do with the chassis. if by implying that improving those statistics via tires is hiding chassis issues, then every single car ever has chassis deficiencies.

fatoni, you're not only claiming that using the same tires isn't "fair", which is debatable; but you're also claiming it's not informative.
(e.g.) Skidpad figures close to an Elise are very informative. But you know what isn't? Changing many things at once, because you don't know what's doing what.
I can't agree that purposely changing one specific thing, that's not a constant during the lifetime of the stock car, is the same as changing many other things at once.

:thumbup:

thats not at all what im saying. what i am saying is that it isnt any more fair or informative than keeping the factory tires or changing some other thing.

skidpad tests are not only next to worthless as far as handling goes but they should only be compared on the same surface with the same radius. close to the elise skidpad numbers? was that the .95g or the 1.03g. the zr1 posts higher numbers than the elise ever did. is the corvette a better handling car than the elise?

you dont have to agree with anything im saying but being able to identify what is making a difference has nothing to do with saying changing tires and only tires alone can be changed in comparisons

While you're right about equating that to a chassis alone, getting high quality tires still hides deficiencies.

Tires have little to do with the chassis, pending setup, suspension geometry, etc.

It's not that every car has a chassis deficiency. That's too extreme a point. The modern chassis of cars nowadays are tremendously better than cars of yesterdecade.

The point is, great tires inflate great results on track tests. Those numbers are what most car buyers actually look at.

The more informed enthusiast will want to see lap times of different chassis with the same tires. Why? They're more likely to use the car for that given application.

My point is this. All sports cars for sale in 2012 have a great set of grippy tires except one car. The FR-S. So, when that "average tire" still puts up huge numbers for typical testing, it says a lot about the chassis, since the tires aren't inflating results. Rather, using narrow 215 tires that belong to a Prius show how much potential the chassis actually has.

great tires will inflate results on both great and shitty chassis. if it does the same things to both ends of the spectrum, how is that hiding anything?

@fatoni:
Taking your words exactly, "it isnt any more informative than keeping the factory tires" - that's not true. It is very informative, if that's the piece of information you're looking for. Guess what: that's the piece of information we're looking for.

Skidpad is one test, no it can't actually measure "handling" but is there even a metric for handling? It's a good example, though, since it's so tire dependent; no car can compensate for low-ish grip tires in this test. You're saying the same radius and same surface must be used; yet you want to test cars with different grip levels (tires). Strange.
What are the Edmunds numbers for the ZR1? 1.02g was all I found.

Being able to identify what is making a difference has everything to do with changing one single item (at a time).
Are you saying magazines should make e.g. suspension changes?

About your response to midenginebias: you just told us why it is so important to test all cars with "great tires" (i.e. to avoid comparing "inflated" results with "non-inflated" ones).