Comparing car lap times: Equal tires?

[rice_classic]

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.

[SubieNate]

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

[avg]

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.

[brewksy]

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.

[Turbowned]

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.

[Kunzite]

Admin, fatoni's vote was counted thrice!

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.

[blur]

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...

[fatoni]

Originally Posted by Kunzite

Admin, fatoni's vote was counted thrice!

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.

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.

[TheRipler]

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.

[brewksy]

Originally Posted by fatoni

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.

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.

[fatoni]

Originally Posted by brewksy

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.

[Kunzite]

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.

[DarkSunrise]

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.

[scorcherjf]

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.