According to the Maxima commercials and the booklet, a stock maxima can brake from 60 within 3 seconds. I find this hard to believe, cause when i break from 50 it takes like 4 0r 5 seconds.(unless their measurements are really slow).

 

but i let my friend drove for a few blocks, and he said my max has better brake than hi audi A4...
don't wanna try that, cuz didn't want 4 raped rotor !^^

 

depending on how much you brake. i was on the highway once and i had to brake really quick (to avoid an accident), it stopped really fast (dont know how fast though) and it stopped really smoothly to. that was the only time i ever experienced the stopping power of the max, but i dont recommend you go out and try it yourself.

 

well the math works out to (assuming constant decelleration)
t=2*d/v

v=60mph = 88ft/s
d=I think it's about 130 feet

t=2.96 seconds.

Anyway this results in decelleration of about 30ft/sec^2 which is pretty close to 1G (32ft/sec^2). Modern ABS systems all seem to stop at this rate. It's mostly a function of the tires.

I would think that full speed stops from 60mph would be fine for your rotors. Of course I could be wrong. All my rotors are warped Need to get an M3... 13 inch rotors

 

You have to take mass into consideration.

 

No, you don't - Galileo proved that a few hundred years ago!

Dave

 

Potential deceleration rate given a known braking force would require mass as a factor - deceleration rate from a known speed and distance does not include mass.

 

I think when they are new 3 secs is no problem. The problem is after alot of heavy braking they warp rotors. I have over .050 of runout in my front rotor and .040 in the rears. I guess it is time to bring in to the dealer for some warranty. LOL!!! The front rotors are blue from the heat!!

 

Will the dealer fix rotors under warranty? I would think they would call it normal wear or something.

Anyway you do not have to take into account mass in the calculation because braking force is not one of the variables. Stopping distance takes into account braking force.

In conclusion. Any car with a 60-0 braking distance of 130 feet will stop from that speed in less than 3 seconds.

 

Uh oh... there's some confusion about mass...

Quick answer :: No, of course it doesn't matter... but i don't think anyone got the reason 100% right yet.. (keep reading if you are interested)

Detailed answer :: Remember way back to physics class... Lemme remind you of a few basics...

F=ma (think newton)
u=ff/n (coefficient of friction = force of friction/normal)

Basic concept review -> something in motion will STAY in motion... UNTIL SOMETHING STOPS IT.. think of an air hockey table... If there was no friction/air resistance, your car would keep going once you let go of the accelerator!!!! at the same speed!!! forever!!! (this is one of those concepts that isn't very intuitive from daily observations, and usually tends to bother people without ANY background in classical physics...)

Now, since we are only restricting ourselves to first year physics, let's just take it on good faith that the only things which could affect an objects movement are things that touch it AND gravity....

Touching?? Last time I checked, only my tires touched the road... so the only friction we care about in this argument, is the friction between those tires and the road... (AND YES, there is friction caused by the atmosphere... in FACT, a LOT of it... but it is just so darned complicated.. we're going to pretend it doesn't exist for now!!!)

Gravity?? well that depends, we are talking about EARTH... right?? so gravity matters... (which makes sense, because if there were no gravity, there would be no frictional force in the first place... think about it, or just trust me!!!)

SO-->

by solving both of those equations above, and assuming that only the tires cause de-acceleration, we get... (think back to algebra)

(u)(m)(g) = (m) (a)

Cross out the m's because you can... and there you go...
MASS IS LIKE THE US-MEXICAN BORDER... IT DOESN'T MATTER!!!

(u)(g) = a;


Proof.... open up your drivers ed manual, and check the stopping distance... notice that mass of the car is NOT a factor!!!


***IF AND ONLY IF YOU FOLLOWED ABOVE, KEEP READING***

We can perform some REALLY rough estimates using just what we learned above!!!! (you see, friction is a very complicated thing, and remember, we just conveniently forgot about drag from the atmosphere!!!)
I mean REALLY ROUGH!!!


We are concerned with static friction... why... because we all have abs :-)

I did some quick searches on the net and came up with an average value of around .85 for the static coefficient of friction on dry asphalt...

that gives us an acceleration of roughly -8.33 m/s

at 60mph your car is moving at roughly 27 m/s

so it should take about 3.2 seconds to come to a complete stop.... (however, keep in mind, we left out air-resistance, and performed VERY rough estimates... so less than 3 seconds is DEFINITELY POSSIBLE!!)

One more calculation :
vf^2 = vi^2 + 2as

gives us a stopping distance of about 44 meters... (consistent with the other responses!!!)


-Tom


PS.. If i screwed up somewhere, lemme know... i didn't bother checking the calculations, or proofreading... :-)

 

tomz17: Nice job....It may seem a bit counterintuitive that mass does not matter in such a calculation. But, a little dynamics and arithmetic show that it cancels out. Lucky for us....in many cases the mass of an object in such a problem is not given

 

ya... lucky for us that it DOES cancel... think about what life would be like if it didn't!!!! (heh, even more SUV's would be crashing into stuff :-)

and forget about semi's!!!!!

-Tom

 

Whoa. Answered the question for all.

 

Nissan does not take reaction time into consideration. I remember an add for a 1995 BMW M3 that did 60-0 in 2.8seconds without adding on driver reaction time. I don't find it hard to believe that the Maxima can brake 60-0 in ruffly 3 seconds.

 

OK, since mass doesn't matter then... stay with me now... if you put the Maxima's brakes on an SUV, would they both stop at the same time and within the same distance?

 

No No No... your missing the point here...

if you disassemble a metro, and stick the brakes on a semi... (all technical considerations aside).. will it stop the semi from 60 mph... OF COURSE NOT... SILLY!!!! Those brakes are NOT able to exert the necessary force (torque) on the wheels... They would warp faster than the enterprise!!! We were talking about the rubber on asphalt (which is a much more meaningful discussion in the context of our discussion)...

Why?? well, the calculations in my previous post rougly reveal the MINIMUM stopping distance/time... (ie.. the theoretical FASTEST THAT YOU CAN STOP without violating the laws of the universe...) (neglecting of course various other factors I outlined)...

Since we were talking about static friction (wheels spinning), once you want to brake faster than that, you should theoretically induce a skid... (and then evil stuff happens with the chemistry of your tires/the road, and we must talk about kinetic friction)... Let's not go there... Just take it on faith that experimental evidence shows us that under **MOST** circumstances you can stop faster if you DON'T SKID... (one of the chief reasons for abs!!!)

Moral of the story --> Nissan engineers are incidously clever people, and know about all of this stuff... therefore they (hopefully), matched the right sized brakes to our car, which are able to do their job efficiently. So in answer to your question "why would maxima brakes on an SUV be a bad idea??" Cuz while mass doesn't matter, we STILL have to obey the laws of thermodynamics!!!

-Tom

 

Hehehe... so we still don't know if the Max can stop within 3 seconds.

 

Well.. quick answer --> no we don't :-)

However, we've shown that it certainly is possible to stop from 60 mph in less than 3 seconds... AND unless the Nissan engineers did a REAL ****ty job on the brakes, I would venture a guess that the car **should** stop within 3 seconds (on new brakes, of course)...

More important, however, are the tires... The Potenza 17's are a tad on the softer side, and it certainly felt like < 3 seconds when I did it ;-) (I almost got into 2 accidents where i had to brake with the max REALLY HARD, and I swear that the abs, along with the grabby tires on dry surface are what saved me..)

-Tom

PS... NO WARPED ROTORS... YET!!!!

 

Option 1: Do some 60-0 runs and wash your wheels by spraying water on them.

Option 2: Let Nissan rotate your tires a few times. Hehehehe...

 

Water warps the rotors???

 

Hot rotors + cool water = whacked rotors

 

Heh... a few 60-0 runs on a hot day, and then some iced water...

Warps faster than the starship enterprise.. (i just like saying that..... it reminds me of how clever I am)


-Tom

PS... you said something about Nissan tire rotations... I was considering having my tires rotate by my dealer next oil change (about 10,000 miles)... what do you guys think... is this a good idea?

 

No, but then that's a different set of equations. The distance would change and so would the time. Then again - it might not matter much because tire traction is the main limitation in braking distance, not the brakes. After the first few stops in a row the brakes start to count more or the smoke does).

DAve

 

No, but then that's a different set of equations. The distance would change and so would the time. Then again - it might not matter much because tire traction is the main limitation in braking distance, not the brakes. After the first few stops in a row the brakes start to count more (or the smoke does).

Dave

 

If the dealer rotates your tires, make sure they put the lugs back in spec. Since they have a air tools, they get lazy and gun your lugs back on.

 

I included any kind of braking (whether it included tires, rotors, pads, calipers, etc.) within my reasoning, so it seems like we weren't on the same page from the very start. Oops!

 

With all this hard stop talking, all I can say is NO WONDER YOU GUYS HAVE WARPED ROTORS

 

Did we ask you? No!!! j/k

\

 

The original question was if the Maxima could do 60 - 0 in 3 seconds. The distance for 60 - 0 is pretty well tested - R&T has it as 133ft. If you know the start speed, the stop speed (ie - 60 and 0) and the distance, the time is easy to calculate and doesn't use weight as a factor. t = d/((s1-s2)/2). The answer for 133 ft is 3.00000 sec., I imagine that's how the advertising dept. came up with that number.

As long as the brakes can exert sufficient force to lock the tires the distance is mostly determined by the tires. Bigger brakes let you do it more often as do better pads.

Dave