Is the Z4M......slow

[Mikewarlover]

i believe that with a good driver u can get under 13 with stock tires but it must be really hard on the car and the tires need to be in relatively good condition.

[HBspeed]

i've got volks and 275's now so i must be under 13!!

[GP20]

Originally Posted by HBspeed

i've got volks and 275's now so i must be under 13!!

Actually, 19" & 275 tires probably put you closer to 14's than 13's.

[HBspeed]

they are 18's!!!!

[Mikewarlover]

Originally Posted by GP20

Actually, 19" & 275 tires probably put you closer to 14's than 13's.

haha u must be kidding right. 19 Inch volk rims are at least 5 lb lighter than stock each wich reduce more than 20lb of unsprung weight and that will transfer into more than 100lb's of weight saving. By fitting wider tires means more traction and more power can be dealivered to the ground.

In one of the magazine's project car the guy did a back to back dyno of a stock car and then with light weight rims and larger tires and he got 13 more whp.


Here is the article http://www.europeancarweb.com/projec...ne_wheels.html

[Mikewarlover]

Originally Posted by HBspeed

they are 18's!!!!

18s would be even lighter so even more power

[HBspeed]

btw, I have pictures on hand to post over in the wheel/tires section if someone can tell me how...

[GP20]

Yeah what do I know. I've only owned 9 sets of aftermarket wheels on my Z4/Z4M now and have been chasing light-weight wheels for 5 years now and studied the physics behind unsprung weight and rotational mass.

Doesn't matter that the Volks are 5lbs lighter than the stockies. You're forgetting about rotational mass from the hub and the extra weight by going to 245/275 tires. I can brag that my 19" BBS RGR's weigh 20lbs also but realistically I'd be happy if they break even from 25lbs 18" wheels.

20lbs of unsprung weight does not equal 100lbs sprung weight. First of all there's not enough info for the calculation. Either way in reality 20lbs of unsprung weight is closer to 30lbs or if lucky, 40lbs of sprung weight. I thought this is highschool level physics?

And 245/275 tires = more patch area = more friction = worse gas mileage = not helping drag times on the Z4/Z4M. If you want to drag race the Z4M, run 255 rear tires and lower the tire pressure to 28lbs.

Originally Posted by Mikewarlover

haha u must be kidding right. 19 Inch volk rims are at least 5 lb lighter than stock each wich reduce more than 20lb of unsprung weight and that will transfer into more than 100lb's of weight saving. By fitting wider tires means more traction and more power can be dealivered to the ground.

In one of the magazine's project car the guy did a back to back dyno of a stock car and then with light weight rims and larger tires and he got 13 more whp.


Here is the article http://www.europeancarweb.com/projec...ne_wheels.html

[marcus1701]

Originally Posted by DiscoZ

It was C&D, it appears your search skills are as bad as your logic. FTR, I don't really read either R&T/C&D/MT/etc, glance over them from time to time. Either way, people have done high 12’s stock, anywhere from 107-109mph. And who cares? It’s fast enough. You can take most cars and make them insanely fast in the ¼ mile or a dyno queen; big deal. Telling you to do your homework before bashing is not elitist, its common sense.

Go try your "don't bash America" strawman somewhere else. Such a simplistic effort at deliberately confusing my argument is obvious to even the most obtuse (is perhaps why I get it). I've owned and driven many cars. When I bought the Z4M, I examined all other options, conducted extensive due-diligence and found only one that was in the money for me: the Z4M. That was my experience and I could have bought a number of other cars, I was never a "BMW" etc fan. Thus, I do not get your point about having money and liking cars, what exactly did you mean?

Either way, I am done wasting my time.

Link: http://www.caranddriver.com/reviews/...ster_road_test

Ok here we go.....I am trying to change the subject?? C&D was your example and you were proven WRONG by your OWN homework. You try to back yourself up with facts and now you are saying it doesn't matter about what those editors wrote.

By the sheer fact that you shoot an R32 down by saying it comes no where near an M is an elitist attitude. If you had read carefully the original argument was concerning 4wd traction DSG gearbox and mountain overtaking not drag racing! You gave a snickering attitude towards the car, and to that person who bought one, that was probably the best car they could afford, that's what I meant. Still don't get it?? Ask me again.

[DiscoZ]

Originally Posted by marcus1701

Ok here we go.....I am trying to change the subject?? C&D was your example and you were proven WRONG by your OWN homework. You try to back yourself up with facts and now you are saying it doesn't matter about what those editors wrote.

By the sheer fact that you shoot an R32 down by saying it comes no where near an M is an elitist attitude. If you had read carefully the original argument was concerning 4wd traction DSG gearbox and mountain overtaking not drag racing! You gave a snickering attitude towards the car, and to that person who bought one, that was probably the best car they could afford, that's what I meant. Still don't get it?? Ask me again.

Um, read the article again. Irony is you telling me I don't get it (which is also quite amusing, hence I am not upset). I am --honestly-- amazed by your sheer lack of comprehension; of any sort. Everything I wrote was in response to your mind-numbing posts. Btw - I've owned 2 Volkswagens (and my fiance owns one now), and this is my first BMW, brands don't matter to me, cars do. Like I said, read what you wrote and each and every one of my responses. While you are at it, read the C&D article. Yes. Read.

This is all I have to say to you, I shall be ignoring your posts from now on. Have fun in your little make-believe world (btw - is it really flat?).

[Mikewarlover]

Originally Posted by GP20

Yeah what do I know. I've only owned 9 sets of aftermarket wheels on my Z4/Z4M now and have been chasing light-weight wheels for 5 years now and studied the physics behind unsprung weight and rotational mass.

Doesn't matter that the Volks are 5lbs lighter than the stockies. You're forgetting about rotational mass from the hub and the extra weight by going to 245/275 tires. I can brag that my 19" BBS RGR's weigh 20lbs also but realistically I'd be happy if they break even from 25lbs 18" wheels.

20lbs of unsprung weight does not equal 100lbs sprung weight. First of all there's not enough info for the calculation. Either way in reality 20lbs of unsprung weight is closer to 30lbs or if lucky, 40lbs of sprung weight. I thought this is highschool level physics?

And 245/275 tires = more patch area = more friction = worse gas mileage = not helping drag times on the Z4/Z4M. If you want to drag race the Z4M, run 255 rear tires and lower the tire pressure to 28lbs.

I can careless about ur experience with chasing light weight wheels really. All i see are facts which in the dyno that the M with light weight rims and fatter tires put down 13 more whp. As far as i know the more power thats put to the ground the faster ur car will go. Fatter 275 tires will be able to put down more power off the line providing the car with a better launch which will likely to achieve a better quatar mile time. I really find it difficult to believe unless u can show me some fact that a car with significantly lighter rims and putting down more power will be slower in a straightline as a car with stock rim and tires.

[MVF4Rrider]

[GP20]

Fatter 275 tires will be able to put down more power off the line providing the car with a better launch which will likely to achieve a better quatar mile time.

We're not talking about Roman's +500HP Z4M. You can get a perfect launch in a stock Z4M without going to 275 tires. Wider tires have more contact patch area which means more energy is required to move them.

I really find it difficult to believe unless u can show me some fact that a car with significantly lighter rims and putting down more power will be slower in a straightline as a car with stock rim and tires.

Go back and read my post again. You're forgetting, once again, about rotational mass away from the wheel hubs - 18" v.s. 19". And I never said a car with significantly lighter rims is slower than a car with stock rims. I said there are other factors that need to be considered and you can't just assume that lighter 19" rims automatically mean quicker acceleration than with stock 18" rims.

[Mikewarlover]

Originally Posted by GP20

We're not talking about Roman's +500HP Z4M. You can get a perfect launch in a stock Z4M without going to 275 tires. Wider tires have more contact patch area which means more energy is required to move them.



Go back and read my post again. You're forgetting, once again, about rotational mass away from the wheel hubs - 18" v.s. 19". And I never said a car with significantly lighter rims is slower than a car with stock rims. I said there are other factors that need to be considered and you can't just assume that lighter 19" rims automatically mean quicker acceleration than with stock 18" rims.

I guess 255 will normally be enough to get it off the line on a good sunny dry day with proper summer tires in reasonably good condition. However plz explain to me that if a light weight 19inch is putting down more power on the dyno than stock 18s how can it not be faster. Or are u saying that if the back to back dyno i showed u is a 19in and one lb heavier it will automaticly lose all the 13whp. I won't believe that.

[GP20]

Originally Posted by Mikewarlover

I guess 255 will normally be enough to get it off the line on a good sunny dry day with proper summer tires in reasonably good condition. However plz explain to me that if a light weight 19inch is putting down more power on the dyno than stock 18s how can it not be faster. Or are u saying that if the back to back dyno i showed u is a 19in and one lb heavier it will automaticly lose all the 13whp. I won't believe that.

I didn't say any of those things. I said just because a 19" rim is lighter than a 18" doesn't mean it's putting down more WHP. It may or it may not. There are more things to be considered. Rim width/diameter. Tire weight/width/diameter. Unsprung weight is only one of the equations. A lighter wheel frees up more WHP, and at the same time you take a step back when you upsize the wheel (moving the rotational mass away from the center) and increase tire patch area and tire weight. You may be back to square one or you may still be ahead.

Anyway. I'm done arguing about it on the forum. Come out to the next Richmond/Vancouver meet and we can chat about it. I'll buy you a cup of coffee too.

[Mikewarlover]

Originally Posted by GP20

I didn't say any of those things. I said just because a 19" rim is lighter than a 18" doesn't mean it's putting down more WHP. It may or it may not. There are more things to be considered. Rim width/diameter. Tire weight/width/diameter. Unsprung weight is only one of the equations. A lighter wheel frees up more WHP, and at the same time you take a step back when you upsize the wheel (moving the rotational mass away from the center) and increase tire patch area and tire weight. You may be back to square one or you may still be ahead.

Anyway. I'm done arguing about it on the forum. Come out to the next Richmond/Vancouver meet and we can chat about it. I'll buy you a cup of coffee too.

It would really interesting to see a back to back dyno of a lightweight 19inch rim compared with stock rims. Anyways i see that u say USA for location but are u living in GVA. Would be nice to see u on the next meet if thats possible. We should organize one in fact haha.

[GP20]

Originally Posted by Mikewarlover

It would really interesting to see a back to back dyno of a lightweight 19inch rim compared with stock rims. Anyways i see that u say USA for location but are u living in GVA. Would be nice to see u on the next meet if thats possible. We should organize one in fact haha.

I grew up in Burnaby, moved to Seattle/Bellevue after college 4 years ago to work for Microsoft and now am back to doing/taking over family business. I decided to stay in Bellevue 'cos I liked here a lot, but still go back to Burnaby/Richmond once a month to visit family and for the food. Let me know whenever you're visiting Seattle as well.

[Mikewarlover]

Originally Posted by GP20

I grew up in Burnaby, moved to Seattle/Bellevue after college 4 years ago to work for Microsoft and now am back to doing/taking over family business. I decided to stay in Bellevue 'cos I liked here a lot, but still go back to Burnaby/Richmond once a month to visit family and for the food. Let me know whenever you're visiting Seattle as well.

sure i hope we can meet at our next meet. There are so little Z4 owners on e90 that are in Vancouver and nevermind M owners.

[karmasabish]

Originally Posted by Mikewarlover

I can careless about ur experience with chasing light weight wheels really. All i see are facts which in the dyno that the M with light weight rims and fatter tires put down 13 more whp. As far as i know the more power thats put to the ground the faster ur car will go. Fatter 275 tires will be able to put down more power off the line providing the car with a better launch which will likely to achieve a better quatar mile time. I really find it difficult to believe unless u can show me some fact that a car with significantly lighter rims and putting down more power will be slower in a straightline as a car with stock rim and tires.

omg. i just saw this thread.

to the guy who thinks a stock Z4m with slicks can run 11s, please put down the crack pipe, or pass it to me at least.

to the guys quoting magazines, please stop mag-racing, the only thing that counts are real timeslips. quoting a car magazine test is nice and all, but these are very good drivers on a track and test equipment. not to mention that that very same car and same driver on a different day will net a different time, due to weather and track conditions...

Regardless - RARELY will an average driver on the road be able to duplicate what the magazine hot shoes can do. Frankly, saying Car A will do a 13 second 1/4 mile, does not mean that YOU can make Car A do a 13 second 1/4mile.


now...13 WHP from lighter wheels? i'm inclined to believe that this is basically impossible; you are lightening rotational inertia, which will aid in accelaration, but i'm not quite sure you'll actually GAIN Horsepower. Its not the same thing as running lighter underdrive pulleys which WILL free up horsepower as you are lightening the rotational mass of the engine.

ALSO to the guys talking about the wheels and tires, and i'm just saying this to think about in your discussion. If you are going to a bigger wheel and end up with a larger overall diameter than stock (including tire and wheel) you will be changing the overall gearing of the car, making your final drive taller and slowing the car's acceleration throughout all gears. (pretty sure it make is taller, either way, you are changing the final drive which will affect acceleration)
This can negate your lighter wheels.

of course now you guys are going to get coffee or whatever, but thought i'd throw in my 2 cents.

[rc'Z]

+1 to the timing slips, something the members of this boad are real short on.

[mpower03]

Originally Posted by karmasabish

omg. i just saw this thread.

to the guy who thinks a stock Z4m with slicks can run 11s, please put down the crack pipe, or pass it to me at least.

to the guys quoting magazines, please stop mag-racing, the only thing that counts are real timeslips. quoting a car magazine test is nice and all, but these are very good drivers on a track and test equipment. not to mention that that very same car and same driver on a different day will net a different time, due to weather and track conditions...

Regardless - RARELY will an average driver on the road be able to duplicate what the magazine hot shoes can do. Frankly, saying Car A will do a 13 second 1/4 mile, does not mean that YOU can make Car A do a 13 second 1/4mile.


now...13 WHP from lighter wheels? i'm inclined to believe that this is basically impossible; you are lightening rotational inertia, which will aid in accelaration, but i'm not quite sure you'll actually GAIN Horsepower. Its not the same thing as running lighter underdrive pulleys which WILL free up horsepower as you are lightening the rotational mass of the engine.

ALSO to the guys talking about the wheels and tires, and i'm just saying this to think about in your discussion. If you are going to a bigger wheel and end up with a larger overall diameter than stock (including tire and wheel) you will be changing the overall gearing of the car, making your final drive taller and slowing the car's acceleration throughout all gears. (pretty sure it make is taller, either way, you are changing the final drive which will affect acceleration)
This can negate your lighter wheels.

of course now you guys are going to get coffee or whatever, but thought i'd throw in my 2 cents.

First of all, i have seen the time slip of a stock car at 12.7. I said with slicks you would lose about a half a second ~12.2. I didn't say or if did i didn't mean to say the car could do 11's, what i meant was, with slicks, and weight reduction of about 250 pounds the car might do high 11's. WIth that being said the car can do high 12's stock, and no doubt low to mid 12's with slicks. Slicks will make the car hook up and go, resulting in a faster 60 foot time and ultimately a faster 1/4 mile et.