18's or 19's......which works best on the M5 - Page 4

Hamann7 · 31st January 2004, 21:02

Quote:

Originally Posted by johann

Do you realize that we're talking about unsprung weight here?

I'd say a well designed light wheel rim could make up to 0.5-1 s off the time to 0-200 km/h, everything else being equal.

Cheers,
/Johan

Yes, I do realize this. My GT2, for instance, has the PCCB brakes which save a lot of unsprung weight.

But my point is that it is all relative. The M5 is a pig, so going to lightweight wheels may do a little, but it ain't gonna do a whole lot on such a heavy platform.

And certainly not shave 0.5-1.0s off the 0-200km time. If you can find wheels that will shave even 0.5s off my GT2 0-200km time, let me know where I can get them!

johann · 31st January 2004, 23:03

Hamann7,

It's obvoius that you don't understand what unsprung weight does for handling and why lighter rims can improve acceleration. Saving 5 kg unsprung weight per corner will affect a heavy M5 as much as an GT2 (which BTW is not really light weight either) becuase it is just unsprung weight and not affected by the total weight of the car. It's obvoius to anyone who have driven a car after reducing the unsprung weight that the car both handles better and has better comfort.

Depending on what rim you have now on your GT2, it should be pretty easy to find a rim that also gives better acceleration. Hint. they are lighter and possibly smaller.

Cheers,
/Johan

MIB · 1st February 2004, 00:17

Quote:

Originally Posted by johann

Hamann7,

Depending on what rim you have now on your GT2, it should be pretty easy to find a rim that also gives better acceleration. Hint. they are lighter and possibly smaller.

Cheers,
/Johan

Hey Johann,

Your an *****.

Your Correct, but your still an *****.

And I mean that in the nicest possible way.

Tysons cars are SO KickA$$ compared to a stock vehicle, that he modestly doesn't feel they can get any larger benefit than what he has already done.

His DFC equipped beast is so far ahead on handling compared to a stock Beast, that it is difficult for him to imagine it, noticeably better again.

I, on the other hand am convinced. I want it all. 360's Beware on the Track.

johann · 1st February 2004, 01:05

MIB,

Do you know that I had DFC as well as ligh weight BBS rims on my M5 already in 2001?

Cheers,
/Johan

Hamann7 · 1st February 2004, 01:09

Quote:

Originally Posted by johann

Hamann7,

It's obvoius that you don't understand what unsprung weight does for handling and why lighter rims can improve acceleration. Saving 5 kg unsprung weight per corner will affect a heavy M5 as much as an GT2 (which BTW is not really light weight either) becuase it is just unsprung weight and not affected by the total weight of the car. It's obvoius to anyone who have driven a car after reducing the unsprung weight that the car both handles better and has better comfort.

Depending on what rim you have now on your GT2, it should be pretty easy to find a rim that also gives better acceleration. Hint. they are lighter and possibly smaller.

Cheers,
/Johan

Johan,

Obviously we don't understand each other. I understand all the so-called technical concepts you are talking about. However, the personal attack is totally uncalled for, as I have maintained a very respectful tone towards you.

Ask anyone on this board who knows me. I have a pretty good grasp of driving dynamics, physics, and performance tuning.

Obviously, it is you who doesn't quite understand. Maybe if you owned a car of the GT2's caliber or a 730bhp 996 Turbo you would understand why modifying the M5 or even an M3 is the law of diminishing returns.

Then again, I suppose I should cut you some slack, obviously you live in the land of Volvos.

Good luck racing your M3, I'll cheer for you as the Porsches annhilate you.

johann · 1st February 2004, 02:11

Quote:

Originally Posted by Hamann7

Obviously, it is you who doesn't quite understand. Maybe if you owned a car of the GT2's caliber or a 730bhp 996 Turbo you would understand why modifying the M5 or even an M3 is the law of diminishing returns.

That makes sense, the more power you have in your car the more you know about physics. Good news for kids, they don't have to go to school or university to learn physics, all they need to do is get their car tuned or buy a more powerful car. The more they tune, the more physics they get to know automagically. You must be enormously intelligent to come up with that. But off course with a whooping 730 hp I guess it's no suprise. I will tell the Nobel price commit, I'm convinced that they will be as thrilled as I am.

BTW, easy come, easy go.

Also the GT3s race in another class.

MIB · 1st February 2004, 03:03

Quote:

Originally Posted by johann

MIB,

Do you know that I had DFC as well as ligh weight BBS rims on my M5 already in 2001?

Cheers,
/Johan

Yes I Knew. Thats why I called you an *****. Because I knew that you knew.

I guess Tysons point is, that adding 200+ HP to your vehicle makes a lot bigger difference than putting on lighter wheels.

But then again he goes an adds 300 to 350+ Hp and feels an even bigger gain. So yes, almost doubling the power of your car is far greater Noticeable then shaving a few pounds off unsprung weight.

So to get full benefit, lets do BOTH.

I'd love to be able to double the power of the Beast, but it is highly unlikely. 500 at the flywheel N/A will do me. When I want more than that, I'll get the P car.

Hamann7 · 1st February 2004, 06:29

Johan,

If you actually comprehend proper English, you would see that the points about knowing physics and vehicle dynamics was presented seperately from the GT2/Turbo comment.

Before you attack me, try to understand my statements first, or else you end up performing a logical fallacy, which you are so prone to do-- it's called a 'Straw Man' argument. Perhaps in Sweden they don't teach you this concept.

Or maybe it's just a foreign relation thing, or lack thereof. You Swedes are too funny!

MIB obviously gets my point.

Oh, and by the way, in addition to DFC and ACS swaybars, I have forged lightweight racing wheels from Work Japan. They are much lighter than stock. I have reduced unsprung weight, and so I have a basis for comparison.

Incidentally, the University I attended actually holds claim to the most Nobel Prize winners... perhaps you can nominate me for one

johann · 1st February 2004, 15:30

Hamann7,

My understanding of proper English is very good and normally I have no problem understanding and follow people’s argument. In this thread not only me, but also most others fail to understand you. Is there something wrong with all our English understanding or is it your reasoning that is unclear and illogical?

Your personal attacks on me and attacks on Sweden and Swedes are and very ignorant, not to mention how rude your message that it's meaningless to modify a heavy car such as an M5 or even an M3 and how poor these cars are compared to "a real sports car".

If your point was that adding 310 hp to a car does more for acceleration than reducing the un-sprung weight why didn't you say so from the beginning. Although it's completely irrelevant to the discussion of un-sprung weight on an M5, let alone if 19" or 18" are better on an M5. The discussion was not if a car will accelerate faster by adding 310 hp instead of reducing un-sprung weight with 20 kg.

BTW, since you went to university you should know how to perform a test with a scientifically approach.

Did you do this to come to you conclusion regarding the effect of un-sprung weight in your car? Also you said they were 19" and lighter than the stock wheels but did actually even measured the weight and did you also consider that going to 19" could have had so much negative effect that it eliminated the positive effects of lower un-sprung weight?

Since you seem so hung-up with straight-line performance, let me give you an example; a M5 with 460 hp 20" Hartge rims and will not be any faster than a bone stock M5. A 425 hp M5 with BBS RC will be clearly faster than both, the same M5 was just barely faster with stock wheels. With BBS RC the 425 hp M5 accelerated 100-200 km/h in 10 s with two people and a heavy sub woofer and amp in the trunk. Alone in the car I could get under 10 s.

Best figure I've seen in a magazine for a stock M5 ever is 11.9 and that car had no passengers and certainly no heavy sub woofer installation on the other hand the 425 hp had a lighter exhaust. So maybe the weight of the stock M5 was about 75 kg less.

If you have the pretty good grasp of driving dynamics, physics, and performance tuning, like you say you do, I suggest you put the money where your mouth is and do the math. If you know how to do that, you can only come to the same conclusion as I and others have, a rim can also affect acceleration significantly.

The fact that BMW made most of the un-sprung parts in aluminium where many of the same parts on an 540i are of steel proofs how important un-sprung weight is for handling. The sole reason why they didn't went further is pure economics, wheter it for owners it's one of the changes with best price/performance and certainly is worth looking into. I use performance here in a wider sense, meaning both straight line performance and cornering

If you bother to read the article Chuckc linked to, http://www.garagetuners.com/showthread.php?s=&threadid=3943, it will be obvious to you too. This quote says it all:

Quote:

A reduction in the weight of the rim/tire assembly of 5lbs x 4 (all around the car) is equivalent to a 200lb weight reduction in vehicle weight (thats worth 0.200 in the 1/4 mile)

tfunk10258 · 1st February 2004, 18:17

Quote:

Originally Posted by Hamann7

Johan,

You and I will disagree on this point, but on an M5, I don't think it makes much difference because if you calculate the weight savings vs. total weight, it is truly negligible.

It's one thing to put lightweight parts on a light sports car. But on a 4000 lb. sedan?

As for acceleration figures, how much difference do you think it would make?

I'd rather have a slightly heavier, stronger wheel that will withstand the abuse of bad roads and potholes.

My point is that most of these so-called mods are psychological. If it makes one feel better about their car, great. But it would be hard to believe that simply switching wheels will shave even one second off your lap time on a typical track. Then again, the M5 is not such a good track car either, but that's a whole other topic.

A larger wheel does affect acceleration figures significantly. As does a heavier wheel. For every inch in diameter larger the wheel is, you lose 8 horsepower going to the ground. You also loose power when your wheels are lighter, because its a rotating mass, and requires more torque.