[JST]

One of my biggest hangups with the new M models is BMW's bizarre decision to favor increased muffler size (and four cool looking exhaust tips) over fitting even a space saver spare tire. I post on this every now and then, but the linked thread got my attention and so I thought I'd do so again.

Can you imagine being on your way to a client site, having a flat, and having to wait by your car while it's flatbedded to a dealership? Or being on a freeway late at night, just wanting to get home, and having to call Roadside Assistance because you hit a nail? I've used the spare tire on several of my cars in just these situations; it simply blows my mind that BMW doesn't see the need to give a real spare tire.

IMHO, if they absolutely have to have the fancy chrome exhaust system, they should at least provide the option of run-flat tires. I realize that they decrease performance somewhat, but the notion of standing next to a brand new 50K+ car on the side of the road waiting for a tow truck because the tire is flat is just ridiculous.

http://forums.roadfly.org/bmw/forums/e46m3/forum.php?postid=393419&page=1

 

[nate]

The Z8 has run-flats :dunno:

Dunlop and Bridgestone make max performance run-flats, it could be an option...

 

[Pinecone]

Then just use the M Mobility kit.

You have a choice, call and wait, or use the kit.

Also the reason for the larger muffler is better performance. Less back pressure.

Another thing, all the current Ms use different wheels front and back with different offsets. Also Limited Slip Differentials don't like different diameters on the same axle.

Lots of reasons why a spare tire would be difficult.

 

[JST]

Then just use the M Mobility kit.

You have a choice, call and wait, or use the kit.

Also the reason for the larger muffler is better performance. Less back pressure.

Another thing, all the current Ms use different wheels front and back with different offsets. Also Limited Slip Differentials don't like different diameters on the same axle.

Lots of reasons why a spare tire would be difficult.

The M "Mobility" kit is a bad joke; a can of "Fix a flat" would be just as effective. For many situations (bubble in the tire, total blowout, bent rim) the M Mobility kit is completely useless, and for those where it can be used, it causes as many problems as it solves (you need to get the goop off the wheel, etc).

There are a lot of tradeoffs that could be made in the name of better performance. Why have windows that roll down? Even in M models, there needs to be some appreciation of the fact that this is a street car, not a race car. Besides, I suspect that "low backpressure" could be acheived without the giant muffler on the Ms; free-flow exhausts are commonplace, and typically take up *less* space than more restrictive exhausts, not more. Moreover, if I'm not mistaken, all of the Ms use a true dual that Ys into four tips; even if a true quad exhaust were somehow superior to a true dual, the Ms don't have one. The four exhaust pipe thing is ///Marketing at its finest, and is an example of function following form.

 

[JPinTO]

As long as it has run-flats, it shouldn't be a huge factor.

If you are really worried about it (assuming one has an E46M3) then you could buy a spare wheel and tire combo and keep them at home for just such an occasion.

In the 500,000miles I've driven in my lifetime, I've never required the spare at all. In fact for about 5 years, I ran without the spare at all in my 91 Eagle Talon. There was no space for the stereo system and the spare, so bye-bye spare! Never even needed the can of fix-it-goo.

Of course, your opinion and results may vary! Then again, I'm the guy who has run my E46 with summer tires through 3 winters in a row.

- JP

 

[.Gravedgr.]

In the 500,000miles I've driven in my lifetime, I've never required the spare at all. In fact for about 5 years, I ran without the spare at all in my 91 Eagle Talon. There was no space for the stereo system and the spare, so bye-bye spare! Never even needed the can of fix-it-goo.

In the 103,000 mile lifetime of my Mazda MX-3 (4.5 years), I picked up somewhere between 1/2 and 1 dozen nails, had 4 replaced tires, and 1 replaced rim (quarter-sized hole).

 

[JST]

In the 103,000 mile lifetime of my Mazda MX-3 (4.5 years), I picked up somewhere between 1/2 and 1 dozen nails, had 4 replaced tires, and 1 replaced rim (quarter-sized hole).

On no less than four ocassions in the past five years I've been in situations where, had I not had a spare tire, I would have been riding my thumb. Nearly once a year is too often to go without such a vital piece of equipment. Obviously, YMMV; for someone who's never had a flat, it's clearly not as big a concern.

 

[Pinecone]

You probably haven't ever used Fix A Flat.

Let's see in 30 + years I have needed a spare twice. And in only one case would not having had the spare been a problem. And in that case the Mobility kit would have been fine.

WRT the exhaast system, it isn't the four tips that make it so large, it is the full dual exhaust system (MZ3s have no room for sapre due to second muffler). Also the manufacturer has to build to a different standard than the aftermarket. Noise, durability, etc. Look at the Eisenmann for the M3, no lighter, no smaller than stock, but meets German standards.

As for the tire being toast with using the Mobility kit, I don't use plugged/patched tires on high performance vehicles. On our Jeep, maybe, on one of the BMWs, never. It isn't worth the potential problems for the few hundred dollars saved.

And you didn't address the problems of the different rim offsets front and rear or the problem of a smaller spare and LSD.

Some of the MZ3 Coupe guys have found a Porsche shrunken spare (you have to inflate first) that fits with a spacer. No idea how the LSD likes it. For an M3 you could do the same.

Personally I have no trouble with no spare.

 

[JST]

AFAIK, limited slip differentials only have problems with differing outside diameters, so as long as the tire was the same outside diameter, you'd be fine (the Porsche inflate-a-spare is one way to accomplish this). Moreover, I had a space saver spare on my Mustang that was not the same outside diameter as the road wheel, and the Mustang's LSD had no problem with it, at least for the short time that a space saver is designed to be used for. I think the LSD argument is a red herring.

The offset argument is a bit more compelling, but again, we're not talking about a spare that has to be capable of handling the Nurburgring. It only has to be capable of getting you out of a tight spot. As long as the tire physically fit and didn't catastrophically affect the handling to the point where the car was undriveable, a compromise in offset would be fine. WRT to the M3, I bet a Type 44 8 inch wheel would work just fine for both front and back (for temporary use); the M68 8.5 inch wheel works on the back (and is used in Europe for snow tires). The M5 uses the same wheels, IIRC, as the 540, so the 540s spare should bolt right up.

The Z3 may honestly not have room for a dual exhaust and a spare, although I tend to think that a pair of three inch pipes running next to each other in a true-dual arrangement would a) run in the same or similar physical space as the Z3 3.0 arrangement, and b) could be tuned to have nearly zero backpressure. But even if it can't, how to explain the M5 and the M3? Both of these platforms have plenty of space for a phalanx of straight pipes in addition to the spare tire well.

You probably haven't ever used Fix A Flat.

Let's see in 30 + years I have needed a spare twice. And in only one case would not having had the spare been a problem. And in that case the Mobility kit would have been fine.

WRT the exhaast system, it isn't the four tips that make it so large, it is the full dual exhaust system (MZ3s have no room for sapre due to second muffler). Also the manufacturer has to build to a different standard than the aftermarket. Noise, durability, etc. Look at the Eisenmann for the M3, no lighter, no smaller than stock, but meets German standards.

As for the tire being toast with using the Mobility kit, I don't use plugged/patched tires on high performance vehicles. On our Jeep, maybe, on one of the BMWs, never. It isn't worth the potential problems for the few hundred dollars saved.

And you didn't address the problems of the different rim offsets front and rear or the problem of a smaller spare and LSD.

Some of the MZ3 Coupe guys have found a Porsche shrunken spare (you have to inflate first) that fits with a spacer. No idea how the LSD likes it. For an M3 you could do the same.

Personally I have no trouble with no spare.

 

[Pinecone]

Yes, it would have to be the same outside diameter. And limited slips do have trouble with differing tire diameters. And it may be more of a problem for the M3 diff, as it isn't a "normal" LSD. And it doesn't take a lot to cause trouble. Look at the recalibration required for different tire diameters for the tire pressure monitor.

Just thought of something, how about the DSC? It might very well "think" that a slight difference in tire diameter is a tire without traction. Of course you can trurn DSC off, but can you be sure that EVERYONE will remember to do that? Heck, take a look over on Roadfly, many people can't figure out what oil to put in M3s with the big yellow decal.

With the MZ3 is isn't the pipes, but the mufflers. And there is no room furhter forward for mufflers. Even with the Supersprint system, there would be no room for the spare. Heck there isn't even room for two 3 inch pipes. The stock system has flat areas to fit it under the car.

Personally for me, I would rather have more trunk space, less weight and a cell phone. Works better for me.

I forgot to say in the last post that I have had MANY more problems that required towing that had nothing to do with tires. It is no big deal.