...and the difference in tire weight is quite sobering. The run flats are heavier, in some cases, a lot heavier. My 17" set-up is nearly 20lbs per wheel lighter than the stock 16" set-up. That's huge! 80lbs of spinning wieght.

 

Sobering? Lets put this into perspective. Bridgestone 050 in STOCK 17" size are 22 pounds.
Same tire, in RF is 23 pounds. Hardley sobering.

Perhaps your talking about buying different wheel in a different wheel size?

 

Allow me to pose this question...

Some time ago, in my older car (1995 Mustang GT), I did some informal autocrossing. Nothing too serious, really just competing against my own times, for the fun of it.

One of the things I read when I was learning about this was that in autocrossing, with its quick direction changes, 180s, etc... that a stiff sidewall was a large benefit - the less flex, the better. One of the suggestions made was that you can overinflate your tires (although still well within "maximum" specs), to increase the pressure and therefore reduce sidewall flex. Obviously they suggested deflating the tires back to "normal" pressure after the autocrossing event.

However, it has always been the case for a long time that drag racers want a soft tire and/or sidewall, that increases contact patch size with the road. The "big" drag racing tires have a very small wheel with a very TALL sidewall, and lots of twisting rubber!

So may I suggest (note: I am NOT claiming to be an expert here) that a stiff sidewall is better for tight HANDLING purposes (think slalom), and a soft sidewall is better for acceleration (and presumably braking) purposes.

IF that is true (AGAIN, I'm only guessing here), then surely there is a handling benefit to having a stiffer sidewall on the runflats? Quite possibly at the sacrifice of acceleration and braking benefits.

Of course, this is just a basic performance question, it does not take into account ride quality, tire wear, actual unsprung weight, etc.

 

I think your right on the money. There is a reason real dragsters run low tire pressure with huge sidewalls.

 

If I am right on the money... then it would stand to be that IF handling is more important to you than having a softer ride, or better acceleration, that you should accept the stiff sidewall with open arms... are you also agreeing with that theory?

Bottom line, I bought the MINI for it's handling... and I love the tight feeling of the runflats. I don't give a CRAP about the harsher ride... I didn't buy a Cadillac... besides, my Mustang has an even harsher ride anyway, so this feels soft to me.

 

Just to address these two points raised, I think what is missing in comparing the tires the variety of choices one has in non-runflats. Some are lighter, some have stiffer sidewalls, different treads, different compounds, etc. All of these options, including size, have an effect on the final outcome in weight, handling and ride quality - which is exactly why you can get the optimum choice for what you want in aftermarket tires vs the stock runflats, and why performance and/or driveability can and often is be better going that way.

 

But ... you dont have to buy the OEM tires again. Second generation RF, like the 050s, are starting to be sold and the choices will continue to increase as it appears more and more car makers will be moving to no spare tires

Edge, dunno, sounds good in theory but I'd like to hear from someone like MINIHUNE who seems to be the resident tire/autox expert.

 

Okay - I guess I don't see how it has to do with the guy's original post really, street driving, and what owners have to work with currently (as the stock RFs are the ones at the center of the issue).

edit: Sure, if and when the better aftermarket runflats are available, not horribly expensive or overly heavy, and have as good grip and drivability for real world mixed driving then I will certainly consider them.

 

I think that the OEM might get a bad rap for now. But see http://www.tirerack.com/tires/survey...ay.jsp?type=MP
Looks like the 050 rate HIGHER than F1s in two categories. Over time, they will just get better and better. That is the only point I got.

 

What setup do you have?

Hmmm. I weighed my 16"X-lite/Dunlop combo at 42lbs.

Perusing the 17" tire weights provided by Alex shows the lightest at 19+lbs.

Even if you were 18lbs lighter, that would be a total of 24lbs.
Do you really have 5lb 17" rims??

Per the weights given, an Slite/Goodyear combo would be 55lbs(!), so I can see getting 20lbs off of that...

 

But in digging deeper, there's no way to see what vote was on a run-flat or non-run-flat. I went to Bridgestones site (http://www.bridgestone.com.au/tyres/...eads/re050.asp) and there you can't tell by the tire name if its directional or not, or a run-flat or not. So the numbers in the reviews have to be viewed as being collected differently than tire brands and models that don't mix run-flat and non run flat technology.

Matt

And Eric, what you say is true, but it's also hard to compare stiffer sidewall with less traction in the contact patch vs a stickier tire with a softer sidewall.

 

Absolutely, good point... but I find that the "RF-haters" are so quick to dismiss RFs, paying no attention whatsoever to the fact that a stiff sidewall has benefits too (beyond the actual "runflat" use itself).

 

I know ... that is frustrating but now go here
http://www.tirerack.com/tires/tires....e1=yes&place=2

"a Run Flat version is used on the BMW Z4 sports cars and 5-Series sedans"

That doesnt mean much cause we still dont know whats being rated but now go here
http://www.tirerack.com/survey/Surve...045WR7RE050AXL
and there are references to RFs from the BMW crowd so they MUST have been part of the rating since there are so few miles, 300000 or so, (new tires) being rated.

This tire is a far superior tire to the concrete shoe runflats the Mini comes with from the factory

bloody great rfts. anyone who has had issues with rfts should try this before judging the state of rfts

The Run Flats are the best...still driving on a flat ( with a 1" gash in the sidewall) in the city while waiting for Bridgestone to deliver a new tire. Best tires I have ever owned.

I have not found a better performing tire [Z4 means RF]

These are great tires. They were the OEM tires with my car with the run flat option. [mercedes]

I think the tire is so new, its is a second generation, that people dont even know it exists as an option

 

I wanted to chime in. I'll be labelled as a RF hater, but really I'm just a "RF's aren't yet ready for prime time" guy. Many of you are correct that lots of the information now available about RF's is anecdotal as opposed to data researched. Corvettes have been running them at least since the C5, Goodyear makes some special ones for them and they generally get decent comments. The E46 M3 however, which does not have a spare, has always used conventional performance tires, as have a score of other sportier cars without spares. Handling is much more than just having stiff sidewalls, the ride/handling compromise is what BMW is famous for, and the MINI carries some of that heritage in its chassis. As far as weights go, the S-lites with Dunlop RF's that came off my car were 48 lbs each, I replaced them with Flik Wasps and Toyo T1R's (both 17's) that weighed 41 lbs. Probably could have picked lighter wheels, but 7 lbs on each corner of unsprung weight is significant. I didn't leave the RF's on long enough (42 miles) to get much of a feel for them, but I really like the feel/grip/ride of the T1R's and they didn't even rate very high in C & D's last shootout. I've been driving the M3 without a spare for almost 3 years so I'm used to the idea of just carrying Fix-a-Flat and a compressor. If I had an emergency on the road, I might not be able to find a 215/45/17 in a hurry, but could probably find something that would be close enough to get me home. And if all your MINI drives have been on RF's, you owe it to yourself to try someone's with conventional tires to feel the difference.

 

Well thanks for the slamming guys...gals?

I was thinking 20lbs per axle and some how multiplied this by four. In reality, the difference is 13lbs per wheel, a significant, if not sobering difference for a 2,563lb car.

26lbs for the stock 17 wheels + 23lbs for the run flats vs 20 lbs for the Michelins and 16lbs for the BBS RGRs. 49lbs vs 36lbs. 52lbs of spinning weight...I call that a lot.

Tire compliance figures into suspension tuning at some point, or it ought to. A stiff spring and damper combo will typically work well with a tire that has a stiff sidewall - the compliance rates of these three components must match up within some window.

 

Thanks for the clarification, meb. 13lbs is a considerable reduction, I just couldn't get to the ~20lb number. 36lbs is a very reasonable weight. Must feel nice!

For the record, I didn't say anything about sidewall stiffness, I think that was Edge.

 

Just for the fun of it, I took off one wheel/tire assembly and weighed it last night. Total weight was 43 pounds.

I have the 17" factory wheels and Goodyear run flats.

Maybe I could find someone in the area that has an S with regular tires they would let me drive so I could see the difference. For now, I'm still happy with the run flats.

 

Just a couple of things to think about - With only 42 miles on the RF's you hardly gave them a chance! I've got about 5600 miles on my RF's, and they do just fine for me! I do laught when everyone posts about the stiff ride. Having driven a Jeep with 33" GoodYear MTRs for the last few years, trust me, the Mini is luxurious on 17" RF's by comparison. I'm sure it could be smoother without the RF's, but.....

One thing everyone needs to remember is that the BMW choice for runflats is for SAFETY - it has nothing to do with being able to repair a tire or drive home and everything to do with maintaining control of the vehicle when you encounter a flat at high speeds. The point of a runflat isn't to just eliminate a spare, it is to provide safe handling in the event of a complete flat. Switching to regular tires and no spare is eliminating a safety feature.

A few weeks ago I was on the freeway and watched as a little Honda Civic went flying by me at about 75 mph when I noticed his back tire was nearly flat...shortly down the road it finally started to break up and then the sidewalls fell apart under the stress and by the time he made it to the shoulder his rim was gone, his tire was completely shredded and he nearly lost control of the car when he stopped to quick on the rim. Now not only does he need a new tire, but a new rim as well. Moral of the story - if you're tracking your Mini on a regular basis, RF's are probably not for you. But if you're driving in congested areas where control and safety go hand & hand, RF's are a good solution overall.

As for weight, just a "summary" of all the significant weight savings. Even if you manage to shave off 30# or more by eliminating the runflats, you still need to carry either (A) a spare (which would weigh close to that) or (B) repair stuff which will add weight and be yet another thing you have to carry in the cargo space of the vehicle. Personally, I need what little storage the Mini has to offer, so I don't want to be bogged down with carrying a spare or a bunch of repair stuff.

Heck, I could probably leave my laptop at home and remove my jumper cables and first aid kit and save almost that much weight.

It seems to me if weight is a concern, the stock RIMS would be a better choice than the RF's. Just my humble opinion.

I'll keep the runflats on my Mini for the safety, since that is why they are there in the first place.

 

I am in the anti-run-flat club here -- the stock Goodyear all-season RF's that came on my MCS sucked in dry, wet, and snowy conditions (and I had almost 1000 miles on them before I could take it no longer). The Dunlop Winter Sport M3s that I replaced the RFs with are superior in all conditions, especially in the snow, but also handle better and are more predictable when pushed in dry conditions.

I would highly recommend a change to those who have yet to experience non-run-flats, and personally think it is best to run a dedicated winter wheel/tire setup and then switch to a dedicated summer/track wheel/tire setup when conditions allow (it takes about 15 min. with a jack and torque wrench to change all 4 wheels). For flat repair carry a Slime kit and a cell phone...

One final note, as an earlier post mentioned, you can go quickly on run-flats as demonstrated by Randy Webb's driving skills at Laguna -- the driver is by far the most important part of the equation. At the same time, however, even Randy will tell you that he would be significantly quicker in a car with performance street tires like the Falken Azenis (which were great at Laguna BTW, and also held up quite well over the course of numerous track sessions throughout the day at the Phil Wicks event) than the same car with run-flats.

 

The published weight for stck 17" wheels is between 24 and 26 lbs. The run-flats are published at 23 lbs. These are the figures I'm quoting.

Eric,

I was responding about grip and side wall stiffnes etc as it relates to suspension/handling performance. There were a couple of comments about that somewhere above. Thanks for keeping me honest.

 

Well, to begin with, if BMW's paramount concern was about safety as you say, and RFs provided this, they would have had every car come with them by default, and they have not. Not only that, BMW has been designing cars that cannot accomodate a spare for many years and they have not come with runflats even when they were available. BMW has employed the use of spares and tire repair kits thru current models likely because the RFs were not up to snuff performance wise, plus they also cost more.

As performance improves in run flats BMW is/will be putting them on more cars (including Ms but prob not lightweight versions), not only because it give the owners peace of mind and its good PR but because it likely reduces BMWs liability and Roadside Assitance demands/costs. They know that the ultimate performance minded will still replace the wheels/tires and will probably also make that a factory option on performance models.

Anyway, no-one debates the safety and convenience advantages runflats can have, its the performance and driveability of the stock runflats that appeared to be at the heart of the initial post and responses regarding runflats. And yes, with the options that have been available in non-runflats, many find that they do perform much better then the OEM RFs in several ways. Its good that they are working on making better ones

PS: Even losing what sounds like a little weight on the wheels has a marked performance and handling/braking impact - much more then if you lose that weight elsewhere on the car.

 

http://www.bmwusa.com/bmwexperience/...hnology/Safety

Run-Flat Tires No more roadside tire emergencies. These self-supporting tires with integrated reinforcements allow tires that have experienced a loss of air pressure to maintain their shape and full use. They can be driven for up to 150 miles at reduced speeds.

Due to low-profile tires, please note: Wheels, tires, and suspension parts are more susceptible to road hazard and consequential damages.
Standard on:
2006 325i Sedan
2006 330i Sedan
2006 325xi Sedan
2006 325xi Sports Wagon
2006 330xi Sedan
2006 650i Convertible
2006 650i Coupe
2005 Z4 Roadster 2.5i
2005 Z4 Roadster 3.0i

Optional on:
2006 330Ci Convertible
2006 330Ci Coupe
2006 525i Sedan
2006 525xi Sedan
2006 530i Sedan
2006 530xi Sedan
2006 530xi Sports Wagon
2006 550i Sedan

 

Yes, as I said they are putting them on more cars (largely to cover their butts since, as I said if safety was really the bottom line and they believed that they were equal in performance the RFs would be on all cars)- when I refer to current model year though I mean 2005.

As I said, in discussing my experience with runflats I am referring to the RFs stock on our cars not what is recently available or coming out in the future.

 

Also, here's the Goodyear site which shows a few pictures of Mini Coopers!

http://eu.goodyear.com/home_en/tires/runonflat/

Again, I'm not saying they are the "best" solution - but it's important for anyone reading these posts to understand that swapping the RF's for regular tires is removing a safety feature.

I plan on driving 'em until the tread is too low, but I'll probably replace them with run flats. My only hope is that the other tire manufacturers wake up by then and start making better performing run flats, since that's the real solution that everyone is looking for.

 

PS: Sorta OT, but it makes me wonder what tires they use when they come up with the 0-60 times?