DailyDriver
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Answer: Runflats are a bad idea, got it.
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Ditch spare, use runflats?
- Thread starter DailyDriver
- Start date
I honestly think its kind of a silly idea. If you were going full race....fine. But for a DD...pointless. That 34 pounds is such a moot point. I'll give you the extra storage space...kind of. Really, what are you going to put there? Think it weighs 34lbs? Now you are right back to where you started plus the extra cost of run flats.
DailyDriver
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Good point.... but an additional reason to look at runflats is the added reliability of not having the tire disintegrate and break the fender / rim etc during a high speed blow out. When you add up all the "advantages" of runflats, it starts to make a little more sense. When the OEM tires wear out, I'm sure I'll be upgrading to some other high quality "expensive" tire regardless, so I'm not overly worried about expense... unless it's truly out of hand. (I have not yet looked at runflat tires for this car / prices.)
How often do you have a high speed blowout? With the tires today, especially the higher end models and Z ratings...it is less of a concern in my mind. The only high speed running that I really do is on the track also so my high speed runs only happens in bursts. Unless you do prolonged high speed runs you have little to worry about IMO.
DailyDriver
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DailyDriver
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hell to the no.
- Although there are good run-flats, there are always BETTER regular tires available.
- Run-flats are more expensive.
- Run-flats are never AS comfortable as a normal tire.
- Run-flats are heavier. You just ditched 40lbs of weight the car barely cares about in favor of a few pounds of unsprung weight that the car DOES care about.
- In a car designed to carry a spare, it's generally engineered as part of the crash safety system. You just saved 40lbs but killed someone in the back seat.
- Although there are good run-flats, there are always BETTER regular tires available.
- Run-flats are more expensive.
- Run-flats are never AS comfortable as a normal tire.
- Run-flats are heavier. You just ditched 40lbs of weight the car barely cares about in favor of a few pounds of unsprung weight that the car DOES care about.
- In a car designed to carry a spare, it's generally engineered as part of the crash safety system. You just saved 40lbs but killed someone in the back seat.
iam sorry but i would like to know what are runfalt tire??
hell to the no.
- Although there are good run-flats, there are always BETTER regular tires available.
- Run-flats are more expensive.
- Run-flats are never AS comfortable as a normal tire.
- Run-flats are heavier. You just ditched 40lbs of weight the car barely cares about in favor of a few pounds of unsprung weight that the car DOES care about.
- In a car designed to carry a spare, it's generally engineered as part of the crash safety system. You just saved 40lbs but killed someone in the back seat.
DailyDriver
Member
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I wouldnt do it to be honest...
As a sidenote, take a look at a blog that was recently published by Autocar Magazine:
http://www.autocar.co.uk/blogs/stillatthewheel/archive/2009/10/26/bmw-running-from-run-flats.aspx
- Heavier tires as jeebusm3 said, you wont be saving that much weight as youd think
- Much louder tires
- Theyll make the ride much harder, which, for some people (def. not me), is already harder than theyd like
- Dont know about your Vette, but in my Mini S, runflats werent as grippy as normal ones
- Much more expensive, which makes me want to stick to normal ones because, if i have to change them, id rather pay for a great normal tire, instead of a not so great runflat for the same amount...
As a sidenote, take a look at a blog that was recently published by Autocar Magazine:
http://www.autocar.co.uk/blogs/stillatthewheel/archive/2009/10/26/bmw-running-from-run-flats.aspx
Runflats are tires that have their sidewalls reinforced, which according to BMW's recommendations, allows you to continue using a flat tire for about 100 km's (62 miles) at an av. speed of 80 kph (50 mph) so you can find a shop to repair it... As long as its not a damaged sidewall, they are repairable, just as any tire would...iam sorry but i would like to know what are runfalt tire??
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DailyDriver
Member
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Run-flats not only increase un-sprung mass, but also rotating mass. Lowering rotating mass increases available power and improves brake performance.
I have just finished some research for my job dealing directly with this sort of thing. ESTIMATED FROM MY RESEARCH: eliminating 1.3% of your static mass (the spare) is probably not worth the 5-10ft of braking distance you'll add or the 1-4% WHP loss you'll see from more rotating mass.
Just in case you needed that last nail in the decision coffin... so to speak (burnout)
I have just finished some research for my job dealing directly with this sort of thing. ESTIMATED FROM MY RESEARCH: eliminating 1.3% of your static mass (the spare) is probably not worth the 5-10ft of braking distance you'll add or the 1-4% WHP loss you'll see from more rotating mass.
Just in case you needed that last nail in the decision coffin... so to speak (burnout)
I just went to tire rack, plugged in 225/40/18 and filtered on Max and Extreme perf summer tires.
Runflats (7 varieties): $241-$289
Normal (40 varieties): $80-$237
Then I picked a popular (but expensive) brand tire that is available in both flavors, the Michelin Pilot Sport PS2. The price penalty was actually very small for this tire. $242 RF vs $230 normal.
Most of the tire stats were identical, tread depth, UTQG,etc. But there were a few notables. (I'm using NT for normal tire and RF for run-flat)
Max Load: 1389lb NT / 1235lb RF
Tire Weight: 21lb NT / 24lb RF
Anyone that knows anything about wheels, tires, brakes, and suspension; knows that 3lbs of unsprung weight is nothing to sneeze at, and if it can be avoided...it is. One of my main factors in tire purchase, after I've narrowed down my choices, is actually tire weight.
Runflats (7 varieties): $241-$289
Normal (40 varieties): $80-$237
Then I picked a popular (but expensive) brand tire that is available in both flavors, the Michelin Pilot Sport PS2. The price penalty was actually very small for this tire. $242 RF vs $230 normal.
Most of the tire stats were identical, tread depth, UTQG,etc. But there were a few notables. (I'm using NT for normal tire and RF for run-flat)
Max Load: 1389lb NT / 1235lb RF
Tire Weight: 21lb NT / 24lb RF
Anyone that knows anything about wheels, tires, brakes, and suspension; knows that 3lbs of unsprung weight is nothing to sneeze at, and if it can be avoided...it is. One of my main factors in tire purchase, after I've narrowed down my choices, is actually tire weight.
Max Load: 1389lb NT / 1235lb RF
Tire Weight: 21lb NT / 24lb RF
Anyone that knows anything about wheels, tires, brakes, and suspension; knows that 3lbs of unsprung weight is nothing to sneeze at, and if it can be avoided...it is. One of my main factors in tire purchase, after I've narrowed down my choices, is actually tire weight.
12lbs of rotating mass (3lb x 4tires) is huge. Especially at the large diameter of the tire!
DailyDriver
Member
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A buddy of mine used to have a GLI that got a flat (45 or 50 series tire if I recall), his wife drove it around for about 20 miles doing errands and didn't notice anything. My buddy hardly noticed anything driving it to the garage to get it repaired, it had picked up a nail.
I guess if tread doesn't catastrophically fail you have "run-flats" assuming the side-wall is low and stiff enough. On my Speed3 I couldn't tell visually that one of my tires had dropped to below 20psi, the TPM sensors yelled at me and I checked my tire pressure...
You also have to look at how the tire fails... if you're running on a flat tire or low on pressure and the tire heats up enough for the tread to disintegrate, even run-flats will blow-out. They might just buy you enough time to slow down and get to a garage, assuming you did something like run over nail.
I guess if tread doesn't catastrophically fail you have "run-flats" assuming the side-wall is low and stiff enough. On my Speed3 I couldn't tell visually that one of my tires had dropped to below 20psi, the TPM sensors yelled at me and I checked my tire pressure...
You also have to look at how the tire fails... if you're running on a flat tire or low on pressure and the tire heats up enough for the tread to disintegrate, even run-flats will blow-out. They might just buy you enough time to slow down and get to a garage, assuming you did something like run over nail.
Stavesacre21
Member
- :
- 2010 Mazdaspeed3
I agree with many of the rest...what's the point of going to runflats on a Mazda?? Is the 40lbs really gonna be worth it?? On the vette I could see you wanting every pound off, not to mention it's initial use of run-flats.
As others have said, unless your turning it into an ultimate performance track machine, it's gain isn't gonna be worth it. You've got SOOO many better choices of non-run flats to choose from that I wouldn't drop the spare specifically for that purpose. That and the fact that a real spare is always gonna be better then a can of goo. I'd prefer to keep from ruining my rims if possible.
As others have said, unless your turning it into an ultimate performance track machine, it's gain isn't gonna be worth it. You've got SOOO many better choices of non-run flats to choose from that I wouldn't drop the spare specifically for that purpose. That and the fact that a real spare is always gonna be better then a can of goo. I'd prefer to keep from ruining my rims if possible.
DailyDriver
Member
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