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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Wheels and Tires Forum Sponsored by The Tire Rack > Runflats improve performance?



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Wheel offset calculator courtesy of BimmerPost.com. You may use this calculator to calculate what tire sizes you might need if you upgrade your tires, or what wheel sizes/offsets are compatible with your car.
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         New Wheel Width  inches                  New Wheel Offset  mm.
 
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  Difference in diameter (in.)
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      02-15-2013, 05:47 AM   #23
Noncom23
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Yes at city speeds I was shocked at the smoothness of the run flats.
I was sure I would hate them. They are great for the design at
those speeds.

However, as many have stated, when I get above 80mph on a
curve the hopping of the back wheels especially is a pain.
The car holds, and I dig with acceleration to see if they will
break lose. So far up to 100mph they hold.

I can only imagine the dw's have less hop with the more
smoothness and equal or better performance. Get what you
like. The only risk is a flat. imho.
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      02-15-2013, 10:03 AM   #24
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Runflats are not better than non-runflats... at all. It may FEEL faster because of the stiff (sporty) ride.. but it's not even in the same league as a good non-rft. I've tracked them both.

Characteristics:
RFT: bumpy on corner entry, slides way too easily, jumps over slight road imbalances, OMG TRAMLINING - don't hit a pothole.. or else.. EXPENSIVE as all hell

Non-RFT: softer, sidewall flex means more tread on the ground to grip, WAY MORE grip, feels slower but is way faster, will save your rims when you hit a pothole, way more predictable mid-corner and exit, easier to correct oversteer.

Bottom line is that the RFT's feel like the car is on stone wheels.
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      02-15-2013, 11:05 AM   #25
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Because of the stiffer sidewall, RFT won't roll under the car and has more rubber to the ground. This maximizes the traction. However, in the wet, soft tire is quicker:

Sport Auto:
Handling dry (2770 m track):

B-stone RFT: 1,17,0 min
B-stone Std: 1.19,4 min
PS2 RFT: 1.17,4
PS2 Std: 1.17,8 min

Handling wet (2300 m track)

B-stone RFT: 1.49,3 min
B-stone Std: 1.44,7 min
PS2 RFT: 1.44,2
PS2 Std: 1.42,5 min
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      02-15-2013, 12:41 PM   #26
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Quote:
Originally Posted by jippii ensio View Post
Because of the stiffer sidewall, RFT won't roll under the car and has more rubber to the ground. This maximizes the traction. However, in the wet, soft tire is quicker:

Sport Auto:
Handling dry (2770 m track):

B-stone RFT: 1,17,0 min
B-stone Std: 1.19,4 min
PS2 RFT: 1.17,4
PS2 Std: 1.17,8 min

Handling wet (2300 m track)

B-stone RFT: 1.49,3 min
B-stone Std: 1.44,7 min
PS2 RFT: 1.44,2
PS2 Std: 1.42,5 min

Negative!

Tire is a component of the entire suspension system. The example above shows only the results on this one particular vehicle. A different vehicle with different suspension system could have completely different results for these tires.
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      02-16-2013, 01:06 AM   #27
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Just ditched my RFTs(B-Stone) for all-season ZE912 Falkens and the ride feels better, went flatout today and the car felt faster since each tire only weighs 25lbs compared to the 30ish pounds the RFTs weigh.
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      02-17-2013, 10:57 PM   #28
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So, for those of you who have ditched the RFT: Do you carry around a spare now or just accept the risk of getting a flat and having to call the tow truck?
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      02-17-2013, 11:14 PM   #29
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I carry repair kit and portable compressor when running non-rft. Good enough to plug small punctures.
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      02-19-2013, 06:48 PM   #30
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Quote:
Originally Posted by 335dFan View Post
This may be the default dealer SA response, since the dealer near me said almost the same words ("whole package was designed as a system and the DSC and everything else is all engineered to work together"). Looking at it from the dealer's point of view (forget about the financial aspects for a minute), they may be weary of customers making their own changes outside of the BMW party line, and then running to the dealer when something is not right, and it relates to something the customer did outside of BMW's comfort zone. There is always some consequence for each of our choices. Nothing wrong with that.

I just listen to all sides, read a lot on the forums and other places, make my choices in as informed a way as I can, and accept the results and consequences, or trip up and try something else. On the tire issue, I ended up just putting RFT Blizzak LM-25 on for the cold season, and I will probably put non-RFT on when the warm weather comes back, even though I have a lot of tread left on the OEM RFT all-seasons. The logistics influenced me, because I want to leave the winter tires on the OEM wheels, and the OEM RFT all-seasons won't fit on the new wheels I want, so I decided to bite the bullet. Now the only decision is whether to buy a fifth wheel and tire, or get one of those aftermarket spares.
I completely agree and I did the exact same thing. This past fall, I put Blizzak LM-25s, which were OEM approved RF snow tires on my 17" OEM wheels, and sold my all-seasons, which still had a ton of tread life left. I figured that even with roadside assistance, I'd rather not get caught with a flat on non-RF up in the mountains when I'm going snowboarding.

Now, for this summer, I've just ordered some 19" Morr VS8.2 wheels and Michelin Pilot Super Sport tires (non-RF). I spend a lot of time with racers and all of them have changed out to non-RF.

I'm expecting some performance gains based on the grip of the tire and the overall weight savings. I might get more comfort on the non-RF, but I am going from a 17" to 19" wheel, so I've got much shorter sidewalls coming. However, I'm saving over 7lbs per wheel!!!! 4lbs on the rim and 3lbs on the tire! That my friends, coupled with the grip from the Pilot SS, should provide a very nice improvement.

This was not a cheap investment at over $7k for the new rims and both sets of tires (sold my OEM all seasons for $300), but your wheels/tires are the MOST important item on your vehicle when it comes to the combination of performance and safety, so don't cheap out!
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      02-19-2013, 07:49 PM   #31
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Quote:
Originally Posted by bplant13
Quote:
Originally Posted by 335dFan View Post
This may be the default dealer SA response, since the dealer near me said almost the same words ("whole package was designed as a system and the DSC and everything else is all engineered to work together"). Looking at it from the dealer's point of view (forget about the financial aspects for a minute), they may be weary of customers making their own changes outside of the BMW party line, and then running to the dealer when something is not right, and it relates to something the customer did outside of BMW's comfort zone. There is always some consequence for each of our choices. Nothing wrong with that.

I just listen to all sides, read a lot on the forums and other places, make my choices in as informed a way as I can, and accept the results and consequences, or trip up and try something else. On the tire issue, I ended up just putting RFT Blizzak LM-25 on for the cold season, and I will probably put non-RFT on when the warm weather comes back, even though I have a lot of tread left on the OEM RFT all-seasons. The logistics influenced me, because I want to leave the winter tires on the OEM wheels, and the OEM RFT all-seasons won't fit on the new wheels I want, so I decided to bite the bullet. Now the only decision is whether to buy a fifth wheel and tire, or get one of those aftermarket spares.
I completely agree and I did the exact same thing. This past fall, I put Blizzak LM-25s, which were OEM approved RF snow tires on my 17" OEM wheels, and sold my all-seasons, which still had a ton of tread life left. I figured that even with roadside assistance, I'd rather not get caught with a flat on non-RF up in the mountains when I'm going snowboarding.

Now, for this summer, I've just ordered some 19" Morr VS8.2 wheels and Michelin Pilot Super Sport tires (non-RF). I spend a lot of time with racers and all of them have changed out to non-RF.

I'm expecting some performance gains based on the grip of the tire and the overall weight savings. I might get more comfort on the non-RF, but I am going from a 17" to 19" wheel, so I've got much shorter sidewalls coming. However, I'm saving over 7lbs per wheel!!!! 4lbs on the rim and 3lbs on the tire! That my friends, coupled with the grip from the Pilot SS, should provide a very nice improvement.

This was not a cheap investment at over $7k for the new rims and both sets of tires (sold my OEM all seasons for $300), but your wheels/tires are the MOST important item on your vehicle when it comes to the combination of performance and safety, so don't cheap out!
Hadn't thought about selling my OEM RFT. Mine have only 6-7k on them.

I think will go to Apex ARC-8 18" but only as wide as will fit without changes. Will probably do the same tires as you. But may get a donut spare for long trips.
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