Is the mushrooming problem only on MINIs with run flats or with all MINIs?

Thanks...

 

It's not a problem if you have smooth roads and don't hit anything.

It becomes a problem if you hit a pothole of significant size at speed.

With runflats your tire is very stiff on the sidewall and can transmit force to your rim and suspension or strut tower plate causing it to bend or malform.

With non runflats you can choose a taller sidewall profile when using a 15" or 16" rim. This helps a little.

Any MINI can get mushrooming. Be careful how you drive. Slow down if you are in unfamilar territory or if it's not clear weather.

 

AND I hate to say it but at a minimum, get the SRP's from M7. Several threads, check them out!

 

The mushrooming happens 'cause the suspension was designed around stock 15" light-weight rims and regular tires, then at the 11th hour BMW/MINI decided to throw runflats into the mix, in particular because they moved the battery in the S to the boot for better weight distribution. A runflat rim and tire weighs 20lbs more than a reg rim/tire and not what the suspension was spec'd for, and that extra 20lbs per wheel being slammed into the struts when you hit a pothole, along with the stiff sidewalls of the runflats not providing much "give" at all, just beats the suspension to death. Switching to light-weight rims and reg. tires helps a LOT! Gong smaller helps as well, as smaller tires actually put more rubber between the road and the rim. I went to stock MINI Rocket 15" rims with Continential tires, and WOW! What a difference in both handeling and ride. Night and day. Car is MUCH nimbler on the road, and the ride is vastly improved.

 

I really don't think that is true because there are people out there that have light weight 15s w/o RFs and have mushrooming. From what I heard, the older Z series BMW had this same issue when they first came out and BMW fixed it.

 

Not ENTIRELY true. The 17" S-lite combo+runflat tires weighs about 20 lbs more tghan the 15" Holey+non-runflat wheel tire combo, but its hardly the runflat tires that are responsible for this 20 lb difference.

Its the WHEELS that weigh a TON, the S-lites weigh 27 something pounds, as opposed to the Holey's that weigh FAR less, in the neighborhood of 15 ish (I think less, but I'm not sure). The runflat tires aren't responsible for much weight gain though, its the larger wheels and larger tires that account for most of it.

For reference, in 205/45-17, The dunlop SP Sport 9000 (non RF) weighs 20 lbs, the Dunlop SP Sport 9000 DSST (RF) weighs 21 lbs. Its not the runflats that are responsible for the huge weight gain, its the larger wheels and tires. The extreme sidewall stiffness of the runflats contributes in that it transmits more force to the suspension than a non-RF tire (which is why people complain about the ride with RF's, but also why people complain about numb steering feel when going they replace the RFs), but lets be realistic about the weight gain that comes from the RF's. . .

 

That's what I said in my post "RIM & TIRE" weigh 20lbs more. I had 16" rims & Goodyear runflats, and I know there was a 20lb difference between those and my new MINI OEM Rocket rims w/OEM Continentals, as I noticed the big differrence in weights while changing out the wheels, and weighed them out of curiosity. And the "suspension not designed for runflats we changed to at the last minute" was acknowledged and commented on by the BMW/MINI design team when asked why the huge difference in ride between the BMW3 series with runflats, and the MINI:

"The shorter MINI wheelbase makes a difference in ride, however the bigger issue is that the BMW’s decision to fit runflats tires on the MINI came at the last moment in its original development cycle. Therefore the current suspension was not designed to be used in conjunction with runflats. The newest 3 series on the other hand has a suspension that was engineered from day one to work with runflat tires. If you switch from runflats to normal tires (as quite a few owners do) you’ll actually be experiencing how the MINI’s engineers originally intended it to feel."

....and the rest is just physics of that added weight. Put on the boxing gloves and spar with a friend - take one to the chin. Then have your friend add a roll of quarters inside his glove and tap you again. When you wake up again and get off the floor, you will have an idea the extra punishment the front suspension takes with that added 20lbs per wheel being slammed up against the strut/suspension when you hit that pothole.