ARE YOU EXPERIENCING SIMILAR TIRE DEGRADATION ?

The MINI is a 2009 Cooper S, manual, 16X6.5 Bridge-Spoke R94 wheels, ordered new. The car is driven quickly around corners but I doubt that the wheels have ever spun on start or while shifting. Tire pressures are checked cold weekly and maintained at 32 psi all around.

A few weeks after delivery it received the JCW suspension pieces all around.

- Original tires were the Goodyear Excellence RFT in 195/55R16. The outer shoulders showed severe degradation after 3,000 miles at which point the tires were rotated F to R and lasted another 2,500 miles. All four outer shoulders were missing major chunks of rubber while the center surfaces had 50% tread left.

Tire pressures were experimented with and tire temperatures were measured but in Florida all roads are straight and flat ...

- At this point a set of fixed IE camber plates were installed and alignment was checked 4 times at 4 locations. Don't ask.

- A set of Michelin Pilot SX in 205/55ZR16 non-RFT were installed.
Now the shoulders AND the rest of the tread were wearing evenly albeit still at twice the rate of wear for the fronts. No degradation of shoulders but the tires were completely worn within 6,000 after the usual rotation at 3,000 miles.

- Next came a set of Pirelli PZero RFT in 205/55R16 and alignment was checked twice.
The Pirellis are wearing evenly and nicely while providing the best wet and dry grip and comfort experienced so far with all tires. After being rotated at 3,000 miles, they are now ready to be replaced after the usual 6,000 miles.

So far the MINI has cost more in tires and alignments than in gas and oil ( I change synthetic every 5,000 miles at my expense).

The dealer makes fun of it as he happens to have discovered that I road raced many moons ago in Europe. No sympathy there.

This is as bad as the cost of printer ink which can rapidly outpace the cost of the printer.

 

That is a lot of tires for street driving.

I run the 205/45 17 on my all seasons Contis, I estimate perhaps 10,000 miles so far of winter driving and maybe 8,000 miles of thread more. I go through summer tires like chewing gum as well but the car sees a fair bit of HPDE.

 

32 psi? are you sure the label doesn't say 35psi ?

 

My original RF Contis have about 28,500 miles on them, but are at the end of their life. I maintain 35 p.s.i. and tires have worn very even. Sounds like you should consider buying stock in your favorite tire company.

 

ARE YOU EXPERIENCING SIMILAR TIRE DEGRADATION ?

"The MINI is a 2009 Cooper S, manual, 16X6.5 Bridge-Spoke R94 wheels, ordered new. The car is driven quickly around corners but I doubt that the wheels have ever spun on start or while shifting. Tire pressures are checked cold weekly and maintained at 32 psi all around."

Sounds like you're running them way too low. I don't have the Mini in the garage right now to look in the manual, but it seems 35-38 psi would be better for getting some wear on the center of the tread and also give better handling. If you're running off-road in the sand, low pressure may be better, but I doubt if that's the case here. I'd suggest pumping up the pressure to spec or a bit higher.

 

Thanks guys but the pressures are fine.

Running low pressures would wear the shoulders more than the centers. Not the case here. The tires wear absolutely even.

The mfrs labels are general guidelines for loads of more than one person, again not the case here as the car is driven 95% of the time with only the driver on board.

Also consider that with my 205/55X16 tires I am running at 12.0 liter a 11.17% larger interior volume than the 10.74 liter volume of the 195/55X16 stock size. My 32 psi therefore translates to a 36 psi pressure on the 195/55X16 stock tires.

Temperature measurements taken over the outer shoulder-center section-inner shoulder are very even and indicate proper pressures as well. Chalk markings on the outer side walls also indicate proper inflation levels.

The Continentals have at 400 AA a much higher treadwear rating and are expected to last longer, maybe twice as long as the Pirellis which have a 220 AA rating. In my application I wouldn't be surprised to get maybe 12-15,000 miles out of the Continentals. Consider though that treadwear ratings are not an exact science but rather arbitrary manufacturer figures.

 

Kraut, I think you really should stick to the mfr's tire pressure recommendation, as per the label on your car. IIRC mine reads 35. In fact, there is a HIGHER pressure for the fully-loaded-going-fast, but never one for "only a driver". I've been only a driver just about 90% of the car's use too, and I run the recommended 35, and (on my previous car where it also was 35) my tires have lasted... (and this is east coast roads!)

edit: just realized you aren't running stock sizes. ok, that might account for differences...maybe.

 

Thanks isthar but see my last post. My 32 psi translate to 36 psi on the 195/55 stock size. Fact, not maybe.

 

I used to drive a lifted Jeep Cherokee and it is pretty common to have to use lower tire pressure when you run a larger tire (a tire shop damn near got me into an accident over inflating my tires one time). Dropping from 36 to 32 seems like a little much but you are doing all the right things to check so that pressure wouldn't seem to be the problem.

I found increased camber fixed the problem for wearing out the outer edges of my tires too fast. Looks like you found the same fix.

To me it seems the only thing left is an alignment problem. Most likely toe. I'm not an expert on alignment but I know you want as little as possible.

Could worn control arm bushings be causing the problem? That might cause a problem with alignment under acceleration and braking.

Like I said. I'm not an expert, just guessing a little based on all the reading I've done on here.

 

I got about 21k out of my Falken 452s in 215/45/r17s. They held up well all the way to the end even had grip left even though the wear bar was showing. They just got really loud. mY BFgoodrich T/A KDW 2 tires grip good could be better but they are suppose to have a pretty long tread life. I have only logged about 2k on them but they look good.

 

Especially with even wear across the tire tread, I would wonder if you're scrubbing due to a toe setting. What are your alignment settings, KrautHammer?

 

Front axle.

Total Toe: 0 deg. 12 min. Even 6 min per side.
Camber: Neg 50 min.
Toe offset angle: 1 deg. 20 min.
Caster: 4 deg. 25 min.

Before somebody jumps at these remember that the car is all JCW all around.

No scrubbing here.

 

We for a while went through tires on my wife's car faster than most people go through wiper blades.

I can't/won't argue with you about the wear pattern...but I do know that my wife managed to go through at least two tires quickly because of running at that low a tire pressure...at least I believe that to be the case.

Also...I would give a for the Continentals...since my wife had her Pirellis switched out...no more problems

 

grip = rubber molecules interlocking with road surface molecules

wear = interlocked rubber molecules being torn off the tire

You maximized the grip from your suspension. You select the highest grip street tires. You utilize that grip in your daily driving.

My advice is to go autocrossing.

 

It takes a racer ... to figure it out and you are correct hsautocrosser.

Once the tires' four contact patches remain unchanged and the car's suspension remains flat through the arc, this car becomes a veritable pencil eraser through the corners. No different than running a few track days and unfortunately just as costly.

 

The more grip you use = more wear on the tires. More turning g force = more wear at the edges. Seems to be one of the few explanations left. What mpg are you running? Perhaps someone in your family is a closet racer.

I know you do not think it is tire pressure but try adding one psi or two to see what that does.

 

Just another thought from another old road racer -- with the pressure a bit low, you are allowing a lot of flex and friction between ALL of the molecules involved, gas and rubber. The flexing is no doubt causing additional heat and you may find that you are actually winding up with tires a bit over inflated as you drive. We used to have that problem with the old Goodyear bluestreaks, you cool the tire on the road a bit by adding a bit of pressure to reduce carcass flex.

Have you done any measurement of tire pressure after a particularly hot trip???

 

For street driving a 36 psi equivalent to the 195 OEM size isn't low for general rolling around.

We do agree however that driving on surface streets at "track cornering speeds" requires track inflation pressures but ... track tire temperatures remain fairly constant once the tires have been warmed up and that is simply not the case with street tire temperatures.

So I have to compromise to inflation levels that maintain some comfort when hot and this is one of the reasons for selecting the 205/55X16 size which results to a "Tire Suspension Comfort Value" of 6.5, up from the 5.6 of the 195/55X16 OEM size.

Now to the question about temperatures:

- At 30 psi the edges were running >180F, the centers were at ~150F so I kept adding 1 psi-cold for every 5F delta and this is how I got to the 32 psi.

- At 36 psi the centers were running >180F while the edges were at <140F. I kept reducing pressures (1 psi-cold for every 5F delta) and I was back to ... oh surprise ... 32psi.

As for tire pressures rising with higher temperatures this is the nature of the beast and I'm not about to go Nitrogen on a lowly road commuter.

 

my advice? do what i did and get some dunlop sp sport signatures (you must order them localy and have them installed by an authorized dealer for this to work, or the warranty will not hold, found this out the hard way) as they are pro-rated for 50,000 miles, plus the fact that for my size they were only like ~$125.00 installed per tire isn't bad either.

 

Good idea but no RFT in my size (205/55X16).

After the initial poor performing Goodyear RFTs I went to the Michelin non-RFTs and now back to RFTs with the PZeros and I must say they are quite good. Other than the pencil eraser life span.

 

- Original tires were the Goodyear Excellence RFT in 195/55R16. The outer shoulders showed severe degradation after 3,000 miles at which point the tires were rotated F to R and lasted another 2,500 miles. All four outer shoulders were missing major chunks of rubber while the center surfaces had 50% tread left.

How can you say the tires wore fine after stating this? Seems a contradiction. Are they chunking or wearing fine? Did you jump the pressure? My Mini says 38 PSI and 41 PSI if you are gonna go fast. 32 PSI is way too low and will cause problems.

 

The OPs 16" tires have different recommended psi than your 17".

 

Yes the 16's sticker omits the reference to 41psi, but 38psi is the recommended pressure for high speed. Still, the OP has some solid logic for his choice of 32psi. I'm convinced that low pressure is the culprit for his rapid wear, but the pressure he has selected likely provides the handling feel and performance he wants.

It appears to be a trade off. If he wants max performance, it seems that he must accept low tire mileage as a cost of operation. He can likely improve his tire mileage at the cost of handling.

I'm wondering at this point if the 6.5 inch wheel width is part of the issue. A wider wheel will provide a larger air volume and will move the flex point on the sidewalls outward a bit perhaps allowing higher pressure while still holding the tread patch constant at the tire shoulder. Have you considered wheel width in any of your calculations, KHammer?

 

Yes.

195/55X16 on 6.5X16 = 10.74 liter volume, 5.6 TSCV

205/45X17 on 7.0X17 = 9.91 liter volume, 3.3 TSCV

205/55X16 on 6.5X16 = 12.0 liter volume, 6.5 TSCV

(TSCV Tire Suspension Comfort Value.)

Note that the 205/55X16 has twice (!) the TSCV of the 205/45X17 and this is the thinking for my selection when I ordered the car with 16" wheels and outfitted it with 205X55 tires.

Tire pressures are directly related to tire volumes (as any racing engineer who has changed wheel and tire sizes during the course of testing on a track is aware off) and some of the above posts seem to ignore this basic fact.

Therefore please consider that my 205/55X16 have a 21% (!) larger volume than the 205/45X17 and the 32 psi on my tires translates to 39 psi on the 205/45X17 tires.

Again, if the 32 psi were too low the tires would be wearing excessively at both shoulders and the temperatures of the shoulders would be hotter than at the centers but as you see in my earlier post that is not the case.

BTW the stock suspension car is such a pusher in the corners that I simply can't see any tire at any inflation level not loosing its outer shoulders in very short order as was the case with my original Gooyears.

 

Interesting -- I agree fully about the pushing issue. I'm kinda new to the Mini stuff, but I've figured that a change in the rear sway bar was to be the first real modification that I was to make. I had planned tgo go to 17 inch wheels, but your calculations have me thinking again.

I have been watching my own tires pretty carefully. I keep tham at 39 rear and 36 front right now. I arrived at those by a pretty non scientific method. I just measured the skid marks from a straight line stop (I know, its an old method, but it always served me well and I have no real measuring tools anymore to check things like tread temp).

Is it possible that there is just a lot of tire slippage in normal driving that could be causing the high wear? My tires (OEM Bridgestone RFTs are at 12K right now and they are about 70% worn. I figure that they will be history by summer's end and will have abotu 20K on them when they go away.

I've been debating tires with myself, and spent a lot of time looking to see what everybody was running on at MOTD -- nothing definitive came from that although the Continental DW asymetrical tread pattern looked to have some good design features vis-avis the Mini, eg., very hard thick and beefy tread on the outside edges, and a complex set of siping grooves on the inside edges.

Still, ti seems odd that you are gettng such short tire life. Most here are getting much better, and I can find no one who has quite the wear issues that you have described.

Are you getting any indication of vibration from the drive train anywhere?