After putting a couple hundred miles on the new 2010 MCS, I received a complaint from the wife that the car was "squirrely" at the rear during highway driving.
Some investigation revealed tires at 30psi except for right rear at 28psi.
Door sill sticker and owners' manual call for 38 psi, which seems excessively high to me.
I dutifully followed the manuals' recommendations though, and pressurized the tires, and reset the TPM monitor...

So, a few questions I hope you more experienced Mini owners can help me with:
-why would such high tire pressures be required for such a light car?
-is there a reason the dealer would have delivered the car with only 30 psi?
-why didn't the TPM show a warning on the dash when the rear tire went down to 28psi?

Won't the 38 psi make the car ride very stiff? (I haven't been able to drive it myself yet, since increasing the tire pressures.)

On the plus side, the car came with Bridgestone Potenza RE050 tires (RFT). I've previously had non-RFT Potenzas and was very happy with the balance of grip, low noise, and durability. These are quite sticky even with RTF technology.

I am now contemplating switching over to these on my 1-series when the Pirelli Euforias' need replacing.

TIA,
bill

 

36-38psi is the recommended for basically all Mini and BMW models.
36-38 isnt excessively high... most tires say do not exceed 50psi
The tire pressure monitoring system needs about a 5 psi difference between reference tires to set the light. Why they would set them at 30 psi I dont know.

 

38 PSI is recommended for the MCS if you have the lower profile tires. The stock 55 series tires that come on 16 inch wheels call for 33 PSI. Yes, it's stiff, but the air volume of the low profile tires is not great, and you need to make sure you don't bottom out over bumps. Keep in mind, if your wife drives above 100 mph, she should run 41 PSI

The TPS is not all that sensitive, one reason many people don't like it.

Your dealer probably screwed up, although you should monitor the tires for a while to make sure they are holding air OK.

 

Allright then, I'll stay with the manual's recommendation. It just seemed a little high to me.
Good input on the 5psi diff. likely being needed to set off the TPMS warning, and thanks for all the responses which increased my confidence. I'm still learning this little beast.

bll

 

you think the dealer checked all this at delivery - pressure at the recomended level?



the kid that prep'ed the car is 17 years old and makes minimum wage . . .

I'll bet you think the wheels are balanced and the front end is aligned too



how silly . .

these are the places I go after leaving the dealer and I can tell you that it is money well spent

 

Two weeks ago, I had to take my mini into the dealer (warrenty oil change and new brake pads), they also check my tires and when I got home I checked them and they were set to 40-41PSI. So I removed some air back down to 38PSI. Today, I had to take my car to a local tire store and got my runflats patch up (small screw in one of the wheels) and they also put in about 40PSI. WHY? On both paperwork, both places put down 38PSI as what they put in. Is my digital tire gauge off? With 40PSI, any problems with running it take way?

 

With 17" rims, I run 36 psi F and R with RFT so they are not so stiff. With non RFT, I tend to run 38 psi. These are cold pressures.

Just a matter of comfort when I am on the rough roads.

There is no harm in experimenting a little with the tire pressures to see what you like. Just don't go too low or too high.

 

I have run into gages that were a pound or 2 off or different (not knowing which was exactly right). This includes an expensive one. The difference could be theirs or yours. But this is only a modest difference that should not be a problem. However, no matter what the gage says, it is probably important to keep the tire pressure the same side to side with the front to rear differnce on the tag. That is, if the gage says 40 on one side it best say 40 on the other. This will insure consistant handling. Once you get comfortable with the car's handling you can play with the front to rear balance to change the understeer characteristics. But big difference in tire pressure here can be a problem.

As for the higher tire pressures on tires, it lowers rolling resistance and increases gas milage.

 

Hey Eddie.

It is about time you bought yourself a good tire pressure guage and retire that pencil thing you use

 

BillG, If you just increased the tyre pressure by 4 or 5 lbs in order to get up to spec. the pressure warning system may get irritated. You may get a yellow warning triangle just left of the trip milage readout. This will be followed by the tyre warning symbol. There is a simple reset procedure in the manual to preform after you have the pressure where you want it.

 

Because when you got home - the tires were warm.... Always check them cold.

 

Hi Moe,

I set pressures using one of those accurate tire gages, then performed the TPMS reset. It is very similar to my BMW 1-series, so I am pretty familiar with it. But thanks for the heads up...

Bill

 

Yeah, silly me!

 

Actually, I think you can solve you wife's complaint by ditching your RFTs. Let's face it; they suck regardless of what pressure is in them. I run on Potenza Grids .

 

I agree with MCSfanboy....ditch the runflats, you ditch the traming on the highway.

I run just enough air to get a firm footprint across my entire tread width. Too much and you start to wear the crown of the tires (centers), too little and you put excessive wear on the outer edges. It's just a matter of the old skool credit card trick...but check em cold, cause adjusting when hot is a moot point.

215/50-16 Kuhmo ASX here on 16x7s...33psi cold.

Now if you're an aggressive driver all the time, then there's other issues we should discuss

 

I would rethink that - you will loose ride comfort BIG time on your 1-series. Just ditched the OEM runflats at only 2,500 miles for the Michelins in my sig - greatly improved ride comfort......

If you want to feel the difference - go test drive a Justa Cooper - like being on a cloud compared to runflats.

 

Why so? The 1-series has run flats, it's just that the Euforia's tread and compound seem to be more "all-season" type vs. The Potenza's "dry weather" leanings.
So the suspension on the 1 is tuned for the stiff RTF's. The ride quality is actually quite good (I came off a 325 w/o run flats so I know the difference). I was commenting on how I liked the grip from the Potenza's vs. the Euforias.

Bill

 

If you are happy with the ride quality then go for it, I too was once a runflat zealot until I felt the difference, in our MINI anyways....

 

That's a good tip. I'll keep an eye on the tire wear pattern as we put more miles on the car.

The whole RFT issue has been discussed ad-nausem in this forum and at the 1-Addicts forum as well; I'm not looking to ad to that!
And, I'm sure the tramlining w/RFT's is true, but my wife is not a true "enthusiast" that will appreciate increased grip levels from high performance conventional tires (Though she would likely appreciate improved ride comfort...). She is happy enough with this car's ride and handling as is (And I'm happy she could discern a low pressure condition!).

The RFT's are actually a useful feature for both of us (at least we think that at the moment given the convinience of dealing with a flat tire. We'll see how that works out over time if I can't plug or repair a tire with a screw in it. I'm not looking forward to replacing these tires though($$$).

Like I've commented in another post, I am generally happy with my RFT's(on the 1-series), but could use more grip, as I can get them to slide pretty easily with aggressive driving; more a function of the tire compound and tread than the tire construction; which is why I liked the Potenzas that came with the MCS better than the Euforias' that came with the 128.

Bill

 

My wife noticed the improved ride before she got out of the tire store's parking lot!

A flat is still a flat unless your RFT's are also self sealing, most are not. So I added the Slime Spair kit even before we traded the RFT's in on Michelins. (Which also increased hand calc MPG from 33 MPG on freeway trips to 36.5 MPG).