X-3 Tire Replacement

Hi All -

Glad to have found this place!

I am wondering if we can use the winter tires we bought last year for a Pontiac Torrent on our 2009 X-3? The winter tires are: 235/60R17 and, as many of you know, the X-3 OEM ones are: 235/55R17.

We plan to mount the winter tires on new rims. I was wondering if the slightly higher aspect ratio would introduce any turning or related problems such as odometer/speedometer readings, etc.

Thanks.

Welcome to bimmerfest!

The original equipment 17-inch tires for BMW X3 are 235/55R-17, as on your vehicle, and -- in Europe -- 215/60R-17 for the base size. So 236/60R-17 is two sizes larger than the OE size.

That said, I think the X3 is rather forgiving of tire upsizing and it is possible that it would fit without rubbing or interfering with body or suspension/brake components.

On the speedometer/odometer issue, a 215/60R-17 tire normally will yield about 765-770 revolutions per mile. A 235/60R-17 will yield about 740-745. About 3% difference. Since German speedometers are normally several percent optimistic, your speedometer would probably be more accurate with the larger tire. And the odometer, normally quite accurate, would be a few percent off.

My conclusion: Possible, but not certain. A good tire/wheel store could probably tell you.

Originally Posted by LMC

Welcome to bimmerfest!

The original equipment 17-inch tires for BMW X3 are 235/55R-17, as on your vehicle, and -- in Europe -- 215/60R-17 for the base size. So 236/60R-17 is two sizes larger than the OE size.

That said, I think the X3 is rather forgiving of tire upsizing and it is possible that it would fit without rubbing or interfering with body or suspension/brake components.

On the speedometer/odometer issue, a 215/60R-17 tire normally will yield about 765-770 revolutions per mile. A 235/60R-17 will yield about 740-745. About 3% difference. Since German speedometers are normally several percent optimistic, your speedometer would probably be more accurate with the larger tire. And the odometer, normally quite accurate, would be a few percent off.

My conclusion: Possible, but not certain. A good tire/wheel store could probably tell you.

Thanks Larry. Actually, I found the answer to my question on line at: http://www.miata.net/garage/tirecalc.html

According the the calculations there, with the tire size replacement in question, there is a 3.4% difference (close to what you said.) So, if the speedometer reads 60 mph, you are actually traveling at 62 mph. The same in metric; 100 kph on the speedometer is actually 103.4.

I assume that is the same for the odometer – if, after the replacement tires are installed, I figure a 100 mile, or kilometers, distance on it means you actually traveled 103.4 miles or kilometers.

Hmmm...

Originally Posted by RMur

I assume that is the same for the odometer –

The odometer and speedometer are no longer intimately connected in the way they used to be.

Yes, the taller tires will make your speedometer more accurate - maybe dead on, but I believe will not affect your odometer at all.

I forget the measurement technology for the odometer, but you can understand that there was regulatory pressure on the industry to keep distance travelled independent of wheel/tire upgrades/downgrades.

The taller tires should also give you a softer ride - but maybe not that noticeable with hard-pack snow on the ground for most of the winter.

Originally Posted by Supercourse

....I forget the measurement technology for the odometer, but you can understand that there was regulatory pressure on the industry to keep distance travelled independent of wheel/tire upgrades/downgrades.

.

With all due respect, I'd like to know how that works, which is to say, I don't think that is possible. The vehicle doesn't know how big the tires are, so the odo has to be calibrated to a specific tire size. I suspect the industry was pressured just to make the odos simply more accurate and better calibrated. They were pretty bad back in cars I first drove, which came from the '50s. There used to be "speedometer check sections" so you see how bad your odo was.

If you have a GPS that tracks miles, suggest you do a before and after comparison, over some distance, in an area where you know there are no dropouts, with WAAS enabled if it's available and on your GPS, using the same route each time.

Originally Posted by dharmadoggie

With all due respect, I'd like to know how that works, which is to say, I don't think that is possible. The vehicle doesn't know how big the tires are, so the odo has to be calibrated to a specific tire size. I suspect the industry was pressured just to make the odos simply more accurate and better calibrated. They were pretty bad back in cars I first drove, which came from the '50s. There used to be "speedometer check sections" so you see how bad your odo was.

If you have a GPS that tracks miles, suggest you do a before and after comparison, over some distance, in an area where you know there are no dropouts, with WAAS enabled if it's available and on your GPS, using the same route each time.

Just a quick note regarding your GPS, I do a lot of mountaineering and I can guarantee you that GPS measurements are estimates at best... sometimes I travel up to 30meters (90feet) while sitting on top of a moutain having lunch =)

Originally Posted by dharmadoggie

The vehicle doesn't know how big the tires are, so the odo has to be calibrated to a specific tire size. I suspect the industry was pressured just to make the odos simply more accurate and better calibrated.

Yes, maybe I should retract my earlier comment that taller tires will not affect the odometer.

Lots of discussion of this in the general BMW forum.

General opinion is that BMW speedometers are maybe about 7% optimistic, but odometers are ony about 1% optimistic, with the O.E. tires/wheels.
That is just a calibration choice, and does not necessarily mean that the odometer is any less susceptible to a change in overall tire/wheel diameter.

In that case, if you buy a used X3 that originally had 17" wheels, which was early on updated to 19" wheels without a fully compensating reduction in tire aspect ratio, it may have done more miles than indicated by the odometer.
Not enough to be a big deal, but something to keep in mind.

Can someone point me to an official site (preferably in English) stating that 215/60R17 is acceptable for an X3? In the US, BMW only publishes 235/55R17 as standard for the X3 and certain tire installers (e.g., Costco) can be very adamant about following manufacturer's guidelines. The "they do this in Europe" won't help if I don't have paper to back that up. I went to BMW's UK site and for the current model they are putting 235/55's on all their X3's. Don't know where else to look.

I also assume that the 215/60's will fit on the same BMW base model wheels that the 235/55's come on?

Thanks!

I hear you on the tire installer wanting documentation!

Two places that come to mind:
(1) Owners manual/door jamb sticker: My '08 with sport package lists only 18- & 19-inch sizes on the door jamb and the owner's manual points me to the door jamb. You don't say what you've got but I presume you've already checked these. The ideal owner's manual would be an older one from Europe (the UK, say) but that would be troublesome to lay hands on.
(2) Service/parts information: The official BMW parts manual (the ETK) references tire size in the wheel section. You may access a copy of this at www.realoem.com/bmw and when I look there, I can find a reference to 215/60R-17 tires on an early X3. But if COSTCO is going to give you static, I'm not sure that a reference on such a web site will help. And a UK X3 owner's manual may not help either, the installer will fear that your American wheel hub is different even if it is not. Offhand I do not know of a place in the service manual (TIS) that references tires sizes. You can access the service database at www.bmwtis.com but you need to pay handsomely for the privilege.

As far as the suitable wheel for a 215/60R-17, in general yes it will fit. However, BMW made at least the base (style 109) alloy wheel in two different widths. 17x7 for a 215/60R-17 tires and 17x8 for a 235/55R-17 tire. The real answer here is to consult the TIRE manufacturer's official specs to see what the recommended range of rim widths is for the tire you are fitting.

I don't know what tires you're looking at, etc., but I think this will be such a hassle that you might consider giving in and going with a 235/55R-17.

Sorry I can't come up with a better answer.

Originally Posted by dbh1

Can someone point me to an official site (preferably in English) stating that 215/60R17 is acceptable for an X3? In the US, BMW only publishes 235/55R17 as standard for the X3 and certain tire installers (e.g., Costco) can be very adamant about following manufacturer's guidelines. The "they do this in Europe" won't help if I don't have paper to back that up. I went to BMW's UK site and for the current model they are putting 235/55's on all their X3's. Don't know where else to look.

I also assume that the 215/60's will fit on the same BMW base model wheels that the 235/55's come on?