There’s so much contradicting information online that I am very confused.
I need to buy 2 new tires for my BMW 228i xDrive.
I know they have to be exactly the same size, so I found the 225/40R18 Pirelly Cinturato P7 with 92 load index.
Now my issue is with the speed index and OE. Current ones are 92H and they have the OE star but when I look online, what’s available is either the 92H non-OE or 92V OE (and 92Y OE too).
Does it have to match so carefully? I managed to find 92H OE but it says RSC Mini where on the 92Y it says RSC BMW. Also, in one website they had 92H Mercedes OE.
Bottom line, how careful should I be? What really matters and what doesn’t?
Age/ tread wear on the existing tires, both front and rear? Which tire died, front or rear? Leased or owned?
The main reason you’re replacing in a pair is to limit wear on the differential- two different rolling diameters will cause that to spin even when driving in a straight line. If your current tires have minimal wear, however, you might get away with replacing just one. If you have less than 10k miles on the tires it’s likely worth taking a closer look.
If you have more wear than that and you’re replacing the pair put the new ones on the back (I don’t think the 228i uses staggered sizes). This is for handling and in particular hydroplaning- if the worn rears hydroplane first on a puddle you’re going for a loop. If all 4 tires are close to replacement (say within 25%) I’d personally replace them all to maintain handling balance- old tires lose grip vs new ones, so worn fronts and fresh rears will understeer badly- usually not dangerous but not fun either.
I’d get the OE BMW tire with the different (higher) speed rating- 92V.
OEs tune the tires for ride, noise, handling, etc. The differences are largest on staggered tire sizes- there they will specifically tune a front tire to turn and brake and a rear tire to accelerate, for example. Results can be terrible if you unwittingly put a tire designed for the front on the rear of a car (failures have occurred even when the ratings are correct). Because you’re dealing with a square setup you shouldn’t have those issues but the OE Mercedes tire may have been designed for a RWD car and the mini FWD, either of which will result in the tires being tuned differently. Getting the BMW spec even if it’s a higher speed rating will be your best bet to maintain handling balance- V (149 mph) might be slightly stiffer than H (130 mph) but I suspect you’ll be hard pressed to notice and you’ll be safe.
A final reason to stick with OE BMW may be buried in your lease paperwork if leased. Some manufactures (ie Porsche) will charge you if you return the car with non-OE tires on it.
Very much disagree- it’s very model specific. What examples?
If you’re talking older cars or models that have been around for a while there’s a big upgrade to be had using newer tech, ie PS2 to a PSS or 4S. If that type of upgrade isn’t available, however, I’ll generally take OE especially on performance oriented cars with tires tuned for them. This is especially true on things like 911s with rear weight bias/ light front ends. The OE Cup 2 305 on the rear of the GT3 are nearly an inch wider than standard 305s- put the “normal” ones on and the handling balance goes to hell.
Also realize that any “new” tire you bolt on feels like an instant upgrade, even if you’re replacing an identical tire. As the tread wears and rubber hardens tires lose grip, so comparing end of life OEs with beginning of life anything is challenging.
Did you check the tread depth yourself? I’d start there and if they’re all roughly the same depth and knowing that their at the end of life along with the flat tire, I’d replace all 4 and call it a day. No harm to the car and you know they will all match.
I didn’t check it myself. The service guy at the BMW dealership checked and recorded that the front tires were 5 3/4 (IIRC) and recommended to do tire rotation, but didn’t put any recommendation to replace them. It makes sense since it’s a FW-biased car (and he mentioned that too). I could also check at the Discount Tire nearby maybe but I am not sure if they’ll just try to sell, hence I am checking here first.
Makes sense
The annoying thing is, if I set it to 92H it changes the OE designation to MB, and when I select BMW, it’s selecting the 92V Discount Tire | Tires and Wheels for Sale | Online & In-Person. I don’t understand if that’s a bug or not. My BMW ones are 100% 92H. And on TireRack they only have the 92H with Mini OE designation. SimpleTire just puts a star, not noting what’s the OE designation.
That’s so complex.
I also assume it has to be the same brand and model (i.e. Pirelli Cinturato P7) if I only change 1 pair?
Fine to mix 92V and 92H in your case. You’re going to buy two new OEM BMW star spec 92V. You want to ask them to move the still good 92H rears to the front and put the new 92Vs in the rear (unless the old tires are very fresh for some reason). Make sense?
yep. Also just found out that my front tires are actually 92V and rear ones are 92H.
Could you explain the reason? I am curious. Since the AWD on the 228i is front biased, I would think the new ones should be there? or does it have to do more with balance?
Basically you never want the front to have more grip than the back. In an emergency maneuver if you slam the brakes, you’re already shifting weight to the front and taking it off the back.
Combined with relatively less grip at the back, you’re increasing the chances of an uncontrolled spin. Worst comes to worst, if you have to hit something you’d rather hit it head on while braking straight instead of sideways while spinning.
As mentioned above, balance is a factor but the biggest issue is hydroplaning.
The speed at which a tire hydroplanes is very sensitive to tread depth. If you have less tread depth in front they’ll hydroplane first if you hit a puddle. If you’re going around a corner this results in understeer, which is relatively safe and easy to control. More tread depth in front results in the opposite in the same situation: snap oversteer. The back coming around mid corner on a wet, slippery road is a very good way to have a very bad accident.
Right idea, but in the dry new vs old the difference in grip is relatively small, something like 5%, so you have 100% front/ 95% rear, resulting in a pretty minor difference in handling balance similar to adjusting a sway bar. Yes it makes a car pointier but in a way that’s likely controllable. Add rain and hydroplaning, on the other hand, and grip on one end can effectively drop to zero- you could be at 80% front- 0% rear as long as the puddle lasts, something nearly impossible to control.
Got new tires for my m340, the stock tires were 95H xl, the new ones are 91V. Not concerned with the speed rating, but is it a big deal the load index went down? The difference is a couple hundred pounds.
225/45R18? Recommended tire pressure is 35/ 39 psi, or?
If the above is correct it’s certainly not great, and most installers will not (technically not supposed to) mount the tires if you bring in the car as opposed to the rims. XL indicated that the tire is rated for inflation above 36 psi- if the inflation pressures above are correct you’d be above what the tires are designed for when properly inflated in the rear as well as over the load limit. So the obvious advice is to return them…
What could happen if you mounted them? Let’s say you lived in Germany, mounted these on the rear, fully loaded the car to the maximum weight rating and then hit the autobahn for a 60 minute blast between Bochum and Frankfurt. The sidewalls would be flexing too much every rotation due to the load, they would overheat and there’s good chance you wouldn’t make it to your destination due to a high speed blowout. That’s the design case for tire speed and load ratings, and it’s something most Americans will never experience.
What Americans will experience: the lower load rated tires will have softer sidewalls and will flex differently in corners, altering handling balance. You also risk pinch flats if you hit a pothole, and if you return the car on lease you may get charged for tires. If you never approach the load limits of the car, live in an area with good roads and don’t explore the limits of the car these might not be deal breakers, so if you can’t return them (or if my estimated numbers at the start of this post are off) you might knowingly “break the rules” and mount the tires even though the sound advice is not to.
This is correct, would have been nice for the tire shop to point out my car required XL tires and not the ones I picked. I was so focused on the tire/size/reviews I neglected the load rating. The tires I purchased are continentals and they do have a 60 day guarantee and confirmed they would swap but now I need to find a new continental with correct specs and that will be aggressive enough for the car. Thanks for the input.
