[Priority 1]

Does anyone out there with X drive have any long term experience with Michelin Pilot Super Sport tires in 235/265 19"?

I'll save everyone the long story, but I put 10k miles on a 225/265 set because the specs show they match closer than 225/255 or 235/265. I had decreased fuel economy while using these tire sizes and eventually i had to replace the transfer case actuator assembly.

I'm tired of using my winter tires in the summer and I'm ready to buy new summer tires, but I don't want to waste money like last time. I'd love to know if the PSS 235/35R19 and 265/30R19 are safe for x drive (even though their posted specs say they are worse than stock sizes).

[gtaccord]

Yes. They will work great. That is the recommended size combination.

[X_Drive]

What tires were you running? I run ContiproContact 2* 245/275. I do have a dip on economy due to the larger overall tire diameter from stock, however haven't had an issue with the VTG to date and I am at the 1-1.5% range. (I guess knock on wood)

I also gained a tad of milage when I used the proper PSI for a 19" rim recommended in the manual. (39/46)

However to answer the question, I think many people have run the set up you mentioned w/o issues.

[ccraig13]

I just got the Pilot A/S 3 which are close to the performance of the PS2 but with much much higher tread life. I did lose MPGs as well, since my new wheels are wider that's more rubber on the road.

[Priority 1]

Originally Posted by gtaccord

Yes. They will work great. That is the recommended size combination.

How many miles do you have on yours?

Originally Posted by X_Drive

What tires were you running? I run ContiproContact 2* 245/275. I do have a dip on economy due to the larger overall tire diameter from stock, however haven't had an issue with the VTG to date and I am at the 1-1.5% range. (I guess knock on wood)

I also gained a tad of milage when I used the proper PSI for a 19" rim recommended in the manual. (39/46)

However to answer the question, I think many people have run the set up you mentioned w/o issues.

I have Michelin Pilot Super Sports 225/35R19 on 8x19 up front and 265/30R19 on 9x19 in the back. If you look at tirerack, or michelin's website you'll see that this setup is 2 revs per mile off and the diameters within 0.1". The same tires in 235/265 are 5 revs per mile off and 0.2" off in diameter. That's why I went with the odd pairing.

If you compare to say the continental extremecontact dw that same setup is 6 revs per mile off. In 235/265 these are only off by 3 revs per mile which is the same as stock.

I did ask michelin for recommended tire pressure, it made more sense than that pressure you quoted @ 39 and 46 from BMW. With wider tires I'd expect the pressure to drop since I'd assume the contact patch would be wider and therefore less pressure required to support the same load. I do wonder how much the pressure would effect this.

[X_Drive]

Sorry, those pressures were BMWs recommended pressures for sedan/touring. They are high, and would never run those on a track, however daily drive it's all good. BMW seemingly places this as the optimal mix of performance and efficiency for tires I would imagine.

[gtaccord]

I run 35/41 for tire pressures (pretty much what's right on the door tag plus a lb or two). Works great.

I wouldn't worry too much about individual manufacturer tire specs for diameter and revs. You could chase that all day and still not be 100% sure of what you have.

[Nonecure]

My door seal said 33/37, so I followed those pressures. The front tires wore out the outer edges. I looked in the owners manual (even know that is against my religion), and it has a nice table showing different wheel/tire options and pressures. I am now running 36/36 and think that is good for my setup. Basically higher pressure for heavier load (more people and luggage).

[cgrizzly888]

The pressure indicated on the door seal are for run-flat tires. I believe you need more pressure for non run-flats.

[Priority 1]

Just to get back on topic, so there are lots of members out there running 235/35R19 and 265/30R19 michelin pilot super sports? And no one has had any issues with decreased fuel economy, a clunk noise, binding sensation or slowing down without applying the brake when turning sharply at slow speeds, or transfer case actuator failure?

I just need to verify that those tires will work even though the manufacturer posted specs would indicate increased wear on the transfer case compared to stock 19" wheels and tires.

[335xs2dinan]

i run 235/35/19 front and 275/30/19 michelin pilot super sports without any issues

[Nonecure]

your 235/265 has a -0.86% difference front to back. Yes that is below the 1% magic number, but is very close and can be your issue. 235/275 is a better setup. I'm personally running 245/285 on my PSS.

[David1]

Originally Posted by cgrizzly888

The pressure indicated on the door seal are for run-flat tires. I believe you need more pressure for non run-flats.

Pressure is pressure and has no correlation to run flat or not.

[David1]

The stickier and wider the tire the lower your MPG. Wider also adds aero drag which is significant.

[Priority 1]

Originally Posted by Nonecure

your 235/265 has a -0.86% difference front to back. Yes that is below the 1% magic number, but is very close and can be your issue. 235/275 is a better setup. I'm personally running 245/285 on my PSS.

I can't count on math anymore because I selected tires that on paper work the best and they were completely off. Check out the math on 225/265 for PSS, and then explain why they gave me so many problems.

[Priority 1]

Originally Posted by David1

The stickier and wider the tire the lower your MPG. Wider also adds aero drag which is significant.

When the tire diameters are different the multiplate clutch packs in the transfer case are constantly wearing. Think of it as a central brake. One axle wants to spin faster than the other, but they are mechanically constrained to rotate at the same speed. So the axle that spins faster is slowed down and drags to an extent, and the clutch pack is worn to an extent. This is the kind of fuel economy loss i'm talking about. I bet the 1% or whatever is the deadzone where the sensors don't consider wheel speed differences to be from wheel slipping. Any diameter difference will result in wear and decreased fuel economy.

[Nonecure]

Your last post just further explained the problem you’re having. A front to rear difference greater than 1% will throw a code and be hard on the Xdrive system. Your 235/265 setup is almost at 1%. Not enough to through a code, but enough to cause extra wear on your clutches and other drive train components. The math does work and I run just fine on my Michelin Pilot Super Sports. I have not seen any issues or a drop in gas mileage, but my front/read difference is smaller than yours. BMW offers a staggered setup, but 225/255 has a 0.2% difference, not almost 0.9%. I get the same in town gas mileage with my 225/225 as I do with my 245/285. I'm sure highway mileage would be slightly reduced (in theory), but I haven't noticed. My daily commute to work (part highway and back roads) nets the same 20.4 mpg with either setup. I hope my rambling has helped.

[Priority 1]

Originally Posted by Nonecure

Your last post just further explained the problem you’re having. A front to rear difference greater than 1% will throw a code and be hard on the Xdrive system. Your 235/265 setup is almost at 1%. Not enough to through a code, but enough to cause extra wear on your clutches and other drive train components. The math does work and I run just fine on my Michelin Pilot Super Sports. I have not seen any issues or a drop in gas mileage, but my front/read difference is smaller than yours. BMW offers a staggered setup, but 225/255 has a 0.2% difference, not almost 0.9%. I get the same in town gas mileage with my 225/225 as I do with my 245/285. I'm sure highway mileage would be slightly reduced (in theory), but I haven't noticed. My daily commute to work (part highway and back roads) nets the same 20.4 mpg with either setup. I hope my rambling has helped.

Keep in mind, the tires that I have that gave me issues are 225/265. That's not a typo...two twenty five and two sixty five. I picked those because the standard pairs were off more than i was willing to try. But for all my efforts I still ran into the exact problem i was trying to avoid. So i skipped a whole season of summer tires just because i was upset and now i'm ready to give them a try again. I loved how the PSS rode and I'd love to get them again, so I'm asking if anyone has significant miles on PSS with a staggered setup i could mount on 8x19 and 9x19 wheels on xdrive.

I have a feeling the numbers michelin provided for diameter and revs/mile are wrong, or are not the only consideration when trying to avoid differences in rolling diameters.

[psubmw]

Bump...I'm looking forward to hearing an answer. I have 8.5x19" and 9.5x19" rims and was planning on using a similar setup with the Michelin PSS.

[gtaccord]

So I have a theory based on my experience.

Stock tire size:

F - 225/40-18 (637.2 mm dia)
R - 255/35-18 (635.7 mm dia)

Notice that the fronts are slightly larger than the rears

Common 19" size:

F - 235/35-19 (647.1 mm dia)
R - 265/30-19 (641.6 mm dia)

Notice once again that the fronts are larger than the rears. This is the sizing that I run with no problems so far. (20 k miles)

My winter setup:

225/40-18 (637.2 mm dia)
265/35-18 (642.7 mm dia)

Rears are larger than fronts. This is similar to the 225/265 19" setup (640.1 mm dia front vs 641.6 mm dia rear) that the OP has. With this setup I have a lot of surging at constant interstate speeds (60 + mph with cruise on) when under load (going up hills etC). The car still performs well and I have not had any issues with the TC so far (10k miles this winter on this setup). I even had the car on the dyno with these tires. But as soon as I went back to my summer setup the surging went away.

I theorize that the computer and awd system as a whole is setup with the consideration that the front rolling diameter is >= the rear (within reason on the > of course). This being a rear biased awd system (transfer case instead of center diff) the computer wants to see the front driveline turning at the same speed or less when compared to the rear. If you think about it, since the rear wheels can never be disengaged like in a car with a center diff, the TC clutch can only be used to slow down or speed up the front driveline using clutch slip in relation to the rear driveline. The front driveline can never be driven faster than 100% of the speed of the rear driveline. In normal driving (non slip conditions) the transfer case can easily attempt to turn the front driveline faster when using larger front tires(using rear driveline speed as a target) but it cannot make the front driveline constantly turn slower when using smaller front tires (tire speed vs driveline speed). So basically the smaller front tires cause the car to fight itself and will probably cause excessive tc wear.

This is why the 235/35 - 275/30 19" setup still works because the rolling diameters are basically exactly the same.

I would modify the typical advice and say that as long as the front tire diameter is >= the rear tire dia within 1% you will be good. I would avoid going with a setup where the rear tire dia is larger than the front. I am actually considering changing my winter setup because of the obvious drivability difference I am seeing.

Hope this helps.

[stashtrey]

What a pain in the ass. I've been running 235/40/18 front and 265/35/18 rear Congo Extreme DW. This was recommended by many people and more than one wheel vendor here.

Just got some new M359 Avant Garde 18 x 8.5/9.5 (pissed I made the mistake of not getting squared). Put the same tires in these rims. Car seeks fine but I was having some noise up front.... either wheel bearing on its way out or differential. Tore it apart this weekend and couldn't get my axle out.... put it all back together and now it sounds fine. The noise started immediately after I installed my KW V3 suspension.

Possible I didn't put it back together properly when I did the suspension? Super weird.

Sorry...off topic. Basically...I wish I had RWD as worrying about the drivetrain is such a headache.

I ordered (haven't paid yet) a set of PSS in 235/265 to replace my DW's. They don't make a 275/35/18 tire. Only option I can find is 225/40 and 255/35 or what I've got now.

Ugh. Sorry to thread Jack. Just commiserating with OP.

[stashtrey]

What the F? Now I see 275/35/18 PSS online. Perhaps Tire rack doesn't carry it? I could have sworn I couldn't find them in that size.

Totally littering the thread now. My bad!