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-   -   BMW X6 - reduce tyre size? (https://www.team-bhp.com/forum/tyre-alloy-wheel-section/104325-bmw-x6-reduce-tyre-size.html)

hi my cousin drives a may'11 X6 and is extremely unhappy with the ride of the car. he is currently using 255 50 R19 wheels. he has been told by the dealership that reducing the size to 18inch will improve the ride considerably. however, the person at bmw is not able to give him the size that he should opt for.

can someone give me the size that my cousin should buy.....

also, i check a number of international websites and found that the x6 always comes with 19in and above. is it that the wheels of some cars can't be downgraded?

1) I assume the X6 comes with "RunFlat" tyres. This is in part responsible for the harsh ride (due to the stiffer side-walls of the RFTs). Read more :
http://www.team-bhp.com/forum/techni...d-go-flat.html
http://www.team-bhp.com/forum/tyre-a...-new-ones.html

2) Scroll down to A Tyre Size Calculator at this tyre bible link
- Enter the current and new tyre sizes, and you can see how similar they are. A difference of 3-5% is okay. Naturally, the closer the match the better. A lot will depend on what tyres are available in 18" in the size range you want.

3) Going from 19" to 18" (even if no X6s come with 18") shouldn't be a problem, in my opinion.

cya
R

Maybe not. I'm not sure about the X6 but sometimes cars cannot accommodate smaller rims due to the size of the brakes.

Either way, if the car isn't driven on bad roads, the best bet is to switch to normal tubeless tyres, and buy a space saver spare, or a full size. The ride comfort should improve a fair amount.

People usually upsize on such cars not downsize! Tell you cousin to shift to tubeless tyres, he'll be amazed at the comfort!

True point, but in this case of a sada X6, 18" rims should still leave plenty of space for the brakes.

cya
R

Hi, I have a 2012 BMW X6 done about 27000 Kms and I want to change the Tyres which are currently 255/50R/19. I visited a Tyre Dealer who suggested me an Upgrade to 20 Inch wheels without compromising the shoulder size, He offered me the Pirelli 255/50R/20, It's a known fact that any X6 comes with different alloys on the front and Rear, the offset is slightly different, On the Front they are 10Jx20 ET40, on the rear they are 11Jx20 ET37, Even BMW recommends putting in wider Tyres at the rear, Now the Problem is... The wheels being offered by my Tyre guy are all same size all 4 of them 10Jx20 ET40, I want to know if installing these effects the ride quality or road grip or will have any warranty issues?? Thanks to all who had the time and patience to read this lengthy query.

I will not at all recommend you to upsize on X6 . I have 20 inchers with different width on front & rear but ride is horrible to say the least . Stance & Looks of these alloys is a different story although .

If you must change to size 20 , stick with original wheels from BMW - there can be problems later on including touching of Brake pads , might fit today but when you change new brake pads those might rub .This is from personal experience - I had to discard a set of 4 alloys for my 530 , you can get tires from outside though

PM me if you want to sell your old wheels ..

The X6 just came Back from 32000 Km Service and was recommended Tyres Change Very Soon... Also the wheels did have some cosmetic Damage.. Decided to change both... So got on the Internet and did some research (About 2 Hrs reading nearly 50 articles) which summed up to a conclusion that a change in Tyre size is Acceptable if the Variation in the Total Change is less than 4% So i went to a online Tyre size calculator website and keyed in the Current Size and the Size I want to Upgrade to.. which are 255 50R 19 to 275 45R 20... To my relief I found the Difference just to be 2.4% Please see Attached Images.. For Other Team BHPian's reference the website link is http://www.carbibles.com/tyre_bible_pg4.html

I really am Hoping to get some final Opinion regarding this from a Senior BHPian or Distinguished BHPian

Size 275/40- 20 in front & 315/35-20 is what BMW uses ( in case of upgrade ) . I have not tried size 275/45-20 but have heard from showroom guys that this might touch something when turned completely . Given me personal experience of about 33,000 Km with more than 3 sets of blown 20 inchers , will never suggest for this upgrade . If you have made up your mind for this , please ensure rims are original BMW .

To answer your original question, the correct logical size in 18" would be 255/55R18.
255 as a number is so close to the inch multiple of 25.4mm that any 255 profile tyre can always be resized by reducing 5% profile for every 1" increase in wheel size or conversely increased 5% for every 1" reduction in wheel size.
Other theoretical matches are:
235/60R18
285/50R18
315/45R18

An oversize to 275/45R20 should not be a problem either. Since you are hardly reducing the sidewall, I do not see any reason for a bad ride or broken wheels.

As for aftermarket wheels being more susceptible to damage than original BMW wheels, it depends entirely on what wheels you buy. Failing to observe what load the wheel is rated for is one of the key reasons of wheel failure in heavier cars like the X6. The only other reason is design (large rim lip, too then or too few spokes, etc.).

The widest TUV approved wheels for the X6 are 11" front with 295mm tyres & 12" rear with 335mm tyres. That said, the most common 20" upgrades measure 10" front & 11.5" rear.

A square setup of 275/45R20 all absolutely fine (typically with 10x20 ET37 wheels).

If you are really specific about checking fitment clearances the easiest way would be to measure the front wheel arch for ~815mm of clear space. The more accurate way is to see if you have at-least 12mm clearance when the 255/50R19 is turned.