XSeries-forum

Hi All. My first post (apart from the welcome section)

Have a 2003 x5 with the 3l Petrol engine.

It appears to have a fault, as when you accelerate under load. Ie. When overtaking or entering a motorway. The car changes down a gear then accelerates upto the Rev limiter then won’t change up unless you take your foot off the pedal slightly.

It dose this in any gear?

No fault codes register and a specialist updated the engine and gearbox ecu program but still the same fault. They also suggested changing the back tyres as they have a slight tread depth difference and are different brands (hardly noticeable)

But what are your thoughts before I buy a set of 285 tyres?

Could it be the pedal?

Thanks in advance

Pedal is only drive by wire and the changes are controlled by the box itself.  Not sure how the pedal might affect the shifting.  Almost sounds like a kick down issue?

Tyre types are important.  They should be the same brand and if a ‘staggered setup’ a ‘*’ marked type to prevent transmission damage to diffs or transfer box.  Tread depth should be within 1.5% front/rear but it is the overall circumference that really matters.  Large differences exist between (and with) brands and that could be upsetting something.

Any sign of unusual shift patterns at less aggressive throttle settings (eg around town) or problems in reverse?

Hi x5sport. Thanks for the reply

Ok sounds like I should buy 2 new rear tyres as they are different tread patten and brand. With a possible mismatched circumference.

Yes front and rear are staggered widths.

No other problems. Drives well. Apart from if you accelerate hard.

You could set off aggressively from a standing start, as if you are pulling out onto a busy road or acceleratorating onto a motorway and it won’t change upto the next gear unless you take your foot off the pedal slightly. Then it changes up.

Maybe the car is thinking it is going round a corner and therefor the computer won’t change up?

Surely the 03 X5 is still an all wheel drive rather than an X drive and has a simple epicyclic gear in the transfer case and no clutches. Even if the tyres are out of sync' this is absorbed by the epicyclic gear???

Hi henryx3. Yes this is what I thought to.
I am not convinced it is a tyre problem as it can happen in 1st gear as well as 4th so not speed related! But no codes to read off the ecu.
Is there a valve/sensor that controls the change up under load? Or could it be the maf?

whats ‘*’ marked mean in the post by X5 ?

He’s referring to star rated tyres, some manufacturers such as Porsche, BMW, Mercedes etc in conjunction with the tyre manufacturers have a special mark on the tyres that are specifically made to a tighter tolerance for that brand of car.

As a for instance, not all Michelin tyres will have the star rating for BMW, there are only a couple of different Michelin tyres that are BMW approved for the X5 out of their huge range of tyres.

If it ain’t got that star *, it is allegedly unsuitable for your BMW.

Some say poppycock - as long as they’re all the same it’s ok, some swear by it and say fitting tyres without the star will ruin your transmission.

For BMW, the tyres that meet the standard will have a 5 pointed star on them. This is because they are made in the bowels of hell using witchcraft and are untouched by human hand.

Personally I put star marked Michelin’s on mine, they were £800 but I thought it was worth it.

thanks, another mystery of this car cleared up,

i took daughters car for a puncture repair and was asking how much tyres for the X5 were, he was selling some Kumo brand at around £80 each which seemed reasonable.
Anyone heard of or used this brand ?

‘*’ marking means matched rolling radii between sizes especially important for staggered wheel setups.  It means that the circumference will be the same despite the different tyre tread width and profile height.  Unfortunately because the numbers produced are smaller the cost per tyre is higher.  BMW will also walk away from warranty claims about the transmission if non ‘*’ marked tyres are fitted.

Not having matched radii can mean a >30mm difference in the circumference between front and rear and that is per revolution.  This winds up the transmission and eventually results in either a destroyed diff or transfer box.  It seems to be a weakness with the xDrive system design - and poor engineering choices as this simply should not be necessary.  Grinding noises, or driveline whining and jerky drive at low speeds especially on full lock are a sure sign is about to break.

It’s a known problem for cars with staggered wheelsets - and no longer just with BMW.  Your car, your choice as they say.  It also occurs when only one axle set of tyres are replaced leaving the other axle set as well worn.  These cars should have their tyres changed as a full set.

You supplier is probably referring to Kumho?  Well known and a good tyre.  Whether they do a ‘*’ rated version I do not know.

Have you checked the gearbox oil level. These auto boxes need to be spot on. Make sure you do it properly and at the right temperature if you haven't got the kit to do it properly take it to someone who does. Google how to do it properly and then ask questions of the person who's doing it. Always remember, if he gets annoyed at your questions then he probably isn't clued up and will do it wrong, tell you it's ok, you buy new box because the old on needed 1/2 ltr of oil. Not clued up on the right procedure for your GM box but someone on here will know. Cheapest option first.

Ok thanks for the replies, I did not know about the * marked tyres but will check what is on the car and measure the rolling radius of each tyre.

Before I go to the expense of changing them has anyone had the change up problem just from incorrect tyres being fitted.

If I had another set of wheels I would change them over to see if it made a difference.

Have you tried the reset adaptations thing yet on the gearbox.
I think you put the ignition on but not start car then hold the pedal to the floor for thirty seconds.
Do a google search in case i have it wrong.

Hi All, just thought I would give you a update.

Checked gearbox level and ok.

The reset gearbox adaptations I had already done so I though I would take off the rear two tyres as they had different brands each side.

When placed side by side on a level surface there is a 11mm difference in height. So the rolling radius must be completely different each side.

Will replace the rears and see if this is the main cause.