Afternoon,
I am new to the BMW world. Unfortunately not having a great start. I bought a used BMW X3 2015 Xdrive d 2.0 several months ago. 3 weeks ago I managed to get nails in both front tyres (Run flats) once at the garage it was pointed out to me that one of the rear tyres was at the minimum so I had all 4 tyres replaced with non flat-runs. a day later I noticed the car was hesitating when pushing the accelerator firmly from around 10 or 15mph. It is hard to explain and I would say its subtle but its there (I notice it more when the car has warmed up, (which would also men the tyres would expand). The AA test drove the car and put the diagnostics machine on and it came back with a Lambda sensor error. Though the AA mechanic said he didn't believe this to be the issue and suggested I take it back to the tyre garage to have them check the suspension/cambers etc.. as I had the wheel alignment carried out when the tyres where changed. I know you could say that its the tyres, but again i might not have neccessarly noticed the hesitation prior to the tyres being changed?
So i took it back and they checked everything and all was perfectly fine. I then took the car to garage to have the lambda sensor replaced which they done and the problem is still there. I have looked online and there is talk of wheel radius etc.. but I have changed all 4 tyres, the only thing being is they aren't run flats, can this really be an issue or could i be facing bigger problems. Hope not as already put £1000 into the car.
Dimensions:
OLD TYRES - 245/45R19 98Y & 275/40R19 101Y , NEW TYRES 245/45 ZR19 102Y XL & 275/40 ZR19 105Y XL
Any help would be much appreciated
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Hesitation when applying accelerator
Re: Hesitation when applying accelerator
Hello and 
The only differences with the tyre sizes are they are non-RFT and have a better weight rating, neither of which should make any difference.
What can make a difference is whether or not the circumference of the tyres varies. BMW (and others) use tyres homologated for them and that are matched so the overall out diameter is the same. This is important because of the different sizes on the axles. The tolerance is approx 1.5%.
Some - not all - tyre manufacturers are more generous than others with their tread depth and size tolerances and this can lead to transmission wind-up. A report from a few years back had one owner discovering that the circumference difference between the axles was in that case 32mm (per revolution) and this was causing an issue. Fitting BMW Approved rubber (marked with a ‘*’ on the sidewall) reduces the risk. On that occasion the owner switched to the ‘correct’ tyres and no more problem. It might not be the case for you, but worth checking just in case. There doesn’t seem to be any hard and fast rule about what tyres are good and bad. People have fitted cheap tyres with no issue, others have broken transmissions and the same applies with premium tyres. It is much rarer for ‘approved’ tyres to have trouble is all that can be said. It really shouldn’t make a difference but some cars just seem to be really sensitive to tyres.
Tyre pressures are also important as lower pressure than spec leads to tyres squatting down so changing their characteristics.
If it started as soon as you fitted the replacement tyres then there is either a coincidence, or a connection. Check the pressures carefully as some tyre places aren’t very good at getting it right. I had a set of tyres changed recently and had 0.5bar/7lbs differences between tyres!
All this being said it doesn’t sound like a tyre issue because you are only just rolling and accelerating, therefore it would suggest engine related rather than drive.
The only differences with the tyre sizes are they are non-RFT and have a better weight rating, neither of which should make any difference.
What can make a difference is whether or not the circumference of the tyres varies. BMW (and others) use tyres homologated for them and that are matched so the overall out diameter is the same. This is important because of the different sizes on the axles. The tolerance is approx 1.5%.
Some - not all - tyre manufacturers are more generous than others with their tread depth and size tolerances and this can lead to transmission wind-up. A report from a few years back had one owner discovering that the circumference difference between the axles was in that case 32mm (per revolution) and this was causing an issue. Fitting BMW Approved rubber (marked with a ‘*’ on the sidewall) reduces the risk. On that occasion the owner switched to the ‘correct’ tyres and no more problem. It might not be the case for you, but worth checking just in case. There doesn’t seem to be any hard and fast rule about what tyres are good and bad. People have fitted cheap tyres with no issue, others have broken transmissions and the same applies with premium tyres. It is much rarer for ‘approved’ tyres to have trouble is all that can be said. It really shouldn’t make a difference but some cars just seem to be really sensitive to tyres.
Tyre pressures are also important as lower pressure than spec leads to tyres squatting down so changing their characteristics.
If it started as soon as you fitted the replacement tyres then there is either a coincidence, or a connection. Check the pressures carefully as some tyre places aren’t very good at getting it right. I had a set of tyres changed recently and had 0.5bar/7lbs differences between tyres!
All this being said it doesn’t sound like a tyre issue because you are only just rolling and accelerating, therefore it would suggest engine related rather than drive.
Never anthropomorphise computers. They hate that.
Re: Hesitation when applying accelerator
Try driving it with the MAF unplugged.
I have seen this before but can't find it now but nothing to loose trying.
I have seen this before but can't find it now but nothing to loose trying.
Re: Hesitation when applying accelerator
Hi,
Thanks for the messages. I have since replaced the tyres fitted a couple of weeks back with OEM P-Zero Run Flats and yes this has actually resolved the issues. No more hesitation/jerking the vehicle driving as it should be.
Happy Driving
Thanks for the messages. I have since replaced the tyres fitted a couple of weeks back with OEM P-Zero Run Flats and yes this has actually resolved the issues. No more hesitation/jerking the vehicle driving as it should be.
Happy Driving
Re: Hesitation when applying accelerator
Thanks for posting this as it could prevent others from making a very expensive mistake.