2010 35i sudden loss of power, code 5A53

[Pbondar]

What size tyres have you currently got fitted?

Bridgestone Ptonenza RE050A1 ... 35s on the front and 40s on the rear.

What are the widths?

Assuming they are either square or assymetric and you really have 40s on the back and 35s on the front then the rolling circumference difference front and rear is either 4% or 7%..the limit lies around 1.5% ish..in which case the DCS unit will have a melt down as your sizes are outside its parameters..

I had a not dissimilar thing when I intentionally provoked the car with all sorts of serious warnings (that dissappeared on re-start) with a 2.5% error based on an incorrect front tyre size..

[CFSD]

What size tyres have you currently got fitted?

Bridgestone Ptonenza RE050A1 ... 35s on the front and 40s on the rear.

What are the widths?

Assuming they are either square or assymetric and you really have 40s on the back and 35s on the front then the rolling circumference difference front and rear is either 4% or 7%..the limit lies around 1.5% ish..in which case the DCS unit will have a melt down as your sizes are outside its parameters..

I had a not dissimilar thing when I intentionally provoked the car with all sorts of serious warnings (that dissappeared on re-start) with a 2.5% error based on an incorrect front tyre size..

They are 255 r18s... so 255/35 and 255/40. Don't know why I wrote it like I did...
They've been on the car since I bought it (thanks to covid). But thanks for the info, I'll definitely look into it.

[Pbondar]

Well it’s a 4% error so once you go to that territory you are on your own with regard to most DCS related functions…

[CFSD]

Well it’s a 4% error so once you go to that territory you are on your own with regard to most DCS related functions…

So I should be matching front and back (ideally)?
Like I said the tyres were on the car when I bought it so changing them isn't an issue for me.

[Pbondar]

Well it’s a 4% error so once you go to that territory you are on your own with regard to most DCS related functions…

So I should be matching front and back (ideally)?
Like I said the tyres were on the car when I bought it so changing them isn't an issue for me.

There AFAIK has not been published a specific figure but 1.5% is usually regarded as the maximum variation..

So yes external tyre circumference should be the same..

Who did the re-map…did you get a dyno run?

[CFSD]

Who did the re-map…did you get a dyno run?

It was done by a place in Warrington, DC Remapping. Full dyno custom tune.
That was over a year ago now and until this strange event the car has been faultless.
Since having it checked over the car seems perfectly fine again. Very strange... I'm actually starting to think maybe I downshifted by mistake.

[Pbondar]

Usually these DCS ‘failures’ occur when you do something extreme and then the systems that are fed by the DCS throw a wobbly..I had one when I was doing extreme hard starts with traction off…it threw a wobbly similar to yours with no subsequent recorded issues..

In my case the tyre supplier had fitted an under profile front tyre which caused the difference in rolling circumstances..

[mcbutler]

Well it’s a 4% error so once you go to that territory you are on your own with regard to most DCS related functions…

So I should be matching front and back (ideally)?
Like I said the tyres were on the car when I bought it so changing them isn't an issue for me.

You just need to use what BMW fitted, its in your owners manual