Bmw x1 xdrive thud

[Mylesx1]

Hi I've got an x1 xdrive and when coming to a stop there's a thud just before it stops, now it doesn't do it all the time seems to when doing a long journey. It only does it when coming to a stop in 1st or 2nd gear, hope someone can help i have no idea. The car drives great no clutch issues gears are spot on and engine pulls well so abit lost anyone have any ideas

[X5Sport]

Front or rear?  Could be suspension bushes wearing out.  You don't say how old/which version you have.

Oh and  

[Mylesx1]

It feels like the front oh its a 2012 m sport model e84, it feels as if you've banged it into gear but the gearbox feels completely normal no slip or stiff gear changes, its very smooth

[Horizon]

[quote="Mylesx1"]
Hi I've got an x1 xdrive and when coming to a stop there's a thud just before it stops, now it doesn't do it all the time seems to when doing a long journey. It only does it when coming to a stop in 1st or 2nd gear, hope someone can help i have no idea. The car drives great no clutch issues gears are spot on and engine pulls well so abit lost anyone have any ideas
[/quote]
You mentioned clutch so it sounds like you have a manual, or are you referring to an automatic gearbox?

[Mylesx1]

Yeh its a manual it only happens when your coming to a stop and in 1st or 2nd gear, it feels as if the abs has kicked in for s split second but there's no lights that flag up on the dash board

[Horizon]

[quote="Mylesx1"]
Yeh its a manual it only happens when your coming to a stop and in 1st or 2nd gear, it feels as if the abs has kicked in for s split second but there's no lights that flag up on the dash board
[/quote]

When it does it again, or after a long journey, or a spirited heavy braking drive, feel the heat of the wheels / front hubs. I had a sticking brake calliper that was more obvious after longer journeys, or if I had been using the brakes to slow the car from motorway speeds.
I think the heat generated in the brakes was causing the calliper piston to expand and over brake that certain wheel.
Hope you get to the bottom of the problem

[Mylesx1]

Thanks i will do, just haven't got a clue people mention tyres being different depths having an impact on the diff and it playing catch up and I don't mind spending the money on new ones if its gonna fix it my tyres I've got now have 6.5 mm on the front and 4.5 mm on the back but don't fancy paying £500 on a new set for no fix

[X5Sport]

The front/rear circumferences need to be with 1.5% max.  More than that increases the likelihood of issues, especially on staggered setups.

[Horizon]

[quote="X5Sport"]
The front/rear circumferences need to be with 1.5% max.  More than that increases the likelihood of issues, especially on staggered setups.
[/quote]
Mine had a lurch, when stopping at certain speeds, once I changed the tyres all was well

[Mylesx1]

I've read alot about people mentioning tyres, do you think my problem is mine I've noticed that I've got 225/45r18 with 6.5mm on the front and 255/40r18 with 4.5mm on the back

[Horizon]

Are the tyres the originals? Are they all the same manufacturer? Different makes can be a mile out when comparing circumferences.
Look on real OEM and put your VIN in, it will tell you what width rims you have fitted to the car.
Tour may be able to fit the same size make tyres all round without needing to go * marked.
I had 9j on the rear and 8.5 J on the front, so was able to fit 255's all round as they are made to go on aether size rim. So you can save a packet on a full set, knowing  it's kind on the transmission as well as your pocket.

[Mylesx1]

No there not original tyres but after research they are the right sizes which i find strange when everyone mentions tyres are so important on the xdrive models for the same rolling road circumference, having 45 on the front and 40 on the back means the tyres are smaller on the back  straight away so surely that puts the rolling off right from the start, think the only way gonna get to the bottom of this is at bmw just hope they can get the car to do the fault because it doesn't always do it and got a feeling they'll just say there's no fault when I know there's definitely something a miss

[X5Sport]

The figure is the sidewall height expressed as a percentage of the tread width.  You rear tyres are 30mm wider so have a different sidewall profile - 40% instead of 45%.  It is that height that causes the issue. '*' marked tyres have the tread depth & circumference matched to maintain the correct figures.  Non '*' marked don't and can have a very different circumference as a result.  At least one member measured his tyres and found more than 30mm difference.  That caused transmission wind up.  Fortunately the issue was caught before any damage was done.

[Mylesx1]

Surely if you had a matching set tho that wouldn't make a difference, mine aren't original tyres but are all the same tyre

[Horizon]

If there not star marked, even the same brand , doesn't mean the different
profiles  are even close to compatable to star marked tyres.
This may not be your problem, but  worth being informed by others less fortunate.