DONT DO WHAT I DID

[omodos]

Ok, just some advice that of course I didn't follow

I am 235/65 r17 all round, replaced 2 fronts that were worn with 2 identical size but different brand and tread style to rears, so running part worn identical rear tires on rear axle, and identical part worn on front axle-but rear to front different brand and treadwise (size seemed the same)

1. driving off after this change, felt like i was sort of either running noisy treads / tires or akin to driving on a cobbled road, after 5 mins noise was gone.
2. Then noticed at 1500rpm on inclines and at a low speed what can only be describe as shudder akin to going over a bit of non smooth tarmac.so was hard to tell at first, if this was the road surface or not until i found a smooth incline to test. The shudder was there.
3.Noticed it also in the low rev range as revved dropped down when I was coming to traffic lights or slow city driving.

This has been like this for the last 3 days, and only yesterday did i do some thorough testing to replicate groans shudders

SO today i replaced all 4 with identical tires tread make (on advice of many here thanks) did 1 hour of testing, normal driving, highway too, but especially up those inclines AND noise/shudder is gone.

So don't do what I did.....no idea what damage I caused but something was not right with non identical tires..the car just didnt like it. And apologies to all those that I annoyed with repeated posts, i tend to obsess alas.

[80stech]

Good to hear and Good for you for not trying to get rid of the shudder by changing the transfer case fluid Maybe update your other threads.

That being said,
If your transfer case fluid is due for changing it might be a good time to change it, but only with the proper BMW fluid and reset the adaptations.

[Clavurion]

Originally Posted by 80stech

If your transfer case fluid is due for changing it might be a good time to change it, but only with the proper BMW fluid and reset the adaptations.

In this case I would change the fluid anyways. And like said with BMW DTF 1 fluid.

[andrewwynn]

Did you ever measure your rolling circumference? It would be helpful feedback how different was enough to be a problem.

[cn90]

Tread DEPTH is what matters. For AWD vehicles, if you replace only 1-2 tire(s), as long as the depth is the same as the existing tires, you *should* be fine.

[crystalworks]

Originally Posted by Clavurion

In this case I would change the fluid anyways. And like said with BMW DTF 1 fluid.

I believe that's made by Shell. S-tec sounds familiar. That's what I put in our transfer cases. Part #OIL0005 (BMW# 83222409710). Not cheap. But much cheaper than a transfer case.

Never had an experience exceeding the 1% tolerance through wear on an X drive vehicle. And we've had 5 of them now. As Andrew said, pictures and measurements would be helpful.

[omodos]

Originally Posted by andrewwynn

Did you ever measure your rolling circumference? It would be helpful feedback how different was enough to be a problem.

Andrew sorry I REALLY should have but was so stressed as you can see by the plethora of posts that I did not and wanted asap to be put out of my miserya and see if reverting back to an identical set of tires on all 4 ends I would be back to normal...have to be frank looking at replacement fronts I put on they did have perhaps 1mm of more tread than rears....but ok this is not what you asked....to be frank wont risk it going forward. This was the first time I did this.

[omodos]

Originally Posted by crystalworks

I believe that's made by Shell. S-tec sounds familiar. That's what I put in our transfer cases. Part #OIL0005 (BMW# 83222409710). Not cheap. But much cheaper than a transfer case.

Never had an experience exceeding the 1% tolerance through wear on an X drive vehicle. And we've had 5 of them now. As Andrew said, pictures and measurements would be helpful.

Won't suck on this post too much but reason for not thinking too much bout putting a different set of brand/reads up front was priort to this, i saw tread depth from front to rear was noticeable..easily more than 3mm difference...so with that logic thought putting on front albeit different brand tread I would be ok. As you say though rolling circum may have differed...but for sure this change caused the shudder/rumble....that went away when i replaced all 4 ends with same ones.

[Homerlovesbeer]

I still think that having this issue simply due to worn tyres on one end is truly bizarre!

A diff is supposed to allow one side/end to spin faster than the other so why is this such a drama?

[andrewwynn]

The problem is when it feeds erroneous data into the abs computer.

It will make the computer think some tires are on ice becusse they are turning at a different speed.