Hi all

I have been running on different sized front and rear tyres on my 4x4, 55 profile on rear and slightly over inflated fronts with a profile of 50, whilst awaiting delivery of new tyres.

Have covered about 100 miles with this configuration.

Today whilst returning home the front nearside(I think) drive started a regular clonking noise whilst coasting, not there on serious driving, haven't had time to investigate yet, tomorrow's job, I think it might be the driveshaft or the cv joint.

Any suggestions out there?

Try disconnecting the wiring connector from the Haldex controller and see if the clonking stops.

It should not be engaged during coasting anyway but worth doing the check.

My rationale is that if there is any transmission wind up due to the tyre delta circumference then one front wheel is going to scrub or hop, the passenger one carrying less load.

An alternative way to "turn off" the Haldex is to look in the manual for a fuse labeled "all wheel drive" and remove it 😃. For whatever it's worth, never run with different sized tyres on any of the corners of a 4x4 car that uses a Haldex. There are slight tolerances that the Haldex will ignore such as differences in tyre wear, but beyond that it'll stay permanently stay engaged because it thinks it's detecting wheel slip due to the rotational differences. This will then cause it to be engaged at higher speeds for extended periods of time which will do it no favours at all. 😃

My suggestion to anyone having to run a different size of tyre for whatever reason is to remove the Haldex fuse while doing so. The car will run in front wheel drive and probably flash all sorts of warnings at you due to alot of safety systems that use the Haldex. Just make sure to drive extra careful as not only will you not have various safety systems, but in an event of a loss of control accident, I'm not sure what an insurers point of view would be if they saw the Haldex fuse in the cup holder 😂.

(Try disconnecting the wiring connector from the Haldex controller and see if the clonking stops.)

Ok, to disconnect the haldex, is the connector at the rear. ie on the haldex unit or somewhere else?

The problem appears to be mechanical, after removal of the Haldex fuse the clonk persisted -- where now?

Are you sure the correct fuse was removed? If it was the dashboard should have lit up like fault code city.

The fuse layout in the manuals for RHD cars are usually wrong (reversed) but as FrenchTone has I presume a LHD car his would be correct.

No, t's a RHD but the fuse board is upside down in the end of the dash panel, took out fuse 16 a 10amp red job, ESC lit up on dash after initial checks, VCDS also showed a problem, replaced fuse and back to normal!

Hence my assumption it is a mech prob.

I will take the car down to the soft surfaced car park and give the accelerator some welly, done this before to prove the 4 wheel drive is working.

Ok, just done the initial take up, and yes 4 x small piles of disturbed parking surface so I assume the the haldex etc is working as it should!

My only other thoughts are -- is it the antivibration joints on the front / rear prop shaft? I cannot look under at the moment, my trolley jack has lost some oil, and, a buddy will eventually arrive with some EP90, my usual top up oil! Then I'll have a look under the car at the shaft etc.

The car is 11 years old with 100k on the clock, the rear joint was replaced about 3 - 4 years ago.

Edited 1 April, 20251 yr by Frenchtone

The noise does sound like it could be a driveshaft. You don't need much excess play to create noises, you may not feel any obvious play when turning the road wheel with the corner jacked up. Noise will often change character with cornering and acceleration/braking as the torque and deflection angle change.

The mismatched tyres may be just a coincidence. Although clearly not ideal for long term driving, the system should be able to accommodate a small amount of speed mismatch front to rear.

As previously no noise when the engine is 'pulling' only whencoating or rolling at a non changing speed

I now have the tyres, they will be fitted in the near future, as above I will check the propshaft tomorrow!

Have you got a parking wheel clamp on that side?😁😁😉

Got the clamp off and went up to the village, no noise so must have been that -- seriously though did go up the village and yes it was silent, cannot look under the car my trolley jack is bust, a chum has promised a pair of ramps for the weekend!

Ok found my problem, a loose front (uk) n/s wheel, changed by local Profil tyre depot as I have another set of wheels, 2 of which are being reshod by said outfit!

A lesson to be learned here, after work like above I will now always check the wheel nuts,

And , an interesting conversation with the depot manager to be had monday when I collect the 2 wheels.

It's quite frightening when the above situation arises and the possible consequences that could have arisen!!

44 minutes ago, Frenchtone said:

Ok found my problem, a loose front (uk) n/s wheel, changed by local Profil tyre depot as I have another set of wheels, 2 of which are being reshod by said outfit!

A lesson to be learned here, after work like above I will now always check the wheel nuts,

And , an interesting conversation with the depot manager to be had monday when I collect the 2 wheels.

It's quite frightening when the above situation arises and the possible consequences that could have arisen!!

I've seen prominent signs in some workshop mandating all wheel fixings being rechecked by leading hand mechanic before vehicle is released. Perhaps more should do this.

Perhaps different rules here a la frog!

It is possible that it's not the fault of the tyre place - it is recommended to check the torque of all bolts/nuts 100 miles or so after a change. That said, I've never had one loosen off, although my place does use a torque wrench and not an ugga dugga.

The Haldex system can be quite sensitive - it's recommended to use four tyres of the same tyre with the same wear, as anything else can cause it to turn into a Torsen system.