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Discussion Starter · #1 ·
I know the older style Haldex controllers were sensitive to difference in circumference. The spare tire in the car is 125/80 R17, and the stock tires are 235/40 R19. The difference in circumference is 5%.

Is that an acceptable difference for the newer gen Haldex?

If not - if you pull fuse 29 in box B ("All Wheel Drive control module") - does that disable haldex and AWD (at which point you can put the spare on the rear and drive without worries)? That is the trick on our older V70R (fuse 17).

Thank you in advance!
 

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Haldex compensates up to 4% difference so your spare tire comes quite close but if you want to play it safe (depending how long distance you need to drive with that spare tire) then it's better to pull the fuse.
 

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Haldex compensates up to 4% difference so your spare tire comes quite close but if you want to play it safe (depending how long distance you need to drive with that spare tire) then it's better to pull the fuse.
Where did you get the 4% number from? The difference can be much greater than that and not cause any problems since the electronic clutches were added in the early 2000s. the only cars that had issues with a uneven tire were the viscous systems which are long gone. No need to pull a fuse on newer models. Ever.
 

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Where did you get the 4% number from?
Directly from Haldex. Someone once asked them and here's the reply;

Haldex wrote:
Hi Franz,
Yes, we do compensate for tiresizes up to 4%. This since we wread the
wheelspeed and the driveshaft and can understand if you have a minispare,
weared down tires or different sizes.
Best Regards,
Mats Johansson
Haldex Traction AB
Detroit
 

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If the tire size is too far off, you don't need to pull the fuse.

The system will disable itself.
 

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If the tire size is too far off, you don't need to pull the fuse.

The system will disable itself.
True, at some point it will disable itself to prevent overheating (<- correct me if I'm wrong?) but anyway why risk it?
 

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Directly from Haldex. Someone once asked them and here's the reply;

Haldex wrote:
Hi Franz,
Yes, we do compensate for tiresizes up to 4%. This since we wread the
wheelspeed and the driveshaft and can understand if you have a minispare,
weared down tires or different sizes.
Best Regards,
Mats Johansson
Haldex Traction AB
Detroit
I think we are talking about two different things here.....the % at which the AWD functions fully at 100% capacity, and the % at which damage will occur. 4% may be whats needed for the system to function as designed, however larger % differences will not damage the system (however the AWD may not function as designed). Ive seen in the service dept may tire size variations greater than 4% first hand.....never had any damage done on a non-viscous system.
 

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True, at some point it will disable itself to prevent overheating (<- correct me if I'm wrong?) but anyway why risk it?
The system constantly monitors the difference in the rate of rotation of all four wheels as well as the steering angle.

It can detect an offset almost immediately and self-protects to prevent overheating even if it doesn't disable based up on this alone.

You might as well just not drive your car at all, because you risk wear and tear on every single part every time you drive.
 

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The last time I used the spare (rear), when going beyond 30 mph, the car sounded like the axle was going to fall off. I checked, and the tire shopped checked to make sure everything was on correctly and lugs tightened. So I too am interested in which fuse to pull.
 

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The last time I used the spare (rear), when going beyond 30 mph, the car sounded like the axle was going to fall off. I checked, and the tire shopped checked to make sure everything was on correctly and lugs tightened. So I too am interested in which fuse to pull.
Fuse 29 from the box A under the glove compartment.
 

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If I am doing the math right, the spare (20.9" Diameter) is about a 5.5" difference in height compared to the 19" Wheels with the Sport Suspension (26.4" Diameter).

I don't think disconnecting the fuse will make a difference in that sound, but if you find out please let us know.
 

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Discussion Starter · #13 · (Edited)
Fuse 29 from the box A under the glove compartment.
Thanks! The description is the exact same wording used ("All Wheel Drive control module") as for for the older. V70R, car.
Of course it means you have to use the spare on the rear axle. Which is a pain if you have front axle flat....

I do thin you meant to say Box B by the way. Fuse 29 in Box A is different.
 
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