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Discussion Starter · #1 ·
Since there is a single motor for each axle (front and rear) that drives both wheels per axle, how does the design allow for different wheel speeds? Is there a differential of some type?
 

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I tersting to see how the immediate torque impacts snow driving. VW may have an advantage with the slower torque ramp so that it behaves more like an ICE car.
 

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A lot of European cars use the ABS sensor as TPMS to measure differences in wheel rotation. To me that is BS, I hates that on my Audi and just as much on the P8. When I have real TPMS I would check actually pressure every time I started car. I am a tire nut as they used to say in the old Michelin commercials, “there is a lot ringing on your tires”. Think about the difference between serious issue could be 4 little contact patches no matter how many safety features your car has.
 

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I thought our tires had tpms sensors on …

Do we have evidence it does not have tpms?

Would letting a tire down slowly and monitoring after each air release prove one way or the other?
 

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Legally it has TPMS, there are 2 ways to implement TPMS, in the wheel/valve stem sensors that will do direct psi readout and then to leverage ABS sensors to determine if a wheel is spinning slower or faster than other wheels. If it had sensors int he wheels we would have a way to see the pressure in each tire. I do not liek the ABS method as it is not very precise. It also does not pick up slow leaks until they lose a bunch of pressure. This is why when you select the "store pressure" setting int he cat you are supposed to drive for 4-6 miles to give the car time to lean the rotational patterns of each wheel. They make all sorts of aftermarket options, valve caps with seniors, which I dislike and of course you can buy wheel sensors (tire have to be dismounted) to get direct readout, but then you need to find a place to mount and poser the readout display. I just tyr and get in the habit of at least once a month checking the tires on the T5 and P8 and topping them off.
 
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Legally it has TPMS, there are 2 ways to implement TPMS, in the wheel/valve stem sensors that will do direct psi readout and then to leverage ABS sensors to determine if a wheel is spinning slower or faster than other wheels. If it had sensors int he wheels we would have a way to see the pressure in each tire. I do not liek the ABS method as it is not very precise. It also does not pick up slow leaks until they lose a bunch of pressure. This is why when you select the "store pressure" setting int he cat you are supposed to drive for 4-6 miles to give the car time to lean the rotational patterns of each wheel. They make all sorts of aftermarket options, valve caps with seniors, which I dislike and of course you can buy wheel sensors (tire have to be dismounted) to get direct readout, but then you need to find a place to mount and poser the readout display. I just tyr and get in the habit of at least once a month checking the tires on the T5 and P8 and topping them off.
Thanks for the info. I am disappointed and surprised that Volvo would choose the cheaper less precise method. Is this the same for all Volvos?
 

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Thanks for the info. I am disappointed and surprised that Volvo would choose the cheaper less precise method. Is this the same for all Volvos?

It is not uncommon on European manufacturers. Part of me thinks it is becasue it is more common in Europe to put snow tires on this negates the need for 2 sets of sensors for people.
 

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You can see that the ABS sensors are accurate enough to see that one tire has a lower pressure than the others from this graph I created from monitoring the CAN bus on my old 2002 MINI Cooper.

You can see where I turned left (The right two tires went faster) then turned right (The left two tires went faster).

You can also (Well, maybe I can because I can zoom in) see where I drove over a stick and first the front tire has a bump where it goes faster while driving a little further in distance over the stick and then one car-length later the rear tire has a spike where it goes faster.

NO, it does not measure tire pressure, but I much prefer a system where I can:
  • Get a "feeling" for tire inflation. (It's really tire size consistency though.)
  • Can replace summer tires with winter tires inexpensively.
  • Can use a "Goop-filled" tire sealant in an emergency without f-ing up a US$250 TPMS sensor.
  • Don't have aftermarket masses threaded onto my tire stems wiggling them around continuously looking for a failure.

I'm not saying Volvo made the right decision for everyone in doing it this way, just that it was the right decision for ME.

(Here's a link to the slides from my CAN bus talk to a bunch of embedded-systems engineers. It might not make a lot of sense without me talking, but maybe...)

Rectangle Slope Purple Plot Organism
 

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Interesting info. The issue for me is "a feeling" is not very accurate. I want to know when 1 tires is down 2-3 psi. I have been burned by this in the past as a slow leaks takes much longer to show up in the ABS method that looking at the pressure. I get not wanting to have a second set of sensors, but many in the US don't run dedicated snow tires.
 

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On my 2016 xc90 I have the direct tpms sensors. I liked the time I got a flat as I was backing into my parking space at work. The car alerted me and when I got out I could hear the air hissing out. ABS would not have alerted me. I was able to arrange alternate transportation home that day. The winter wheels happen to be take offs that had sensors, so both summer and winter display actual pressure. My other cars have an orange tpms light on the dash all winter. Would the indirect (abs) tpms work with run flat tires?
 

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Discussion Starter · #19 ·
…yes as the owner of both Audi and Volvo I am aware of their tire pressure monitoring.

Volvo Ev motors max rpms are limited to14,000.
So there must be gearing involved. I have researched this out and have come up with very little… do you know if this is a lifetime service item? I’m so used to changing out rear differential fluid, this is all new!
 

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…yes as the owner of both Audi and Volvo I am aware of their tire pressure monitoring.



So there must be gearing involved. I have researched this out and have come up with very little… do you know if this is a lifetime service item? I’m so used to changing out rear differential fluid, this is all new!
I am pretty sure the system uses brake actuated LSD. It is electronic. There would not be mechanical differentials.
 
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