Tyre Pressure Sensors

[Nigelo2]

Went into preparation last week with a week 16 build date. I 've sourced a full size matching spare wheel in Germany but need to order the TPMS / valve assembly. Anyone happen to know the part number? TIA

[boff]

Ready to be flamed down here....

AFAIC Nigelo2 the wheels do not have a TPMS Assembly in them, as some clever chap worked out that TPMS could be delivered via the ABS????

[Leo-RS]

Ready to be flamed down here....

AFAIC Nigelo2 the wheels do not have a TPMS Assembly in them, as some clever chap worked out that TPMS could be delivered via the ABS????

That's incorrect and relevant to cars that do not have tyre pressure monitoring valves, all the ABS system does is take a 'snapshot' of the geometry and should a tyre have a puncture (or runs low) the geometry changes and the TPMS generates a warning that something has changed.

On the RS6, each tyre has a monitoring valve that lets you know the individual tyre pressures and tyre temps. Something an ABS TPMS cannot do.

[wildbore]

Why not just buy a space saver? It fits perfectly into the boot below the floor level and it is always on hand if you need it without filling up the rear load area.

[MikeFish]

Ready to be flamed down here....

AFAIC Nigelo2 the wheels do not have a TPMS Assembly in them, as some clever chap worked out that TPMS could be delivered via the ABS????

That's incorrect and relevant to cars that do not have tyre pressure monitoring valves, all the ABS system does is take a 'snapshot' of the geometry and should a tyre have a puncture (or runs low) the geometry changes and the TPMS generates a warning that something has changed.

On the RS6, each tyre has a monitoring valve that lets you know the individual tyre pressures and tyre temps. Something an ABS TPMS cannot do.

Yes the RS3 has the pseudo tpms system using abs sensors but the rs6 has proper sensors, which is nice bit more of a pain when changing wheels.

[stjames]

Who makes a 21" space saver and will it still fit underneath boot floor........??

[wildbore]

The space saver is a 20" wheel + tyre and is a genuine Audi part - there are always a few on eBay at any time (T145/60 R20). The tyre is 145 section temporary-use only and it fits perfectly in the boot well. If you have air suspension you just need to use some double-sided tape to move the suspension valve block out of the way. I popped one in the boot a few weeks ago and now I have a warm, fuzzy feeling about getting a puncture. Well, I am less worried about getting one, anyway.

[MikeFish]

Will it fit over the front calipers or is it for the rear only?

[IanH755]

It doesn't fit over the front calipers but the idea is to fit the space saver to the rear and move the rear tyre to the front if you ever get a front puncture

[boff]

call brake down. have a snooze.

[stjames]

Thanks for info, will talk to tame VAG dealer post haste.......!!

[Nigelo2]

Thanks for the TPMS clarification - much appreciated. Does anyone have a part number for the sensor/valve unit?

A space saver might be ok for very short distance emergency use but completely useless for me on my regular continental trips. As I wrote on another thread, the 145 60 R20 Space saver has a rolling radius that is substantially different to the standard tyres and well outside recommended parameters. This will quickly heat up the centre diff and maybe the reason Audi don't offer it. So there could be a warranty issue if you have diff failure due to using it.

Coincidentally a friend has just taken delivery of a 2015 Allroad that has an SS with a 195 50 R20 collapsible Vredstein which is still no good for me but very close to the standard rolling radius.

FYI, diameters as follows:
275 35 R20 = 700.5mm
285 30 R21 = 704.4mm

145 60 R20 = 682mm
195 50 R20 = 703mm

[wildbore]

You can change the 145 section tyre for a 165 section on the same spare wheel and it has an almost identical rolling radius to the 21" wheel. Rolling circumferences.
285/30 R21 = 2150
165 spare = 2167
145 spare = 2094

Only 17mm difference instead of 56mm. I thought about it but I will only ever use the spare to get me to a puncture repair centre.

As for travelling long distance or high speed, yes the temporary-use spare is not safe for fast or performance driving, but I reckon it would be fine at up to 80mph for a few hundred miles of gentle driving.

[MikeFish]

Alternatively, for Continental trips I'd be looking at a full size spare if you have space.

[amariyavhrist]

Tyre pressure monitoring system (TPMS)is one of the most important equipment of vehicles to monitor tires and avoid inconvenience.