Spare wheel Do or Don't

[JTQ]

Speed-derived systems are quite sensitive - as I discovered some years ago when I fitted slightly larger tyres on the rear of my Astra as it fooled the ABS system into thinking the front wheels were spinning!

Whilst I have never mismatched my tyres, my experience with VW's speed derived warning system has been it did not pick up a 3 psi drop, that is 9% pressure loss. An amount I think is too high.

 

[otherclive]

On the subject of tyre pressures what gauge is used and how do you know its accuracy? I have three gauges and at a nominal 33psi there’s a variation of 3psi across the nominal. The gauges on my three types of inflator ( track pump, foot pump and powered) are rubbish. So I use just one gauge, a PCL digital, and keep an eye on tread wear. In the glove box of the second car is a PCL pencil gauge that in the event of a TPMS alert can be used on warm tyres to check the equality of pressure across an axle.


PCL digital

 

[RogerL]

On the subject of tyre pressures what gauge is used and how do you know its accuracy? I have three gauges and at a nominal 33psi there’s a variation of 3psi across the nominal. The gauges on my three types of inflator ( track pump, foot pump and powered) are rubbish. So I use just one gauge, a PCL digital, and keep an eye on tread wear. In the glove box of the second car is a PCL pencil gauge that in the event of a TPMS alert can be used on warm tyres to check the equality of pressure across an axle.


PCL digital

I recall a test some years back where traditional "pencil" gauges were the most accurate - with garage airline gauges the least accurate.

When I want to do a pressure check I pump the tyres up a bit the night before and then adjust them using a pencil gauge first thing in a morning, so the tyres are cold and not affected by radiant heat from the sun - it's the only way I've found to get consistent readings - the car's TPMS does then display the actual pressures of each individual tyre during a journey, which of course rise naturally

 

[otherclive]

I recall a test some years back where traditional "pencil" gauges were the most accurate - with garage airline gauges the least accurate.

When I want to do a pressure check I pump the tyres up a bit the night before and then adjust them using a pencil gauge first thing in a morning, so the tyres are cold and not affected by radiant heat from the sun - it's the only way I've found to get consistent readings - the car's TPMS does then display the actual pressures of each individual tyre during a journey, which of course rise naturally

Likewise I always check or adjust my tyre pressures when they are cool and no sun. Where we live that’s early evening in summer. Today it could be anytime. 🙁

 

[JTQ]

The digital ones, if this LINK test is itself reliable, seem to be good on accuracy.

If looking at Clive's and the above test's recommendation from PCL, again if the offer is itself genuine, this LINK saves a bit.

edit: looks a bit clumsy to use on my Brompton's front wheel, but that seems par for the course, for gauges and inflators as well. Pencils typically go no where near high enough.

 

[otherclive]

The digital ones, if this LINK test is itself reliable, seem to be good on accuracy.

If looking at Clive's and the above test's recommendation from PCL, again if the offer is itself genuine, this LINK saves a bit.

edit: looks a bit clumsy to use on my Brompton's front wheel, but that seems par for the course, for gauges and inflators as well. Pencils typically go no where near high enough.

That’s the one I purchased. Looking at PCLs website it’s much cheaper on eBay or Amazon. Apart from its accuracy compared to pencil gauges it’s very easy to use and doesn’t lose air as you put it onto the tyre valve as many gauges tend to especially on alloy spoked wheels.

 

[izzy]

I use a locking dial guage with a short flexi lead. seems fairly accurate

 

[toad a caravan]

I bought a "Swift" (£10 approx) spare wheel carrier that fits into the front locker,my van has two locker doors so getting the spare wheel in place isn't easy,I prefer a struggle and spare wheel rather than no spare

 

[Buckman]

There are cases where the in car tyre pressure warning system is not one displaying the pressures but simply a technology that warns based on comparing the relative wheel rotation speeds.
Should the owner of a car have that type of system I can well understand they would like to have a pressure display, not least because they can be proactive to more modest pressure losses than IME the speed derived system comes up with.
Plus the speed based system does not know the pressures are "wrong", they could all be down a bit, only that one wheel has an issue relative to the others.

If I remember correctly the Suzuki Across is a RAV4 in disguise. Last year I took a Landcruiser for a test drive and noticed that tyre pressures were not displayed so you are probably correct. Myself I would prefer it where I can see the pressure in each individual wheel and also get a warning if the spare drops below pressure.

 

[toad a caravan]

 

[otherclive]

If I remember correctly the Suzuki Across is a RAV4 in disguise. Last year I took a Landcruiser for a test drive and noticed that tyre pressures were not displayed so you are probably correct. Myself I would prefer it where I can see the pressure in each individual wheel and also get a warning if the spare drops below pressure.

Are there TPMS that also monitor the spare? I check mine every couple of months or when going in a holiday jaunt.

 

[Buckman]

Are there TPMS that also monitor the spare? I check mine every couple of months or when going in a holiday jaunt.

Ours does as flashes up an alarm if the pressure drops below 2.1 bar.