TPMS - Reference Pressure

Submitted: Tuesday, Apr 05, 2016 at 23:52
ThreadID: 132041 Views:3032 Replies:7 FollowUps:9
This Thread has been Archived
Dear All. I appreciate that there have been many threads on TPMS systems. I have read most on ExplorOz plus many others. Initially I was going to post a comparison table on the voiced likes and dislikes of the multiple systems available. Then laziness set in hence this post.

I want to buy a TPMS before we head off on the next big trip and I am interested in your comments.

My interest is in the amount of effort required to adjust the reference tyre pressures for each tyre/sensor after airing up or down. My research suggests that only Sensatyre has a simple system. However this may not be correct.

Whether internal or external sensors the driver has a labour overhead of either removing a valve cap or a sensor cap when airing up or down. So after the "airing" comes the adjustment to the TPMS reference pressure.

It would seem logical that you can set a single base line pressure to which all tyre sensors are referenced. For example:

Let's say the base pressure reference is 20psi and I want to set my TMPS alarm levels to cater for highway cruising. So I end up with.

Tug Front = 36 psi Reference + 16
Tug Rear = 40 psi Reference + 20
Van = 45 psi. Reference + 25

Then a rough bit of dirt is foreseen so air down required.

Tug Front = 24. reference + 4
Tug Rear = 28. Reference + 8
Van = 33. Reference + 13

So in the example I have adjusted all tyre pressures down by 12 psi.

Is there a TPMS around that allows the base line reference pressure to be adjusted by a simple button press or similar. Rather than have to reprogramme each sensor to the new pressures. In the example the reference base pressure would go from 20psi to 8 psi.

I don't wish to start an argument on best tyre pressures for different circumstances. Just want a TPMS that is simple to reset for different tyre pressures. I run 5 different pressures depending on what's underfoot and whether towing or not.

Trust the above makes sense. Always seems to when you write it.


Back Expand Un-Read 0 Moderator

Reply By: vk1dx - Wednesday, Apr 06, 2016 at 07:32

Wednesday, Apr 06, 2016 at 07:32
Hi John

That seems like a lot of trouble. Why not just set them to alarm at anything under your lowest pressure for the desert. In my case that would be 16.

For a slow leak I would feel it well before it got that low (which I have) and for a fast leak then I would hear the alarm instantly. I look at the tyres every time I get out of the car so I would see a difference in any profile. I don't believe that one should ignore the "common sense" look in favour of electronics that get shaken up heaps when you are moving and especially on dirt and rocky roads/tracks.

We have three pressures that we use. 40, 26 and 18.

Maybe I don't understand all the adjustments. What this + number mean? (ie 36 psi Reference + 16)

AnswerID: 598255

Follow Up By: Member - Rod N (QLD) - Wednesday, Apr 06, 2016 at 07:44

Wednesday, Apr 06, 2016 at 07:44
Yep, what Phil said is what I do. I have found the sensors are not as accurate as my tyre gauge so I only use them as a rough indication of when pressures change. Don't forget pressures will change as you drive and the tyres heat up, even which side the sun is on will affect pressures.
FollowupID: 867422

Reply By: Malcom M - Wednesday, Apr 06, 2016 at 08:08

Wednesday, Apr 06, 2016 at 08:08
Have a look at the Inawise units
I use the TPMS201 which is a 4 wheel unit but I have 6 wheels so bought two extra sensors.
Every time you air up or down, you hit one switch and the current pressures are automatically read and used as the new reference values. Air up - hit the switch, air down - hit the switch... Takes a couple of seconds to read.

Each wheel has a sensor that replaces the standard valve and each is coded. Changing wheels simply requires you to swap out a small ID plug on the TPMS head so it knows which tyres to look for.
You only want to see the data on the wheel you are using but they have other models if you want to see the lot all the time.
Also monitors tyre temperatures.
AnswerID: 598256

Follow Up By: HKB Electronics - Wednesday, Apr 06, 2016 at 09:03

Wednesday, Apr 06, 2016 at 09:03
X2 for the Inawise

Lifetime Member
My Profile  Send Message

FollowupID: 867425

Follow Up By: vk1dx - Wednesday, Apr 06, 2016 at 09:07

Wednesday, Apr 06, 2016 at 09:07
We have two sets of tyres and rims. One set for town and one set for trips. 10 rims all up.

Would we need ten of the Inawise sensors to cover both sets?

FollowupID: 867426

Follow Up By: Malcom M - Wednesday, Apr 06, 2016 at 11:55

Wednesday, Apr 06, 2016 at 11:55
Yes, one sensor for each monitored wheel.
I don't bother monitoring my black top set. Should be able to feel those going down.
FollowupID: 867431

Follow Up By: HKB Electronics - Wednesday, Apr 06, 2016 at 12:39

Wednesday, Apr 06, 2016 at 12:39
Keep in mind though the internal sensors have a battery life of several years, I have a set that is still going strong after 10 years.

The signal strength of the sensors is very good and no repaeter is generally needed with the inawise when used on caravans and other trailers etc.

Sensors do need to be fitted internally but give accurate temperature and pressure readings, not easy to steal and not subject to damage as can happen with external units.

Lifetime Member
My Profile  Send Message

FollowupID: 867435

Follow Up By: vk1dx - Wednesday, Apr 06, 2016 at 13:11

Wednesday, Apr 06, 2016 at 13:11

We sometimes use the "town" set for the deserts.


FollowupID: 867436

Reply By: Member - Robert1660 - Wednesday, Apr 06, 2016 at 09:54

Wednesday, Apr 06, 2016 at 09:54
Hi John,
I have recently installed a SensaTire system on 8 wheels. So far so good. Rather than installing the receiver under the vehicle I did a number of trial and error placements initially. I finally settled in a placement on the cabin side of the cargo barrier. This system appears to be able to detect each of the internal sensors easily. The sensors are the internal type strapped around the rim by a steel strap. I have set the reference pressure for all tyres rather than trying to set a reference pressure for individual tyres. A reference temperature was also set for all tyres not individual tyres.
It is most interesting to note how external factors affect tyre temperatures in particular. General heat from the engine and exhaust has a noticeable effect on the under slung spare wheel temperature. Heat from the engine also has an effect on front wheel temperature. I installed the system after I had a failed wheel bearing on the campertrailer which managed to cause a small fire. I would feel that a TPM System would be able to detect the considerable increase in temperature that occurs after such a bearing collapse.
Landcruiser 200 VX Diesel + 19ft Bushtracker

My Profile  Send Message

AnswerID: 598258

Reply By: Allan B (Member, SunCoast) - Wednesday, Apr 06, 2016 at 10:32

Wednesday, Apr 06, 2016 at 10:32
Hi John,

My current system is an Inawise internal system, several years old and a '4WD' model. This model incorporated a switch to set the baseline pressure at either of two values for on-road or off-road. All tyres are set to one baseline. It is an internal sensor model. This model (TPMS-4WD) is still available but a newer model is able to easily set the baseline by pushbutton as Malcolm has said with each tyre set to its individual baseline pressure. This is the TPMS-201-D series.

The 4WD model sets the baseline for all 4 tyres at either 27.5 / 55psi for on-road and 11.6 / 55 for off-road. The alarm operates at either 20% below the lower figure or 30% above the upper (55psi) figure with the high temperature alarm operating at a fixed 80c.

The 201D series alarm operates as above but from the baseline set for each tyre.
This clearly makes it valid to the operating baseline.

My current system is about 5 years old and battery life is nominated as about 7 years so as my current tyres are ready for replacement it would be appropriate to fit new wheel sensors. With 6 wheels (2 spares) I would be looking at $65 x 6 = $390 so it would be perhaps opportune to upgrade to the 201D series including 6 sensors at a total of $424 and gain the benefit of the superior receiver.

My Inawise has performed perfectly. A big advantage of this brand is the two extended antennas that optimise reception. In my vehicle they are fitted to extend through the floor 150mm encased in fuel-line hose like "Rubber Ducky" antennas.

There are many TPMS offered for sale at widely ranging prices. Inawise are only available through approved distributors at Inawise set pricing although it may be possible to negotiate with a distributor if purchasing new tyres at the same time.
The considerations of makes, models and internal or external sensors has been 'done to death' and it comes down to the individual's personal discretion. Good luck with your deliberations.

My Profile  My Blog  My Position  Send Message

AnswerID: 598263

Follow Up By: Malcom M - Wednesday, Apr 06, 2016 at 12:05

Wednesday, Apr 06, 2016 at 12:05
I don't like that model as it only lets you set predetermined base values as you said.
Tough if you are stuck in the sand and need to go down to 6psi but you don't have that value programmed in...
Thats the really cool thing about the 201D that you set it to anything that you can put in the tyre and on the fly.
Inawise prattle on about 4WD specific models and the 201 only handling a certain pressure range but reality is the 201 will measure near flat to damned dangerous. Love it.

You can buy direct plus they do club pricing.
FollowupID: 867432

Follow Up By: Allan B (Member, SunCoast) - Wednesday, Apr 06, 2016 at 12:35

Wednesday, Apr 06, 2016 at 12:35
Yes Malcom, the shortcoming of the '4WD' model (and others similar) is the fixed baselines.
As an example, with it set to 'on-road' then the baseline is 27.5psi with an alarm point of 22psi. If then from an inflation pressure of say 40psi the pressure dropped to 23psi the alarm would not sound but it is a severe pressure loss and the temperature would rise dramatically and not alarm until 80c which is above my comfort zone and with possible tyre damage.
Having the baseline set in the 201D at 40psi would have initiated an alarm at 32psi which is much better.
It seems to me that if you are prepared to fork-out a couple of hundred dollars on a limited system it would make good sense to go a hundred further for a very much better model. Which is what I am intending.

My Profile  My Blog  My Position  Send Message

FollowupID: 867434

Reply By: Baz - The Landy - Wednesday, Apr 06, 2016 at 13:37

Wednesday, Apr 06, 2016 at 13:37
Hi John

Whilst ease of use should not be overlooked when selecting a TPMS, most are relatively straight forward, some are better than others when it comes to resetting pressures.

I have the Doran 360 which has served me well and you can read my review here.

When changing pressures it requires a simple recoding of the pressure into the unit. If you asked me how long this takes I couldn’t tell you, because it doesn’t take that long that it bothers me.

But I’ll hazard a guess at well less than a minute.

The longest part of airing up or down is doing just that – if you are travelling with someone else have them reset the unit whilst you air up or down.

Mrs Landy does ours and has a cuppa on long before I’ve finished the actual chore of inflating or deflating.

My tip, buy the unit that gives you the most confidence that it will to do the job of monitoring the vehicle’s tyre pressures efficiently and accurately, I wouldn't focus too much on ease of use, most of the good ones are fairly straightforward and easy anyway.

Enjoy your trip, Baz – The Landy
AnswerID: 598268

Reply By: Member - J&A&KK - Wednesday, Apr 06, 2016 at 21:53

Wednesday, Apr 06, 2016 at 21:53
PHIL, Rod, Malcolm, HKB, Robert, Allen & Baz

Many thanks for the inputs. All valuable and taken into account. I am always amazed at the generosity of knowledge given by members on ExplorOz.

I will most probably go for an internal sensor system. Comments by Phil on how to deal with different pressure settings reminded me of the real issue which is not the actual tyre pressure but is it below what you would expect. This has been useful.

I am not actually interested in the individual tyre pressures at any point in time. Only interested if they are changing rapidly or falling into a zone where damage will occur. Your inputs have helpe me draw this conclusion.

Finally on anything that gives you data, on which you rely, the veracity and reliability of the source of that data becomes the most important factor. For that reason I have ruled out external cap type sensor units. Next step is to choose the internal type unit. Sensatyre and Inawise are the probable finalists.

I learnt what I wanted to understand from this thread. Thank you all.

AnswerID: 598284

Follow Up By: Idler Chris - Wednesday, Apr 06, 2016 at 22:50

Wednesday, Apr 06, 2016 at 22:50
Sensatyre. Just so easy. Displays ALL tyres at once, you get readings within seconds of turning on, no changes required if you air up or down, a couple of minutes to tell the unit where you have moved tyres when you rotate them, you can set alarms for all tyres at once or individually. Does exactly what you want, telling you all your tyre pressures or temps with the press of one button to go from one to the other.
What other people think of me is none of my business.
Do unto others what you would have them do unto you.

Lifetime Member
My Profile  My Blog  My Position  Send Message

FollowupID: 867463

Reply By: David T6 - Thursday, Apr 07, 2016 at 04:22

Thursday, Apr 07, 2016 at 04:22
I recently fitted an Inawise 203 for the Landcruiser and camper. It has the one button you press when you reset your pressure.
I did a test the other day and slowly let air out of one tyre to test the alarm. It went off after the pressure dropped 5psi.
I have not used it on a trip yet.
AnswerID: 598286

Sponsored Links