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shouldibedoingthis

Joined:

Aug 14

Posts: 4

Tyre pressure guages, what to believe?

 I had a new tyre fitted and when I got home to check with "pencil type" guage it showed 25psi.  I did a check because  the steering did feel a little unusual. My bike needs 32psi.

So I've been back to the dealer who were very helpful :smile they did work on the tyre and upon return I whipped out my pencil tyre pressure guage in front of the manager, I asked "what the tyre was inflated to?" he say 32 psi, I did the test and it was 37psi :blink:
So he went into his shop and brought out a new tyre guage (£16) did the same test, it read 37psi :blink: So he went and got his "calibrated" gauge (£100 unit) and did a test, that showed 32psi.

So two cheapies indicate 37psi and the calibrated shop guage reads 37psi.

The dealer was very helpful so no complaints there at all. But I am at a loss to know which guage to believe, any suggestions would be helpful.

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  • Posted 34 days ago (19 August 2014 13:30)

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philehidiot

Joined:

Feb 09

Posts: 4759

philehidiot says:

I would

be suspicious of a pencil type gauge as I have had a duff one before. A decent digital one is usually reliable. If his is calibrated you have to wonder if the calibration is out...


Perhaps get another garage to quickly check it? Riding with low pressures isn't a good thing.

EDIT: Don't use a petrol station one as they're notoriously dodgy. If you're in or around Leeds I'll happily meet you with my pressure gauge and check them. Bear in mind that the pressures will be higher just after a ride and they should be checked whilst the tyre is cool.

[This Reply has been modified by the Author]

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shouldibedoingthis

Joined:

Aug 14

Posts: 4

erm.. yes but...

Yeh thanks for that, although I do understand the tyre temp thing, when to take the measurements, petrol station gauges being dodgy and high/low tyre pressue not good which is why I want to get a good reading.

As for suspect pencil type, the digital one did confirm it!? :blink:Actually the pencil type I have got top marks in the MCN review!

I need a lie down.:unsure:

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James600zx

Joined:

Sep 07

Posts: 2825

James600zx says:

Pressure.

Ten years ago petrol station air lines with a bar meter on the nozzle probably were inaccurate. As soon as the nozzle and integral meter was dropped on the floor its accuracy was lost until the next calibration, if indeed it ever was re-calibrated.  In these more modern times of Health & Safety and over-eager lawyers the modern digital machines must surely be accurate, no?

Have a look at the second post here from nicke20 in May 2014:

http://forums.moneysavingexpert.com/showthread.php?t=4981572&page=2

Your dealer's air line meter might be an older design and/or not as carefully calibrated. See what the machine on the local petrol station forecourt says.

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mirloXXbob

Joined:

Mar 14

Posts: 173

mirloXXbob says:

Tire gauges

Years ago I took my pickup truck to a shop where a friend worked and he and his co-workers swamped the truck checking everything from oil to brakes to suspension, etc. They checked the tire pressures with a high-dollar Snap-On gauge, insisting that no other gauge on earth was as accurate. I pulled my Yamaha tool kit gauge I got with my YZ125 out of the glove box and followed them around the truck checking each tire after they did. My gauge gave the exact same readings. I still use that gauge 30 years later with no problems. Still, the digital gauges are probably best these days.

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shouldibedoingthis

Joined:

Aug 14

Posts: 4

NOT the forecourt meter!!

OK no more mention of forecourt pressure gauges! I KNOW THEY ARE USUALLY WRONG! :ph43r: and I'm NOT talking about that one!

I'm talking about the "reference" £100+ pressure gauge the dealer keeps locked away only used to check their workshop gauges are to spec. and gets "inspected" by the DoT.
 

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James600zx

Joined:

Sep 07

Posts: 2825

James600zx says:

Forecourt meter.

"OK no more mention of forecourt pressure gauges! I KNOW THEY ARE USUALLY WRONG!"


Did you read my post?

How did the dealer explain the disparity between his DOT calibrated meter and the stuff he is selling?

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shouldibedoingthis

Joined:

Aug 14

Posts: 4

we just stood bemused

Hi James, yes I did read what you posted and still can't see why it's relevant. I am not talking about the forecourt pump which your post seem to refer to, unless I'm mistaken.

Pehaps I give more detail. I take my bike to dealer for new tyre fitting, they fit tyre, all OK so I whip out my pressure tester (knowing there have been problems in the past) which reads 38psi. I ask Service Manager what the correct pressure should be, he say 33psi which is correct (as I already checked the manual beforehand).

So he goes and from his retail shop gets a new pressure digital guage and he does the same test. It reads 38psi. Which agrees with my pencil guage.

So he goes into workshop and gets "treasured" DoT pressure guage and tries it, it reads 33psi, which is why the workshop set the pressure to that, so which is wrong??

He shows me the calibration cert for the meter, which isn't a cal cert for that specific guage, but the spec. Not the same thing. Service Manager says DoT inspector is OK with that as meter is just under 2 years old. Which is how the Service Manager justifies the "trusted" guage.

The dealer was very nice and understanding, no bad feelings or words, but we are both uncertain which is correct as I'm sure they have a legal responsibility to put the correct tyre pressures in, obviously. I'm sure he won't want to let me know, simply to avoid any liability issues so I'm not expecting a response either way. So it's more for my own safety.



[This Reply has been modified by the Author]

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philehidiot

Joined:

Feb 09

Posts: 4759

philehidiot says:

What

James is saying that the only way to really prove which is right is to test on another gauge and see which is correct.


I am willing to believe that modern forecourt gauges are better than older ones but I just do it myself at home. I have a gauge on the pump and a decent digital one which tend to more or less agree to within a PSI.

As he says, try the forecourt one and what that says will tell you which one to agree with. I find it odd that he trusts his calibration so much when two different gauges are both different to his but agreeing with each other.

I remember a review of gauges - there were two pencil type ones in it and one was perfect and one was utter shite - I'd got the shite one hadn't I.

Anyhoos, the consensus seems to be to get one more measurement and see what it says. If you get another one around the 37 mark then that's thee readings at 37 and go with that and if you get another one around the 32 mark then I suppose you have to run with it. Just make sure your tyres aren't warm when you do it. A quick run down the road is fine but more than a mile and you're going to increase the pressure fairly significantly.

Also, if they're 5 PSI over then it'll be an excessively bumpy ride and possibly a little twitchy if it's the front tyre.

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James600zx

Joined:

Sep 07

Posts: 2825

James600zx says:

Pressure gauge.

Yes, I'm suggesting that a digital machine at a major petrol station will have a recent calibration which you can rely on. It sounds as though the dealer's device hasn't been calibrated in the two years since it left the manufacturer, so I'll bet it's out.

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philehidiot

Joined:

Feb 09

Posts: 4759

philehidiot says:

damnit

they suckled upon my 3 day old socks and appeared to enjoy it.


What fresh hell is this?

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