Topeak D2 Tyre Pressure Gauge

[BazP]

Having just bought the above gauge I tested it against two track pumps and a foot pump on four tubeless tyres with presta valves. It consistently read 8psi low on the presta valves but read ok on the car valves.
With pressures around 22 to 25psi this is quite an error. There are a few historic problems on Google like this but I wondered if anyone here has used this gauge and had problems.
Getting a bit more technical, I understand that pumps take the pressure from the cylinder while gauges take it from the tyre direct. Is this the case

 

[matthewslack]

It all depends on whether the valve remains open during pumping or not. If not, the gauge is not seeing the tyre pressure directly. Perhaps different valve types behave differently...

 

[thelarkbox]

the valve needs to be open to enable a full pressure reading as said above.. if catered for what is different in the air passages between the 2 valve types, perhaps a packing fragment is obstructing or partially obstructing a crucial feed path?? and Shrader mod caps are available for Presta valves..

 

[Az.]

Why would you need device like that?

 

[soundwave]

i have one used it few times and been sat in tool box ever since

 

[BazP]

Why would you need device like that?

How do you check your tyre pressure?

 

[thelarkbox]

How do you check your tyre pressure?

A quick glance when sat on the bike backed up with a lil pinch of the tyre if unsure.

 

[Az.]

How do you check your tyre pressure?

Pumps usually have pressure gauge attached. While riding a bike you just feel it.

 

[BazP]

Pumps usually have pressure gauge attached. While riding a bike you just feel it.

Well my two pumps and a friends read slightly different and I can’t feel the difference between 23psi and 26 psi which I want.

 

[sjpt]

I can’t feel the difference between 23psi and 26 psi which I want.

Not only can you not feel it, the difference is unlikely to be significant on traction, speed, wear, noise or any other tyre parameters I can think of.

 

[Az.]

Well my two pumps and a friends read slightly different and I can’t feel the difference between 23psi and 26 psi which I want.

Does it really matter if it is 23 or 26psi? As long as you won't pump up to a crazy high pressure you should be OK. Most important is if you like the ride not the number.

 

[Cadence]

I have a Topeak D2 pressure gauge, an XLC track pump with a gauge built in and an old Smiths all-metal dial pressure gauge that belonged to my father. The Smiths gauge would have been expensive when new (early 1960's) and is capable of being calibrated.
The Topeak and Smiths are within 2-3 psi of each other at 35psi, but the XLC pump is about 10psi higher. I have no idea if any of them are accurate
For ease of use I've settled on just using the D2 and, as others have said, rather than inflating to a known accurate figure I just inflate to a number that "feels right". If I could get the Smiths calibrated I would just use that, but It can only be used on Schrader valves (although I am gradually replacing the Presta's on some of my bikes). I've used it when inflating car tyres at the local supermarket and it matches the pressure indicated by the pump, but where do you get a pressure gauge calibrated? Dunno, but not worth losing sleep over.

 

[thelarkbox]

The 'ebay' mod caps work a treat, my basic pump adaptor and fancy new battery pump are both geared towards schrader valves so after screwing up and buying a presta valved tube last time round its the way i went.. a bit more fiddley, as you need to open and close the presta valve in addition to fitting the mod cap but it provides a single consistent air in interface

?? 26 psi?? my pump gauges indicate thats a woefully under inflated tyre. then again i mass over 90kg so i guess your circa 40-50kg?? 50-60 psi is where i end up inflating to. -edit btw im only aware of the pressure thanks to the fancy new battery pump and it could be miles off, thumb pressure while pumping and a rear on the saddle and glance down to confirm the rims are clear of the ground to confirm are the 'acid tests'.

 

[BazP]

So it looks like we are all doing different types of riding. I run 2.5in tubeless tyres and ride many rocky tracks. At anything over 30psi I would be bouncing all over the place and the science is that it is quicker to roll over obstacles rather than bounce over them with the tyre conforming to the obstacle be it a rock or root. But that's for another debate. I thought that anything in the 40psi plus range was for roadies.

 

[matthewslack]

Does the science include time mending snakebites on hardtails with low tyre pressure?

 

[BazP]

I’m obviously talking to the uneducated. Some professional riders including Pidcock and Van der Poel ride on 18 and 20psi. Never had a snakebite, if I had one or two I would go with inserts. Once saw a rattler in Utah but it didn’t bite.

 

[matthewslack]

For precision measurement there is no option but to use a separate gauge directly onto the valve. That way the volume of air in the measuring system is tiny compared to that in the tyre, which minimises that source of error.

Otherwise the pump mounted gauge is at the mercy of the valve characteristics and hose volume and pumping action style, all of which make more difference at lower pressures.

My (make unknown) track pump only starts to show any tyre pressure steadily after a pump stroke on Presta above about 35psi. At low pressures it will show pressure during the pumping stroke which then drops back between strokes. My pressure target is not as critical as yours.

 

[BazP]

For precision measurement there is no option but to use a separate gauge directly onto the valve. That way the volume of air in the measuring system is tiny compared to that in the tyre, which minimises that source of error.

Otherwise the pump mounted gauge is at the mercy of the valve characteristics and hose volume and pumping action style, all of which make more difference at lower pressures.

My (make unknown) track pump only starts to show any tyre pressure steadily after a pump stroke on Presta above about 35psi. At low pressures it will show pressure during the pumping stroke which then drops back between strokes. My pressure target is not as critical as yours.

Thank you for the sensible reply. My track pump does exactly as yours does. My new gauge measures a consistent 8psi lower at the valve, which is quite a percentage at 30 psi and lower. I can put an arbitrary amount of air in to suite my riding but wondered why there was such a difference in readings.

 

[lenny]

Tyre Pressure Gauge UK 2 Bar 30 Psi

https://www.amazon.co.uk/ATsafepro-Pressure-Accurate-Professional-Mechanical/dp/B0C1SLP8LD