Pumping Tyres - some noob qns

[Tiek]

Hey folks,

 

I just went to pump at my petrol station this morning. I made 2 observations:

 

1) My front driver side tyre pressure is about 10kpa less than the passenger side tyre when measured by the pump before it fills up to correct pressure. Is this normal? I drive alone most of the time, so it is right side heavy most of the time.

 

2) To test if the pressure I pumped is correct, I pushed in the probe a 2nd time after pumping for all the tyres. Realised that the pressure is immediately lower than what I pumped earlier (about 5-10kpa difference). Is this normal due to the pressure loss when inserting and removing the probe? So if my desired pressure is 220kpa, should I set the meter at 230kpa, so that I can take into account the pressure lost in removing the probe?

 

Thanks for any help to a noob driver like me.

[Theoldjaffa]

yah its like that.. normally i pump twice per wheel to even out the pressure.

 

remember to pump when tyres are cold. ie: early morning and/or driven for less than 1.6km

[Madsumm]

Juz a note.. most petrol station pumps are down by 10-15psi.

 

If you pump 220 on the pumps, most means.. 210 or 205.

 

Best is to get a good tire pressure gauge and double check. BTW, I never relied on the pump's pressure indicator.

 

If you travelled on highway for more then 15-20mins at 90kmh, your tires are considered HOT.

So, its best to pump nearly 20psi more on top of your normal pumps. If its 220, you pump 240. After the tire had cooled, it should measure around 220.

 

Rgds

[Watwheels]

Time to loose some weight.

 

joking lah.

 

Best condition to fill your tyres is when they are cold. Our relative humiditiy is quite high here in sg, hence moisture will also cause pressure to drop easily.

 

Condition of your tyre will also affect the pressure ie thinner wall will have difficulty maintaining the desired pressure.

 

For your question (2), most likely the air in your tyre is still warm and air pressure unstable.

 

Aiya. Do what I do lah. Just pump in pure Nitrogen and forget about it until the next 10k km.

[Rtth84]

what pressure guage is accurate? the ones i see in accessories shops dun look accurate to me leh

[Tiek]

Tks for all the replies.

 

I pumped my tyres first thing in the morning at 7am. The petrol station is just 200m from my house, so the air inside should be still cold.

 

I did pump nitrogen last time when I changed my rims leh. But I find it a chore to go down to the workshop for free top-ups, so I decided to go and pump air today instead loh. Anyway, I found that nitro also not that great. It's only been 1 mth since my last nitro pump, and today when I measured at the petrol station, all 4 tyres have lost about 20kpa each.

 

But like what some of u said lah.. it could be that the pump at the station not accurate. But the pump looks quite new and hi-tech to me leh.. digital one.

[Watwheels]

I see...

 

To me I'm not so crazy about the numbers cos to me that small amount is insignificant.

 

I did it at KM, so every servicing I'll just ask them to check.

 

Just yesterday I changed my set of tyres and then drive to KM to top-up(not far from workplace), I realise having pure nitro the ride is slightly more comfy and quiet.

 

I dunno, maybe it's just me.

Edited June 29, 2007 by Watwheels

[Blackbird749]

After pump nitrogen, can mix with normal air pump or must die die pump nitro again when u check the air not enough??

[Watwheels]

Can! Air is 78% Nitrogen + 21% Oxygen + 1% other gases. Why not?

 

Whether u wanna do the pure nitrogen again is entirely up to u.

Edited June 29, 2007 by Watwheels

[Slowmo]

Normal Atmospheric Air is 79% Nitrogen. I doubt is a big difference though.

Edited June 29, 2007 by Slowmo

[Rtth84]

its the water vapour in the air that causes the air leak i think

[Kklee]

Tks for all the replies.

 

I pumped my tyres first thing in the morning at 7am. The petrol station is just 200m from my house, so the air inside should be still cold.

 

I did pump nitrogen last time when I changed my rims leh. But I find it a chore to go down to the workshop for free top-ups, so I decided to go and pump air today instead loh. Anyway, I found that nitro also not that great. It's only been 1 mth since my last nitro pump, and today when I measured at the petrol station, all 4 tyres have lost about 20kpa each.

 

But like what some of u said lah.. it could be that the pump at the station not accurate. But the pump looks quite new and hi-tech to me leh.. digital one.

 

Before you change rims, were you plagued with the tyres losing pressure often issue?

[Scaglietti]

My question to you... did your tyre fitter pump out all the air in the tyre before filling it with N2? I doubt so because you can't really remove all the air in the tyre before filling it up with N2. I don't think there is much difference when you are topping up with air.

 

BC

[Yeobh]

Depending on yr requirements, price of tire gauge gauge can vary from s$5.00 up to s$240.00 per pc.

Edited June 29, 2007 by Yeobh

[Madsumm]

actually, the analog dials are more accurate then digitals.

 

In bike shops (bicycles) there are some good ones, though a bit ex.

 

No matter, it will be much better then the ones at petrol station. Once. 2 tyres are totally different pressures. I would rather that at least, they are the same... 5psi diff is ok..

 

BTW, get the one in the last pic shown above. I prefer flexible tubes to the nozzle. Easier. The stick ones are difficult, depending on rims. And the digital one is what i have. Prob with digital is... its in the increment of 5. So you have +/-5 psi accuracy? Not very accurate but give a roughly good guide

 

keke.

 

Rgds

Edited June 29, 2007 by Madsumm

[Tiek]

No.. i din see him pump out any gas. I was kind of really blur back then... thought his device probably suck out the air and pump in nitro at the same time. Haha... how stupid can I get

[Furrynadz]

Juz a note.. most petrol station pumps are down by 10-15psi.

 

If you pump 220 on the pumps, most means.. 210 or 205.

 

Best is to get a good tire pressure gauge and double check. BTW, I never relied on the pump's pressure indicator.

 

If you travelled on highway for more then 15-20mins at 90kmh, your tires are considered HOT.

So, its best to pump nearly 20psi more on top of your normal pumps. If its 220, you pump 240. After the tire had cooled, it should measure around 220.

 

Rgds

 

20 psi and ur 20kpa diff hor

[Yeobh]

Yes, low pressure gauge with high resolution are expensive - like those used to take go-kart tyre pressures. I understand the pressure difference between the wheels should not be more than 0.5psi. High difference in tyre pressure will cause instability when the kart is at high speed neogiating a corner.