Losing air causing pinch flats

funkyg

Hey guys. Had a pinch flat the other night, think it may have been caused by a pot hole and low tyre pressure.
Swapped the tube, pumped up as best I could and limped home the last two miles as I'd gone cold.
When I got my compressor on the tyres it said my front tyre was only 60PSI, so I imagine the rear would have been about the same before my puncture. The thing is I pumped them up a couple of weeks ago when got the presta adaptor for my compressor so I'd lost around 50 PSI in this time.
This is my second pinch flat. When I bought the bike the LBS said they put 100 PSI in the tyres, but yet again after about two weeks I'd suffered a pinch flat.

Am I really losing so much pressure over such a small length of time? How often do people generally check their tyre pressures?

charlie_potatoes

funkyg wrote:

How often do people generally check their tyre pressures?

Prior to every ride.

sungod

^^^this

otherwise you may not realise you have a slow puncture

skinny road tyres do not have much volume, so the impact of even slight loss of air is large compared to fat tyres which run at lower pressure

butyl tubes may last up to a week before needing to be reinflated, less if you're fussy about pressure

latex tubes need reinflating every day

Mikey23

I inflate to 100 every couple of days by which time I am down to 80. Any different is an early sign that all is not well with my inners and I change straight away. Never had a pinch flat and rarely get a puncture with my gatorskins

smoggysteve

I usually ride at 7 bar on clinchers and 8+ on tubulars.

I can guarantee that every time I check the pressure it will have dropped by at least 1 bar on the clinchers and if I don't ride on the tubulars for a few weeks they will be completely flat or close to it. Fact is that a simple valve is never going to be able to hold such high pressures for a long period of time.

As far as your pinch flat, that has been the reason for every puncture I have had in the last 2 years. Higher pressures do help protect them but you do lose ride comfort so its trying to find the best happy medium for you.

Mark_P

The inner tube material is not of uniform consistency on a microscopic level, causing a loss of pressure over time following an exponential decay curve. The rate of decay will vary from manufacturer to manufacturer, as well as tube to tube, but it's a good idea to pump up your tyres before every ride.

goonz

Mine drop to about 70-80 from 100 in a week

JayKosta

After inflating to full pressure, use hard thumb pressure on the tire tread to get a 'feel' for 'full pressure'.

At least do the 'thumb test' before riding again to judge if much pressure has been lost.

I use the pump if it has been more than 2 days since inflating - regardless of 'thumb test'.

Jay Kosta
Endwell NY USA

jgsi

From what I gather, you dont own a Track Pump.
Get a decent 1 (Dont go cheap!) and keeping tyres up to pressure becomes a pleasure almost.

funkyg

Thanked for the info guys. Will be sure to check more regularly!
You're right, I don't have a track pump and it's a ball ache getting the compressor out and plugging it into the car. I did have a cheap one but the pressure blew out the tube at the bottom at about 90 PSI! You get what you pay for.

Bobbinogs

FWIW, the Bontrager Charger offers a good VFM option that just works great. Lots of other options out there (Joe Blow, Topeak, etc., worth searching for track pumps under the Road Buying Advice section).

My Charger has paid for itself as I use it on the car now instead of spending money on a garage forecourt!