Very frustrated over tyre pressure

IrishHomer

I have just got a new mountain bike its a La Pierre technic 500

http://www.cyclesuperstore.ie/shop/pc/viewPrd.asp?idcategory=232&idproduct=17846


I was told by the salesman to put 60psi into the wheels.

I went to the local garage and i wanted to be precise with the pressure and i was being carefull as i have had bikes for all of my life (30yrs).

Anyway the rear wheel burst and i got a right frigght and my left ear is slightly deaf. I was fuming with myself and i went and put in a second tube and once again i carefully pumped it up and this time i only put 58psi into the wheel. By the way the front wheel was pumped up to 60psi without any problems.

Anyway this time it didnt pop on me but when i arrived home with the bike in my van when i tool out the bike the bloody 2nd tube was in shreds! :eek:

I have a 3rd tube in the rear wheel now and i am terrified to pump it up. Any advise or comments appreciated (i feel so frustrated trying ot do things correctsly)

makospeed

I remember when I was replacing a spoke once I removed the rim tape and forgot to put the rim tape back...stupid I know...so pumped the tyre with my floorpump and bang, got some fright....check no spoke is protruding and run your finger along the inside of the tyre as well

blorg

You can't reliably pump wheels to a specific pressure in most petrol stations; you can't trust the gauge in a petrol station (it is designed for car tyres) and have to do it by tyre feel, in very short bursts only. It is possible if you have experience doing it, I can pump my wheels without them exploding but I certainly couldn't tell you what pressure I get them to; I suspect I marginally underinflate.

But you are better off buying a track pump, which are designed for bike pressure ranges, with a decent gauge, and pumping them up that way.

ednwireland

i've never used a garage airline but its really easy to over inflate with those, i normally run 50 psi on the mtb and i'm a heavy guy. i'd only run 60 with slicks on the mtb 60 sounds high offroad youd want 45
what does it say on the tyre / inner tube as the max its on there mind you you may just have got a duff inner tube. it happens.
actually jut googled the tyres on your lnk and it says max pressure 58psi lucky you didnt blow them off the rim

ollietrex

Who ever told you to pump MTB tyres to 60psi is stupid... If you look at the side wall of the tyre it will probably recommend no more pressure than about 30-50 psi.

I run my mountain bike tyres at 30psi for off road and 35psi if I am going to do a fair distance on road. I have only ever put 50+ psi in my tyres and that was to get a set of tubeless tryes to seal.

Now if he was talking about road tyres that is a different story but you have a mountain bike so about 30psi'ish should be fine.

Chris Peak

I heard you can put about 20psi more than what it says on the tyre wall...

I run my mtb slicks (on road) at about 80psi and never had a problem. The only time I had blowouts was when I had old tyres with very thin/ damaged walls. Or, when the rim tape wore too thin.


I'd bring the tubes back to the shop and tell them you followed their instructions, and show what happened!
You might get a few free tubes off them, though they will try put you off by asking if the tyre was on properly...

jwwie

go back to the shop and pick up a tire pump with a gauge on it (after you argue for a few new tubes). even if you cycle every day, the tires will lose pressure and will periodically need air. this is one of the most important/overlooked tools to have. then just follow directions on the tube/tire for pressure recommendations.

72hundred

Yeah my semi-slicks come with a recommendation of 95 psi, and I usually give 'em 100, to negate pressure lost during decoupling the connector.

Although after hearing stories of exploding tires, I might go around 95 now.

72oo

daymobrew

jwwie wrote: »

go back to the shop and pick up a tire pump with a gauge on it

I carry the Topeak Master Blaster Guage on my frame and have the Topeak Joe Blow Sport track pump at home. Very easy to get the right pressure.

Chips Lovell

daymobrew wrote: »

...and have the Topeak Job Blow Sport track pump at home.

Odd choice of name

niceonetom

:P it's a typo. i very interesting typo.


...paging dr. freud, paging dr. freud, could dr. freud please come to the cycling forum...

kenmc

In fairness it does say on the air-lines in garage forecourts something along the lines of "not to be used to inflate bicycles, inflatable toys, swimming pools or air mattresses etc".

el tel

Never blow up bike tyres using a forecourt pump. Bike tyres take only a very small volume of air and are easily exploded by these pumps which are for motor vehicles only. Furthermore, the pressure gauges on them cannot be relied upon as being accurate.

You would be better getting a track pump as suggested by others here.
Alternatively, you could get an Assos tyre inflation cylinder which uses only the purest low-molecular weight Swiss mountain air.

rubadub

kenmc wrote: »

In fairness it does say on the air-lines in garage forecourts something along the lines of "not to be used to inflate bicycles, inflatable toys, swimming pools or air mattresses etc".

Yes, to cover themselves, and so paying customers in cars getting petrol do not have to wait for kids with bikes.

Most important is going in slow bursts. If going from flat be very careful. I had a tube slip out the side, huge big balloon pumping up. Also if from flat you can get twists or stretching inside, so there can be friction etc in the tube. I fill it up, let it down a bit, leave a while and pump in short bursts.

Check the rims & spokes as mentioned, also be sure your tube is suitable for the tyre. If you put a small tube in a big tyre it will blow easily.

These things all have a factor of safety engineered in, so it blowing at 60 means something is really wrong. I would expect my 120rated tyres to take 160 easily (I do not do that). Most things have a factor of safety built in, e.g. my pressure cooker is 15psi, yet max rated operating is 43psi, I have a barbell rated to 60kg and have had 130kg on it. They have to allow for people with faulty gauges etc.

stuf

rubadub wrote: »

Yes, to cover themselves, and so paying customers in cars getting petrol do not have to wait for kids with bikes.

Not really, they have to cover themselves as it can be dangerous. Bike tyres work at much higher pressures than car tyres so the effects of a blow out can be quite bad.

daymobrew

niceonetom wrote: »

:P it's a typo. i very interesting typo.


...paging dr. freud, paging dr. freud, could dr. freud please come to the cycling forum...

I've fixed the embarrassing typo.

Mmm, "paging" reminds me of Miami Sound Machine's "Dr Beat". Classic 80s.

blorg

You need to use a track pump to reliably get the right pressure. You cannot trust the gauge on a forecourt pump.

Having said that you can use a forecourt pump if you are careful and know what you are doing. Ignore the gauge completely, go by tyre feel and only in slow bursts as rubadub says. I have a presta-schraeder adaptor on all my bikes and often top up at a petrol station after a puncture (inflating as far as I can with my mini-pump first.)

I've pumped my tyres at a forecourt hundreds of times and have never had one explode yet (based on my history posting stuff in this forum, I will get a puncture tomorrow and the tyre will explode when I pump it up in a petrol station, and the rim will crack for good measure.)