Boom! tyre pressure question

richjb

Morning
Just put some continental gp4s on last night and going by the psi guidelines printed on the box it looked like the maximum was 120 psi. I was only using a small pump and got to just over 100, turned around to do something else and the inner tube exploded. What did I do wrong and will my hearing come back?
Thanks
Rich

RonB

Hi Rich

Not sure if you're putting on new tyres or tubes and whether this was due to wear or a p***ture, but here goes.

Might be worth checking the inside of the tyre wall for sharps. Another possibility is that there was a pinch/ snag beween the tube and the bead of the tyre. Was the rating for the tubes or the new tyres?

I'm sure folks will come up with other possibilities, all the best, Ron.

ride_whenever

Your hearing will come back, but it'll be a bit ringy for a few days :?

Why were you pumping them up to the max? There are a few more considerations than just what is printed on them. Bit like speed limits, might be a 60 zone but 60 isn't always appropriate...

As for the cause, you've either got slightly undersized rims (possible but shouldn't be a massive problem) or you didn't seat the tyre properly, so it slipped off the rim and the innertube exploded without the retaining force of the tyre/rim combo.

richjb

thanks
the guidelines were on the tyre box. Seems likely that the tube just got pinched between the tyre and bead, was a new tube so doubt it was a puncture. won't break the bank to get a new one.

1stGenRex

yeah it helps to pump up the tube to like 20 PSI and stop to check everything is OK before proceeding.

dawebbo

Sounds like it wasn't seated properly. Agree with 1stGenRex's suggestion.

@rider_whenever: not pumping the tyres up fully will mean more rolling restistance and more likely to get a pinch flat. The extra grip from lower pressure is minimal, it's not like this is MTB where you vary the pressure depending on the terrain.

Stoo48

Strueth, I run 147psi (10 Bar) in mine, never had any issues, though those that ride with me live in fear of losing their hearing if it does go bang!

17 Stone on 23mm tyres

chunkytfg

Stoo48 wrote:

Strueth, I run 147psi (10 Bar) in mine, never had any issues, though those that ride with me live in fear of losing their hearing if it does go bang!

17 Stone on 23mm tyres

21 stone on 23mm tyres


I once had a tyre go bang at about 2am while the bike was in the bedroom. it had 120psi in it when it went pop. It was a Slime tyre so when I finally got up in the morning having been woken with quite a bang during the middle of the night I had slime all up the bedroom wall!! :oops:

richjb

Thanks
I guess it wasn't seated properly, I've spent the last 7 years running a big fat Norco MTB so I'm not used to this strange new world of tight skinny tubes and tyres, does one have to pay a little more attention when putting road tubes/tyres on?

danowat

Stoo48 wrote:

Strueth, I run 147psi (10 Bar) in mine, never had any issues, though those that ride with me live in fear of losing their hearing if it does go bang!

17 Stone on 23mm tyres

147psi?, christ on a bike, that must be a harsh ride!

balthazar

richjb wrote:

Thanks
I guess it wasn't seated properly, I've spent the last 7 years running a big fat Norco MTB so I'm not used to this strange new world of tight skinny tubes and tyres, does one have to pay a little more attention when putting road tubes/tyres on?

Perhaps a little more care, though fat inner tubes are not much less likely to be trapped by a tight MTB tyre. I think the difference is the higher pressure, which presents a tougher test for tyre clinching. A small piece of trapped tube, or a poorly seated bead, may work itself out on a low-pressure MTB tyre before — BANG.

emx

dawebbo wrote:

@rider_whenever: not pumping the tyres up fully will mean more rolling restistance

can somebody put this guy straight, please...?

tri-sexual

also check rim tape
from your description i guess this is one possibility ( probably the most likely cause)
tubes puncture or explode for a reason, check wheel, tyre, pressure etc, find out why it popped in the first place before attempting repair or replacement or it will happen again then you will blame the fairies
its very easy to do, when you strip tyre, inner tube, locate the puncture position and check wheel or tyre at that place for damage / foreign objects etc.
before fixing problem, fix the cause.
make sure you line up (damaged) inner tube with the tyre in the same way as you took it off (when checking for the cause) or else the damage and the cause will not line up and will be on the opposite side (of the valve).

ride_whenever

dawebbo

You are only correct on almost perfectly smooth surfaces. As soon as you're on something much rougher than an indoor velodrome you're wrong unfortunately.

Lower pressure allows the tyre to conform to the road surface, if it is pumped up too hard then it cannot deform and you have to move vertically to traverse the obstacle, losing speed.

Schwalbe have done proper scientific studies (ie they paid a phd student to ride up a hill over and over again at different pressure and surfaces with a powertap at a set speed) to confirm this.

this is also worth a read.

Lagavulin

I used to follow the tyre sidewall guides so ventured out on the roads with skinny 23C GP4000s at 125 and even Vredestein Fortezza Tricomps at 145psi - the latter once only :shock:

Have since gone very much the other way. Now run 24c Open-Paves at 90/100 and 23c Fortezza Tricomps and 22C Veloflex Paves at a little over 100psi.

Odd though when some tubes do decide to let go. Having swapped out the rear wheel I once bolted my Allez into the turbo in the lounge, chucked the DVD in, popped upstairs to for the last pre-training pee and BANG whilst at the toilet.

balthazar

ride_whenever wrote:

dawebbo

You are only correct on almost perfectly smooth surfaces. As soon as you're on something much rougher than an indoor velodrome you're wrong unfortunately.

Lower pressure allows the tyre to conform to the road surface, if it is pumped up too hard then it cannot deform and you have to move vertically to traverse the obstacle, losing speed.

Schwalbe have done proper scientific studies (ie they paid a phd student to ride up a hill over and over again at different pressure and surfaces with a powertap at a set speed) to confirm this.

this is also worth a read.

This needs unravelling. RR is a technical characteristic of tyres, and it follows a smooth, non-proportional, downward curve as pressure increases. In that respect dawebbo is absolutely right.

What you are talking about is a secondary consequence of high inflation pressure, which (supposedly) impairs the efficiency of forward progress of bicycle+rider. As I wrote before, this seems fairly obvious and - to my mind, at least - roughly aligns with experience: but I've never seen any test or data that quantifies it, and which could underpin the confidence of your analysis. This Schwalbe experiment you refer to was conducted off-road, yes? Is it not online? (Is there any equivalent on-road study?)

TommyEss

chunkytfg wrote:

Stoo48 wrote:

having been woken with quite a bang during the middle of the night I had slime all up the bedroom wall!! :oops:

Wow! So early in the year and we already have a contender for quote of 2011!!

mattsaw

Purely anecdotal, but I tend to find slightly higher pressures seem to give a slightly faster (but harsher) ride. I'm mostly cycling on pretty smooth roads though - excepting potholes :roll:

Conversely, too high a pressure seems to greatly increase the risk of punctures so I normally run between 100-110 psi

Stoo48

I can't lay claim to the slime comment......

As for the high pressures, I have never really thought about it, the ride is pretty harsh granted,. Rolling resistance would be the main reason for the high pressures, however, I can see the theory behind ride_whenevers observations.

Maybe this year I'll have a play about with the them and try and give some feedback.

dawebbo

ride_whenever wrote:

dawebbo

You are only correct on almost perfectly smooth surfaces. As soon as you're on something much rougher than an indoor velodrome you're wrong unfortunately.

Lower pressure allows the tyre to conform to the road surface, if it is pumped up too hard then it cannot deform and you have to move vertically to traverse the obstacle, losing speed.

Schwalbe have done proper scientific studies (ie they paid a phd student to ride up a hill over and over again at different pressure and surfaces with a powertap at a set speed) to confirm this.

this is also worth a read.

Seems pretty consistent with what I said, albeit I omitted the relevance of vertical displacement. All down to how you interpret what I meant by "fully" I suppose. In my experience for most roads, this is 110-120 ie. the max rating on most tyres. Clearly if you are on a particularly bumpy road this will change.