Paranoid Newbie

[Frankenfish]

Hi Chatters, Frank here from E. London, 58yo. and not been in the saddle since my paper round 43 years ago. Trying to regain some fitness/lost youth I recently got myself a second hand barely used Hybrid. I've had four decent days out, longest 37 miles steady towpath pace and have already been attacked twice by fairies! The tyre sidewalls read 50-85psi yet when I carried out the second replacement I took it to just over 70, set it to one side and thirty seconds later the wheel exploded with an almighty bang(stop giggling). The actual alloy rim had split for about 8 inches(20cm) along the wear indicator, the tube had split lengthways 10 inches and although the wire was intact, the the tyre had an inch of damage just inside it. I have now replaced the fat stock tyres with Marathon Plus 35s but am fearful of going above 75psi. Was this down to bad luck, a faulty front wheel or a dodgy 'Beto' track pump gauge ? Just thankful it happened indoors and not on the street. Any thoughts ?

 

[ianrauk]

Welcome to CC Frank.
For the rim to explode that tells me that the rim was at it's limits, worn away by the brake blocks. As you said it is a second hand bike so is plausible.

It's best you check the rear wheel/rim also.
You can do this by putting a straight edge against the rim to see how much the brake blocks have eaten into the rim.

 

[Frankenfish]

Welcome to CC Frank.
For the rim to explode that tells me that the rim was at it's limits, worn away by the brake blocks. As you said it is a second hand bike so is plausible.

It's best you check the rear wheel/rim also.
You can do this by putting a straight edge against the rim to see how much the brake blocks have eaten into the rim.

Thanks Ian, the bike was only about 8 months old and hardly used as it was too big for the owner. This I could tell by the condition of the original tyres and blocks, it basically was in new excellent condition. And the other wheel rim is sound, clean.

 

[Andrius.B]

Then the bike itself was probably made from very low quality materials using very cheap and unreliable manufacturing processes and testing. Riding such bikes is usually very dangerous, as pedals can break while riding, frames can snap, brakes can break etc.

 

[Frankenfish]

Then the bike itself was probably made from very low quality materials using very cheap and unreliable manufacturing processes and testing. Riding such bikes is usually very dangerous, as pedals can break while riding, frames can snap, brakes can break etc.

Thanks Andrius, but bike is a Carrera Crossfire1 2011 model. I thought these were a reliable make.I only worry that this could happen at speed on the mean street.

 

[Pauluk]

Hi Frankenfish. What was the tyre width that exploded, 45C by any chance? What make of bike is it?

 

[Frankenfish]

Hi Frankenfish. What was the tyre width that exploded, 45C by any chance? What make of bike is it?

Yep, 45c Kenda 'all terrain' Carrera Crossfire1 2011
Also, as it was the rim that exploded, I used the tyre afterwards on a new wheel until I replaced both tyres.

 

[Peteaud]

Certainly doesn't sound as if you did anything wrong.

 

[Pauluk]

45C is a very wide tyre for a crossfire as they come with 17.5mm internal rims. I had these on my crossfire 2 but took them off and replaced with 35C.

I did ride on the 45C for a bit at a pressure of about 60 psi but I think 45C is pushing it for a 17mm rim.

The maximum tyre width shouldn't be much more than 2X the internal rim width (35C on a 17.5mm rim). I know that people will say its ok, mine was, but is it ok above 70 psi.

Just a thought.

 

[Pauluk]

By the way, crossfire (1 not usually called a one just crossfire) comes as standard with 35C tyres, not 45C so I suspect someone carried out a modification by swapping the tyres.

 

[Frankenfish]

45C is a very wide tyre for a crossfire as they come with 17.5mm internal rims. I had these on my crossfire 2 but took them off and replaced with 35C.

I did ride on the 45C for a bit at a pressure of about 60 psi but I think 45C is pushing it for a 17mm rim.

The maximum tyre width shouldn't be much more than 2X the internal rim width (35C on a 17.5mm rim). I know that people will say its ok, mine was, but is it ok above 70 psi.

Just a thought.

Nice one Paul, thanks. 35s on now. Still, not nice to happen to front at speed on a very busy street or by the water.

 

[ianrauk]

Nice one Paul, thanks. 35s on now. Still, not nice to happen to front at speed on a very busy street or by the water.

Had a rear road rim go whilst I was doing over 20mph on a commute home once... not nice

 

[Frankenfish]

By the way, crossfire (1 not usually called a one just crossfire) comes as standard with 35C tyres, not 45C so I suspect someone carried out a modification by swapping the tyres.

Paul, bike is in front of me now, printed on top tube 'Crossfire 1' halfords still have them on website.

 

[Frankenfish]

Had a rear road rim go whilst I was doing over 20mph on a commute home once... not nice

Ian, what, if anything, did you put it down to ?

 

[ianrauk]

Ian, what, if anything, did you put it down to ?

Me not checking the rims properly. Simple as that.