Tubes go bang!!

[Royalrider]

Recently fitted new marathons to the trusty steed and went for a spin today.
(Third time out on the new tyres)
After about 4 miles noticed the rear wheel rubbing and within a few seconds locked up. Climbed off to investigate and the tube exploded blowing the tyre off the wheel. I was outside a pub and people came out to see what the bang was.
I had two spare tubes with me fitted one and continued. About 5 miles further on same thing happened but this time to the front wheel.
So is it:
Me incorrectly fitting/pinching two tyres or faulty tubes?
The tubes were blown wide apart they are called Impac and came with the marathons..
I had inflated to 4 bars by the way.

 

[spandex]

Its not the tubes its the tyres they are not fitting your rims right if it was just one then yes it was not put on right. But both na its the tyres have a look at http://www.sheldonbrown.com/tire-sizing.html

 

[Royalrider]

Interesting read Spandex. I take it you are suggesting the size of the tyres are not right for the rims?
You may have picked up from he name that I am riding Raleigh Royal, not one of the new ones but one bought in 1983. The wheel sizes are consequently 27x 1&1/4. The new marathons are similarly marked as 27 x 1&1/4. I have never had a problem like this before. Could the tyres be incorrectly marked or slightly bigger than the stated size?
I do not think it is incorrect fitting,I have done lots of tyres over the years, and anyhow it would be unusual to incorrectly fit two one after the other.

 

[Gary D]

Royalrider,

This is surely now more than a coincidence?

Please see this thread I posted a few weeks ago on another forum citing exactly the same problem:

http://www.bikeradar.com/forums/viewtopic.php?t=12559868&highlight=

Scary eh? What wheels/rims are you using?

Gary.

 

[byegad]

I'm puzzled by your remark that the first tyre was rubbing before it went. Had you just come down a big hill with the brakes on all the way.
The ex Mrs Byegad did that once with a HUGE bang when the tyre went.
If you had that would explain an enlarged tyre before the boom!

Marathon Pluses are renowned for difficult fitting, does anyone know if plain Marathons are the same?

 

[spandex]

You can test your tyres to see how they fit by pumping them up just to 15 or 20 psi just so they are firm ish. Then try and push the tyre off the rim with your hands if you can they dont fit right so go back to the shop.

 

[mickle]

Spandex is right, its the tyres not seating correctly in the rim. A manufacturing tolerance difference of a couple of mm in the circumference of a rim or tyre can mean the difference between a dangerously loose tyre or a frustratingly tight fit. The rubbing was caused by the bulge as the tyre started to come away from the rim.

Buy new tyres!

 

[Royalrider]

Thanks all,
To answer a few questions.
The rims are Weinnman 17x630-27 x 1 1/4. I assume they were designed as a touring wheel as the bike was marketed as such.
No I hadn't just come down a hill with the brakes on, in fact I had been on a slight incline for about a mile.
You are exactly right mickle, the tyre seemed to be inflating by itself causing a lock up against the brake blocks. In fact when the front one went, because I had just experienced the back wheel,I tried to get the cap off the presta and release some air but was n't quick enough. It was rubbing/catching noise,wheel lock up, bang! all in about 10 seconds.
I had read good reports about the Schwalbe Marathons hence the purchase. But your link to the other forum Gary is interesting as they were Marathons as well. Maybe the tolerences on certain rims is very low.
I tried to push the tyres off like you suggested Spandex but they are tough and in fact had to use a lever when fitting them originally.
I have contacted the internet shop where I got them from by e-mail and they have replied with a phone number to discuss the issue with them.
You will be aware good tyres in the dimensions I need are few and far between. Local places don't stock them.
I've just ordered another 6 tubes off the net. I'll need them if they blow at this rate!!

 

[piedwagtail91]

just a thought but are they designed to go on rims which aren't "hooked"
i'm not sure if it will make a difference but given the rim name, age and size,thought it worth mentioning.
i've had trouble with marathons doing what you describe but fortunately i was still in the house.they wouldn't seat properly.
i gave up on them and went for contis.