Weird front tyre blow outs

essjaydee

I've read (somewhere, but can't find it now!) about using the brakes on prolonged down hills which eventually cause the tyre to blow. A friend had this happen today. He was ok, but wrecked the tyre and damaged the rim. Not good.

I was even luckier, as I'd just finished a 75 mile sportive, which had a couple of mile down hill run to the finish, and when I got over the finish line I noticed the front tyre bulging in several places :shock:

Packed the bike up in the car and went and got some refreshments, and when I returned the tyre had blown wrecking the tyre.

So what caused this?
Was it prolonged brake use which overheated the rim and tube causing it to blow. It was just shy of 20 degrees today. I checked the tyre pressures before setting off and they where 105 psi front & rear.

Team4Luke

very very likely, all downhill braking should be done with some cooling, ie on/off on the brakes and keeping the speed down, if not a lengthly spell of full brakes on will superheat the rim. I have seen first hand a tube squeeze through between rim and tyre into a huge balloon and explode, luckily my friend was stopped at the bottom of the descent T Junc. I would guess hard to damage the tyre, but possible, if the tyre was in very poor condition/old then potentially the tube could explode and split/damage the tyre too. Also, it is a good idea, that when putting bike back in car on a hot day to let the tyres go down a little and cover them up from the sun.

Omar Little

maybe the pad was rubbing on the tyre slightly when braking?

You are right though - tyres can blow if you drag the brakes going down a hill causing the rim to overheat but i think you'd need to be pretty unlucky for that to happen on the size of the descents that the UK has to offer. If it was to happen on a UK descent then i think it would IMO be more likely to be due to some other issue like a brake pad rubbing the tyre rather than the rim overheating.

cougie

I've blown my tyre descending alpe d'huez - but that was a combination of a 10 mile descent, heavy traffic, 30 degree heat and stupid pressures 140 psi.

Are your tyres worn maybe ? Or maybe your pump isn't very accurate ?

Monty Dog

Some carbon-faired clincher wheels are reknown for overheating and latex inners make matters worse.

JohnBoyUK

This is a timely post.

I had a tyre blow out on me on the descent down Birling Hill in Kent on Saturday. Was a GP4000S on a Fulcrum 3 rear wheel. Thankfully it was just passed the Z bend and was only doing 30mph at the time. Heard a massive bang, felt the back end kick out and instantly unclipped my right foot to keep my balance and slid speedway-style to a halt with my heart in my mouth 100 yards down the road with my life flashing before my eyes.

I have a tendency to come down descents fully on my brakes as I'm 15st and I fly if I dont. Had never done the descent before, never knew the road so thought I'd try and take it as easy as I could. I know I shouldnt come down on the brakes but other than trusting the bike and having balls of steel, I'm going to be even more tentative coming down descents now than I was previously.

Never want to go through that again. Was shaking like a leaf for an hour. I'm fortunate I was with a friend who made a 5 mile detour to the nearest bike shop to pick me up a new tyre so we eventually managed our maiden 2012 century in the sunshine but the descents afterwards were no fun at all.

Was talking to one of my club experts and they said it'll come naturally, just keep low, keep your weight over the back wheel and trust the bike. Bit difficult to trust the bike when you've had a tyre blow out at that speed!

amaferanga

Monty Dog wrote:

Some carbon-faired clincher wheels are reknown for overheating and latex inners make matters worse.

What difference does the fairing make? What are these wheels then and can you point me to all these reports of tyre blow-outs caused by overheating rims?

essjaydee

My tyre had done 600 miles only and was in very good condition, with no noticeable signs of damage, flints etc

Tyre was a Vittoria Zaffiro, which came with the bike.

Wish I had hindsight, as I think it would have been sensible to drop the pressure slightly, and will bear that in mind for future rides.

Thanks for replies

itsnotarace

amaferanga wrote:

Monty Dog wrote:

Some carbon-faired clincher wheels are reknown for overheating and latex inners make matters worse.

What difference does the fairing make? What are these wheels then and can you point me to all these reports of tyre blow-outs caused by overheating rims?

Plenty of reports on google but I will save you the time and link one for you

http://themanleyreport.blogspot.co.uk/2 ... ilure.html

John.T

itsnotarace wrote:

amaferanga wrote:

Monty Dog wrote:

Some carbon-faired clincher wheels are reknown for overheating and latex inners make matters worse.

What difference does the fairing make? What are these wheels then and can you point me to all these reports of tyre blow-outs caused by overheating rims?

Plenty of reports on google but I will save you the time and link one for you
http://themanleyreport.blogspot.co.uk/2 ... ilure.html

It is full carbon rims that give most trouble as they don't dissipate heat as well as alloy ones. Carbon faired alloy clinchers are not as bad but not as good as full alloy. You can get rim failure such as in the above blog with full carbon but not likely with the others.
Tyre failure is not common and is usually due to excess pressure in the first place.
Tube failure due to heat is quite common even on the UK hills and is due to bad braking practice. IE dragging the brake instead of staying off the brakes then braking hard before corners. This gives the rims time to cool on the straights (and is much more fun ).

amaferanga

itsnotarace wrote:

amaferanga wrote:

Monty Dog wrote:

Some carbon-faired clincher wheels are reknown for overheating and latex inners make matters worse.

What difference does the fairing make? What are these wheels then and can you point me to all these reports of tyre blow-outs caused by overheating rims?

Plenty of reports on google but I will save you the time and link one for you

http://themanleyreport.blogspot.co.uk/2 ... ilure.html

By carbon faired clincher I'd assumed alloy rim with carbon fairings, like the RS80. Anyway, even with a full carbon clincher you'd have to be braking like a muppet to overheat rims on the sort of hills we have in the UK (been riding and racing on a set for a while now). I doubt very, very much that heating is the issue in the OP's friends case.

Team4Luke

As I know the OP's friend, it is incorrect to say we don't have the descents here in the UK, as I said I have seen it happen first hand, in wales actually and it wasn't on the greatest of descents, however, very worth noting also the weight of the rider, both the OP's friend and my mate were not light guys !
Another excellent point made above too, was about pads touching tyres, but none the less always worth regular checking of pads, when badly worn and if set high they can bridge across into the tyre bead.
Please be careful on descents, keep your speed down to manageable levels ( I call it survivable speed ), I have been there on more than once occasion when it has gone wrong, badly so.

essjaydee

I'm no lightweight either!

As to braking technique, I do tend to use the brake hard then release technique rather than drag them.

Will have another look at my pad positioning, as I had just fitted a set of Swisstop greens.
Excellent pads btw

itsnotarace

amaferanga wrote:

itsnotarace wrote:

amaferanga wrote:

Monty Dog wrote:

Some carbon-faired clincher wheels are reknown for overheating and latex inners make matters worse.

What difference does the fairing make? What are these wheels then and can you point me to all these reports of tyre blow-outs caused by overheating rims?

Plenty of reports on google but I will save you the time and link one for you

http://themanleyreport.blogspot.co.uk/2 ... ilure.html

By carbon faired clincher I'd assumed alloy rim with carbon fairings, like the RS80. Anyway, even with a full carbon clincher you'd have to be braking like a muppet to overheat rims on the sort of hills we have in the UK (been riding and racing on a set for a while now). I doubt very, very much that heating is the issue in the OP's friends case.

I was assuming he was talking about a carbon braking service

mudcovered

I've had a front tyre unseat itself from the bead and slip around the wheel due to excessive braking heat multiple times. This then caused the inner tube valve to shear. When I replaced the tyre I realised it was a defect with the tyre (bead didn't really seat tightly enough) and I've never had a problem since.

This was on a Mavic Open Pro Rim with CX Canti brakes. The rim was definitely hot at the point the tyre failed as it was still seriously hot to the touch when I was replacing the inner tube. I've not had a recurrence since I replaced the tyre. It has made me a bit wary though so I try and alternate my brake use between front & rear when following slow vehicles (cars ) down steep hills.

Mike

rake

essjaydee wrote:

I'm no lightweight either!

As to braking technique, I do tend to use the brake hard then release technique rather than drag them.

Will have another look at my pad positioning, as I had just fitted a set of Swisstop greens.
Excellent pads btw

some say that breaking technique has no noticeable impactact on heat build up in the brakes. im inclined to belive it. same energy involved however you brake.

Team4Luke

rake wrote:

essjaydee wrote:

I'm no lightweight either!

As to braking technique, I do tend to use the brake hard then release technique rather than drag them.

Will have another look at my pad positioning, as I had just fitted a set of Swisstop greens.
Excellent pads btw

some say that breaking technique has no noticeable impactact on heat build up in the brakes. im inclined to belive it. same energy involved however you brake.

just allows a little rest and cooling of the rim, sometimes brakes held on will not slow you down, block fade, personally I don't do hard breaking, just keep my speed down and lots of short on off braking, any minor uphill section can be used to naturally slow before cresting over and continuing down.

Giant Phil

Ambient temperature can change the pressure in a tyre by up to 5%, the temperature change generated by breaking can put the pressure up by 25%, factor in that your weight is also forward whilst breaking.

..... in case you wanted to know.

essjaydee

Thanks

joshr96

It's likely that the heat from the braking caused the tire to blow because the temperature obviously wasn't in your favor.
A more unlikely explanation is that convection may have occurred inside the tire?

jim453

Josh Harfoot wrote:

It's likely that the heat from the braking caused the tire to blow because the temperature obviously wasn't in your favor.
A more unlikely explanation is that convection may have occurred inside the tire?

What?

andrewjoseph

:twisted: convection currents, you know, like magma rising through the mantle and causing hotspots. perhaps the rim had melted in that area and caused intrusions between rim,inner and tyre. Could be nasty, blowing molten aluminium, latex and kevlar everywhere!

Get disk brakes! :twisted:

t5nel

amaferanga wrote:

itsnotarace wrote:

amaferanga wrote:

Monty Dog wrote:

Some carbon-faired clincher wheels are reknown for overheating and latex inners make matters worse.

What difference does the fairing make? What are these wheels then and can you point me to all these reports of tyre blow-outs caused by overheating rims?

Plenty of reports on google but I will save you the time and link one for you

http://themanleyreport.blogspot.co.uk/2 ... ilure.html

By carbon faired clincher I'd assumed alloy rim with carbon fairings, like the RS80. Anyway, even with a full carbon clincher you'd have to be braking like a muppet to overheat rims on the sort of hills we have in the UK (been riding and racing on a set for a while now). I doubt very, very much that heating is the issue in the OP's friends case.

Carbo fairing is just that i.e. the wheel is built from a normal alloy rim which is structural and then has a carbon fairing bonded on the inside to give a deep aero section. Bontrager aeolus and mavic cosmic carbon are examples off the top of my head. I gess if nothing else the carbon will prevent a significant amount of the alloy rim being exposed to cool, fast moving air which is excellent at keeping the heat down.

I would still expect full carbon rims to fair worst of all as the heat will not conduct so freely around the rim so you are more likely to get hot spots.