Cycling UK Forum

The bike I am using most at the moment has got a Continental GP 4 season tyre on the front and a Specialized Armadillo Elite All Condition tyre on the back. My rides are around the flinty lanes of Hampshire and after every ride I have to carefully inspect the tyres and remove minute shards of flint which are embedded into the tyre rubber. Experience has taught me that failure to do this will result in a visit from the P fairy, usually in pouring rain on the muddiest lane in the world. The rear tyre (Specialized) seems to attract many more flint shards than the front. Is there some reason why a rear tyre would be more prone to this or is it because there is a significant difference in the rubber compounds used that would cause one tyre to be a flint shard magnet ?

I think the front tyre flicks the flint upwards ready for the back tyre to become impaled.

I get the same issues here too. Maybe more weight is over the back wheel, so they go in deeper ?

Also the stuff they spread on the roads last winter caused a fair amount of damage, I had several goes at picking out the shards.

Will check again this weekend...

Swap the tyres over and see if it is still the same.

After heavy rain there is a fresh crop of sharp flints on the roads ready to wreak their havoc. When it is wet, flints can cut through tyre rubber more easily; water is a good cutting lubricant for rubber.

But past that, there is more load on the rear tyre and it deforms more; it flattens against the road. After many years of observing this I believe that the deformation of the tyre is most significant; I think that it can mean that once a small flint is in the thickness of the tyre, it is gradually forced inwards through the tread thickness by the deformation of the tyre.

For this to happen I think that the tyre tread has to be thick enough to hide a small flint, and that the difference between 'curved' and 'flattened' needs to be large. This being the case a skinny tyre could be worse than a wider one, because the way the tyre deforms against the road is more extreme. The deformation is most extreme in the centre of the contact patch. I note with interest that if the tyre contacts the road in a strip 15mm wide (say) then the vast majority of punctures from small flints will occur in the middle 8mm or so; just where the deformation in the tread is worst.

Recently ( a few thousand miles now) I've been using a slightly fatter rear tyre and even though it has a thinner tread, I seem to have been getting fewer flint punctures, which wasn't what I expected when I started out.

cheers

I agree with Brucey I'm a chunky monkey these days and all my punctures with flints (Norfolk and Suffolk is famous for them) are in the back. My snakebite nips etc occur on the front. I've tried most things Gator skins, Conti and used to like Michellin Kryllions. Currently I've got Bontranger hard cases as these came off wifeys bike. To be honest unless the tyre is a low end type I find them all much of a much. Check your tyres as most flints get stuck then work in.

Hi,
Flints........its a man made thing where all this crap which is straight off the crusher gets laid on the ground, all virgin and nice and sharp.

If you travel old natural lanes / tracks all the grit is weathered as to say, been down the river, from the hill up the valley even brought down by a glacier, nice and round grains.

I just wonder if any one will every get round to realise that we need to use something better than the made made stuff.
But how do you produce grit that's not been cracked off a stone.
On a off road forrest cycling specially made trail near me, either the top is covered or the tracks are just laid out with very fine really smooth grit that is smoother than even tarmac and very fast, but I guess on a flat surface drainage would be a problem.

Yeh, after the rain comes all the newly disturbed stuff.

Flinty lanes are these natural or been laid down

the flints that give you punctures get washed out of the fields onto the road, which is why some parts of the country are terrible for it and others are not. Summer rain does not seem to produce the same puncture epidemic as autumn rain presumably because there is less run-off from the fields when the crops are still in them.

By contrast roads are surfaced in granite chippings; the chippings are washed and graded, so don't produce many small flakes; the rock doesn't usually fracture that way anyway.

Whenever I get a puncture from a tiny thing I look at the tiny thing to see what it was; if I find it, about one time in ten it is a piece of glass (more than this on my town bike), about eight times out of ten it is brown (so it is a local flint) and sometimes I can't tell what it was.

In some parts of the country the flints are grey and could be mistaken for granite flakes. I doubt they are anything other than flints though.

cheers

Local geology must be a big factor. Here in South Wales i have no problems with flints. Man-made debris such as glass, combined with thorns from hedge cutting are all I have to deal with. As far as I can remember I've never had a flint puncture. Maybe this regional variation explains why some of us think one tyre is great at resisting punctures while others think the same tyre punctures every five minutes.

We have the same problem with flints here in Suffolk. And yes its usually the back rather than the front . For this reason I have taken to using a gatorskin hardshell on the rear.Last set of tyres did 7k without puncturing at which point I changed them just to be on the safe side.

Would some old school tyre savers fit the bill for this?

http://www.ebay.com/sch/i.html?_nkw=bicycle+tire+savers

Used to use them a lot when I was young and foolish and rode Sprints and Tubs all year round (not because I was super fast but because it was my only bike!)

Don't make the mistake I did though,one wore so badly it turned itself into a razor blade and stripped the tread off a Tubular in a dramatic exploding punture fest going downhill on fixed.

Was going to suggest the old school flint catchers as we used to call them. Knock the flint off before the next revolution of the wheel helps push them in further. Seen all sorts including bits of old wire run between the brake bosses... look like a recipe for a trip over the handlebars!

I've seen insulating tape used between the seat stays or chain stays but you have to pretty much do it for every ride and it looks a bit naff in my opinion.

Hi,
Not sure what we are calling flints
What I am digging out of my tyres are grey and are the stuff they are laying on cycle (:evil:) paths around Newton Abbot / Bovey Tracy.
They are sharp and burry them selves under the surface of the tyre. Even the glass is buried often too ( I am assuming this is real processed glass bottles), with out good light and even a magnifying glass / 3x mag glasses you will be hard pressed to see the slit in tyre.
So I am calling this ruddy stuff flits as they are shaped with acute angled faces that cut.

Tell me that any natural un man made stuff you would dig out of the ground would be sharp and not have rounded corners, seriously do shards of any stone that have not been mechanically crushed with the exception of slate exist
I want to be educated as I live in Devon and have not cycled that much in other counties, I might be a bit naive

Road chippings as said do not puncture that easy if at all due to shape and type of stone I am assuming.
Whatever they are dressing cycle paths with should be scrapped as its totally unsuitable, no wonder I appear to be a frequent user because others have got the message and gone back on the road...................suits me

In my area the path I was mentioning had puddles of chipping / whatever, which is bad practice as in document below.

"Suitability This method only works on surfaces that are smooth and even, as the
finished surface treatment has only minimal thickness.
Loose aggregate must be swept from the finished path before opening
it to cycle traffic.
If the surface treatment is applied directly to a stone base, then two
layers of the surface treatment are required (lower layer 6mm stone,
upper layer 3 – 6mm stone). This type of surface has been frequently
used in the early days of the NCN."
http://www.google.co.uk/url?sa=t&rct=j& ... q80ulSGSxg

If I analyse my personal puncture statistics 100% in the front tyre (that is 100% of the ONE puncture I've had !!). Really teeny flint triangular wedge (mini sharks tooth). And my fingers were already so cold they would not have worked adequately to swap inner tubes but I could get 1 mile from pumping up the type each time and was only 3 miles from a cycle shop. It was winter so the time of year with rain washing the weeny bits of broken flint off the fields onto the roads.

Ian