any one ever tried siped tires? we use to do it to car tires for grip in winter wouldnt it work on rock? by the way (sipe) many razor cuts acoss the tire for better bite.

Tried it once but the tread blocks on a trials tyre protrude too far compared to a car tyre and the sipes just started a tear in the block.I had better results by trimming the sides of the blocks to get a sharper edge....but it was a lot of fannying on for little gain.

I don't think the rules allow modified tyres.

I bought a Knobby Knife which makes it easier to cut a sharp edge than a razor blade. I sharpened up a few leading edges but haven't gotten around to doing the whole tire or adding tread to the top of the knob. I'm going to try it on my boot soles also.

Ishy is right of course . However I have to admit to spending happyhours many years ago cutting leading edges sharp ; I used a junior hacksaw with the blade ground into a thin sharp edge. I think Razor cuts as described simply make the surface more flexible ..spread ..contact tarmac better perhaps.

thanks guys i was just curious.

while it could be done if you wanted to, defiantly not allowed under acu rules (tyre has to be commercially available)

while it could be done if you wanted to, defiantly not allowed under acu rules

RUBBISH!

Whether you're defiant or not, siped tyres are allowed.

If you look at a new Michelin or Dunlop there are sipes in the tread blocks, they're not enormously deep, but they are there.

It's been a while since I've had a new Dunlop but the Michelin has 5 concentric rows of blocks and every block in the 3 centre rows has 4 sipes, in a square pattern but without the corners.

A long, long time ago I saw a future world champion at a trial receive a delivery of tyres. Whilst he was out riding, his crew sat down and re-cut the sipes on the tyres deeper.

So it can't be disallowed - can it?.

Anyway, since then, when I've had the time I've taken a stanley knife to my new tyres and cut the sipes deeper and it seems to help, the 'new tyre effect' seems to last a lot longer

The sipes 'squeegee' away the water on smooth wet surfaces allowing the rubber to grip.

The one control in our sport is the tyres. The size of the blocks and their spacing is strictly defined in the rule book and should limit the amount of grip available. Every tyre commercially available will have the smallest blocks and the biggest gaps allowed by the rules - that's the way to get the best grip in most trials situations.

Re-cutting the edges of a block will normally take the tyre outside of these limits and make it illegal

However, rubber compound (e.g. IRC vs Barum) and surface finish (e.g. sipes) do not seem to be at present controlled by the rule makers.

Personally, I believe that the Pirelli tyre does not conform to the rules as the blocks are not square - the leading and trailing edges are concave, this is visible to the naked eye, but since no-one uses them at a high level it goes un-noticed (or without penalty). Also the IRC tyre appears to contravene the rules by being a (relatively) 'low profile' tyre - i.e. the aspect ratio is outside the rules.

My thoughts

Re-Cut your sipes however you want, if it helps - great!!

O

RUBBISH!

Whether you're defiant or not, siped tyres are allowed.

If you look at a new Michelin or Dunlop there are sipes in the tread blocks, they're not enormously deep, but they are there.

It's been a while since I've had a new Dunlop but the Michelin has 5 concentric rows of blocks and every block in the 3 centre rows has 4 sipes, in a square pattern but without the corners.

A long, long time ago I saw a future world champion at a trial receive a delivery of tyres. Whilst he was out riding, his crew sat down and re-cut the sipes on the tyres deeper.

So it can't be disallowed - can it?.

Anyway, since then, when I've had the time I've taken a stanley knife to my new tyres and cut the sipes deeper and it seems to help, the 'new tyre effect' seems to last a lot longer

The sipes 'squeegee' away the water on smooth wet surfaces allowing the rubber to grip.

The one control in our sport is the tyres. The size of the blocks and their spacing is strictly defined in the rule book and should limit the amount of grip available. Every tyre commercially available will have the smallest blocks and the biggest gaps allowed by the rules - that's the way to get the best grip in most trials situations.

Re-cutting the edges of a block will normally take the tyre outside of these limits and make it illegal

However, rubber compound (e.g. IRC vs Barum) and surface finish (e.g. sipes) do not seem to be at present controlled by the rule makers.

Personally, I believe that the Pirelli tyre does not conform to the rules as the blocks are not square - the leading and trailing edges are concave, this is visible to the naked eye, but since no-one uses them at a high level it goes un-noticed (or without penalty). Also the IRC tyre appears to contravene the rules by being a (relatively) 'low profile' tyre - i.e. the aspect ratio is outside the rules.

My thoughts

Re-Cut your sipes however you want, if it helps - great!!

I love those two words; Stanley, and I've seen Bostich . Two American capitalist free market companies a few miles from home representing everything good.

Edited January 10, 201016 yr by rockyrider

I was referring to chewy's comments about sitting there cutting the tyres with a razor, rather than manufactures cuts in the blocks

the rules (2009 version, haven't got 2010 yet...) are below; (the is a diagram too in handbook referign to the block layout, etc).

Tyres. Only tyres which conform to the following

specification may be used. All tyres will be measured mounted

on the rim inflated to a pressure of 14 lbs/sq.in, and must

have a nominal aspect ratio of 100/100. Overall width (O)

measured at wheel spindle height must not exceed 115mm.

(Refer to diagram). Tread depth (A) must not exceed 13mm.

All tread blocks in the same circumference must be of the

same depth. The space between the tread blocks ( must not

exceed 9.5mm across the tyre or 13mm in a circumferential

direction ©. The space between the shoulder blocks (D)

must not exceed 22mm. The space across the tread (E) must

not extend completely across the tyre measured at right angles

to the tyre wall unless broken by a block. All main tread

blocks must in principle be parallel with or at right angles to

the tyre axis. (Tyre must have the same appearance if reversed

and conform in principle with these diagrams). The tyre

surface must not be fitted with any subsequently mounted

elements such as anti-skid devices, chains, etc. Note: Only

tyres available from commercial sources and complying with

these dimensions are permitted in competitions.

thank you all for your input. i am gona try it. let you know what i think. if i can even notice a differance.

I have done it quite regularly. Cutting on the surface of the tread is legal. Widening the gap between the treads above 9.5mm is not.

To cut the grooves I use a 4.5 angle grinder with a narrow cutting disc. A lot quicker than a knife!!