the current economic climate, LBS's are bound to lose out to internet retailers. That's Capitalism for yer. It's a nice idea, but brutal economics wins every time.

I disagree. You can't buy good service or expertise over the Internet. Some IBDs are suffering but it's mainly because they aren't evolving. Granted, the likes of Wiggle and CRC are undercutting the retail side of many independent bike shops, but the smart ones are still keeping their customers by giving them the service and advice they need and having excellent mechanics.

And as STW shows us all on a daily basis, most amateur mechanics are far from experts!

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…and yes, tension is a force. It's a pulling force instead of a pushing force but it's still a force. A force has only magnitude and direction.

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You're right that the forces from the air inside the rim do not change – after all, as you say, the rim has the same surface area, the air pressure is the same, so the force it exerts on the rim is the same.

I think you may not be seeing how the forces on the tyre are turned into forces pulling on the rim.

The bigger tyre, as you say, has more surface area so has more force acting on it. However, because the tyre does not expand (or, at least, doesn't expand very much – as someone else said, double your air pressure and your tyre will not double in size), those increased forces don't just act to expand the tyre.

OK, an imagination experiment:

Imagine you have a small cereal box, one of those little variety pack ones. You've taken all the cereal out and left the flaps open. You turn it upside down and sellotape the flaps to a table so it's "open" side down and the flaps are sticking out, taped to the table. Now you drill a hole through the bottom of the table under the box and put a balloon through it. Then you try to inflate the balloon. It will need quite a bit of puff, but sooner or later as you blow up the balloon it will force the box off the table. The force from the air pressure inside the balloon will not be able to expand the box, so it will be released in the only remaining direction, and lift the box away from the table.

Does that make sense?

Where the tyre analogy comes in is that if you instead use a full size cereal box, or maybe a shoe box, instead (and a bigger balloon), you won't need as much air pressure. As before, the air pressure will push against the sides of the box and they'll push back, meaning that the force ends up pushing against the table and lifting the box up.

Granted, this is not an exact analogy, the forces inside the tyre and rim are in slightly different directions, but the general principle is the same…

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You've got a point. Evans do have a lot of clout with their suppliers but sometimes, regardless of clout, you can't make a container ship cross an ocean any faster, or make sure that the right container was loaded in the first place. It was unintuitive of Evans not to actually tell you what the problem was when it was clear there was a delay.

And as far as I know "available in stock in 7-10 days" is used on most websites to mean "we don't stock it but our supplier usually does and if they've got it we can usually get it in a week". It does, however, assume that the item's in stock at the supplier. It's not exactly dishonest but it's the easiest way to look like you can sell something you haven't actually got…

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I think that's the bit we're all trying to explain and why people keep repeating that pressure and force are very different things.

I weigh 75kg. That means the FORCE I exert on the earth due to gravity is 75kg (assuming g=10ms^-2 and not using Newtons as a unit for the moment)

If I stand on the floor in my Vans, the surface area of the soles is, let's say (25x10cm^2 x2 = ) 500cm^2. So the PRESSURE I exert on the floor is 75kg per 500cm^2, or 0.15kg per square centimetre.

However, if I put on pair of stiletto heels and stand on just one heel, I haven't changed my weight, so the FORCE I exert is exactly the same. But this time all that force is concentrated on an area, let's say, 1 sqaure centimetre in size. The PRESSURE I'm exerting is now 75kg in just one square centimetre.

Does this make sense so far?

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I've always used Turtle Wax car wax stuff on the Solitude, the few times I've given it a proper wash. It's great, makes it look fantastically shiny and ensures the water and mud doesn't even get a chance to stick. For a while, anyway.

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Actually the bridge analogy is not bad. Part of what I tried to explain is that more tyre with the same pressure acting on it (per unit area of tyre) will mean more force on the rim. Which is quite a lot like more bridge of the same density means more weight on the cables.

So to carry on that analogy, the rim strength is the strength of the cables holding up the bridge. A small tyre is a narrow bridge; a big tyre is a wide bridge. Increasing the pressure is like adding more material uniformly to the bridge: you can make the narrow bridge much thicker before the cables snap, whereas because the wide bridge has much more area, you can only make it a little thicker (all over) before the cables snap.

Kind of convoluted, but hope that helps.

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If it had been advertised as "suitable for all types of chain" and you'd bought it and found it wasn't suitable for your type of chain, some sort of failure would have occurred on DMR's part.

If you've been given a component that you haven't properly researched and then found out that it's sold as being explicitly INcompatible with your chain and you then come on here whingeing about it somehow being DMR's fault, I think the thread title would be more appropriately "PeterPoddy planning and reasoning – EPIC FAIL!"

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It may also cross your mind that with a few minutes' careful work with a file you can widen the groove in the roller and make the free part you got work like the one you should have paid for…

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In Evans' defence, it's quite likely that they genuinely thought there _was_ a delivery coming from Trek (who distribute Gary Fisher), but that the due date kept being moved. It seems to have happened quite a lot this year, and taking your custom elsewhere wouldn't have solved the problem because nobody else could get hold of the bike either.

However, I suspect this will turn into yet another "yes and they didn't fix my puncture, Evans are crap I'm going to CRC" thread… :roll:

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Measure and weigh the box and have a look at http://www.interparcel.com to compare carriers…

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In short, yes. The chain will effectively change length (from the chain tension point of view) and it's best to have something to take up the slack or you're more likely to lose the chain.

You can't use it on a fixie. You want as even chain tension as possible. I've seen several efforts at using Biopace rings on fixed wheel bikes. All were abandoned.

Sorry to be blunt!

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It's not that the force is being dissipated, it's that there is more force, because there is more air at that pressure.

Each of those arrows is meant to represent the same amount of force. Pressure is force per amount of area, so if the pressure stays constant then more area means more overall force. If you count one arrow as one unit of force, then inside the rim there are 11 arrows – 11 units of force – in both cases. This makes sense because there is the same area, the same amount of air, at the same pressure, inside the rim itself in both cases.

But in the tyre, outside the rim, the small tyre has 16 arrows – 16 units of force – acting on it. The large tyre has 26 arrows – 26 units of force – acting on it. Those forces don't just get dissipated or go away. Because the tyre can't expand, those forces pull on the tyre so that they are transferred to the rim (the tyre is the rope in the tug-of-war analogy).

Now, granted, the rim is pretty stiff. In most cases, it doesn't move. It would be like the tug-of-war rope being attached to a brick wall. Because there is an equal and opposite force being exerted, the brick wall exerts a force on the rope so that it doesn't go anywhere. Likewise, the rim exerts a force right back against the tyre to stop it going anywhere.

But just like the wall is only so strong, a rim can only provide a finite amount of force to resist the air pressure trying to pull the tyre and trying to force the rim apart. If you add enough men, or enough rope with one man per metre, you can pull the wall down. Likewise, if you put in enough pressure, or make the tyre _really_ big and keep the pressure low, that resultant force will pull the rim apart.

The trouble is with force is that it can't be dissipated. It can be opposed: if I push against a wall, the wall opposes with the same force. But it can't just go away. The force isn't dissipated, it's still there, as the pressure senses in my hands will tell me.

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OK, here we go…

Those are the rims in black biro, and the tyres in blue biro. I've assumed that the inner tube will inflate to fill the entire space (as it does) so the little arrows show force.

The "problem" forces are the ones I've drawn in pencil. They're the ones that will try and pull the rim apart. They're caused by the tyre pulling on the rim in that direction.

As I hope you can see, the arrows inside the tyre are pretty evenly and regularly spaced. Imagine both tyres are at the same pressure. There are the same number of green arrows in both diagrams, because the tyres are at the same pressure so there are the same forces acting on the inside bit of each rim.

However, the red arrows should also be pretty evenly spaced. You don't need to count them to see that the bigger tyre has more red arrows because the air pressure is acting over more of an area of tyre material. As the tyre doesn't expand (very much) under this pressure, this is effectively the same as adding more rope, with more men at one man per metre, to the tug-of-war analogy. The pressure itself (one man per metre) hasn't increased, but the amount of stuff that the pressure is acting on (the rope, or the tyre) has increased.

And that's the bit that means there is more force being exerted, in the direction of the pencil arrows, on the rim. Not from the amount of air inside the rim (which stays the same), but through the tyre pulling on the rim edges. A bigger tyre at the same pressure means more pulling.*

I hope this makes sense!

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* or, what I haven't shown, more air pressure means more pulling in both cases. It would increase the number of all arrows.

Hang on a minute, I'll try and draw a picture.

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The tyre doesn't absorb _all_ the extra force from the air pressure. Tyre casings have lots of threads that are designed _not_ to expand too much. What happens is that extra air pressure is converted into extra force trying to pull the tyre away from the rim.

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The bit where I'm getting stuck, however, is that the rim is designed to withstand a certain maximum force over it's area, but if the area remains constant, then the pressure/force exerted on each square inch of it always remains the same, no?

This is true – but the problem is not the air pressure's direct force on the rim, it's the air pressure pushing on the bit of the tyre that's outside the rim – the direction of the forces that result from this means that the tyre tries to pull the hooky bit away from the rim and make it more of a V-shape.

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BTW a drop-in chain checker like this is usually accurate:

whereas the dial sort of tools are usually no good:

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OK. My turn to try.

We've already said that force is not the same as pressure. Pressure acts over an area, force just acts in a direction (at one point). I'll try to focus on force.

I think the reason rim manufacturers have limits is to prevent the rim sides being split apart – too much force against the walls from the inside will press them away from each other. The problem is not that the rim will be squashed to be a smaller circle, but that the rim in cross-section will become less like a U shape (where the sides of the U are the braking surfaces, if you had rim brakes) and more like a big V as the walls get pulled apart. Also that the hooky bit of the rim that holds the tyre on will get pulled away from the rest of the rim.

So I'm going to try to explain this while thinking about a cross-section of the rim with the tyre and tube fitted – don't worry about the whole rim as a circle, that's not the problem, just think about the cross-section of the rim like this:

When you fit a tyre to a rim, as you inflate the tyre the bead (the bright red dots) hooks inside the rim wall to hold the tyre on. As you increase the pressure in the tube (the pink circle), the tube expands and applies more force to hold the bead into the groove inside the rim wall. However, as the tube expands, it also applies more force to the rest of the tyre (the bit at the bottom of the picture above), which tries to pull the bead out of the groove, or pull the hooked bit of rim away from the rest of the rim.

The way the air pressure acts to try and expand the tyre (and pull it away from the rim) is important here. The bigger the tyre, the more tyre material there is for the air pressure to act on. So a small tyre will only have a small cross-section of material for the air pressure to pull on, whereas if you try to imagine the picture above with a tyre double the size, you can imagine that there will be lots more tyre material that the air pressure is pressing against.

That's the important bit – if you fit a small tyre and you inflate it to, say 30psi, the air pressure will only be acting on a small area of tyre so it will not provide a lot of force against the side walls of the rim or try to pull the hooked part away. If you fitted a big tyre and inflated it to 30psi, that pressure will be acting on a lot more tyre so there will be more force trying to pull the hook away from the rest of the rim.

The "problem" force is not the force between the rim walls, it's the force that the rest of the tyre (not inside the rim) is exerting on the rim. So if you keep the air pressure the same, more tyre means more force trying to pull the rim apart.

I guess if you want to bring the difference between pressure and force into it, think of one side of a tug-of-war with one man per metre pulling on a fixed length of rope. The force on the rim is the overall pull on the rope. You can increase the force on the rope by increasing the number of men – say two men per metre – and this is similar to increasing the pressure in the tyre. Or you can increase the force on the rope by adding on more rope and keeping one man per metre, effectively adding more men. This is like fitting a bigger tyre at the same pressure.

Hope this makes sense.

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There will always be a few chumps who will ride kit into the ground and claim that it works fine but the reason that people like KMC, who make some of the best chains in the world, specify wear parameters is so that people know when you're using the chains within those parameters they will be as reliable as they're designed to be.

Like with just about every other component, of course you can cover it in gritty crap, abuse it and never lube it and if you're lucky it might keep working for a long time. But it's not meant to work that way and you can't then whine about how unreliable or poor quality a brand is if you haven't looked after it.

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Nice to start matching up forum names to faces I met!

Am contemplating making a longer trip out of Belgium next year – if it's a simple ferry journey from Newcastle then a great reason to drive up and ride Northern trails for a couple of days first…

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The drop-in tools measure wear at 0.75% and 1% overall values.

At 0.75% you can usually get away with just changing the chain and keeping the cassette, if they are the first of both.

At 1% you usually need to change the chain and cassette.

I'd only worry about changing the front ring if the teeth are looking hooked or if front ring shifting is suffering – somewhere between 5 and 10 chains is pretty normal for rings as long as you're sensible with your gear changes (i.e. ease off the pressure a little when changing).

So 0.75% = 12.1"ish
And 1% = 12.12"

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My parents have one without the motor (it came with the house).

Can't say I'm that impressed, it doesn't feel much more sturdy than the old up and over kind. And there's a whacking great gap at the top when it's pulled down.

However, it's entirely possible that they don't have the make of door you're looking at, just a crappy roller door.

It may be worth trying to get quotes from people who make shutters and doors for warehouses and shops – they're designed for security and daily use so should be sturdy and reliable.

HTH.

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http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=250512851252

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=260587492975

…

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A second-hand Orange? Mrs. Pierre is 5'0" and rides a 13" P7 – I know mamadairt (on here) is also small and had a lovely little Orange.

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I would:

– put the tube inside the tyre before putting the tyre near the rim. Inflate it only very slightly so that it just holds its shape. This should prevent you pinching it on its way in; you can always let a little air out if it's tough to fit

– put the valve through the rim hole and fit one bead (one side of the tyre) starting at the valve and working round to the far side. You should not need a tyre lever for this bit. This side is now done.

– starting from opposite the valve, begin to fit the other bead. Work evenly on both sides towards the valve. When things begin to get difficult, go back to where you started on this side and push the bead further "into" the rim so that it goes into the well in the middle of the rim. This should give you a little more bead to work with near the valve side as the middle of the rim (in cross section) is a smaller diameter so you have a bit more bead available at the other side near the valve.

– be careful not to pinch the tube. If it's really tough to fit, let a little air out of the tube and see if it gets easier. You shouldn't need tyre levers.

Hope this helps. Like I said, that's what I would do. I've worked in the bike trade for quite a few years and have removed and fitted thousands of tyres, literally. Once you get into the habit of doing it "the easy way" then you can fit (and often remove) most tyres without having to use tyre levers – although, of course, a few tyres are really awkward even _with_ levers.

One last thing: when you inflate the tyre, put only about 15-20psi in it then check all the way round the bead on both sides of the tyre to make sure it's seated properly. The ridged or striped band on the tyre should be evenly visible all the way round – any narrow bits or bulges and you need to pull the tyre about to even it out, otherwise you increase the risk of a blowout or tyre rolloff.

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The atmosphere at the London Marathon is unlike any other I've run – don't expect a PB (far FAR too many people for probably the first hour or so) but it will be an amazing experience for her if she can run the distance.

Go for it!

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Like Bentos said, whisky doesn't age in the bottle, it ages in the cask. So there's no point "laying up" a whisky.

You'd need to take some very good advice on a wine you could buy now that would be mature in 17 years' time, and I'm not sure a 17/18 year old would appreciate it enough.

My wife's dad gave her a bottle of port for her 21st birthday that he'd had in the loft since the year she was born. It was probably the nicest thing we've ever drunk, really rich and smooth.

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If they are a European airline and flying into/around Europe then they do have a legal duty to provide meals and accomodation for passnegers stuck abroad. If Mr O'Leary hasn't built this risk into his pricing policy then perhaps his buisness model isn't quite a good as he thinks.

gonefishin is completely right. Airlines operating flights inside Europe (or European operators flying the return journey from anywhere in the world back to Europe) have to either refund the passengers or provide accommodation and meals (the passenger gets to choose) in the case of a delay of any kind.

O'Leary is a devious whinging scumbag but when he agreed to operate from Europe, he agreed to these rules. If his business wasn't adequately prepared or insured for this sort of event, it's their fault and should rightfully be their loss.

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A brilliant brilliant weekend. Thanks again Sheldon and the other KoN. Amazing riding, lovely people, CHEESE, ale, bands, bike throwing, crazy Belgians – great event. See you at SSUK!

Oh, and I'd forgotten about the Polish Moonshine. That and Taz's green rocket fuel may be responsible for me forgetting other parts of the weekend too…

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oh crap, I'm never going to be able to grow a beard in time. Maybe I can find one of these…

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…and Rigida Zac 19R are decent rims, also 19mm wide, double eyeletted and I've built probably around 14ish, they build up well.

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£30 719s on eBay:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=390140578742

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Play with fire and you get burned.

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Plain gauge aren't necessarily weaker but they build a less resilient wheel. Double butting (or, more correctly, swaging) makes the material in the middle of the spoke thinner, which makes it more flexible ("stretchy!"). This allows the middle of the spoke to expand and contract more under varying forces, which prevents those forces being transferred to the spoke elbow or to the hub flange.

Spokes commonly break at the elbow, mainly because that's where they end up absorbing force if the rest of the spoke doesn't. I've built hundreds of wheels and IME double butted spokes build a stronger, more resilient wheel. My recommended spokes for really heavy riders would be Sapim Force – 2.3mm at the elbow, 1.8 in the body and 2.0 at the thread – they're thicker diameter at the elbow to be even stronger.

There's all sorts of technical bumf about this online, Sheldon Brown wrote loads, Jobst Brandt has covered lots of the physics stuff in his book "The Bicycle Wheel" and Roger Musson's written some very helful stuff too.

HTH.

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Mavic Open Pros are pretty sturdy. Get a decent wheelbuilder to build it tight and strong, nice high spoke tension with double butted stainless steel spokes (NOT plain gauge, they're not stronger!) and use a mountain bike hub like an LX.

Is your colleague in London?

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I tend to avoid going through the middle of puddles in well-worn trails mainly because I can't tell how deep they are and I'm not that fond of going over the bars. I don't think it's a Southern thing, I've got no problem getting muddy…

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Sorry, should have added – Phil BB and Middleburn cranks here, they're flippin' lovely. :)

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Rounding off cranks tends to be as a result of loose crank bolts. When you fit the cranks, DO NOT grease the axle or crank itself, but use threadlock on the bolt thread and apply plenty of torque. Then just check that your bolts are still tight before every ride (or carry an 8mm allen key in your Camelbak if you're that worried!)

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Would you mind emailing me a copy of the PDF too? Can't remember if my address is in my profile but inigopete at hotmail dot com if not – thanks!

I'm tempted to join you tomorrow but a) have too much work to do and b) would be on a singlespeed!

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