Thread To Tell Everyone What Fettling You've Just Done

Coriander

I took my pannier rack off.

And put it back on a few days later.

:shock: :shock: :shock:

Get me.

OK, I confess, a knight in shining armour had to take the rack off for me as I couldn't. :roll:

Specialized Needs

el_presidente wrote:

[It does that, always need a proper pump after a couple of days if you have filled with CO2.

Why is that, though? I would have thought the CO2 molecules would be 'chunkier' than N2, which I presume is what effectively we are pumping in normally. If so it should leak less, I'd have thought; unless there is a weird interaction with the hydrocarbons in the tube.

Any smart explanations, anyone?

Stuey01

duncedunce wrote:

el_presidente wrote:

[It does that, always need a proper pump after a couple of days if you have filled with CO2.

Why is that, though? I would have thought the CO2 molecules would be 'chunkier' than N2, which I presume is what effectively we are pumping in normally. If so it should leak less, I'd have thought; unless there is a weird interaction with the hydrocarbons in the tube.

Any smart explanations, anyone?

Google tells me that N2 is larger than CO2. I don't pretend to know why.

benno68

My bike is running like a dream since my mini service last week so I haven't fettled at all.

There is my old Peugeot (only a 501 frame) in desperate need of some TLC. I've never fully stripped a bike down, but I'm going to get stuck in soon as I want to get it back on the road after 15+ years in retirement.

I've got a soft spot for Peugeot's.

shoulder_of_orion

Nothing. No wait, I lubed my transmission a few days ago after the rain. Woohoo.

marchant

A little bit of annual leave fettling here, finally got around to sorting out my wife's (free) bike. Mainly rubbing down the cheap steel rims with wire wool, cleaning said rims, and toeing in & adjusting the brakes - the squeaky brakes were the reason the previous owner stopped using it. Their loss.

d.n.f

duncedunce wrote:

el_presidente wrote:

[It does that, always need a proper pump after a couple of days if you have filled with CO2.

Why is that, though? I would have thought the CO2 molecules would be 'chunkier' than N2, which I presume is what effectively we are pumping in normally. If so it should leak less, I'd have thought; unless there is a weird interaction with the hydrocarbons in the tube.

Any smart explanations, anyone?

I would hazard a guess it is to do with the gas cooling. It must get hot going through a small hole at a rate of knots because of the friction, so you end up with a tyre full of 'hot' gas.
As a gas cools its pressure drops.

Probably totally wrong but that's my theory anyway...

Jamey

biondino wrote:

Thanks! Though it's not even close to being original (Jamey inspired it, along with the bike-bit-buying thread).

Aww, thanks.

I must admit I was very tempted to resurrect the "Things that go wrong with my bike" thread a few weeks back when I had a crank arm shear through and also (separately, within a few days) managed to snap three spokes in my rear wheel while trying to true it as the threadlock on the nipples prevented them from turning, so the spokes were just twisting.

But then I thought it wouldn't be right if the thread just had this massive gap in the log where I'd stopped filling it in, so I didn't bother.

Still waiting for the replacement crank arm from Evans/Specialized/FSA. Luckily I already had a complete spare chainset I'd picked up for £17 in the Chainreaction flood sale a while back.

Mattinthezie

I replaced my rear mudguard with an sks one, which was a little more complicated than I thought it would be - had to cut the stays down a bit - but it is a lot more solid than the previous zefal guard.

Also changed the back brake blocks to Swissstop greens and can't believe the difference it has made!

el_presidente

d.n.f wrote:

duncedunce wrote:

el_presidente wrote:

[It does that, always need a proper pump after a couple of days if you have filled with CO2.

Why is that, though? I would have thought the CO2 molecules would be 'chunkier' than N2, which I presume is what effectively we are pumping in normally. If so it should leak less, I'd have thought; unless there is a weird interaction with the hydrocarbons in the tube.

Any smart explanations, anyone?

I would hazard a guess it is to do with the gas cooling. It must get hot going through a small hole at a rate of knots because of the friction, so you end up with a tyre full of 'hot' gas.
As a gas cools its pressure drops.

Probably totally wrong but that's my theory anyway...

aah but as a gas expands it cools down - hence why the canister is freezing cold at the end. I don't buy it.

lost_in_thought

Just finished off my new handlebars with some new bar tape, and I've not actually done a bad job, if I may say so myself!

Kieran_Burns

el_presidente wrote:

d.n.f wrote:

duncedunce wrote:

el_presidente wrote:

[It does that, always need a proper pump after a couple of days if you have filled with CO2.

Why is that, though? I would have thought the CO2 molecules would be 'chunkier' than N2, which I presume is what effectively we are pumping in normally. If so it should leak less, I'd have thought; unless there is a weird interaction with the hydrocarbons in the tube.

Any smart explanations, anyone?

I would hazard a guess it is to do with the gas cooling. It must get hot going through a small hole at a rate of knots because of the friction, so you end up with a tyre full of 'hot' gas.
As a gas cools its pressure drops.

Probably totally wrong but that's my theory anyway...

aah but as a gas expands it cools down - hence why the canister is freezing cold at the end. I don't buy it.

Read this: http://en.wikipedia.org/wiki/Gas_Laws come back and discuss

cjcp

Just fitted my new bar tape.

King Donut

Snapped my old chain last night to force myself to fit a new one/clean drive train this morning. Woke up late and got train to work instead.

d.n.f

el_presidente wrote:

d.n.f wrote:

duncedunce wrote:

el_presidente wrote:

[It does that, always need a proper pump after a couple of days if you have filled with CO2.

Why is that, though? I would have thought the CO2 molecules would be 'chunkier' than N2, which I presume is what effectively we are pumping in normally. If so it should leak less, I'd have thought; unless there is a weird interaction with the hydrocarbons in the tube.

Any smart explanations, anyone?

I would hazard a guess it is to do with the gas cooling. It must get hot going through a small hole at a rate of knots because of the friction, so you end up with a tyre full of 'hot' gas.
As a gas cools its pressure drops.

Probably totally wrong but that's my theory anyway...

aah but as a gas expands it cools down - hence why the canister is freezing cold at the end. I don't buy it.

but isn't the CO2 in the canister liquid? so rather than expanding it's evaporating - and taking heat with it. ie heating the gas but cooling the liquid until it's all gone.
Then heat that gas some more by forcing it through a small hole and bobs ya uncle, warm tyres.

Jamey

Warning: thread tangent detected.

MonkeyMonster

lost_in_thought wrote:

Just finished off my new handlebars with some new bar tape, and I've not actually done a bad job, if I may say so myself!

Surely we need some pics to make sure...

cjcp

Jamey wrote:

Warning: thread tangent detected.

d.n.f

cjcp wrote:

Jamey wrote:

Warning: thread tangent detected.

Yeah, good point.

Errr, i adjusted a girls seat to horizontal at work..... :?

ride_whenever

i've cleaned up some second hand qr skewers over lunch and will fit them now.

MonkeyMonster

d.n.f wrote:

Errr, i adjusted a girls seat to horizontal at work.....

That surely is for another thread too... perhaps not even this forum!

benno68

MonkeyMonster wrote:

d.n.f wrote:

Errr, i adjusted a girls seat to horizontal at work.....

That surely is for another thread too... perhaps not even this forum!

Do you have a specific forum in mind Monkey Monster?

Sorry - going off track again - ho hum.

Jamey

Mmm... Adjusting girls to be horizontal...

Anyway, I was meant to be fettling my mate's rear mech this lunchtime but he got called into a meeting so we're doing it tomorrow now. I'm not holding out much hope as I think his hanger is a bit bent but I'll see what I can do.

d.n.f

Jamey wrote:

Mmm... Adjusting girls to be horizontal...

Anyway, I was meant to be fettling my mate's rear mech this lunchtime .

*cough* :shock:

Thats worse than mine surely!

il_principe

cjcp wrote:

Just fitted my new bar tape.

You've used proper tape and not gaffer tape this time I trust.

We will examine LiT's taping job on friday, whilst sat inside avoiding the Welsh rain...

cjcp

Il Principe wrote:

cjcp wrote:

Just fitted my new bar tape.

You've used proper tape and not gaffer tape this time I trust.

Yup. Only Ritchey bar tape this time, not Wickes' finest insulating tape.

Underscore

d.n.f wrote:

...

but isn't the CO2 in the canister liquid? so rather than expanding it's evaporating - and taking heat with it. ie heating the gas but cooling the liquid until it's all gone.
Then heat that gas some more by forcing it through a small hole and bobs ya uncle, warm tyres.

From Q & A with Lennard Zinn:

Butyl rubber dominates the market and is used for almost all tubeless tires and bike tubes as its permeability to air is incredibly low — butyl tubes have only 10 percent the leakage rates of natural latex rubber tubes.

Permeation by diffusion predicts gas leakage rates proportional to the inverse of the square root of their molecular weights. Using air as a reference the predicted leakage rates for common gases are: helium 2.7, air 1.0, nitrogen 1.02, oxygen 0.95, argon 0.85, carbon dioxide 0.81.

It turns out however that the leakage rate of CO2 is huge, and the reason is that it is actually soluble in butyl rubber and is thus not constrained to normal permeation loss, it can transfer straight through the bulk rubber resulting in severe tire pressure loss on the order of a single day. CO2 is not likely to be replaced by argon or other gases in refill cartridges, however, because CO2 is much more easily liquefied than other gases and can be contained in a moderate-pressure cartridge in a patch kit. An analogous cartridge holding N2 or argon (non-liquified gas) would be dangerous and would require a thick (and very heavy) steel-walled storage vessel.

Back on topic, I replaced the pads on my MTB front disc. Braking not great though, so I'm going to try realigning the calliper. Could just be the pads bedding in though...

_

biondino

It turns out however that the leakage rate of CO2 is huge, and the reason is that it is actually soluble in butyl rubber

So, basically, your tyres have gone fizzy.

d.n.f

Underscore wrote:

It turns out however that the leakage rate of CO2 is huge, and the reason is that it is actually soluble in butyl rubber and is thus not constrained to normal permeation loss, it can transfer straight through the bulk rubber resulting in severe tire pressure loss on the order of a single day.

Ah, see, so I was wrong.

benno68

Il Principe wrote:

cjcp wrote:

Just fitted my new bar tape.

You've used proper tape and not gaffer tape this time I trust.

We will examine LiT's taping job on friday, whilst sat inside avoiding the Welsh rain...

@Il Principe - get out in it - it's character building so they say!

cough cough, back on topic - I adjusted my rear brake 1mm to the left