BrownhillsBob's #365daysofbiking

On a bike, riding somewhere. Every day, rain or shine.

Posts tagged ‘mechanics’

#365daysofbiking It’s only flat at the bottom!

Friday November 21st 2020 – One here for Bob’s big book of bizarre mechanical failures – specifically the ‘This is not my circus, and those are most definitely not my monkeys’ chapter.

This is not my bike. I was asked by an old family friend to change their tyres, as they didn’t feel comfortable to do so themselves. ‘No problem!’ I assured them as they wheeled the bike into the garage.

First step, remove rear wheel and let air out of the old tyre. Simple enough. Since the tubes would be too big for the new tyres, I removed the valve for a full deflation – and the telltale green ooze of tyre sealant – slime brand – bubbled out.

This would be no problem, usually, except the local bike shop who originally fitted these tyres made a mistake.

What I found was only half of the tyre went down – the other half opposite the valve state inflated. That I was astounded and somewhat bemused is an understatement.

Never, ever had seen that before, and it took me a few minutes to work out – with the help of a mate by text – to diagnose that the tube had been twisted when fitted, under inflation the pressure had compressed the two twists, and the sealant blocked them creating an effective seal.

Great. But how do you release the trapped air?

I didn’t want to try puncturing it. Friend suggested a sharp tap with a blunt, soft object on the inflated section, or bouncing it off the floor. I grabbed an offcut of 2×2 and rapped the tire sharply.

There was a loud bang, and a volcanic ejaculation of green sealant.

Everywhere.It went everywhere. It’s just possible there’s an object in the workshop that doesn’t have green slime on it somewhere, but as yet I’ve not found one. A total mess. I was dripping.

The areas where the tube had twisted had clearly worn tissue-thin against the tyre, and the tap with the wood was the straw that broke it’s back.There was no patching THAT tube.

I have never seen this before, and probably never will do again, but it was a messy, if perplexing adventure.

That was a blowout on the road waiting to happen, and the bike shop deserve a slap.

Fixing other people’s bikes is never as simple as you think…

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#365daysofbiking Grime scene

December 9th – The increasingly poor weather really is taking it’s toll on the bikes. I’m not a fanatical bike cleaner, and prefer my steeds to show the dull patina of constant use: but right now it’s less of a film and more inches of crud picked up from the muddy trails and roads.

I’m working on the basis that this layer of detritus will prevent further ingress, but to be honest I’m not hopeful.

Next spring I’m going to have to do a lot of work on these bikes.

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#365daysofbiking A grim toll

November 15th – The bikes are suffering in the bad weather.

A continual spray of road water containing grit, balsam, leaf litter and road salt is getting into the brakes, frame and drivetrain. The pads and brake discs are wearing fast.

I need to get on with some TLC and show my steeds some love.

But while the bad weather persists, anything other than essential work seems like a losing battle.

It’s not just the rider that needs some dry weather….

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#365daysofbikingTension makes a tangle


November 8th – Spotted on a rather new-looking Raleigh ladies step-trough bike on the train on the way to Birmingham in the morning. A curious spring fitted between the downtime and rear of the fork crown.

I’ve never noticed this before. It seems an odd idea and I had no idea of the function, other than perhaps to modulate the handling to compensate perhaps for poor frame design.

A bright friend came to my aid – it’s actually a very weak spring to serve a somewhat unusual purpose. The bike has a kickstand fitted. The spring merely stops the forks flipping around when using the stand, keeping it upright.

A strange idea, but I would imagine quite effective.

You learn something new every day.

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#365daysofbiking Groovy, man


June 26th – Weeks of commuting in rain and grim weather are taking their toll on my brakes. Thinking I’d be in for a decent spell, I replaced the brake discs and pads on this bike in early spring.

Now it’s the end of June and they’re groovier than a 1970s Parisian jazz club.

The bikes are suffering: Corrosion, road grime, grit. This weather is eating my bikes.

A bit of sun and dryness isn’t too much to ask, is it?

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#365daysofbiking On the rebound

January 11th – I’ve had a winter of mechanical problems with the bikes, and one has concerned suspension.

Forks with suspension can be a blessing and a curse, and the ones I use have a sealed air spring with a hydraulic damper, and several adjustments – air volume, pressure, slow rebound, fast rebound – all of which significantly affect the ride.

If you don’t have suspension tuned correctly, you can lose a lot of efficiency in compressing the forks with every pedal revolution. The ones I use can be locked out to make them rigid in use on road, but that’s only half a solution.

Since the forks have had work done, they’ve lost all my fine tuning and I need to start from scratch, so I’ve cheated on the lengthy process of dialling them in – I’ve borrowed a Shockwiz.

Shockwiz is a small electronic gizmo (a bit smaller than a matchbox) that is cable tied to the fork, and connected by a small hose to the air spring valve. It uses pressure and other sensors to detect the motion of the forks over a variety of riding conditions, and it just sits there, logging the data.

With a brilliant companion phone app connected via bluetooth, you set various measurements and chose what kind of profile you want, and over successive rides, the app will make recommendations on adjustments to make, and request you ride certain surfaces – like bumpy trails or whatever.

You adjust, then restart the process.

Within a few rides you get a fantastic ride that really is what you’re looking for – often by telling you to make adjustments that are counter-intuitive.

Shockwiz is very expensive, but if you can borrow or hire one like I did, it’s a godsend. A month or more long process sorted in a few days. And probably far better.

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#365daysofbiking The daily grind:

25th November – A mechanical job that should have been easy was far from it. Replacing brake discs resulted in a struggle with seized fasteners, the failure of a brake calliper and the discovery that the parts I thought I had in the spares box brand new for this eventually were in fact the wrong ones.

The front disc was so badly worn it was starting to warp.

For a job I thought would take 15 minutes and leave me bags of time to get out turned into hours and I was lucky to get time for tea…

Perhaps I shouldn’t leave it so long next time.

#365daysofbiking Spring has sprung:

September 13th – Spotted in a customer’s bike shed, and improvised, clever repair to a brake calliper with a broken return spring.

The return spring – present in some form in nearly every type of brake – forces the brake off once the lever is released.

Since the brake cable pulls the yoke awards the cable end stop to engage the disc brake fitted here, forcing the two apart will duplicate the effect of releasing the brake as performed normally by a return spring. The spring has clearly broken and instead of replacing the whole calliper, the owner has released the cable, threaded on a very stiff spring and re-assembled the cable. The cable retains the spring and the brake operates as normal.

Clever. I’m impressed.

February 13th – I wore out a set of front brake pads, and still have a fair few part worn ones glazed out from the problems with the rear brake, which I wouldn’t throw away in case I found a way to reclaim them.

I’ve been thinking about it idly, and I’ve managed to recover a set. I filed off the surface a little with a clean flat file surface. Filing alone doesn’t work, so working on the basis whatever has destroyed them must be oil based, I took the pads, placed them on an aluminium sheet, and gently heated them with a very hot plumber’s blowtorch for ten minutes, until they stopped smoking when I removed the flame.

I then cleaned off the oxidisation with a scotchbrite pad and finally degreased them with a zero residue spray cleaner.

They are as good as new. Without the heat, none of these steps have worked before. 

I guess you could stove the pads in a normal kitchen oven if you don’t have a blowtorch.

It’s saved a few bob, I guess. Be interesting to see if they wear any quicker or glaze again.

February 18th – Brakes. Can’t keep stopping like this…

Thanks for all the suggestions for answers to the sudden loss of braking power issue. The disc is not greasy, the pads are dry and the disc is only 0.06mm down from new thickness – although that one really did make me think, so cheers for the suggestion.

I put in a set of Shimano pads. They worked fine once bedded in, without cleaning the disc. The old ones look glazed, and seems to be a grumble in online bike forums. 

I’ve decided to trial some aftermarket alternative pads to see how they fare in comparison – the red ones are Kool Stop, who are famed for old-style brake blocks, and the other set, with separate heatsinks are from Uberbike. The Kool Stops are at the pricey end of the market, the others, cheap. The interesting thing about the Uberbike ones is they come in synthetic, metal and semi-metal flavours, and you can buy the pad separate to the sink, so they’re cheaper.

Got the Kool Stops in for now. I’ll report back. Again, thanks for all the advice.