How to go faster?

[400bhp]

You work in finance so I hope you can work out that even pushing your average up to 17 (an increase of over 25%) is only going to save you about 15 mins (there & back).

Have a shorter shower.

Learn to throw clothes on/off quicker.

Red light jump

 

[Amanda P]

Pretending for a moment that there's no such thing as traffic (because I don't want to get into a debate with Jimbo), here's my experience from a similar commute.

I switched to using a fixed bike in winter, because the road salt was destroying derailleurs and chains at an alarming rate, and I wanted to spend time with my family and not in the workshop. It's a flat ride to work, so no problem there.

The thing about fixed is that if your speed drops, so does your cadence. There comes a point at which that becomes uncomfortable, so you automatically pedal harder, start pulling up and back on the pedals as well as pushing down, or even stand up for a bit, to get the speed, and cadence, back up to comfy levels. This is what happens when you encounter a bit of a rise, move off from a junction or hit a headwind.

So, to increase your speed, fit slightly higher gearing. And when you've raised your cruising speed so that you're comfortable with that, change to another smaller sprocket and so on.

Because there's only one gear on the bike, once you've set off, you have to go faster to maintain a comfortable cadence. There's no alternative.

This only works if your ride is pretty much flat: if there are hills you will have to compromise in your choice of gear.

 

[jimboalee]

Pretending for a moment that there's no such thing as traffic (because I don't want to get into a debate with Jimbo), here's my experience from a similar commute.

I switched to using a fixed bike in winter, because the road salt was destroying derailleurs and chains at an alarming rate, and I wanted to spend time with my family and not in the workshop. It's a flat ride to work, so no problem there.

The thing about fixed is that if your speed drops, so does your cadence. There comes a point at which that becomes uncomfortable, so you automatically pedal harder, start pulling up and back on the pedals as well as pushing down, or even stand up for a bit, to get the speed, and cadence, back up to comfy levels. This is what happens when you encounter a bit of a rise, move off from a junction or hit a headwind.

So, to increase your speed, fit slightly higher gearing. And when you've raised your cruising speed so that you're comfortable with that, change to another smaller sprocket and so on.

Because there's only one gear on the bike, once you've set off, you have to go faster to maintain a comfortable cadence. There's no alternative.

This only works if your ride is pretty much flat: if there are hills you will have to compromise in your choice of gear.

This is more or less what I've been doing with my BSA 20 over the last three or so months. I've now arranged No. 3 gear to be the gear I would ride a SS or fixie, and only use 2 and 1 on climbs.

At the beginning of the year, I had No. 2 gear as my cruising gear, hardly used top and struggled up hills in No. 1.
I've been through 18, 19, 20, 21 and 22 tooth sprockets to find the most comfortable is 20 tooth, giving a 61" gear on a 37 lb bike, with 46 and 35" gears in reserve.

61" can keep 15 mph at 81 rpm, 150 Watts at a HR of about 125 ( 70% MHR ) so there's room for some spinning.

It is now a confident Audax 100 km bike.

 

[gaz]

because someone threw cleats into this. i'll throw helmet.
Leave your helmet at home, it saves weight and less drag. win win

 

[jimboalee]

because someone threw cleats into this. i'll throw helmet.
Leave your helmet at home, it saves weight and less drag. win win

The only way you can improve drag over a helmet is to shave your head, so go and get a pack of Wilkinson Sword.
But then you'll wear a fuzzy bobble hat which knocks you back to where you started, so get a nice smooth helmet with a scull cap underneath.

 

[Bollo]

Like the power required to keep the bike moving, the amount of force to decelerate it rises with speed.

Force = mass x acceleration. Mass doesn't change but the deceleration from 20 mph into the side of a car is greater than the deceleration from 15 mph.

So if a car pulls out when you are doing 20 mph, injuries will be more likely.

If you're doing over 20 mph, at a speed motorists don't expect a cyclist to be doing, they misjudge your arrival at the junction.

I'm sorry, Jim. I kept my trap shut for you're little statistical fantasy in the Truck thread, but this is utter, utter b0llocks.

Crudely, the damage is done by that rate at which your initial kinetic energy is dissipated within your body, technically a measurement of the 'power' of the impact as (again crudely Power= Energy/time). It will also depend on the volume of your limb that absorbs the energy.

At the moment of impact...


KE = 0.5xmass x initial impact velocity^2


So, very roughly (the real calc would involve some integration over time and limbs) and assuming that the cyclist is 'stopped dead' by an impact against a hard, massive and stationary object that does not absorb much of the energy of the impact....

Damage per unit volume of cyclist ~ 0.5mv^2/(V*t)

where V is the volume absorbing the blow and t is the time taken to go from impact speed v to zero.

Stress again, a very very crude model of a real impact. The missing variable here is how the body responds to the sudden injection of energy. This in turn will depend on the limbs involved and their ability to dissipate the energy without sustaining damage.

Deceleration comes into the equation at it determines the timescale over which the energy is injected into the body and accounts for one of the 'v's in the numerator and the t in the denominator. It does not 'cause' the injury. Your model would suggest that damage increases linearly with speed, but it will actually follow something more like the square of the impact speed. This goes some of the way to explaining the proprtionally larger increase in fatality rates for pedestrian RTAs with increasing vehicle speeds.

Please Jim, stop posting dodgy physics and maths to sound clever. It's not working.

 

[snailracer]

kinetic energy is proportional to speed squared. Going 2x faster means your brakes must dissipate 4x the energy to stop you. Or your body gets 4X the damage if you crash.

Does the OP figure in the extra time needed to put on clipless shoes, change out of lycra clothes, take a shower, etc. that cycling faster would require? Overall, it may be more time efficient to cycle slower and dispense for the need to do all of the aforementioned - just put the bike away and jump straight onto the sofa with a cup of tea.

 

[jimboalee]

I'm sorry, Jim. I kept my trap shut for you're little statistical fantasy in the Truck thread, but this is utter, utter b0llocks.

Crudely, the damage is done by that rate at which your initial kinetic energy is dissipated within your body, technically a measurement of the 'power' of the impact as (again crudely Power= Energy/time). It will also depend on the volume of your limb that absorbs the energy.

At the moment of impact...


KE = 0.5xmass x initial impact velocity^2


So, very roughly (the real calc would involve some integration over time and limbs) and assuming that the cyclist is 'stopped dead' by an impact against a hard, massive and stationary object that does not absorb much of the energy of the impact....

Damage per unit volume of cyclist ~ 0.5mv^2/(V*t)

where V is the volume absorbing the blow and t is the time taken to go from impact speed v to zero.

Stress again, a very very crude model of a real impact. The missing variable here is how the body responds to the sudden injection of energy. This in turn will depend on the limbs involved and their ability to dissipate the energy without sustaining damage.

Deceleration comes into the equation at it determines the timescale over which the energy is injected into the body and accounts for one of the 'v's in the numerator and the t in the denominator. It does not 'cause' the injury. Your model would suggest that damage increases linearly with speed, but it will actually follow something more like the square of the impact speed. This goes some of the way to explaining the proprtionally larger increase in fatality rates for pedestrian RTAs with increasing vehicle speeds.

Please Jim, stop posting dodgy physics and maths to sound clever. It's not working.

Thanks for putting me right.

Would you agree that the faster Snailracer's tea cup hits a wall, the more small pieces it breaks into?

Is it the same for the human cranium, or will it just squidge because its inside a skin bag?

No formulas please, just a simple explanation to suit the intelligence of a cyclist who rides at 20 mph between stationary traffic.

I may have got all the wrong formulas, but one thing I do know is it hurts a lot more the faster my shoulder hits the side of a van.
I hope OP knows this.

 

[wanda2010]

You guys lost me completely

 

[JoysOfSight]

While the impact might be worse, the faster you ride, the less likely you are to have a crash. This is because instead of bumping along at the side of the road with everybody overtaking you (and trying to decide if they can be bothered waiting or are just going to pull in/out across your path), you suddenly get to be part of the traffic flow.

Almost without exception, I have issues in places where I can't go fast (like uphill).

 

[gavintc]

While the impact might be worse, the faster you ride, the less likely you are to have a crash. This is because instead of bumping along at the side of the road with everybody overtaking you (and trying to decide if they can be bothered waiting or are just going to pull in/out across your path), you suddenly get to be part of the traffic flow.

Almost without exception, I have issues in places where I can't go fast (like uphill).

I completely agree. As I became more confident with my route and my pace increased to match that of the cars, I found I can dominate a lane, keep my position better and navigate difficult junctions more safely be being part of the traffic. Thankfully, I have only a shortish urban commute of around 8 km, before I hit the rural roads and can just get into a flow.

 

[jimboalee]

While the impact might be worse, the faster you ride, the less likely you are to have a crash. This is because instead of bumping along at the side of the road with everybody overtaking you (and trying to decide if they can be bothered waiting or are just going to pull in/out across your path), you suddenly get to be part of the traffic flow.

Almost without exception, I have issues in places where I can't go fast (like uphill).

On the occasions I've been bumped off ( can't vouch for anyone else, we could have a poll ), it has been vehicles emerging from the left and one car driver taking exception to me taking primary. We have established the car driver who put me up the curb was a very rare thing and not necessarily because I was in primary, although remembering the situation, it contributed.

The vehicles emerging saw me and drove into the carriageway, not properly assessing my speed. There were huge apologies and "didn't know you was going that fast".
Two cars from T junctions, and a van pulling out from a parking space.
In the case of the van, if I'd have been riding slower, I would have pulled to a stop before I hit it. In all three cases, it would not have mattered if I was in secondary. I was in the Dominant position because I was getting a stink on.

It has just now come to mind that I have been knocked onto the tarmac by a motor vehicle once per decade.

 

[Bollo]

Thanks for putting me right.

Would you agree that the faster Snailracer's tea cup hits a wall, the more small pieces it breaks into?

Is it the same for the human cranium, or will it just squidge because its inside a skin bag?

No formulas please, just a simple explanation to suit the intelligence of a cyclist who rides at 20 mph between stationary traffic.

I may have got all the wrong formulas, but one thing I do know is it hurts a lot more the faster my shoulder hits the side of a van.
I hope OP knows this.

Yes

 

[fossyant]

As for the 'more time at home' - the problem is the job, not the commute. 8.5 miles is a nice distance, not too short, not too long (in terms of time).

Anyway, what's all this rubbish about riding slow................. Fortunately I have limited my top speed (on the flat) to about 24-25 mph with a 74" fixed. Crack out the geared road bikes, and things get a bit "warp factor" in traffic.............

 

[fossyant]

It has just now come to mind that I have been knocked onto the tarmac by a motor vehicle once per decade.

That's good going that !!! Low hit count !!