Cycling UK Forum

Hill Lover wrote:In retrospect, bringing up the issue of the helmet was a mistake...

Super; let's all move on now - take the h****t stuff to the appropriate forum. Bygones!

Trigger wrote:I didn't intend to mislead, I'm by no means turning it over "once every lamp post" and I'm not grimacing slogging it out up hills in the biggest gear.

Then you should really give us some figures. All the useful debate so far has been in quite general terms; we can't diagnose your specific problems without some hard facts.

Hill Lover wrote:DavidT; I agree with your comments re. helmets as the topic is past it's sell by date. Hopefully anyone reading this topic will focus only on the positives of my comments and not get on about helmets.

I'm glad you're Ok and typing stuff here. And it's nice to hear about all the good samaritans.

But if you didn't want people to discuss your views on helmets, why bring them up?

You do need to understand power to understand the requirements for cycling.
F=ma is useful for acceleration, but does not tell you about what steady speed you can maintain (because a=0 ! )

In old skool terms, look up "Work Done = F x d (distance) " You could calculate the work done against wind resistance this way, but ultimately you'll end up at the same place:
Power = force x speed

In any decent wind you can ignore rolling resistance and still get roughly the right answer.

( Cyclists are limited by power for any given time period. The force we generate at the hub is affected by gearing, which makes everything more complex - so power is key. Ask a time-triallist, or Dave Brailsford. )

This may reflect my bias towards higher revs, but:
I think of twiddling as too big a cadence.
Spinning as "just right".

Too low a gear and you can't put out much power, but at least it's easy on the muscles! "Twiddle" has a sort of light-hearted sound to it that suits this.

Trigger wrote:I know this is considered bad for the knees, but if I suffer no ill effects is there any reason not to stick with it? I find going up hills in the big ring slowly turning the cranks over much easier than spinning in the middle ring and getting out of breath. I did a steady 60 odd miles on Saturday and felt like I'd hardly done anything when I got home, my previous higher cadence rides left me quite tired.

You may not know what harm you're doing until it's too late. Personally, it seems common sense that higher stresses on the joint will lead to more problems.

If you're tired at higher cadences, I expect it's because your muscles aren't adapted to it yet. Beginners might find the same thing, as walking is done at much less than 80rpm. Maybe runners have a different experience?

It seems crazy to think that low cadence is best for many people, when almost no professionals find this to be the case. But they're your knees, not mine.

I had the SPD/Platform type on my commuter bike for a year.

They were pointless - "doublesided SPD" M520s make much more sense. Here's why:

You can ride fairly well in normal shoes on an SPD pedal. If you want to ride any distance, it becomes worthwhile to put your cycling shoes on anyway => there is no benefit to the "platform" side.

Someone mentioned taking their bike on holiday and forgetting their shoes. I admit I've never tried this! But then I've only ever had my cycling shoes with me on a cycling holiday :smug:

Headwinds aren't additive - at least not as I understand the idea. So if your top speed (in still air) is 16mph on the flat, you should be able to manage more than 8mph against a 8mph headwind.

Imagine a 16mph headwind - this would be very strong, but the rider above would be able to move slowly into it, rather than be stopped completely dead. Now the science bit ...

It's because Force and Power are different. In a headwind, the air resistance force goes up with the square of the airspeed, so [v_rider + v_wind ] ^2

But power = force x speed. That's speed of the rider NOT the air (or wind). So, if you ride at 8mph into a 8mph wind, you get
Power = k* [8 + 8] ^2 *8
[k is some constant number that you can get from the equations pages earlier]

Whereas riding at 16mph:
Power = k* [8 + 8] ^2 *16
So that is twice the power needed at 8mph into an 8mph wind.

Someone else can work out how fast our rider COULD do into the 8mph wind! Rolling resistance does have some effect, but if we looked at - say - a 30mph timetriallist we could create conditions where RR almost disappears from this scenario.
[I haven't written this stuff down for 20 years, so am very receptive to corrections]

If you have a front-shifting disaster*, it is much nicer to be stuck on the middle ring of a triple than on either ring of a compact.

I think this argument is in favour of a triple irrespective of range, preferred speed, etc etc...

[OT: The Pros need a narrower range than us mortals - over the same parcours - cos gradients slow them down less, but friction has almost a big an effect on their top speed.]

*broken cable seems most common in my compadres

songsforpolarbears wrote:100?!

So how am I expected to fix mine?! Where do you start? Should you check certain possibilities first?

Fortunately a lot of them are things that don't just happen overnight. (e.g. frame spacing not matching wheel!) It's a lot easier to diagnose a problem on a bike that was working fine 5 miles ago, than if you fit a transmission from scratch and it doesn't work.

Or if you fit a new cassette, you probably won't make the BB loosen. etc ...

I have a 10sp Centaur from a similar setup with just a few 100 miles on it. PM me if interested.

You might also wish to fit mudguards ...

CJ wrote:...
Check out the two photos below. Pay particular attention to the relationship between the side pivot of the dual-pivot brake and the top of the tyre. In the bike with clearance, the fixed part of the brake containing this pivot is entirely above the tyre. In the bike without it isn't. The bikes in these photos are both specified with 23mm tyres. If you're looking at the photo of a bike that comes with 25mm or 28mm tyres, the top of the tyre might be a bit higher than that part of the brake even though it's a 57mm model, but it should still be lower than the centre of that pivot.

Clearance.jpg

Note that the brake blocks in both photos are almost at the bottoms of their slots. This means that both frames have been made carefully, to exploit the full potential clearance of the model of brake for which each is designed. This is especially important when the user wants to fit 25 or 28mm tyres to a frame with 57mm brakes.

Nice one Chris. That makes frame-shopping a load easier.

thirdcrank wrote:AFAIK, one of the main reasons that clear winter skies = very cold weather is that the lack of cloud cover means that the radiant heat of the earth goes straight out into space with nothing to reflect it towards the earth. With mind in fully open position, I'm prepared to stick my neck out and say that cold only exists as an absence of heat.

I think I'm with you here. Heat is very different to current flow, because of that awkward obstacle absolute zero.

Or to put it another way; as things get colder, they move about less. You can't move about less than not moving!

Describing cold as radiating anywhere is just likely to reduce the layman's comprehension.

thirdcrank wrote:I'd pay a lot more attention if they identified a survey population of people who had given it a go and having shelled out for a bike had given up.

IMO It would throw up a lot more of the: it's too far (people commuting 10+ miles each way); my employer is (at best) unco-operative (at worst) downright obstructive; my partner thinks it's too dangerous; I have a company car and my job involves a lot of travel using that car; I couldn't stand the hassle, especially the aggro of every kind from so many drivers.

The reason I like this is that it should filter out a whole load of self-interest bias.

Would increasing fuel-tax get me on my bike? Hell no ( I don't want any more fuel tax!)
Would more traffic cops get me on my bike? Hell no ( I don't want a speeding fine!)
Would more infrastructure get me on my bike? Absolutely (that should get lots of cyclists out of my way).

Spot on thirdcrank!

You would think it wasn't rocket science to realise this, but ...