Double or Triple chain rings ?

[4F]

Oh the old "trade secrets" line

 

[jimboalee]

OK,

18.75 mph is one fifth of a Horsepower on a 'straight arm sports' bike.

So FFFF, you are less than one horses leg

75 cadence is 'average' for a broad range of cyclists when climbing.

 

[4F]

OK,

18.75 mph is one fifth of a Horsepower on a 'straight arm sports' bike.

So FFFF, you are less than one horses leg

75 cadence is 'average' for a broad range of cyclists when climbing.

What size horse are you basing that on. Suffolk punch or a pony ?

 

[Fab Foodie]

Very interesting stuff I must say.

It's inspired me to try and work out the gearing on my new bike using the 'Sheldon Brown' calculator, but I'm having a bit of an issue with wheel size.

They're Rodi Airline Evo 700c with 31mm rims

Not sure what that translates to on the calculator. Do I select 700X32 as the closest?

I've never really put much thought in to wheel size before

I assume you mean the tyre size is 700x31c, so calculating for a 700x32 is more than accurate (all tyres of a particular size vary plus or minus a mm or so anyway).

 

[Ant]

I assume you mean the tyre size is 700x31c, so calculating for a 700x32 is more than accurate (all tyres of a particular size vary plus or minus a mm or so anyway).

Thanks

 

[Fab Foodie]

FF, I think tyred's explanation above is useful for getting a handle on jimbo's methodology. Your questions to jimbo are arguably in a different language. You're perhaps asking him to answer your questions in your language.

Anyone that's ever done any kind of translation work will tell you it's not always possible to provide an exact, or even adequate translation. In the absence of learning the mother-tongue (as it were), you'll just have to appreciate the beauty and take on trust!

That's as maybe yello, but putting up stuff as fact in a beginners forum should stand some scrutiny. Be terrible if somebody wrote their 'gospel' on say bike gearing or bike sizing or compatability between Shimano and Campag which was wrong and a newbie took it as gospel, spent money and found they'd made the wrong choice.
So, thus far there are those here who are challenging Jimbo's theories and hopefully the newbies here might be better informed as to whether to take Jimbo's advice at face value or ask more questions. Jimbo's theories might be valid and sound even vaguely plausible to the unscientific but he is unable to give us any validity.
Newbies beware.

 

[Crackle]

Except, I used to ride a regular mile and a half 10% and climbed it in a 37" gear at 55rpm, so it's close but not spot on. Unless of course the sign saying 10% was wrong and I had just come up a mile long 8% so maybe my legs were tired. i therefore am not an aveage rider

The infinetly variable cadence only works if you can restrain yourself from 'having a bit of a go' when you get to the hill, not possible I say, unless you stick a powermeter and cadence computer on your bike and watch them like a hawk.

 

[Chris James]

Except, I used to ride a regular mile and a half 10% and climbed it in a 37" gear at 55rpm, so it's close but not spot on. Unless of course the sign saying 10% was wrong .

Quite possibly.

The steepest hill immediately near me has a 10% sign on it. It is steeper than the one with a 15% sign on it, and the OS map shows it as one chevron (i.e. between 1 in 5 and 1 in 7, 14 - 20%).

I don't know why Jimboalee's calculation is based on a 10% hill. There are loads on my normal routes that are steeper than that.

Right back to the start of this thread it was obvious that there is no 'true' answer to gearing. It depends on the type of riding you do (racing, leisure etc), how hilly it is, how fit you are, and how much you much you like to keep in reserve in case you are having a bad day.

My limited experience of sportives (for example) is that lots of people are macho about how they have no need for a triple, but then push their bikes up steep hills.

 

[jimboalee]

Well said Chris.

It has amazed me just how argumentative people are. Even people who share the same interest.

The proof of the pudding is to go out and experiment with the various theories.

Up to now, I have forwarded a piece of my knowledge which was handed to me by a very able LBS man, which nominates the gear length you should have on your bike to get you up a 10%.
The logic is 'lower for heavier'; and after a bit of thought, 'lower for steeper'.

I have not seen any alternative scientifically based theories, except the one which is "Buy something, test it, find its crap, junk it and then go and spend more money on another bit of kit which might not 100% cure the deficiency" - the 'suck it and see' approach.

There is my other one which relies on the Sin of the gradient to apportion the power, but NO others.

My second theory is based again on stuff passed to me by an ex Pro and backed up by UCSC ( Uni California, Santa Cruz ) research.


Now go and measure some 10% hills and select the gear.

(The end of a 1m spirit level should be 10cm off the tarmac.)

 

[Crackle]

(The end of a 1m spirit level should be 10cm off the tarmac.)

That would make it 20% if you did that on a 10% hill

 

[jimboalee]

Uh!

1 in 10. 1 m rise every 10 m progression.

Oh, I see. You've got the wrong end of the stick again.

 

[jimboalee]

Oh BTW, there are a few 10% gradients near where I live that are not even signposted.

In fact, gradient indications are for the motorist when it's icey. Cyclists are 'not worthy' of spending council money on.

 

[4F]

It has amazed me just how argumentative people are.

Steve B has asked you some questions with regards to your calculations and rather than answering them you come up with the "trade secrets" line and then think others are being argumentative ?

 

[tyred]

This is where I fall down with this. I have never seen a signpost saying how steep a hill is. I understand the the maths behind saying if a hill is 1 in 4 or whatever, but I would never trust myself to just estimate how steep it actually is with any great accuracy and I have no inclination to go and measure them. People would think I really have lost my marbles this time.

Personally, the terrain is either level, steep, or bloody steep

 

[marinyork]

I don't mind jimboalee's formula's, I'd wish he'd just admit they aren't remotely applicable to the average cyclist and certainly not a beginner. If they were something to aim for rather than a baseline I think they'd be about right.