gear speed

[meth24]

Hi, I'm new, been riding seriously for about 3 weeks or so, just every now and then before that. I have a hybrid (2000 Specialized Crossover) with 48x38x28 front and 11-28 7-speed in back. All of the advice here and whatnot seems to be using 53's and 39's, but I pretty much only use the middle 38 up front right now. With that one and the 5th down which I think is a 15 on back I can cruise on flatlands around 18mph. When I switch up to the 13 I can cruise over 20 if my legs are feeling frisky. Is this too much of a cadence or am I doing fine?

I never use the 28 and rarely use the 48 (this I have only used on roads with slight downhills going around an average of 25-27mph).

 

[infinitive one]

i have only been riding seriously for about 2 weeks and on a flat not sprinting on a reasonbly high gear i can go at 25 mph plus
sprinting up to 31 mph and down hills 33 mph but i have a powerful build so that helps

 

[coolworx]

Originally posted by meth24
Hi, I'm new, been riding seriously for about 3 weeks or so, just every now and then before that. I have a hybrid (2000 Specialized Crossover) with 48x38x28 front and 11-28 7-speed in back. All of the advice here and whatnot seems to be using 53's and 39's, but I pretty much only use the middle 38 up front right now. With that one and the 5th down which I think is a 15 on back I can cruise on flatlands around 18mph. When I switch up to the 13 I can cruise over 20 if my legs are feeling frisky. Is this too much of a cadence or am I doing fine?

I never use the 28 and rarely use the 48 (this I have only used on roads with slight downhills going around an average of 25-27mph).

I'd say you were doing more than 'fine'.

Let's do some math, shall we?

A 38/15 gear ratio on a 27" wheel gives us 68.4 gear-inches, which translates to about 215 inches of travel (68.4 * pi) for every revolution of the cranks...

Ok, now 18mph is .3 miles per minute - or about 19,000 inches per minute. Divide that by the 215" per revolution, and your cadence is a very respectable 88!

 

[meth24]

Originally posted by coolworx
I'd say you were doing more than 'fine'.

Let's do some math, shall we?

A 38/15 gear ratio on a 27" wheel gives us 68.4 gear-inches, which translates to about 215 inches of travel (68.4 * pi) for every revolution of the cranks...

Ok, now 18mph is .3 miles per minute - or about 19,000 inches per minute. Divide that by the 215" per revolution, and your cadence is a very respectable 88!

Wow, thanks for giving me the formula too. I should have a lower overall cadence though since I pedal slower up hills and down hills, but most aren't too steep.

 

[coolworx]

I should have a lower overall cadence though since I pedal slower up hills and down hills, but most aren't too steep.

Nahhh... you should gear down and keep up your cadence.

Those fast twitch muscles (when properly trained) will allow you much more efficient and longlasting horsepower.

Lance has learned the joy of spinning an easier gear.... That's what all that offseason MTB training was all about.

You should be shooting for a 100rpm natural rhythm.


Here's a real 'Math Intensive' site on the subject:
Why bikes have gears

 

[meth24]

Originally posted by coolworx
Nahhh... you should gear down and keep up your cadence.

Those fast twitch muscles (when properly trained) will allow you much more efficient and longlasting horsepower.

Lance has learned the joy of spinning an easier gear.... That's what all that offseason MTB training was all about.

You should be shooting for a 100rpm natural rhythm.


Here's a real 'Math Intensive' site on the subject:
Why bikes have gears

I love math, thanks for the link. Right now I just can't keep stable on the bike with a higher cadence while standing up during short uphills. I'll try varying it.

 

[VeloFlash]

Originally posted by coolworx
I'd say you were doing more than 'fine'.

Let's do some math, shall we?

A 38/15 gear ratio on a 27" wheel gives us 68.4 gear-inches, which translates to about 215 inches of travel (68.4 * pi) for every revolution of the cranks...

Ok, now 18mph is .3 miles per minute - or about 19,000 inches per minute. Divide that by the 215" per revolution, and your cadence is a very respectable 88!

Your formula is correct except you have made the presumption that 27" wheels have a 27" diameter (and the exact same wheels are known in metric as 700 - but 27" converts to 685mm).

Here is a calculation website -

http://www.aussiecycling.com/cycling/gears.cfm

That website states -

"Note that in many cases nominal wheelsizes (eg 27", 700c) are not the real dimensions, so the only way to be sure of your wheel diameter is to get your tape out and measure it, and don't forget to include the tyre."

But it is preferable to measure the circumference by rolling it out with the weight of the rider and tyres inflated to normal. The rider's weight will compress the tyres and reduce the roll out

 

[meth24]

It's fine for a rough figure for me though, when I get going more into it I'll get a computer with cadence.

I did ride a lot better today by understanding that it's okay to stay in that gear for going around 18-19mph and tried the advice here for going up hills. Helped a lot, conserved more energy and didn't lose any speed. Oh yeah, adjust my seat position up some from the posts here too. Just need to get a ***** pack to hold an allen wrench pack.

 

[zaskar]

same thing i was wondering, im some what of a convert mtb
and have my 1st rd bike i mostly ride in the 39 gear,
and have riding speeds between 16- 25 mph anything
faster then 25 mph i have to get on the 53 then its
27-40mph @ 40 i seem to run out of gear,.

what about you guys, how fast can you go on the 39
also i dont let my chain dog track or what ever the
name is for incorrect gearing.

 

[M2cycler]

next time you ride, just look at ur freakin watch and count the revs

 

[coolworx]

Originally posted by VeloFlash
But it is preferable to measure the circumference by rolling it out with the weight of the rider and tyres inflated to normal.

I agree wholeheartedly - for instance my weighted roll out measures 2197 mm, which translates to a '27.54" wheel'.

But I was just going over the horseshoe/hand grenade method.
;-)