Can't cycle very fast downhill

[chucknorris]

Hi everyone,

I'm not only new here, I'm new to cycling. I like to run to keep myself fit but after continuingly injuring myself I have recently started cross training by cycling 2-3 times a week. At first this was only to avoid running too much but now I am beginning to get into it and enjoy it as much as running. However I am quite green as to the technical details of cycling.

I have become aware (or at least this is what I think, I maybe wrong) that my bike is not geared correctly. I have two bikes an old Giant border alu lite and a Dahon Espresso. I recently switched the tyres of the bikes (putting slicks on the Giant bike) with the intention of using the giant bike to commute to work and leaving it at the station (it's quite old so hopefully wouldn't be anyone's first choice to steal). I find the bike good for inclines but downhill the gearing is all wrong, I find that the pedals go around too fast for me to cycle any faster. I might be using the wrong terms here (if so please correct me) is this down to the 'chain set'? Do I need to buy another bike or is it possible to change the chain set for something that would still allow me to cycle fast uphill but also faster downhill?

[Ayesha]

Hi,

Pedaling a too fast 'Cadence' is called 'spinning out'. You must be going a fair whack to spin-out on even a MTB.
When this occurs, its best to let gravity pull the bike down the hill and give the legs a well earned rest; unless, that is, the bike is a fixed wheel.

Are you sure that wasn't a Giant Boulder MTB? 42 tooth front to 14 tooth rear is quite high for a MTB. 42/14 = 3, 3 x 26 = 78 in inch gear which is a comfortably high gear for declines.

You could investigate the possibility of a rear cassette with a 12 tooth smallest sprocket. Take the bike to your Local Bike Shop ( LBS ).

[531colin]

................. I find that the pedals go around too fast for me to cycle any faster. ........

The first question is, how fast is your "too fast" ?
Experienced cyclists usually use a "high cadence" , ie spinning the pedals at up to 90 rpm.

[[XAP]Bob]

................. I find that the pedals go around too fast for me to cycle any faster. ........

The first question is, how fast is your "too fast" ?
Experienced cyclists usually use a "high cadence" , ie spinning the pedals at up to 90 rpm.

When I'm racking up the speed I'll push (http://www.machars.net/bikecalc.htm) 120-130rpm on the pedals, I can't sustain that for long though.

I drive a 'bent (lying down) trike (three wheels), and this has helped up my cadence...

I'd expect a "newish" cyclist to be able to push 90rpm for a while, the way to increase that is to drop a gear relative where you would normally cycle and keep the cadence up through much of your journey. Higher cadences will tire your cardio system more than lower cadences, but your legs less... They also put less stress on knees etc.

[chucknorris]

Thanks for the replies guys:

It is definitely a Border alu lite.

I feel a bit stupid now because I went to count the teeth on the (thing that I don't know what it's called, is it the chain wheel?) and noticed although the gear shifter on the handlebar says 3, it was in fact stuck on the middle chain wheel, so yesterday I was in the wrong gear. Despite this my query is probably still valid because for weeks (in the correct gear)I have been experiencing the feeling that I could go a lot faster downhill ever since I started cycling about 6 weeks ago. However yesterday it was much more noticeable (can't believe I didn't notice that I was in the wrong gear). Anyway quickly moving on from my stupidity, I counted 42 teeth on the larger chain wheel, is this quite low? and should be improved upon?

As for the 'spinning' being new I haven't really got a feel for cadence but yesterday aside (which was blatantly over spinning) I have found that downhill it's not really worth spinning because I can't really add much to the speed most of (but not all) my effort is used up just keeping up with the spinning without adding any real speed to the bike. I think (guessing) I tend to cycle at about a cadence of around 90-100? but I don't find it an easy thing to judge. I only tend to cycle for about 55 mins (14 miles) as it more or less is the same effort as my 5 mile runs (40 mins, coming back from injury so expect improvement over the couple of months).

Thanks for the tip on targeting my heart and lungs over my legs, this is indeed what I want to do.

[Robert]

If your chainring has 42 teeth, and your smallest sprocket is 14 at 20mph your cadence will be about 86, at 25 mph it will be 107 and at 30 mph it will be around 130, given wheels at 26".

The easy way to know what your cadence is, is to use a cycle computer that shows your cadence.
Otherwise the formula is
1056*v/pi*d, where v=speed and d = gear inches - (no of chainwheel teeth*wheel diameter/no of sprocket teeth)

[[XAP]Bob]

Lots of wd40 in the ffrony shifter to loosen it up, and grab it and move it directly.
assuming that it is stuck, and not s cable sticking...

42 isn't large, but it spends what speed you feel you'd like to improve on.

[alicej]

If your chainring has 42 teeth, and your smallest sprocket is 14 at 20mph your cadence will be about 86, at 25 mph it will be 107 and at 30 mph it will be around 130, given wheels at 26".

The easy way to know what your cadence is, is to use a cycle computer that shows your cadence.
Otherwise the formula is
1056*v/pi*d, where v=speed and d = gear inches - (no of chainwheel teeth*wheel diameter/no of sprocket teeth)

BTW "chainrings" are the cogs at the front, attached near where you pedal. "Sprockets" are the cogs at the back, attached to your rear wheel. Largest chainring and smallest sprocket will = your highest gear.

The answer to "What's the right gear" questions usually seems to be (in the end), "Whatever feels good to the rider" Maybe if you say where in the country you're based we could try to recommend good Local Bike Shops near you who might be able to look at adding higher gears, if that's what you feel you need? It's probably not something you'd want to do yourself anyway.

[snibgo]

If I were you, I'd wait a month or so before making changes. Your ideal setup will depend on your cycling strength, which I'd expect to improve. You may not be able to exert much power at a cadence of 90rpm or more, but this will improve with practice.

You can get a computer with cadence, or get a feel for it at home with a clock that shows seconds (and ideally ticks once per second). Move you hands in a pedalling motion. When each hand does one revolution per tick, that is 60 rpm. Two revolutions per tick is 120rpm. Halfway between is 90rpm.

We are all different, but I usually pedal at 90-100rpm, with occasional bursts up to 130. That's just the way my legs work. Many cyclists who are stronger than me pedal slower. My top gear at 90rpm is 30mph. If I had a hill that pulled me faster than that, I'd let the hill do the work and rest my legs for the pull up the other side.

[[XAP]Bob]

Technically they are all sprockets, cogs have interleaving teeth.

[Robert]

Technically they are all sprockets, cogs have interleaving teeth.

Well you learn something new every day - but it's probably best to use words that are common to describe common things.

Returning to the OP, it's probably better to concentrate on how you're going on the flat. With the gearing you have, if your cadence is around 90 and you're riding at around 20 mph you'll be turning the pedals at around 90 rpm. That's a good cadence that will feel fast if you're not used to it. When I started cycling, on my commute, I tried to maintaing a cadence of 90 irrespective of the speed I was going at. I'd change down for hills and not worry about my speed.

[alicej]

Technically they are all sprockets, cogs have interleaving teeth.

What are they? I tried to look it up and can only find stuff about computers...

[Malaconotus]

I suspect your bike is really rather undergeared. A 42 tooth large chainring is at the low end (although common on mountain bikes) and it seems to be combined with a 7-speed freewheel with a smallest cog of 14 teeth. With 26" wheels the top gear is only 78 inches, and the slick, and possibly smaller tyres, may be exagerrating this further. (the wheel size affects the gearing, which is why penny farthings were the solution to going fast before gears were used on bikes)

That is low, but still higher than most people would use on a single speed bike (no gears), and with practice single-speed riders acheive over 30mph. It is always better for your knees (and your heart) to be spinning a low gear than mashing a high gear and you can spin faster the more you ride.

So the answer is partly practice, but most people with multiple geared bikes prefer a top gear of around 100 inches, which would make you 28% faster in top gear pedalling at the same cadence. The easiset way to achieve this would be to change the frewheel (the seven cogs at the back, which are a single unit) Something like this might well do the job on a budget... http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 0677609179 However, I don't know the full spec of your bike and whether that particular freewheel, with a very large big cog for a very low gear, will work with your set-up.

Your best bet, as suggested upthread, would be to take the bike to a local bike shop who can inspect the whole set-up and advise. It certainly should be possible to find and fit a new freewheel which gives you a higher gear range, although they may not have one in stock.

[thelawnet]

Thanks for the replies guys:

It is definitely a Border alu lite.

Pretty sure it's a Giant Boulder. It's a slow bottom-of-the-line mountain bike with cheap suspension, the gears aren't really the problem.

[531colin]

Technically they are all sprockets, cogs have interleaving teeth.

What are they? I tried to look it up and can only find stuff about computers...

I couldn't resist this.......


.........on Wiki they were even revolving!

brilliant....they do it here too!.............http://en.wikipedia.org/wiki/Gear BTW

I'm having a lovely play, the magic of computers is still fresh!!