Post edited 6:54 am - November 19, 2009 by Mark G

Matt Schofield said:

are turbo-trainers any good? i'm thinking about getting one but I don't know much about them or what spec to look for in one

Hi Matt How are you getting on with the turbo trainer I lent you?

Re. an earlier post….

Running is now not a proplem - Great.

Mandy (my partner) has now said “Of course I will support you if you want to do the London Marathon”

How could I fit this in with my training for CYCLE road racing?

Should I bother?

Are the two disciplines that far from each other that it cannot be done.?

It sounds a silly question but I was looking at TT tri-bars and would a tri-bar that says it will fit a 31.7 mm handlebar fit a 31.8mm handelbar?

coach…. are rollers any good for you other than improving balance?

thank you.

So its dark nights and colder weather.  For most road riders this is the time to get the best bike cleaned oiled and greased so it can be put away until spring next year.  This saves your best bike from the rigours of wet and salty roads which cause havoc with your bike components.

Also if you have any small mechanical problems on the best bike get them sorted now before you put the bike away so that you dont forget about them over the winter.

Tom has started the winter clothing thread already and is thinking about getting wrapped up a bit more!  One thing when you are out winter riding don't be fooled into thinking you need less hydration.  You can lose the same amount of water in winter and under that warm clothing you can easily lose a bit more…so keep drinking well!

Debbie's got a 15in Giant 29er on test at the moment. So not just taller folk.  Have a spin on it. 

But I've probably derailled this thread enough. If you listen to Mark, you will go faster, cos he'll fine-tune your engine. If you listen to me, you'll just end up ****ing around with your bike. But hey - it might work.

Tommo said:

Feel is the most important factor when you're on the bike don't forget that.

I agree.

I'm not saying shorter cranks are THE answer. Just an answer. 

On the other hand, longer cranks aren't a free lunch way to produce more power. If you like 'em and if you're not planning on a particularly fast cadence, go for it. But to test it, go up by 5mm at least. 2.5mm either way is pretty much irrelevant (apart from a small effect on saddle height). Even 5mm isn't that much. We routinely make that jump going from a road bike (170mm) to a mountain bike (175mm) and most of us barely notice. 

I've used 180mm cranks on a singlespeed mountain bike and I found them awful. They really messed up my cadence when I was spinning. I swapped to 170mm and put on a sprocket that was one tooth bigger. (That is, reduced the effective gear, which is all that you're doing by using longer cranks.) 

On variable gears, you can - and I would argue, will - adjust your cadence and/or your gear to suit your crank length. So if you're not careful, it can be a zero sum game, e.g. you'll stay on top of that high gear and it'll feel easier, but you could be pedalling slower. So power output - and speed - is the same. Mark well Mark's words about power, further up.

I'm on 167.5mm cranks (no particular reason - they came on the bike) and am looking to reduce them further. When you're chained to your one gear choice, you sometimes have to spin. I can't do that so easily on longer cranks.

No particular conclusion to all this, though - except to experiment and find out what works for you. I think most top TTers are wrong to use longer cranks (I think they've just got better engines). But the evidence so far is arguably against me.

But just you wait! In 10 years, everyone will be on 160mm. Or 150mm. And probably 29ers when they're riding off-road.

If not, I'll be the first to admit I got it wrong.  Meantime, boo to the norm!

Post edited 12:28 am - October 30, 2009 by Dan Joyce

Longer cranks can feel nice because what they do, in effect, is lower your gearing. You've got more leverage to get the same gear around, so you don't have to strain quite so hard on the pedals. But as Mark rightly says, going faster is about cadence and gearing - not just pushing bigger gears. And it's harder to get a fast cadence with longer cranks than shorter ones. 

Also, the big issue for time triallists is aerodynamics. With shorter cranks, you get to raise the saddle relative to the handlebars - so you're effectively lowering the front end of the bike a bit. Going from 170 to 165 wins you a 5mm relative drop in bar height. It also give you 5mm more room between your knees and your chest on top of that, so you can drop the bar height by another 5mm without having your chest thumped by your knees - a net gain of 10mm at the front of your bike. If you can push the shorter cranks around as fast as the longer ones in a given gear, you should go faster cos you'll be a bit more aero (actually, you'd be going the same speed but you'd be using less energy!). Last year's BAR was won on 165mm cranks. 

I fancy having a go on some 150mm cranks…

Cheers Mark - 180's it is then (840×0.216=181.44)

Seems a bit scary long so might go for 177.5's - I've been on 172.5 since I started so we'll see ???

Might as well jump over 175's a make a more obvious change, keeping my old cranks as a back up.

Tommo said:

Coach - 172.5, 175 or 177.5 ??? and the reasons behind the answer.

(5ft 11in with slightly longer legs than the height would sugest)

Cheers

There are a number of suggested ways to get an ideal crank length this is generally based on the fact that longer legged riders will need longer cranks the most common calculation is:

inseam in mm x 0.216 = crank length

BUT the outcome may give you a crank that is not readily available so choose a common crank length nearest the calculation.  Remember change in a crank length will mean a change in saddle height as well.

The length of the crank can also relate to the type of riding you are doing so longer cranks means less force to push the same gear ratio  but you will find it harder to get a faster cadence. Therefore longer cranks would generally be good for time trialling and shorter cranks good for quick accelerations in road races and track. 

So for you Tommo measure your inseam and see what you get - I would guess you would be wanting around 175 or 177.5 for Time Trial.