Cranksets?

adodsk

This is a daft one for Friday. Just wondering if there are any differences physical/mental between using standard/compact cranksets?

What I mean is, if I train on a Compact during the week do my legs and brain get into a certain rhythm which may be different to that required to use a Standard at the weekends?

blorg

I doubt it, you still have the same gears excepting 1 gear at the top and bottom end. Same would go for different cassettes... I have everything between 53/39 11-23 and 50/34 12-27... plus multiple fixed gears at different ratios.

Makes sense to vary your gearing according to the terrain and the sort of cycling you will be doing.

lescol

The tendency would be to select the gearing to suit the terrain/cadence so compact/standard would not, in most cases, make any difference. Having both I still prefer standard, although I'm getting more accustomed to the dramatic gearing change on going from the 50 to the 34 which usually, for me, means left 1 click, right 2 clicks in quick succession.

Mosiki

While on the subject of cranks - would i be right in thinking that a shorter crank will increase cadence somewhat?

If so is there an optimal ratio between someones leg length (or persons height) and crank length?

blorg

There is a correspondence between leg length and crank, yes, longer legs = longer cranks. It is debated how much it matters... it effectively changes your gearing on any given chainring/sprocket combination.

There is some research out there to suggest that changing between crank sizes doesn't help, e.g. if you train on one crank length you will tend to race better on the same crank length and worse on something different.

It is easier to spin shorter cranks at a high cadence, yes, this is one of the reasons they are used in track sprinting. You have less leverage though with a shorter crank.

Lumen

Mosiki wrote: »

While on the subject of cranks - would i be right in thinking that a shorter crank will increase cadence somewhat?

At a given cadence a shorter crank means lower foot speed, which (all things being equal) is easier to achieve. So your highest cadence (at low load) is likely to be crank length dependent.

For a given power output and cadence a shorter crank will require greater pedal force (and increase loads at the knee, at a greater angle).

Theory aside, on a bike with adequate gearing it doesn't really make much difference. Some people just prefer longer or shorter cranks.

Mosiki wrote: »

If so is there an optimal ratio between someones leg length (or persons height) and crank length?

Not that anyone can agree on.

Mosiki

I ride 172.5mm cranks, and thinking they are a little long for sprinting purposes (cant get high enough cadence). I'm 5'9 with 32" leg. Anyone ride bigger / smaller length cranks?

Edit: I guess the flip side is cruising at similar speeds with lower cadence (with longer cranks) ??

Lumen

Mosiki wrote: »

I ride 172.5mm cranks, and thinking they are a little long for sprinting purposes (cant get high enough cadence). I'm 5'9 with 32" leg. Anyone ride bigger / smaller length cranks?

Have you seen this?

lukester

Given that we're on a crankset free for all, (and I know this has been covered somewhat before) would anyone here consider a compact for racing, say with an 11 as smallest cog?

I know you're unlikely to spin out in a compact, just wondered if the gearing gaps for front shifting on a compact could prove a hassle in a race.

I ask because next bike upgrade/purchase would be something a bit better than current ride, but would be my one 'good' bike, so also to be used for hilly sportives, etc. I could conceivably get away with a standard double with a 27 at the back, as discussed recently on Lumen's thread, but I'm ~80kg, which is much heavier than his good self.

blorg

I raced all last year on a compact with a 12-27 as I wasn't arsed changing it for the hilly stuff (Sierra Nevada, Alps, Pyrenees.) It was fine. I wouldn't suggest it if you didn't have a bike already, a standard is certainly more optimal for racing, but it isn't a big deal. I certainly never spun out on 50-12. 50-11 of course is a bigger gear than 53-12 but if you consider that the pros are OK on 53-12... The abrubt shift between the rings is more of an issue than spinning out.

If I could only have one bike/chainset for everything I would go for a compact, no question.

niceonetom

I'm thinking of sticking a 110bcd 39t inner ring on my compact crank for racing. That, with my 11t cog should give me very nearly the same range as a standard chainset with (I'm guessing) even better front shifting. The only downside I can envision is that the jump from 50x12 to 50x11 is bigger than the jump from 53x13 to 53x12 in percentage terms so at high speeds I wouldn't have quite the precise control over cadence a standard would offer. A ring is significantly cheaper than a crankset though.

I'm on a 172.5 crankset btw. Does that seem a little short for a 82cm inseam?

I'd like to try a 175 to see if I might be a little better on it. My fixie has 170s and I certainly find them easier to spin at 120rpm+.

lukester

blorg wrote: »

.. The abrubt shift between the rings is more of an issue than spinning out.

If I could only have one bike/chainset for everything I would go for a compact, no question.

It's the shifting at the front that I'd be most concerned about. For most races it probably wouldn't be an issue, but for anything lumpy where you might have to shift at the front a fair bit, faffing around with shifters trying to find the correct ratio isn't going to be fun. How did you find front shifting at race pace?

@NOT Interesting proposition, in terms of how it affects front shifting.

Murph100

I've just switched from a Compact, and I definitely prefer the front shifting on the Standard, less drama moving down to the 39.

blorg

lukester wrote: »

It's the shifting at the front that I'd be most concerned about. For most races it probably wouldn't be an issue, but for anything lumpy where you might have to shift at the front a fair bit, faffing around with shifters trying to find the correct ratio isn't going to be fun. How did you find front shifting at race pace?

I think I shifted about twice all season but to be honest if you are used to a compact it is not that bad, you just do the back at the same time.

No question a standard is superior, I just wouldn't say it is necessary before you enter your first race.

ROK ON

niceonetom wrote: »

I'm on a 172.5 crankset btw. Does that seem a little short for a 82cm inseam?

On the basis that you are somewhat taller than me, then maybe yes. I use 172.5.

Murph100

You'll waste more time & life trying to find a consensus on crank length, believe me

Some are proponents of ' shorter is better ', others say it's determined by your leg length, others say its strictly dependant on femur length ( try measuring that to within 2.5mm !! ) and a lot say it depends on your riding style, spinner or masher.

To add to all the confusion, some advise that if you have any knee problems you should knock off 5mm, are over 40 knock off 2.5mm and a whole list of other crap.

I gave up in the end and went for what I was used to, 172.5mm, despite having an 88cm inseam. I cant see 2,5mm making much of a difference and certainly not an excuse for getting dropped.

niceonetom wrote: »

I'm on a 172.5 crankset btw. Does that seem a little short for a 82cm inseam?

blorg

2002, haven't heard anything since...