170mm or 175mm cranks..will I really notice any difference ?

Darra8

Is it really possible to notice any difference between 170 and 175mm crank arms?

Cheers,

Steve

cougie

Not in my experience.

smegurmum

depends on what riding you do, and how low your bb is, ive found in my experiance that on certain bikes you can catch the arm on roots if climbing in woods

paul.skibum

No you wont notice the difference and you wont suffer from grounding the arm. Most bikes come with 175mm arms fitted.

Steve_b77

I've got 175mm on one bike and 170mm on the other, can't tell the diffrence

MacAndCheese

I'm sure the difference in pedals and the soles on shoes, and possible even the thickness of socks adds up to +/- 5mm anyways...I know the soles on my Vans are alot thicker that the soles on SPD shoes for example...I think it only really matters if your a pro trying to shave tenths off you times.

boz64

In terms of pedalling, you'd probably notice more of a difference on a road bike where seating position etc is more precise and you spend longer periods pedalling at a steady cadence. It's easier to spin shorter cranks... conversely longer ones are more difficult to spin but give more power.

Anonymous

MacAndCheese wrote:

I'm sure the difference in pedals and the soles on shoes, and possible even the thickness of socks adds up to +/- 5mm anyways...I know the soles on my Vans are alot thicker that the soles on SPD shoes for example...I think it only really matters if your a pro trying to shave tenths off you times.

Doesn't matter how think your shoes / socks are, your feet will still be describing a circle of 170mm diameter or 175mm diameter, depending on your cranks.

supersonic

As pedals get thicker, your foot traces an oval with the centre above the BB axle.

MacAndCheese

yeehaamcgee wrote:

MacAndCheese wrote:

I'm sure the difference in pedals and the soles on shoes, and possible even the thickness of socks adds up to +/- 5mm anyways...I know the soles on my Vans are alot thicker that the soles on SPD shoes for example...I think it only really matters if your a pro trying to shave tenths off you times.

Doesn't matter how think your shoes / socks are, your feet will still be describing a circle of 170mm diameter or 175mm diameter, depending on your cranks.

Yep, just re-thought that and turns outs I was talking utter rubbish as it would just move your pedelling circles/ovals higher or lower in relation to the BB, but wouldn't effect the overall size like a changing the crank would....not have a good few days for talking rubbish at the moment...And to think I did mechanical engineering as part of my degree.....I'll get my coat. :oops:

Anonymous

supersonic wrote:

As pedals get thicker, your foot traces an oval with the centre above the BB axle.

No it doesn't.
It traces a circle, displaced from the pedal axis by the thickness of your pedal and footwear.
(ignoring minor abberations caused by tilting your foot through the rotation)

supersonic

Ah yes, if your foot stays the same ;-)

But you are right.

Anonymous

Well, I used to have this problems where my feet turned into hooves at the start of the upward stroke, but luckily, I've overcome that now.

supersonic

Mine do weird things! One was when commuting to work in flappy trousers (even using clips) I developed this habit of riding on the outside of the right pedal with an angled leg.

I still do it sometimes unconcsiously!

Anonymous

I have trouble because of my insanely wide duck-feet.
I noticed the other day that my loosely done-up Vans were quite mis-shapen, because only about two thirds of my foot was on the pedal.
With the shoe done up tight, I hadn't hoticed.

supersonic

I got pretty wide feet too, and walk on the outside of the heel - wear shoes down fast when walking. Charie Chaplin style hehe.

rhyko7

i changed from 175 to 170 mm cranks on my bike.
the reason for this was to bash less rocks as i have a really low BB
i do hit slightly less rocks with the pedals, but didnt notice the difference in the pedalling diameter, doesnt feel any different to the 175's

Skonk

My SX Trail has 170mm arms where as my 3 other bikes all have 175mm.

I CAN tell the difference but it's not a huge difference (obviously the SX Trail is a very different bike to ride compared to the others anyway).

I did have an AM/XC bike a while back that had 170mm arms and again I could tell the difference, a bit more so than with my current bikes though. I felt it when riding up hill; the slightly shorter length meant a little less leverage and it did seem to make a difference.

Would prefere the longer arms on a bike I had to ride up hill a lot.

It could just be because I'm so unfit though 15 years of sitting on my arse and im now trying to make up for it at almost 30 years old.

Darra8

Thanks guys.

If there is no difference that what is the point in offering the 2 different lengths?

meesterbond

boz64 wrote:

In terms of pedalling, you'd probably notice more of a difference on a road bike where seating position etc is more precise and you spend longer periods pedalling at a steady cadence. It's easier to spin shorter cranks... conversely longer ones are more difficult to spin but give more power.

For those of a road persuasion, there's a time trialist called Michael Hutchinson (no not that one) - British champion and generally quite amusing bloke, but anyway, he writes in Cycling Weekly and one column addressed the issue of crank length.

Bear in mind that his time trial bike is set up to the milimetre for the optimum aero advantage etc etc he claimed that between 170 and 175mm crank length, he could tell absolutely no difference whatsoever... couldn't even tell you what lengths cranks were on his current bike.

If someone as fastidious as a pro timetrialler can't tell the difference, I reckon you're pretty safe...

Anonymous

meesterbond wrote:

If someone as fastidious as a pro timetrialler can't tell the difference, I reckon you're pretty safe...

Ah, but I'm an engineer, I could tell.
I'd measure them