What's the different between 172.5 and 175mm?

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What's the different between 172.5 and 175mm?

Postby rider_1 » Wed Jan 01, 2014 10:32 am

Guys,
I have a question in my mind about crankset,
What's the different between 172.5 and 175mm?
What will effect me if I use 175mm ? Currently I'm using 172.5

Any ideas ?

Thanks
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by BNA » Wed Jan 01, 2014 10:56 am

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Re: What's the different between 172.5 and 175mm?

Postby trailgumby » Wed Jan 01, 2014 10:56 am

I have 172.5 on the roadie and 175 on all the mtbs.

The difference in ability to put down torque.is only just noticeable. The difference on my lower back is very noticeable. Shorter is much better. Only 5mm difference in pedal circle diameter and seat is/was set at same height relative to bottom of stroke (changed slightly now due to running Speedplay zeros on the roadie) so quite surprised by the improvement.

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Re: What's the different between 172.5 and 175mm?

Postby jimsheedy » Wed Jan 01, 2014 11:04 am

I changed from 172.5 to 175 about 3 years ago. The difference was outstanding. I was able to put down a lot more power more easily for longer. I guess it depends on your height or even leg length though.
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Re: What's the different between 172.5 and 175mm?

Postby rider_1 » Wed Jan 01, 2014 5:26 pm

I'm 176cm which one is better ? thanks
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Re: What's the different between 172.5 and 175mm?

Postby trailgumby » Wed Jan 01, 2014 5:31 pm

I'm 185cm and find the 172.5 to be an improvement.

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Re: What's the different between 172.5 and 175mm?

Postby GAV!N » Wed Jan 01, 2014 5:34 pm

Measure the inside of your leg, it's not necessarily your total height that counts. There are simple calculators online to then convert to your most suited crank length.
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Re: What's the different between 172.5 and 175mm?

Postby jimsheedy » Wed Jan 01, 2014 5:36 pm

I'm 192 and find the 175 to be an improvement
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Re: What's the different between 172.5 and 175mm?

Postby RonK » Wed Jan 01, 2014 5:38 pm

The difference is 2.5 mm - bugger all. I regularly ride bikes with 170mm, 172.5mm and 175mm cranks. The difference is all but imperceptible.
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Re: What's the different between 172.5 and 175mm?

Postby jimsheedy » Wed Jan 01, 2014 6:29 pm

not in my opinion. I also have a track bike with 165 cranks . very noticeable difference. a few mm difference in seat height is very noticeable too so why not cranks?
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Re: What's the different between 172.5 and 175mm?

Postby trailgumby » Wed Jan 01, 2014 6:39 pm

I'm with Jim. When you ride a lot (8-12+ hrs/week) you do.notice small changes. At least at first. Then you settle in. With some things.

Seat height though is not one of them. I.am quite fussy about that due to my history with lower back pain.

The shorter cranks help with that for me despite the flatter lower position because my knees don't come up so high.

You may be different. However with your smaller stature I would think smaller would more likely suit you better.

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Re: What's the different between 172.5 and 175mm?

Postby trailgumby » Wed Jan 01, 2014 6:44 pm

Interestingly I notice the 2.5mm reduction less when I go to the roadie than the increase when I go back to the mtb.

For about 15 minutes. Then I'm too busy picking lines to give it any further thought. ;)

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Re: What's the different between 172.5 and 175mm?

Postby jimsheedy » Wed Jan 01, 2014 7:06 pm

The real difference in longer cranks for me was on the flat.
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Re: What's the different between 172.5 and 175mm?

Postby Nobody » Wed Jan 01, 2014 7:30 pm

I've got an inner leg measurement of 80cm and use a 165mm. But I'm middle aged and have knee issues. What crank works best has to with what existing problems you have, if any, and how old you are. As you get older, you may find your tolerance for longer cranks gets lower. I can notice different crank lengths.

Advantages of smaller cranks:
Faster acceleration
Less pedal strike
Less toe overlap with front tyre
Less heel strike with panniers
Can allow for more aero position

Advantages of longer cranks:
Usually better time trial performance (depends also on aero of the individual).
Better climbing performance

In the end, it's best to get cranks that suit your inner leg the best IMO.
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Re: What's the different between 172.5 and 175mm?

Postby warthog1 » Wed Jan 01, 2014 8:18 pm

I am 184 cm and find 175s best on the roadie. I use 177.5 on the tt and was faster on a timed course compared to 175 back when I lived where the cycling clubs weren't allergic to anything but crits and handicap road races ad nauseam :x
Tried 177.5 on the roadie recently and have gone back to 175. Slightly slower on a 18 min timed strava climb.
172.5 didn't work for me but I haven't got much of a sprint, if you can sprint maybe slightly shorter is better.
Sorry for the completely inconclusive answer :roll: but that is what I've found for me.
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Re: What's the different between 172.5 and 175mm?

Postby nickobec » Wed Jan 01, 2014 10:39 pm

I am 184cm tall (and over 50), and ride a mix of bikes with different crank lengths:

at 175mm are my two TT bikes (one was supposed to be climbing/race bike but got put into service as TT bike after problem with other TT bike)
at 172.5mm are my race bike, training bike and commuter
at 170mm are my crit bike, single speed and old school late 8Ts 6 speed
at 165mm are a pair of cranks in the shed, I tried once on the single speed and never again.

Most of my bikes came with 172.5 cranks, so that is what I used. Bought a TT bike, that came with 175 cranks, found out that worked well for me, steady low cadence (80ish) = good power & good speed from me.

Started building crit bike, decided to experiment with 170 cranks, liked them because I find it is easier to accelerate, my cadence is around 100 and actually found out I do have a half decent sprint (something I had trouble with 172.5 cranks was that snap or sudden burst)

Next road race season I will experiment with using both 170 and 175 cranks to see how I go.

My singlespeed is based on an old Repco Olympic 12, it came with 170 cranks and I am comfortable with them, even though the gearing 52/16 is probably better suited to 175 cranks. The time I tried 165 cranks it just felt so wrong.

What I am trying to say is different crank lengths for different purposes works for me. If I can find a 177.5 I might try that on a TT bike, I might also try 175 on my singlespeed. Will see what is best for longer road races 170, 172.5 or 175 later this year.
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Re: What's the different between 172.5 and 175mm?

Postby rider_1 » Thu Jan 02, 2014 12:53 am

How can I know my inner leg measurement? Is it from my hip to my toe ?
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Re: What's the different between 172.5 and 175mm?

Postby warthog1 » Thu Jan 02, 2014 7:35 am

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Re: What's the different between 172.5 and 175mm?

Postby KGB » Thu Jan 02, 2014 8:45 am

Stand against a wall, wedge a book up to your junk, step away from the wall and measure from the top of the book to the floor.

I'm 170cm and have always ridden 165mm on the track and 170 on the road. Pretty sure my mtb is 175 but I'd also use a much lower cadence offroad. I tried 175 on the TT bike last year but have a pretty low position so found it restricted me a bit - I'll do some more testing this year with 170 on the TT setup.
I can't really tell a difference changing 2.5mm .

Whatever you read, take as a guide. Height alone is not a good indication. Other factors include ratio of upper to lower leg length, flexibility (esp lower back and hamstrings), preferred cadence and probably other stuff I can't think of right now.

Maybe find someone one here with some spare cranks that would be willing to do a temp swap so you can try it out?
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Re: What's the different between 172.5 and 175mm?

Postby Ross » Thu Jan 02, 2014 1:36 pm

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Re: What's the different between 172.5 and 175mm?

Postby Xplora » Fri Jan 03, 2014 10:27 am

If you can get comfortable with 172.5 cranks, they are a MILLION times easier to get second hand. I use 175s at 187cms tall and I really really struggle to find compacts on Ebay, let alone powermeters. My PM was the first and only one that was a half decent cost.
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