Is this a bad idea? Will I notice the difference? I’m seeing a lot of compact cranksets for sale at 172.5mm and am wondering if it’s not a good idea to switch lengths…
Is this a bad idea? Will I notice the difference? I’m seeing a lot of compact cranksets for sale at 172.5mm and am wondering if it’s not a good idea to switch lengths…
My opinion is that you won’t notice a difference of 2.5mm. I switched from 175’s to 172.5’s when I went to compacts a few years ago, thinking I’d be able to “spin” them a little easier. I honestly can’t feel a bit of difference.
I’ve been told that your muscles don’t feel the difference in crank sizes if its 2.5mm but I’ve never tried it.
I did it, and I don’t regret it. Not sure about the compact crank part, but I went from 175 to 172.5 and it helped my knees. How tall are you? I am 5 10
Just remember that when you decrease crank length you’ll need to raise your seat. The seat goes up since the distance to the pedal at the bottom is now less then before.
I’ll be changing from 180mm to 175mm on the new bike. I’ve been riding 180’s for many years. It’ll be fun to see if there is a difference. The max crank length on the new bike is 175.
I did it, and I don’t regret it. Not sure about the compact crank part, but I went from 175 to 172.5 and it helped my knees. How tall are you? I am 5 10
I’m 6’2…
you won’t notice a difference. 2.5 mm is almost nothing.
that said, with your height, you probably shouldn’t switch from 175s to 172.5s, you probably should switch from 175s to 195s! most riders of your height (annecdotally) report significant improvements when switching to proportional cranks. because right now you are using (proportionally) tiny cranks. want some food for thought? take a few minutes to read this.
I did it a few years back…I am 6’2" with a 34" inseam. I like it.
Hi
I have tried changing crank lengths. My experience is to not mess around with fractional changes, 175 to 172.5 changes your circle by .5cm or ONE FIFTH of an INCH…
Shoot, dimensionally speaking, My morning to nite body height changes more than that…With the tides and the full moon it is probably more (I am 6-2 mostly)
From 1981 until 1984, I went direct from 170 to 180. Kept that on my whole fleet until a recent change on one test bike.
I just went from 180mm (7 inch lever) to 195mm (7 and 3/5ths inch lever) of crank…The rest of the previous set up carried forward un-altered (except to adjust for the bigger drop to the bottom pedal: Seat down 1.5cm, cockpit down same, personal pref dictated that I stay at same fore-aft of pedal circle) Your preferences can vary, that is why they are called “personal preferences”, after all.
54-40 q-rings, 11/23 or 25 cogset. Quark w-G705 ,custom alu cranks
Connected to an old, but beloved, stock geometried, Aluminium P3(56cm, aka"Grey Ghost")
I am now putting out 385W (from 362W) at 142hr/bpm(same) on my 2XTwenty test course.
Bodyweight and fat are same for now (YES! I am still a fat Bloated F-CK!)…it is 10 ride sessions since the change
More results to come…literally and figuratively(sp?)
A race: IMC 09-Here comes the re-match.
tp
Bald, Bloated, Boobed…but not for long
So it appears you have a choice between the conventional tried and true advice or the whacko, out there in left field advice.
Manufacturers makes cranks in 2.5mm increments because those increments work very well for the vast population of the cycling community. 5mm can be the difference between chronic knee pain and maximum performance for many people. If you could really throw on cranks that were 1.5cm longer, then why do we bother fitting bikes at all.
At 6’2", you are on the borderline between 175 and 172.5. Try the shorter cranks and see how they do for you.
Something to think about.
I go back & forth between the 2 sizes on several different bikes… 172.5 on my regular road bikes (x3), and 175 on my TT/Tri, MTB, touring, cross, and commuter bikes. Of course it’s impossible to isolate just the crank length from the rest of the bike geometry and my resulting position, but I’ve arrived at this point over many years of T&E, and I do feel like the longer cranks are better for more leverage at lower cadence while the shorter ones allow a smoother spin with less stress on the knees… pretty much the same explanation as classic conventional wisdom. So, I think the ultimate answer boils down to your preferred pedaling style or cadence range and then work back from there. Are you more of a spinner, or masher? Most folks I ride with are clearly one or the other, just watching them it’s obvious.
i would look at it this way. the most important angle in terms of leverage is your hip angle in it’s closed position. if you shorten your cranks by X, you can increase your armrest drop by 2X and achieve that same hip angle at top dead center. conversely, if you lengthen your cranks you must go with less drop. so, on balance, to the degree aerodynamics are of value you to, and assuming that a flatter back = smaller frontal profile = lower drag, well, there you go.
but power is a function of both torque and cadence, and you’ll have to ride your smaller cranks with a slightly higher cadence to make up for that marginal loss in torque.
so, if going smaller is better, why not go smaller still? big question right now. i think jim martin at U of Utah is saying down to even 145mm, and maybe even smaller, is fine. i haven’t tried it. it’s hard to try because it’s hard to find cranks that small. i mean, you sort of have to make them, i don’t think you can buy them.
in general, i’m a fan of going 2.5mm to 5mm smaller on the tri bike than on one’s corresponding road bike. i also think tri bike riding should on balance occur at a cadence 10 beats higher than road bike riding, and that’s esp the case if you go to a smaller crank.
Manufacturers makes cranks in 2.5mm increments because those increments work very well for the vast population of the cycling community.
are you sure that that is the reason manufacturers makes cranks in only a few sizes of just 2.5mm increments for riders whose sizes range enormously? if you are sure that is the reason, what is your source for this info?
then, if we used the (sometimes impaired) judgment of existing manufacturers as to what “works very well for the vast population of the cycling community”, we’d all still be racing triathlons on round-tubed bikes with 72 deg seat tube angles and with drop bars (without clip ons). no slight on them, but profitable manufacturers need to take a lot of things into account to survive, but what “works very well for the vast population of the cycling community” doesn’t necessarily take top billing. how about, costs vs. return on investment? and the list goes on …
Maybe there are a lot for or on sale because no one is buying them. Personally, I don’t get the whole compact crank thing. Well, maybe for cyclocross and unexperience or beginner cyclists who haven’t developed power yet.
Mr. AnDroid,
Am I out in left field? Not sure,as I do not follow stick and ball sports.
Am I, as you say… “a Whacko”? (well :)" That has been well documented," I resemble that comment. (with due credit to Groucho for a good quip. ;#)
The industry hands down arbitrary lengths because they have the CE and CPSC to worry about. Equipped bikes must pass certain ground clearance and overlap standards
I confess that I don’t know anything about fitting, the random world championship podium athletes I have positioned must have done well in spite of my ignorance.
In keeping with the Data or it didn’t happen mantra, I take time to provide some metrics for my example as I too have grown weary of the typical ST wonk talking about how he felt so much better because of this or that Delta in equipment.
Hopefully some day I can provide a more reasonable example that n=1, it is almost n=2 but I have not seen Mr H2oFun post in almost a month, he of the longer cranks than I, Where art thou, Dave?
How ever, in the mean time… this will have do for now.
You can all race on your desired equipment and find your own path, send the rest of us notes along the way, so that we might learn and , if need be, Find you when you totally lose the path!
Tom -
Curious… were you using Q rings on your old cranks when you established your baseline wattage #'s?
.
Amicable solutions are the best.
Hi M.H.!
I was indeed using the Q-rings on the prior set up…which was as follows:
Saddle midpoint at 79.5 degree, 82.25 cm seat altitude over BB spindle center, 19 cm of drop
54/40 Q-rings (Both set at position 5…established by feel, not watts, Because the popular 3/4 setting felt like the foot was falling thru at 4:25 on the clock…but stalling at 4:30)
Ran baseline for last 18mos, including IMC 2007 (where I was 7th age-grouper off bike, run was complicated by blood pooling in left lung, still finished, but lost the Kona slot, and had to be on blood thinners for a bit to ward off blood clots)
What are you racing this season?
Tom
Bump,
I stand corrected, and retract my previous angry rantings…
Perhaps the extra angular movement of my legs because of my new crank length has perhaps altered the rate of bloodflow to the upper and lower male brain.
Maybe I just like long cranks?
TP
Not as heavy as yesterday, but still searching for class
I think it is across campus.