Bike fit trends - specifically in crank length, handlebar width, reach and stack..

wafter

Über Member
Location
Oxford
Inspired by watching the video below along with some of the others in this series and from different content creators. FWIW I like Francis Cade's stuff - him and his crew seem like decent folk and his mate James (in the video below) seems to know his stuff..



Anyway, as most will probably be aware a "medium" road bike usually comes with 172.5mm cranks and 420mm wide bars. There appears to be a move towards shorter cranks now in many circles to "open up the hip angle" and reduce knee angularity; which is repeated in this video.

Bar width is also covered; the suggestion being that most bars are too wide and should be shoulder width for best comfort (wider can't help with aero either, I guess). I've always thought I had reasonably broad shoulders (rightly or wrongly) however using the measurement process shown in the video they're apparently around 380mm wide (effective); suggesting I'd benefit from a set of bars 40mm narrower than those commonly available on bikes "my size".

An interesting point is also made about most bikes being too large; suggested as being the result of effective frame sizes remaining the same over the years, but stems lengthening; meaning that for a given frame size a modern bike tends to be more suitable for a larger rider.

Some have postulated that a lot of the "set in stone" measurements such as bar width and crank length have little scientifically-valid basis, and given some of the other atrocities the cycling industry has bestowed upon its patrons in the past it wouldn't surprise me if these figures were essentially just pulled out of their arses :rolleyes:

This position might be further supported by the relationship between crank length and rider height as specced by manufacturers. For example according to Boardman's specs for their latest SLR 8.9, male riders of height 170-179cm (mean 174.5cm) get a 170mm crank, while at the other end riders of 187-195cm (mean 191cm) get a 175mm crank. That's an increase in crank length of 2.9% to suit an increase in rider height of around 9.5%. Perhaps I'm over-simplying things, but surely you'd expect the ideal crank length to scale linearly with the rider size..?

Both my newer (2017, 2020), "medium" bikes have 172.5mm cranks and 420mm bars, yet ironically amid this "new" train of thought about crank length and bar width, my 33yr old Raleigh town hack has 165mm cranks and 380mm bars :whistle:

Interestingly it seems that these trends are being noted, with the new Boardman stuff running slightly shorter cranks and narrower bars on their 2021 range.

So, what do we reckon about these changes; legit scientifically-led progress or just another aribtrary turn of the wheel to incentivise spending more on "better" gear?

More specifically, do people see merit in shorter cranks and narrower bars? I can appreciate the argument for both, however the bikes I have that differ in these ways are so different in others that I can't really make valid comparisons; irritating as that is. That said while having a short reach I should benefit from narrower bars, I certainly don't get on the Raleigh and feel it instantly fits me better than say my Boardman with its 40mm wider bars.

The Genesis does feel long, but then it has a lot of reach both on the bars and brake hoods and while I spend most of the time on the outside of the tops / a good bit back from the hoods, the extra reach comes in handy when chasing aero gains and they feel right when climbing out of the saddle..

Ultimately feck knows, but I'd be interested to hear your thoughts :smile:
 

Sharky

Guru
Location
Kent
I went over to shorter cranks a few years ago. As you say, it opens up the hip angle and the higher cadence puts 'zip' into your riding. A feeling I used to get when I was younger.
 

MichaelW2

Veteran
The scaling of crank length to height, or more specifically leg length, or even more specifically, femur length, is OK for medium people who can pick short, standard or long cranks however they prefer.
Tall riders are always riding short cranks, and even worse short riders are always on long cranks. Only TA make a reasonable range of crank lengths and they are such a boutique brand.
 

Sharky

Guru
Location
Kent
There are others. You can get Sinz expert cranks in a very wide range of crank lengths. They are square taper, but very good.

I have 145mm on my TT bike and 150mm on my other three!
 

si_c

Veteran
Location
Wirral
I watched that video the other day and I had a few takeaways from it but I'm not sure what I could do about it. I'm a little over 6'5" in height so I struggle with saddle height on pretty much all the frames I've ridden, it tends to be a case of needing to have it fully extended.

My last frame was a 61cm frame with a 400mm seatpost pretty much all the way extended out. I'm currently riding a 63cm Kinesis Racelight with a 440mm (c-c) bars and a 120mm stem, 175mm cranks. I don't have the stem slammed as it has 2cm of spacers underneath, but that results in a 5.5" (14cm) saddle to bar drop, so it's long and low already. My Trek Domane has a different position - it's a bit more upright, but it's still a 62cm frame and has a 4" saddle to bar drop, same bar width and crank length although the stem is 110mm so a tiny bit shorter, but the seatpost angle is slacker so the saddle is a bit further back. Saddle height on both is the same within a couple of mm.

These positions are derived from setting the bike in it's most upright position and then tweaking the position over time, raising the saddle a couple of mm or changing the stem out for longer if needed. One thing I've never changed is the 175mm crank length - I'm not sure that going to 170 would give me any benefit - I'd have to raise the saddle height even further than it already is and that would mean raising the stem as well as I don't want yet more drop.

I'm quite tempted with the idea of having a proper bike fit as I'd like to know what size frame I should be riding as well as what is a good endurance riding position for me. Maybe once we're done with COVID I can persuade Mrs C that it's a good idea:crazy:.
 

FrankCrank

Professional layabout
For cranks, I use 140mm on both my 'bents, and regular 170mm on DF bikes - works for me. My preference for handlebars is an upright position, north rounders seem to hit the sweet spot. Frame size, at 5'7", a small or medium will work, enough room for adjustments to get either to fit OK. Have never seen the point of all this 'frame fit' malarky, where you get measured to the nearest mm and then get a frame made that's an exact match. Would have thought off-the-peg stuff had enough wriggle room, but then again I'm not doing the TDF :laugh:
 

Twilkes

Veteran
I watched that video the other day and I had a few takeaways from it but I'm not sure what I could do about it. I'm a little over 6'5" in height so I struggle with saddle height on pretty much all the frames I've ridden, it tends to be a case of needing to have it fully extended.

My last frame was a 61cm frame with a 400mm seatpost pretty much all the way extended out. I'm currently riding a 63cm Kinesis Racelight with a 440mm (c-c) bars and a 120mm stem, 175mm cranks. I don't have the stem slammed as it has 2cm of spacers underneath, but that results in a 5.5" (14cm) saddle to bar drop, so it's long and low already. My Trek Domane has a different position - it's a bit more upright, but it's still a 62cm frame and has a 4" saddle to bar drop, same bar width and crank length although the stem is 110mm so a tiny bit shorter, but the seatpost angle is slacker so the saddle is a bit further back. Saddle height on both is the same within a couple of mm.

These positions are derived from setting the bike in it's most upright position and then tweaking the position over time, raising the saddle a couple of mm or changing the stem out for longer if needed. One thing I've never changed is the 175mm crank length - I'm not sure that going to 170 would give me any benefit - I'd have to raise the saddle height even further than it already is and that would mean raising the stem as well as I don't want yet more drop.

I'm quite tempted with the idea of having a proper bike fit as I'd like to know what size frame I should be riding as well as what is a good endurance riding position for me. Maybe once we're done with COVID I can persuade Mrs C that it's a good idea:crazy:.
What's your inside leg, out of interest? I'm 6ft5 but have a pretty standard 34" inseam.
 

Twilkes

Veteran
I have 175mm cranks on one bike and 170mm on another and don't really notice the difference - perhaps only when riding out of the saddle up a steep hill where it maybe feels like I could do with some more travel on the 170s. I think there's a wide range of crank length where the difference to the rider is fairly negligible, unlike saddle height where +/- 5% would make a noticeable difference.
 
Very opinionated chappie isn't he? He doesn't seem to take into account the usage of different bikes and just goes for a generic this is how it should be approach.

Gravel bikes like my Kona are very much influenced by Mountain Bikes in it's approach to sizing, so 460mm wide bars (Centre to Centre), 70mm stem and 170mm cranks. Now off-road the influence those wide bars and short stem can really be felt, the bike can handle some really impressively rough trails. The other benefit on road is the comfort this affords, I have never ridden a more comfy bike and in the summer I rode 440 km across Slovenia loaded up and didn't suffer a single bit of bike fit related discomfort.

So forgive me if I take some of his protestations about bar width with a pinch of salt, it really is up to the individual rider and the usage to which the bike will be put. Narrow bars will suit some riders and their intended use, but equally, wide bars have their place to and can contribute to an impressively comfy all day touring bike.
 

Venod

Eh up
Location
Yorkshire
The bar width conundrum is a topic I struggle with, I am 5' 10" of normal build but prefer 44cm drop bars, the latest bike has 42cm, I have not changed them yet but considering some carbon in 44cm, the aero argument is not a concern, anything narrower just feels uncomfortable, on my MTB they are wide but not as excessive as some, I have considered cutting them down, I rode 170mm cranks for years, they are my preffered length, but the three bikes I have now have 170, (CX) 172,5 (Road) and 175 (MTB) I don't notice the difference. The road and MTB came with that length, I built the CX so chose 170, if I had built the other two I would have chose 170.
 

YukonBoy

The Monch
Location
Inside my skull
Crank length will not scale with height. Even people of the same height can have very different leg dimensions. Even with same leg dimensions riders will have different preferences or indeed not really care whether it’s 170mm or 175mm.
 

MichaelW2

Veteran
I have 175mm cranks on one bike and 170mm on another and don't really notice the difference - perhaps only when riding out of the saddle up a steep hill where it maybe feels like I could do with some more travel on the 170s. I think there's a wide range of crank length where the difference to the rider is fairly negligible, unlike saddle height where +/- 5% would make a noticeable difference.
Both of those are small cranks with minor differences for a rider of your size. Zinn would probably fit you with 200mm cranks on his xxxl bikes with higher than normal BB height for cornering clearance.

https://zinncycles.com/product/khs-flite-747/
 

si_c

Veteran
Location
Wirral
Both of those are small cranks with minor differences for a rider of your size. Zinn would probably fit you with 200mm cranks on his xxxl bikes with higher than normal BB height for cornering clearance.

https://zinncycles.com/product/khs-flite-747/
I'd argue that that bike is for people significantly taller than me. Aside from the fact it's hideous, it's geometry is very very tall and very upright, it's probably a comfortable position to ride from but it's not going to be particularly quick. I'm curious about how it handles as well - it's definitely going to have a very high centre of gravity.
 
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