sean.hwy

A lot of bike brands as for height and inseam when sizing a bike.

Some sites say from from crotch to floor. While others say to your ankle. That's going to give two very different answers.

mstateglfr 

I have never heard the ankle one.
Odd.

Maelochs

https://www.competitivecyclist.com/S...ulatorBike.jsp

Sy Reene

Interesting though. "Just be sure not to use the inseam measurement from your jeans as pants inseams are at least 2" shorter than your actual inseam."

Am I alone? My jeans are typically always 1" longer nominally than my actual

Maelochs

Ummmm .... well. "Actual" inseam is from crotch to floor. "Clothing" inseam is usually shorter as pants are supposed to "break" on the top of the foot and come down to about an inch above the floor in the back, so as not to drag on the ground. if your jeans are an inch longer than your actual inseam you are rolling your cuffs or walking on them.

Of course, nowadays some guys wear their pants below their buttocks. I have no idea how to measure "clothing" inseam in those cases. Happily, I only need my actual inseam to ride a bike.

Inusuit

Seems an inefficient way to size a bike.

Maelochs

Yeah ... . try as I might I cannot get an accurate measurement of my bike's inseam.

urbanknight

Inseam alone is not a very good way to size a bike. The fit calculator Maelochs linked to is a much better way.

tomato coupe

Not if you're an actual cowboy ...

KerryIrons

Please provide a link to the site that says to measure from your ankle. Nobody does this and in over 50 years in this racket, I've never heard of it. So a link to that reference would be interesting so we can figure out what kind of nonsense they are spouting.

sean.hwy

google "how to measure inseam"
google "how to measur inseam"

most results come back with ankle or where your pant ends.


I always thought it was crotch to floor.

ThermionicScott 

Do you see anything in that result about fitting a bike? Let's think about this a little.

genejockey 

And they should get off your lawn.

urbanknight

That's an attempt at idiot-proofing people who are trying to figure out what size pants to buy.

sean.hwy

I guess I have not bought pants in a long time. The inseam number that I have always used was from the floor.

urbanknight

Eh, maybe the brands you were already take that into account? Makes me want to go measure the actual inseam of my pants. I do tend to wear 30" in Levi's and Dockers, but 31" in Dickies (I measure 31" to the floor). Some people also like their pants to come to the floor or bunch up around the ankles... or they cinch the wait up high.

But if you have always measured it from the floor, what made you suddenly google it recently?

sean.hwy

I injured both of knees in motorcycle accident in 2016. 2017 had surgery on both knees. I can hike ok, I still can't run. If I putz around on bike at 100 watts on flat ground I can ride all day. Of course bike rides are not putzing around in zone 1 all day. I have been reading & watching lot of stuff on knee pain while biking. Some stuff comes back as q-factor but I can't find anything on how to measure what yours should be. I see lot of stuff on bike fit, what size bike you should ride and shorter cranks.

https://www.applemanbicycles.com/res...-crank-length/

If I was to believe this ^^^^^ I should be riding on 155mm cranksets. I have been thinking of getting a bike fit, and shorter cranks to see if that helps.

urbanknight

I'm always suspicious of "articles" that are published by the company making the specialized product they are saying is needed. They may believe it themselves (which might be why they are offering the product) and they may even be right, but it's biased no matter how you look at it. For that reason, I tend to look for independent articles that support the findings. There is credibility to going with shorter cranks, and you might benefit from it more than others due to your medical history, but this company's products just might be a solution to a problem you don't actually have. Get the bike that fits you and see if you have any problems (pain or discomfort) with the size of its parts (stem, handlebar, seat setback, cranks).

Sy Reene

I can't explain it, it's just my experience. I've worn 34" length levis for many years. My cycling inseam is 33". Supposedly I should buy Levi's with a 31" inseam. I'm 6'2" and I don't roll up the cuffs on my jeans. ymmv

rc5781

Assuming you have the correct size frame for you (I'm 5'11 and have a 17 inch mountain bike frame), adjust your seat height so that you hyperextend when pedaling. Then bring down your seat height until you're just short of hyperextending.

[Oh, wait...sounds like you're trying to size your frame, my bad...]

Maelochs

As I understand it, with shorter cranks the rider spins faster against marginally less leverage and with marginally less force (since the force is spread over more repetitions) so hsorter cranks are good for people who have tender knees.

"Q" factor is .... well, if you are running a triple crank or something, or riding a fat bike, it might be an issue. Basically you don't want the pedals to be wider than your hips? Most bikes are pretty similar .... two chain rings or even three, most are not that wide. Unless you have some specialty bike, I wouldn't even worry about it.

The most important consideration, IMO, is bike fit---and this means fitting the bike's contact points, which determine your riding position, to your body and riding style.

Obviously there can only be rules of thumb, because each of us has a specific body. if I had bad knees I would probably be most interested in not hyper-extending---which is also my main consideration with my not too bad knees. Hyperextension Hurts and causes lasting damage. But you also have to look at where your feet hit the pedals (most people suggest the ball of the foot or a little back, I think) and how far your feet are ahead of seat ....

if your legs don't extend enough, it pus more strain on your knees .... or more accurately (and in terms of physics or physiognomy, none of this is really accurate anyway) you won't be using your legs as efficiently if you don't extend them the proper amount ... More power than the motion can transmit, which means more strain on the knees. But, given that you might be riding with less than maximum power to spare your knees, a little shorter might be better. You can and will almost certainly have to adjust your position many, many times to dial it in.

Also ... putzing around in Zone 1 Is cycling. Maybe not what you want, but if you enjoy it, you do.

Calsun

It is a ballpark measure to get you within a couple of sizes for a start. Ultimately it depends on how you feel on the bike in a normal riding position and posture. It is also going to be different for a mountain bike as compared to a road bike or a touring bicycle. Most bikes now come in half as many sizes than was the case with centimeter frame sizing in the past. It has become a XS, S, M, L, or XL size frame.

For men it is more important to be able to stand over the top tube with feet on the ground to protect vulnerable parts of the body. There is a tendency for men to get the smallest frame that will "fit" as a result, even if that requires very long seat tubes and stems.

tomato coupe

I think you can get within a couple of sizes just by guessing.