bikeamateur70

You have an online bike fit calculator to recommend? I am going to buy a gravel bike, but need some data if I gonna find a rekaxed and good frame for a rather stiff 51 years old (181 cm tall). Sickbicker recimmends the one from competetivecyclist, but the page isnt operating.

veganbikes

I would play Rock Paper Scissors or roll some dice if I am doing the online thing. I would visit with an actual fitter and get a proper fit if I really wanted to not go by chance.

wolfchild

I did all my bike fitting at home by myself without any complex mathematical calculations. Sure it took a bit of tinkering and experimenting but after a couple of rides everything is perfect.

Brofessor

Not sure what you mean by a "fit calculator", but if you are looking for something to compare the fit of a new frame to an existing one that fits you well, you can use this one: https://www.velogicfit.com/frame-comparison A lot of "fit calculators" make a lot of assumptions on what you will be comfortable with (ball of feet on paddle axle is one of them, which might not be ideal for some people actually).

AlgarveCycling

Nothing beats a proper bike fit. While it isn't hard for a casual cyclist to get in the ballpark for less intensive, shorter rides, if you intend to do a lot of riding and especially if already prone to physical issues, best get it done professionally.

For years I did it myself. When I finally went and got it done professionally - bike on a stand, laser measurements, specific bike geometry accounted for, personal measurements etc - there were small changes here and there, including my shoe cleats and the difference was immense on me physically for longer distances, harder riding. When I added another bike, I set it up exactly the same myself at first. Went to the pro bike fit folk, they found some more adjustments! Different bikes, different angles, differences hard to measure properly.

bikeamateur70

I am looking for a good way to find which frame size I should go for when purchasing new bikes. I will probably buy second hand, so its good for me to be able to figure out if the frame will be my size before I make trips to check out various bikes. When I have a reliable ways to measure my various body parts I imagine its easier to check the geometry of the frame from the bike manufacturers.

When I have purchased a new bike I will definately consider going to professional bike fitter. Been doing rather long rides on a hybrid bike with a frame too large, its causing neck pain. Hope to be better suited before a buying my next bike

ofajen

A key measurement is your pubic bone height (PBH). Just stand barefoot facing a wall or door and pull a measuring bar or even a book up between your legs until you contact the bone and can’t go higher, making sure you measure on the level. Then mark and measure that height down to the floor. Having a second person to help make sure it’s level and record the height is handy.

You can get a very good guess at proper seat height from PBH * 0.883. Seat height is the distance along the seat tube from the center of the bottom bracket axle to the top of the saddle.

With older frames, you could expect a reasonable fit by subtracting 15cm or maybe 16 cm from your seat height.

Many modern frames have sizes like T-shirts and the frame geometry is different so there is no longer a true seat tube length to measure, it’s more of an “effective” seat tube.

Still, knowing your PBH and seat height can quickly help you get an idea of what would work. Some manufacturers have guidance showing how their sizes match up.

Now are you hard or easy to fit? Longer arms and torso usually make it easier, shorter ones make it harder. One clue is the fraction of PBH to total height. Should be in the vicinity of 50%, and smaller values mean easier to fit.

Another is the difference of your wingspan (fingertip to fingertip with arms spread wide) minus total height. Positive values mean easier to fit, negative values mean harder.

That should get you started.

Otto

philbob57

I think that would result in a frame that's too big. BITD, with steel diamond frames, the reco was to buy a frame that was 9"-10" smaller than your PBH. A person can probably ride a bike that's 15 CM shorter than PBH, but stopping it could be painful.

kingston 

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

ofajen

Sorry, you missed a step there. The frame size would be 15-16 cm less than seat height, which will be roughly .883 times PBH. Probably pretty similar result for most.

Otto

philbob57

I apologize for misreading your words, Otto.

ofajen

No worries. Truth is, my PBH is 36.5” and I ride 25” or 63 cm frames, which are arguably a little small for me. Seat height is 82 cm or 32 1/4”. So I’m at about 19 cm less than seat height. Oops! 😐

Otto

genejockey 

Something's not quite right, still. My inseam is 88cm, which indicates a saddle height of 77.4 (my saddles are actually at 78.1, but what's 7mm among friends?) Take away 16 cm from that, and it would have me on a 63 cm frame. I ride 58s with 110-120 mm stems.

ofajen

I think that would be 61 to 62 cm. Still as I said, this was an older guideline. Current practice is different and that 3-4 cm difference is common.

On modern bikes, people tend to ride smaller frames with lower bar height, bend their elbows less and ride the hoods more because they are already pretty low.

OP describes himself as a “rather stiff” 51 years old, so I’m thinking the older rule would give more room for higher handlebars that might fit better.

Edit: I forgot to add, another relevant feature of newer bikes is that bottom brackets tend to be several centimeters higher than they used to be. This will raise the seat higher for a given rider and may or may not be compensated for in head tube to raise bar height. The sloping top tube of modern compact geometry should compensate and allow a rider to keep a similar frame size.

Otto

Wilbur76

Somewhat unrelated but a good bike geometry comparison site I use is https://bikeinsights.com

Helped me to compare between brands, models and sizes.