69chevy

Use Bike Fit Calculator | Find Your Bike Size | Competitive Cyclist to determine the optimum sized bike for a person your size. Take accurate body measurements! Don’t skimp here.

Once a bike is decided, or if you already have a bike, it’s time to adjust the bike to meet the three critical measurements (recommended by the calculator) listed below, and illustrated on attached picture.

If you can get these three measurements in the proper range, bike size doesn’t necessarily have to match the recommended bicycle sizes given by the calculator. Notes at bottom explain.

BB Saddle Position (orange on drawing, called bottom bracket to saddle) is the first thing to adjust. This height is very important for comfort, power production and knee protection. Once this height is set within the recommended range, set the Saddle Setback.

Saddle Setback (blue on picture) can be measured several ways. Saddle setback is important to power production and protecting the calf/hamstring at the back of the knee. The easiest way to get this measurement in my opinion is to back the tire of the bike against a wall and stand it upright, perpendicular to the wall the tire is against. Take the measurement from the bottom bracket to the wall (keep measuring device level). Write this measurement down. Now take the measurement from the back of the saddle to the wall (keep measuring device level). Write this measurement down. The difference in the two numbers is your saddle setback.
Once these positions are locked in, there is only one other measurement that is left.

Saddle-Handlebar (red on picture, called saddle to bar). Measure from the tip of your saddle to the back edge of your handlebar. If it falls within the recommended range and is at the height you are comfortable riding, you are ready to go.

If it is outside of the range, you will need to change stems to compensate. To do this, you must figure out how long your current stem is. If your bars are too close, you will need a stem that is longer by the amount you need. Most stems are sold in 10mm variations.

If your recommended range is 58.3 to 58.8 and you are currently at 57.5 for example, you will need to add 10mm to the length of your stem. If you have a 110mm, you will need a 120mm.

The recommended stem length is included in the calculation and should be very close to what you actually need.
These three measurements will put you very close to a comfortable, powerful and efficient position.

NOTES:

Saddle-Handlebar measurement has the most leeway when it comes to a comfortable fit. If you are comfortable with it shorter or longer than recommended, set it where you like it. Longer means more aero position (taxes shoulders and neck), shorter means more upright (more wind resistance). If you set it to the recommended range, bending your elbows to make adjustments to your position is the norm, but requires your arms to be fit enough to support the extra weight.

Another measurement that needs to be considered is your bar height. The last three measurements shouldn’t change, regardless of flexibility. Bar height is based on user comfort and should be adjusted to taste. Remember though, raising/lowering your stem affects saddle-handlebar distance, and should be considered.

It is possible to compensate short seat tubes with longer seat posts as long as they can be inserted to the safe minimum amount usually shown by a line on the seatpost.

Top tube length can be compensated by stem length, but 90-120 are the most common sizes. Any size outside this range will likely make a noticeable change in the feel of your steering response.

If you cannot get these adjustments close to the recommended range (with longer seatposts, longer stems, seatposts with setback, etc...) and cannot ride your current bike comfortably, a new frame size may be the only option. I recommend a size that falls within the ranges provided by the calculator.




EDIT:

The numbers the site gives you will look like this....

The "Seat tube range CT" is the number most companys call the bike "size", but it can differ based on the slope of the top tube.

Check the geometry chart for the bike you are considering.

The measurements given by the calculator can be compared to the geometry provided by the bike company to determine the best size for you.

If you struggle to figure out the right size, post your recommended measurements on here and the bike you want, and I'll show how to pick the size to suit you based on the data from the calculator.

pakk

I've done this twice and it seems pretty accurate except for my saddle to BB. It positions it way too high.

Clipped_in

Sticky that OP!

69chevy

I will say that it positions you properly in relation to your bottom bracket.

Your crank arm length (bike manufacturers usually size based on average riders) and shoe size (foot length) could mean that you still have the issue of needing to to pedal "toes down".

If you have to lower your saddle outside the measurements suggested by this calculator (based on body geometry), you may want to consider a shorter crank arm or taking your measurements again.

But... if you are comfortable being lower, still have a smooth pedal stroke and don't feel that your quads (or knees) are being overly taxed, riding lower than recommended isn't uncommon.

Comfort always trumps these numbers, but these numbers will get most riders very close to comfort.

69chevy

Not sure how to "sticky" it.

I wanted to write it so I can link to it when these questions come up, but if it gets "stickied", that would make it easier...

Sojodave

I'm 6'4" with a 34" inseam. It recommends a 63 cm bike. I currently ride a 61 cm and a 63 seemed huge when I test rode it. It sucks being tall because you can't test ride bikes before you buy them. They never have any my size and if I got serious about a bike, I would have to order it and hope for the best.

69chevy

That doesn't sound right. (I say this because I'm 6'3" with a 36" inseam and it recommends a 60cm.)

I also have a long torso and "short" legs for my height. 34" long pants drag the ground on me.

Did you input your inseam measurement exactly like instructed?

EDIT: I put in my numbers but changed my inseam to 34" to match what you said, and it tells me a 60cm is my size. What number did you see that made you think 63cm was your size?

pakk

I'm pretty comfortable in my current fit. Also not feeling significant soreness. I have been considering a shorter crank. I'm currently using a 170. How much will a 167.5 affect my saddle height?

69chevy

It will allow you to move your saddle up 2.5 mm in the seat tube, which isn't much.

If you are comfortable where you are, there's no real reason to change.

If you had a 175mm crank, I'd say it would be worth considering.

When you are on the saddle, can you reach your pedal with your heel?

Sojodave

Here is what I got from my fit on the Bike Fit Calculator

69chevy

That puts you on a 60cm frame, which should be close to perfect.

Most bike companies size frames based on seat tube not top tube.

I would check your inseam measurement though, it may be skewing the fit.

The measurement should be up to your crotch with your crotch putting normal pressure on a tube. If the inseam is wrong, it will throw the reach off since the computer will think you have a very long torso.

Sojodave

I really wish I could fit a 58 cm bike. They are easier to find, easier to sell, and I could actually test drive them before I bought them. I wonder if I'm close enough to ride comfortably on a 58 cm?

69chevy

I'd advise against it. You would either have to ride it very upright, or use a very long stem on it.

dr_lha

There are serious issues with this calculator. It works for many, but for me and others with long torsos and relatively short legs it gives ridiculous answers for bike fit. I'm 6'2'' and have a 34'' inseam, and it recommends me a bike with a 76cm top tube length!

Rather than just complain here, I'll recommend a different bike fit calculator, that for me produced results that much more closely match what I know fits me:

Pedal Force super-light carbon bicycle

69chevy

Thanks for the extra link. I have used the one I linked to for 10-11 people now and haven't seen any strange numbers.

Did you measure exactly as it suggests?

dr_lha

Yes. I've also entered the exact same numbers into other calculators (including the one I linked to) and got results that made sense. I'm not the only person on bikeforums who has reported this issue, but as usual the awesome search features (and Google) don't allow me to find others with issues.

69chevy

Maybe I should edit the OP and add both calculators. I honestly thought the one I posted was solid since it has been so consistant for me.

The reason I asked about your inseam is because I have a 36" cycling inseam and am 6'3". I am also have a long torso, as in I can't tuck normal shirts in and have to buy Large Tall dress shirts, or buy fitted ones.

EDIT: I just ran measurements for a 6'2" man with 34" inseam, crazy long sternal notch, crazy long arms and couldn't get it over 68cm.

dr_lha

Can you post the measurements that you put in to get that, I'd like to compare to mine. Maybe I'm getting one number wrong?

69chevy

I didn't save the numbers, but here are measurements that are the min/max it would allow me to put in for someone with a 34" inseam.

With these proportions, he would be severly deformed, have an 8" tall head, Kevin Durant arms, and his thigh+lower leg wouldn't equal a 34" inseam.

dr_lha

OK, here's mine. Tell me how I'm deformed.

69chevy

You aren't deformed, your measurements are wrong.

Thigh

Sit on a stool again making sure your back is straight and your pelvis is hard against the wall. Make sure your femur is parallel to the ground and your tibia is perpendicular to the ground. Place the level across the front of both of your kneecaps, then measure from the inside face of the straight edge to the wall. Take this measurement from both legs, then take the average.

This should be close to 24". Not 14.5


Sternal Notch

Stand up against the wall. Set your feet approximately 8" apart. Find the sternal notch in your neck - it's the bony "V" immediately beneath your Adam's apple. Measure the distance from the apex of the notch to the floor.

Your measurements mean that it is 12" from the top of your head to this spot. I would guess this is 1-1.5" shorter than it should be.

dr_lha

By jove, I think you might have it there. Clearly I must have mistyped that one in. Changing it to 24 makes everything look much better. Thanks!

PS I take back my previous comments I guess.

dr_lha

Orr... I basically have no neck. I just confirmed this measurement is correct!

69chevy

Haha, no prob.

It's not how I would guess to measure a thigh either.

If you get the right number, it will give you a better setback number as well.

69chevy

Or... I have a tall head.