How to Measure Mountain Bike Size Simply Do It

How to Measure Mountain Bike Size Simply Do It

We’re going to be talking about how to measure a modern mountain bike size. Here we have discussed details of how you can measure.

Frame Measurement

So, we need a little bit of a history lesson and mountain biking. Didn’t really evolve till the late seventies, early eighties and we borrowed everything from the clunkers, from the beach cruisers, from the road bikes, we had rigid forks and we had to set seat post Heights. So, it made sense to borrow our sizing from road bikes as well.

So rode bikes were measured in centimeters for the length of the seat tube. So, if this were a road bike and we were using road bikes, standard sizing.

We would measure this here as a 43.5-centimeter bike. I like that because they use the same sizing for all bikes.

I may start to diverge from the road bikes. We got quick-release levers on our seat post, so we could easily make seat post adjustments and lower seats all the way for downhill or technical writing.

We started getting better stand over height. We started getting suspension forks. At that time, we started sizing people differently.

From the seat tube, it was essentially adjusting the reach measurement let’s fast forward to today. We now have dropper posts on almost all bikes.

There is if you want to learn more about how to measure a bike frame quickly then you can follow the link.

I’m a big proponent of dropper posts. We now have really wide hands. We have hardtails with up to 170 millimeters of travel. That makes a huge difference on how a bike rides and it’s completely different.

So nowadays what’s even more important than seated position is you’re standing reach position. So a lot of people think reaches when you’re seated, it does not reach is when you’re into attack position off the seat like this.

If you had to dismount, you could stand on something even on uneven ground. That wasn’t the perfect way to measure back then, but it was still more effective than just going off the seat to the pipe.

Saddle Measurement

Depending on if you’re old school over the back like this or new school over the front, like this, you’re going to want a different reach number.

Now don’t size all my bikes the same. If I’m a bike, packing, and spending a lot of days in the saddle, I’m going to pick a smaller size with a shorter reach.

On a Trek stash that would put me at a large or a 19.5 as they call it on a pole, I’d be a size small. So you can’t say I write a medium giant, therefore I need a medium specialized on my next one.

It doesn’t work that way. You need to be looking at the more modern numbers and you need to understand bicycle geometry.


It’s really important to get the right size bike and some of these things take time. If you remember my modern geometry. If you learn something and you want to support this web blog, give us a thumbs up.