“I can’t believe I’m a size XS” – about mountain bike sizing
Here’s the sort of question I get all the time in the Lee Likes Bikes MTB School. This member site has tons of info about bike fit, riding skills, mental skills and physical training. Members get to interact with me 1:1. Here’s today’s question:
Hi,
I am slightly confused. I am 5? 7.5? and my RAD is 766mm. I have a 2019 Cube Stereo 150 in small. Cube states that I should be well within riding a medium size, however even on a small with a low and short stem the a RAD of 805mm which is RAD ++. I am not to unusual in shape or size, the bike doesn’t have progressive geometry and isn’t particularly long, so why should this be so far out? I would hate to think if I bought a new bike with progressive geometry – I would be on an XXS!
Steve H.
Hi Steve,
From here it’s all math. If you want to ride with dynamic integration with your bike, you need the bike to be RAD neutral or slightly RAD minus compared with your body. This gives you access to your peak power and full range of motion to control your bike, plus it prevents chronic injuries (worn out shoulders) and acute injuries (being launched over your bars onto your face). Riding is just more joyful.
We can run numbers that tell us what frame reach you need. From there we choose the frame size, then we model the details using the RideLogic bike calculator in the member site.
The bike industry sizing is way out of whack these days. This is because they are all chasing this “longer is better” trend. It’s a trend, and every company who wants to sell bikes has to follow it. A classic example is Chris Cocalis, founder of Pivot. He’s a smart engineer who fought the trend, but the man has to pay his staff and feed his family, so he made his bikes longer. But get this: I heard him say he, his racers, his staff and the people they fit at demos have all gone down a size. Yeah.
Here’s a great example: The reach on a small 2023 Santa Cruz Nomad is LONGER than the reach on a 2013 XL Santa Crux Nomad. That means if the 2013 XL felt good to you, you need a size S in the 2023 model. I made an infographic! Check it out. Consider that people have not changed size, and the Santa Cruz size charts have not been updated to reflect these changes. In 2023 they tell a 5’1″ rider to ride the same size they told a 6’2″ rider to ride in 2013. These are numbers plain and simple.
This requires people, especially men, to get over that size letter. An S doesn’t make you less of a man than an M. Hopefully you’re not stuck in that trap, but many men are — which is why I’m talking about it here.
I am exactly 5’8.5? tall per my doctor (although I project 6’0″ :). I’ve ridden medium sized mountain bikes for 35 years. My most recent bike, an Ibis Exie, is a size small (and I still feel like a man). Many modern bike are too long for me in every size. I’m fortunate to be offered bikes from various companies. I look at the geo charts. If the reach on the smallest size is too long for me, which happens most of the time, I say thank you but no. It’s a total waste of time to ride a bike that doesn’t allow me to ride my best.
Based on the numbers you gave me, the MAXIMUM viable frame reach for you is about 420 mm. It’s best to err shorter, especially if you want to ride technical trails well. Your small with a reach of 420 is a hair long but workable (use the calculator in the member site to model a 30mm stem and an SQlab 30X 16-degree 15mm rise bar upside down with a rise of -15mm).
If you hire me to do a 1:1 fit for you, I’ll push you to the XS with a reach of 405mm. That bike will shred so hard! The medium with a reach of 440 is way too long to be ridden well — unless you just want to cruise around mellow trails or on technical tails be a hunk of meat hurtling to an uncertain fate.
I’d love to say trust the geo charts and the local bike shop bros who ignorantly refer to them, but that just won’t give you a great-fitting bike. My biggest advice for all men is to get over yourself when it comes to your height and bike size, run the numbers, make an informed buying decision, focus on your abilities then spread joy everywhere you ride.
Does this help?
Lee