Modern MTB sizing

Anyone bought a MTB recently? I just got my daughter a cannondale so we could do some trails - if it ever stops raining. She's right in the middle of the range for a medium. So I bought a 2022 medium on ebay for cheap. But it's huge, like the size I'd expect to ride and I'm 6'2". It's about the same size as my motorbike. The wheelbase is huge, the reach is pretty long and it just generally seems huge to me, who's used to riding older MTBs. I just sold an XL Krampus and that was big, but not that much bigger than this medium sized one.

Is this just modern sizing? it's on 29s so that makes it look bigger as well. But my Ms had an older cannondale 29er and it was no where near as big.

I was looking for an XL epic or chisel but now I'm thinking they'd be crazy big - even though that's the size i'd need on the sizing chart. Do I just need to re-calibrate my concept of correct sizing since they raked out the forks and stretched the top tubes?

Yea, I did measure it and check it was a M on the geo chart.

Yep, modern MTBs are much longer than they used to be. The gap between my latest and last one was 20yrs and I was shocked too.
However, they are now much more capable, stable, and easier to ride than they used to be. I'm riding stuff I wouldn't have even walked down as a teenager. Suspension also works, really quite well, rather than being a bit of rubber shoved inside a noodly fork.
It might feel big and unwieldy at first, but you'll be surprised how quickly you get used to it. And if it still doesn't feel right, sizing down is an option. Quite a few pros so this for races with particularly tight stuff.

That longer reach does also mean that riding technique has changed a bit too. The old skool "get your bum back" technique will get you in loads of trouble on a modern bike. Longer wheelbase means staying in the middle of the bike and getting your chin over the stem to weight the front wheel.

Everything @TooTallTim said. And crucially: yes, these are the right sizes for your heights, especially from a brand like Cannondale that hasn't gone crazy with reach.

The wheelbase might look crazy long, but some of that length is in the slacker head angle; reaches are longer but seat tubes are also steeper, and stems are shorter. For the rider, it's both comfortable and confidence-giving. Don't forget that these frames are all also assuming a dropper post most of the time: you have a lot of ability to dynamically move your body around the cockpit as you ride more technical (down) stuff, even whilst keeping it centred.

You sound around the L-to- XL mark in a lot of brands; note that many companies (including specialized) are now moving away from t-shirt sizing and into numeric sizes (eg: S1-S6 in Specialized's case) to reflect that riders do size up/down depending on preference, and height isn't the defining factor as much these days.

bikeinsights.com will help you see how modern brands compare to one another.

My bike doesn't even come in tshirt or numeric sizes, it's measured in "long, longer, longest"

Not sure what size stem came as standard but in theory a shorter stem will handle better. Something quick and easy to swap out.

Yeah, I can relate. I recently bought a Giant XTC which is my first MTB since I was a teenager. My first thought was also 'fuck me, how big is it?' I'm a similar size to you (6'4") and immediately thought I'd made an error with sizing.

As others have said, it felt a bit unweildy at first, especially coming from a CX bike. But, after a few hundred ks it now just feels really stable. I've ridden the same trails with it that I'd usually ride on a CX bike and I'm actually quite a lot faster because less precision is required.

Thanks for that. I think the seat height on the stationary bike is also deceptive as 29s with 2.4 tires means the BB is much higher so the seat relatively needs to be higher. It all just looks massive and far from nimble but I guess if it works, it works.

I'm just over 6' 2" so maybe an XL will be fine.

Also dithering between getting a full sus or a lightweight HT. I've never had a FS and I think I just want one to try out but I'm a bit concerned the extra weight and faff will annoy me after the first couple of rides. They also seem super heavy. Do I need to re-calibrate on that too? If i can find something cheap with 100mm or rear travel I assume it'll be good for all day trail riding?

This may have saved me dental bills so thanks.

Unless you're solely doing XC racing, forget about weight. Big capable bikes just weigh more, my enduro bike is 16kg with DH tyres, coil forks and shock. Might feel heavy lifting it on the roof rack, but that weight disappears the moment you start riding.

Bouncy bikes are more fun, and more comfortable

If i can find something cheap with 100mm or rear travel I assume it'll be good for all day trail riding?

These big bikes are still fine for long days out, yes. "all day trail riding" = "trail" or possibly "downcountry" in modern terminology/marketingspeak, which usually translates to 120mm-140mm rear travel, 130mm-150mm out front. The main issue with 'cheap' will be getting something that's... basically a bit too old, ie, out-of-date geometry or out-of-date standards that you can't build upon. You can still find some great s/h deals around, though.

Dreary question: where do you ride? What do your trails look like?

Hoping to get the kids into it by doing Bedgbury etc and I try and get out to the downs but I've barely ridden the last couple of years. Just sold the Krampus as it was just too cumbersome - even if it was fun - and sold the road bike I never used, as well as the kids ones that were too small.

Got the 'dale for my older daughter now need one for myself and my youngest. Was looking at a chisel or an Epic HT (new ones are about 50% off) but now thinking maybe an epic evo (2021>) if I can get something cheap enough. Was really into the idea of a used Santa Crux Tallboy but now not so sure. Got proper optional paralysis...

Also got the small issue of rehabbing the leg I broke skiing in Feb so will be V mild trails for the foreseeable.

There was a really cheap stumpjumper evo comp alloy on Gumtree but it was an S6 size and looked like a motorbike so I passed. Looked like waaay too much bike.