are we riding bikes which are too small?

....A while back I read an interesting post re downhill geometry:

https://www.mbr.co.uk/news/size-matters ... all-321374

...and so a small experiment began. Bearing in mind I have a stable of bikes running back to the 1990s, and some of those were VERY carefully put together after experience of cycling thousands of off-road miles. Typically, at 5 foot 7 I have been riding 15 inch frames - orange, bontrager. AMP, and so on. My optimum bike of years has been a 15 inch (orange called it 17) bb to tt centre C16R - huge fun, fast and reliable as the cold water tap. And then I got into DH (my son was to blame for that ... I said 'yes' to building a gravity bike for him). And so the fun began. A couple of DH rigs later, I had begun to re-think geometry. I had a 'large' Cannondale F6 frame lying around (16 inches bb to tt centre), and decided to stick 130 travel forks (Reba) on the front, and made it up. I had seriously dismissed the frame, but measured it and found that it had the same reach as my orange, but with a much higher bar height. The 130 mm forks and 40mm stem did not mess up the geometry since the F6 is actually build for this length of fork, with a good seat angle and slack head angle - although no way as slack as a Cotic or Ragley. The build went well, with Hope WTB and 11x2 XT it came out at just over 9kg. And I thought it would handle like sh+t, compared with my reference Oranges. How wrong I was. Ten minutes in fast, rooty and slippy single track showed the bike as fast, responsive, flickable, strong in climbs and quickly 'a body part' rather than something being sat on.

I got back on the Orange and it just felt short and small. The standover height was right, the Orange catalogue of the time said the size was right. Yet with the 130 stem out front and the tt at 56 cms it now feels WAY too small. And slightly scary going downhill. The Amp (a medium) was just as bad. Yet the AMP had felt big when I first got it, way back in the last century.

Next to the Cannondale the Orange looks tiny and the AMP looks like a much smaller brother.

I am building a Cotic SOUL and Ragley Marley for the retroGrom...much longer cockpits and very slack head angles.

I think we might be riding things out there on the trails and climbs which are too small.....

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You've gone from one extreme to the other there!
The difference between the 13cm stem on the C16 to the 4cm you've got on the Cannondale is absolutely massive, and must cause a huge change in the steering?
9cm must surely be greater than the difference in the respective top tube lengths, meaning the C16 is actually longer? But the size 17 C16 has a tiny head tube, so with a shorter fork it must also be massively lower at the front - do you think it's that which makes it feel smaller?
I certainly agree with you that lots of riders fit a shorter stem to improve the handling, without thinking through that maybe they really need a new, and longer, frame to compensate.
Personally though, I like a small frame as it promotes a more upright posture - and I think that suits longer forks. But I feel sure I'm in a minority on that.

Different bikes handle differently is the take away lesson from this as far as i can see.

And 13 cm stems on tiny bikes is a bad idea and says you've probably set it up badly, or bought a bike that's too small.

It’s all about effective lengths from your privates to the contact points......and how long your toes are

Aerodynamics etc need taking into account as well, them woods get awfully fast in the retro tuck position until you find a 4 foot drop.

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...just to be clear, orange C16R 15 inch (17 orange catalogue) is not tiny - at 5 foot 7 this was absolutely the recommended size for this height back in the day. This was the second size up in the range, there was a 14 inch (orange said 16). And the 19 inch does not have enough stand over - I know this since I have a couple of them in the barn. And 130 was a very standard stem length at the time, and was the length supplied on this bike. So that's my point really...what is now called 'aggressive trail geometry' really is very different from geometry of the 90's and is changing even now. The new San Quentin Marin is very interesting, with a very slack head angle (65) long travel suspension and very steep seat angle to keep the reach within bounds (75).

The best downhill rider I knew back in the early 90s - was 5 foot 7 - and rode a 21 inch Stumpjumper. It was enormous but he simply lay almost flat, dropped his ass off the back and grabbed the seat with his knees.

I have struggled with sizing a lot over the years. 18, 19, 20 inches have all felt either too small or too large depending on geometry. I've also had quite good fitting from bikes of each of those sizes. The best fit was a 19 or 20 inch Dawes Ranger - because it was long (especially with the layback saddle) which gave me the right mix of being able to ride almost anything up or downhill. I have longer femurs, longer feet and longer arms than my shade under six foot height would suggest.

I now tend to go for 20 inch retro rides (and have a 2016 20 inch charge cooker too) with various stem changes (usually higher with riser bars) and layback seat posts. The Cooker has had no changes. All told the step overs are a little higher than I would like but I can leave with them. The best tactic, however, is to regularly ride all of my steeds so they don't have a chance to feel weird.

I've yet to try a modern trail or downhill bike - but am intrigued.

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Good that you mention weird - that’s exactly my experience - ridden four retro bikes in anger for years - then built new ‘big bike’ and acclimatised - now three of the retro bikes feel so weird they feel wrong - one feels weird but rideable - and the common factor is that they were once considered ‘exact fit’ but now feel far too small...just lack of acclimatisation or have things actually seriously moved on? The latter I think ....

Not a bad read. Don't really agree with everything he's saying though.

BMX with short stems and higher bars also played a role in MTB development for sharper handling at low speeds.

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Shouldn't the question be "are we riding bikes " as apart from MM the ride and most area group sections on this site are as active as a dinosaur !

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I have mentioned it before but back in the mid 2000’s I could happily switch between modern and retro. Since then and especially in the last few years geometry has changed so much it makes retro feel very odd to me. Saying that, it also made my 2007 Clockwork feel strange so it’s not just a retro issue.

Fine if you don’t ride modern but for me my current bikes make retro riding pretty redundant. Too small, too twitchy, wheels too small and not stable enough. Still lovely to look at though.