Sizing - hypothetically?

larkim · January 2019

If in a hypothetical world you only had the choice between two frame sizes of one bike, and you were objectively half-way between being perfectly sized on either, should you choose the bigger or smaller of the two sizes when thinking about trail performance?

I know the ideal is that that bike should fit correctly, but in broad terms is it better to err on one side than the other? A bigger framed bike can be made to feel smaller by seat and stem adjustments, but then so can a smaller framed bike be adjusted in the opposite way. But broadly if you make the bigger bike smaller you'll bring the weight forward and make the steering faster / twitchier, and vice versa you take the weight back (seated) and make it slower. What would be the broad guidance in terms of what is prefereable, noting that this is a MTB website not a leisure riding website!

slc123 · January 2019

I don't think anyone will give you definitive advice and there isn't really a right or wrong answer as everyone has their preference of riding style and what they feel comfortable with. I am between 6'1 and 6'2 and consider my arms and legs relatively well proportioned... I have been riding a Large HT that with a decent travel fork felt roomy enough perhaps a little cramped. I scaled the fork back to less travel and I've since felt really cramped up and a little to over the bars. I should have probably gone for an XL in that frame. I'm just building a new FS bike and that's going to be XL, it looks pretty big long compared to the HT, but I won't know until I sit on it. Based on this I would say I am in the go bigger camp.

A guy I ride with is pretty similar height to me and proportions but prefers a smaller bike. I personally think he looks cramped and probably compromises pedalling efficiency, but he doesn't seem to mind!

I think ultimately it's pretty academic as it's about your proportions and how you like the bike to ride/feel and what type of riding you are doing.

larkim · January 2019

Fair enough answer. The only reason I ask is that plenty of us don't have the luxury of trying out different sized bikes for long enough to get a proper feel for it (and might be so in-expert that what we feel isn't really relevant!), so faced with a dilemma of a bike which on paper might be smidge too big or a smidge too small I wondered if there was a default position.

Sort of like with trousers - too small, and you can't do much about it, too big and at least you have the options of re-sizing ;-)

slc123 · January 2019

It is a tricky one and I am in a similar position. I don't think by sitting on a bike in a shop you'll really ever know. It might feel OK but until you've climbed on it or descended you can't tell if it suits or not. I've just learn't from mistakes and just ended up changing things about until I get it where I want it to be. Like I said the HT feels a little bit small but I've adjusted as much as I can in terms of wider bars, spacers etc. It was a much better size when I had longer travel 160mm forks on it, but it didn't suit the riding, so I made the trade off to 130mm forks and now it climbs better but feels a little cramped and I feel less confident as I'm pitched a bit further forward but hey the riding I do mostly isn't hugely technical so it's fine. The new build I want to get right in terms of sizing as that's the one that goes to the bike parks and further a field to be pointed downhill. I would always prefer the bike to be slightly bigger for that as it just gives me more confidence.

Sizing - hypothetically?

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