Mountain bike frame size for short legs

Digger_Downsman

I'm looking to get a new mountain bike, potentially an electric one, and was looking for some advice when selecting the correct frame and wheel size.

I don't appear to have a standard body shape, being 5 ft 10 inches tall( ~180cm) and have an inside leg measurement of 31.5 inches (~80cm). I also have a positive 'ape' index, i.e. l my arm span being longer than my height.

I currently have a pretty old mountain bike( Kona Lava-dome, hardtail, circa 1992!) that has a 19inch frame and 26inch wheels. This bike is a pretty good fit leg wise, but a little short in the reach. I've never found this to be a problem though.

When I check my measurements against general guidance on the web. I'm somewhere between the top of a 'Medium' and the bottom of a 'Large' frame size( 46cm and 49cm frame).

With Haibikes models, I have also noticed that wheel size makes a difference. On 29inch wheel Bikes I'm told I'm at the lower end of a Large. But on a 27.5inch wheel bike I'm on the top end of a medium.

I'm not really too fussed if the bike has 27.5 or 29inch wheels, both are bigger than the 26inch wheels I currently ride. Also, I assume that I will get better standing clearance on a bike with smaller wheels, as it will be that bit shorter.

Would it be better to select a larger frame or smaller frame, and will wheel size make that much of a difference?

I know that the ideal approach is to get access to some bikes and to actually sit on them and ride them. But it's not always easy to do so. Stores don't always have stock in and the trend these days seems to be ordering online.

So, are there any others who may have similar experience to me, who might be able to advise?

Cheers in advance.

mully79

5ft10 is definitely a medium in my book but there can be quite big differences between some manufacturers. Bikes tend to have become longer which helps those of us who are between sizes. Some offer a ML which is a medium long frame.
I have a large trek (6ft) but my 31” legs mean I’m limited to a 125mm dropper post.
I don’t have any idea where haibike sit regards modern geometry.

reaperactual

I'm also 5'10" and between sizes. I went for a 27.5" and medium frame size. Online purchase with the choice based on comparing measurements from my previous medium frame bike.

I'm somewhere around a 30-31" inseam measurement.

Same as Mully, the stock 150mm travel dropper was the only thing that didn't fit, the rest feels fine.

I did put the saddle back a little further on the rails, probably didn't really need to, but it does go some way towards tweaking fit in either direction even if it's only a placebo effect.

Like you said ideally getting a chance to at least sit on both sizes would make the decision easier.

Digger_Downsman

Thanks for the responses.
I’m definitely thinking along the lines of a medium frame size, rather than a large, and although I like the idea of 29inch wheels, going for 27.5inch ones.
Interesting comment about putting the saddle back on the rails, as that’s exactly what I did on my old bike.
Cheers.

steve_sordy

Don't rule out a mullet bike, ie one with a 29" front wheel and a 27.5"on the rear. You get the benefit of the 29er's ability to roll over stuff without your rear end getting buzzed when descending steep stuff, thanks to the smaller rear wheel.

I too have slightly shorter legs than you would think from my height and like Reaper, my only problems have been with droppers that are slightly too high even when fully inserted into the seat tube. I too had to swap a 150mm travel dropper for a 125mm. In my vase the original dropper failed and I was able to swap it for a 125mm travel.

I always end up pushing my saddle as far back as it will go. This is a consequence of my body being longer than is usual for my height. (That will be the same for you I expect).

I wouldn't be concerned about your long arms, modern bikes come with much wider bars than they used to. My first mtb had 625mm wide bars and my current one is 780mm. Stems have got shorter too (100mm down to 35mm).

Regarding the possibility of you going pedal assist and getting an emtb. I have had one since early 2019 and I'm on my second one now. They are not cheating and they are an abs9lute barrel of fun. But they are not the same. There is a lot to learn that is new and different. The best advice I can give is to sign up to the (free) emtb forum. Ask any questions you have; you will find many people willing to help.
https://www.emtbforums.com/

Edit: PS: In the absence of being able to sit on a bike before purchase, let the geometry charts be your friend. Compare things like reach and stack as well as seat tube length and crank length.