Another day, another bike sizing geo post. So apologies in advance!

So…. i have my eyes on a new frame (Vitus Sommet). Vitus say i should be on a medium, as per my height (175cm and inner leg measurement 80cm). But looking at the reach and stack figures, compared to my current and previous bikes (Specialized Status in S3 and Norco Optic in Large) the figures of those are much closer to a Large Sommet. Apart from the wheel base, which is quite a chunk longer.

I have an irrational fear of buying a bike too short and feeling cramped, but equally dont want one that is going to feel like a oil tanker. My head says go medium, my heart says go large. Which when typing it, seems somewhat silly, so maybe i have answered my own question.

Just to add further info, i have a Ragley Big Al hardtail in medium, which i have no issues riding and is again similar figures to the medium Sommet. But that could be complimented by a longer, big travel bruiser in the form of a large Sommet?!

So i think i basically if someone can give me a dry slap and tell me to follow the manufacturers recommendations, that would be great. Or tell me to ignore them and just go with the figures….?!?

Someone put me out of this perpetual misery of comparing numbers on geometrygeeks and coming to no conclusion!!

Many thanks!

i feel your pain 😀

Go on your own numbers and thoughts – not on the manufacturer’s recommendations. All day long. As long as you know what you like and what you’re looking for, which it sounds like you do.

Beware delaying though on those Sommets. I set up a stock alert on a XL frame in April and they finally arrived in stock yesterday (only 3 available). I imagine they’ll not hang around long.

Agree with a11y. Trust your own numbers and thoughts. I prefer bigger MTBs and smaller road bike to manufacturer recommendations. Most MTB manufacturers would have me at the top of a medium frame, whereas I prefer to be at the bottom of a large frame with a short wheelbase. The opposite is true for road bikes.

Why would they know what size bike you need better than you?

Those manufacturer sizing charts are for noobs.

Get the large.

Numbers, always the numbers. The manufacturer doesn’t know your preferences and experiences. Ignore the labels S, M, L and so on and use the data that you seem to understand fine

@a11y – well my credit card took a right bashing yesterday, as i got the stock alerts, quickly bought a large, then panicked and bought a medium!

I was hoping to have my dilemma sorted before they arrive so i can just return one straight away.

I appreciate the advice thus far.

The Large also seems to have a higher stack than my current bikes. Is this something to be wary of, or easily solved with a lower rise bar, less spacers under the stem etc?

I sometimes feel like i have a grip on bike geo and sizing, then the next minute i feel like i dont have a clue 😛

The Large also seems to have a higher stack than my current bikes. Is this something to be wary of, or easily solved with a lower rise bar, less spacers under the stem etc?

Kinda depends, are you running some spacers at the moment? If so, you should be grand. If you already have your stem slammed then you might struggle to get back to the same height

@mashr – currently have spacers on the Status, i would say 20-25mm off the top of my head. So in theory i can use less on the Sommet and have a similar stack height?

Yup, exactly that

I had a similar experience recently, looking at a new road bike. When I plugged my measurements into the Canyon website it recommended a Small. That was enough to make me discount them as an option.

179cm here, long back, short legs.  I just take the geo of the bike I’ve ridden the most (V1 RipMo) and try and get close to reach, stack, standover (short legs remember!) and how much dropper I can fit.

On my original FlareMax and SolarisMax, Cy reckoned I’d be better on a L, but I went M. Both would have been fine.

Geo now tho defo suits the dwarf legged rider. My Turner 5 Spot was a L (19.5 seat tube) because the M was way too short. But looking back, can’t believe how little post I was running.

So I’d go with what is closer to what you ride already and tweak from there

Always follow the numbers.

@scotroutes – exactly the same happened to me yesterday. In a bid to try and gain more info, i put my details into their size guide and it came out as a small. Makes me think i have either been riding the wrong sized bikes for a long time…. or Canyon’s system is whack!

Again, i appreciate the opinions, which are 100% go with the digits!

I’m similar to @alex, 178cm but short legs long body. I have a large 2020 Hightower, a medium Scandal, and a Medium Sonder Camino.

All were very calculated decisions based on my current or previous bikes and a few key things such as what size dropper I want to run.

I ride the large Hightower because I needed the top tube length, and I wanted to run a 35mm stubby stem. However this means I can only run a 125mm dropper. I could have bought a medium, run a 150mm dropper but probably had to run a longer than optimal stem.

I remember years ago buying a Boardman FS and I had to literally take my old seatpost in with some tape marks on it to work out whether I could get away with the large and still be able to fit the dropper in.

Key point – if you havent previously done so, remember that dropping to 165mm cranks can make the difference in being able to ‘size up’ or not. If i had 175mm cranks on my Hightower I wouldnt be able to fit my seatpost in.

ETA – even the difference between flats and SPDS!Riding flats means I need a 5-10mm shorter seatube than I would were I on SPDs due to lower stack height. You can also get some saddles which are shallower than others.

Its worth the effort doing some proper analysis of the numbers and measuring of your current bikes, particularly BB to saddle.

Good points there @snotrag.

The dropper is interesting. On my RipMo(L) and my Bardino (ML) I can fit the 210mm oneup dropper (just). On my new Rascal, I knew it was going to be a problem as there’s a bit more extruding seat tube.

With flats, shorter cranks and a slacker seat angle than the RipMo, I still managed 200mm. I’d kind of set myself a target of 180mm after looking at the numbers, so I was very happy with that.

I know there’s a few on here that don’t like/need to get the saddle all the way down, but I’m a big fan, so that’s an important part of the Geo for me.

Large 5-Spot

Large RipMo

Defo improvements for us shorter in the leg!

@snotrag @Alex – many thanks for that input. I didnt really consider seat post insertion.

I have a 170mm AXS reverb, which currently sits a fair way out of the frame on my Status, so that shouldn’t be an issue. But i will definitely measure the length between the couple of bikes i have. I suspect in theory they should all be the same/similar measurement?!

I’m a similar height as you, with a slightly longer inner seam.

I was in a similar quandary 2 years ago (2019 model Sommet). I went with their height charts and ordered the medium. It was far too small… I returned it and ordered a large*. The large was perfect.

*The forgotten luxury of bike availability… and discounts!

Two things I measure, centre of botom bracket (assuming you’re running the same crank lengths) to bottom of saddle rail. Then how mich of that distance is ‘above’ and ‘below’ the seat tube. Which is a check for ‘can I get all the ‘dropper’ bit above the tube and is there enough room for the non dropper part to fit into the seat tube.

Yep, good points by @snotrag, particularly crank length effect on ST length. I found that when swapping between flats and SPDs and having to lower my seatpost height by 5-10mm when on flats.

I like a long bike but – despite ST lengths generally getting shorter with modern bikes – still need to be aware of tall ST lengths limiting my dropper length. At 187cm I can’t go longer than a 500mm ST if I still want to use a 200mm dropper. It’s a close thing on my current bike with my dropper almost completely slammed – I could try a dropper with a lower stack than my Brand X one, but it’s fine.

@v7fmp – good choice! (although sounds like its the large for you…). I’m quite glad of the out of stock delay as its put me onto a completely different bike and geometry approach entirely.

I’m still quite old school with my bikes and have decided that, unless an absolute bargain comes about that may work, I’m going to need to try before i buy.

6’2 long torso, short legs. Have ridden L/19″/20″ bikes for all time. looking at geo and recommendations, I’m on the cusp of L/XL for most manufacturers.

however, it’s not that simple.
bike I liked riding, an old Fisher 29er, 19″/L with 100mm stem,seat back on the rails of an inline post. worked a charm.
bikes I currently run.
old pace RC129, large/18.5″ seat tube. short. but feels spot on with a 80-90mm stem, seat slightly back from mid point on an inline post.
Pinnacle ramin v1. large (says on it up to 6’1) pretty similar reach and geo to the fisher, albeit slightly slacker head angle. works very well with a 80mm stem and the seat mid point on an inline post.

My take on this is simple:
– first, if unsure, try before you buy.
– if you don’t have lots of experience with different geo styles, following the brand’s chart will generally direct you towards the “feel” they imagined for the bike.
– some will have enough experience with different bikes to know what they like and what fits them. In this case, just follow the numbers of your preference.

more great advice, cheers folks.

To add another set of numbers into the mix, a riding buddy said he concentrates more on the seated position and the effective top tube length as ‘thats where you spend most of your time’.

i always thought that rang true with road bikes, as you do spend 99% of your time seated, but less so with a mountain bike?

Given the amount of out-the-saddle riding with MTBing, reach is equally important than ETT for MTBing. TBF to your mate they’re not (completely) wrong in mentioning ETT as it all needs to be taken into consideration together: ETT, reach, SA, stack, HA, etc.

An example: I changed from a frame with 65.5 HA, 471 reach, 1253 wheelbase and 74.0 SA, to the one above with 64.5 HA, 535 reach, 1341 wheelbase and 77.0 SA, but my ETT only increased from 675 to 686 due to the steeper SA. So we can’t consider/put too much weighting on one measurement in particular.

@a11y – fair play. It is a measurement on my radar, but considered that all the current bikes i have ridden have been fairly modern geo, it wouldnt be a million miles away from a sensible increase with the larger sizes.

I will get both out the box when they arrive and offer them up to my current bikes and have a think, but certainly sounds like the large is the way to go.

Cheers everyone!