Confused with bike sizing.
 

Hi, Can you help me out with bike sizing, I'm 5' 8" – 171cm, inseam 32” - 81cm I been told I need a medium size , most medium size frams are 21” - 54cm, on canyon’s built insizing tool on their web site I put in my height and inseam and it told me I'm a XS 18.5 47cm can you advise thanks

Medium or around 54cm should be good for you. Mtb? 17.5-18.5" ish. XS? No way.

You buying a new bike? You really need to go by the manufacturer's suggested size for the particular model you are looking at when you lack your own experience. Even for older bikes you can sometimes find the sizing recommendation from the maker.

Just because you fit a certain size of one model doesn't mean that's the size you fit on another model.

A. Canyon sizing is different from every other manufacturer that I have experience with.
B. When I input the values you listed, it shows small, not XS.
C. My height and inseam is the same as what you listed, and my Canyon is a small and fits great.

this is not the first that I have heard of Canyon's fitting calculator giving whacky recommendations. I just plugged in your numbers on the Canyon site and it says you should be on a XS frame in the Grail 7 (I picked a bike at random). That's really weird.

I also just looked at their geometry and their sizing is weird. at 5'9", I would need a "small." my wife is short and she's a full 10 centimeters shorter than what their smallest bike should fit. why are they making their bikes so large?

Always test ride several bikes when you can, even two sizes of the same model. I found that I preferred the smaller size even when the manufacturer said I should go a size larger. In the case of manufacturers like Canyon that only sell direct, you might consider plugging them into bikeinsights.com https://bikeinsights.com to compare against other bikes you’ve actually thrown a leg over.

I agree with those who suggest test rides. A friend of mine and I both have a 56 cm frame Specialized Diverge. He is 6' 2", I am 5' 10". I believe manufacture recommended size is a good starting point but you may be plus or minus based on personal preference.

Knowing your preferred stack is a good starting point here. I largely ignore t-shirt sizing and seat tube or top tube sizing and just focus on stack and reach. To determine the stack and reach, find a bike that fits you well and either look up or measure the stack and reach on that bike.

Even knowing your stack and reach don't solve all problems. For example, my Giant Defy has a very tall measured stack. However, Giant has taken almost 15mm out of the fork length on the bike when compared to similar endurance models like the Domane. This makes the Defy actually have a more aggressive front end than a Domane or Roubaix despite what the stack measurement might lead you to believe. Similarly, a reach measurement doesn't account for the effect of the stem length and bar reach of a given complete bike. Stem length and bar reach can vary widely. For that reason, I also measured and memorized my preferred "true reach" from the nose of the saddle to the center of the lever hoods which allows me to determine if the stem and bar on a bike I'm considering are going to work for me. Snub nosed saddles have now screwed up even that measurement. Gah.

One note: Canyon's sizing is unorthodox, their bikes are generally significantly larger than the same t-shirt size on another brand. This is annoying given that Canyon is a direct sales brand and you can't try before you buy. BMC also has wacky sizing.

what specific Canyon bike(s) are you looking at?

I just checked the sizing for an Exceed hardtail and Canyon says I should get a small. I am 175cm tall with a 84 cm (actual) inseam and they say I should ride a bike with a 415mm reach, 597 stack, and 575 ETT. The 75° STA is on the steep side of a XC hardtail. that geo is consistent with "old school" XC sizing for a small bike designed for someone a few inches shorter than me. the only way that bike would fit me would be with a 100mm+ stem. I like a fairly compact fit on my mountain bike, so I don't know what Canyon is doing. I'll cross Canyon off my list of bikes I would ever buy because I can't see their sizing as anything other than totally whack.

I concur about Canyon sizing being different than most manufacturers. When I was thinking of buying an Inflite last year, I assumed I needed a medium (which would align with most other manufacturer's sizing), but when I ran through the Canyon bike fit calculator, it recommended a Small.

You are the same height and inseam as me. A lot of manufacturers have us in the overlap area between med and small. I go for mediums now, years ago I would go small for a "race fit".

True that. Lots of new frame designs are being rolled out, and geometries vary, especially between bike type (road, mtb, hybrid, etc.) Not something you want to get wrong, if you can't try the bike you're considering.

mtb chart/
 

Both the SM and XS will fit.
171cm, I would go for the XS. SM will work but you may not be able to get your position correct on it.

Unless you have a good handle on bike fit, buying a bike by mail is a dodgy proposition. I bought an Endurace from Canyon this summer. Given my height and inseam (6', 34.5"), Canyon would have had me on a Medium. I already have 3 bikes set up within a few mm of each other that all work great for me, so I measured them carefully and worked with the Canyon geometry table to determine what would fit - a Large. When I got it, I set it up as close to the other bikes as I could, and it's perfect. The Medium would have had the bar much too close for me.

So, I'd only order by mail if I knew exactly how I wanted to set it up, and determined what size would allow that. Otherwise, it's kind of a crap shoot.

^^^ All of this ^^^ Get a profressional fit and get your stack and reach, especially if you're going to mail order that big of an investment.. You sound like you have long legs. I'm four inches taller than you and have the same inseam. Maybe I have short legs :)

I'm 5' 9" with a 33" inseam. I ride a 54cm road bike and a 54cm gravel bike. That's "my size," just as it has been since about 1979. But on an All City Nature Boy, I'm a 49cm. On a Breezer Radar, I fit a 51cm. On a Black Mountain Road Plus, it's a 47cm. In general, the top tube length, stack, and reach are the measurements you need to pay attention to; these days, you can pretty much ignore the seat tube measurement, and any S, M, L, XL designations.

I agree with the above, except when it comes to Canyon. Take a look at their size designations and the geometry associated with those. It's totally silly.

I think for Road and Gravel bikes, this is pretty spot on.

Now that I know my exact fit on a bike, with Reach, Stack, Head Tube Angle and a good calculator, I’ve been able to nail within +/- 10mm how I am going to fit on a bike (assuming I use my same bars).

Of course, you are trusting that they have the measurements right. But most of the time if they are going to bother giving reach and stack it is an indication that they take sizing accuracy seriously.

Start with saddle height. From that and some idea of desired saddle to bar drop, a proper stack can be determined. Reach will be in the 370-380 range.

Size numbers and letters mean little. I also look at seat tube length because I have long legs for my for my 5'-6" height. My saddle height is 73cm and I set my bar height to produce a 10cm saddle to bar drop.

I normally look for a stack that's no more than 527mm. I now have an XS or 46cm Cinelli superstar with a 509mm stack. It requires 15mm of spacer on top of 15mm headset top cover, with a -17 stem, or a 30mm headset top cover. A -6 stem would raise the bars by about 2cm. The 46cm seat tube is on the short side, but anything in the 45-48cm range will work.