# Sizing Inquiry when falling between two sizes



## Dirt_Devil (12 mo ago)

I have my eyes set on the Polygon Siskiu T8, but based on the sizing chart, I fall right in between Medium and Large as I'm 5'9". When you fall in between sizes, is it better to go down (medium) or up (large)?

Since the Polygon is a direct-to-consumer bike, I'm unable to test ride and compare the sizes. I went to a bike shop to get some general thoughts and they recommended a medium at my height because it would be better to handle. But I just wanted to get some other opinions before making the purchase.


----------



## yzedf (Apr 22, 2014)

Trying to go fast, riding steeper and faster trails - Large

More about having fun, jumping out really tight trails - Medium


----------



## Moosedriver (Jan 19, 2021)

I’d also say that your body dimensions other than just height play into the determination as well. If you have a long torso and short arms and legs, a medium would probably work better. Long arms and legs, large would probably be better. 

Is it possible to look at the geometry of the Polygon and see if any bikes at your LBS come close to the same numbers? It wouldn’t be a perfect way to compare sizes, but it may get you close enough for you to make a more informed decision. You also might find that you really like one of their bikes in the process. IMO, it’s often better to go with what you can demo until you determine what geometry you like, then move on to a direct-to-consumer brand instead of taking a shot in the dark on what you might like based on what people that you don’t know on the internet say.

For what it’s worth, I’m 5’9.5” with average torso and arm/leg lengths and went medium on my current bike, thinking along the lines of it being easier to maneuver over being at the bottom of the large size range. I’ve spent a lot of time changing stems, bars, adjusting bar and seat positions because the cockpit feels cramped to me. I have made a big improvement after multiple changes, but I still feel like I have a very small area to adjust my body position while riding. I wish I had gone with a large.


----------



## KobayashiMaru (Apr 25, 2020)

I'm 5'10".

This is me thinking about how buying a modern large (because everybody thinks that's what a rider my size should ride) ended up working out:


----------



## LVLBTY (Jul 15, 2020)

The smaller size is most definitely going to be more playful as long as the cockpit fits you.


----------



## NORCAL1979 (Jan 18, 2013)

I am 5'9 as well and fall in between sizes too. What has worked for me in the past was to go with the medium frame bike and size the cranks down by 5mm. This change will give you more room by pushing you up and back just a little bit. Also, you can try going with a stem that is 10mm longer. The crank change will make the greatest difference.

My current bike is a 2021 Stumpjumper Evo size s4 (Large). Unfortunately the S3 (medium was just too cramped and I felt that a crank swap wasn't going to make enough of a difference. I purchased the S4 size for this reason and figured that I could make some changes to shrink the cockpit reach a bit. I ended up going with a 35mm stem positioned lower on the stack to bring reach in even further then went with 770 bars with a 38mm rise to regain the stack height. The fit is much better with these changes however it still feels a tad bit stretched and not as comfortable as the medium with crank swap.

Given my experience, I would advise going with a Medium and doing the crank/stem swap as this will probably make for a more comfortable bike to ride.


----------



## maynard4130 (May 12, 2019)

I always go with the smaller size. Slide the seat back. Kept the stock stem instead of a shorter one like most guys do and you should be fine


----------



## blcman (Feb 1, 2007)

What yzedf stated earlier is similar to how I would perceive sizing, but with a slight change. I'm 5'9". .Smaller size is playful and twitchy
and larger sizes are more for stability at speed! I, being an older rider, prefer the larger size bike as it let's me to be able to ride faster
without needing to be "on" all the time. It's more forgiving to rider input!


----------



## LMN (Sep 8, 2007)

Four years ago the rule was size up. I don't think that holds any more.


----------



## DeoreDX (Jul 28, 2007)

I have two datum points for you. I am 5'8" with long torso and short legs (Wear 29 inseam pants). I have a Medium 27.5 D7. I would say it fits but it's closer to being too small than too big. IIRC 29er D7 is a little bigger.

I rode a Large size T7. It felt too big for me mostly in the vertical direction. 170mm dropper was way too long. I thought the stack felt way too tall but some people like the big stack like they are sitting up straight on a beach cruiser. Doesn't feel as effective boosting on jumps since I don't get maximum leverage and extension at full boost. Length was OK and manageable. Knowing the T7/8 is a little bigger than the D7 I might lean towards the Medium on the T7/8. I will favor a smaller bike over a larger bike 9 times out of 9 though.


----------



## Sparticus (Dec 28, 1999)

yzedf said:


> Trying to go fast, riding steeper and faster trails - Large
> 
> More about having fun, jumping out really tight trails - Medium


This ⬆ ⬆ ⬆ is good advice.
If you know which type of riding you favor &/or whether your fit preferences lean toward smaller or larger frames, you've got your answer.
Personally I prefer to size up but I believe I'm in the minority on this.
The good news is you could probably flip a coin and once you've had the bike for a few rides & get used to it, you'll likely be happy with it regardless.
Being in the middle isn't so bad -- it usually means you're good to go in either direction.
=sParty


----------



## dllawson819 (Feb 22, 2019)

yzedf said:


> Trying to go fast, riding steeper and faster trails - Large
> More about having fun, jumping out really tight trails - Medium


I agree, this advice is a good starting point. 

I used Lee McCormack's RAD guide to fit my current bike. Dynamic MTB Fit – Lee Likes Bikes (It looks like he has adjusted his recommendations to account for recent trends in frame design.)

I am also 5'9" and in between Ibis frame sizes. I chose a medium Mojo SL-R based on Lee's RAD recommendations and love the way the bike handles. I think I would feel more comfortable on a large in the parking lot, but on the trail the medium is perfect.


----------



## Sidewalk (May 18, 2015)

Don't use the sizing chart, use actual numbers.

I just bought an XC bike, sizing chart had me on a medium. However, the numbers showed that the small was nearly the same size as the two medium bikes I already had that I was comfortable on. The medium was about the same size as the large frame bikes I had in the past that were too big.

I bought the small, and it fits me well. I even have the seat slide forward.


----------



## jeremy3220 (Jul 5, 2017)

Depends on how that bike model is sized. Some bikes are sized small and some sized big. I go based on geo numbers but if you don't know what you're looking for I'd post this question in the Polygon sub forum and get responses from actual owners of the model you're looking at. I think using generalities about sizing up or down is a bad idea. I have a friend who is between sizes and he sizes up or down depending on the actual reach, stack, etc of the bike.


----------



## john1970 (Apr 11, 2009)

I also had the same experience when ordering my 2022 Trek Top Fuel 9.7. I am 5' 10.5" in height with 32" inseam and 35" sleeve length. Originally I ordered a M/L, but a couple of weeks later I tested a 2022 Trek Top Fuel 8 in M/L and L. For me the M/L was cramped and after riding it on a dirt path for about 20 min my lower back was bothering me. In contrast, the L felt more natural and was more comfortable. 

If at all possible try to ride both sizes before making the purchase.


----------



## ocnLogan (Aug 15, 2018)

Dirt_Devil said:


> I have my eyes set on the Polygon Siskiu T8, but based on the sizing chart, I fall right in between Medium and Large as I'm 5'9". When you fall in between sizes, is it better to go down (medium) or up (large)?
> 
> Since the Polygon is a direct-to-consumer bike, I'm unable to test ride and compare the sizes. I went to a bike shop to get some general thoughts and they recommended a medium at my height because it would be better to handle. But I just wanted to get some other opinions before making the purchase.


I think the shop was spot on with their recommendation. At least generically speaking. But as others have said, your specific body dimensions (inseam, torso, and arm length specifically) and your style of riding could change that one way or the other. But I'd say 5'9" is pretty darn close to the spot on for a medium.

The Medium T8 has 460mm of reach, and 607mm of stack. 

Anecdotally, I have a buddy who is 5'8" and rides a 2018 Kona Process 153 in size medium... That bike has 450mm of reach, 607mm of stack and he's actually wanting to downsize to a smaller bike lately.


----------



## Harold (Dec 23, 2003)

Moosedriver said:


> I’d also say that your body dimensions other than just height play into the determination as well. If you have a long torso and short arms and legs, a medium would probably work better. Long arms and legs, large would probably be better.
> 
> Is it possible to look at the geometry of the Polygon and see if any bikes at your LBS come close to the same numbers? It wouldn’t be a perfect way to compare sizes, but it may get you close enough for you to make a more informed decision. You also might find that you really like one of their bikes in the process. IMO, it’s often better to go with what you can demo until you determine what geometry you like, then move on to a direct-to-consumer brand instead of taking a shot in the dark on what you might like based on what people that you don’t know on the internet say.
> 
> For what it’s worth, I’m 5’9.5” with average torso and arm/leg lengths and went medium on my current bike, thinking along the lines of it being easier to maneuver over being at the bottom of the large size range. I’ve spent a lot of time changing stems, bars, adjusting bar and seat positions because the cockpit feels cramped to me. I have made a big improvement after multiple changes, but I still feel like I have a very small area to adjust my body position while riding. I wish I had gone with a large.


You just contradicted yourself in your own post.

The length of the bike is the least adjustable part of it, so get that right first. If you have a long torso and/or long arms, you are going to feel a more comfortable on a long bike. So size up. If you have a short torso and/or short arms, then sizing down is going to give you more range of motion.

If standover clearance becomes a problem for a bike that's the correct length, then you should look at a different frame that has better standover clearance for your size, instead of sizing down, because that's going to cause different problems with a cramped cockpit.

standover clearance should never be a determinant of which frame _size_ you should ride. If standover clearance is a priority for you, then use it to filter different bikes that DO fit in the important metrics.


----------



## Sparticus (Dec 28, 1999)

Harold said:


> You just contradicted yourself in your own post.
> 
> The length of the bike is the least adjustable part of it, so get that right first. If you have a long torso and/or long arms, you are going to feel a more comfortable on a long bike. So size up. If you have a short torso and/or short arms, then sizing down is going to give you more range of motion.
> 
> ...


This ⬆ is insightful.

I've noticed a frame sizing trend since droppers have gotten longer, and it is this. Standover doesn't change much anymore. Shorter riders need all the room they can get (short seat tubes) and taller riders want room for a 200mm+ dropper (also short seat tubes). So what makes up the biggest difference in frame sizes?

Cockpit length.

Size-specific chainstays have recently become a thing, too.

Seems head tube length doesn't vary more than 5-20mm between XS - XL frames these days.
=sParty


----------



## s0ckeyeus (Jun 20, 2008)

dllawson819 said:


> I agree, this advice is a good starting point.
> 
> I used Lee McCormack's RAD guide to fit my current bike. Dynamic MTB Fit – Lee Likes Bikes (It looks like he has adjusted his recommendations to account for recent trends in frame design.)
> 
> I am also 5'9" and in between Ibis frame sizes. I chose a medium Mojo SL-R based on Lee's RAD recommendations and love the way the bike handles. I think I would feel more comfortable on a large in the parking lot, but on the trail the medium is perfect.


What part do you think has changed? I don't think he's really modified his viewpoint much, if at all.

RAD has worked super well for me. I bought an Ibis Ripmo AF a couple weekends ago. I walked in with a string, a measuring tape, and my RAD number and walked out with a bike after only test riding one bike. I knew it fit, and it felt like I wanted.

To the OP, I wouldn't trust the size charts. They don't necessarily correspond to much of anything.


----------



## Moosedriver (Jan 19, 2021)

Harold said:


> You just contradicted yourself in your own post.
> 
> The length of the bike is the least adjustable part of it, so get that right first. If you have a long torso and/or long arms, you are going to feel a more comfortable on a long bike. So size up. If you have a short torso and/or short arms, then sizing down is going to give you more range of motion.
> 
> ...


My opinion stands and I do not consider that I contradicted myself. The only part of my post that appears you feel that I contradicted myself on is torso length, which made you feel that my entire post needed to be specifically called out. Many people that I’ve met with long torsos have shorter arms and legs, which will cause problems fitting on a larger frame. My statement was “long torso and short arms/legs”, then made a separate statement on those that have long arms, but did not include a torso descriptor. I do agree with you on those people who have both long torsos and long arms, but felt that was covered by my “long arm” statement. I admit that I could have done a better job and will concede that I unintentionally omitted the group of people with both long torsos and long arms, and for that I apologize.


----------



## Harold (Dec 23, 2003)

Moosedriver said:


> My opinion stands and I do not consider that I contradicted myself. The only part of my post that appears you feel that I contradicted myself on is torso length, which made you feel that my entire post needed to be specifically called out. Many people that I’ve met with long torsos have shorter arms and legs, which will cause problems fitting on a larger frame. My statement was “long torso and short arms/legs”, then made a separate statement on those that have long arms, but did not include a torso descriptor. I do agree with you on those people who have both long torsos and long arms, but felt that was covered by my “long arm” statement. I admit that I could have done a better job and will concede that I unintentionally omitted the group of people with both long torsos and long arms, and for that I apologize.


it doesn't have to be just long torso AND long arms. either could put you into a bigger size. I have an avg torso and long arms, but am otherwise a "solid" medium. on some bikes, larges definitely fit me better. if I like a medium, chances are it's a longer bike. my wife has an average torso and short arms, and she absolutely has to size down, but her height alone puts her as a solid small. it all depends on your specific body proportions. it's possible to have a long torso and short arms that effectively counteract each other. but it's also possible that they don't. my point stands, that you need to fit the LENGTH of the bike first, before you mess with anything else. and if any dimensions of your upper body are longer than average, you need to strongly consider sizing up.

where you contradicted yourself is where you talked about what's working for yourself (or not) compared to the recommendation you make.


----------



## Moosedriver (Jan 19, 2021)

Harold said:


> it doesn't have to be just long torso AND long arms. either could put you into a bigger size. I have an avg torso and long arms, but am otherwise a "solid" medium. on some bikes, larges definitely fit me better. if I like a medium, chances are it's a longer bike. my wife has an average torso and short arms, and she absolutely has to size down, but her height alone puts her as a solid small. it all depends on your specific body proportions. it's possible to have a long torso and short arms that effectively counteract each other. but it's also possible that they don't. my point stands, that you need to fit the LENGTH of the bike first, before you mess with anything else. and if any dimensions of your upper body are longer than average, you need to strongly consider sizing up.
> 
> where you contradicted yourself is where you talked about what's working for yourself (or not) compared to the recommendation you make.


Ok, so I first state that more than just height needs to be taken into account for sizing, then make the statement that I’m average height, average torso, and average arm and leg lengths and went with a medium. I then determine that I felt the cockpit is cramped for me and I spent time changing the cockpit to be more comfortable for me. What exactly is being contradicted?

Edit: or was the contradiction that I said the OP should ride some demos to determine first hand what works rather than just listen to internet strangers and then added my backstory afterwards? If so, then I agree, that could be seen as a contradiction. Good job to you for pointing it out.


----------



## Harold (Dec 23, 2003)

Moosedriver said:


> Ok, so I first state that more than just height needs to be taken into account for sizing, then make the statement that I’m average height, average torso, and average arm and leg lengths and went with a medium. I then determine that I felt the cockpit is cramped for me and I spent time changing the cockpit to be more comfortable for me. What exactly is being contradicted?


you forgot the part where you said if you have a long torso and short arms that you should size down. so they can have a cramped cockpit, too?


----------



## Moosedriver (Jan 19, 2021)

Harold said:


> you forgot the part where you said if you have a long torso and short arms that you should size down. so they can have a cramped cockpit, too?


Ok, you just literally stated my contradiction was based off what worked or didn’t work for me, but now it’s back to long torso and short arms? I think you’re just stretching so that you can feel your comment about a contradiction makes sense. Maybe I’m missing something here, but I guess we’ll just continue to disagree with each other without either one of us budging. So, I will just leave it with: Have a great day.


----------



## Harold (Dec 23, 2003)

Moosedriver said:


> Ok, you just literally stated my contradiction was based off what worked or didn’t work for me, but now it’s back to long torso and short arms? I think you’re just stretching so that you can feel your comment about a contradiction makes sense. Maybe I’m missing something here, but I guess we’ll just continue to disagree with each other without either one of us budging. So, I will just leave it with: Have a great day.


let me write it out more simply. 

you said early in your post that someone with a long torso and short arms should size down.

then at the end of that post you said that you have fiddled so much with your own bike (where you had sized down) and still aren't quite there...such that you wished you had sized up.

these two things are contradictory.


----------



## Moosedriver (Jan 19, 2021)

Harold said:


> let me write it out more simply.
> 
> you said early in your post that someone with a long torso and short arms should size down.
> 
> ...


Let me reply more clearly.

If I had stated I have a long torso and short arms and downsized and felt that my cockpit was cramped AND THEN recommended the OP do the same if he has a long torso and short arms, then I agree that would be a contradiction.

But, that is NOT how I described myself. I stated I have average torso, arm, and leg lengths. The first statement was my recommendation for someone with a specific type of body dimensions, the second statement was my personal experience with a different type of body dimension. There is NO contradiction because those statements are mutually exclusive.


----------



## Steel-Onions (Sep 3, 2021)

I kinda go with the theory that its easier to make a large bike 'smaller' to fit you (stem, seatpost etc), than to make a small bike 'larger' to fit you (stem, seatpost etc)' without messing up so much the intended 'geometry/balance'?, so in your position id take the large and be prepared to change a couple of parts if i really could not get along with it


----------



## s0ckeyeus (Jun 20, 2008)

Steel-Onions said:


> I kinda go with the theory that its easier to make a large bike 'smaller' to fit you (stem, seatpost etc), than to make a small bike 'larger' to fit you (stem, seatpost etc)' without messing up so much the intended 'geometry/balance'?, so in your position id take the large and be prepared to change a couple of parts if i really could not get along with it


That's assuming the larger bike isn't actually too big, which sometimes they are if just going off the mfg's site. 

Example: I just bought an Ibis Ripmo AF a couple weeks ago. By the size chart, I'm between a LG and XL, when in reality the LG was actually a little big for me. The large I bought actually came with a 10mm shorter stem than it was supposed to, which ended up being perfect. I could have made the XL work, but the LG with the shorter stem fit way better. 

Bike sizing can get kind of confusing. It's better to know real measurements that work for you and match those to the bike than rely on the sizing sticker.


----------



## harambe2 (Aug 31, 2021)

I’m 5’8 with a 32.5” inseam (no shoes), so more legs than torso. Neutral ape index. I ride a medium T8 and it fits me very well. If you have a longer torso, I can see you potentially with a large, but with my measurements, I would not want to be on a large. For comparison sake, the T8 medium fits me better than than the intense primer medium. 

I did need to size to a 200mm dropper with about 2-3 inches of seat post showing though.


----------



## des1401 (Jan 10, 2022)

harambe2 said:


> I’m 5’8 with a 32.5” inseam (no shoes), so more legs than torso. Neutral ape index. I ride a medium T8 and it fits me very well. If you have a longer torso, I can see you potentially with a large, but with my measurements, I would not want to be on a large. For comparison sake, the T8 medium fits me better than than the intense primer medium.
> 
> I did need to size to a 200mm dropper with about 2-3 inches of seat post showing though.


Hi - I'm pretty close to your stature (5'9" with a 33" inseam) and thinking a bit about the T7/T8. Your dropper seems quite long, do you use that much? They offer a 170 in the large/xl, which I would have thought would be more than sufficient. Did you upgrade your dropper yourself, or were you able to custom order? 

Did you get a 29er? (I'm thinking I want the 27.5+ if it can go 2.8 wide enough on the tires. I can't seem to find that spec).

Thanks.


----------



## harambe2 (Aug 31, 2021)

des1401 said:


> Hi - I'm pretty close to your stature (5'9" with a 33" inseam) and thinking a bit about the T7/T8. Your dropper seems quite long, do you use that much? They offer a 170 in the large/xl, which I would have thought would be more than sufficient. Did you upgrade your dropper yourself, or were you able to custom order?
> 
> Did you get a 29er? (I'm thinking I want the 27.5+ if it can go 2.8 wide enough on the tires. I can't seem to find that spec).
> 
> Thanks.


I bought a 200mm PNW Loam, but one key piece is that I switched out the 170mm cranks to 165mm. L/XL has 175mm cranks, so you might be good with the 170mm dropper. The 200mm dropper would be too short for me if I slammed it all the way into the seat post. I had to move it so that 2-3 inches of the dropper post is exposed.

I have the M 27.5", but the measurements are nearly identical to the 29er. You should try sending them an email to ask about wheel width. They are missing a lot of measurements that other companies would normally post.


----------



## des1401 (Jan 10, 2022)

harambe2 said:


> I bought a 200mm PNW Loam, but one key piece is that I switched out the 170mm cranks to 165mm. L/XL has 175mm cranks, so you might be good with the 170mm dropper. The 200mm dropper would be too short for me if I slammed it all the way into the seat post. I had to move it so that 2-3 inches of the dropper post is exposed.
> 
> I have the M 27.5", but the measurements are nearly identical to the 29er. You should try sending them an email to ask about wheel width. They are missing a lot of measurements that other companies would normally post.


So many variables makes it very hard to figure out how to go. Based on your comment, I was thinking that your 200mm post couldn't go down the final 2", not that you were running it at that point. 
I have a query into customer service to see if they can provide the widest tire. I noted that the 29 is listed, but not the 27.5.

Thanks.


----------



## harambe2 (Aug 31, 2021)

des1401 said:


> So many variables makes it very hard to figure out how to go. Based on your comment, I was thinking that your 200mm post couldn't go down the final 2", not that you were running it at that point.
> I have a query into customer service to see if they can provide the widest tire. I noted that the 29 is listed, but not the 27.5.
> 
> Thanks.


Ahh, I could see the confusion.

The 27.5 only comes in size small and medium, so if you need L or XL, you have to do 29”.


----------



## dllawson819 (Feb 22, 2019)

s0ckeyeus said:


> What part do you think has changed? I don't think he's really modified his viewpoint much, if at all.
> 
> RAD has worked super well for me. I bought an Ibis Ripmo AF a couple weekends ago. I walked in with a string, a measuring tape, and my RAD number and walked out with a bike after only test riding one bike. I knew it fit, and it felt like I wanted.
> 
> To the OP, I wouldn't trust the size charts. They don't necessarily correspond to much of anything.


RAD has also worked very well for me. I don't think Lee's recommendations have changed, but I don't remember seat angle or standing fit being discussed the last time I bought a bike (early 2019).

It is interesting that Specialized has moved from S,M,L to number sizing. Seems to be a validation of RAD.


----------



## s0ckeyeus (Jun 20, 2008)

dllawson819 said:


> RAD has also worked very well for me. I don't think Lee's recommendations have changed, but I don't remember seat angle or standing fit being discussed the last time I bought a bike (early 2019).
> 
> It is interesting that Specialized has moved from S,M,L to number sizing. Seems to be a validation of RAD.


Thanks for clarifying. RAD has pretty much exclusively been standing position with the saddle adjustment being mostly independent. I think Lee's softened on RAD+, but most of the messaging seems to have staid consistent since 2016, when I first heard of it and started using it.

As I alluded to earlier, sizing based on RAD made my last purchase pretty easy. Since buying the bike, I discovered that it came with a shorter than advertised stem. Lucky for me since I wasn't concerned with the advertised numbers or sizing, I ended up with a bike I didn't have to modify to fit. I would have gone down to a 40mm stem anyway, instead of the 50mm that was supposed to come on the large.


----------



## dundundata (May 15, 2009)

I say depends what you like. Personally I prefer a bike a tad too small vs too big. If I was bombing downhills I might prefer the larger size but for general trail riding I think the smaller size is easier to maneuver and toss around, and prefer the lower seat/top tubes and stack height.


----------



## durask (Nov 16, 2020)

john1970 said:


> If at all possible try to ride both sizes before making the purchase.


That would be nice, but around here bike shops will just let you sit on a bike in the store. Asking to actually ride it, even for a couple of minutes in the parking lot - forget it.


----------

