Confused as hell on modern geometry fit

[jacob_dbu]

I definitely did not like the super steep seat tube angles, but I do like the longer reach for steep trails. I think I could have gotten used to it, but I settled on a bike with a slightly more traditional seattube angle (e.g. 75.5-76 vs 77/78 of some of the ultra-modern bikes).

I sized up and went for a large when I was between M and L and I'm still not 100% sure that was the right choice, but I am getting more used to it. Partially because the large is what I could find at a price I wanted.

[supermodel159]

Get the XL.

[XXX-er]

Ibis rec had me firmly in a Large Ripmo AF. I bought a medium based mostly off how my previous bike feels and its reach/stack. I also tinkered with Lee’s RAD formula and measurements and think there’s something to it. My medium is RAD+.

The medium fits perfect even with my short legs and long arms. Super stable on the down but way easier to maneuver on technical ups than a large would have been. I’m now in the camp that believes size recommendations have gotten too big.

how tall are you ?

both SC and Yeti put me on a medium at 5'8" and that has been perfect, i think they both fit the same at least in medium

I initialy took out a large Yeti 5.5 cuz I could ride an already dirty large shop bike but it felt long and it was 1 " longer TT than medium, bought the medium and it was perfect

[Eluder]

There are lots of numbers that come together to make any given bike what is, some of which isn't visible in the published geo chart. We all have our personal bias but I think in general if you are a large you are large in how that company has decided to build their bikes. Sizing down or up can push a bike out of how it was conceived when in actuality you would probably be better served on a bike designed around different parameters. For sure this doesn't help if you truly are between sizes but it sure seems most people that are "between" sizes should be on the bigger bike but are hesitant.

I am sure I am opening a can of worms here but If you really think you know better than the bikes designer than why are you buying bike from them?

[J. Barron DeJong]

How come Ibis can’t convert between cm and inches properly?

173 cm is not 5’7”. 198 cm is not 6’5”.

Get the XL. Put a 50mm stem on it and go ride.

[toast2266]

I am sure I am opening a can of worms here but If you really think you know better than the bikes designer than why are you buying bike from them?

I am 100% confident that bike designers can't give a single recommendation that works for every person in every location.

Case in point: Jack Moir races on a size small Canyon Spectral. He's 6'1" and can get whatever size bike he wants. His decision appears to be working for him, despite Canyon's sizing recommendations.

edit: don't you have both a medium and a large in the exact same bike from the company you work for?

[EWG]

X2 on paying attention to the effective top tube length. You spend a lot of time seated and pedaling, and if your ETT is too long or too short, you'll be uncomfortable. What was a comfortable ETT on a bike 10+ years ago isn't any different now. Yes, a steeper seat tube will mean your seated body position is different relative to the BB, but don't worry too much about that; for most people, that's easy to adjust to (or sometimes not even all that noticeable).

Also agreed with your conclusion that you're kinda between sizes on the Ripley AF. If you're dead set on that bike, I'd probably lean towards sizing up, but a better option might be to hunt around for a bike that's more appropriately sized for you.

Toast is giving you good advice here.

Picking a bike that fits is independent of geometry and style (kinda of - read on.)

Fit starts with your seat relative to your pedals. Based on leg length, femur length etc. When on your seat your knees need to be in the correct position relative to your pedal spindles. Old method (and still a good home check) is to drop a plumbbob straight down from the little budge directly under your kneecap when the knee is bent and the pedal is in the forward 90 degree position. Plumb string should run very close to directly through the pedal axle in that position. Some folks like it to go even with the end of the crank. That's more of a spinning position. Through the spindle is a little more for power, slower pedaling (like in mtb), and you can go even further back but only for specific reasons and I would not recommend it.

After that, you figure out reach. Think of it as an arc - really low bars need to be closer to you than really high bars to exist on the same reach arc, and bar width impacts it as well. That arc really is a circle around your hip bones in a perfect world (though it gets screwed up when you go real low or real high - you aren't likely to do either.) At this point you can start thinking about bike type. Figure out your riding style, trails, and bike type. That will help figure out your bar width, height, etc. If your current bike feels super comfy, then use the distance from your hips to your bars as the goal to hit on your new bike. This is a 3D measurement - it includes the distance sideways to your grips.

Now you pick your suspension type/bike design. See what the different manufacturers are that make that style, and then see what the differences are in effective top tube length between those manufacturers. Pick the one that is most likely to get your reach right.

Most people do it backwards. Buy the bike (usually based on cool factor and/or color...sort've not joking), set the handlebar height and width, then adjust the saddle location till the reach is comfortable. That's super messed up, and only works on DH bikes where there is very little seated pedaling. If the amount of power you can generate matters to you, always, always, always set your saddle location first, then find a bike that works with your reach.

Make sense?

[Duffman]

There are lots of numbers that come together to make any given bike what is, some of which isn't visible in the published geo chart. We all have our personal bias but I think in general if you are a large you are large in how that company has decided to build their bikes. Sizing down or up can push a bike out of how it was conceived when in actuality you would probably be better served on a bike designed around different parameters. For sure this doesn't help if you truly are between sizes but it sure seems most people that are "between" sizes should be on the bigger bike but are hesitant.

I am sure I am opening a can of worms here but If you really think you know better than the bikes designer than why are you buying bike from them?

I don't disagree, but in this case 6'1 is the very top limit of the L and the very bottom limit of the XL on the Ibis chart. Truly between sizes.

Interestingly enough, based on some tips earlier in this thread , I started looking at similar short travel 29 trail bikes and was surprised how close the numbers are now. For example the Giant Trance 29 vs the Ripley AF , both in large. But the Giant size guide has the Large going up to 6'2 and I haven't heard as much chatter online about it fitting small .


Ibis Ripley AF
2021: Large

Giant Trance 29
2022: L

Reach 475 480
Stack 622 622
Top Tube (effective) 630 624
Seat Tube C-T 418 465
Head Angle 65.5 66.2
Seat Angle 76 77.0
Head Tube 115 120
Chainstay 432 437
Wheelbase 1217 1223
Standover 722 759
BB Drop 35
BB Height 335
BB Type BSA
Fork Rake / Offset 44 44
Trail 114 120

Looking at this at least to my confused eyes, they should fit quite similar with the Giant potentially having even a little less cockpit room, right?

[J. Barron DeJong]

When on your seat your knees need to be in the correct position relative to your pedal spindles. Old method (and still a good home check) is to drop a plumbbob straight down from the little budge directly under your kneecap when the knee is bent and the pedal is in the forward 90 degree position. Plumb string should run very close to directly through the pedal axle in that position.

I disagree with this. KOPS worked ok for old school road bike geometry, but even in road bikes the trend has been to a more forward saddle position as riders have tried to get into lower more aero positions. The new(er) short nose saddles are a part of this since there’s a rule about how far the nose of the saddle needs to be behind the BB.

With modern geometry MTB’s most people would need to slam the seat back on the rails to get their knee over pedal spindle, right? I mean, if it falls into place properly on a road bike with a 73 degree seat angle, you’re going to be forward of that position with a 76 (or 78) seat angle.

[toast2266]

Looking at this at least to my confused eyes, they should fit quite similar with the Giant potentially having even a little less cockpit room, right?

Yeah, just in terms of sizing, those two bikes look quite similar. I would say that none of the differences are large enough to really matter. Especially because there's a little bit of bullshitty-ness with any stated geometry numbers, so take them all with a little bit of a grain of salt.

[XXX-er]

But then we might have to stop wanking about endlessly online and do work

The difference in yeti cockpit L vs M was quite noticable, but i wouldn't have known without the B2B compro

especialy coming from a 14 yr old bike

[J. Barron DeJong]

I don't disagree, but in this case 6'1 is the very top limit of the L and the very bottom limit of the XL on the Ibis chart. Truly between sizes.

Interestingly enough, based on some tips earlier in this thread , I started looking at similar short travel 29 trail bikes and was surprised how close the numbers are now. For example the Giant Trance 29 vs the Ripley AF , both in large. But the Giant size guide has the Large going up to 6'2 and I haven't heard as much chatter online about it fitting small .


Ibis Ripley AF
2021: Large

Giant Trance 29
2022: L

Reach 475 480
Stack 622 622
Top Tube (effective) 630 624
Seat Tube C-T 418 465
Head Angle 65.5 66.2
Seat Angle 76 77.0
Head Tube 115 120
Chainstay 432 437
Wheelbase 1217 1223
Standover 722 759
BB Drop 35
BB Height 335
BB Type BSA
Fork Rake / Offset 44 44
Trail 114 120

Looking at this at least to my confused eyes, they should fit quite similar with the Giant potentially having even a little less cockpit room, right?

Giant lists the reach on a large 2022 Trance as 486 mm on their website?

Also don’t see a sizing chart on the Giant site.

[justo8484]

Duffman, I ride wiss weekly most of the year and just got on a size large transition scout. I'm 6'1", 34" inseam, and coming off a size large 2015 yeti sb5c. The effective top tube on the scout is actually 5mm shorter than the yeti was, but the bike feels worlds more stable on the downs than the yeti ever did. Probably mostly due to the longer reach and slacker head angle. I, like you, fell squarely in between the L and XL, and felt that going XL would be more fun for when I get up to blue for DH laps, or up to new england or down to VA/WV for some longer rockier descents, but I'm very happy with the L for the home trails. The more modern geometry absolutely makes the downs we do have more stable and fun, and I think not having gone for the XL keeps things manageable for the chunky, techy climbs and twisty logover hell of belmont.

Also, Duffman and VTskibum, do we know each other? I feel like there's at least a small chance we've ridden together; the philly mtb scene isn't thaaaat big. Do you do any of the regularly scheduled wiss group rides?

[EWG]

I disagree with this. KOPS worked ok for old school road bike geometry, but even in road bikes the trend has been to a more forward saddle position as riders have tried to get into lower more aero positions. The new(er) short nose saddles are a part of this since there’s a rule about how far the nose of the saddle needs to be behind the BB.

With modern geometry MTB’s most people would need to slam the seat back on the rails to get their knee over pedal spindle, right? I mean, if it falls into place properly on a road bike with a 73 degree seat angle, you’re going to be forward of that position with a 76 (or 78) seat angle.

This is a fair point. That said, we are venturing into mtbr territory here.

Most studies over the last handful of years have equated a more forward saddle position with increased efficiency, which furthers your point. Here's a good one: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5786204/
Though some of that is trying to get aero, which doesn't apply here.

Remember that saddle position is somewhat independent of seat angle - to a point. You can slide the seat forward and back as needed. But seat angles increased on mtn bikes for reasons not necessarily related to leg position - mostly as a response to wheelbase getting longer and still having rider reach work. One other note - early mtn bikes had super shallow seatposts. Getting steeper was very necessary. But published steepness doesn't equal real world steepness, as your rear shock sag will make your seattube shallower - up to 3 degrees for a long travel. So your "supersteep" 78 degree seattube is actually working like a 75. Going uphill also creates an effectively shallower seattube.

Long story short - I buy what you are saying to a point. Having your knee a bit ahead of your spindle makes sense. But I don't think it will be wildly forward.

Regardless, your decision on this doesn't change the basic advice: Whichever saddle position you choose relative to your feet, set it first, then size your bike so the cockpit fits - not the other way around.

[VTskibum]

Duffman, I ride wiss weekly most of the year and just got on a size large transition scout. I'm 6'1", 34" inseam, and coming off a size large 2015 yeti sb5c. The effective top tube on the scout is actually 5mm shorter than the yeti was, but the bike feels worlds more stable on the downs than the yeti ever did. Probably mostly due to the longer reach and slacker head angle. I, like you, fell squarely in between the L and XL, and felt that going XL would be more fun for when I get up to blue for DH laps, or up to new england or down to VA/WV for some longer rockier descents, but I'm very happy with the L for the home trails. The more modern geometry absolutely makes the downs we do have more stable and fun, and I think not having gone for the XL keeps things manageable for the chunky, techy climbs and twisty logover hell of belmont.

Also, Duffman and VTskibum, do we know each other? I feel like there's at least a small chance we've ridden together; the philly mtb scene isn't thaaaat big. Do you do any of the regularly scheduled wiss group rides?

It's possible, but I live in Downingtown right next to Marsh Creek, so don't get to the Wiss too often. Depending your riding crew, I imagine we could pretty easily connect some dots on acquaintances. Especially true if your crew raced MASS Cat 1 XC in the last decade.

Glad I'm not the only one touting slightly smaller frames around here. 5'11" and I go between Medium and (mostly) Large depending on bike and brand.