mike09

I am 5’10” with a pant inseam of 30”. I have shorter legs and a longer torso. I am looking at the Sirrus hybrid bike but am unsure what size to get. If I go with my legs I think I’m a medium frame and if I got with my torso I’m a large. Is it more important to size to the seat tube (legs) or top tube (torso)? A medium will fit my legs better but my torso might feel crammed up, and if I go large my torso will fit better but my legs could be dangling off. Which is more important, what is more adjustable- leg or torso geometry, what size frame will suit me better?

Some bike shops won’t let me demo due to Covid so I need your help.

Thank you!!

woodcraft

IME, a lot of saddle setback is needed to balance the long torso,

so a long top tube is not needed & the smaller size is a better fit.

martianone

I too have short legs and long torso, 6'2" tall with a 30" inseam.
tried a number of bikes, none really fit well.
finally went with a Gunnar Roadie with custom geometry.
best investment I've ever made in a bike.

Litespud

in general, size for your legs, you can stretch the cockpit through a combination of longer stem and longer reach bars. I personally wouldn’t used saddle setback to achieve this. Seat height and setback should be reserved for optimizing pedal stroke - don’t mess with that for cockpit adjusting. If you can’t achieve a good-fitting cockpit without an unfeasibly long stem or a frame too tall for your legs, you might be looking at custom

mike09

What do you think about stand over height? Maybe that can help determine since I’m between sizes? Think I need to size down to a M.

Litespud

i don’t think about standover height at all, since IMO it’s the measurement least relevant to how the bike behaves when you’re actually riding it. That being said, no one wants to crunch their ‘nads on the top tube. If you can place both feet flat on the ground, that’s all you need. I still say size the frame for optimal pedal stroke. If that size precludes stand-over, then either a smaller frame or a more sloping top tube, or custom. My main road bike has a horizontal top tube that allows me to stand over flat-footed in my bike shoes with maybe 1-2” ‘nad clearance, which is plenty. The only time I stand like that is if I’m about to get off the bike or if I just got on. When I come to a stop on the road, I only ever unclip one foot, so standover height is seldom a factor

Koyote

No. Saddle setback is to position the knees properly over the pedal spindles, and someone with shorter legs (shorter femurs, actually) would actually need less setback, everything else equal.

mike09 , you likely should look at bikes that have relatively long top tubes (compared to the seat tubes) - and even then, you may need a long-ish stem. I also think you need a good shop, with a test ride and an experienced bike fitter. I don't know where you are, but plenty of shops are still doing this (as safely as possible) right now - I was at one such shop today.

AdkMtnMonster

Stop using your pants to size your bike, and get a real measurement. Google it. It’s so freakin easy. Good luck!

79pmooney

I'd love help with my funky body geometry but I find even the best fits only help me when I'm on the bike and that is only 5% of my waking hours in a good riding year. Now if I could get some of that funk into my music ...

Couldn't resist.

And seriously - my breakthrough was my first 180mm stem. That changed what I knew about bike fit. (My customs and the stock bikes I choose reflect that now so most have close to stock stems..)

Litespud

79pm - I always thought that super-long stems weren’t optimal because they slowed down rider input and shifted rider weight further to the front, with negative consequences for bike handling. What’s your take on that notion?

79pmooney

All true. But when your position is sacrificed and costing you 15% on available oxygen and power, that stuff is peanuts. (And super long stems ride fine, just different. No, not what I would want for a Cat 4-5 criterium. Likewise weight on the wheels. But having strength after 90 miles of hills more than makes up for both if you are not racing. My bikes now are chosen to use more normal stems. (Well all but my fix gear commuter which is typically the next frame I can find that works when I crash my last. Currently an old Trek 4something. It's got a 175. But then, its a fix gear with 175 cranks. Not doing criterium corners!)

So I use the long stems on stock bikes I buy for a purpose. The good bikes are either chosen carefully so they get stock stems or are built for me. My first TiCycles was designed around using a 120mm stem. Second one was patterned after a bike with a ride I loved. I run 130-140 on that depending on the handlebars. It also has nice quick steering geometry so it doesn't suffer at all with the longish stems. Real race handling .

woodcraft

My saddle nose is 8 cm behind the BB. Should I change it for proper knee position?

bruce19

My pants inseam is also 30" but my actual measured inseam is 32.5". I ride a "square" 55. That is 55 cm frame with 55 cm TT. FWIW I am 5'9" on a good day.

Koyote

You can start here. While there is some disagreement over the KOPS method, there is general agreement that saddle position is for positioning knees relative to the pedals/cranks, and top tube length and stem length are for adjusting reach. (That's a very basic starting point, grossly simplified.)

As for your own saddle position: if you are comfortable on the bike, can ride as long as you want without pain or discomfort, then it may be best to leave it alone!

c_m_shooter

Buy your bike based on the reach you need. Saddle height is easily adjusted and most bikes use sloping top tubes now. Moving the saddle excessively forward or back or using a stem much shorter or longer than the frame is designed for change the handling away from what the designers had intended.

woodcraft

Actually, I was just attempting to pull your chain. At risk of beating a dead horse, and for anyone who might be interested...

The measurement of KOPS will vary ~5cm just from toe up/down pedaling position, and riding up a 10% grade can change it 6cm- depending on foot length. Not to mention TT bikes and recumbents.

Why is knee over pedal "proper"? According to the article linked, it is so that the force of pedaling pushes the body up, and slightly back, reducing the need to use muscle and/or friction to hold the position. So it is the COG that will be pushed forward or back. For the same KOPS position, a rider upright on a cruiser bike with backswept bars will be pushed back (against a wide saddle), and the same rider in a low road position will be pushed forward onto the hands- especially one with a long torso.

So focusing on just the position of the lower legs in relation to the pedals makes no sense without fitting for the overall riding position, and cycling goals.

If you don't think that your COG changes with forward bend, try standing with heels against a wall, and attempt to touch the floor without falling.

My point to the OP was that as forward bend increases, the COG and thus the shoulders move back, partially offsetting the imagined need for an especially long top tube.

ArchEtech

I’m about your height and have very short legs. I’ve found smaller sizes that typically recommended are better since I need a shirt stand over height and then use a high seat position. The endurance CX Gravel geometry tend to fit me a bit better and the slightly more upright is better for my heavier upper body. Doesn’t mean all that will work for you, but it’s some options to look at.

Koyote

Yeah, this is why I linked to an article that considers alternatives to KOPS: it's not a hard and fast rule. In fact, my saddle position puts my position over an inch behind KOPS, but it's where I feel comfortable. A bike fitter once convinced me to move the saddle forward (with an appropriately longer stem), but my knees hated it.

79pmooney

All this theory on pushing the body forward or back using KOP? Wow! I keep it really simple. There is a best compromise for me that gets me aero enough to go upwind and has my thighs and torso open enough for good, full breathing, Being quite skinny, long limbed and not remotely powerful, that aero is very important, Those two things dictate where my seat needs to be. And where my shoulders end up. From there I take an easy swing forward with a small bend in my arms and that is where my handlebars want to be. And yes, I have real weight on my hands. I"m fussy about things like handlebars, handlebar rotation and height (which vary fairly often) and brake lever location. If I pay attention to those things (and ride regularly) I can spend all day on the bike with little problem. And if I have to spend a few hours going upwind, it's "thank you, thank you, thank you!"

I now keep an on-going CAD drawing of all my bikes, each bike overlaid on the same point at the center of the BB. Includes seat and handlebar positions. I bring a tape measure and take notes when looking at a prospective bike. Draw it up that night and compare. What seatpost do I need to get the seat right? Stem? How does the weight balance between the wheels look? Makes setting upu different bikes for different uses easy. A cruiser? I just rotate my whole position around the BB back a few degrees.