Short top-tube, compensate with extra long stem?

The weight distribution is what matters. Stem length and/or saddle position can not fix the wrong frame size. \n \nI do not even look at TT length. I know where I want my hands to be in relation to the front axle, and about what front-center is required to achieve that position. Stem length is then what it needs to be. \nWhen designing a new frame I tend to use a 120mm stem as the norm. To go shorter requires a steeper HTA and/or less fork offset. \n \nIf my hands are too far forward the front tends to tuck-in in corners, especially slow tight turns or on loose surfaces. \nToo far back and the front floats, lacking grip. Hard to turn and wants to continue straight.

Shiggy!  Wow, thanks for responding.  If anyone should know it's the person who designed the best dirt drops available!

Side note, why are mountain bike stems (for flat bars) getting shorter and shorter as frame geo changes?  I don't have a flat bar bike currently, just curious.

Erik_A wrote:Shiggy!  Wow, thanks for responding.  If anyone should know it's the person who designed the best dirt drops available!

Side note, why are mountain bike stems (for flat bars) getting shorter and shorter as frame geo changes?  I don't have a flat bar bike currently, just curious.

\nAll about fashion. The long front-stubby stem setup is fine if you are riding straight down 30%+ slopes and do not really need to turn. "Nimble", "agile" and "responsive" do not apply to many mtbs any more. Even the "best" of today's trail bikes would have been described as sluggish, floppy, and clumsy 15 years ago. You have super slack HTAs, high trail, choppered out bikes with no weight on the front wheel -- unless you are on those steep descents and/or use extreme body english. (Remember when "aggressive" meant steep and short and "relaxed" was long and slack?) \n \nRecently I have read reviews of a couple of bikes with "old school" geometry (and still stacker and longer than I prefer). First comments are usually like "you can actually steer the bike easily", "surprisingly good on the descents", and "climbs very well and holds its line". \n \nThen they say it would be better with slacker angles, which would ruin all the above that they liked. \n \nSimilar things have happened with road bike geometry, but in the other way. \nFor my personal preferences, most current road/'cross bikes are too short in the front, and most mtbs are too long. \nLast summer I test rode a XL Niner RLT. The reach to the bars was 4-inches shorter than my dropbar MTB (custom frame by me). The reach on my custom road/Rando/gravel bike is another 2" longer. I could ride stock frames 15-20 years ago, usually 58cm road and medium MTB.

Shiggy- Thanks again! Would you be willing to share your current bike frame(s) geometry?

I really do not even know the geo in "standard" chart terms. \n \nI simply set my "fit" points relative to the BB (saddle set back, reach to the bars, reach to front axle, saddle height, bar height), connect the dots and the TT, STA, HTA are the result of the fit. Not the other way round.

this is still a good topic. on a conventional road (paved or otherwise) bike with a drop bar and a 70-72° HTA, how long or short can a stem be before it starts to compromise handling?

if I am between sizes on a frame and I can make the larger size fit with a 80mm downward-pointing stem, or a 100mm stem pointed upward to create the same relative contact points, should I get the bigger or smaller frame?

[QUOTE username=mack_turtle userid=4470674 postid=1317581345]before it starts to compromise handling?
/QUOTE] What is your definition of ideal handling and what changes to it would you feel compromised?

BTW, handling will be dictated by trail (based on head angle and fork offset), while your stem and bar width will impact the feel of your input into that steering response.  The other question is wheelbase - some bikes offset head angles to make wheelbase similar across sizes, while other don't keeping the same head angle and fork offset.  

80 or 100mm stems are fine IMO (I run 90mm), are you looking for a more stable ride, or slightly more responsive ride?  And again examine the trail/headangle first before assuming shorter stem is more responsive.

Also another consideration is seat tube length - tall ones if you want to race cyclocross, short ones if you want to run a dropper post.

For me, I am not weaving between peloton traffic on the road and often take my gravel bike offroad on singletrack and some steepish descents, so I prefer a more stable handling bike.

A set back seat post 30~40mm and a slightly longer stem should keep too much of your weight distribution off the front end.

mack_turtle wrote:this is still a good topic. on a conventional road (paved or otherwise) bike with a drop bar and a 70-72° HTA, how long or short can a stem be before it starts to compromise handling?

if I am between sizes on a frame and I can make the larger size fit with a 80mm downward-pointing stem, or a 100mm stem pointed upward to create the same relative contact points, should I get the bigger or smaller frame?

It’s still about weight distribution. A longer stem does give a “tiller” effect, but for me it is all about where my hands are relative to the front axle. 

I'm sure there's no shortcut to figuring out what is the optimal position for my hands relative to my front axle, but is there any way to describe it so I know what I'm looking for?

Here are some relevant numbers:

• I have owned a Salsa Vaya. the long wheelbase made a handle like a school but, but it was comfy! I never road it loaded down for very long miles—which is the intension of such a bike. I wanted something more lively. sold it to buy the following:
• 52cm Soma Double Cross Disc. helluva a bike, but I recall a lot of toe overlap with 35mm CX tires. not sure if I should worry about that anymore as it's only a problem with riding technical singletrack where the bike really doesn't belong. I had to use a tall spacer stack to get the handlebar high enough which was ugly but it worked. I had a good amount of exposed seatpost. i should have gotten the 54cm DCD. sold it to pay for some upgrades my MTB needed.
• Traitor Crusade. I really like how this bike fits and handles. wish it had a taller head tube so I could use fewer spacers but that's mostly an aesthetic issue. I am replacing it so I can get something to bigger tires, hence the Rando.

Note: the Rando will have an eccentric BB, so the BB drop, reach, and stack can change by up to 7mm when I am done with it. because of the way the Wheels MFG PF30 EBB is designed, the crank spindle will have to be higher than 75mm. I'll most likely try to point the EBB back to shorten the rear-center but the position will depend on what gear combo I use (singlespeed). that means the stack will be less, the front-center a tiny bit longer, and the reach will increase.

mack_turtle wrote:I'm sure there's no shortcut to figuring out what is the optimal position for my hands relative to my front axle, but is there any way to describe it so I know what I'm looking for?

Short cut:
when riding, look down at your front axle.  You should not be able to see it because the handle bars are in the way.  If you can see your front axle, adjust your stem length accordingly.

mack_turtle wrote:this is still a good topic. on a conventional road (paved or otherwise) bike with a drop bar and a 70-72° HTA, how long or short can a stem be before it starts to compromise handling?

if I am between sizes on a frame and I can make the larger size fit with a 80mm downward-pointing stem, or a 100mm stem pointed upward to create the same relative contact points, should I get the bigger or smaller frame?

.

Generally speaking, you can change a stem by 10 or 20mm without affecting the steering response much.  by 40mm, its going to be really obvious that the bike handles differently.

If you want to know what a shorter stem feels like, move your hands to the midpoint between the stem and the drops.  Moving your hands closer to the stem has a similar affect to the steering response as does using a shorter stem.   
FYI - notice that on mountain bikes stems (that used to be 120mm) are now super short, but at the same time the width of the handlebars as grown just as dramatically?

A short top tube may also mean a relatively short front center, if toe overlap is a concern.

Here's another builder's thoughts on the move toward long top tubes/short stems.
https://www.44bikes.com/huntsman-supertrail-prototype/

chas wrote:

Short cut:
when riding, look down at your front axle.  You should not be able to see it because the handle bars are in the way.  If you can see your front axle, adjust your stem length accordingly.

That was such a ridiculous method for sizing. Right up there with using only stand over for frame size.
Never talks about how you grip the bar. No consideration of the bar reach. I can “move” the bar ahead or behind the axle simply by bending my elbows, or arching and stretching my back.

mack_turtle wrote:I'm sure there's no shortcut to figuring out what is the optimal position for my hands relative to my front axle, but is there any way to describe it so I know what I'm looking for?

It took me 25 years to figure out how to quantify the weight distribution that works for me, and that was more than 15 years ago. Then it is complicated by total reach differences I prefer for road, unpaved, and mtb. 

indeed, I think the "hide the hub" thing sounds like kooky folk wisdom in the vein of moving your saddle to accommodate KOPS. it's basically nonsense but it sounds objective. perhaps this is a good example of the McNamara Fallacy.

I am interested in this now because I'm replacing a CX frame with something that has more tire clearance. Namely, I have a Traitor Crusade and I'm looking at a Van Dessel WTF. (meets my criteria of being easily single-speedable and room for big tires with a non-boutique price tag.)

I'm 5'9" with tight hamstrings, so I need the bar close to level with the saddle, just a bit below, and not too far away. The reach and ETT on the medium WTF is quite a bit longer than what I am used to and I think I'll need something shorter than a 80mm stem to make it fit. traditionalists will say that the stem is too short, which means the bike just doesn't fit me, but the fork with a 50mm tire has a high trail value, which might be just fine for a short stem. I expect this bike to handle closer to a mountain bike than a road bike, but that still leaves me with a lot of questions. it's impossible to actually ride any of the bikes I've considered buying recently, so I have to go off geometry charts and online reviews.

mack_turtle wrote:indeed, I think the "hide the hub" thing sounds like kooky folk wisdom in the vein of moving your saddle to accommodate KOPS. it's basically nonsense but it sounds objective. perhaps this is a good example of the McNamara Fallacy..

How do you adjust your position over the BB if you don’t move the saddle?
My position relative to the BB is the basis of every other fit/handling dimension of my bikes.

I move the saddle until I feel balanced and stable over the BB in riding position so I don't rely on loading my arms with body weight. That may or may not line up with KOPS. it's subjective and takes trail and error.