I have seen every saddle set back methodology that exists, and if the "optimal" set back is a 2-3mm range, then it is very sad for the all the people who didn't get fit with the correct set back method. Because they vary a lot more than 2-3mm between them.


Which method is correct? I can tell you with some certainty it is not KOPS.


I can only conclude that the authors of those articles were really selling their method.


As far as the OP goes, I assume he is setting up another bike by fit numbers and his stem gives a reach that is 5mm off the numbers. Which raises the question what to do if a 5mm increment stem is unavailable. And one of my several suggestions was to borrow a little bit of your set back, either positive or negative, to balance the increase or decrease in reach. Which seems like a much better bargain to me than maintaining a set back while being too far or too close in reach.

And the ideal set back should be tolerant within a few MMs because we don't sit in precisely the same place on the saddle every time.


The most useful way to look at racing bike set back is that it is the forward limit where you still have balance to not lean on your hands, but are as far forward you can be to get your back flat. Greater amounts of set back are commonly used, but require the bar to come up.

So if I find a hundred of them on Ebay, does that not count?

Provide a link. All I’m stating is when you look at the available stems to 3 of the largest mail order companies in the bike business, they don’t show stems in 5mm increments. Completely anecdotal but having built up bikes for 36 years and having purchased many, I’ve never seen one in anything but 10mm increments. If you’ve seen one that’s available as a new purchase, show us a link. I only saw one very short mt bike stem from somebody in 35.

See, that's funny because Performance used to sell their Forte Pro stems in 5mm increments. I have a 95 and a 105.

Here's a page of just 125mm stems:
https://www.ebay.com/sch/i.html?_nkw...stem&_osacat=0

The point I was making is that if you really want a 5mm smaller stem, they exist. That doesn't mean they are common or expected. Everyone seems to treat 10mm as granular enough.

It seems that you disagree that the optimal saddle fore/aft position exists within a narrow range of 2-3 mm. Maybe "optimal" is not the word that perfectly captures what I am getting at. Let me try this another way. I submit that if you take one of the bikes you frequently ride and move the saddle either forward or backward by 2.5 mm (as you had proposed in response to the OP), you should be able to feel a difference in your pedal stroke during a ride. Do you disagree?

Okay, that's a different concept. Once you have adopted and adapted to a particular set back, you may or may not be sensitive to small changes.

I had a commuter bike that I built with a Cinelli 90mm stem, despite it being 10mm too short. So I pushed the saddle back 10cm. That worked fine, so I would not agree with the general statement - lots of riders have race bikes with standard set back and French Fit bikes for touring.

However, if you took one of my race bikes and moved the saddle 10mm forward - that would be a problem and I would be too far forward. 3mm? Probably not, but maybe. For all I know, my bikes already have that kind of variation, if I wasn't careful enough with the plumb line.


A real fitting luminary I worked for - Colin O'Brien - used the term "super adapters" for folks that are much less sensitive to changes in their fit. And then there were the opposite folks that even the smallest changes caused all sorts of problems. Maybe those are the people that would be screwed up by 2.5mm. But I don't think they are the majority. And when you make any fit changes you should do so thoughtfully and expect to balance it with something else. Like raising the stem slightly.



Back to the OP: So - when in doubt - move the saddle to the rear and go down in stem length.

I think saddle adjustments are very controversial because racers need the saddle right over the bottom bracket for maximum speed and a flat back for aerodynamics or something. I think there's even a UCI racing regulation preventing moving it farther up.

For normal people, moving the saddle back is often considered more comfortable. The Townie line of bikes advertises a flat foot, crank forward geometry, for example, that places the saddle way back so people don't have to lean or stand on tippy toes at stop lights.

Anyway, if you aren't a racer, there's plenty of adjustable stems out there. I have one of these which features continual adjustment, for example:
https://www.amazon.com/dp/B0CB2XR2MZ

Probably double the weight of a racing stem, but sure makes my commute comfortable.

It's aimed at the persons that focus on the numbers. Not so much the fit method itself. Generally not the fitter, but the one being fitted. I wonder what questions we'd get if those numbers were given in hundredths of a millimeter.

Perhaps ten mm is too much. But is 5mm close enough? I don't know. I've gone back and forth between a 100mm stem and a 70mm stem several times in the last 5 years and can't say that one is better than the other. Just that perhaps I should get a 50mm stem and a 120mm stem and see if either of those is significantly better or like the other two isn't really much difference. Though other things do change in the way I keep my posture when I change stems. And stem/bar height too. But neither is more or less comfortable.

Sometimes I shift my butt back into my saddle when I really want to dig in.

Not necessarily

In what regards is the reach too long? Reach to the hoods, on the tops, on the drops? Or all of the above?

Cheapest fix is just rotate the bars slightly upwards/inwards or do the same with the shifters. You also could look for a bar with less of a reach or drop, if you reach to the tops is fine

I just swapped out a 79mm reach bar for a 72mm bar. It would have been cheaper to go down 10mm in stem length, but IMO that changes the handling too much and could have made overall riding too cramped.

To the OP.
If I felt 5mm was a significant change, I would want to define 'Why' I thought I needed it to be 5mm shorter (or longer}.
I have a bunch of bikes, of different types and uses - that are all 'road' designated. They also, in many cases have different realized 'reach' and 'Stack'.
They're all comfortable... depending on their use. And then there are those which have the same 'intended use'.
Those would be very close/similar in position setup, regardless of the frame Dims.
I don;t think I'd be troubled by a 5mm difference in reach. A difference of 15 mm or more, would start to be noticeable, for me.
The only positional thing which seems very noticeable and affecting, for me, is saddle setback and extension...

Is this a rhetorical question for you? Or do you have some real issue where a 5mm diff. in reach would be a critical adjustment?

Ride On
Yuri

EDIT: If you have an idea that 5mm will make a difference, then go ahead and try it. Nothing like experimenting to gain some insight.

Handling comes from the total lever arm, which is the stem + handlebar reach. The stem itself doesn't dictate handling.

schmaybe

wrong, a longer stem would have more weight over the front wheel thus giving you the characteristics of being more stable and predictable. Also a longer stem simply provides more leverage. Yes you can combine the effective reach with the reach of the handlebar but again most handlebars are in 10mm increments while bar reach differs anywhere from 2mm-10mm bar to bar, thus you can make more precise incremental reach adjustments

aren't you a bike fitter? shouldn't you know this?

No, the statement was correct. Combined stem length plus handlebar reach is what matters.

Now your are now confusing bar reach with bar width. Your example was a long reach bar with a short stem vs a short reach bar with a long stem. As long as the hoods end up in the same place, there is no difference in leverage or loading.

Yes, I am a fitter and I absolutely understand this.

When I used "optimal" I did not suggest that the optimal saddle fore/aft position is a constant that is set in stone forever. I meant optimal for a given rider with his/her then current physique for a particular bike. (Physique encompassing fitness, musculature, flexibility, etc.)

Thus, if one shifts the saddle position by a few mm, how one's muscles are used throughout the pedal stroke is slightly different -- do you agree with this? --- which may affect one's comfort and/or power output.

After one gets used to the new position (i.e., one's muscles have adapted to the new position), if comfort and/or power output is improved, then the new position is more "optimal" than the former.

Well, that's the theory. But then you go from your road bike to your gravel bike to your MTB and you are able to ride all those different positions just fine. Because set back doesn't not remain the same when you bar heights are different.

People naturally slide forward in their saddles when they pushing hardest. Is that optimal?

fwiw if you buy a 3t 6 degree stem, it is measured in the positive position. If you flip it so it is -6 degrees like most of us will it adds 5mm to the reach if you actually measure the stem. Deda, Thomson, pro, enve all measure accurately. Some other companies might drift 1-3mm from their stated lengths, but the big differences only really appear in 130 and 140mm lengths.

I always thought stems were measured from the side, from the middle of the clamp hole to the middle of the opposite end's clamp hole.

eg. something like this

You are correct. Measuring them from the top is incorrect and will give you two different number +/- the real number.

What varies is the horizontal reach when you flip the stem. And that happens because the steerer is angled back.

old thread, but for people like me with short reach I would say no. One stems are usually sold in 10mm increments, thus a shorter stem would be then 5mm too short? There are other ways to adjust effective reach on the bike other than the stem, since a shorter stem will effect handling in a more twitchy feel. You can tilt your bars slightly up, you can tilt your shifters slightly up, you can flip stem for a positive rise or buy a stem with a positive rise. You can also buy new bars that have a shorter reach to them. My Cannondale SuperSix EVO had a similar issue of the reach to the shifter was just a touch long. I changed the bars from a 80mm reach to 72mm reach and went down to a narrower bar width 35cm to 33cm and the fit is spot on now.

For me a 5mm difference sure is noticeable. Several decades back when I was in my late 30's the body started telling me I need to make an adjustment. Tried different length stems and between 2 stems of different lengths of 10mm difference one was too long and another felt a little too short. Bought one 5mm in-between the two and it was like magic. There used to be more stems available in 5mm length increments but not too many now. Been using the same seat to bar measurement ever since and can tell when it's not the same. That's just me though so not the same for everyone.

There are so many quality stems now at good prices. I was researching a 70 mm stem to replace the 80 on my bike, when I came across the Kalloy Uno Stealth stem. It weighs about 90-100 grams for a 70 mm, and you can get one for $50 or less. I know some associate Kalloy with "cheap", but my experience with Kalloy products has been good. So, for a few bucks you can try out a shorter stem with no real regrets if it doesn't work out.

I only ride with 130mm stems whether on MTB and Ropad bikes, so this stem lenght has to be respected .