When did stack & reach become a thing?

[EB]

Originally Posted by Mark McM

There is one class of bike that often does have out-of-whack seat tube angles - 700c bikes in very small sizes. It's fairly obvious that smaller people need smaller bikes, with a shorter reach. But wheel size limits how short the reach can be before there is too much toe overlap Sure, a certain amount of toe overlap can be tolerated, but there is actually a CPCS regulation on how close the wheel can be to the pedals, so there is a regulatory limit on how short the front center can be.

Modern mountain bikes, especially full suspension ones, also have very steep effective seat tube angles - ranging from 75 up to 78. There are a bunch of reasons for this we don’t need to debate here (please), but one side-effect of this trend has been to make frame reach useless to compare frame fit, as the steep seat angles vary considerably amongst brands and models, and different suspension designs and travel amounts call for different amounts of steepness. I’ve fallen back to using ETT and seat tube length (to make sure I can fit the right dropper).

Fortunately, fit matters a little less with mountain bikes, and riders often size up or down depending on riding style rather than trying to recreate a certain static pedaling position.

[54ny77]

Funny you mention that. Couple years ago I bought a new mtb, and relied 100% on the expertise of the shop to put me on the right size. I hadn't the slightest idea what's what.

Originally Posted by Eli Bingham

Modern mountain bikes, especially full suspension ones, also have very steep effective seat tube angles - ranging from 75 up to 78. There are a bunch of reasons for this we don’t need to debate here (please), but one side-effect of this trend has been to make frame reach useless to compare frame fit, as the steep seat angles vary considerably amongst brands and models, and different suspension designs and travel amounts call for different amounts of steepness. I’ve fallen back to using ETT and seat tube length (to make sure I can fit the right dropper).

Fortunately, fit matters a little less with mountain bikes, and riders often size up or down depending on riding style rather than trying to recreate a certain static pedaling position.

[Indy]

Looks like Rivendell threw in the towel and started listing Stack and Reach for their upcoming A.H.H frames.

https://www.rivbike.com/products/homer

For a long time they would only go by Pubic Bone Height, which made little sense for perople like me with longer legs and shorter torsos vs. the average.

[fogrider]

it seems like reach is just another part of the equation. if one rides a 58 tt with 100mm stem, could one go with a 56 tt with a 120mm stem? depending on the st angle, this would put the rider a more forward, but one could move the saddle back and go with a shorter stem.

[HenryA]

Originally Posted by fogrider

it seems like reach is just another part of the equation…. snipped a bunch.

Yes, and that’s the criticism of using it as a definitive measure — its only part of the answer. And its not the logical starting point unless you’re in the bike business and want buyers to have a simplified method to make buying decisions. S, M, L sizing is a huge boon to manufacturers, distributors and dealers.

Using the full measure of a bike’s geometry gets a little complicated. And it might be that for comparing bikes with very similar BB placements and seat tube angles that S/R works. Move away from that scenario and S/R become meaningless pretty quick.

S/R is a short answer to an incomplete question. A rule of thumb, not an absolute.

[marciero]

Originally Posted by David Kirk

One thing I’ve not seen mentioned in this thread is how much headset type affects this...
If headset isn’t factored in it can lead to frustration...
dave

With that in mind, having stack, reach, and STA is equivalent to having virtual ST, TT, and STA. They both give the same information up to adjustment. With the former, you have to adjust for headset, and consequently stack and reach, With the latter you need to adjust for tube thickness, ht extension, and headset, also affecting stack and reach. You could argue that it is less of an adjustment with the former vs the latter. But is having a smaller "error" term any advantage when you know the error in each case? But without STA, both are incomplete and if we are just ballparking, stack and reach does not have across the board advantage over virtual TT/ST. As has been noted, unless you are a fringe case you can adjust on both ends- setback as well as bar height and extension. On the other hand, if we assume 73 STA, both are equivalent-that is, they give the same information - up to the above adjustments. So no advantage to either.

One big disadvantage for tagging size with stack and reach is that they are not easy to measure quickly. By contrast, with just a tape measure, you could get a much closer estimate of virtual TT and ST by eyeballing the horizontal.

[ripvanrando]

Cervelo kept STA at 73 degrees and kept a fixed chain stay length, I bet that really increases complexity and cost of the molds.

I hope my next bike is a Pinarello Dogma f12 with 72 degree STA.

[soulspinner]

Originally Posted by jimmy-moots

Yeah stack and reach was a construct created by a bloke on Slow Twitch many moons ago. Cervelo were an early adopter and it seems to have caught on more broadly early 2010's.

You can basically take stack and reach as a good guide for whether a frame will fit - the only thing you need to take into account is the seat tube angle and whether or not you can get your saddle in the right position with respect to the bottom bracket.

With frames of 'comparable size', STA's tend to be within a range that allows you to adjust... but if you're slammed on the rails one way or another then it comes into focus.

The other point that has been noted is that as you increase stack, reach decreases. So if you have a frame that has the right reach but not enough stack and you plan to add spacers to increase the stack, then reach will need to be corrected for with a longer stem. Usually no big deal, but if you are already running a long stem then it may be a concern.

But yeah. As a rule of thumb. Very handy. Allows you to quickly ascertain if something might be a good fit, then you can drill down into the specifics.

As an example, my preferred Colnago size is 52s, which has comparable reach to a 50s and 54s (the three sizes are within a few mm). The 50s needs spacers, a longer stem and I go back on the saddle rails. And a 54s is possible, on paper, but I would need a straight post and likely be quite forward on the saddle rails.

Cervelo keeps seat tube same all sizes which makes stack/reach easier to compare sizes.

[ripvanrando]

Originally Posted by soulspinner

Cervelo keeps seat tube same all sizes which makes stack/reach easier to compare sizes.

Alternative theory. They do not need separate molds for the back half of the frame.

[soulspinner]

Not sure thats the intent but it makes calculating easier than if every seat tube angle was different.

[ripvanrando]

Originally Posted by soulspinner

Not sure thats the intent but it makes calculating easier than if every seat tube angle was different.

That is true. Prolly need trigonometery for that.

I listened to a guru fitter and bought a Cervelo, it never fit. I listened to Zinn and got a custom, it never really fit due to STA

[Dave]

If I'm looking for a new frame, I look at stack first since I know that I want 510-530mm for a road bike with around 10cm of saddle to bar drop. If was looking for an endurance/gravel frame I might want 2cm more stack and that's generally how they're made.

After that, I look for a reach in the 370-380 range. It's rare when a frame that's my size has something other than a 74-75 degree STA. I try to avoid a 75, but I could use it with a 32mm setback post.

Don't overlook stem angle as a means of getting the desired bar height. I usually use a -17, but a -6 will raise the bars about 2cm.

Most brands have a size that will fit me, unless they have a proprietary seat post with inadequate setback. That can be a deal killer.

I just looked up a Specialized Atheos. It took all of 2 minutes to figure out that the size 52 would fit me perfectly.

[mhespenheide]

I had a 2011 Cervelo R3 and it fit and rode great. If it fit tires larger than 25mm, I'd still have it today.

[benb]

Originally Posted by Eli Bingham

Modern mountain bikes, especially full suspension ones, also have very steep effective seat tube angles - ranging from 75 up to 78. There are a bunch of reasons for this we don’t need to debate here (please), but one side-effect of this trend has been to make frame reach useless to compare frame fit, as the steep seat angles vary considerably amongst brands and models, and different suspension designs and travel amounts call for different amounts of steepness. I’ve fallen back to using ETT and seat tube length (to make sure I can fit the right dropper).

Fortunately, fit matters a little less with mountain bikes, and riders often size up or down depending on riding style rather than trying to recreate a certain static pedaling position.

Do riders end up with setback seatposts now on MTBs?

I'm going to find out for sure, but I 100% could not ride a MTB with a STA that steep without a ton of setback on the post if I have to pedal the bike, which I very much want to be able to do.

Looking at some MTBs I'm interested in they're listing a STA and an Effective STA. The Effective STA is what is super steep around 75, so it sounds like they are playing some frame tricks to bring the rear wheel in while allowing the rider to still have enough setback.

I need my saddle 8-9cm back, a real 75 degree STA I would likely need a 3+ cm setback on the post, and I'd wonder if that would completely defeat the point of engineering the frame with such a steep STA.

[benb]

FWIW I pulled my 2007 Serotta build sheet.

It did not have stack and reach the way we define it today.

But they were calculating stack and reach to the center of the handlebar with the headset + spacers + target stem, but not calling it stack and reach.

More interestingly I got a Seven build sheet in late 2015 but then did not go through with the purchase. Seven was not listing stack and reach in 2015. Their measurements were quite confusing. Though I think the frame would have been a great fit if I'd gone through with it.

I think there's still a lot that could be done if the manufacturers standardized some sort of frame data and all these calculations could be done on an app at the bike shop and the app could calculate differences between bikes and what stem + spacers could hit target fits.

Obviously fit guys can do this, but it'd be nicer if the consumers had access to the data easily without having to learn all the math, cause certainly some shops use this as part of a sales pitch in an unfriendly way.