When did stack & reach become a thing?

[Dave]

With MTBs. I don't understand the real STA being around 66 and the effective STA more like 76 degrees. I'll never ride one, but I'm curious.

[RoosterCogset]

Originally Posted by 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.

You can play with a site such as this one, showing native frame stack/reach, as well as with spacers and/or stem.
http://www.bikegeo.net/

[Mark McM]

Originally Posted by Dave

With MTBs. I don't understand the real STA being around 66 and the effective STA more like 76 degrees. I'll never ride one, but I'm curious.

This happens on road bikes as well. It can happen when either: The seat tube is curved (in which case the seat post extends at a different angle than the angle from the seat cluster to the BB); or the seat tube is straight, but it isn't aligned with the center of the BB (so the seatpost is forward or rearward of where it would be if the seat tube was was aligned with the BB.

In both cases the "effective seat tube angle" is the angle of the straight line from the top of the seat post to the BB, when the saddle is raised to a traditional height for that size frame.

[jimoots]

Originally Posted by 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.

You can calculate stack / reach to the stem (inc spacers, headset, etc) with bikegeo.net

You do need basic geometry measurements that are typically available.

[benb]

I made a spreadsheet to calculate my fit onto new frames about 5-6 years ago.

As long as I get the STA and the stack/reach I can get a real quick indicator. I can't calculate weight distribution and center of gravity or something, that would be really cool to work on actually!

But there's a big difference between me having something I use myself and the bike industry making it easy and transparent (and robust) for all shoppers at the point of sale.

Most shops still treat this stuff as smoke and mirrors old world magic.

[9tubes]

When I retire I'm going to open a pub in rural England named The Stack & Reach.

[soulspinner]

Originally Posted by 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.

Its the drop at 65yo with a crappy back that keeps my drop in the 6cm range. Do you work on your flexibility?

[soulspinner]

Originally Posted by 9tubes

When I retire I'm going to open a pub in rural England named The Stack & Reach.

Beers on a handelbar the perfect stack and reach of you bikes!

[weisan]

Regardless of how they came about, the challenge to debunk myths and help consumer come up with an easy to understand and quickly figure out fit and sizing remains a worthy goal.

[Dave]

Regarding the effective STA - I realized that the cervelo R3 frame that I bought when they first came out many years ago had a seat tube that was moved forward and the 73 degrees was not the actual angle, but was supposed to position the saddle like a 73. I rode that bike twice, tore it down and sold the frame. Going down my regular mountain descent it felt unstable. Back to my LOOK and Colnago frames.

The steep effective STA on mountain bikes does seem odd. My knee is typically about 2cm behind KOP. I could duplicate that with my 32mm setback post, but the saddle would be back a long way on it.

[tommyrod74]

Originally Posted by Dave

The steep effective STA on mountain bikes does seem odd. My knee is typically about 2cm behind KOP. I could duplicate that with my 32mm setback post, but the saddle would be back a long way on it.

It helps to understand that a modern geometry MTB set up to duplicate your road fit would result in a horrible ride. Slack HTA + long reach + short stem = the need for a more forward weight distribution to weight the front tire in corners and on climbs.

The upside is that steep climbs, downhill handling, and all cornering are tremendously improved over old-school MTB geometry. The downside is that the tradeoff between pedaling on flatter terrain and overall handling ability (which was formerly skewed drastically toward pedaling) is now skewed in favor of handling.

Set up a newer bike with you weight that far aft and you'll understeer through every turn.

[NHAero]

I don't understand this yet and maybe you could elaborate. Doesn't a slack HTA plus a short stem both combine to push the front wheel out farther from the person's center of mass, thereby moving front/rear weight distribution to the rear? Which I expect helps on fast descents but not on steep climbs.

Originally Posted by tommyrod74

It helps to understand that a modern geometry MTB set up to duplicate your road fit would result in a horrible ride. Slack HTA + long reach + short stem = the need for a more forward weight distribution to weight the front tire in corners and on climbs.

The upside is that steep climbs, downhill handling, and all cornering are tremendously improved over old-school MTB geometry. The downside is that the tradeoff between pedaling on flatter terrain and overall handling ability (which was formerly skewed drastically toward pedaling) is now skewed in favor of handling.

Set up a newer bike with you weight that far aft and you'll understeer through every turn.

[weiwentg]

Originally Posted by Mark McM

...

In both cases the "effective seat tube angle" is the angle of the straight line from the top of the seat post to the BB, when the saddle is raised to a traditional height for that size frame.

...

You know one drop bar manufacturer that uses effective STA completely differently? Open. They state an STA of 72.5 degrees in all sizes, but a "normalized" STA of 74 degrees for small (in the Open UP), declining to 73.5 for other sizes. Their note says

Normalized dimensions to compare to frames with standard seattube instead of our zero-setback seattube design.

Which confused me at first as I've never seen anyone else do this. In any case, I need at least a 74 degree real STA with a zero setback post to achieve my desired fore-aft position, so Open is totally ruled out for me.

[marciero]

Originally Posted by benb

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.

That we have stack and reach at all is evidence that the movement in the industry has been in the other direction-toward simplification and rough estimates rather than greater precision. The level of precision you get when considering a complete set of dimensions that uniquely locate contact points is not meaningful unless you have your fit dialed to the same precision, and that excludes a large portion of the consumer market.

[Mark McM]

Originally Posted by NHAero

I don't understand this yet and maybe you could elaborate. Doesn't a slack HTA plus a short stem both combine to push the front wheel out farther from the person's center of mass, thereby moving front/rear weight distribution to the rear? Which I expect helps on fast descents but not on steep climbs.

I think the idea is that long top tubes and shallow head angles improves handling on steep descents, but require that the rider's weight be far forward for climbing. Climbing is best done seated, so the seat tube angle is steep to keep the rider's weight forward when in the saddle. Steep descents are done out of the saddle, with the rider's weight moved back. Dropper posts get the saddle out of the way, so the rider may more easily move their weight back when out of the saddle.