How did these Serotta Hors Categorie function

[cnighbor1]

How did these Serotta Hors Categorie function
I see these on eBay https://www.ebay.com/itm/Vintage-Ser...53.m1438.l2649

every once in a while and always wonder did they function better or worst that a similar Serotta
Thanks

[Dude]

I'm assuming David Kirk will chime in here, if not there is enough collective wisdom to answer the question. These stays were the brainchild of Kirk's when he worked at Serotta.

"better" and "worse" are in the eye of the beholder. They rode great. The curved ti seatstay acted as a spring/suspension. The rubber straps that ran on the inside of the stays were essentially a damper. The curved ti stays, without them, would be too flexy. Together they were great.

The bike handled very well, you could never feel the stays flexing, I think at most there was about 8mm of "travel." They did what suspension is supposed to do - keep your rear wheel stuck to the ground. The comfort/smoothness was an added benefit.

Many people didn't agree with the aesthetics of the the bike, but i've never heard of a bike, that doesn't look like a bike, that is praised for its new design (around here people complain if it's made of carbon fiber).

[pdonk]

From the patent abstract

"A bicycle frame uses an existing frame member--a seat stay--as a spring, and absorbs high frequency, low amplitude vibration with effective damping. The spring force constant can be adjusted for rider weight, riding style, road or terrain conditions, or the like, and the system is lightweight. Each seat stay is connected at a top end to the seat tube, and pivotally connected at the bottom end to the rear drop out, and has a circular arcuate curvature adjacent the bottom end with a radius of between about 11-16 inches and subtending an angle of between about 20-60 degrees. A damping/spring constant increasing element, comprising a metal strip bonded to elastomeric material (such as silicone) having a durometer between about 20-70 Shore A, is bolted to the seat stay convex arcuate portion, and can be replaced with a unit having a different durometer."

Link to full text

https://patents.google.com/patent/US...e+serotta+kirk

[stev0]

Have read many positive reviews about the hors categorie's ride qualities in the past, but would love to hear how DKS compares to modern versions like "FutureShock" on the Specialized Roubaix and the rear shock on the Pinarello K10. Definitely ahead of its time.

[Black Dog]

Dave Kirk may chime in here since he is the man behind the design. The DKS on the chainstay stands for David Kirk Suspension AFAIK.

[bambam]

I have one(from forumite). I have been down one particular hill around here many times. short 23% grade. on many different bikes. Typically hit speeds between 48-51 mph. Went down the same hill on my Hors and hit 55.

caveat: not sure I was using the same computer and the Hors is longer and lower that most my bikes with a 130 stem. (usually ride a 110-120).

All I know is it was like butter going down that hill and never felt out of control.

I know from rollerblading a softer wheel durometer can be faster than a harder one. i.e softer wheel on a rough surface will be smoother, not bouncing and loosing speed. This may be accomplished with lower tire pressure in a bike? but how often on a ride is the road smoothness consistent.
Bambam

[duff_duffy]

I owned one once...was told the rear was designed to keep the rear wheel on the ground when hitting rough spots, it was not designed to absorb shock - never quite made sense to me but it was a great riding bike.

[Mark McM]

Originally Posted by bambam

I have one(from forumite). I have been down one particular hill around here many times. short 23% grade. on many different bikes. Typically hit speeds between 48-51 mph. Went down the same hill on my Hors and hit 55.

Were you braking less with the Hors than the other bikes, or perhaps had a better (more aero position)? A 10% speed increase seems a bit much just by adding a little more flex in the rear. The force to overcome air resistance increases with the square of speed, and since the majority of the drag at 55 mph is air resistance, the air resistance would have gone up by nearly 20%. I don't think there's enough rolling resistance/suspension drag losses for a reduction in these to make up for the 20% difference.

For my own anecdote, there is one hill around here where my speed on the same bike has varied between 46 mph and 55 mph - but the big variable in these cases was wind (head wind vs. tail wind), which can vary quite a bit in that area.

I don't doubt that there could be some amount of speed improvement by adding some rear suspension, but on reasonably good pavement, 5 mph seems a bit much.

[campy man]

Kirk +1

Originally Posted by Dude

I'm assuming David Kirk will chime in here, if not there is enough collective wisdom to answer the question. These stays were the brainchild of Kirk's when he worked at Serotta.

"better" and "worse" are in the eye of the beholder. They rode great. The curved ti seatstay acted as a spring/suspension. The rubber straps that ran on the inside of the stays were essentially a damper. The curved ti stays, without them, would be too flexy. Together they were great.

The bike handled very well, you could never feel the stays flexing, I think at most there was about 8mm of "travel." They did what suspension is supposed to do - keep your rear wheel stuck to the ground. The comfort/smoothness was an added benefit.

Many people didn't agree with the aesthetics of the the bike, but i've never heard of a bike, that doesn't look like a bike, that is praised for its new design (around here people complain if it's made of carbon fiber).

[David Kirk]

The DKS is an interesting thing....even after all these years I still get a few emails a month asking about them.

They have developed a cult like following due to their ability to go downhill or around a less than perfectly paved corner faster than anything else. They really carve corners well.

The idea came to me after seeing curved seat stay bikes at Interbike and I wondered if they really did anything...and if they do something they must move. So I bought a few bikes and tested them and there was little to no movement under load. So while they looked like they might do something they actually did nothing. It was marketing BS and nothing more

I then set about trying to come up with a design that would allow for measurable and repeatable movement and this lead to the J shaped curve of the seat stay and the pivot at the dropout to allow the stay the freedom to move. This worked very well but under some circumstances it had a busy feeling. Not bouncy like a MTB on the road but it needed some additional control....it was a spring without a damper.

This lead to the silicone strap bolted on the outside of the stay curve. This allowed the stay to bed into the GE developed "super-damper" silicone and it really made the bike feel hunkered down and stuck to the floor. I kept tweaking the design until it would give 8-10 mm of wheel travel at the most. I ruined a few wheels testing the prototypes running them into a 2x4 bolted to the floor. It was brutal.

In the end I liked the design but I didn't feel I was fully done with it when a line was drawn in the sand and it was offered for sale. I worked on a revised version that took out weight and gave better still damping control but it never made it to market. The big problem was that no one understood how it worked and that included the sales staff so they never pushed them. The other bikes were easier to sell and looked so much more conventional.

I wish I still had one just to hang on the wall. They are a really fun and different ride and nothing will corner on bad pavement like an Hors with DKS. I'm proud of that.

dave

[weisan]

thank you dave pal. always learn something new from you.

my long-gone Hors...

[dddd]

10mm would seem to be about at the limit for this design, at least in terms of the brake pad having a surface to rub on.
This could be re-introduced as a longer-travel disc-braked frame, assuming that the materials of the seatstays could deliver that (and that it had a worthwhile marketing/performance metric about it).

I had doubted that using significant chainstay compression flex could adequately control rear wheel tilting, versus having a monostay compress, but it sounds like the bike's lateral rigidity about the rear wheel wasn't a problem in the real world.

I've ridden full-suspension road bikes and don't like the feel unless the spring rate is decidedly firm. Too much movement and then cornering clearance becomes an issue, and geometry changes and pitching motions compromise the feeling of control (assuming road geometry, short wheelbases work only with very limited travel).

[jamesdak]

I've always wanted one of these but they never come up in my size at a time I can afford one.

I wonder how the DKS compares to the current Terraplane Seat Stays.

[SPOKE]

Originally Posted by jamesdak

I've always wanted one of these but they never come up in my size at a time I can afford one.

I wonder how the DKS compares to the current Terraplane Seat Stays.

I have both...the DKS moves a bunch more. You can actually feel the rear of the bike compress while climbing a steep hill in a pretty low gear....kinda a slight “bobbing” action. Not much at all but you can feel it.

[bambam]

Originally Posted by Mark McM

Were you braking less with the Hors than the other bikes, or perhaps had a better (more aero position)? A 10% speed increase seems a bit much just by adding a little more flex in the rear. The force to overcome air resistance increases with the square of speed, and since the majority of the drag at 55 mph is air resistance, the air resistance would have gone up by nearly 20%. I don't think there's enough rolling resistance/suspension drag losses for a reduction in these to make up for the 20% difference.

For my own anecdote, there is one hill around here where my speed on the same bike has varied between 46 mph and 55 mph - but the big variable in these cases was wind (head wind vs. tail wind), which can vary quite a bit in that area.

I don't doubt that there could be some amount of speed improvement by adding some rear suspension, but on reasonably good pavement, 5 mph seems a bit much.

As stated "caveat: not sure I was using the same computer and the Hors is longer and lower that most my bikes with a 130 stem. (usually ride a 110-120)."
That stem is a quill titanium that I can flex with pressure.
And what I learned from real world use of hard rubber wheels on rollerblades with different durometers.

The positioning is more aero that other bikes I have taken on that hill.

I believe the positioning added speed. Also the fact that I was more relaxed because It was smoother (stem and stays)and I felt connected better to the road. Wind is usually negligible on this hill.

The hors has always made me feel like I'm decending 5-10 mph slower than I actually am. Due to soaking up the road and positioning.

Maybe breaking less because of the feel and positioning.
Bike and feel are all factors that attribute to break needs.

it is a constant right curving downhill.

Bambam