Why is an 80 degree STA somewhere near optimal for a tri bike and not something like 90?
I can see why hip angle would be a crucial parameter, but given the ‘optimal’ hip angle (whatever that is for a given triathlete) why not keep rotating them forward until the back is level? I know there is a +5cm rule but given that plus nose riding someone can, within the USAT rules, get an effective STA of over 90 degrees.
I imagine that at some point beyond 80-82 degrees you exceed the tipping point where the weight bias is not optimal. A 90 deg. STA could put too much weight on the front end. This would certainly affect handling and lead to upper body fatigue since that part of the body is not designed to hold our body weight.
So it comes down to comfort?
I can see the bike being hard to handle when it’s designed for a vastly different STA, but if it was designed with this in mind then it should be OK wouldn’t you think? (longer wheelbase, more fork rake)
It is against the rules, that is why you do not see 90 degree bikes anymore. I say anymore, because there used to be some, in fact Scott Molina rode one for awhile, perhaps if he reads this, he can comment on that expirence. From what I gather, it makes little difference if you can handle your bike ok. I’ve had most of my bikes set up at 84 to 87 over the years, and nose ride so I’m basically riding at 90 sometimes. 89 is where it all began, then it inched foreward from there, then they made rules about it. SO I believe 80 is just about perfect for todays tri bikes, and allows folks to go a bit foreward/backward to suit their needs…
I’m only speculating since I don’t know the answer. Comfort may play a role in that someone discovered that there is not enough aero or power advantage to riding at 90 deg. (over 80) but that there was more discomfort. I imagine that over the years a wide range of angles was tried and natural selection settled in on around 80 deg.
If the bike was designed for it, then yes, handling would be better. But any given manufacturer probably doesn’t want to be the oddball in designing bike geometry. They seem to stick together in a narrow band of STA choices.
Thanks for your input Monty. Let me get clarification on your statement that it’s against the rules. USAT allows the nose of the saddle to be up to 5cm IN FRONT OF the bottom bracket. If you ride on the front of the seat you can legally get to 90 degrees.
Also, you say that 80 degrees is just about perfect. Wouldn’t you also agree that aerodynamically a horizontal back is also perfect? Do you ride with an 80 degree hip angle then along with your 80 degree STA?
Thanks.
USAT allows the nose of the saddle to be up to 5cm IN FRONT OF the bottom bracket. If you ride on the front of the seat you can legally get to 90 degrees.\
That is what I meant, if you have a 90 degree seat angle, you will be further ahead than the 5cm limit…Unless you slam the seat all the way back, but what would be the point of that??
I think a flat back is fine, but most important in my opinion is a powerful/ comfortable, position that shows the least frontal area to the wind. SOmetimes that is done with a flat back, sometimes not, depends on each rders body, and their ability to ride other positions. Not usre what my hip angle is, have to get Dan or Jordan measure me out sometime. I came to my position through a lot of trial and error, and looking at other sucessful riders and what they did. In the beginning of any endevour like a new bike fitting, or coaching philosophy, or new diet, I think this is how a consensus is finally arrived at. Those on the cutting edge of the performance side expirementing, and later on ,those that love to analyze those folks and try to come up with some universal truths about the process…
For clarification: I meant the effective STA, not the bike’s actual STA hence our misunderstanding.
Thanks for your help.
My set-up:
BB to center of rails - 81.5 degrees
One inch from tip of saddle - 90 degrees
Which makes sense when you consider my saddle tip is +2.5cm from BB.
So my effective STA is greater than 90 and that is, on average, where I ride. And I will gravitate back to that position again and again. And I have not seen my improvements limited by my position after 3 years of serious bike training. Most of the serious athletes who I fit fall into the 85-90 degree range when self-selecting seat angles based on comfort and perceived (and usually actual) power producing ability. That is effective STA, actual STA being in the common 78-82 degree range when measured to the center of the rails.
Dave Luscan
www.endorphinfitness.com
My set-up:
BB to center of rails - 81.5 degrees
One inch from tip of saddle - 90 degrees
Which makes sense when you consider my saddle tip is +2.5cm from BB.
So my effective STA is greater than 90 and that is, on average, where I ride. And I will gravitate back to that position again and again. And I have not seen my improvements limited by my position after 3 years of serious bike training. Most of the serious athletes who I fit fall into the 85-90 degree range when self-selecting seat angles based on comfort and perceived (and usually actual) power producing ability. That is effective STA, actual STA being in the common 78-82 degree range when measured to the center of the rails.
Dave Luscan
www.endorphinfitness.com
Dave, thanks for that insight. Can you tell me what your hip angle is (estimate at least)? What about some of the other athletes that you’ve fit at around a 90 degree effective STA? (I’m assuming that’s around 90 also for aerodynamics).
Wasn’t a Desert Princess built with a 90 degree STA? Back in the neon days.
One issue I have as I’ve moved my position further forward over the last few seasons (currently saddle tip is +1cm past vertical w/ BB)… you’re almost effectively in a standing position as far as your lower body is concerned relative to the cranks, only you’re straddling the saddle at the same time. That’s well and good the 98% of the time you’re humming along in the aero position, but for the brief occasions when you actually need to stand for real (starting/stopping, steep climbs) there’s not really anywhere else to go so the nose of the saddle isn’t jabbing you in the ass. In a more conventional road position, you end up shifting way forward as you stand, but at ~90* you’ve already “used up” that arc.
It is been my experience when the athlete is perceptually aware and in tune with their bodies, that hip angle always falls within spitting distance of 100 degrees. I’m not even surprised anymore when it is exactly 100. I tend to check that last after they have acheived their ‘favorite’ position. And for those less aware, as I nudge their positions into place, and we get close to that 100 degree angle, they usually prefer it, they just have a harder time finding it on their own.
And yes those 85-90 degree positions allow everything else to be in place to take aerodynamic advantage of the time trial position. Though with minimal adaptation, my power doesn’t suffer any drop-off while aero. I actually ride that way as I make the most power there, while being quite aero. And did* *mention comfortable?
Dave Luscan
www.endorphinfitness.com
Wasn’t a Desert Princess built with a 90 degree STA? Back in the neon days.\
Ya, it was the Holland bike, but they were all custom bikes. But a lot of them were build with 90 degree seat angles, and they had the prettiest paint jobs ever…
One issue I have as I’ve moved my position further forward over the last few seasons (currently saddle tip is +1cm past vertical w/ BB)… you’re almost effectively in a standing position as far as your lower body is concerned relative to the cranks, only you’re straddling the saddle at the same time. That’s well and good the 98% of the time you’re humming along in the aero position, but for the brief occasions when you actually need to stand for real (starting/stopping, steep climbs) there’s not really anywhere else to go so the nose of the saddle isn’t jabbing you in the ass. In a more conventional road position, you end up shifting way forward as you stand, but at ~90* you’ve already “used up” that arc.
You’re right. not to mention the arm pads are usually within an inch of the knees while seated so they get in the way too.
But I consider this a compromise that must be made for a better position (hence performance) during most of the rest of the ride.
Agreed- this is why if you ride really steep (i do too- tip of saddle 2cm in front of bb) you basically HAVE to have two race bikes- one for hills and one for flat courses.
My “flattish” race bike is set up super steep, and my “hill course” bike (built for st croix) is a road bike with extensions. I find it very difficult to stand up on my “flat course” bike because the gap between “butt hits sadle nose” and “knees hit elbow pads” is very small- i can ride standing but the margin of error is tiny.