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PaMtbRider
12-22-2010, 06:16 PM
When a ready custom frame is selected a choice can be made between race or performance geometry. Does anyone know if there are any differences between the two choices besides geometric dimensions? i.e. Does the tubing selected for a frame with race geometry have different butting or thickness to change the ride when compared to the same frame with performance gemetry?
dekindy
12-22-2010, 07:10 PM
I would expect a race frame to be generally made with stiffer tubing and have a shorter wheelbase versus a performance oriented frame. Read David Kirk's article on frame stiffness and realize that it does not necessarily have to be that way. I have also read and heard comments from Ben Serotta that it is not good enough to design a frame to go faster. It also has to feel faster to the rider or they will not be satisfied.
dave thompson
12-22-2010, 07:24 PM
In reading the geometry chart here: http://www.serotta.com/assets/documents/2010_ready_custom_geometry.pdf it appears the 'race' geometry is long and low compared to the 'performance' geometry; shorter head tubes, longer top tubes, higher bottom bracket, longer reach and lower stack, just like a race bike.
PaMtbRider
12-22-2010, 08:16 PM
Read David Kirk's article on frame stiffness ...
I looked at his site site but couldn't find this article, could you point me to it.
Songline
12-23-2010, 09:53 AM
I looked at his site site but couldn't find this article, could you point me to it.

Here you go:

http://www.kirkframeworks.com/Flex.htm
benb
12-23-2010, 10:42 AM
I have also read and heard comments from Ben Serotta that it is not good enough to design a frame to go faster. It also has to feel faster to the rider or they will not be satisfied.

Do you have a link to that? That sounds really interesting to read. It makes me wonder if it is possible that some bike companies even jump to making frames overly stiff in a way that produces a slower bike, but it sells better, so they continue to make the frames stiffer and stiffer.
David Kirk
12-23-2010, 10:57 AM
It makes me wonder if it is possible that some bike companies even jump to making frames overly stiff in a way that produces a slower bike, but it sells better, so they continue to make the frames stiffer and stiffer.

IMO you absolutely nailed it. I've been saying this for as long as I can remember and I know I lose business because of it - but it's the truth. Stiffer is not always better. Everything in moderation and the stiffness is best when it matches the rider's needs.

Dave
dekindy
12-23-2010, 11:04 AM
Do you have a link to that? That sounds really interesting to read. It makes me wonder if it is possible that some bike companies even jump to making frames overly stiff in a way that produces a slower bike, but it sells better, so they continue to make the frames stiffer and stiffer.

Ben Serotta gave a presentation at Bicycle Garage Indy (my favorite LBS) during the NAHBS when it was held in Indianapolis. He told a story about the development of one of the frames, I forget which one. He was able to ride a known route faster than he ever had before. However the frame did not feel faster. So they kept engineering the frame until it not only rode faster, but also felt faster. Have you ever felt bad and thought you had a horrible ride on a known training course only to look at your computer and discover your average speed was the same as the previous ride when you felt really strong? That's the analogy that I would use.

It was probably either the Meivici or the HSG. He also said that the Ottrott was his favorite model.
jr59
12-23-2010, 11:04 AM
The more I read of you Dave, the MORE I want one of your bikes.
benb
12-23-2010, 11:11 AM
Yes same here.. probably a long time before I will be able looking for a new bike but just that level of honesty is pretty amazing.

I definitely know that feeling of thinking the ride doesn't feel great and it turns out I'm flying.. although when I'm really at my best it usually doesn't feel that way.
SPOKE
12-23-2010, 11:19 AM
High frequency vibration feels fast but actually robs some speed.
PaMtbRider
12-23-2010, 02:09 PM
This is pretty common in mountain biking. Someone thinks they are faster on a hardtail until they see actual lap times. In a lot of cases a full suspension bike is faster but doesn't feel like it to the rider because they are equate a rough ride to higher speed.
David Kirk
12-23-2010, 02:54 PM
This is pretty common in mountain biking. Someone thinks they are faster on a hardtail until they see actual lap times. In a lot of cases a full suspension bike is faster but doesn't feel like it to the rider because they are equate a rough ride to higher speed.

This is one of the reasons the early Cannondales sold so well. I worked at a dealer and we sold a large number of them. The bosses favorite ways to sell one was to inflate the tires to 150 psi and let the guy test ride one. They felt they were going so fast because there was so much buzz it had to be fast.

I bought one too. I sold it two weeks later.

Dave
Brian Smith
12-23-2010, 10:18 PM
When a ready custom frame is selected a choice can be made between race or performance geometry. Does anyone know if there are any differences between the two choices besides geometric dimensions? i.e. Does the tubing selected for a frame with race geometry have different butting or thickness to change the ride when compared to the same frame with performance gemetry?

Yes, for each ready custom build sheet, the tubing selection as well as the geometry is tailored to the individual bike. This is most apparent in the carbon tubed models, as the tunability range is highest there.
MadRocketSci
12-24-2010, 05:28 PM
This is one of the reasons the early Cannondales sold so well. I worked at a dealer and we sold a large number of them. The bosses favorite ways to sell one was to inflate the tires to 150 psi and let the guy test ride one. They felt they were going so fast because there was so much buzz it had to be fast.

I bought one too. I sold it two weeks later.

Dave

People like stiff bikes because they tend to be light and give that "rocketship" feeling...ie, OMG, the thing just shoots/lurches/rockets out from under me, it's a freakin buckin bronco that must be tamed by my studly ass..

I have a hypothesis on what is going on, dunno if it is old news. But anyways, the only thing that is going to turn the wheels is torque about the bottom bracket. To apply torque, you have to produce a force on the pedal exactly along the circular path of the pedal, ie, perpendicular to the crank. This probably doesn't happen, and the remaining tangential (along the crank) force results in a force on the bike itself in the forward direction. If the bb is stiff, the force goes into forward bike motion, if it is less stiff, the bb deflects a little, possibly resulting in less force on the bike since the deflection could result in less forward force (F = kx). Anyway, you put a force on the stiff bike, the bike moves forward, however, the bike puts an equal an opposite force on you, so you accelerate backwards, end result, OMG THIS BIKE JUST WANTS TO GO IT'S LIKE A FREAKIN SCALDED CAT!!!

Does xtra stiffness help overall acceleration? not in my view. having more or less is a matter of personal preference.
soulspinner
12-25-2010, 06:34 AM
IMO you absolutely nailed it. I've been saying this for as long as I can remember and I know I lose business because of it - but it's the truth. Stiffer is not always better. Everything in moderation and the stiffness is best when it matches the rider's needs.

Dave


Got rid of a Colnago Master(yellow, chromed hl and front precisa fork). Sitting on a bike that skitters due to excessive stiffness is not fun. Probably great for someone 25 pounds heavier, but for me it was too stiff.
spartacus
12-25-2010, 11:35 AM
He also said that the Ottrott was his favorite model.

This I've read more than once before. How does he view the Meivici and HSG SuperComp frames in comparison to the Ottrott?
dekindy
12-25-2010, 12:20 PM
This I've read more than once before. How does he view the Meivici and HSG SuperComp frames in comparison to the Ottrott?

All I know is the obvious; they are less favorite! :)

All the current models were on the market when he made that statement.
dd74
12-25-2010, 12:37 PM
Sitting on a bike that skitters due to excessive stiffness is not fun. Probably great for someone 25 pounds heavier, but for me it was too stiff.
I've had the same issues, and oddly, they were steel frames. At the time, I wondered if it was as much a stiffness issue as potentially a fit issue. But more than likely, I think it was from having a frame that was too stiff.

And yes, that skittering truly does slow a person down.