[CowboyLeo]

Just a suggestion (more of a plea) but...

-because many more bikes are using head angles and seat angles that don't match and
- freeriders spend more time off of the saddle than on it and
- a measurement that told you how the bike will feel when the rider is standing will be useful to anyone regardless of how they ride (unless you never stand up) i believe a new method of frame measurement is needed not in ten years not when shimano says so but NOW

In some old thread Binary Visions suggested a measurement straight up from the BB to the top of the head tube. Does anyone do this? (read: can everyone do this please)

even better why not also provide the effective top tube length AS IF measured with the seat tube changed to match the head angle ALONG WITH the real effective top tube length and BBtoHT length

If a few companies start doing this then it might set a trend and within a while we might have an industry wide method of frame fitting thats reasonable and functional

how could it hurt? manufacturers need only post the measurements up on their websites (in a top secret hidden corner in really small font if they're afraid of being persecuted and burned at the stake for being different and not using obscure and antiquaited measurements)

all we need is a few willing people who agree on a measurement (maybe some diagrams are in order) and decide to post up their measurements along with whatever other method they used originally

this thread can be a start

 

[dw]

I think what you suggest is a good idea, and it has been discussed quite a bit here in the past. Personally, I use Front center for a lot of measurement discussion, and also the distance from the center of the BB to the bottom of the head tube at the steering axis.

Bicycle frame geometry can get pretty complex to discuss (in relation to feel) because so many factors are interdependant with each other.

dw

 

[xy9ine]

i agree a new standard figure for demonstrating cockpit length should be used - bb to lower headtube might be the figure to go with. "theoretical" toptube lengths on bikes with wack seattube configurations/angles (ie, imperial, tmx) are confusing at best.

 

[kidwoo]

The first measurement I always take on a new bike is pretty much what you guys are talking about. I measure BB center to the intersection of the theoretical centerlines of headtube and down tube. I was looking at a few bikes a while ago with movable seat towers and it was driving me crazy that manufacturers just wanted to give top tube measurements.

Circulate a petition at interbike this year.

 

[Leethal]

and a few other BMX companies have use the bb to top of headtube for a while now.

 

[Kornphlake]

it's a cool idea but it still really means nothing, you can have a really short wheelbase with a tall fork and the bb to the top of the HT measurement will be the same as a bike with a longer wheelbase and a shorter fork. Sure if there was some standard that says all bike dimensions will be stated in terms of the bb height from the ground to the center of the BB, the angle of the line from the top of the headtube to the center of the bb (to adjust for fork length) and the length of said line then we'd be somewhere, just a length of a theoretical line is pretty useless.

 

[CreeP]

I'm with you 145% leo, and have been since i first considered geometry as an important part of a bike!

 

[binary visions]

Originally posted by Kornphlake
it's a cool idea but it still really means nothing, you can have a really short wheelbase with a tall fork and the bb to the top of the HT measurement will be the same as a bike with a longer wheelbase and a shorter fork. Sure if there was some standard that says all bike dimensions will be stated in terms of the bb height from the ground to the center of the BB, the angle of the line from the top of the headtube to the center of the bb (to adjust for fork length) and the length of said line then we'd be somewhere, just a length of a theoretical line is pretty useless.

Well, if you're going to say that, you may as well say that the head angle measurement of a bike is useless, after all, they could have a Super Monster on it...

It is, of course, dependant on knowing the fork height (which 90% of manufacturers list when listing geometries).

 

[Rik]

I think manufacturers really need to provide as much info as possible. There's no use knowing the basic ST/SA/TT/HA, as they're pretty much useless without knowing everything else as well. I'd like to see more companies giving almost EVERY dimension there is, and at what fork height these measurements were taken. Even then, sag will still affect the feel of the bike, but that can be taken in to account by the rider.
Without knowing every measurement, we might as well just have S, M, L as our frame sizes with nothing more mentioned.

 

[binary visions]

THIS is what all geometry charts should look like:

http://www.cannondale.com/bikes/04/geo-1.html

Lots of measurements, tells you how long the fork was, and a diagram telling you explicitly how they were measured (i.e. BB height was measured ground to bottom of the shell, not middle of the BB).

 

[CowboyLeo]

Originally posted by dw
I think what you suggest is a good idea, and it has been discussed quite a bit here in the past. Personally, I use Front center for a lot of measurement discussion, and also the distance from the center of the BB to the bottom of the head tube at the steering axis.

Bicycle frame geometry can get pretty complex to discuss (in relation to feel) because so many factors are interdependant with each other.

dw

Front center? enlighten me

and yes, i'm aware that many factors are interdependant (for example longer front end making back end feel shorter) but I just believe that if people are well informed of the dimensions of their bike and with what components those measurements were taken, they would be much more capable of choosing bikes that suited them

as rik said more info is necessary for people to make decisions


all instances in which there has been widespread change for the better, whether technological social or whatever have come about from people being informed and educated so I am just asking for information and education

 

[CreeP]

front center is the distance from your front axle to your bb, basically the compliment of the chainstay measurement.

it changes a lot with fork length and offset, though you don't get much deviation in offset with mountainbikes.

 

[thaflyinfatman]

Doesn't Endless already do this?

 

[zane]

Originally posted by binary visions
THIS is what all geometry charts should look like:

http://www.cannondale.com/bikes/04/geo-1.html

Lots of measurements, tells you how long the fork was, and a diagram telling you explicitly how they were measured (i.e. BB height was measured ground to bottom of the shell, not middle of the BB).

That chart is IN-DEPTH, all manufacturers should be doing this...

 

[Brian HCM#1]

That is a cool Cannondale chart, however what is the correct way to measure the TT? It seems like its done 1000 different ways, is there a correct standard?