Difference between straight & sloping frame

boudreaux said:

.... some people with short legs may fit compacts better.

Spoken by someone who does not have short legs.

In "general" compact frames are more square, (virtual) toptube
length is close to seat tube length, and seat tube angle is a little
steeper (0.5 deg?), although I think the seat tube angle change
is a trend across all frames over the past 10 years?.

Both of these changes; steep seat tube and short top tube,
disadvantage a person who's leg to height ratio is lower -

ie compact frames are not good for people with short legs (me)

regards,
Matthew

boudreaux said:

By golly, that really explains why
Giant makes their aluminum frames in compact doesn't it?

Actually some of the Giant alu frames are hydroformed, which requires moulds, so the cost of moulds could be a factor for these frames.

mjw_byrne said:

Actually some of the Giant alu frames are hydroformed, which requires moulds, so the cost of moulds could be a factor for these frames.

Methinks the tubing may be shaped by hydroforming,but it still has to be welded together.

MattAussie66 said:

Spoken by someone who does not have short legs.

ie compact frames are not good for people with short legs (me)

regards,
Matthew

And alot of short legged people would disagree.

boudreaux said:

And alot of short legged people would disagree.

If standover height (whilst dismounting in front of cafe) is all you are
interested in - then yes compact frames and short legs are a good match. 😄

If you want to pedal the bl@@dy thing anywhere then the position
of the seat/bb/bar will "generally" place a relatively long body too far
forward on a compact design frame - not because the frame is compact,
but because compact frames are "usually" designed with steeper seat
tubes and shorter (virtual) top tubes - I guess it is just a fashion thing.

So Boudreaux - I'm 5'10.5" (179cm) high and my inside leg is
31.5" (78.5cm) giving me a leg to height ratio of 0.44 which puts me
close to 2 standard deviations from the mean in the direction of
short legs & long body

- what are you?

regards
Matthew

MattAussie66 said:

So Boudreaux.........what are you?

Eh.......he goes to bed early -- don't expect a quick reply 😄

boudreaux said:

Methinks the tubing may be shaped by hydroforming,but it still has to be welded together.

Ah-ha, OK. I was under the impression the frames are hydroformed after welding (making the nice smooth welds you see on e.g. an alu TCR).

MattAussie66 said:

If you want to pedal the bl@@dy thing anywhere then the position of the seat/bb/bar will "generally" place a relatively long body too far forward on a compact design frame ...

ie compact frames are not good for people with short legs (me)

Again, I would disagree. I'm 5' 5", certainly don't have long legs and feel perfectly fine (bike was "fitted"😉 on my Litespeed compact.

MattAussie66 said:

If you want to pedal the bl@@dy thing anywhere then the position
of the seat/bb/bar will "generally" place a relatively long body too far
forward on a compact design frame - not because the frame is compact,
but because compact frames are "usually" designed with steeper seat
tubes and shorter (virtual) top tubes - I guess it is just a fashion thing.

In general, I think your bloody generalizations are all wet.

boudreaux said:

By golly, that really explains why
Giant makes their aluminum frames in compact doesn't it?

By some I clearly meant all, especially Giant. But you made my point for me anyway. I see that the TCR Alloy only comes in five sizes.
Even though the hydroforming is done before welding, they still need a different mold for each length tube.

artmichalek said:

Even though the hydroforming is done before welding, they still need a different mold for each length tube.

Maybe they are clever enough to use one mold and then trim the ends to size.

boudreaux said:

Maybe they are clever enough to use one mold and then trim the ends to size.

It's so clever it makes me wonder why companies have been drawing their butted tubes to length all these years when they could just be trimming the ends. Even if it was that easy, it doesn't explain the limited sizing. Maybe they're just clever enough to design and manufacture tubes to fit the frame instead of doing something half assed like cutting down the ends just to get more sizes.

artmichalek said:

It's so clever it makes me wonder why companies have been drawing their butted tubes to length all these years when they could just be trimming the ends. Even if it was that easy, it doesn't explain the limited sizing. Maybe they're just clever enough to design and manufacture tubes to fit the frame instead of doing something half assed like cutting down the ends just to get more sizes.

Butted tubes are trimmed to length.You really think they make a specific set for every possible frame size? LOL.
The limited sizing is aimed at the bottom line and econmy of production for some makers.Others offer more sizes than some.

boudreaux said:

Butted tubes are trimmed to length.You really think they make a specific set for every possible frame size? LOL.
The limited sizing is aimed at the bottom line and econmy of production for some makers.Others offer more sizes than some.

Exactly. Tubes are made in one size and then cut mitred at each end. Just look at any frame with a shape in the centre section of the tube and compare it across the range of sizes. You'll see the shaped sections are all the same length.