Compact Geometry Question

[Scott]

Hi, I have been out of the road cycling scene for more than 10 years. I
want to get back into it and I am looking for a new bike. I see a lot
of bikes with "Compact" geometries. I have read that this is to make it
easier to fit a bike to the customer because the manufacturer only
needs to make a few frame sizes.

Can anyone describe to me the pros and cons of these geometries vs more
traditional ones?

Thanks,
Scott

 

[Mike Jacoubowsky]

Hi, I have been out of the road cycling scene for more than 10 years. I
> want to get back into it and I am looking for a new bike. I see a lot of
> bikes with "Compact" geometries. I have read that this is to make it
> easier to fit a bike to the customer because the manufacturer only needs
> to make a few frame sizes.
>
> Can anyone describe to me the pros and cons of these geometries vs more
> traditional ones?


Top-tube length is often the key to proper fit, and to the extent that a
manufacturer reduces the number of sizes (when using a compact geometry),
fit suffers. It doesn't have to; if a manufacturer chooses to make a
"compact" frame design and retain a reasonable number of sizes (6? 7? Tough
to know, but it's certainly more than 4!), then what you've got is basically
differing style points and an enhanced ability to fit someone with very sort
legs but a longer torso.

As far as saving weight, there are limits to what can be accomplished, since
a longer seatpost adds weight, and the increased leverage it applies to the
frame means it (the frame) has to be made a bit heavier in that region. It's
mainly all about looks, or, for manufacturers making fewer sizes, saving
money.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com

 

[nash]

That' right and Cap's made me buy a smaller frame by saying it was stronger
and I was sorry for that. Stretching out give you more power. That is how
your body geometry works never mind their cocomamy bike geometry.

SN

 

[John Thompson]

On 2007-02-05, Scott <[email protected]> wrote:

> Hi, I have been out of the road cycling scene for more than 10 years. I
> want to get back into it and I am looking for a new bike. I see a lot
> of bikes with "Compact" geometries. I have read that this is to make it
> easier to fit a bike to the customer because the manufacturer only
> needs to make a few frame sizes.

It doesn't make it easier to fit a bike to a customer; it just makes it
easier for the manufacturers and shops who don't have to make or stock
so many sizes.

A custom designed frame will take into account many factors, including
leg length, torso length, intended use and riding style, etc.
Mass-produced frames in a limited number of sizes must compromise on
many of these factors.

--

John ([email protected])

 

[rdclark]

On Feb 5, 1:04 am, Scott <[email protected]> wrote:

> Can anyone describe to me the pros and cons of these geometries vs more
> traditional ones?

If the frame puts your head, hands, and feet where you need them to
be, then it hardly matters what the angle of the top tube is. Compact
frames can run the same gamut of stiffness that other frames do, and
given all the variants in tube design, frame material, and other
aspects of frame geometry, pointing at one factor (top tube angle) and
suggesting that a frame derives all its riding character from it, is
silly.

I suggest evaluating bikes by fit and feel, the way you normally
would, and let the top tube angle be a minor factor in your decision.
If a frame doesn't fit, it will be because one or more of its
dimensions is wrong for you -- the effective top tube length is too
long or too short, or the seat tube angle is too shallow or too steep,
or the head tube is too short to allow you to easily set the bars high
enough, or something like that -- and compact frames have the same
kinds of measuments as any other bike.

Personally, I have two bikes with traditional geometry and one with a
compact frame. All three fit the same, although they are otherwise
quite different from one another, which is the empirical reason for my
opinion on this.

RichC

RichC

 

[David L. Johnson]

Scott wrote:
> Hi, I have been out of the road cycling scene for more than 10 years. I
> want to get back into it and I am looking for a new bike. I see a lot of
> bikes with "Compact" geometries. I have read that this is to make it
> easier to fit a bike to the customer because the manufacturer only needs
> to make a few frame sizes.

How does it work that fewer sizes will fit the same collection of
riders? A compact frame can possibly be jerry-rigged to be ridable by
more riders than a standard frame, in that you could get on/off a bike
that is way to big for you if the top tube doesn't bash up the boys, but
that is not the same as saying it fits.

On the other hand, if you are like me, a "perfect 56", then most
manufacturers will make a bike that fits you well, sloping or flat top
tube. But it does not offer any advantage, except in terms of being
able to make do with a bike that really doesn't fit. Why spend
thousands of dollars for that?
>
> Can anyone describe to me the pros and cons of these geometries vs more
> traditional ones?

I think they are ugly. But, then, most new bikes are.

--

David L. Johnson

It is a scientifically proven fact that a mid life crisis can only be
cured by something racy and Italian. Bianchis and Colnagos are a lot
cheaper than Maserattis and Ferraris. -- Glenn Davies

 

[Tom Keats]

In article <[email protected]>,
"David L. Johnson" <[email protected]> writes:
> Scott wrote:
>> Hi, I have been out of the road cycling scene for more than 10 years. I
>> want to get back into it and I am looking for a new bike. I see a lot of
>> bikes with "Compact" geometries. I have read that this is to make it
>> easier to fit a bike to the customer because the manufacturer only needs
>> to make a few frame sizes.
>
> How does it work that fewer sizes will fit the same collection of
> riders? A compact frame can possibly be jerry-rigged to be ridable by
> more riders than a standard frame, in that you could get on/off a bike
> that is way to big for you if the top tube doesn't bash up the boys, but
> that is not the same as saying it fits.

From doing a little Googling, I perceive a
concensus to the effect that "traditional
geometries" allow for finer fit adjustments
than do so-called compact geometries.

>> Can anyone describe to me the pros and cons of these geometries vs more
>> traditional ones?
>
> I think they are ugly. But, then, most new bikes are.

It also seems at least some compact geometry designs
are applied with the intent of making bicycles which
are "twitchier" and more responsive -- e.g: shorter
chainstains to reduce wheelbase. I guess that in
conjunction with an agressive headtube angle and
maybe some other features might be considerations
in a purpose-built crit bike. Apparently comfort
is at least one trade-off.

There may be some contention about whether compact
geometries have some intrinsic aerodynamic advantage
(I suspect if they do, any advantage would be so small
that it would easily be overshadowed by other factors.)

I also noted some interest in compact geometries
especially among the triathlon community. And
we all know how prone they are to come up with
weird notions ;-)


cheers,
Tom

--
Nothing is safe from me.
Above address is just a spam midden.
I'm really at: tkeats curlicue vcn dot bc dot ca

 

[David L. Johnson]

Tom Keats wrote:

> From doing a little Googling, I perceive a
> concensus to the effect that "traditional
> geometries" allow for finer fit adjustments
> than do so-called compact geometries.

No, that's not really it. Compact frames are marketed with fewer sizes.
The number of sizes needed to properly fit most people --- most
importantly being the effective top tube length -- is independent of the
type of frame. Dealers in compact frames expect the buyer to adjust to
fewer sizes, as I said before because the single least important part of
sizing (straddle clearance) is not an issue.

> It also seems at least some compact geometry designs
> are applied with the intent of making bicycles which
> are "twitchier" and more responsive -- e.g: shorter
> chainstains to reduce wheelbase.

Nah. That is a function of the chainstays, not the top tube, and lots
of traditional frames have very short chainstays. "Twitchiness" also
comes from the angles of the head tube, again not a thing specific to
compact frames.

> There may be some contention about whether compact
> geometries have some intrinsic aerodynamic advantage
> (I suspect if they do, any advantage would be so small
> that it would easily be overshadowed by other factors.)

That stuff is marketing BS
>
> I also noted some interest in compact geometries
> especially among the triathlon community. And
> we all know how prone they are to come up with
> weird notions ;-)

Yeah, well, you wanna buy some 650c wheels?

--

David L. Johnson

Do not worry about your difficulties in mathematics, I can assure you
that mine are all greater. -- A. Einstein

 

[Qui si parla Campagnolo]

On Feb 5, 6:32 pm, "David L. Johnson" <[email protected]>
wrote:
> Scott wrote:
> > Hi, I have been out of the road cycling scene for more than 10 years. I
> > want to get back into it and I am looking for a new bike. I see a lot of
> > bikes with "Compact" geometries. I have read that this is to make it
> > easier to fit a bike to the customer because the manufacturer only needs
> > to make a few frame sizes.
>
> How does it work that fewer sizes will fit the same collection of
> riders? A compact frame can possibly be jerry-rigged to be ridable by
> more riders than a standard frame, in that you could get on/off a bike
> that is way to big for you if the top tube doesn't bash up the boys, but
> that is not the same as saying it fits.

Reality, what a concept.
>
> On the other hand, if you are like me, a "perfect 56", then most
> manufacturers will make a bike that fits you well, sloping or flat top
> tube. But it does not offer any advantage, except in terms of being
> able to make do with a bike that really doesn't fit. Why spend
> thousands of dollars for that?
>
>
>
> > Can anyone describe to me the pros and cons of these geometries vs more
> > traditional ones?
>
> I think they are ugly. But, then, most new bikes are.

Reality, what a conceptx2
>
> --
>
> David L. Johnson
>
> It is a scientifically proven fact that a mid life crisis can only be
> cured by something racy and Italian. Bianchis and Colnagos are a lot
> cheaper than Maserattis and Ferraris. -- Glenn Davies

 

[Curtis L. Russell]

On Mon, 05 Feb 2007 20:32:50 -0500, "David L. Johnson"
<[email protected]> wrote:

>I think they are ugly. But, then, most new bikes are.

Ever since they stopped using custom lugs. I still remember a red and
white Sachs frame worth killing for. Then again,there are a few people
I'm just looking for the right excuse...

Curtis L. Russell
Odenton, MD (USA)
Just someone on two wheels...