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On Sun, 20 Mar 2005 23:09:25 +0000, Simon Brooke
wrote:

in message , Martin Wilson
') wrote:

I've never seen a cheap bike with terrible alignment or substandard
components.

Then you haven't seen many cheap bikes. I've seen (and tried to adjust
to some semblance of roadworthiness) several. I've seen at least one
brand new 'Universal' brand bike in the past fortnight where the front
dropouts were so far out of line that the front brake could not be made
to work at all.

Universal are an importer they don't make bikes. They are supplied
with bikes by low cost factories in taiwan, china, vietnam, india etc.
The same factories supply other brands including Raleigh, Falcon,
concept etc. Some of the companies used are idealbikes, abeni, forever
cycles, roadmaster (india) and quite a few others.

What was the make and model of the universal bike in question ?(yes I
realise it's imported by universal but many of their bikes are given
other brand names)

In article ,
Ian Smith wrote:

On Tue, 22 Mar 2005, Martin Wilson wrote:

So your basically saying sheldon brown doesn't like them so the extra
welded length of stays to the top tube has absolutely no improvement
in strength at all. The fact the seat stays have two welded/anchor
points does not add any strength what so ever.

Absolutely. In fact, by adding local bending top teh tubes by loading
them other than at teh node points of the truss, if anything, you'll
weaken teh frame. They've taken a nice tidy shape that is
intrinsically rigid without introducing local bending in teh elements
of teh frame, then converted it to something that relies on local
bending.

real world users seem to accept GTs on this level and they have an
excellent reputation for strength. After reading various postings

So they make teh tubes thicker to compensate for poor design - doesn't
make teh design good, and especially doesn't make it efficient.



Spot on Ian.

As another example of bad design...

Consider this bike...

http://www.dialledbikes.com/albert.htm

To the uninformed, they'd think this hardtail which is meant for long
travel suspension forks would be stronger because of the extra tube
reinforcing the headtube area, but all the strut does is make the head
area more rigid and concentrate the forces that would usually rip a head
tube off into the weakest part of the bike - the thin walled main tubes
so it's LESS strong than a normal diamond frame or one with well done
side plates that transfer the head tube stress into the sides of the
main tubes.

The GT design is less of a problem as it's less stressed so is mostly
cosmetic.

And I can work this out without FEA software. ;-)

Shaun

In article ,
Martin Wilson wrote:



Yeah right like I was suggesting there was about 3 inches of movement
or something. You must surely realise that even a tiny amount of
movement like 2mm or 3mm would still have a shock reducing effect and
would be instantanously corrected.

They don't even move that much with few exceptions - Ritchey Plexus
being the obvious example, which you'd notice also has quite poor
braking performance if you've ever ridden one.


I don't know what your imagination
is up to but I can assure you my seat and chain stays do not operate
like some sort of elastic bands. Its well documented that the GT
triple triangle frame design is more rigid because it supports the
seat stays at both the seat tube and top tube with welds.

It's also bunkem. There's no merit in the design at all.


As a heavier
rider I'm obviously going to get more movement there.


If you sit on a brick do you expect it compress more than if I sit on it?
Ok, perhaps it does at some sub-atomic level but like the forces in a
bike rear triangle, it's negligible.



What is your
problem? Are you saying high tensile steel is not capable of flexing
slightly under loads?


Not saying that at all but in the context of a bicycle frame's rear
triangle, it's irrelevant.

What's more important is the quality of the welds joining everything
together and on cheap Hi-Ten or for that matter cheap cromo or aluminium
bikes, that's usually where they fail.


Surely its aluminium frames which can be damaged
by excessive constant flexing and they would have thicker seat/chain
stays.

But chain stays are usually built not to flex AT ALL no matter what you
make them of.

The exception being the Plexus and softtail bikes like Moots and the
Ibis Ripley - both of which I've ridden. The Ripley was made entirely of
aluminium and had about an inch of travel in the rear. It used a
completely flat plate of aluminium, like a ruler, for a chainstay.

Castellano, who designed the Ripley, is an ex-aircraft engineer. He went
on to start his own bike company - http://www.castellanodesigns.com/ and
still makes completely aluminium bikes with flexible chainstays. Read
about it here - http://www.castellanodesigns.com/tech.html



As I'm riding the bike its very difficult for me to judge
technically why a frame is more comfortable all I know is it is and
admittedly my guess is the seat and chain stays because when I've read
about older bikes generally being often more comfortable using steel
frames it seems to be flexing of the seat/chain stays which is the
reason. Many older bikes use earlier possibly less advanced high
tensile steel like my Raleigh Royal.

It's a myth that has propagated down the years and still persists. It's
got nothing to do with chainstays flexing. The comfort on a steel frame
comes from the main tubes and a certain amount of splay in the wheelbase
which dampens a lot of road vibration.

It's even more of a myth on a mountain bike with big 2 inch wide tyres.
Any splay at the fork is a bad thing if you're running a suspension fork
- it just gets juddery for no reason and interferes with the forks small
bump performance. Lateral splay also messes up the handling which isn't
such a deal on a road bike but is offroad IMHO.



I can't deny the possibility that its the seat post. It doesn't feel
like the seatpost but its the only bike with a steel seatpost as far
as I can tell. I don't see how it would absorb shocks though.

Stick a ruler on a desk edge. Bend it up and down. That is what your
seatpost is doing backwards and forwards.

Now stick a pen on the edge of a desk and do the same. Bigger diameter,
less flex. That's why oversize tubed bikes feel less comfortable.

Aluminium seatposts generally flex more than steel ones too.

Now stick a set square on your desk, one edge on the desk, pointy end in
the air. Push down on the point - it doesn't flex vertically at all. It
will eventually flex laterally with a side load, but that won't happen
like that on a bike as a bike has two triangles joined at the points by
the axle, bottom bracket, brake bridge, chainstay bridge (usually) and
seat tube.


Oddly, these same people whinge on about fatigue life too. Perhaps they
should tell aeroplane designers that those big flexy wings need
replacing with some nice heavy hi-ten steel ones?


Yeah right like aeroplane wings flex about like the wings of bird, in
fact you wonder why they have to fit jet engines or props at all. I'm
pretty sure they design planes to minimise flexing/bending of the
wings. Its a known fact that as a general rule steel can flex a lot
more than aluminium without long term damage or structural problems.
Its not that aluminium can't flex/bend its just you don't want it to
because it would weaken it and shorten its lifespan.

The wings on a 747 jet flex up and down 30 feet at the ends and are made
out of aluminium, not steel. Jumbo jets fly thousands and thousands of
miles every day without their wings falling off or being replaced.

Shaun

Martin Wilson wrote:

So your basically saying sheldon brown doesn't like them so the
extra welded length of stays to the top tube has absolutely no
improvement in strength at all. The fact the seat stays have two
welded/anchor points does not add any strength what so ever.

No, I'm simply pointing out Sheldon's opinion. I haven't been able to
find any authoritative rebuttal of it, and it would be extremely
uncharacteristic of Sheldon to make such a statement in such absolute
terms without being pretty sure of his ground.

Admittedly the well documented statement is referring to mainly
GT's own information but real world users seem to accept GTs on
this level and they have an excellent reputation for strength.

Marketing material then? I'd hardly describe that as "well documented".
They may well be strong, but that could be just because they're
over-built to compensate for the poor design. Maybe they would be
stronger still with a conventional arrangement of the tubes.

--
Dave...

On Tue, 22 Mar 2005 22:51:05 +0000, JLB
wrote:

Martin Wilson wrote:
[snip several paragraphs about cheap bike frames, one of several posts
in this thread on the same subject by Martin, and it's not the first
thread where he's engaged on the subject]...
I'm not sure I
even care anyway
...[snip another couple of paragraphs]

I can hardly wait to see what you'll do for a topic you really care about.

I just made the point that of the bikes I've got the cheap bike seems
very comfortable even with its greater weight. I don't see it as
vastly inferior to my Kona, Gt or Giant. Its the bike that gets most
used and abused. It goes out in all weathers and basically gets
treated lke rubbish but I really can't fault it and don't know why
people go on about how bad some of these cheap bikes are.

Howver in the context of the posting you are referring too. I just
mentioned that GT's triple triangle is meant to have a harsher ride as
thats what I'd read and got the impression from reading over postings
on mountain bike forums. As I've said I don't care if the GT does or
doesn't have a more rigid frame.

My point is simply the cheap bike is very comfortable and if anything
seems to soften impacts more than the other bikes at the rear.

This forum seems to be full of people with opinions that cheap bikes
are;

1. Death traps
2. Unpleasant to ride
3. uncomfortable
4. incredibly heavy
5. have totally warped frames that you can't even fit wheels to or get
the brakes to work etc.
6. the frames for these bikes are stored in the back of your local
bike shop
7. The bikes are hidden away and never used.
8. They secretly enter your bedroom at night and will kill your whole
family
9. They are special magnets that will cause airliners to crash into
your house
10. Your family and anyone that goes near one will be jinxed for the
rest of their life.
11. Your children will be born with terrible disfigurements and
strange growths if you even think about buying one.
12. God himself is telling you not to buy one as its the 11th
commandment but he forgot to mention it to moses at the time.

Anyway I've sorted out a solution. I'm going to repaint the frame
yellow and paint 'Cannondale' on it instead. So now on when I mention
how much I enjoy riding my Cannondale or how good my Cannondale is it
will be accepted.

On 24/3/05 9:11 am, in article ,
"Martin Wilson" wrote:

My point is simply the cheap bike is very comfortable and if anything
seems to soften impacts more than the other bikes at the rear.

This forum seems to be full of people with opinions that cheap bikes
are;

1. Death traps
Some are, despite legislation to the contrary.

2. Unpleasant to ride
Some are.

3. uncomfortable
Some are

4. incredibly heavy
Some are.

5. have totally warped frames that you can't even fit wheels to or get
the brakes to work etc.
Some do.

6. the frames for these bikes are stored in the back of your local
bike shop
Rarely. Though the bike shop next to my parents has a skip with a pile of
such bikes in.

7. The bikes are hidden away and never used.
Unfortunately mostly true.

8. They secretly enter your bedroom at night and will kill your whole
family
Nah, they are too heavy to get up the stairs before the frames break ;-)

9. They are special magnets that will cause airliners to crash into
your house
Ones that will magnetise aluminium.. wow, call the theoretical physicists.

10. Your family and anyone that goes near one will be jinxed for the
rest of their life.
They will be. They might even take up cycling..

11. Your children will be born with terrible disfigurements and
strange growths if you even think about buying one.
Only if they are really made of Uranium.

12. God himself is telling you not to buy one as its the 11th
commandment but he forgot to mention it to moses at the time.
Didn't tell me that either.


Anyway I've sorted out a solution. I'm going to repaint the frame
yellow and paint 'Cannondale' on it instead. So now on when I mention
how much I enjoy riding my Cannondale or how good my Cannondale is it
will be accepted.

;-) Maybe Simon would have some spare sticky back Gingham^H^H^H^H^H Carbon
fibre lookalike for you?

...d

Martin Wilson wrote:

I just made the point that of the bikes I've got the cheap bike seems
very comfortable even with its greater weight. I don't see it as
vastly inferior to my Kona, Gt or Giant. Its the bike that gets most
used and abused. It goes out in all weathers and basically gets
treated lke rubbish but I really can't fault it

So why bother with the others?

This forum seems to be full of people with opinions that cheap bikes
are;

1. Death traps

Some are

2. Unpleasant to ride

All the ones I've ridden have been. I've been in considerable
discomfort after a few miles, though a lot of that would be correctable
with a decent saddle.

3. uncomfortable

Same thing as 2 in my book.

4. incredibly heavy

If "incredibly heavy" bothered me in itself I wouldn't ride a couple of
bikes that weighs 20 Kg. What is bad is excessively heavy for no good
reason. The weight on my 20 Kg bikes all comes from useful stuff that
makes the bikes better for my intended use. Things like fat steel tubes
don't do that.

7. The bikes are hidden away and never used.

Most of them are. For that matter, quite a few reasonable ones are too.
Every now and then Trail mag exhorts its readers to "dig that bike out
of the back of the garage and use it for walk ins" or similar. Why
would it suggest this sort of thing if everyone's bikes were in regular
use? Do some questioning around your friends and colleagues and see how
many have bikes, and how many use them regularly.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net http://www.dundee.ac.uk/~pjclinch/

On Thu, 24 Mar 2005 09:30:27 +0000, David Martin
wrote:

11. Your children will be born with terrible disfigurements and
strange growths if you even think about buying one.
Only if they are really made of Uranium.

The quality of saddle provided will prevent this being a problem.

On Thu, 24 Mar 2005 09:44:48 +0000, Peter Clinch
wrote:

Martin Wilson wrote:

I just made the point that of the bikes I've got the cheap bike seems
very comfortable even with its greater weight. I don't see it as
vastly inferior to my Kona, Gt or Giant. Its the bike that gets most
used and abused. It goes out in all weathers and basically gets
treated lke rubbish but I really can't fault it

So why bother with the others?


The variety of riding something different. For journeys where I don't
have to worry about leaving it vulnerable to theft. Although it has to
be said a big part was I simply wanted them.

This forum seems to be full of people with opinions that cheap bikes
are;

1. Death traps

Some are


Yes but which actual models? Normally if some item is unsafe it has a
brand and model. If you hear that a washing machine can catch fire it
might be a Candy 1100 or a tv that can catch fire it might be a
wharfedale but what actual brand and models with regards bikes are
actually unsafe. I assume its some sort of welding or material problem
with them.

Martin Wilson wrote:

Yes but which actual models? Normally if some item is unsafe it has a
brand and model.

But that isn't all there is to it. Often a cheap bike is unsafe because
it's put together by someone Without A Clue and sold on to someone who
doesn't know any better (case in point, a pal on a Halfwits Apollo MTB
where the handlebars came off after a couple of days). I could make my
/very/ expensive Streetmachine GT unsafe with some applied cluelessness,
but that wouldn't make the brand and model inherently unsafe.

I assume its some sort of welding or material problem
with them.

No, usually assembly, combined with components that don't encourage it
to go together well. Bad welds happen but are unusual. OTOH, /any/
bolt or screw can come undone if it isn't done up properly to start with.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net http://www.dundee.ac.uk/~pjclinch/