650 vs. 700 TT bike

cycledogg said:

Hello,
I am considering doing some timetrials this season and would like to
know if there is an advantage of using 650 or 700 wheels.

Yes.

thanks,

K. Gringioni.

There's considerable debate and misunderstanding about this question. I
don't think anyone can say which is faster, purely from the standpoint of
physics. I've posed that question in all kinds of different forums. There
just isn't an answer, really. 650 wheels have an advantage in that they
accellerate more quickly which can be good. You may get more of a flywheel
effect from 700 wheels, which can be good. It all depends on the course.

Here's the real skinny on making the decision. Before integrated headsets
came about, a lot of riders would ride 650c wheels purely to achieve a
lower, more aerodynamic position on the bike. For smaller riders, it was
absolutely essential to have 650 wheels to get a truly aero position (get
your aerobars low enough to yield a flat back). Nowdays, bikes have shorter
head tubes and a lower position can be achieved with 700c wheels. Also,
smaller frames can be made in 700 and allow a low position that would only
have been possible with 650 wheels before. So you see fewer and fewer 650
bikes. Lots of folks like not having to have different size wheels for
their road bikes and TT bikes. But as you should have discerned from that,
the goal is the aerodynamic position. That's what you need to achieve.

Only when you get into really small frame sizes do you still see 650 wheels
much -- 51cm and below is what I've noticed (and I've really been shopping
for a 650 bike ... primarily 'cuz I have a huge investment in 650 wheels).

I've heard it argued that 650 wheels are not as good for longer events on
rougher road surfaces because they are stiffer than an equivalent 700 wheel
and can have a harsher ride. I couldn't say I've noticed anything like that
and I've done some 1/2 ironman distance races. Doing 112 miles (ironman
distance), maybe that would be an issue.

Last thing I'll tell you is that, in the triathlon world, some of the
fastest bike splits in days gone by were turned in on 650 wheels. However,
there's an asterisk that needs to go beside those performances because they
were turned in at a time when (as I've been told) drug suspicions were high
and drug controls were pretty much not in the picture in that sport.

Hope this helps some.

--
Bob C.

"Of course it hurts. The trick is not minding that it hurts."
T. E. Lawrence (of Arabia)
"cycledogg" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Hello,
I am considering doing some timetrials this season and would like to
know if there is an advantage of using 650 or 700 wheels. I see many
tri bikes with 650 and some TT bikes using 650. I had always thought
shorter riders tend to use the smaller wheel size but I have seen tall
riders using both.
Cheers
Rick in Tennessee

Originally, 650 bikes were used on tts because it was easier to make a
steep angled frame with the smaller wheels. this is especially so with
smaller sized frames. however, you can make steep angled frames and use
700 c wheels.

the idea of using steep angled frames for tts came from triathletes who
may not have as much flexibility as pro cyclists in their backs and
were doing 120 mile time trials. when they got of the bikes and started
running, their backs and hamstrings would be wasted. by using 78 degree
seat angles, they have a more relaxed back.

nowadays, people are using 700s tt frames with steep angles. however,
if you have good lower back and hamstring flexibility you don't need a
steep angled frame. Lance and a lot of the pros ride tts in 74 degree
seat angle bikes.

I have short hamstrings and my flexibility is not that great and prefer
a steel angled frame even for regular riding. I have a tt frame set up
as a rode bike and fits me better than a rode bike. Ultimately, there
is no advantage to 650 wheels.

Andres

Thanks, that helps clear up some questions I have been pondering.

cycledogg said:

Hello,
I am considering doing some timetrials this season and would like to
know if there is an advantage of using 650 or 700 wheels. I see many
tri bikes with 650 and some TT bikes using 650. I had always thought
shorter riders tend to use the smaller wheel size but I have seen tall
riders using both.

650 is more aerodynamic, but has higher rolling resistance. Air drag is
more important on a smooth time trial course.

Vader said:

650 is more aerodynamic, but has higher rolling resistance. Air drag is
more important on a smooth time trial course.

Marginally so, because the wheels are slightly smaller. But the
difference is minute. Another argument for 650 wheels is that they
accelerate faster. Again this is marginally so. Since you need to sit
high enough on the bike to prevent pedals from scraping the ground,
you'll ride just as high in a 650 bike as in a 700 bike. So the
aerodynamic advantages of the bike with a human are minuscle. In fact,
most people doing tts, even when attempting the hour record on a track
or in smooth courses are using 700 bikes. Most triathlets are using 700
bikes too.

Andres

Yes but remember the superbikes in the 80's? 24" fronts. Reduce the
wheel-generated resistance. That was the idea.

Of course it is all hogwash anyway. It should be equal so that it is a
race of people.

Vader said:

Yes but remember the superbikes in the 80's? 24" fronts. Reduce the
wheel-generated resistance. That was the idea.

Dumbass -

The biggest advantage of 24" fronts is that the riders in team time
trial can get their bodies closer together.

The cyclist's body has the most wind resistance of any component in the
system and the closer you can get them together, the less turbulence
you have. This effect can be easily "felt" in an echelon in a
crosswind, where the riders' bodies can be inches apart.

The 24" front wheel went out the window when 4 man TTT was no longer
contested at worlds or the Olympics.

thanks,

K. Gringioni.

Kurgan Gringioni said:

Vader said:

Yes but remember the superbikes in the 80's? 24" fronts. Reduce the
wheel-generated resistance. That was the idea.

Dumbass -

The biggest advantage of 24" fronts is that the riders in team time
trial can get their bodies closer together.

The cyclist's body has the most wind resistance of any component in the
system and the closer you can get them together, the less turbulence
you have. This effect can be easily "felt" in an echelon in a
crosswind, where the riders' bodies can be inches apart.

The 24" front wheel went out the window when 4 man TTT was no longer
contested at worlds or the Olympics.

That's the most rational and useful piece of information I hav eread
here in a month.

Thanks,

Darth

Kurgan Gringioni said:

Quoted message said:

The biggest advantage of 24" fronts is that the riders in team time
trial can get their bodies closer together.

Vader said:

That's the most rational and useful piece of information I hav eread
here in a month.

Quoted message said:

Darth

Dumbass,
With a aero helmet like yours you don't need 650 wheels.