MTB low pressure and pinch flats

On Friday, May 19, 2017 at 3:35:55 PM UTC-7, Joerg wrote:
On 2017-05-19 15:22, wrote:
On Friday, May 19, 2017 at 11:19:38 AM UTC-7, Joerg wrote:

It was the AL model just before this one:
http://www.ebay.com/itm/Trek-Superfl...AOSwax5Y1d4 X

As you can see the weight of the rider is centered.

??

The seat is almost above the rear axle. How can the rider's weight be
centered?

On steep uphill sections of trails that bike will rear up just as much
as mine.

https://www.youtube.com/watch?v=WkS8nzvqfPA

This is in German but the pics show it:

https://www.youtube.com/watch?v=MC0DhR4WfSs

Eh? The rider doesn't sit back on that sort of bike - he sits forward so that he can shift his weight to the rear for traction when necessary.

Then you have a couple of videos of people riding just as I was suggesting.

By the way - I was on a ride today and while waiting at a light a young man came pushing a high end Trek road bike across the street. I questioned him and he had a flat but didn't have a flat repair kit.

So I pulled over. He had Continental 3000 tires and after looking for a thorn or wire I showed him how to put a patch on an innertube. It looked like a real bad pinch flat. So I put the whole thing together and inflated it via CO2 whereby it immediately exploded.

On inspection the Continental 3000 had a cut sidewall just as you were saying and everyone here was criticizing. And my Gatorskins were pretty worn so I replaced them and in the process discovered several cuts in the sidewall though not large enough to render them flats waiting to occur.

So your complains about sidewall strength and cut-resistance of Continentals appear to be pretty much correct.

On Friday, May 19, 2017 at 6:42:41 PM UTC-7, Sir Ridesalot wrote:
On Friday, May 19, 2017 at 11:24:21 AM UTC-4, wrote:
On Friday, May 19, 2017 at 7:51:37 AM UTC-7, Joerg wrote:
On 2017-05-19 06:30, wrote:

When you're on a real steep off-road climb you sit. The front end is
so heavy that you can't lift them off of the ground with a low gear
so you don't have to stand.


Not really. The front coming off the ground is a common occurrence on a
MTB. There are climbs where I have to not just stand but also bend my
upper body over the handlebar so this does not happen.

Are you talking about full suspension bikes? Maybe on the latest super-light full carbon fiber bikes.

You can quite easily lift the front end on just about any bicycle if the hill is steep enough and the gear you're using is low enough. Sometimes when i tour on fire/logging/mining roads i'll pack the front end of the bike heavier than the rear just to help keep that front wheel on the ground when there are a lot of short steep climbs to make.Riding uop those hills even at a walking pace 9or slower) is LOT easire than trying to push the loaded bike up them.

That aluminum full suspension Trek I had would have taken a crane to lift the front wheel on. Low gear was REALLY low and the problem climbing wasn't that the front end was lifting but that you were going so slow that you were losing balance and control.

On 2017-05-21 15:16, wrote:
On Friday, May 19, 2017 at 3:35:55 PM UTC-7, Joerg wrote:
On 2017-05-19 15:22, wrote:
On Friday, May 19, 2017 at 11:19:38 AM UTC-7, Joerg wrote:

It was the AL model just before this one:
http://www.ebay.com/itm/Trek-Superfl...AOSwax5Y1d4 X



As you can see the weight of the rider is centered.

??

The seat is almost above the rear axle. How can the rider's weight
be centered?

On steep uphill sections of trails that bike will rear up just as
much as mine.

https://www.youtube.com/watch?v=WkS8nzvqfPA

This is in German but the pics show it:

https://www.youtube.com/watch?v=MC0DhR4WfSs

Eh? The rider doesn't sit back on that sort of bike - he sits forward
so that he can shift his weight to the rear for traction when
necessary.


Riders generally sit on the saddle most of the time :-)


Then you have a couple of videos of people riding just as I was
suggesting.


Take another look at the 2nd video. The people sit on the saddle and the
front wheels keep coming off the ground.


By the way - I was on a ride today and while waiting at a light a
young man came pushing a high end Trek road bike across the street. I
questioned him and he had a flat but didn't have a flat repair kit.

So I pulled over. He had Continental 3000 tires and after looking for
a thorn or wire I showed him how to put a patch on an innertube. It
looked like a real bad pinch flat. So I put the whole thing together
and inflated it via CO2 whereby it immediately exploded.


Whoops. Side wall aneurysm :-)


On inspection the Continental 3000 had a cut sidewall just as you
were saying and everyone here was criticizing. And my Gatorskins were
pretty worn so I replaced them and in the process discovered several
cuts in the sidewall though not large enough to render them flats
waiting to occur.

So your complains about sidewall strength and cut-resistance of
Continentals appear to be pretty much correct.


I won't buy Gatorskins anymore. I'll report back here in the NG when I
am through my first CST Conquistare. It's close to 1000mi now and
doesn't want to wear out. Its side walls look like new. At 1000mi the
Gatorskin side walls looked very worn, some threads flapping in the wind
and all.

The other main advantage is that the CST is correctly sized so went on
in minutes instead of an hour of wrestling.

Might be a while because I just shot the BB on the road bike and using
the MTB most of the time now anyhow.

--
Regards, Joerg

http://www.analogconsultants.com/

On 2017-05-21 15:20, wrote:
On Friday, May 19, 2017 at 6:42:41 PM UTC-7, Sir Ridesalot wrote:
On Friday, May 19, 2017 at 11:24:21 AM UTC-4,
wrote:
On Friday, May 19, 2017 at 7:51:37 AM UTC-7, Joerg wrote:
On 2017-05-19 06:30, wrote:

When you're on a real steep off-road climb you sit. The front
end is so heavy that you can't lift them off of the ground
with a low gear so you don't have to stand.


Not really. The front coming off the ground is a common
occurrence on a MTB. There are climbs where I have to not just
stand but also bend my upper body over the handlebar so this
does not happen.

Are you talking about full suspension bikes? Maybe on the latest
super-light full carbon fiber bikes.

You can quite easily lift the front end on just about any bicycle
if the hill is steep enough and the gear you're using is low
enough. Sometimes when i tour on fire/logging/mining roads i'll
pack the front end of the bike heavier than the rear just to help
keep that front wheel on the ground when there are a lot of short
steep climbs to make.Riding uop those hills even at a walking pace
9or slower) is LOT easire than trying to push the loaded bike up
them.

That aluminum full suspension Trek I had would have taken a crane to
lift the front wheel on.


How do you bunny-hop such a bike? A MTB that cannot be bunny-hopped with
a reasonable effort isn't very useful on a gnarlier trail. You can't
just barrel up a diagonal root because that would result in a very fast
crash.


... Low gear was REALLY low and the problem
climbing wasn't that the front end was lifting but that you were
going so slow that you were losing balance and control.


That requires training. A good MTB rider should be able to stop for
several seconds without setting down the feet and even go backwards a
little:

https://www.youtube.com/watch?v=6K04q_l6m5M

Some day I want to learn how to perform a long wheelie on an MTB but
maybe I am too old for that.

--
Regards, Joerg

http://www.analogconsultants.com/

On Monday, May 22, 2017 at 4:02:55 PM UTC-4, Joerg wrote:
On 2017-05-21 15:20, wrote:
Snipped

... Low gear was REALLY low and the problem
climbing wasn't that the front end was lifting but that you were
going so slow that you were losing balance and control.


That requires training. A good MTB rider should be able to stop for
several seconds without setting down the feet and even go backwards a
little:

Snipped
Regards, Joerg

http://www.analogconsultants.com/

On one of commuting routes home in Toronto Canada I'd take a short cut through a ravine on what was ALMOST a single track trail if it`d been a bit wider. Just before I exited the trail there was a steep climb with a 90 degree right turn at the top. There were tree roots there too. The ONLY way to be able to make that turn and continue was to come to a dead stop, jerk the front end up and around to the right so that I was now facing the right and then continue on that section. If you put a foot down at the 90 degreeturn you`d have to walk until you go to a section where you could remount and continue the ride. A lot of people got stuck there because they couldn't make the stop, turn the bike by jerking it and then get over the roots.

Cheers

On Monday, May 22, 2017 at 2:23:50 PM UTC-7, Sir Ridesalot wrote:
On Monday, May 22, 2017 at 4:02:55 PM UTC-4, Joerg wrote:
On 2017-05-21 15:20, wrote:
Snipped

... Low gear was REALLY low and the problem
climbing wasn't that the front end was lifting but that you were
going so slow that you were losing balance and control.


That requires training. A good MTB rider should be able to stop for
several seconds without setting down the feet and even go backwards a
little:

Snipped
Regards, Joerg

http://www.analogconsultants.com/

On one of commuting routes home in Toronto Canada I'd take a short cut through a ravine on what was ALMOST a single track trail if it`d been a bit wider. Just before I exited the trail there was a steep climb with a 90 degree right turn at the top. There were tree roots there too. The ONLY way to be able to make that turn and continue was to come to a dead stop, jerk the front end up and around to the right so that I was now facing the right and then continue on that section. If you put a foot down at the 90 degreeturn you`d have to walk until you go to a section where you could remount and continue the ride. A lot of people got stuck there because they couldn't make the stop, turn the bike by jerking it and then get over the roots.

There is a difference between moving along well and then having to stop for a second or two and moving near a dead stop when you have to weave back and forth to retain your balance.

I stay clipped in at many stop signs but that's not the same as climbing rough ground very slowly.