Confidence and stability going down hill fast

AC said:

I am not sure if it is the bike or not or just a mind games thing.
The bike is a TCR and is twitchy at the best of times which is great
for flat out sprinting and moving around but gets hairy on decents
where I feel like I haven't got total control of the bike.

I think you are talking about the dreaded 'shimmy.' Various theories are
out there about what causes this (other than obvious problems like loose
wheel bearings or out of true wheels). Here's one take on the issue.

http://www.sheldonbrown.com/brandt/shimmy.html

--
..dt
1996 Diamond Back 'Expert Tg' Roadie (7spd DT shifters, favourite bike!)
2004 Trek 2300 Roadie (9spd Ultegra)
2003 DiamondBack 'Criterium' Roadie (8spd Sora, rain bike)

|
| I think you are talking about the dreaded 'shimmy.' Various theories are
| out there about what causes this (other than obvious problems like loose
| wheel bearings or out of true wheels). Here's one take on the issue.
|
| http://www.sheldonbrown.com/brandt/shimmy.html
|
|
| --
| .dt
| 1996 Diamond Back 'Expert Tg' Roadie (7spd DT shifters, favourite bike!)
| 2004 Trek 2300 Roadie (9spd Ultegra)
| 2003 DiamondBack 'Criterium' Roadie (8spd Sora, rain bike)

Alway thought the correct Australian english term was "death wobbles"...

Book said:

|
| I think you are talking about the dreaded 'shimmy.' Various theories are
| out there about what causes this (other than obvious problems like loose
| wheel bearings or out of true wheels). Here's one take on the issue.
|
| http://www.sheldonbrown.com/brandt/shimmy.html

Quoted message said:

Alway thought the correct Australian english term was "death wobbles"...

IIRR, in motor bike land they use the words, "tank slapper"

kim

"AC" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Learned cyclists,

This follows on from an earlier post about windy conditions where I
noticed somebody mentioning the Giant TCR.

For some reason I find that when going down hill at 60km + I get nervy
and apply the brakes while my peers fly down the hill.

I am not sure if it is the bike or not or just a mind games thing.
The bike is a TCR and is twitchy at the best of times which is great
for flat out sprinting and moving around but gets hairy on decents
where I feel like I haven't got total control of the bike.

Any tips on how to improve my confidence or set up or do I just need
balls the size of grapefruit and stop being a big girls blouse?

AC

I've got an '01 TCR2 and yes they are a bit nervous. Never had any problems
in windy conditions though! Descending is no problem at all if the road is
smooth but if I hit bumps with it cranked over it get unsettled. There's one
place coming down Mt Cootha in Brisbane that has a dip in the middle of the
corner and I have to slow just a bit and pick it up a little. I've got a
kuota kharma as well now and it is slightly slower steering, but I can go
through the same corner without braking and hardly notice the bump - big
difference.

But it is a confidence thing, I used to be a pretty good descender (probably
from riding motorcycles) but I seem to have lost it a bit lately. I'm not an
expert but a few things help me when I remember them:
Arms relaxed and your inside shoulder down and forward. Flap your elbows
chicken dance style to see if you're arms are relaxed enough.
Light counter steering pressure on the inside bar will make it hold a
tighter line
Push down on the outside pedal
Lean the bike a little more than your body i.e. motocross style rather than
motorcycle road racing.
The bike will go over the bumps better if your weight is evenly distributed
over the front and the back.
Don't touch the brakes they only slow you down! If you have too a bit a rear
brake can help tighten your line if you get in a little bit hot
Squared off (worn) tyres don't want to turn in initially then turn too
quickly as they roll over the edge
Look through the corners as far ahead as you can...you go where you look
Watch out for rocks, sticks,gravel, diesel, animals, walkers, cars etc

Adam

AC said:

This follows on from an earlier post about windy conditions where I
noticed somebody mentioning the Giant TCR.

I posted a while ago about a mate who got the wobbles descending
on his new TCR. He improved steadily over a few months
and seems to be fine at 70km/h or so now, which is pretty good
evidence that it's a matter of confidence and relaxation.

--
Home page: http://members.westnet.com.au/mvw

Michael Warner said:

AC said:

This follows on from an earlier post about windy conditions where I
noticed somebody mentioning the Giant TCR.

I posted a while ago about a mate who got the wobbles descending
on his new TCR. He improved steadily over a few months
and seems to be fine at 70km/h or so now, which is pretty good
evidence that it's a matter of confidence and relaxation.

Yeah the early TCRs are a twitchy frame design (with some dodgy
assembling in some cases) Their aint anything wrong with the design..
in fact they were wonderful bang for buck.. but they are twitchy.

Perfectly rideable fast down hill just not actually all that stable.
Its a confidence thing but then it allways is; its just a little more so.

The later ones are a lot better (so I am told) Some one figured that
maybe tracklike handling was actually best left to track bikes. I love
my TCR but its an aquired taste
Dave

Kathy said:

Yeah the early TCRs are a twitchy frame design (with some dodgy
assembling in some cases) Their aint anything wrong with the design..
in fact they were wonderful bang for buck.. but they are twitchy.

Perfectly rideable fast down hill just not actually all that stable.
Its a confidence thing but then it allways is; its just a little more so.

The later ones are a lot better (so I am told) Some one figured that
maybe tracklike handling was actually best left to track bikes. I love
my TCR but its an aquired taste
Dave

Just out of curiosity (and to try and myth-bust this thing so many have said about GIANTs*) are these twitchy GIANTs the models with straight forks, or raked?

*Dutch does not, nor ever has ridden a GIANT

The bike in question is the 2003 TCR1

http://www.giant-bicycle.com/au/030.000.000/030.000.000.asp?year=2003&model=9673

Straight down bladed forks. Goes fast and handles well, just likes to
move with the slightest adjustment of body.
My feeling is it is just a confidence thing. I like the idea of relax
more although it is something I need to work on (hence not relaxing!)

I will adopt a more reckless attitude from this point onwards. I have
seriously considered pedalling down the hell as the bike feels more
stable when pedaling rather than just holding on for the ride, but am
not keen yet to nudge 100km! (I wish)

AC

AC said:

The bike in question is the 2003 TCR1

http://www.giant-bicycle.com/au/030.000.000/030.000.000.asp?year=2003&model=9673

Straight down bladed forks. Goes fast and handles well, just likes to
move with the slightest adjustment of body.
My feeling is it is just a confidence thing. I like the idea of relax
more although it is something I need to work on (hence not relaxing!)

I will adopt a more reckless attitude from this point onwards. I have
seriously considered pedalling down the hell as the bike feels more
stable when pedaling rather than just holding on for the ride, but am
not keen yet to nudge 100km! (I wish)

Pedalling will make it more stable.

AC said:

The bike in question is the 2003 TCR1

giant-bicycle.com030.000.000.aspOpen ↗

Straight down bladed forks. Goes fast and handles well, just likes to
move with the slightest adjustment of body.
My feeling is it is just a confidence thing. I like the idea of relax
more although it is something I need to work on (hence not relaxing!)

I will adopt a more reckless attitude from this point onwards. I have
seriously considered pedalling down the hell as the bike feels more
stable when pedaling rather than just holding on for the ride, but am
not keen yet to nudge 100km! (I wish)

AC

Something I read somewhere... or maybe was told... was to rest your knees against the frame. It feels much more stable...

but mind you, i'm the biggest wuss descending...

cheers,
ali

There's and interesting article (letter) about speed wobbles in the current Bicycling Aust or Ride Mag (can't recall which). It talks about trail length (distance between point where tyre meets the ground and centre of top tube would meet the ground if it was that long.) I think they include a disclaimer that their's is but one theory.

Interesting also that 15 mins on this forum has also provided a useful analysis of the problem too.

Regarding earlier comments/suggestions (Adam I think) about cornering technique, I fully endorse these comments but suggest that a useful way to be confident that you are putting the right weight through the outside pedal is to try to lift your backside only slightly out of the saddle (a few millimetres). My experience is that I think I am doing ok, but then lift my b-side and find that it REALLY delivers weight where required. Before I was deceiving myself that I was putting weight through pedal.

Also concur re: confidence.

DeeDub

Kim said:

IIRR, in motor bike land they use the words, "tank slapper"

Well, in this case it would just be a 'head shake'. You don't recover from a real tankslapper, you hit the ground and hope you don't slide into something solid :eek:

In motorcycle design, the 2 factors that affect head shake are rake and trail. Trail has already been described. Rake is the angle of the forks from vertical. Steeper rake (ie. smaller angle), and/or less trail will make the bike really twitchy - rake affects this more than trail apparently. More trail gives the front wheel a self-centring effect. A bigger rake angle slows down the steering.

I can't see any reason for things to be different on a bicycle, the same laws of physics would apply.

With motorcycles, you would typically get a head shake/tankslapper exiting a corner under power with a rough road surface (though there are also other conditions under which it can happen). Many bikes will never exhibit this behaviour as the geometry (rake & trail) is such that it just won't happen. Some bikes will only do it if there isn't enough weight over the front wheel, or the suspension hasn't been setup correctly for the rider's weight and the road conditions.

The typical advice for motorcycle riders is to loose the death grip on the 'bars (ie. relax, as has already been pointed out - the chicken dance is one I've heard before too 🙂 ), and make sure your weight is distributed evenly or even a little towards the front.

Also, why aren't you pedalling on the descent? I've always loved speed, so a descent is a great place to sprint and spin out top gear 😄

"Peka" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Kim said:

IIRR, in motor bike land they use the words, "tank slapper"Well, in this
case it would just be a 'head shake'. You don't recover

from a real tankslapper, you hit the ground and hope you don't slide
into something solid :eek:

In motorcycle design, the 2 factors that affect head shake are rake and
trail. Trail has already been described. Rake is the angle of the forks
from vertical. Steeper rake (ie. smaller angle), and/or less trail will
make the bike really twitchy - rake affects this more than trail
apparently. More trail gives the front wheel a self-centring effect. A
bigger rake angle slows down the steering.

I can't see any reason for things to be different on a bicycle, the
same laws of physics would apply.

With motorcycles, you would typically get a head shake/tankslapper
exiting a corner under power with a rough road surface (though there
are also other conditions under which it can happen). Many bikes will
never exhibit this behaviour as the geometry (rake & trail) is such
that it just won't happen. Some bikes will only do it if there isn't
enough weight over the front wheel, or the suspension hasn't been setup
correctly for the rider's weight and the road conditions.

The typical advice for motorcycle riders is to loose the death grip on
the 'bars (ie. relax, as has already been pointed out - the chicken
dance is one I've heard before too 🙂 ), and make sure your weight is
distributed evenly or even a little towards the front.

Also, why aren't you pedalling on the descent? I've always loved speed,
so a descent is a great place to sprint and spin out top gear 😄

--
Peka

I belive you're right about the same basic riding theory applying, but the
rider/bike mass ratio is pretty much inverted which could screw things up.

Resound said:

....the
rider/bike mass ratio is pretty much inverted which could screw things up

Sure, but I would think the geometry would affect the bike in the same way? ie. Steeper rake and less trail on a bicycle would make it quick to turn but twitchy?

AC said:

Any tips on how to improve my confidence or set up
or do I just need balls the size of grapefruit and stop
being a big girls blouse?

You're probably just gripping the bars too tight. When you do that, you set up feedback, which can cause the wobbles at high speed. Relax, let the blood go back to your fingertips, and it'll be all so much easier.

It's a real hoot to get to the bottom, check the speedo, and see you topped 80.

Cheers,

Suzy

"AC" wrote

Quoted message said:

Learned cyclists,

This follows on from an earlier post about windy conditions where I
noticed somebody mentioning the Giant TCR.

For some reason I find that when going down hill at 60km + I get nervy
and apply the brakes while my peers fly down the hill.

I am not sure if it is the bike or not or just a mind games thing.
The bike is a TCR and is twitchy at the best of times which is great
for flat out sprinting and moving around but gets hairy on decents
where I feel like I haven't got total control of the bike.

Any tips on how to improve my confidence or set up or do I just need
balls the size of grapefruit and stop being a big girls blouse?

AC

begin combined grumble and gloat>
I wish I could go fast down hill! I used to max out at about 72kph on my
old steel bike, now on the CF TCR1 I cannot manage much more than about
68kph pedalling flat out in top gear. The price I pay for being a skinny
bugger and being able to go fast up hills?
<end combined gloat and grumble

Bruce(For the last 20 years, "oh what a surprise, I am still 65kg!"😉A

BruceA said:

.....on the CF TCR1 I cannot manage much more than about
68kph pedalling flat out in top gear

Really? What gearing does it have? I hit 65kmh on my MTB the other day and I'm sure when my fitness gets better I'll be able to beat that. My top gear is 42-11.

Peka(73kg for the last 15yrs)

Kathy said:

Perfectly rideable fast down hill just not actually all that stable.
Its a confidence thing but then it allways is; its just a little more so.

The later ones are a lot better (so I am told) Some one figured that
maybe tracklike handling was actually best left to track bikes. I love
my TCR but its an aquired taste

Mine is a large '04 - is that later, even though the back wheel is tucked
in very tight? I've never felt unstable descending at high speed, and I
like being able to drop into a corner or twitch around a pothole
instantly.

--
Home page: http://members.westnet.com.au/mvw

Bleve said:

Pedalling will make it more stable.

Does it matter whether you're still freewheeling or not?

--
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