Descending bike

Discuss light weight issues concerning road bikes & parts.
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ks_rider
Posts: 64
Joined: Sun Dec 07, 2003 8:01 pm
Location: Wichita, KS USA

by ks_rider

Superlite had the first version of Zero Gravity's and said that they did not brake that well, which means that you scrub off less speed going down and ergo, go faster. :wink:

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Ye Olde Balde One
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Joined: Sun Oct 19, 2003 4:26 pm
Location: Santa Monica, CA

by Ye Olde Balde One

benz76 wrote:I need help, please!
Yesterday I realized that I need a faster descending bike.
I'm already one of the best climebers in my category, but I loose too much when downhilling. I used to be a very fast descender, but now I feel unstable on my bike/wheels combo. I still ride a Pinarello Prince (which was considered a good descending bike), with AC Sprint 350 wheels (CX-rays) on 20mm tires.
Probably I'm as fast as I used to be, but other riders have become faster on their carbon frames (i suppose).

1.Which are good descending frames? (remember I'm a weight weenie too...)
2. Which are the best downhill wheels (lighter than my 1300gr AC, if possible)?
3. Any suggestion about tires (clincher/tubulars).

Thank you very much.

BENZ.


I found this with Veloflex Corsa tires, I changed to Pave (2mm extra width and a bigger pocket) and the problem was solved. Also having good brakes helped, I was more trusting in being able to drop speed quickly if I needed to, so I actually slowed down less and made the descent faster.
Ride lightly!

by Weenie


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Superlite
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Joined: Fri Aug 29, 2003 9:01 pm

by Superlite

Superlite had the first version of Zero Gravity's and said that they did not brake that well, which means that you scrub off less speed going down and ergo, go faster.


True, until you fly off a corner, drop 3000 feet and die a horible death and ergo, go slower!

:lol:

Someones been watching the matrix

tyson12zoll
Posts: 39
Joined: Tue Jun 08, 2004 4:32 am
Location: St. Louis, USA

by tyson12zoll

Francois_Viviers wrote:And I just pointed out that it might rather be worth just making the bike more aero as trying to put weight on the bike would have no serious benefit at all


A rider would surely benefit from a heavier rim going downhill. Not as to accelerate faster, but add in the stability of the spinning wheel.

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rico
Posts: 953
Joined: Thu Jan 01, 2004 3:49 am
Location: Kingston, the heart of UK weenie-ism

by rico

I don't think being a good descender is necessarily about being more aero. Like you I'm good uphill and terrible downhill, especially anything where the road surface is poor, there are lots of nasty corners ( :shock: ) and visibility is poor. I was not helped by a very nasty crash on a fast descent a couple of years ago.

The big guys in my club always swoop past me. In analysing why, I think much of it is about confidence. Once you get into that brake-grabby, tensed up mode, it's never going to work out. So now I try to relax as much as possible, brake later and think about how I'm going into the apex.

I know everyone will laugh at this (sigh), but buying a Colnago did help slightly. They have a shallower fork rake (71 degrees), a slightly longer wheelbase and descend in a less squirrely way than the Principia I ride before.

For all their other defects, Ksyriums are the best descending wheels I've ridden. Mavic braking surfaces tend to be good...

rico

popawheelie
Posts: 1021
Joined: Thu Sep 26, 2002 3:42 pm
Location: in Colorado

by popawheelie

How about riding a motorcycle for a while? If you take it down some of the descents you are doing on your bicycle you might get more used to the speed factor. I've heard of mountainbike downhillers riding motocross to get faster on thier bikes.

benz76
Posts: 152
Joined: Wed Jul 30, 2003 11:00 am
Location: Reggio Emilia, ITALY

by benz76

Truth is that I'm a very good downhiller: I weigh around 45 kg, and on twisty descends I'm able to brake lots of meters after other riders. And also in the very first meters of acceleration I'm faster than other riders.
But when the road becomes more straight and the downhill gets faster, I've noticed that I don't keep the pace of the 10-15 faster downhillers. And the problem is not in top speed, I loose distance when entering the corner. Other riders seem to have more stable bikes, the cut the bend and keep the bike on a straight line. I try to put my wheels on the same line, but my bike becomes unstable, and i have to (slightly) drop the speed.

My question was NOT on downhilling tecniques, but only on bike setup. I already know that downhilling is 95% rider ability and 5% bike setup...

The only thing I've noticed is that I don't keep the pace of riders I smoked on downhill one ore two years ago: is my frame that has lost some of his strenght? Are my new wheels (AC 350)? Is my tires choice?

Does anyone knows anything about Zipp 202? Expecially on braking power and overall stiffness ...

Bye, thank you very much.

Benz.

popawheelie
Posts: 1021
Joined: Thu Sep 26, 2002 3:42 pm
Location: in Colorado

by popawheelie

I still think 23's would be a better choice and not too expensive. From what the other posts say wheels would be the next thing to look at.

Racing Aardvark
Posts: 640
Joined: Thu Jan 15, 2004 1:44 am
Location: Boulder, CO

by Racing Aardvark

I can't believe noone has said this before: have you checked that there is not a problem with your wheels? :idea: Do you have a flat spot? Are they still in balance? An out of (weight) balance wheel will cause your bike to become VERY unstable at higher speeds.

I had the unpleasant discovery of a flat spot on my rear training wheel recently. You coudn't feel it until you got up around 30mph, and above 40 the bike was almost uncontrollable. I somehow put a flat spot right near the seam (between two spokes) on my Open Pro..bizarre.

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Frankie - B
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by Frankie - B

Racing Aardvark wrote:Do you have a flat spot?


Aardvark, can you suppy us with a pic of this problem? As a non native speaker i don't get the flat spot thingie... :roll:

It seems to be a very reasonable thing though.
'Tape was made to wrap your GF's gifts, NOT hold a freakin tire on.'

Racing Aardvark
Posts: 640
Joined: Thu Jan 15, 2004 1:44 am
Location: Boulder, CO

by Racing Aardvark

already tore apart the wheel, so no pic possible :(

basically, imagine taking the wheel and deforming the rim so you have a small area (no more than 1-2 cm) where the diameter is less than it should be. You could BARELY see it with your eye, but if you ran your finger over it, it was obvious. I have no idea how I did it, as I never punctured that wheel slamming it into anything.

benz76
Posts: 152
Joined: Wed Jul 30, 2003 11:00 am
Location: Reggio Emilia, ITALY

by benz76

@ racing aarkvard:

I checked both my wheels, and I found that front wheel is little unbalanced. But it's not out of center, the problem is "rotational"... When spinning very fast the rotation is not smooth as it should be: if you keep the wheels in hands you can feel the wheel "jumping" up and down. The problem is less noticeable with tire fitted on, but it still remains.

How can I get it fixed?

Thanks, Benz.

Racing Aardvark
Posts: 640
Joined: Thu Jan 15, 2004 1:44 am
Location: Boulder, CO

by Racing Aardvark

Bingo! It can be perfectly true, and be out of balance. Depending where the weight imbalance is, you can try and balance it out. IE: if the seam is the heavy point, add one of those little nuts to your valve stem. Try repositioning your computer magnet.

BTW, you can check this easily by hanging your bike on a stand and spinning the wheel up to speed. If you have really drastic oscillations start developing, you may need to fix the balance.

Supposedly back in '97, on the stage where Virenque could have taken the yellow jersey from Jan, Jan had a terrible time controlling his Boras because they were out of balance. The next day he had Bjarne's ADAs.

Beeble
Posts: 66
Joined: Sat Mar 06, 2004 7:53 pm

by Beeble

Racing Aardvark wrote:The next day he had Bjarne's ADAs.


Let's not go there :?!

bullit
Posts: 2
Joined: Sat Jun 19, 2004 7:39 pm
Location: Germany

by bullit

Racing Aardvark wrote:Bingo! It can be perfectly true, and be out of balance. Depending where the weight imbalance is, you can try and balance it out. IE: if the seam is the heavy point, add one of those little nuts to your valve stem. Try repositioning your computer magnet.

BTW, you can check this easily by hanging your bike on a stand and spinning the wheel up to speed. If you have really drastic oscillations start developing, you may need to fix the balance.

Supposedly back in '97, on the stage where Virenque could have taken the yellow jersey from Jan, Jan had a terrible time controlling his Boras because they were out of balance. The next day he had Bjarne's ADAs.



Hello,
I can remember that stage,in the evening of that day Eddy Merckx called Godefroot and gave him the advice to replace the front wheel of Ullrich´s bike.The next day Ullrich rode Heylight (later called Lightweight) and he descended better,

bullit

by Weenie


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