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Can carbon frames be too light?

Posted: Fri Jan 04, 2013 4:48 pm
by steel515
Not fragility. Roadbikeaction said http://www.roadbikeaction.com/Bike-Test ... light.html, "While the Ultralight was at ease on the climbs, its minimal mass didn’t necessarily lend itself to fearless descending. Paying a little extra attention on descents was necessary since it’s quicker to be thrown off its line than a bike with more mass. This isn’t a geometry or design problem; it’s merely the inevitable trade-off that the new super-lightweight bikes have to make."

Can carbon frames be too light?

Posted: Fri Jan 04, 2013 4:48 pm
by Weenie

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Re: Can carbon frames be too light?

Posted: Fri Jan 04, 2013 7:08 pm
by prendrefeu
Can carbon frames be too light?


No.

I've descended on a 9lb bike. Felt just as "confident" as a 16lb bike.
It's all in the rider's confidence in their abilities.

I've also spent some time (a week and a half) doing a long-term test ride of the BH ultralite. It "felt" more stable in descending than an SL4. But, really, that's just to say that it doesn't make a difference how much the frame weighs - it's all in the confidence of the rider and the rider's ability to be connected with what they are riding.

Re: Can carbon frames be too light?

Posted: Fri Jan 04, 2013 7:10 pm
by artray
My Guru is light and is very stable going down . I think design is important and can make an impact.

Re: Can carbon frames be too light?

Posted: Fri Jan 04, 2013 7:11 pm
by Doolop
Disagree with prendrefeu

You don't get a 9lb bike without sacrificing stiffness, you simply can't.

I CAN descend fine on a flexy noodle but it sure feels better on a bike that tracks straight.

Re: Can carbon frames be too light?

Posted: Fri Jan 04, 2013 7:13 pm
by 113245
Honestly I dont think so. The bike is a small % of the rider-bike system mass. If the bike isn't built up enough and there's lots of flexing under load/handling it might not hold its line very well, so in that sense it could be too light, but if you make a 10 gram frame with the same stiffness/rigidity as a solid, beefy frame, it really shouldn't make too much of a difference IMO

Re: Can carbon frames be too light?

Posted: Fri Jan 04, 2013 7:15 pm
by prendrefeu
@dooloop
:roll:
You can.
But wheels make the majority of the difference. Stiff wheels vs. Weak wheels.
Can ultra-lite wheels be super stiff? Yes, and they have been for more than a decade now (see: Lightweights)

Can a ultra-lite frame be stiff? Yes.

Re: Can carbon frames be too light?

Posted: Fri Jan 04, 2013 7:22 pm
by Pharmstrong
Doolop wrote:Disagree with prendrefeu

You don't get a 9lb bike without sacrificing stiffness, you simply can't.


He didn't discuss 'stiffness' simply how confident the bike felt. Surely the weight of the rider is the factor in how well a frame can manage it's load, anyway?

Re: Can carbon frames be too light?

Posted: Fri Jan 04, 2013 8:09 pm
by CharlesM
steel515 wrote:Not fragility. Roadbikeaction said http://www.roadbikeaction.com/Bike-Test ... light.html" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;, "While the Ultralight was at ease on the climbs, its minimal mass didn’t necessarily lend itself to fearless descending. Paying a little extra attention on descents was necessary since it’s quicker to be thrown off its line than a bike with more mass. This isn’t a geometry or design problem; it’s merely the inevitable trade-off that the new super-lightweight bikes have to make."



I think this is bullshit.

Firstly, the BH tested wasn't "that" light. I had the same bike on test.

They had 13.6. Slap on pedals and cages and you're 14-14.5.

I think jumping to a 9 pound bike is a reach relative to the topic (and or 99% of readers)

Handling is far more about geometry, frame flex, wheel flex, fork flex, to some degree wheel weight and tire pressure in most cases.


Saying its "quicker to be thrown off line" is an overreach in most reasonable cases... Quicker to get off line than a slacked out angled 22 pound bike with 36/36 spoke, 1800 gram wheels maybe... But that doesn't mean that this bike is quick to get off line relative to the vast majority of similar bikes within a pound or 2 or 3.

The BH in the form tested is very simply NOT a bike so light that it lacks control.

I rode that bike with MADfibers and Zipp 303 tubulars and it handled pretty well. In fact it has a bit better damping than a few other frames in its weight class and that damping is going to aid control rather that make you quick to lose a line...

At days end, the review sounds like they handed a modern high end carbon bike with a reasonable 14-15pound ride ready weight to a guy not used to the class of bike...

I generally avoid poking at other reviews, but I think this one is off the mark.

I was right at home chasing down motorcycles coming off south mountain on the ULtralight... It's no place near quick to lose a line. I think the only folks that will mention the handling in the fashion the reviewer did are folks very simply not used to the direct handling and stiffness that several bikes in this class have...

http://www.pezcyclingnews.com/?pg=fullstory&id=10575

Re: Can carbon frames be too light?

Posted: Fri Jan 04, 2013 8:11 pm
by Doolop
Well I'm not going to get into an argument on the internet.

This is simply my experience with many of the lightweight bikes I have ridden. (Inversely some of the heftier bikes I have ridden also) I shouldn't make such a black and white statement, I meant generally.

Re: Can carbon frames be too light?

Posted: Fri Jan 04, 2013 8:37 pm
by CharlesM
I got ya, I just thought jumping straight to 9 pounds is an over-reach relative to the conversation. (a bike that was 14.5 at least for a ride weight)


That said, low frame weight (taken in OP context) does not always equal a bike so flexy that the handling suffers... (never mind the fact that the BH is not relatively flexy frame or fork, nor are the bars, stem and wheels used).

In fact, the RBA Reviewer compliments the stiffness of the bike... And he should.


A good example of this being overly general bullsh!t / word filler for a weak review is:::

I worked with Nick Crumpton (and the guys at Fairwheel) and helped a friend get a special bike. He wanted Light and he really wanted stable... Crumpton can Build a frame comperable to the BH in weight all day and he did. He also gave the bike a bit more friendly front end geo and extended the wheel base a little.

What we wound up with is a bike 2 pounds lighter than the BH that is the subject here at full build with GREAT stiffness and extremely stable handling relative to virtually anything on the road regardless of weight...



Forget for a second that the BH was 14.5 weight as tested, the Reviewer making a blanket statement that handling so sketchy that it requires noteworthy extra effort is due to the "inevitable trade off that the new super light bikes make" is crap for the great majority of folks hunting bikes in the BH ultralight class.

If someone is completely out of your element on a 14-15 pound bike with good stiffness (made of any material), maybe they make that statement...

Re: Can carbon frames be too light?

Posted: Fri Jan 04, 2013 11:08 pm
by bm0p700f
Reviews are often very subjective and can be nonsense. I ignore them for that reason. Go with your instinsts and if in doubt try it out.

A light bike can in principle be just as good at decending as a heavier one or better or worse. It has little to do with it's weight.

Re: Can carbon frames be too light?

Posted: Fri Jan 04, 2013 11:39 pm
by CBRE
Im sure the 900g wheels had more to due with it than the frame.

Re: Can carbon frames be too light?

Posted: Sat Jan 05, 2013 12:36 am
by dvincere
Quicker to get out of line is likely due to the vertical compliance of the bike and not weight. If you have your tires pumped up hard, and your stays (or fork) don't flex a little vertically, then every little bump will bounce you, reducing traction and bingo! tracking is off. The weight of the frame has almost nothing to do with the weight of the system. If you're a featherlight 65 kg, the bike weighs a ridiculous 5 kg and you add 300 grams to the frame, we're talking about 0.43% if you're not carrying water. Sorry bub, that's not what's affecting how the bike tracks. These numbers are probably way too extreme for the reviewer too.

Re: Can carbon frames be too light?

Posted: Sat Jan 05, 2013 1:27 am
by mellowJohnny
For the record the guy doing the test / review was Neil Shirley - so the guy knows his way around a bike. He did say that he thought slightly heavier wheels would have tracked better (moving from the RZRs on test to the RZR Team).

Edit: wrong bike test. I was thinking of the Supersix Evo Black Inc. project bike they built up for the Feb issue.

I'll show myself out now...

Re: Can carbon frames be too light?

Posted: Sat Jan 05, 2013 1:27 am
by Weenie

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Re: Can carbon frames be too light?

Posted: Sat Jan 05, 2013 3:50 am
by fdegrove
Hi,

He did say that he thought slightly heavier wheels would have tracked better (moving from the RZRs on test to the RZR Team).


If so then not because of the difference in weight but because one of the wheels just isn't stiff enough with respect to the load it's being submitted to, I suppose?

Some of these internet reviewers should be more careful about how they phrase their opinion if you'd ask me....

Ciao, ;)