Fork upgrade for Cervelo P3c

Discuss light weight issues concerning road bikes & parts.
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Ruds
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Joined: Thu Jan 25, 2007 3:56 pm

by Ruds

I have a Cervelo P3c and I'm interested in upgrading the very heavy Wolf TT fork. I have weighed this fork and it is roughly 650g with a cut steerer. I was thinking about upgrading to the Wolf SL fork as it has the same profile as the TT fork but is about 330g with an uncut steerer. So the question is does anyone know of any Legal and practical TT forks which are very light :?:

footwerx
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by footwerx

Easton EC90 Aero is the logical choice.

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evenfasterson
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by evenfasterson

footwerx wrote:Easton EC90 Aero is the logical choice.


+1

Ruds
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by Ruds

But its not as light as the Wolf Sl and its also not very aerodynamic from the test reports that I have read on the internet

marcob
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by marcob

I'm planning to upgrade my PC3 with the oval jetstream A900 tt fork.
Last edited by marcob on Sun Jan 28, 2007 7:03 pm, edited 1 time in total.

Pantani
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by Pantani

I'd just doublecheck that the Wolf SL's steerer is strong enough for aerobars. Cervelo have been supplying their TT bikes with alu steerers for a long time with Alu steerers while their road bikes have been specced with carbon steerers.

PS Blackwell Research's forks are listed on their website as being pretty light.

estone2
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by estone2

marcob wrote:I'm planning to upgrade my PC3 with the oval jetstream A900 tt fork.

That would be my suggested upgrade too.
Ti rules.

Ruds
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by Ruds

I have thought about the carbon steerer strength issue on a TT bike before. But if you think that road bars go up to 46cm width and TT bars rarely go above 40cm then surly this gives less leaverage to apply force through the stem to the steerer. This coupled with the fact that you don't sprint on a TT bike would surly mean that a carbon steerer on a TT bike would see less force acting on it than on a road bike :idea: What do you guys think :?:

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evenfasterson
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by evenfasterson

Ruds wrote:I have thought about the carbon steerer strength issue on a TT bike before. But if you think that road bars go up to 46cm width and TT bars rarely go above 40cm then surly this gives less leaverage to apply force through the stem to the steerer. This coupled with the fact that you don't sprint on a TT bike would surly mean that a carbon steerer on a TT bike would see less force acting on it than on a road bike :idea: What do you guys think :?:


I agree, the road bars will have more force on them than the TT bars. You should'nt rock the top half of your body when time trialing anyway, its a waste of energy.

estone2
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by estone2

evenfasterson wrote:
Ruds wrote:I have thought about the carbon steerer strength issue on a TT bike before. But if you think that road bars go up to 46cm width and TT bars rarely go above 40cm then surly this gives less leaverage to apply force through the stem to the steerer. This coupled with the fact that you don't sprint on a TT bike would surly mean that a carbon steerer on a TT bike would see less force acting on it than on a road bike :idea: What do you guys think :?:


I agree, the road bars will have more force on them than the TT bars. You should'nt rock the top half of your body when time trialing anyway, its a waste of energy.

I don't think that's the issue that other people are wondering about. It's not lateral, it's front to back (if that's how to put it... i don't know)
You're out front on the aerobars, applying your weight on the ends of the bars (although most of it goes onto your elbows, I'd imagine).

However, there's more torque that can potentially be applied - I just looked at my aerobars (clipons) and I'd guess they're about 30cm long. if you look at the formula for torque, it's Force x Distance. On a handlebar you're looking at a clockwise torque of .21*F and a counterclockwise torque of .21*F again, where F is the force your hands are applying to the hoods or whatever. The torques cancel sort of - if I'm correct they just 'change' into a downward force - no torque on the steerer tube, no concerns.

The aerobars don't mount in the middle, so they're not .15*F, etc. Since both hands are in the same location, I'm going to use 2F (since F was the force each hand was exerting in the previous equation.).
2F*.3 ahead of the tube. There's nothing to cancel the torque, so there's forward torque (ie stress) on the steerer tube.
However, I would assume that the F in this case is minimal unless you have a poorly fit bike, as most of your weight should be going onto your elbow pads, and the torque that they can exert on the steerer tube would be minimal, since they're close to it (so it would be like F*.1 at most).

I would think it woudln't really be an issue. Any steerer that would actually crack or similarly fail would be too weak for road use too, I'd imagine.
Ti rules.

wilmar13
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by wilmar13

estone2 wrote: It's not lateral, it's front to back (if that's how to put it... i don't know) You're out front on the aerobars, applying your weight on the ends of the bars (although most of it goes onto your elbows, I'd imagine).

You are on the right track estone2... but the high loads you need to worry about on the steerer tube are when you hit a bump with your weight (significantly greater % than road bike) on the stem(via elbows)... But so what... 8) I run a 140mm stem and weigh 85kg and would still not hesitate to use carbon steerer tube. I use the standard Wolf fork, but someday will upgrade and assume whatever fork I choose (probably Blackwell) was properly designed. :wink:

estone2
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by estone2

wilmar13 wrote:
estone2 wrote: It's not lateral, it's front to back (if that's how to put it... i don't know) You're out front on the aerobars, applying your weight on the ends of the bars (although most of it goes onto your elbows, I'd imagine).

You are on the right track estone2... but the high loads you need to worry about on the steerer tube are when you hit a bump with your weight (significantly greater % than road bike) on the stem(via elbows)... But so what... 8) I run a 140mm stem and weigh 85kg and would still not hesitate to use carbon steerer tube. I use the standard Wolf fork, but someday will upgrade and assume whatever fork I choose (probably Blackwell) was properly designed. :wink:

Oi I completely forgot to factor in the stem.
However, I'd think that the stem is a factor that doesn't matter - I think the increase in front to back torque (there has to be a better term!) due to the stem can be counted out, as that same thing force is applied on a normal road bike, provided you use the same length stem.
I would doubt that hitting a bump with the weight on your elbows is any worse than hitting a bump with the weight on your hands on normal handlebars, at least for mechanical stress. For you, it could mean a crash, of course, which would be bad for your equipment, but that's a whole different venue :p
Make sure to get the legal Blackwell. They've got two forks, one of them's not UCI legal, they just made it for kicks or something. Seems like an awwfully expensive fork to put on a bike that you're not going to race, but whatever floats their boat...
-estone2
Ti rules.

wilmar13
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by wilmar13

You have a lot of weight on the stem if you are in a really aggresive TT position (for example, I have 10" drop from seat to bars)... on a road bike this is not the case at all.

The blackwell non-UCI legal fork is for age group Triathletes... I imagine at USCF TT's they would not care either... unless you have a stickler official.

estone2
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by estone2

wilmar13 wrote:You have a lot of weight on the stem if you are in a really aggresive TT position (for example, I have 10" drop from seat to bars)... on a road bike this is not the case at all.

The blackwell non-UCI legal fork is for age group Triathletes... I imagine at USCF TT's they would not care either... unless you have a stickler official.

I guess crazy people like you have to worry more :p
I don't change that much, I go from 4" to 6" or so.
Didn't remember Triathletes. Eh.
The officials around here are sticklers, for Juniors at least.
I had my freaking Trek 1200 weighed once when I was racing on it... it had Mavic Cosmic Elite wheels on it, 1900g, etc - the sucker weighed 21.5 pounds, and looked the part too, but they still insisted that I weigh in... ridiculous.
-estone2
Ti rules.

wilmar13
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by wilmar13

estone2 wrote:The officials around here are sticklers, for Juniors at least.

And the Junior gearing Nazis geesh, how are you supposed to compete in a 1/2/3 race as a Junior with a 52/14 as your biggest gear :roll:

Sorry for your luck with the new regs.

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