Cervelo carbon fork with aluminum insert questions

Discuss light weight issues concerning road bikes & parts.
thisisatest
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by thisisatest

gerardvroomen wrote:It is important that the sleeve extends below the top bearing,

although this ended up being important for the wolf SL forks, it is my current understanding that this doesn't apply to the 3t forks.
the insert is 75mm long. max stack is 40mm above the "volcano" (headset top cone), stem clamp heights tend to be around 45mm. so the insert is typically 5-10mm shy of the top cone, plus 15mm of cone equals 20-25mm from the bearing.
i remember the whole wolfSL fiasco as it was unfolding. AlphaQ, TrueTemper, disagreed with Cervelo's max stack recommendation, AlphaQ did not intend for their insert to pass to the lower bearing. Their first generation inserts, that were 100mm long and thicker, were designed to go that far. cervelo stated a lower max stack, and wanted the insert to go to the bearing. in the end, the steerer was just not very tough for reasons beyond where the insert went, as a couple failed big time, and during recall, i saw a lot of recalled forks that had the beginnings of steerer failure even with an insert.
rant over, what i'm saying is 3t has stated that the insert does not have to pass through the top bearing. it is not a design requirement.

by Weenie


Rodrego Hernandez
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Joined: Mon Oct 31, 2005 7:11 pm
Location: Out there

by Rodrego Hernandez

thisisatest wrote:
gerardvroomen wrote:It is important that the sleeve extends below the top bearing,

although this ended up being important for the wolf SL forks, it is my current understanding that this doesn't apply to the 3t forks.
the insert is 75mm long. max stack is 40mm above the "volcano" (headset top cone), stem clamp heights tend to be around 45mm. so the insert is typically 5-10mm shy of the top cone, plus 15mm of cone equals 20-25mm from the bearing.
i remember the whole wolfSL fiasco as it was unfolding. AlphaQ, TrueTemper, disagreed with Cervelo's max stack recommendation, AlphaQ did not intend for their insert to pass to the lower bearing. Their first generation inserts, that were 100mm long and thicker, were designed to go that far. cervelo stated a lower max stack, and wanted the insert to go to the bearing. in the end, the steerer was just not very tough for reasons beyond where the insert went, as a couple failed big time, and during recall, i saw a lot of recalled forks that had the beginnings of steerer failure even with an insert.
rant over, what i'm saying is 3t has stated that the insert does not have to pass through the top bearing. it is not a design requirement.



From experience I would always use the alu insert and having the bloke that designed the bike come on here and also state that makes me think that not following their instructions might be a little silly.

thisisatest
Shop Owner
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by thisisatest

he did not design the fork, although they worked with 3t on that. the 3t instructions state the measurements i quoted, to which i have to agree, and respectfully disagree with Gerard. sure, it would be BETTER, and STRONGER if the insert passed through the bearing, but it is not a design requirement. it might be stronger to fill the steerer with steel too, but i wouldn't go visit a foundry anytime soon.
and i thought Gerard was not directly involved with Cervelo anymore, anyways, and was reporting for Slowtwitch??

maquisard
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Location: France

by maquisard

I guess we should all bow to your greater judgement then since you clearly know better.

Rodrego Hernandez
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Joined: Mon Oct 31, 2005 7:11 pm
Location: Out there

by Rodrego Hernandez

Didn't 3T make the forks to their spec? Anyhoo, I'd trust the designer who probably has more insight into the design, test and performance than anyone here - no disrespect intended. He was involved with Cervelo when they moved from Easton to 3T. His hands on involvement in testing is widely documented For him to take the time out to post on here makes me think that maybe he's concerned enough about people who ride his bikes to give advice that Could save them expensive dental bills or having to buy new bar tape.

thisisatest
Shop Owner
Posts: 1980
Joined: Sat Jun 13, 2009 4:02 am
Location: NoVA/DC

by thisisatest

not to beat a dead horse, but here goes anyways...
i reread the 3t funda manual off their website. they clearly allow 40mm spacers over the "volcano" (their term), which in itself can be 15mm. their insert is stated as being 75mm. i believe the published instructions over word-of-mouth, even Gerard's.
http://www.3tcycling.com/files/Funda_ma ... _Rev00.pdf
and i'm okay with others disagreeing with me. in the end, i'd just like to know the truth.
edit: i appreciate responses like Rodrego's, even in disagreement, as it is respectful and on topic. others, not so helpful.

on the other hand, upon rereading the instructions, it seems they removed the part that stated the insert was optional. i wonder exactly when that was removed, and if it was because people were being less-than-sensible, or because of the wide variance in compression plug designs, etc.

Permon
Posts: 640
Joined: Mon Jun 23, 2008 8:52 am

by Permon

Hello guys,

I do have new R5 VWD, size 56. I assembled the bike and rode like 400km on it. The headtube area seems to me a little bit nervous, not very much stiff. I used to have an R3, 2007 model, size 58, so the lack of R5's HT area stifness surprises me...I expected stiffer HT from the R5.

So, it just came to my mind if the insert is bonded perfectly in the steerer tube or not (epoxy not fully covering the insert). If not, could it play any role in the overall stiffness of the system?
My understanding is that the insert is there to be a support for the steerer tube in cases of crash, not to be there for stifness, am I right?

FYI: I use only 5mm spacer under the stem, the bottom of the insert is deep under the upper bearings.

P.S Maybe I am too strong after winter (a lot of country skiing > my upper body is stronger so the bike seems not being stiff enough :-) )

Thank You for any inputs.

em3
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Location: NYC

by em3

Permon, if you are feeling like your front end is a bit wiggly or less stable then it is very likely that your insert is not securely bonded and is effecting your headset adjustment (bearings not properly compressed) OR your front wheel bearings or QR skewer are not correctly adjusted. Remember that the star nut insert's only purpose is to allow you to properly preload you bearings when adjusting your headset.

IME the single most important reworking of the 2011 and newer Cervelo R-series frames was the increase in front end stiffness, compared to earlier models (even when considering the slightly taller head tubes)...my point is that what you describe is not a frame design issue, but a mechanical issue.

EM3
______________

Permon
Posts: 640
Joined: Mon Jun 23, 2008 8:52 am

by Permon

em3 wrote:Permon, if you are feeling like your front end is a bit wiggly or less stable then it is very likely that your insert is not securely bonded and is effecting your headset adjustment (bearings not properly compressed) OR your front wheel bearings or QR skewer are not correctly adjusted. Remember that the star nut insert's only purpose is to allow you to properly preload you bearings when adjusting your headset.

IME the single most important reworking of the 2011 and newer Cervelo R-series frames was the increase in front end stiffness, compared to earlier models (even when considering the slightly taller head tubes)...my point is that what you describe is not a frame design issue, but a mechanical issue.

EM3


Thank You for Your opinion.
Yeah, I expected the R5 to be significantly stiffer at the HT area than the old R3 :wink: because of the re-design.
The fact is that I rode my old R3 2 months ago....so I do not have a direct comparisson with the R5.

Regarding the insert bond....the insert stays at the place, the headset does not have any play, also my Hyperons dont have any play.

So, it seems to me that problem is:
- my stronger upper body after winter :mrgreen: :beerchug: (country skiing, fitness....)
- I used to have R3, size 58....now I have R5, size 56 (due to changes in geometry - taller headtube), so the top tube and wheelbase is shorter > more twitchy handling? Maybe.

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