A query for the fully rigid...

silentbutdeadly

silentbutdeadly

has some good things to say
As a recent convert to fully rigid MTB I have learnt many things...mostly about myself and my softness but there's the odd few about bike handling that have been a hoot. Don't knock it if you haven't tried it!

However, I have noticed that, with the relatively low torques involved in headset caps and stem bolts, the additional vibration of the rigid forks seems to result in the stem not infrequently coming loose on the steerer sufficiently to release headset tension and make the front end very clunky.

Is this something I will just have to get used to happening on occasion or should I start using the Loctite on these bolts as well (not something I've done on any A-head stem before!)?

For clarity, the fork is a full carbon Carver (open mould Chinese); stem is a Thomson; and headset is a Chris King.
 
Calvin27

Calvin27

Eats Squid
Yep not much you can do - that's the nature of rigid forks. I didn't try Loctite, but I have noticed that some headsets are better than others. Surprisingly (or not surprisingly, depending on your personal views and grasp of physics) the traditional external headsets have been the best performers, fully integrated is the worst and semi (I have no idea but would assume) sits somewhere in the middle. This is no way a scientific test though and a thousand variables in the mix including head tube length which makes a difference too.
 
Ackland

Ackland

chats d'élevage
Loctite will not help my friend.

What compression plug are you using?

Are you using a carbon friction paste between the stem/steerer?

Do you have a torque wrench?

Do you have accurate max torque numbers for installation of the compression plug and the steerer itself?

Have you tried using a coarse sand paper to make the carbon steerer have a higher friction co-efficient?
 
silentbutdeadly

silentbutdeadly

has some good things to say
Ackland said:
Loctite will not help my friend.
Click to expand...
That was my suspicion


What compression plug are you using? One that came with the fork from Bikeman that was mooted as being for carbon steerers. The cross bike runs a Deda carbon compression plug in its Kinesis carbon fork but hasn't had the hours as yet. Do you have any particular recommendation?

Are you using a carbon friction paste between the stem/steerer? Yes

Do you have a torque wrench? Yes

Do you have accurate max torque numbers for installation of the compression plug and the steerer itself? No (assumed 4 Nm). The CK headset recommended cap preload is 1.5 Nm

Have you tried using a coarse sand paper to make the carbon steerer have a higher friction co-efficient? No
 
mitchy_

mitchy_

Llama calmer
stem caps are somewhat redundant apart from setting bearing preload, and stoping you from punching a 1 1/8" hole in your face. (or 1 1/4" if you prefer a 'giant' hole)

your stem is what is coming loose, and then that loosens the headset bearings and can wriggle the expander out.
whilst checking your stem bolts often is recommended, they shouldn't come loose often... confirm the correct torque settings, use of carbon paste (but dont smear it on like peanut butter...) and i'd use a touch of loctite on the stem steerer clamp bolts.
 
Ackland

Ackland

chats d'élevage
I'll lay out what I've done on my One9RDO w Niner RDO Fork.... I used to have the same issue (but only with this stem)

My Niner rigid came with a compression plug, I'm assuming yours is similar? Steel?

Make sure that the top of your steerer is perfectly level and that the plug sits in nice and flush.
You don't want too much excess steerer as the stem clamping area needs to overlap the compression plug.
Clean all interfaces with Isopropyl.

If you go by the Niner spec, tighten your compression plug inside the steerer to 7nM.

With an internal force (pushing outwards on the carbon) of 7nM, you can safely go up to 8nM on your stem bolts. (from Niner).

I'd initially try dry installation, no carbon paste.
If no love, I use the finish line carbon assembly paste (sparingly).
If again no love, try roughing up the clamp surface with a coarse sand paper, being careful not to alter the OD of the steerer.
Try dry.... then try with carbon paste.

If you're still getting movement..... I'm stumped.

With a Flat force stem (really low stack height and minimal clamping area) I had to do all of the above to get the stem to hold.
With an F109, I was able to install dry at 6nM on the stem bolts.
Tightening your top cap won't help as it will only start to pull your compression plug upwards and out of the steerer.

Whatever you do.... don't press in the wrong headset and then dremel out your headtube until it fits, then abuse people offering advice....
 
T-Rex

T-Rex

Template denier
SBD, slightly OT here, but.... Are you happy with that Carver fork otherwise?

If so, have you got a link for me, I'm looking for a rigid fork for my old HT, which is now a commuter.
 
slippy

slippy

Likes Bikes and Dirt
Ackland said:
If you go by the Niner spec, tighten your compression plug inside the steerer to 7nM.

With an internal force (pushing outwards on the carbon) of 7nM, you can safely go up to 8nM on your stem bolts. (from Niner).
Click to expand...
Agreed. My carbon bits say torque to 6NM, 4 doesn't sound like enough.

Apart from that, loosen the death grip and let the bike rattle around in your loose hands. Scary at first, then educational.
 
T

takai

Eats Squid
Also consider a chemical friction additive, rather than a physical one. The Motorex carbon assembly grease is what i use.
 
silentbutdeadly

silentbutdeadly

has some good things to say
Ackland said:
I'll lay out what I've done on my One9RDO w Niner RDO Fork....
Click to expand...
Cheers bloke...has given me food for thought. The setup has only come loose after the best part of a thousand kays that included a couple of races so I'm close to sorted


Ackland said:
Whatever you do.... don't press in the wrong headset and then dremel out your headtube until it fits, then abuse people offering advice....
Click to expand...
Who? Me? :pound:
 
silentbutdeadly

silentbutdeadly

has some good things to say
T-Rex said:
SBD, slightly OT here, but.... Are you happy with that Carver fork otherwise?

If so, have you got a link for me, I'm looking for a rigid fork for my old HT, which is now a commuter.
Click to expand...
Yes...absolutely. It has been a good thing http://www.bikeman.com/CARV-FKMTN29-XC480.html

Bear in mind that the On-One monocoque is cheaper (but arguably uglier) and that given it is for a commuter then it might be best to go with the Kinesis CX disc fork which is a bargain from CRC http://www.chainreactioncycles.com/au/en/kinesis-dc37-cx-disc-fork/rp-prod65378

Failing that...check out the options from Carbon Cycles in Singapore
 
mitchy_

mitchy_

Llama calmer
slippy said:
Agreed. My carbon bits say torque to 6NM, 4 doesn't sound like enough.

Apart from that, loosen the death grip and let the bike rattle around in your loose hands. Scary at first, then educational.
Click to expand...
depends on the items... carbon paste is supposed to reduce the torque required to properly grip as well.
my carbon stem says max 5Nm. it's never come loose at 4Nm on a rigid carbon fork with a smear of carbon paste applied.

T-Rex said:
Cheers for that Ackland, I didn't realise rigid forks are that pricey. A $250 fork on this old HT would be a bit like lipstick on a pig. I might need to look for a cheap steel one.
Click to expand...
if you swing the way of chinese carbon, there are ~$100 options.
 
slippy

slippy

Likes Bikes and Dirt
mitchy_ said:
depends on the items... carbon paste is supposed to reduce the torque required to properly grip as well.
my carbon stem says max 5Nm. it's never come loose at 4Nm on a rigid carbon fork with a smear of carbon paste applied.
Click to expand...
As you say, it depends on the items. In this case the OP's items ARE coming loose at 4NM with carbon paste. I'm not clear on what you're suggesting he does.

All the same, if it's only happening every 1000kms of riding I'd say just retighten every 900.
 
mitchy_

mitchy_

Llama calmer
slippy said:
As you say, it depends on the items. In this case the OP's items ARE coming loose at 4NM with carbon paste. I'm not clear on what you're suggesting he does.

All the same, if it's only happening every 1000kms of riding I'd say just retighten every 900.
Click to expand...
i'm suggesting he check his torque figures, no point suggesting 6Nm if it's not rated to it.
 
silentbutdeadly

silentbutdeadly

has some good things to say
A little further research via search engine and email turned up a figure of 6-7 Nm for the compression plug. Enve recommends 7 Nm for theirs and Carver didn't disagree with that. The plug had already been pasted so it went back in. At that torque the steerer definitely firmed up on the internal dimension of the slack Thomson stem. The top cap went down 'finger' tight (given that my torque wrench doesn't do below 3 Nm) and there was no apparent slack in the headset preload. Then the Thomson (properly pasted) was torqued up to the recommended 5.5 Nm on both bolts with no Loctite.

I'm guessing that previously the plug shifted and the compression was lost on the steerer. There is one more thing I can try and that is to place the 5mm spacer that's currently under the stem on top of the stem so that this way the plug is entirely engaged by the stem and the stem is not grabbing on the top cap instead of the fork. This is the technique recommended by ENVE for their forks.

In fact...I may do this anyway...back to the Shed!
 
Ackland

Ackland

chats d'élevage
Really you just need the top set of bolts clamping the steerer as above this, the stem doesn't have as much force....

If you were happy with the stem height before, I would leave it as it was and just try it with the higher torque
 
silentbutdeadly

silentbutdeadly

has some good things to say
Ackland said:
Really you just need the top set of bolts clamping the steerer as above this, the stem doesn't have as much force....
Click to expand...
That may have been part of the problem.

Without the 5mm spacer below the stem...the compression plug top was basically flush with the top of the stem even before preload was applied. Yes I kind of tooled up cutting the steerer length when I forgot to take into consideration the compression plug cap. So when the spacer was in place below the stem...the stem sat 5mm proud of the end of the steerer. When I went back to the Shed...I found the stem had (again) clamped onto the top cap.

Now it is the other way around, doesn't look shit and appears to be solid...lets see what another few hundred kilometres bring.
 
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