My Trek Domane has the worst saddle clamp ever. Anything like this will be a deal breaker for all future bikes.
My carbon rail saddle has a max torque of 8Nm but with carbon paste on the clamp-seatpost interface and grease on the bolt threads I can still tilt my saddle with relative ease. What else can I try? How much over 8Nm could I go?
I always used alloy rail saddles on it before, with the appropriate “Ears”. That stayed in place…..too well. To change the angle by a tiny bit, I’m a delicate flower, you have to smash it out of place and start all over.
Before I give up and put this saddle on a different bike, can anyone suggest anything? Is there anything better than carbon paste? I used finish line that’s probably 8 years old if that matters.
Let me verify I understand… the conical pieces that allow you to change saddle tilt are slipping/rotating? I’ve not had this problem on my domane. A bit the opposite in fact. What happens if you remove the finish line paste from the interface and run it dry?
From past experience, those clamps slip at pretty much anything less than the maximum torque (IIRC 14Nm), amd they’re a real pain in the backside to adjust, as you say. I can understand you might be reluctant to exceed the max torque value on the saddle rails.
Some of that torque will go to clamping the saddle rails between the ears, but some will disappear overcoming the friction in the conical interface between post wedges, so that 8Nm at the bolt head probably isn’t translating to 8Nm of pressure on the saddle rails.
Personally, I would gradually increase the torque 1 Nm at a time until it no longer slips, but the saddle manufacturer may not agree, and I can understand why you might be reluctant to do so, but I’ve generally found most of these conical wedge systems seem to slip unless torqued to the max.
If you’re committed to using that saddle on that bike, you could consider using the aluminium seatmast from the Emonda SL5, which has TWO BOLTS! It has a similar barrel-style bamp to set fore-aft adjustment, but the whole assembly can be rotated to adjust the angle, and set with a pinch bolt, part W541053. It’s a bit hefty though.
I was excited there for a second, the emonda seatpost is compatible! But you said mast so I think it’s a different generation?
I like the idea of gradually increasing the torque. The saddle is an AliExpress gamble that turns out to be perfect for me. At the price of it I’m willing experiment.
Exactly. I’ve always had the opposite experience as well but with alloy rails with a torque of 16Nm. There might be something to the idea of not using carbon paste. That stuff confuses me sometimes.
What year/gen is your Domane? It looks to be before the current generation (which has a different slipping issue instead), so it should use the fairly standard external mast system which was used on most Emonda, Domane and Checkpoint SL/SLR models until about MY23
In that case, apologies, ignore me. You have the current Gen4 there.
I saw the top of the post and assumed it was one of the Gen 1/Gen2 posts. I didn’t realise the Gen4 now had a different seatpost which had reverted to the old clamp style (I didn’t see that many of them due to pricing/availability issues) . I was thinking of the Gen3 post with the convenient clamp at the back (and the inconvenient quill stem-style wedge to set the saddle height). They really do make these things easy for people…
I recently had a Pro Saddle with carbon rails that says otherwise. Even if the rails are solid, one rail is deformed and delaminating. The saddle was binned last week.
What I can’t say is what torque it took to get to that, and in all likelihood the torque level to cause saddle rail failure would differ for different seatpost designs.
Do not exceed the torque setting stipulated for the seatpost clamp!
Here are some thoughts from listening to a lot of tech podcast. note I have no slipping experience as my carbon toupee has never slipped in my now very old Colnago/Giant seatpost. Please excuse my dyslexic spelling. A 8Nm greased bolt will give lower clamping force than a 8Nm dry torqued bolt as your torque wrench measures the forced to move the bolt in the thread and not the clamping force over the bolted joint. so, lubing it will give a lower clamping force. Try dry. Dave has a great article and pod on this. very recently
The carrier in the finish line acts as a lubricant according to Josh from Silca. if I recall correctly. He uses a different carrier and possible more uniform grit which clamps better. He has a youtube video on it with pictures of the grit.. Note I am a massive silca fanboy. and suffer retrograde buyers remorse when I buy silca products as I feel ripped off from the crap tools I previously bought.
Some Carbon rails are a different shape than alloy rails . meaning the teeth of the seatpost head can tilt and not be held at the correct angle to hold the saddle without slipping . if silca grip and drybolts dont work . buy an alloy rail saddle. I am a recovering weight weenies so that can be difficult.
If you have your set up dialed, you can get your saddle bonded permanently and safely to your seatpost. using carbon fiber tow and appropriate prep and bonding and adhesive from an experienced professional. Someone that has actually tested their method to validate the specific technique they are using. iirc the peeling force is critical in carbon repair epoxies and is quite a bit more expensive than “normal” SIMILAR epoxy . Well the 3m one is. Every step in bonding is critical.
Hope this helps. G
And for the most extreme option there are 1, possible 2 companies that do replacement carbon seatpost for modern bikes. They are ultra lite and ultra expensive. They cost into the hundreds if not thousands of euros
I think the opposite if I understand you correctly; there should not be carbon grip paste anywhere near the clamp. Threads should be cleaned, then greased, then re-assembled.
And then the same torque applied at the bolt will result in a tighter clamping on the saddle rails, and it might hold. Worth saying though as many others have that applying 8Nm on the clamp bolt will not necessarily apply 8Nm on the rails, so might be fine to go higher. At best that 8Nm might be applied with a normal saddle clamp @ 8Nm.
I hate single bolt clamps, I’ve only every had them slip at inopportune times like hitting a pothole, and they’re a real pain to adjust accurately.
As with the OP, I will actively avoid buying any bike frame with a proprietary seatpost shape that comes with a single bolt saddle clamp. There is zero reason for any manufacturer to use them when 2 bolt infinitely adjustable and reliable clamps have existed for 100 years.
Okay I probably should have clarified and stated within reason. 10 or maybe as high as 12 Nm (if lower wasn’t possible without slipping) would probably work.
Not ideal but if the OP real loves this AliExpress saddle it’s probably worth attempting.
Also, I hate proprietary seat posts. It’s not like the domane is a super aero bike. Couldn’t they just put a round 27.2 seat post on there?
Unless the saddle says to not exceed 8Nm WITH THAT TYPE OF SADDLE CLAMP, then their max torque statement is a “cover your ass” type of statement and practically meaningless. Single side bolt types of saddle clamps all require much higher bolt torque than the more typical vertical sandwich style clamps (such as Thomson for reference). Most of the torque on the side bolt clamps goes into the part of the cylinder below the rails, with only a portion going to actually applying a clamping force on the rails. The mating surface of the clamp pieces below the rails forms a ramp. Tightening the bolt slides the ramp downward, allowing the outer/upper clamp portions to push down/in onto the lower clamp portions which make up the cylinder.
I increased the torque a little at a time and checked if I could tilt the saddle. Just under 10Nm it felt solid so I took it off and checked the rails. They looked like new so I put it back on. When the snow is gone I’ll see how it goes outside.
10 or maybe as high as 12 Nm (if lower wasn’t possible without slipping) would probably work.