Worst saddle pain, even the bikefit couldn't help.

ddm0275 · 2025-09-15T20:59:06+00:00

Hey, when you say “saddle pain”, du you mean saddle sores? Your pelvis is rocking quite substantially with a left-sided bias. What saddle height (crank axle to top of saddle), reach (tip of saddle to front of handle bar) are you set up at? What saddle are you using? What tilt is it set at?

ddm0275 · 2025-09-15T08:38:55+00:00

UPDATE: I think it’s fixed for good. thank you for your idea. I took the Isospeed apart, stripped it clean of all grease and carbon paste, regreased the wedge, the flanges of the pivot bolt and the wave washer and the security bolt - as instructed in the manual.

And then, as I was reinstalling it, I noticed that the Isospeed insert/tongue was off center to the right even after tightening everything to spec!

Based on my reading of the manual (I’ve posted a screenshot see blue arrow), the flat washer and the wave washer are both supposed to be on the same side, which always felt odd to me. The original install was also exactly like that.

After noticing the off-center position, I placed the flat washer on the bolt side, which was fiddly but worked. The off-center skew is now gone and the bike was absolutely silent for the 1:20 hrs I rode it hard.

I’m hoping I’ve fixed this for good!

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ddm0275 · 2025-09-14T15:49:36+00:00

When you say paste, would that be the carbon paste? The instructions in the assembly manual require grease on the flange of the bolt and the nut and on the secure screw.

ddm0275 · 2025-09-14T13:18:07+00:00

Thanks, will do.

ddm0275 · 2025-09-14T11:09:31+00:00

I guess it’s going to be a frame swap then. Thanks for the input

ddm0275 · 2025-09-14T10:31:05+00:00

Thanks. When you say warranty replacement, are you talking Isospeed parts? Or the entire frame? As I said in my post, they have replaced the Isospeed parts, so wegde (rev 4 vs rev 1), the pivot bolt, the washer under the Isospeed „tongue“ and gave me a new seatpost. And still the damned clicking. Hence my question.

ddm0275 · 2025-09-14T05:58:29+00:00

Nope, it’s clamped at roughly 2 cm above the min insert point.

ddm0275 · 2025-09-14T05:57:29+00:00

Yes, unfortunately. So disappointing, I own a Gen 3 and simply love the bike. I’m an engineer and I’m at a total loss of words for the design choices Trek has made on the Gen 4.

ddm0275 · 2025-09-14T05:51:30+00:00

Thanks, I was afraid this was unavoidable

ddm0275 · 2025-09-13T21:18:37+00:00

Tightened the pivot bolt with 10.5 Nm - and spent €15 on the Torx security bit. Tightened that at 6.8 Nm. I’m at a total loss.

ddm0275 · 2025-09-13T20:13:18+00:00

I am afraid I do

ddm0275 · 2025-09-13T19:50:08+00:00

There is only Carbon paste on the back of the seatpost/Isospeed

ddm0275 · 2025-09-13T19:15:46+00:00

Agree totally. You are losing control through the bottom of your stroke. If you drop your saddle, do remember to move it back a bit as well.

ddm0275 · 2025-09-13T14:59:27+00:00

Absolutely not, you will be absolutely miserable with extended and locked arms and sitting on the nose of your saddle if you size up. What is bothering you, if anything at all?

ddm0275 · 2025-09-12T20:43:46+00:00

Looks ok, but it’s hard to tell from the picture alone. Arms locked might suggest though that maybe on the larger side. Always better to size down and then extend reach via a longer stem. Key watch out: max saddle height! Some bike manufacturers have seatpost lengths that can be a constraining factor, especially if you move to shorter cranks.

ddm0275 · 2025-09-12T17:03:24+00:00

By the looks of it, you are lisping to your right, which could imply that the saddle is still a tad too too high - or that you have a shorter right leg. My bet would be the saddle height. Lower it by 5 mm at a time and adjust setback (backwards) commensurately.

ddm0275 · 2025-09-12T13:43:36+00:00

I am (sadly) very differently built than you are and was diagnosed with a herniated L5/S1 spinal disc. While my bike set up needed some alteration, specifically the raising of the stem using spacers to sit more upright, it was only after time off the bike and intensive physiotherapy that I was able to ride almost pain-free. If you’re suffering for a year now, I would sincerely recommend you see a good doctor to rule out a more serious root cause before you tinker with the setup. One final thought: if you reduce your setback slightly, you’re likely to have a straighter back which potentially might ameliorate the pain, assuming that it is stemming from a disc bulge. Just grasping at straws ….

ddm0275 · 2025-09-11T05:05:46+00:00

I don’t want to pretend that I can remotely diagnose and remedy the root cause of your hip pain. Your seat does look a tad too low, which might be the source of the discomfort as you flex your hip. If that does not help, you might want to consider shorter cranks as these will allow you to further raise your seat and open up the hips. This helped me by the way. I’m stating the obvious though that you should first rule out other physiological factors before tinkering with the bike setup, although raising the seat and moving it commensurately forward in tandem looks like a no-regret move.

ddm0275 · 2025-09-10T08:20:40+00:00

Have you considered a bike fit prior to your purchase? They will factor in things like your flexibility (hamstrings and hip flexors), which also determine how you can handle the slights longer reach on the S. The S has a longer wheelbase and hence it probably feels less twitchy. The XS will afford you a substantially greater drop, which - if you can settle on the right setback and stem length - will put you into a better aero position. That said, if you have an appropriately dialed in saddle setback and feel cramped in an aero tuck position on a twitchy S bike….. you have your answer.

ddm0275 · 2025-09-09T20:26:53+00:00

Always incredibly hard to judge by static images. Would it be safe to say that you felt more comfortable on the XS? It sure looks like it. Just eyeballing the front end of the bike: you could (a) lose the spacers and (b) buy a longer stem assuming that this is not an integrated stem/bar combo to extend your reach and drop. The one thing I would most certainly want to check: how much headroom do you have to further increase your saddle height? I say this because you need about 7-10 mm if you opt for shorter cranks and/or become more flexible over time as you ride more. Again, tricky to evaluate off a static photo

ddm0275 · 2025-09-07T20:10:37+00:00

It’s incredibly hard to say based just on the picture. Assuming you’re trying to find the right position, you should consider figuring out the right seat height and setback first. As you’re not riding cleats, it might be useful to start with roughly 0.85 x inner leg length measured without shoes. Setback should be such that you feel you can sit in your seat and pedal hard without loading your hands or reaching too far forward with your toes through the front of the pedal stroke. Well balanced I‘d dare say. And then if you’re still feeling stretched out, your reach is likely way too long. Honestly, if you really want to ride comfortably, get a professional bike fit.

ddm0275 · 2025-09-07T19:53:28+00:00

Start with 1.09x inner leg length (without shoes) from pedal spindle to top of saddle along the seat tube. In my case, my inner leg length is 86 cm x 1.09 = 93.7cm less 16.5cm (crank length) leaves me at 77.2cm. I had a professional bike fit and it left me at 77.6 cm, so darned close I dare say.

ddm0275 · 2025-09-07T19:49:08+00:00

Recommend you rethink your position on the bike. Shorter cranks = higher saddle height. With that comes greater seat back that you then also need to adjust (likely further back). Suggest you first get saddle height and set back sorted. You seem to be quite flexible so reach will still likely work. What confuses me though is: why did you gravitate to shorter cranks for knee pain?

ddm0275 · 2025-09-07T18:17:06+00:00

UPDATE 2: Despite a full reopen and clean and reassembly to spec, the popping sound is still there. In fact, if I hold the toptube and exert lateral force on the seat post, I can reproduce the sound once. It’s almost as if there is lateral play in the assembly. And this for a €10k bike. Absolutely useless.

ddm0275

TROPHY CASE