Knock-Block failed - Trek Rail 9.8 carbon frame damage

[GrandesRoues]

I checked on mine : 2021 carbon xl with Zeb, and the crown does touch the carbon frame... :*( by about 2mm

By the way, do you guys know if the Slash knock block 2.0 (with more range)
Part Réf. 5252160
Would fit our Rails ?

 

[Willie Los Angeles]

I checked on mine : 2021 carbon xl with Zeb, and the crown does touch the carbon frame... :*( by about 2mm

By the way, do you guys know if the Slash knock block 2.0 (with more range)
Part Réf. 5252160
Would fit our Rails ?

Slash frame design is different than the Rail. Here’s photos Slash taken when I brought my bike for service.

 

[bluewater87]

I checked on mine : 2021 carbon xl with Zeb, and the crown does touch the carbon frame... :*( by about 2mm

By the way, do you guys know if the Slash knock block 2.0 (with more range)
Part Réf. 5252160
Would fit our Rails ?

take the compression knob adjuster off the zeb and it should clear the frame.

 

[GrandesRoues]

@bluewater87 : Thanks for the tip, i just did, and it seems like it might juuusssst clear. I haven't removed my stem to properly check. At least it should do less damage.

My other question remains, do you know if the Slash knock block would work on the Rail ?
@Willie Los Angeles You have not mounted the knock block on your Slash, and i know that it clears the frame. You must have got an optionnal knock block with your bike, that have more amplitude than the one on the rail. It allows the bar to rotate a bit further. I feel limited in switchbacks, and would like to test it on my Rail if it fits.

 

[GrandesRoues]

New style (Slash 2021) ref PN 5252160 allows 72° each side

https://trek.scene7.com/is/content/TrekBicycleProducts/TK20_2021_Slash_Carbon_Alloy_USEN_Final.pdf

On the Rail the ref is PN 576232
I measured 125° range on my bike, so about 62° each side ??? (in the docs, i found a 58° quote)

 

[HeatproofGenie]

So has anyone installed the Slack-R from 9.8?

I'm strongly thinking of doing that as the direction I want my newly acquired Rail to take would benefit from it. It looks like a well thought out product.

 

[Black8917]

My 2021 Large with zeb clears the frame I removed knock block.

 

[Wak]

You crashed that's life stop trying to pass the blame of you damaging the bike get better don't crash

 

[Doomanic]

The bike has parts specifically used to stop this exact scenario. They failed to protect the bike. That's either through poor parts used, or good parts badly fitted. Neither is the OP's fault.

 

[fenwick458]

a friend crashed his bike today, same scenario the knock block failed and it's chipped the paint off the frame. its a bad design for sure, the fox 38 top cap is super sharp and angular, it just digs in to the plastic bumper and frame and chews it up causing massive damage.
Mine has a smashpot conversion so my top cap is lower and just clears, but if I were to do the same on the other side it'd likely smash the damper adjuster or damage the frame. I think I'm going to look at some sort of protection on the bottom of the downtube, it might help for a lower speed crash

 

[RustyIron]

the knock block is a bad idea and that frames/forks should simply be engineered to not have that type of interference with the fork crown.

I had never heard of a "knock block" and had to keep reading until it's function was confirmed. I can't imagine a frame designed in a way that the fork will smash into it. It's as if it was getting late on a Friday afternoon, and the designers were more interested in getting to the pub, so they just called it "good enough" and went home. I know it's good to be humble, but it's really hard when a billion dollar company makes engineering blunders that are obvious to you and me.

 

[HeatproofGenie]

I did end up buying a Rail and did end up installing a Slack R kit from 9.8. This in effect includes a spacer so it can be used to ditch the knock bloc system. I went with the 1.7 HA reduction. It's pretty slack but the Rail now is really good on steep terrain. Very much feels like a DH bike in how you must ride it. I need to get a 170mm Zeb air shaft and then I'll put the frame in high mode. Should be good.

 

[Gyre]

The bike has parts specifically used to stop this exact scenario. They failed to protect the bike. That's either through poor parts used, or good parts badly fitted. Neither is the OP's fault.

Once you commit to building a bike with insufficient clearance between single-crown fork adjusters and the down tube, the options for protecting it from falls are pretty bad. If they made the steering stop chip any stronger, a big fall would rip the chip's anchor point straight out of the carbon frame. So they design it to handle a certain amount of load and then fail before that point can occur. It's a really awful compromise IMHO.

I get that they need to fit a straight internal battery and mounting hardware, and they want to fit a water bottle mount, and they need to hit certain geometry targets, but I hope enough people will make noise and get this particular solution to go away.

 

[Madmountainman]

Purely out of interest, is it possible to mount an external bottom headset cup to the Rail? Yes, I know it'll increase the head angle, but would it then allow the fork to clear the frame?

 

[Gyre]

Purely out of interest, is it possible to mount an external bottom headset cup to the Rail? Yes, I know it'll increase the head angle, but would it then allow the fork to clear the frame?

I believe that the 9point8 SlackR does add an external cup, but it'll probably be a bigger change in head angle than you had in mind.

(Side note: Avast is warning me that the 9point8 SlackR website is infected with "CardStealer" malware at the moment, which sounds pretty ominous. I don't know if it's a false alarm or legit, so proceed with caution)

Here's a link to an NSMB review.

9point8 SLACK-R IS-Standard Angleset (nsmb.com)

Cane Creek makes +3 and +6mm crown races, so those might help push the adjuster tops away from your frame.

 

[Jamescoughlan]

I’ve fitted the Cane Creek +3 crown race and fork dials now clear the down tube.
It’s still a stupid bloody design fail. Just wish I was as good a rider as Wak clearly is.

 

[Liam9667]

I’ve had the same issue with my 21 Rail 9, luckily the damage wasn’t too severe.

Still pretty disappointing on a bike of this value. Seems like the knock block design is flawed also the rubber blocks aren’t aligned with where the fork meets the frame ?

Probably going to file down what’s left of the knock block and fit a +3 Cane Creek race.

Does anyone have a link for where you purchase this?

 

[WNH]

Bugger bugger bugger. I had a simple wash-out on a corner at Cwmcarn. Knock-block "feature" broke and the forks over rotated causing the knurled aluminium damper adjuster on the Lyrik's to scrape along the underside of the downtube.

Trek are stating it's not a warranty claim which I can't argue with but I would claim this "feature" is a design failure and the consequential damage has basically/potentially written my frame off.

The bike shop is offering me a replacement frame at cost or I look to repair the damage: thoughts and feedback welcome! Extremely upset if I'm honest; £6k bike, 200 miles in and looking at a massive bill for a basic wash-out. Not cool.

View attachment 40447

View attachment 40448

View attachment 40449

View attachment 40450

View attachment 40451

View attachment 40452

View attachment 40453

View attachment 40454

Quick question, is the Lyrik the fork the bike came stock with? I thought the 9.8's came stock with the Zeb. If indeed the bike has been "modified", that may be the reason for the claim denial. Just a thought. Also, I agree with the others, it's minor enough to be confidently repaired.

 

[Jamescoughlan]

Mine’s a mk1 Rail which came with Lyriks so completely standard.
I’ve done over 1000km of pretty hard riding since the failure and it hasn’t killed me post my minor repair. Let’s hope that’s not now tempting fate, Final Destination style!!!

 

[Gyre]

Some good news on the Knock Block front for the new 2022 frames:

 

[Peaky Rider]

The 'bumf' in the above post states "still compatible with standard stems". Presumably that's with the adaptor?

The 52 degree turning angle does not cause me any problems personally, in fact I quite like it, but can you get the new cap to up the angle to 72 degrees on the older Rails?

 

[Planemo]

So they design it to handle a certain amount of load and then fail before that point can occur. It's a really awful compromise IMHO.

I agree, but no more of a compromise than those bikes which clout the top tube with the shifter (as mine does). It's not like it's the way I have the shifter set up either - if I rotated it enough to clear, the shifter would be near impossible to use. So IMO its a design issue as the bike is stock, already runs 3 spacers under the stem and the bars are set to the highest point. So I just have to run the shifter 'nipped up' only and hope for the best in a stack. I appreciate worse things happen at sea but it will really annoy me if the tube gets dented/scratched to buggery.

 

[Mikerb]

I agree, but no more of a compromise than those bikes which clout the top tube with the shifter (as mine does). It's not like it's the way I have the shifter set up either - if I rotated it enough to clear, the shifter would be near impossible to use. So IMO its a design issue as the bike is stock, already runs 3 spacers under the stem and the bars are set to the highest point. So I just have to run the shifter 'nipped up' only and hope for the best in a stack. I appreciate worse things happen at sea but it will really annoy me if the tube gets dented/scratched to buggery.

it puts me off even considering the bike..........it needs a new frame design so nothing hits the top tube. No way I would buy a bike with knock block ( that does not even work!!).

 

[DaveW2]

Good photos of the damage. I agree with others that some carbon fibres appear to be broken. It is in an area that would have high compressive forces, so the remaining unbroken fibres might buckle during a good hit while riding. Carbon is not particularly strong in compression. I expect that someone experienced in carbon frame repair could put a patch over that to make up for the severed fibres.

 

[luna87824]

The 'bumf' in the above post states "still compatible with standard stems". Presumably that's with the adaptor?

The 52 degree turning angle does not cause me any problems personally, in fact I quite like it, but can you get the new cap to up the angle to 72 degrees on the older Rails?

"Some good news on the Knock Block" No, the good news would be....."Trek stops using knock block on all their bikes in 2022"

 

[Zorg]

Some good news on the Knock Block front for the new 2022 frames:

View attachment 78462

Anyone knows where to buy those online ?

 

[RustyMojo]

I have a knock block on my Rail. But my Zeb Ultimates are nowhere near the down tube on my large frame. I mean not even close.

 

[Gyre]

Anyone knows where to buy those online ?

Can't retrofit them on older frames, so not much reason to buy them online.

 

[Hamina]

Side note: I find this conversation very interesting as I've not faced any knock-block problems with the aluminium Rail 5.