Build thread: 24" Gu with shortened wheelbase

[Target]

Tough fork choice

Initially, I bought the WAW carbon disc 26" through-axle fork, and everything was fine until I installed it into the frame and measured the wheelbase. It turned out that the wheelbase with the WAW fork is 1085 mm. That's 10 mm more than with my current Rockman Carbon 24" fork!

That was totally unexpected and unpleasant. Apparently, I haven't taken into account that the WAW fork is a bit higher (405 mm) and has slightly larger offset (35 mm) than the fork I'm currently using. I'd be OK with 1075 mm WB which is long but acceptable, but 1085 mm WB is just too damn long.

While looking for alternatives, I found a 24" disc carbon fork made by Extention with the 20 mm offset and 415 mm height. This seemed interesting, because according to calculations, this fork would make the WB about 1071 mm. Plus, this fork looked beefier (and was heavier), had thicker steerer tube walls than Crewkerz, had 15 mm through axle, and was designed for 180 mm rotors (while Crewkerz made their fork for 160 mm rotors for some reasons). So I imagined the front end with this fork would be as rigid and stiff as it can be.

The only issue with Extention is that they have a steerer tube threaded inside, and a special star nut/top cap designed for internal routing. This design isn't compatible with traditional sloped stem top caps (or stems with integrated top cap like my Clean Pro), so I'll need to make an adapter for a traditional M6 top cap bolt.

[Swoofty]

The 15mm through axle is definitely a bonus. Curse Crewkerz for their 9mm proprietary B.S! That Extension fork will ruin the aesthetics of your bike I fear, but 24 pure is an exercise in poor tradeoffs. I didn't have the through axle version of the carbon WAW fork, but I ran a 203 rotor on my TMS Evo6 no problem. You can put a star nut down a threaded steerer no problem and cut it at an angle too. 

[Target]

On 7/28/2022 at 4:39 AM, Swoofty said:

That Extension fork will ruin the aesthetics of your bike I fear, but 24 pure is an exercise in poor tradeoffs.

The look of the Extention fork is controversial, especially those offset dropouts. I just told myself that it's a matter of getting used to. I remember times (mid 00's) when a trials bike without a seat looked too radical and even ugly for me.

On 7/28/2022 at 4:39 AM, Swoofty said:

You can put a star nut down a threaded steerer no problem and cut it at an angle too. 

Yeah, that's definitely possible, but I just couldn't think of ruining the inner thread with a star nut. Plus, I wanted to keep an option of internal routing open.

[Target]

Finally, the most important thing is here! Black titanium M6 bolts for the stem and black aluminium bolt for the top cap.

Now the stem looks much cleaner than with the stock silver bolts. Plus, I used shorter bolts for the clamp, so they don't stick out like the original bolts do. Plus, it always feels good to shave a few grams.

[Mark W]

12 hours ago, Target said:

Plus, I used shorter bolts for the clamp, so they don't stick out like the original bolts do.

Out of interest, was that bar clamp, steerer clamp, or both? The only reason I ask is that it looks like with the bar clamp fully closed there the bolts are close to flush with the ends of the bolts holes, but once you've got some bars in there and the clamp gap opens up you might be rolling the dice a bit with the amount of thread contact those bolts will actually get. I think there's typically more overlap with stem bolts just to ensure there's a lot of thread contact as most people really crank up the tension on them, so it's best to have a bit of extra support for them where they can.

[Target]

2 hours ago, Mark W said:

Out of interest, was that bar clamp, steerer clamp, or both? The only reason I ask is that it looks like with the bar clamp fully closed there the bolts are close to flush with the ends of the bolts holes, but once you've got some bars in there and the clamp gap opens up you might be rolling the dice a bit with the amount of thread contact those bolts will actually get. I think there's typically more overlap with stem bolts just to ensure there's a lot of thread contact as most people really crank up the tension on them, so it's best to have a bit of extra support for them where they can.

My bad, I forgot to mention that's the bar clamp. 

Clean uses 16 mm bolts for both bar and steerer clamps (for simplicity of assembling, I guess). While it's working just fine for the steerer clamp, it doesn't look ideal for the bar clamp. The bar clamp bolts are a bit too long.

On a normal bar clamp, the bolts being too long isn't a big issue. But on a Clean Pro stem, these bolts stick out dangerously towards the chest, causing risks of unpleasant feelings on front wheel moves, or even of cutting you with sharp edges of the threads.

Except of the bolts, the design of the bar clamp overall is very chest friendly.

Of course, I measured everything multiple times with different bars before I ordered those expensive bolts. And you're right, one shouldn't come to any conclusion after measuring just the stem without the bar installed.

 

[Target]

Sadly, I didn't have much time for the build recently, but here's some new custom stuff!

- An adapter to fit a sloped stem onto the Extention fork. It has M17 external thread and M6 internal thread

- Washers for the rear Jitsie hub to use it without snailcams

- Adjustment screws for Hope TZ levers. These are made longer than standard ones, so I can fit a knob on it, and I'll finally be able to adjust my levers without the allen key!

I found myself adjusting the Hope levers several times per riding, and it's so annoying to reach out for the allen key each time, so these adjusters should really make a difference.

[Target]

The front hub is here!


There are a lot of different hubs available, but I wanted to reduce spoke flex of the front wheel as much as possible. And the most annoying aspect of it is for me the one that happens between the rotor and the rim while braking. So I wanted the wheel to perform good under torsional load, that's why I've chosen a hub with the largest flange diameter available, considering not only left flange but right one as well. 

Other requirements were body material (7075), 32 holes, 15 mm through-axle.

The hub that happen to tick all the boxes is called "Progress Endurance". 58 mm flanges, and the weight is 146 g. It's not that lightweight as Tune, Extralight or Carbon-Ti, but it's still much lighter than Hope.

Edited October 9, 2022 by Target

[AdamR28]

On 10/7/2022 at 11:45 PM, Target said:

I found myself adjusting the Hope levers several times per riding, and it's so annoying to reach out for the allen key each time, so these adjusters should really make a difference.

Time for new brass barrels.

[Target]

13 hours ago, AdamR28 said:

Time for new brass barrels.

You're right, that would totally help if the levers unwind by themselves. 
But in my case, I feel a constant need to adjust and fine-tune the contact point of the levers even if they don't unwind. Sometimes the contact point must be a bit closer to the bar, sometimes it must be further away, depending on how tired my fingers are and on my mood. There must be a term for this kind of mental disorder

[AdamR28]

Haha, I see. Perhaps levers with adjustment would be sensible in this case (eg. Tech 3, Tech 4). The nylon piece in the Hope lever isn't meant to be constantly adjusted like that, the nylon piece wears out pretty quickly so the reach will constant be changing - it's likely that is the culprit, rather than your head

 

[Target]

Slowly getting there!
Installed a piece of a 1.5 mm drill bit between the bashring and the crank, so that the bashring is fixed in place and doesn't spin when the freewheel tightens up.

Removed black anodizing from the bb washers to match silver cranks

Built up the front wheel

[Target]

Cut off the buster from the frame. Initially, I had an idea to remove the hs-33 mounts with the buster completely. But it would be difficult to make the area on the seat stays look good after cutting the mounts, since I was planning to keep the frame in the original red anodized color. So I decided that just the booster would be good enough.



Angled headset installed! 

 

I'll try to use a slightly unusual chainstay protector. Made of some kind of rubber, it's here mostly to eliminate chain slap noise.

[Target]

Some tubeless stuff is getting ready.

Tubeless rim tape. Seals all the holes in the rim. Made of a TPE resistance band.


Before, I had issues with leaking air in the area between the valve and the rim tape, so this time the valve hole is made more carefully

 

Tubeless inserts (made of backer rods)


Tubeless valves. Normal tubeless valves are designed for double-wall rims, so it takes a certain amount of effort to make them compatible with a single-wall rim.

[Target]

I've tried to setup front tubeless tyre, and it didn't go well.

I've had previous experience with a tubeless setup on Hashtagg rims, and it went really smooth, haven't encountered any serious issues with it. But now I'm trying a similar setup with different rims (Neon single), and the area between the tyre and the rim leaks as crazy and just doesn't hold any air.

It looks like I didn't take into account that the profile of Neon rims is completely different from the profile of Hashtagg rims. 

The bead area of Hashtagg rims features "shoulders" on the bead shelf, very similar to ones found on some tubeless rims. That certainly helps the tyre to hold tight, and make the seal between the tyre and the rim easy to achieve.

 

The profile of Neon rims is conventional with round shelfs, and I think this is just the reason why I cannot make them work with tubeless setup.


I guess I have two options now:
1. Trying to improve Neon rims profile using some Gorilla tape. But that doesn't look easy since bead shelfs area is pretty small.
2. Forget about tubeless with Neon rims, use tubes for now, and eventually buy tubeless-friendly Light Bicycle carbon rims

[DJEHB]

I would put money on gorilla tape doing the job

[Mark W]

The hook on the top of the rim is the key one really, that's what really holds things in place. My Spank rims didn't have much of a stepped/shouldered shelf at the lower end, and it didn't really make much difference apart from it being a little harder to seat the tyre initially as the bead was binding on the rim and not popping out fully.

Gorilla tape is a good shout though! I've used that on awkward tubeless setups before and it did the trick.

[ben_travis]

Gorilla tape is definitely your best bet IMO. It'll reduce the space between the hook and the shelf and hopefully push the tire bead up into the hook creating a better seal.

Just make sure you use a rim tape or something over the holes (but im hopeful you knew that already)...

[AdamR28]

Could also fit a tube, inflate the tyre to seat both beads, then deflate it and remove the tube. With a bit of luck, that will leave you with one bead seated and only half the amount of places for air to go leaky leaky when trying to air it up tubeless.

[Target]

Appreciate all the advices, but I decided to go with tubes for now. Making a reliable tubeless setup with Neon single wall rims is too much effort.

In the meantime, here's my Jitsie Race 135 mm rear hub with custom washers. These washers are beefier than Jitsie ones and have more contact area against the dropout, and they are 3 mm longer since I won't be using snailcams.


It turned out that the inner surfaces of the left and right dropouts on my new frame are not parallel. It's so bad that you can barely rotate the hub by hands when both hub bolts are tightened! I had to file the washers of the hub at angle to compensate that.

[Target]

Because of the unparallel dropouts, I had to re-face the rear brake disc mount. It has been faced before (using Hope tool for IS mounts), but apparently due to unparallel dropouts the brake pads weren't parallel to the rotor (really badly). 

Since a dedicated tool for facing failed in my case, I decided to use a file. It took me 7 evenings to make everything square. I'm satisfied with the result, but wouldn't recommend this to anyone, it's a nightmare to do the facing manually.

I went with a method allowing me to reduce a number of variables: with only one bolt and one pad in place, I install a caliper, a wheel with a rotor, check the gap between the pad and the rotor from different points, and figure out where to file. Then I remove the caliper and the wheel, and do a really small amount of filing. Then put the wheel back. Eventually, after a lot of iterations like this, the pads become more and more parallel to the rotor. The key is not to file too much in one iteration, and be really patient. 
 

[Target]

I've faced some issues with the Clean Pro stem not holding the handlebar tight enough. Using the same torque as I do for other stems, even with the carbon adhesive paste the handlebar kept rotating forward under load.

I think I've even seen a video of Matt Pengelly supergluing(!) the bar to the Clean Pro stem, so I suspect I'm not the only one having such issues.

My solution was to add some texture to contacting surfaces of the stem and of the handlebar. I grabbed superglue and put hundreds of very small dots on the stem and the bar, let them dry out completely, and then assembled with a large amount of carbon assembly paste.

The solution seems to be working, no issues during a test ride.

Edited January 5, 2023 by Target