Carbonda fm936 Thoughts

[carbonazza]

...Any further word on your BSA frame order?

No. Just they will hurry the factory up...
Did you ask them for one ?

[carbonazza]

...If you mean from your experiences with gravel builds, I wouldn't compare those with XC riding where it's more likely to ruin a hanger

Against all apparences,  I've built more MTBs than other bikes 

[carbonazza]

...All home builders should invest in a hanger alignment tool...

Meanwhile you can put an Hex5 key in the hanger screw.
And counter-bend the hanger, generally a little up and/or left.
Comparing its alignement with another bike with the same dérailleur.
Or look for web pictures, on how it generally looks.

[AAJIIKOO]

Hello All,

I finally received my FM936 frame this week after ordering it at the beginning of July. There were some negative, neutral and positive surprises:

Negative:
- The seatstay definitely hits the main frame at bottom out with Fox 165x42.5mm shock. There is only 1-2mm of clearance when shock is deflated but as usual that is not enough because the frame flexes in the real riding conditions. This was confirmed when test riding the bike for the first time. I fabricated an extra 1mm steel spacer under the bottom out o-ring and shim and that was enough to prevent this from happening. But I may fabricate another 1mm spacer just to be sure...
- The trunnion width on the frame was 56mm and 54mm on the shock. I had to fabricate 1mm spacers to either side to fit the shock correctly.

Neutral:
- I ordered the frame without any special requests but I was quite surprised that the frame had BSA bottom bracket. Luckily I had totally forgot to order a new PF92 BB (I transferred all the parts from my carbon hardtail with PF92) and I could find BSA BB even from shitty local bike shops (although only Deore level but that's good enough for the time being). Some would be quite happy to have BSA over PF92 but I have never had any problems with PF92.

Positive:
- The frame looks really good.
- The shipping was by train and to my surprise I didn't have to pay any taxes.
- The geometry and handling is really good (size M, my height 174cm). It feels like a new school enduro bike but is light and efficient.

[theirishrider]

Negative:
- The seatstay definitely hits the main frame at bottom out with Fox 165x42.5mm shock. There is only 1-2mm of clearance when shock is deflated but as usual that is not enough because the frame flexes in the real riding conditions. This was confirmed when test riding the bike for the first time. I fabricated an extra 1mm steel spacer under the bottom out o-ring and shim and that was enough to prevent this from happening. But I may fabricate another 1mm spacer just to be sure...
- The trunnion width on the frame was 56mm and 54mm on the shock. I had to fabricate 1mm spacers to either side to fit the shock correctly.

Thanks for the info always good to hear. Any chance you could take a picture of your steel spacer? I'd be very curious how it looks so I can do the same if needed. Thanks.
Weird about the Trunnion width, I will fit mine today and see!

[AAJIIKOO]

Negative:
- The seatstay definitely hits the main frame at bottom out with Fox 165x42.5mm shock. There is only 1-2mm of clearance when shock is deflated but as usual that is not enough because the frame flexes in the real riding conditions. This was confirmed when test riding the bike for the first time. I fabricated an extra 1mm steel spacer under the bottom out o-ring and shim and that was enough to prevent this from happening. But I may fabricate another 1mm spacer just to be sure...
- The trunnion width on the frame was 56mm and 54mm on the shock. I had to fabricate 1mm spacers to either side to fit the shock correctly.

Thanks for the info always good to hear. Any chance you could take a picture of your steel spacer? I'd be very curious how it looks so I can do the same if needed. Thanks.
Weird about the Trunnion width, I will fit mine today and see!

The spacer is just a normal 1mm thick steel washer with an ~6mm ID and wide enough OD and I drilled it to 10mm ID. Then I cut it with an hacksaw from 1 side so I could bend it to be able to fit it on the shock shaft and then I just bent it back and closed the gap with pliers so it fits quite snugly on the 9mm shaft. It's not going anywhere since it's under the original bottom out shim. You just have to be careful not to scratch the shaft so it's a good idea to make all edges smooth. I had to do a similar procedure back in the day to a Fox DHX Air when the seatstay was hitting the main frame hard on my Mondraker even with the stock shock.

[theirishrider]

The spacer is just a normal 1mm thick steel washer with an ~6mm ID and wide enough OD and I drilled it to 10mm ID. Then I cut it with an hacksaw from 1 side so I could bend it to be able to fit it on the shock shaft and then I just bent it back and closed the gap with pliers so it fits quite snugly on the 9mm shaft. It's not going anywhere since it's under the original bottom out shim. You just have to be careful not to scratch the shaft so it's a good idea to make all edges smooth. I had to do a similar procedure back in the day to a Fox DHX Air when the seatstay was hitting the main frame hard on my Mondraker even with the stock shock.

Nice one! I'll try that before I try nylon. Thanks a million! would love to see a pic of the full build! 

[carbonazza]

The spacer is just a normal 1mm thick steel washer with an ~6mm ID and wide enough OD and I drilled it to 10mm ID. Then I cut it with an hacksaw from 1 side so I could bend it to be able to fit it on the shock shaft and then I just bent it back and closed the gap with pliers so it fits quite snugly on the 9mm shaft. It's not going anywhere since it's under the original bottom out shim. You just have to be careful not to scratch the shaft so it's a good idea to make all edges smooth. I had to do a similar procedure back in the day to a Fox DHX Air when the seatstay was hitting the main frame hard on my Mondraker even with the stock shock.

Hum... I'll guess I'll understand this better seeing it for real.
Shock shaft, and bottom out shim are alien to me.

For the BSA/PF92 story, I'm always for pressfit, except this time as the DUB spindle I have already is too big.
We've ordered 3 BSA beginning of July too. Damn! They've sent you one of ours by mistake

[numberzero]

It seems something scratched your frame and the bolt too, probably just paint.
Can you check with no pressure in your shock if you can take full travel without contact issue between rear and seattube?

This is the clearance with 42.5mm shock

I seriously don't understand how people make the frame flex so much to fill this gap?
Even if this thing was possible, the energy of the impact will be very low because it's first dissipated in the shock and then in the frame flex.

[AAJIIKOO]

It seems something scratched your frame and the bolt too, probably just paint.
Can you check with no pressure in your shock if you can take full travel without contact issue between rear and seattube?

This is the clearance with 42.5mm shock

I seriously don't understand how people make the frame flex so much to fill this gap?
Even if this thing was possible, the energy of the impact will be very low because it's first dissipated in the shock and then in the frame flex.

The gap looks much larger on your frame so maybe there is some variance in the tolerances of these frames. It didn't require much force at all to make the seatstay to hit the frame: with the shock deflated and weight on the seat just a little nudge  was enough for contact to happen. The same was happening when riding the bike with the shock pressurized: just bouncing with your weight back was enough to make audible clunk. The force is much greater in real riding conditions so I'm sure that the seatstay would have hit the main frame very hard if I haven't reduced the travel.

[Zdrenka89]

'Finished' mine for now. Had a great first ride. Everythings worked perfectecly as inteded, only had to get used to the geo. Handles great ones you get a hang of it.

I made the wheels myself but it took me two attempts regarding spoke lengths for the straight pull hubs.... bummer but they ride great in the end. ca. 1500 grams total.

I used Slapper Tape for a chainguide (only mounted in the second picture) and i can really recommend that stuff. Very flexible solution.

I use a 165x42,5mm shock and no problems so far. Frame is a L.

I might need a 60mm stem - bike feels shorter than expected so im interested as to see what it does to the handling.

Im running 170mm cranks with 25% sag and no strikes so far. (4 rides in... )

I have a BSA BB and the window to help route the Dropper cable is very small so it was a mayor pain in ass. Got it in the end though. I did use a foam liner which makes the friction higher i.e more difficult.

Haven't weighed the bike yet but frame was to spec.

Last pic is clearance of 2,35" tires on i29mm rims and a 32T Oval chainring.

Overall it feels like a GREAT purchase.
 

[zorinena]

So I have been compiling the excel for a few builds.. Just 2 for now.. will add more.. as I build mine.( this does not include mine yet ) . If anyone would like edit access to this to add their build, please let me know..

Here is the https://bit.ly/356ZHfZ
for the ones I have been able to do

[theirishrider]

Last pic is clearance of 2,35" tires on i29mm rims and a 32T Oval chainring.

Looks SO good!! Congrats!! Have you got a link to the oval rings? What dropper did you go with! Thanks

[carbonazza]

...only had to get used to the geo. Handles great ones you get a hang of it...

What is so different compared to your previous bike ?

I made the wheels myself but it took me two attempts regarding spoke lengths for the straight pull hubs.... bummer but they ride great in the end. ca. 1500 grams total.

Congrats! It is a great skill to have. You'll see how easy it will be now, to replace a spoke or true a wheel.

...I have a BSA BB...

Yet another BSA, that is comforting

Last pic is clearance of 2,35" tires on i29mm rims and a 32T Oval chainring.
Overall it feels like a GREAT purchase.

I love these tires, they roll fast, and are grippy in the mud.
Nice to see you're happy from your build!

@theirishrider, my bet it is a Garbaruk chainring

[adroitrider]

...I would order 3-4 additional hangers.
Does anyone have a link to a hanger that works for this frame?

Chasing a shifting issue. Only the two middle cogs struggle to shift down the cassette, very sluggish like the chain isn't picking up the ramps. I have been monkeying with the barrel adjuster for a few days. The encyclopedia of bike issues says this is a text book bent derailleur hanger...

Will replace and find out.

Even new hangers can be a bit out of spec and new 11/12 speed drivetrains really require a lot tighter tolerance on hanger straightness.

All home builders should invest in a hanger alignment tool, mine has paid for itself many times over already.

In fact I just had to straighten the hanger on my FM936 this past weekend after a spill and the shifting went to crap.  It looked straight to the eye, but was off quite a bit.

Ordered one. Thanks.