New Hong Fu FM058 build

[sclyde2]

the longer event yesterday went well.  even though i am about the same weight as last year (still over 3kg above where i get to later in the year), about the same fitness, and the course was a bit tougher (exact same route, but the long last downhill was particularly eroded, and the dirt road at the end seemed to be more corrugated), i managed to slice more than 8 mins off last year (~0.8km/h faster).  yeah, i did break a chain last year which accounted for nearly 4 mins of that though.  was one place off getting into the top 5% of finishers, which is pretty good for me.

strava tells me i was a bit faster just about everywhere.  climbs, most downhills.  last year on my hardtail, i was a tiny bit faster on the flat road bits (including two sections of sealed road) and on the last downhill (which, as mentioned above, was quite treacherous this year).  the FM-058 totally destroyed the hardtail when it came to the rough stuff in the middle of the event.  especially a section with relentless rock step ups.  i quickly realised that this bike is amazing at going up that stuff.  when encountering slower traffic through these step ups, i could make my own lines around them and get up the biggest steps, probably the biggest i have ever done.  all losing minimal momentum.  i certainly could easily get used to this.

in other news, the night before the event, i noticed that there was some knocking in the rear end, when lifting and dropping the bike.  i realised that a few of the pivot bolts had come slightly loose.  i'd only ridden the bike 3 times before that.  i probably should've checked them on delivery.  i suppose that is something to look out for when buying these chinese frames.  gonna keep a close eye on those, maybe looking into putting some locktite on them.

[bournon]

How is the margin between the frame and chainring. I have little problems here with same frame. I can not use any bigger than 32T

[Klaster_1]

Only when you're off the bike and pick it up by hand you can hear a little click. I would not be concerned about yours getting worse. I've been riding mine for about a year and it has not gotten worse.

That's encouraging to hear, I was concerned with that click for a while and thought it was caused by lack of tension at rear shock binding post.

[sclyde2]

How is the margin between the frame and chainring. I have little problems here with same frame. I can not use any bigger than 32T

I don't have the bike in front of me (to measure the gap between the chainring to the frame), but I had plenty enough clearance, such that I have no concern that flex could cause contact.  I even put a 34t on, and there was still plenty of clearance.

I saw that you linked your cranks on the other thread.  CRC's SRAM stuff is geoblocked for my country, so I am not sure exactly what crank and ring that you are using.  I am not that familiar with sram 1x cranks with direct mount rings.  I did look up sram cranks and I didn't really find anything that definitive on their chainline anyway.  I could not find another image of the 11s direct mount chainrings with "blackbox" written on it like yours, so don't know what chain ring you have.

Overall, I dunno what is going on with your crank-chainring-bottombracket setup, but you are the only one I have heard of that had an issue with chainring clearance on this frame (including all the equivalents from hongfu and other suppliers).  AFAIK, these frames all come out of the same mold (for each size), so I can't see how your frame would be different from everyone elses.

It seems to me that your issue is more likely the chainline of your crank/ring.  AFAIK, just about every 3x shimano hollowtech mtb crank has a chainline of 50mm for the middle ring position.  I would suggest that you grab one of these Shimano cranks (most people I know have an old one of these either on one of their backup bikes, or sitting in a parts bin, and they usually have a 32t) and put it on to check clearance.  You might need to remove a spacer or get a different bearing to get the (gxp) 22mm side up to 24mm, so the Shimano axle fits.

[bournon]

Ok, i will try shimano M8000 and see if it works.

Now i used this:
http://www.chainreactioncycles.com/se/en/sram-pressfit-gxp-alloy-bottom-bracket/rp-prod75586
http://www.chainreactioncycles.com/se/en/sram-x01-11-speed-chainset/rp-prod122747
32T SRAM Chainring. 6mm offset for 11 speed setup. - https://www.sram.com/sram/mountain/products/sram-x-sync-direct-mount-chainrings

Should be 49mm chainline when use this setup.

[sclyde2]

Ok, i will try shimano M8000 and see if it works.

Now i used this:
http://www.chainreactioncycles.com/se/en/sram-pressfit-gxp-alloy-bottom-bracket/rp-prod75586
http://www.chainreactioncycles.com/se/en/sram-x01-11-speed-chainset/rp-prod122747
32T SRAM Chainring. 6mm offset for 11 speed setup. - https://www.sram.com/sram/mountain/products/sram-x-sync-direct-mount-chainrings

Should be 49mm chainline when use this setup.

I washed my bike yesterday, and had a closer look at the chainring clearance.  It isn't as much as I thought.  If the chain line was about 2mm less, it would be close to touching the chain stay.  How did you go with the Shimano crank?

[sclyde2]

1 year Update:

My bike turned one this week.  In total, I'm guessing I've done about 15 events on it - mostly ~70-80 minute xc events at local clubs, about four or five longer events (mostly 3-4hrs) and one 35 minute short track event.

With 2 young kids (2 and 3), I don't have much time for riding.  I get my fitness from commuting to work (around 200 of my 240hrs in 2018 were on my fm057 hardtail commuter), go in the above mentioned races, and do minimal other off road riding.  I have only ridden the fm058 in the above mentioned events, and less than 10 non race rides (such as reccy missions to pre ride race courses).  My long travel 26er has barely been ridden since I built up my fm058 - the old bike geometry feels weird now.

Log of changes since initial build:
April (2018) - Converted to tubeless.  Bike lost 108g with that conversion.
April - tune seatpost clamp.  About 30g savings
May - got same saddle and seatpost that sissypants has (well, at least back then).  The seatpost was a bit heavier than claimed, but saddle was pretty light.  The saddle is the comfiest I've ridden.  Seatpost and saddle totalled the same weight as the previous setup (within 10g).
August - Removed the zip ties on the internal cables and put in capgo noise protection.  It works.  Get it.
August - Got a light rear axle.  Robert project.  42g (saved 45g)
August - 2.25 thunder burt rear tyre.  575g (85g lighter than old tyre)
October - Got a 2nd hand fork - fox 32 factory SC non boost 46mm offset remote lockout.  Used the remote lockout off my old fork (80g including cable).  took 230-240g off the bike. 
February - Changed front tyre - 2.25 racing Ralph speed grip snakeskin (thicker sidewall than old tyre, 639g, 59g heavier than old tyre)
February - New crank with oval chainring - rotor rex 3.1 with 32t oval chainring.  Overall, 10g heavier than old crank/chainring setup.

As pictured, bike now weighs 9.81kg (ready to race, just attach number plate and Garmin and go).



Next changes:
Different coloured decals for fork.  thinking red
New front tyre - 2.25 racing ray
32t oval chainring absolute black - a bit lighter and slightly narrower chainline

The bike has been a joy to ride in races, and I have been steadily improving on it.  Other than one exception (where I had dehydration issues, that I blame on excessive pre-race coffee), I have had steady improvement in the results I am getting on this bike.  Have had a few 3rds, seconds, and finally started getting some wins starting near the end of last year.  Before all this, I never got better than 4th in these kind of races.  I can now expect to keep up with the front runners, up, down, just about everywhere.  Climbing is great, descending is great, and I seem to get a little better at cornering every time i ride it.

For a while there, the only downside of this bike for me was I was struggling a bit on the tighter uphill switchbacks.  This is probably because the reach on this bike is longer than I'd normally run, and I have a very short stem on it, making it harder to weight the front tyre in certain situations.  Lately though, it seems I am shifting my weight better and getting around them faster, and not losing ground.

I haven't touched the rear shock (think it is still around 135psi) and always run it with the compression setting fully open.  I notice no Bob, even when stomping.  Must be the high main pivot with the 32t chainring (anti squat has been discussed elsewhere on here).

While I considered that the chainring clearance was pretty good when I initially set it up with a 32t round chainring on my m980 xtr crank (50mm chainline), I ran into problems when I attempted to put an oval chainring on it.  I was determined to put a 32t oval chainring on.  The chainline for a 32t oval on my xtr crank is 48.5mm and I bought one of those chainrings, and it didn't fit (chainring hit chainstay).  After much research I ended up with a rotor 3.1 crank, the one with the 24mm axle so I didn't need to mess with the bottom  bracket.  The rotor oval ring on that had a chainline of nearly 51mm, so has plenty on clearance. The chainline is not ideal for non boost, and is a bit grindy in the big cog, so I have ordered an absolute black chainring for it, which apparently are quieter and are a mm or two further in.  Would've had much more options if I got a boost frame.

The Chinese seat post I am using has barely enough setback, especially when combined with the Chinese saddle I am using (the rails on the saddle don't allow much rearward movement).  With the setback in the post, plus with the saddle almost all the way back, and I am barely as far back as where I have been riding my commuter for the last few years. I am ecstatic with comfort of the ~$25 saddle on longer events, so much so that I have 2 spares, and recently put one on my commuter too.  There is one downside of the saddle : my shorts get stuck on it when I get behind the saddle.  I'll have to work around it.

Soon after I initially put the bike together I noticed a tiny bit of play in the rear end, when picking up the bike by the saddle.  It is very very minor, so minor that I cannot be sure where it originates.  Others have mentioned these kind of frames have play in the shock bolts.  When I initially built the bike, the top shock bolt bottomed out before it got tight, so I put a washer in there.  My measurements came up with 21.8 for the top shock mount.  Maybe I should've used a 22.2 and spread it a tiny bit.  After recently confirming that I could get 22.2 to fit, I ordered another 22.2 RWS needle bearing kit and put it on this week.  It seems to have worked, but we'll see if the play comes back after a ride.

This is my first frame with a press fit BB.  I was paranoid about creaking, so put one of those (heavy) screw together hope BBs on it.  WIthin the first month, I did detect some minor creaking, but did some research, and realised that I was putting to much pressure on the bearings, so I loosened the cranks a bit, and have pretty much forgotten about it (so it is silent).

I do have some concerns about the durability of the frame overall.  Maybe I am about paranoid, but I the play in the rear end has got my worried it had weakness in the pivots.  I have also had the headset loosen, and noticed that my headset now requires a spacer to avoid bottoming the top headset cap on the frame, suggesting something has moved - either something compressed in the top headset, or the frame's top headset cup has been pushed down.

Despite these concerns, I have no regrets getting this bike.  I am continuing to beat previous pbs on Strava segments throughout the local racetracks, and am now beating people I have never before.  Not bad for someone in their 40s.

The bike is almost too good at pedaling, which I put down to the high pivot and the inherent anti squat.  I am used to very active Horst link bikes, so I would maybe prefer a slightly more active setup.  If I was to do it again, I suppose I'd run a bigger 34t chainring (less anti squat), but then I'd probably need boost spacing to get the clearance, and probably a bigger-than-42t rear cog to get the low gear.  But I am happy with what I have, with no need to bother with a rear lockout.

[ConcreteJ]

nice bike,

I have the old fm036 the play you refer too in the back end might be what I had this was down to the mounting holes for the shock being slightly larger than needed on the linkage. I eventually cured this by using a new ti nut and bolt, whereby via complete accident the nut was drawn into the linkage recess and wedged there firmly enough to act like the hole was re-bored. Play now cured.!!!

best regards

[sclyde2]

Since the last post, i have put a racing ray tyre on the front - only 2 rides in, so far so good.  I also purchased an absolute black chainring, which promised a slightly narrow chainline, and a bit less weight - well, it turns out it was lighter, but the chainline was identical to the other rotor chainring, and the oval shape was identical, but slightly different teeth shape (a tiny bit less grindy on the bigger cogs).  The chainline on this non-boost bike is probably the worst thing about it.  good thing i very rarely use the big cog these days.

The play in the rear end got slightly better with some new hardware for the mcleod shock (back in april), where i got another slightly wider (22.2) RWS bearing kit.  but then it got worse again.  After noticing that the hardware was looser than expected (i didn't even need to press it, it just went in easily with a finger), I have been doing some research on the mcleod shock, and have discovered a few issues - 1. the hardware can be loose (can be solved by some custom-sized hardware), 2. there can be some knocking internal to the shock (which is easily fixed by someone who knows what they are doing).  either issue could result in the play i've been getting, but i'd have to send the shock away to get it fixed, and i cant be without by bike at the moment.  so, i bit the bullet, and purchased another mcleod shock, and this time went with standard bushing hardware.  received the shock & hardware last week, raced it on the weekend, and the bike is totally perfect now.  i'll look into getting the old shock fixed, but i am in no hurry.  So, in conclusion, the play was not the bike, it was the shock.

over the last few months, i have continued to improve my results in XCO-format club races and longer 3hour events.  it has been a while since i got worse than 3rd. I have been having the best time racing ever, with a few absolutely glorious finishes, often picking up some places in the closing stages of events of all kinds.  i cannot imagine a better bike for these events.  i have reached a crossroads recently, where my long-time goal, which was to get a top 3 B-grade overall series result at my local club, a goal which has more recently been upgraded to winning the series outright, is now looking like it will be realised - with 2 races to go, i'd pretty much have to DNF to lose the series now.  So, feeling a little goal-less at the moment, the motivation not so good.  need to find another goal.  Naturally, going to A grade is the next step, but it is a big one.  I'll do that next year, but A grade at my local seems to almost always feature guys who frequent world championships etc, so i certainly wouldn't be going for the win in those races.  There are a lot of other races which have age-based cats, so maybe that's a better bet.  In any case, i still have probably 5kg i could lose off me (without getting crazy thin), so there's a bit of speed to gain there.  I certainly am not motivated to upgrade anything else on the bike, as I don't think there are any changes to do that would make me any faster.

i am so much faster now than people who beat me easily last year.  I am trying to think of the reason why.  i am barely 2kg lighter than i was about a year ago (note: i am still 1kg over the healthy weight range per BMI), the bike is maybe 400g lighter (mainly due to the Fox32SC fork).  My power figures lately are pretty close to what they were this time last year - if they are higher, it wouldn't be more than 5%.  I have been riding maybe 5% more hours than last year, a lot of the extra hours are races.  I certainly feel more comfortable on the bike with the handling, and i spent a fair bit of time fine tuning the tyre pressures and suspension settings.  i did move my cleats back a few mm which has reduced the tightness in my calves, and more recently i moved the saddle forward about 8mm.  since about January or february, i have gone all in on oval chainrings (on all bikes), and i am starting to believe some of the claims (better endurance, lower HR etc), especially given how strong i have been finishing races.  I suppose all the marginal gains add up.  the bike certainly helps.  super super stoked with it.

[carbonazza]

Nice read. Thank you for posting !

I will build a full suspension in the coming months, I like the new Carbonda for the moment.
Maybe you improved your technique or confidence or both.

A friend goes much faster than me, not because of power, I get him as soon as it climbs a little.
But when it gets curvy or rough, I see him go. My guess is handling and confidence.
I improved dramatically last year after a racing week, but still lot of work to do.
At least for me, this is a non-marginal gain to get

[sclyde2]

yeah, i think the bike handling improvements have probably contributed more than i realise - after a year on this bike, i think i'm going into and through corners more smoothly, and exiting with more speed.  i also certainly am pivoting around the sharper corners (e.g. switchbacks) better than when i first started riding this bike.

i think i also underestimated my fitness improvements.  i reviewed my 2018 vs 2019 power curves, and it looks like my power is up around 7% (roughly on average, across the curve), which is more than i expected. 

in a week's time i am gonna do a threshold-type fitness test, which involves a ~30min interval up a steady fire trail climb.  i did it at the exact same time of year last year, and i do it on my powertap-equipped hardtail (my commuter reconfigured with lower gears and off road tyres), so, unless the surface is significantly different, it should be a good like-for-like comparison, to gauge if i have really improved fitness, and by how much.

[carbonazza]

...i reviewed my 2018 vs 2019 power curves, and it looks like my power is up around 7%...

Congrats... this is no small feat.
When I compare them, 2019 looks better than 2018, but never 7%
This is about going 4' faster every hour.

[sclyde2]

the numbers are in - the improvements were much more in the engine than originally thought.  the fitness test today went much better than expected.  over the exact same course (a gradual long climb), on pretty much the same bike (my hardtail commuter, converted to offroad, with a slightly different 1xoval transmission, and faster rolling rear tyre), with a very similar year of riding (maybe 10 extra hours so far this year, a few more races), i got power numbers that were a consistent 9-11% higher than last year over the targeted 5-30 minute part of the curve.  the key ~35minute segment was done over 3 minutes faster too.  was definitely attacking the steeper sections more.  though it wasnt as painful as last year, i did average 2bpm higher. 

well this explains the recent results a lot.  dunno where this improvement came from.  maybe my kids getting heavier has helped - more resistance towing them up climbs, when i do the twice-a-month trailer rides.  or maybe there's more gains in that oval chainring (for me, at least).  it is not like i have done much different, no structured 'training', just riding to work like i have been doing for years.

i still think my FM058 has helped though.

I am more motivated to do some more events after this.  will do some more mid-length 3-4 hour endurance events.  am more motivated to lose some weight too, as i am getting close to matching the really fast guys, and need to close the gap before taking the big step up.