Chinertown
Chinese Carbon MTB => 29er => Topic started by: MovinMamba on April 03, 2024, 07:48:16 AM
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Hi everyone, I'm looking to build a gravel bike that might be on the verge of over biking.
I saw XC FS frames used at races like Leadville and was wondering how dumb would it be for a roadie like me to build up the same kinda bike with a drop bar? I.e Dylan Johnson style with FS (He used a hardtail xc).
I'm assuming reach issues with a 30-40mm stem could be solved to get a similar geo to most gravel bikes, so far I've been looking at the Light Carbon 918?
Considering there isn't too much information and I've been a roadie for the past 3 years, is this a really really dumb idea?
Am I missing something completely? Any advice is appreciate thank you I love you all mwah mwah
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Really the biggest issue I see using an MTB frame as the base for a gravel bike is the limited front chainring size if you try to keep the recommended chain line.
Maybe going 2x solves this?
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Sorry I'm somewhat of a mtb newbie, but why is it limiting? I mean I know the LCFS918 is listed as 36t but is this typically a bottoming out or frame issue? Ideally I could run 40t 1 by.
And if it was 2 by you mean to say that it would clear the frame better because it's offset? Do you think I could just run a single chainring then if I just yolo it and leave only the big ring on?
Appreciate your help and here is one of my Inspos :D
https://www.instagram.com/p/CxOiucSuq0s/?hl=en
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I think you main issue would be clearance on the frame rear triangle I think 38t would be possible on 918, but wouldn’t be ideal clearance wise. X2 I don’t think would work as the spacing would be terrible for chainline. You could see what a what gearing you could do with 36/38t with a non standard 12speed rear cassette to give closer higher speed ratios (Shimano make one for the old x2) but your going to be limited by the smallest cog for the highest gear. Would something like as you mention a HT mtb or maybe better the new gravel frame with a small amount of rear travel and put a front fork in.
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dengue makes a full suspension gravel frame. built around a 100/100mm travel. http://m.dengfubikes.com/index.php?s=/229.html
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Ha, I just responded to you on reddit. Here's how my old Monstercross bike started life, I did a few rides with a fork and messed around with different tires, but mostly had it set up as a 29er gravel bike https://chinertown.com/index.php/topic,2837.msg20146.html#msg20146
Chainring clearance is limited by the chainstay. MTB's have the wide tires that road bikes don't, so the chainstay flares outward where the tire is. Bigger chainring means you need to push that little bump out rearward or inward, which means either making chainstays longer or limiting tire clearance. In reality, 36t is probably the largest you'll find on a full squish. The FM199 I built from had a bunch of chainring clearance, but it's a hardtail. 36t front and 10t rear is pretty tall gearing though. Remember than 29er's are worth about 2t more speed than 700c, and 10t is 10% over 11t, so a 36/10t on 29er is similar to 42/11t on 700c. Not enough gear to win a gravel race, but more than enough for XC racing and fine for most gravel stuff. 34/10t on my MTB's is enough to get around 30mph before I spin out and tuck.
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One other thing is to look for 0° or 3° offset chainrings. I run shimano cranks and Pass Quest makes some in both variations. You could flip a 3° around so it moves outward to give you more clearance.
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Do you guys think that the chainring sizing could be overcome by going with a DUB wide bb? extra 2.5mm. Or is that something that all MTBs have standard to begin with?
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Look at the Scott HT, SP cycle has a copy and I think it allows 40T chainring
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I have briefly tested a fully mtb with a drop bar.
For me the drop bar doesn't allow to use the full potential of the bike and i always felt frustrated not to have a flat bar for more control. I lost the fun of the gravel and the ability of the MTB...
It wasn't a fun machine.
If i was to build a suspended gravel, i will go with max 50mm travel, big rolling tyres and road/gravel geometry.
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Do you guys think that the chainring sizing could be overcome by going with a DUB wide bb? extra 2.5mm. Or is that something that all MTBs have standard to begin with?
You will run into the same issue no matter how you move the chainring out and that is really poor shifting and excessive cross chaining on the low gears. I am not familiar with the DUB stuff but you will be limited by the spindle length either way. If you make the bb 2.5mm wider then the crank spindle needs to do the same. You would be better off getting a crankset to fit and using chainring offset. I think they even go up to 5 or 6mm for the cinch style ones. Am am sure the 3 bolt or 8 bolt ones are the same. This was done a lot in the fat bike world to get better chain lines.
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You should go size down, or a couple of sizes down to get a reasonable long stem. With short stem(shorter than 60mm), you will get terrible bike handling(very nervous) on a narrow dropbars.
And try to get a frame with the max chainstay length as possible. It will help with chaincross issue.
You can buy a boost cranks and/or chainrings with 0 offstet to not rub the chainstays.
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You should go size down, or a couple of sizes down to get a reasonable long stem. With short stem(shorter than 60mm), you will get terrible bike handling(very nervous) on a narrow dropbars.
I'm curious, so if I go for relatively wide bars, i.e. 440m wide drops with 550mm flare and a 60mm stem it starts getting to XC territory right? (narrow xc that is), but also the ultrawide drop bar has additional reach which flat bars don't? If I'm honest the reason I dont wanna ride flats is because ergonomically I feel much more comfortable long distances on drops than on flats
ill defo check the boost cranks!
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Wide bars will make the reach problem even worse. Have you ridden wide drops before? Personally, I'm very comfortable on 40cm gravel bars with slight flare, and 740-760mm flat bars with some backsweep. The flat bars I ride most have 11deg backsweep where most bars have more like 6-7, helps keep the wrist angle a bit more in check. 44cm drops with medium flare (Ritchey Venturemax, don't remember the flare) were very uncomfortable for me. I've ridden a bike around the parking lot with PNW bars before, maybe they were the 48cm's, and it just felt ridiculous to me. You may have a different experience though. It seems to me like you should just be on a gravel bike that takes over 50mm tires and put a gravel fork on it.
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I have ridden 420mm flared gravel bars but tbh i was more in aw of the comfort of the grx hoods…
but Yea i think the reality is setting in that im probably gonna need both a fully XC and a gravel bike … was hoping i could combine the two but here we are
n+1 afterall
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dengue makes a full suspension gravel frame. built around a 100/100mm travel. http://m.dengfubikes.com/index.php?s=/229.html
Ive been trying to get in touch with dengfu and still waiting for them to get back to me but it doesnt seem like anyone on here has built up one of these? Another thing i sorta dont like is the max tire clearance, i was hoping to fir proper mtb 2.2 inch tires
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Ive been trying to get in touch with dengfu and still waiting for them to get back to me but it doesnt seem like anyone on here has built up one of these? Another thing i sorta dont like is the max tire clearance, i was hoping to fir proper mtb 2.2 inch tires
No, I’m not aware of anyone here building one. I would definitely have taken notice.
I think I’m about to take the title for most overkill gravel build here and all I’m doing is slapping a very upright cockpit and suspension fork on a CFR707.
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I just started another thread in the gravel section about the Yishun G1055-D Adventure Gravel frame. It has 50mm rear suspension that is just a pivot the Topstone but has clearance for 700x50mm. This with a Rudy or Lauf is very intriguing to me.
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The SPCycle carbon frame I purchased a couple years ago doubles as my 2nd Gravel bike. In less than 1/2 and hour I can swap between a rigid carbon 29er fork or my Rockshox SID Ultimate, and configure either with flat bars or H bars.
When the bike is in rigid fork configuration with H bars, and I run a set of narrow width carbon wheels with 50mm low rolling resistance tires, this bike weighs less than my dedicated gravel bike. The wider 50s versus my 38s on the gravel bike, handle descents and technical terrain far better than my gravel bike. I run 1 X 12 gearing, and the only issue I have encountered is that the steps are often too big for pack riding on smooth gravel roads or asphalt.
With the higher BB clearance, I often find myself taking this bike on singletracks. It handles amazingly well versus my gravel bike on the same mtb trails I ride.
Why do you want rear suspension on a gravel type bike?
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Why do you want rear suspension on a gravel type bike?
I want to do long distances, and I'm hoping the suspension can take the edge off of the vibration fatigue, especially on washboard gravel and rooty terrain which I have where I ride.
Hard tail with front sus fork starts to look promising but considering I want maximum comfort for long distance I'm thinking a fully for washboard gravel makes most sense?
This is why I'm asking for advice because maybe I'm mislead in that regard but from what I gather sus is slower but comfier.
Realistically this will be one of many bikes I'll own so lets see how it goes
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Define long distances? 50+ miles? 100+? Multi day grinders?
What type of terrain/elevation changes are you riding?
I went through similar issues with my bikes.
1. I am getting arthritis in my hands and wrists, so washboard and washouts can be very painful on faster descents.
2. After my gravel bike was beating the heck out of me on 85 to 100 mile gravel grinders with 30+K climbing, I installed shock absorbing padding
on my bars then wrapped with bar tape. This helped a lot for general vibrations. Then I installed a PNW Coast "suspension" dropper post. This helped a bit more.
3. I still hated washboard and washouts on descents because I couldn't ride over them at speed and had to slow down too much. I thought about adding short travel suspension on the front, but changed my mind and went the 29er hardtail route based on the bike I posted pics of.
4. On the 29er, I put purchased both a carbon rigid fork, a Rockshox SID Ultimate 100mm travel fork and another PNW Coastal suspension seat post. With the rigid fork, I quickly discovered that having 50mm to 2.2 low rolling resistance tires on this bike made a lot of difference in comfort and the bike's ability to handle washboard and small washouts. This bike descends so much faster than my gravel bike, yet still climbs quickly.
5. For the 29er, with the SID on front, I found that I could start riding the bike on trails with some rock fields, roots and smaller drops. The suspension seat post sucks up a lot of the jack-hammering on the back end when you are sitting down, but I find that I am off the seat when I am riding over roots and rocks, so most of the pounding is transferred to the bars. The SID fork gobbles up almost all the roughness of washboard and washouts. With the bike set up with "H" bars it still handles well and the bike rides well for 100 mile rides. - The bike, set up with the SID and tires that handles more rocky trails adds several pounds, so it rolls and climbs slower.
6. I ride a hardtail these days for probably 70% of my off-road trail/gravel road riding. The rest is on my XC FS bike. Full suspension bikes add a lot more weight, climb slower, and to me, really aren't any more comfortable on washboard and washouts. They do shine on single-tracks with diverse terrain, but I usually only ride 30+- miles on FS bikes and I expect to get beat up and tired anyways.
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Define long distances? 50+ miles? 100+? Multi day grinders?
What type of terrain/elevation changes are you riding?
Long distance is usually around the 100 mile mark. in the saddle rolling time around 6-10 hours on the weekend per ride if it allow.
As for the terrain anything from fine gravel on long flat rolling hills to rooty single track on steep hills, (I got it all in in my area), elevation gain around 2000m or 6000ft per ride.
I actually don't mind the bike being slower up hills, I'm not after the fastest and lightest machine possible, definitely more about comfort. However I don't want to completely sacrifice handling because of weight
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Perhaps a Niner MCR RDO to split the difference? The framesets were on sale for cheap recently with option of getting it with the fork or the rear shock.
A couple people have turned the Specialized S-Works Epic World Cup in gravel bikes.... https://youtu.be/rmniD7M9j8w?si=cDlMReyhqC7hCyC2
Maybe TanTan/Seraph's FM080 http://tantancycling.com/index.php?_m=mod_product&_a=view&p_id=1118
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No, I’m not aware of anyone here building one. I would definitely have taken notice.
I think I’m about to take the title for most overkill gravel build here and all I’m doing is slapping a very upright cockpit and suspension fork on a CFR707.
Please share pictures when you can.
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I have ridden 420mm flared gravel bars but tbh i was more in aw of the comfort of the grx hoods…
but Yea i think the reality is setting in that im probably gonna need both a fully XC and a gravel bike … was hoping i could combine the two but here we are
n+1 afterall
Have I got 2 resources for you.
This is my contribution to this topic, but the post near the start from user Upcountry was what inspired my build. https://www.trainerroad.com/forum/t/drop-bar-mtb-geo/87495/167?u=kactusdog
And then, read the essays on this written by Torsten Frank. See here: https://torstenfrank.wordpress.com/2023/03/26/dropbar-mtb-teil-1-warum-gravel-immer-mehr-zu-mtb-offroad-wird-und-welches-rad-ich-mir-dafur-gebaut-habe/
Let me know what you think!
Here’s my build in progress. Size medium spcycle Epic clone running XPLR mechanical from my previous gravel bike, dub wide cranks with an AXS road 8 bolt 40t chainring (8mm offset). Flared bars, 40cm on the tops, 48mm in the drops.