CYC X1 pro gen 4 -- 72v build -- Frame questions

[Indy1204]

Hey everyone. I'm building a bike around the cyc gen 4 with a 72v pack. I spent a couple days looking up frame styles, wheel size, geometry, talking with AI, etc., and I've come out more confused than going in. I've been riding a Giant 29 hardtail with seized up front shocks and a BBSHD, 52v pack for a few years now. I've only ridden the 29 so I can't compare against 27.5 and 26" tires. I see a lot or recommendations and builds using downhill frames for their beefiness which makes sense so I've been looking for those. I plan on riding this like a motorbike with minimal to no pedaling. Terrain will be off-road, jumps, small climbs, bmx tracks, as well as some flat riding typically for no more than a few km. I'm prioritizing low end torque over top-end speed, though I'm not sure how much difference that will really make with the motor, and it wouldn't matter for me anyway. If there is a massive difference on top-end between 26 and 29 I may reconsider, but I suspect it wouldn't be an issue.
I've searched FB marketplace and kijji for 27.5 and 29 frames as I was just thinking about what I'm used to, but there are a lot more options with 26." I've got as few questions if you don't mind.

• Am I on the right track with the downhill style frame? Would anything else be suitable?
• Any particular frame anyone has had success with?
• Considering I won't be pedaling, how much does tire size matter for the style of riding I've described above?
• I'm 5'11". Will a 26 medium/large frame feel too small? I think riding position would be more important, but I've never been on a DH bike.
• So I'm talking to some AI about this and I mention one of the spots I ride has a lot or roots on the trail and its telling me that a 29" tire will roll over it easier which makes sense. But these root only stick out a couple inches at most. Is there that much of a difference between tire size on something that size? I've been riding around on a hardtail with seized front shocks so I feel that a bike with dual suspension and a lot of travel will feel very, very different.
• I've been eyeing that CYC Heavy-Duty draintrain as I've been reading above people shredding the stock cassettes. Anyone try this out? Any alternatives to this?

Thanks for reading

 

[scianiac]

I think you are the right track with that type of terrain, yes the larger wheels are slightly better but honestly not a ton and there are some major disadvantages. Like for instance you can get 26 DH bikes for cheap all day long but 27.5/29 you are talking about a bit more. While I would probably build a future bike on 27.5 I think I would do it mostly for the tire options and even that is mostly because I'm a tire nerd. I would absolutely rather have 26in with serious suspension than 29 hardtail or XC suspension. In fact my first build was on a 29er with 100mm/100mm suspension and not even comparable to my current bike with 26in wheels and 200/254mm suspension. 26in wheels or not it absolutely eats anything in front of it. Also remember that a lot of the reason for larger wheels is for rolling resistance, that rollover can mean better rolling which is important when you don't have a motor.

Frame wise an enduro or trail bike of good quality will also work well but weirdly these can be just as expensive. DH bikes are all about hype and so they devalue quickly and in most areas there are limited placed to use them so people buy them and hardly ever ride them in most areas, then decided to sell them.

You want something that will of course fit the motor in front of the BB well but that's not hard especially with slightly older bikes. The real trick is where you put the battery, if you are building they battery then you can just build it to fit around the frame but there are limited options or ways to mount medium to large size batteries to most full suspension frames.

Size wise I you absolutely want near the correct size, you can tweak things slightly but if it's the wrong size it won't be comfortable regardless if you are pedaling. Now the size is somewhat less critical than if you were pedaling. Also when looking at older bikes, they were quite a bit smaller. I'm 5'4" and I have two converted DH bikes from around 2010-2011 and they are both size medium while being probably slightly smaller than a modern size small that would fit me.

Motor and drivetrain wise personally if I were to do it again I would stick with my choice and go with an LR Small Block over a CYC X1. I was really set on the X1 for awhile but I like the advantages the LR kit has and don't like the disadvantages of the CYC. Either way the driveline does depend on how you are using it, if you are staying in a narrow range of speeds, like say 0-20 even 0-30 single speed is the way to go. The motor at high voltage has enough go so gears are pointless, added complexity, less reliable, more unsprung mass, more delicate to being ripped off by a rock, etc, etc. Like I have my bike geared for a top speed of like 20 and basically never go that fast (although due to the motor type and field weakening I've been up to 45 on that same gearing just to see) and I have honeslty more torque than I can use. Like I have the phase amps turned down to the point where it won't power wheelie uncontrolably at my relatively low weight.

 

[Indy1204]

Thanks for the reply. I just found a Devinci from I'm guessing between 2008-2010. Its either a Franktik or Hecktik. 26" tires. Looks in great shape. Doesn't have much space for a battery except along the bottom side of the frame. I'm having a custom battery built so I might be able to get away with something there. You think this frame would hold up?

P.S. What bike do you have that motor on in the profile pic?

Thanks

 

[scianiac]

Yeah I think Frantik looks nice, the bike in my bio is a Santa Cruz V10.3 (around 2007-2010) which makes the Frantik look absolutely spacious battery wise. Remember of course batteries under down tube have to still clear the wheel at max suspension travel. The trick with batteries on these bikes is if you don't want to make some crazy divided battery pack like I did is to just put them low on the downtube, right above the motor, extending up the downtube but getting thinner for clearance, so fat at the bottom thin at the top. Then if you need more battery see if you can make it wider, nobody ever considered the width, you can actually make a pretty wide battery before in interfears with anything. Keeps the weight low, the other trick is figuring out how much battery you actually need, don't try and put a massive battery that you'll never use.

Ah there is one more thing I forgot to mention, this one is kinda complicated and not super important but can be annoying. Chain growth, a frame with a ton of chain growth can be kind of annoying now and then depending how you set the motor up. This may be more because of the interesting way I've setup my bike so I have a switch on the bar that turns the motor on and then the motor always runs with just enough torque to keep the freehub engaged. This means throttle response is smooth and instant which is great for the extremely technical terrain I ride but can cause weird side effects due to chain growth which I had to get around. Just looking at it though I don't think the Frantik has that much, the V10 has an absurd amount due to the VPP suspension. Also meant I had to make a custom articulating chain tensioner.

 

[JRR-1]

The problem with 26" bikes is the geometry. The frames are short and high compared to more modern ones. They are cheap for a reason. The frames from the 27,5" and 29" era are longer and lower. The rider sits more between the wheels than above the wheels like it is with 26 inchers. They tolerate more speed and handling is way better. I recommend to go 27,5" and look for a frame not older than 2015.

I have an X1 pro gen2 on a 26" dh frame and it's good for a sunday road rides, not so good for offroad anymore. You can ride it but more modern frames just handle so much better. As I looked for a more modern frame to build my bonnell copy I ended up with a alu frame 27,5 Trek Remedy. Looks promising to be a very capable offroad rig so far.

 

[scianiac]

The problem with 26" bikes is the geometry. The frames are short and high compared to more modern ones. They are cheap for a reason. The frames from the 27,5" and 29" era are longer and lower. The rider sits more between the wheels than above the wheels like it is with 26 inchers. They tolerate more speed and handling is way better. I recommend to go 27,5" and look for a frame not older than 2015.

I have an X1 pro gen2 on a 26" dh frame and it's good for a sunday road rides, not so good for offroad anymore. You can ride it but more modern frames just handle so much better. As I looked for a more modern frame to build my bonnell copy I ended up with a alu frame 27,5 Trek Remedy. Looks promising to be a very capable offroad rig so far.

While those facts about modern bikes are true (and the sales pitches for most modern bikes) they are overly simplistic. To say XYZ geometry is just better in every way all the time is ridiculous, that's why the geo of modern trail bikes is different than modern DH bikes. It depends on where and how you are riding. If you are riding fast DH tracks like modern DH bikes are designed for by all means go with that but I think they can be too slack, too long, and too low for many of the trails people actually ride which are slow, tight, awkward and rough. A DH bike from 2010 assuming you size up to match the reach ends up being pretty similar in head tube and wheelbase to a modern trailbike, probably slightly higher BB.

You should look for a bike that fits your trails and riding style. If that is MTB focused trails and fast then yeah a modern DH bike is ideal. But I'm guessing like many while I have lots of trails to ride only a few are MTB trails, the rest are multiuse and I don't ride fast like I'm trying to win a DH race, chances are if you have the skill to ride real fast you don't need any of this advice because you already know it but if you're like me and are not a DH racer you should consider a bike that fits your needs.

 

[phobos]

the geo of modern trail bikes is different than modern DH bikes

spot on. Modern DH bikes are optimized for, you guessed it, going fast down a very steep hill. Climbing them is a nightmare and plain unsafe. They also pop wheelies easily for that reason as the chain-stay length is relatively short compared to the wheel base.

Suspension kinematics are also designed differently, suspension activity and plushness is prioritized over anti squat and anti rise figures, leverage ratios are higher and very progressive to accommodate coil shocks. This can be a good thing, pedal bob is not something a cyc x1 pro user would care about.

Most modern DH frames do not allow for a dropper post insertion as dropper is not used in DH.

I also agree that old frames designed for 26 inch wheels have bad geometry and suspension kinematics.

I would choose the best tool for the job, ask yourself where are you going to ride the bike 90% of the time and choose a modern frame based on that. Factor in additional requirements of fitting a battery and motor, so nice and open main triangle and relatively straight downtube, no obstructions around the BB area.

Me personally - I ride mostly gravel and forest fire roads 50% of the time and green and blue single track 40% of the time, the rest is in the city and on pavement. I chose a 150/150 trail frame on 27.5mm wheels for more comfort (Scott Spark), but I could easily pick a 100-120mm full suspension 29er XC or even a hardtail frame.

 

[scianiac]

I also agree that old frames designed for 26 inch wheels have bad geometry and suspension kinematics.

I would choose the best tool for the job, ask yourself where are you going to ride the bike 90% of the time and choose a modern frame based on that. Factor in additional requirements of fitting a battery and motor, so nice and open main triangle and relatively straight downtube, no obstructions around the BB area.

I do agree that modern geo is better but I don't think it's always better enough to justify the cost and it's not better in all ways. There are a lot of ebike conversion use cases where the geo of an older bike is just fine or better than an equivalently priced modern bike.

There are also cases where the slightly older, and again we aren't talking pre-2010, geo may be more suited than some modern options specifically for ebike applications. In ebike applications a DH bike frame and suspension but with more trailbike geo like an older DH bike suites well. You don't care about the weight or pedaling or dropper etc, you want more suspension, stronger frame, etc and you want geo that is not super slack, super long and super low because you are riding terrain that is more suited to slackish, longish and lowish like you would ride a trailbike on.

If you have high speed gnarly bike park like DH trails then yeah a modern DH bike is what you want. But I think realisticly the trails most people ride and have access to on ebike builds are a few mountain bike specific trails, lots of multiuse trails and a good bit of fire roads. And those mountain bike specific trails are probably pretty tame unless you live in one of the few places that are MTB centers.

Also have fun finding a modern DH bike with a straight downtube and no obstructions around the BB, they exist but don't seem very common anymore.

All that being said would I still maybe pick a modern DH/Enduro bike and try to optimize it for my trails if budget were no option, more tire choices is nice, more modern suspension, slightly better kinematics although many of those haven't changed much since 2010-2015. But I would be looking over the numbers and considering bikes that are not too much geo for my riding.

 

[Klyph]

Hello I have the a-65 battery and the gen4 x1 pro motor does anyone have any frames they have had luck fittimg both of these on currently i have them fitted to a 2004 era khs alite hard tail and i want to change to a rear suspension of some sort but i have been comming up with nothing. One or two frames that cost 3.5 k which is out of the budget for now. Any thought help. I will of course scower the forum if this info is already posted somewhere else.
Thanks