I am on a quest to come up with a single adjustable dropout that I can use for all of my off-road frame models. I currently use conventional style sliders on hardtails and rockers on gravel bikes.
Rocker Pros: Flat mount and Post mount brake mounts are inside the chainstay/seatstay triangle.
Rocker Cons: Dropout body is much larger, heavier and more expensive to machine. Paragon doesn’t make a PM180 rocker insert. (I have tried modeling a paragon compatible PM180 insert and it looks pretty ridiculous)
Slider Pros: Dropout body is smaller, lighter, and cheaper to machine. Simple chain tensioning.
Slider Cons: Flat mount brakes located on seat stay. (I’ve also tried creating a paragon compatible low flat mount insert, but the mounting locations land right on top of the insert attachment bolts)
What I really want is a low mount, sliding dropout system capable of FM160 and PM180.
My question: Is this a bad idea? Is there a reason this doesn’t exist already? Too much force extended out over the chainstay?
Ive found some example of low mount style adjustable dropouts but none are meant for PM180.
I meant they don’t currently do a PM180 insert for it but it might be possible. The low angle of most MTB seatstays is probably why you don’t see PM180 option for other adjustable dropouts where the caliper is placed inside the rear triangle. And you’d lose UDH compatibility which Paragon has figured out for the other two.
Putting my customer hat on for a second I guess I’d be wary of buying a frame from a small manufacturer that used a propriety dropout standard. Like I know All-City is QBP but I can’t see that system being supported forever now they’re closed down.
I think it’s all a factor of dropout angle. Sliders are good for acute angles but look wrong on more open angles. Likewise rockers with the brake inside are too big for acute mtb dropout angles. Since it seems like you want to keep PM brakes for MTBs and FM for gravel it also doesn’t seem like you are saving much inventory complexity by having one standard.
This is a hardtail with a reasonably low standover / acute angle between the stays that I built a few years ago. Fits a 4-pot caliper with no issue (160mm rotor).
I completely agree that PM180 is the key to unlocking a clean chainstay mounted PM solution. I think the easy answer for the absence of Rear PM 180 is just demand. The big rotor trend for trail bikes is relatively new and I’d wager to bet hardtails are a small portion of sales for sliding dropouts.
The heavily cantilevered brake mounts on latest super enduro inverted forks designed for 200 to 230mm rotors gives me a lot of confidence that a similar brake mount design can be made for dropouts without any issue. My own flat mount design is pretty damn cantilevered and is rock solid.
I think a slight variation of the IRD Broski Slider would be ideal. Something that allows you to attach the seatstay at the rearward most portion of the dropout (if you removed the fender mount) that allows room for the calipers on the chainstay. Then an insert that is similar to the previous generation Rodeo Labs Flaanimal but native to 160 rotors. That would allow you to to simply use a FMR to PM +20 Adapter for PM 180 compatibility. Whyte, Cannondale and Rocky Mountain all have bikes that use FMR160 with a PM +20 Adapters (most are labeled as 160) for PM180 compatibility.
To be clear, this is a PM for a 160mm rotor but I can easliy make a 180mm version for both PM and FM.
We’ve increased the torque-resistance by making the insert and dropout have a sort of rail interface and not just rely on the nub that sits inside the slot.
Your question got me googling around because I have a similar need for a future build.
I just found this one which looks really interesting!
I think for my application I’ll stick to ISO mount in the dropout system. I like ISO mount because at least with the traditional qr dropouts I like to use, the inside face is the only reference face and it’s in the same plane as the inside face of the dropout.
So I can just 3D print the parts that go in the frame and have flat plates lasercut or machined in 7075 plate to mount to it.
I personally would use a round section between the top and bottom bolt hole instead of the I-beam style because it’ll look less bulky.
Here’s a rival caliper setup 160 on a trimmed down PMW insert. Its angled down 8 degrees so that its in line with my chainstays and to make more head room for the PM setup.
I think the big difference with Curve’s drops is the horizontal distance from the axle to the mounting bolts. Moving the axle forward relative to the insert bolts clears up some of the conflict.
Very possible.
TBH, I didn’t pay much attention to that as I had official clearance-check 3D models of various calipers (incl. SRAM, HOPE, Shimano) to verify against.
But yes, this is partially why I’ve pushed the axle forward in relation to the mounting bolts, and also why I haven’t tilted the FM mounting plane down more.
This is exactly why I pushed it forward a bit.
Mine’s also 160mm native. I’ve run it with HOPE RX4+ calipers in the +20 config. So 180mm rotor with no need for a caliper adapter. No issues.
As much as I’d like to come up with my own dropout ecosystem, that sounds like a lot of design time and more importantly machining money that I don’t have. Utilizing PMWs driveside components and designing the NDS to match seems like the best option.
I think theres still some room to beef up the area you highlighted above.
Would you be able to share any of those caliper models you mention?
If you’re using s-bend stays, I think you’ll want to have the mount sit above chainstay rather than inline. Otherwise the angle of the chainstay is likely to interfere with the mount or You’ll need to triple bend the chainstay. Either way just make sure you’re also adding the chainstay to your model.
My dropout for example would for sure interfere with the chainstay if it were inline
Both models I intend to use this for have yokes mated with round 3/4” tube, so I’m hoping we can control that with bends, the real check will be what it does to heel clearance. Good call ill be sure to model the whole rear end.
any reason this part couldn’t be the stud? ( I get that its a bit pfaffy); counterbore (or /sink) the “inside” and run a bolt through it and a nut on the outside?
Sorry. I had to sign NDA’s to get access to them, so I could get in trouble if I pass them along.
Could probably work. Maybe not the cleanest from the outside when you need one nut and one bolt. Unless of course you’d make both fasteners on the left side the same.
Here’s an idea:
To avoid using a nut on the outside, maybe the double nut from PMW’s DR4145 could be used?
Make a recess in the insert, matching the nut and maybe just use a shorter bolt up front.
Needs some checking in 3D, but could be worth exploring.
ill be sure to model the whole rear end.