Specialized Hardrock Disc brakes and conversion

[Smashing1978]

I'm looking for some help with a new e-bike conversion. I bought a used specialized Hardrock which has a good steel frame. I'm hoping to install a Bafang 8fun-BBS02-48V-500W motor in it. I think I want disc brakes, especially considering I weigh 230lbs and I'd like to be able to pull a small trailer.

I need a whole slew of parts to get this bike there. I think I can upgrade to disc brakes because it looks like there's mounting brackets for it in the rear, but the brackets are on both sides of the bike, and typically I believe they should only be on one side of the bike so maybe it's something else? could someone take a look at the attached picture and let me know if that's a disc brake mount or not? There's not one up front, so I'll have to buy:

forks, hubs, wheels, cables, aligator AIS housing, levers, disc brakes, mid-drive kit, batteries.

I could use some suggestions on a good fork, hubs(that support disc brakes) and tires. Once I have them I can at least ride the bike, like a bike and it'll be ready for the next step, buying a motor, batteries, etc. But I'd like to get it up and running as a bicycle first. The catch is that I want to make sure the parts will work well after it's converted to an e-bike. And It'll need to pull my weight and possibly a trailer. I'm not sure if that affects what kind of tires/fork that I'll need.

 

[Smashing1978]

rear hub
View attachment 1

front hub

 

[amberwolf]

I'm looking for some help with a new e-bike conversion. I bought a used specialized Hardrock which has a good steel frame. I'm hoping to install a Bafang 8fun-BBS02-48V-500W motor in it. I think I want disc brakes, especially considering I weigh 230lbs and I'd like to be able to pull a small trailer.

Rim brakes will do just as well as disc (probably better, for the price difference--they have a larger "disc" (your rim)). Unless you end up in wet-rim or dirty-rim conditions that affect your braking, where those same conditions wouldn't get the discs wet or dirty, I'd guess it's easier and cheaper and just as effective to keep what you have, perhaps changing pads to Koolstop or something if you find the need.

If you go disc then you'll probably have to change the front fork to do that, or else do what I did and weld on a bracket if they're steel. There are some bolt-on brackets I've seen around for either front or rear disc, but I couldn't say how well they work-never tried.

On mine, adding the bracket ended up being mostly a waste of time, cuz the cheap disc brakes ended up not really being any better (sometimes not even as good) as the cheap rim brakes, with the sole exception that they would still work even if hte rim was bent enough out of true to make me disconnect the rim brakes due to rubbing.

That's on my really heavy CrazyBike2, which with me (~165lbs right now) on it and carrying my usual daily stuff and tools on it and extra battery probably weighs a total of 350lbs right now. Maybe more. I also pull a trailer that cna sometimes be loaded down to add another 200-300lbs, and still only use my front rim brake to slow me down (well, that and sometimes regen in the front hub motor), but when I add that trailer I also only ride around 15-17MPH instead of 18-20MPH, becuase it makes it that much harder to control, stop, etc.

I need a whole slew of parts to get this bike there. I think I can upgrade to disc brakes because it looks like there's mounting brackets for it in the rear, but the brackets are on both sides of the bike, and typically I believe they should only be on one side of the bike so maybe it's something else?

Most likley those are jsut rack/fender mounts. You'd have to measure their spacing to see if they match brake mount spacing, but probably they dont'.


Tires...depends on where you ride (terrain, weather, etc).

Overall I'd guesstimate that if you really want disc you're better off finding a completely differnet bike to convert, that already *has* the disc brakes.

 

[Smashing1978]

thanks, that helps a lot. I'll look-up what normal spacing is and measure them.

 

[Drunkskunk]

In all honesty, while the rock hopper is a great bike, and near perfect for most conversions, It may be cheaper to hit craigslist and get a bike with disk brakes already.


Unfortunately, you may be SOL adding disk brakes to that bike. The rear is a fender and rack mount. the size, spacing, and placement are all wrong for adding a disk. The front fork is a 1" head tube. there aren't any quality shock forks with 1" head tubes now days. The new standard is 1-1/8th inch.

If you can weld, it may be possible to dismantle the front shock and weld on a bracket for a disk brake. I absolutely wouldn't try one of the bolt on conversions for a front brake. Any malfunction could cause a sudden wheel lock that could kill you really easily. On the rear, a bolt on is a possibility. A rear wheel locking up isn't normally a big problem.
However, a rim brake on the rear may be all you need anyway.

Replacing the hubs for disk brakes means relacing with new spokes, and will cost you around $100 per wheel if you do the work your self. ($40-60 for hub, $40-60 for new spokes, shipped.)
Good disk brakes (Avid BB7, Hayes, Hope, Magura ) can be had used or one season out of date for $100 a set from ebay. Cheap disk brakes (Any Tektro or any Schwinn priced under $150) aren't worth the effort.

 

[Chalo]

I weigh about a hundred pounds more than you do, I haul cycle trailers regularly, and I would never consider fitting discs to a bike like yours that has no mounting points for them. I have bikes with and without discs, and there is no categorical performance advantage to disc brakes. The only outright advantage to discs is that they remove restrictions on the size and width of your rims and tires. They do this at the expense of requiring wheels that are intrinsically weaker than non-disc wheels, all else equal.

Don't waste your time and money. Decent discs will cost you at least $150 for the brakes, at least $150 for disc compatible wheels, $100 or more for a disc compatible fork, plus whatever modifications you must do to the bike frame. Oh, and good luck finding a disc compatible fork that matches your threaded headset and doesn't require you to buy a new headset and stem too. Totally not worth it.

If you want better braking for a reasonable outlay, these are your best upgrades, in order of benefit per cost:

1) Good new brake pads like Kool Stop "Salmon" compound.
2) Careful brake adjustment by an experienced professional bike mechanic, including fresh cables and housings.
3) New, good quality linear-pull brakes (V-brakes) and compatible levers.
4) Booster arches to stiffen your brake pivots.

There are plenty of folks who spend lots of money and effort to switch to disc brakes without first spending a little bit of money and effort to make their rim brakes work the way they're supposed to. I recommend first trying the cheaper and easier route to better braking.

 

[Smashing1978]

Thanks for the great advice. If someone who weighs more than me can run an e-bike with rim brakes, then I can too. I'll take your advice and upgrade to better pads and have a professional check them out. I'll be able to afford the motor and batteries that much sooner

 

[dogman dan]

You are rolling with v brakes with that bike for sure. Just get the best pads for them.

Changing the fork for disk front brakes could be an option, but it looks to me like that's a 1" headset bike, so fork choices will be slim.

Ride the brakes you have now, but over time, keep looking for the deal on a bike for next summer.

 

[Chalo]

Two other points:

The crank drive you picked is a good idea for wheel integrity. Hub motor wheels are not a strong as normal bike wheels of similar construction, so putting the motor elsewhere leaves the beef in your wheels (and lets you find upgraded replacements more cheaply and easily).

That RST suspension fork may be an elastomer sprung unit, and if so, the elastomers are probably wrecked already or soon headed that way. You can replace them with coil springs, tube spacers (thus converting the fork to rigid), nothing (making the fork shorter and rigid), or you can just find a new fork.