trying to figure out what brakes to use

[vin791]

i am building a dual motor 2kW (but able to be limited to 750 Watt to meet federal regulations) setup for my grad project to kind of showcase the feasibility of an electric bike. you can still have some thrill and speed from this thing but at the same time limit the power to increase the range, etc. im using some 12Ah cells that are rated at 10C nominal - 20C peak so powering the motors wont be a problem. also, im dealing with hightekbikes.com for 2 amped kits because he's $10-$46 cheaper per kit depending on what kit and if you're local you can do free pick up. plus hes willing to mix and match parts for me as where ampedbikes.com wont. which for the average customer isn't an issue, but for me having dual motors and controllers the extra throttle and brakes aren't necessary and he's giving me some "Y" adapters as well to hook up the throttle, brakes, and battery to the dual setup. im also designing a cool (i think so anyway) "body" for the bike to keep as many wires hidden as possible amongst other reasons.

now for my question. i am using a cheap motiv frame, and from what ive read the frames on these bikes are good, everything else is junk. which is what i expected. im buying a donor mongoose fireball with a broken fork to rob the shimano components off of. it has f/r disc brakes and a 7 speed rear cluster, single cog up front. so my plan is to take the 6 speed freewheel off and use the shimano 7 speed if its compatible, if not i'll use the shimano derailleur and just adjust it to only shift 6 gears (btw, is that possible?). the next problem is that my frame and fork don't accept disc brakes stock. do i need disc brakes or will a set of touring cantilevers do me justice? im aiming for the total weight of this bike to be 50-60 lbs. or, do i need disc brakes?

if i need discs, do you think it would be feasible to design a torque arm that extended out to be a caliper mount as well? or would the stress be too high? i would definitely use 2 hose clamps, one b/t the 2 caliper mount holes and one just under the bottom mount. or maybe just buy a fork w/ disc mounts, and try to rig up a disc mount in the rear? or v brake in the rear.

any input is much appreciated. and i'll most likely start a build thread when all my parts get in to show you all my progress.

thank you for your time!

 

[miuan]

Don't try to fabricate disc mounts, the torque arm thing is a bad idea too. Use the mounts you have and get some decent quality V-brakes.

 

[vin791]

thanks for the quick reply!

thats pretty much what i figured, just hoping someone else had luck with one of my crazy ideas before

do you think its worth it to get a new for w/ disc break mounts?

also, what type of puller/brake type would you recommend/ maybe one that you use and have had good results with?

idk what the advantages between center pull/ side pull, and the different rim brake types are, forgive me ignorance

 

[miuan]

What speed ar you aiming for? If over 25-30mph, you should consider something powerful. There are also high power V-brakes available, e.g. older Shimano parallelogram V-brakes. Much depends on rubber compound, stiff brake arms and good adjustment.

 

[vin791]

i dont think i'll be going much faster than that. my guess is the bike at 48v will only go about 30mph even with dual motors, it will just get up to speed way quicker. i did an ebay and local craigslist search and couldnt find anything under that name. theres quite a few good bike shops and used-parts stores here in seattle so i'll check those out plus i have quite a few avid biker friends that may have extra stuff lying around. so it sounds like i should just keep my current fork and go v-brakes front and rear, and not bother on discs on a new fork up front?

 

[miuan]

Grab these. Shimano doesn't make them anymore, so very rare to get new, here you can buy a complete pair. They're rock solid, and exactly the same as I had on my 40mph bike before it got stolen.
http://www.ebay.de/itm/SHIMANO-Deore-XT-Bremse-Bremssatz-vorne-hinten-BR-M750-/260869480670?pt=Sport_Radsport_Fahrradteile&hash=item3cbd0860de
You may want to contact the seller about international shipping since he says he only ships to Europe.

 

[dogman dan]

Good V brakes can be adequate for riding under 30 mph. Even cheap wallbike vbrakes can be pretty good with new pads vs old hard sun fried ones.

You could change the forks to ones with a disc mount, and get the most important brake to be a disk, the front. The reason to do that would be if you ride in the wet much.

 

[vin791]

thanks for the link! and thanks to google chrome i dont have to try to translate everything from german to english using babelfish lol. i'll definitely watch that auction when it gets closer to the end.

im thinking im going to spend $50 on a new fork, already have disk brakes off the donor bike im purchasing tomorrow, and then i'll get a good v brake for the rear. since i live in seattle the front disc brake is probably necessary. and recycled cycles has a lot of good used parts so i'll check there first.

but, if those v-brakes go for cheap enough i may just snag those

im still open for input at this point. also if anyone has brakes they want to sell that i would use, that would be sweet.

edit: just realized it seems they dont offer shipping to the US

 

[MadRhino]

Since the fork has to be replaced, chose one that has disc brake mounts. Good disc brake in the front is a must. As for the rear, you can find Magura HS 22 or HS 33 hydraulic rim brakes for a good price. Regen braking the rear motor is the way to shorten stopping distance, and also have safer braking on wet surface.

 

[vin791]

the fork i have is fine, i was just thinking about replacing it to use w/ disc brakes.

im thinking about going with shimano acera v brakes? they seem to get really good reviews and theyre pretty cheap. still may go w/ a disc up front if i can get a fork for cheap

 

[miuan]

you don't wanna cheap out on brakes. while these are acceptable for a sport MTB, regular braking from high speeds will make them, and you, suffer. moreso in the wet. you want a good grabby compound pad for varied conditions.

 

[MadRhino]

you don't wanna cheap out on brakes...

Exactly, money you spend on brakes is your best insurance policy.

 

[jimw1960]

I'm using Magura hydraulic rim brakes on my current build. They are pretty smooth and great stopping power.

http://www.magura.com/en/products/rim-brakes-2012.html?PHPSESSID=0e2ab73a00e983d08ce5947b0889c274

 

[Ykick]

I'm using Magura hydraulic rim brakes on my current build. They are pretty smooth and great stopping power.

http://www.magura.com/en/products/rim-brakes-2012.html?PHPSESSID=0e2ab73a00e983d08ce5947b0889c274

I like these too...

 

[vin791]

im pretty sure i can't use hydraulic brakes due the the fact that im using the brake levers that cutoff power to the motor when pulled (the ones that come in an ebike kit)

 

[izeman]

the fork i have is fine, i was just thinking about replacing it to use w/ disc brakes.

im thinking about going with shimano acera v brakes? they seem to get really good reviews and theyre pretty cheap. still may go w/ a disc up front if i can get a fork for cheap

if i remember correctly i have the xt vbrakes some lying around, as well as a magura hydraulic rim brake (hs 11 or 33)
just pm if you're interested. no problem shipping to where you want, but it may not be super cheap

 

[vin791]

pm sent. im heading over to recycled cycles right now to see what they have.

hopefully i'll have some sort of progress when i get back

 

[vin791]

i ended up getting some arch rival 4s out of the brake bin at recycled cycles. theyre in really good shape, i also got some extra pads. the guy at the shop told me they'd be adequate (and i just dont have the money after buying all the other parts for the bike to spend $200 on a disc brake setup)