Noob here with a legit question about disc brakes

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mediumrare   1 mW

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Noob here with a legit question about disc brakes

Post by mediumrare » Jul 29 2012 12:34pm

Hey everyone, newbie here, first post and first build.

I'm going with a kit from e-bikekit.com. I live in PA near their shop and they're good guys. Front drive, 36V Lithium.

The bike is a Surly Rat Ride 1x1, disc only, with the giant Large Marge Rims and 3.0 knobbies, Alfine 8 in the rear. It's like a mini-Pugsley snow bike.

Question is: I need to find a disc setup for the front that has a very narrow caliper. I need 18mm of space between the rotor and electric hub. I can't seem to find a definitive answer, although I've see people running front hubs with discs on fat bikes before.
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fractal   1 kW

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Re: Noob here with a legit question about disc brakes

Post by fractal » Jul 30 2012 10:44am

Try Magura Gustav. I know Madrhino uses them because of their thin profile. I think they are the thinnest ones available.
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Re: Noob here with a legit question about disc brakes

Post by MattyCiii » Jul 30 2012 11:02am

I have to agree Fractal. My Gustav's need like 10-12 mm between the rotor and the wheel (in my case, the chainring for the left side electric drive... see my A-Line build thread.

Sadly the Gustav's have been out of production about a year. You can still find new pads for them, and find used Gustav's at pinkbike and ebay. I bought 2 sets back in April, took awhile & lots of effort to buy.

If you do go with the Gustavs, note that they originally shipped with a bunch of mounting adapters. You can still find the pdf showing all the options if you search. These things went for $50 and above originally, and are much harder to find than the brakes only.

If you're buying a front brake only, expect to pay about $150 for tthe brake/line/lever and mount, un used but very good condition. If you're lucky the brake you find for sale has the mount you need. If not I'd walk away, nobody wants to break a set by selling only the mount.

Great brake, lots of stopping power and uniquely meets the need of a narrow inside profile. It's a shame Magura stopped making them.
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teklektik   10 GW

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Re: Noob here with a legit question about disc brakes

Post by teklektik » Jul 30 2012 11:56am

If you want to go mechanical, you might look at Avid BB7s. I use a 185mm BB7 and BMC motor up front. The distance between the inside of the rotor to the the hub face is 11/16" or 17.5mm. The BB7 fits with about 1/8" of extra clearance (pic + description here) - just enough to slip in a tool to adjust the inner knob.

I'm very happy with the BB7 - it's about as much brake as my fork can safely handle and is a breeze to adjust. Just thought I'd throw out the option - without going down the whole hydraulic vs mechanical discussion path :) .
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Sacman   10 kW

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Re: Noob here with a legit question about disc brakes

Post by Sacman » Jul 30 2012 2:23pm

Justin at ebikes.ca sells an Ahlonga low profile mechanical disc brake caliper for $30. It's supposed to be thin enough to fit fine between the front forks and a 9C hubmotor. Look in the Store - Parts - Brakes section.

Also, you can remove 1mm or 2mm of material from your bike frame's disc caliper mounts or the caliper's mounting brackets (either or both), in order to increase distance between your disc and the side covers to your hubmotor. Local bike shops do this all the time and even have the special tool to remove the material exactly perpendicular to the mounting holes. You can bring your bike to them and have it done if you're not comfortable doing it yourself.

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teklektik   10 GW

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Re: Noob here with a legit question about disc brakes

Post by teklektik » Jul 30 2012 3:13pm

Sacman wrote:Also, you can remove 1mm or 2mm of material from your bike frame's disc caliper mounts or the caliper's mounting brackets (either or both), in order to increase distance between your disc and the side covers to your hubmotor. Local bike shops do this all the time and even have the special tool to remove the material exactly perpendicular to the mounting holes. You can bring your bike to them and have it done if you're not comfortable doing it yourself.
Gee - that's good to know - clever tool. So I guess this calls for a spacer of equivalent thickness on the motor rotor mount. Coincidentally, ebikes.ca sells rotor spacers, although you can make one from an old rotor.
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d8veh   100 GW

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Re: Noob here with a legit question about disc brakes

Post by d8veh » Jul 30 2012 6:47pm

With many motors you can solve the problem with a larger disk, which usually brings the caliper further away from the motor. Normally 180mm is enough. You only need a new disk and a new caliper mount.

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Russell   10 MW

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Re: Noob here with a legit question about disc brakes

Post by Russell » Jul 30 2012 7:04pm

I use Radius brand on both of my E-bikes, they are the narrowest I've found. Tha calipers also use easy to find Shimano pads plus the alignment hardware is similar to Avid.
Radius.jpg
Radius
Radius.jpg (84.3 KiB) Viewed 3341 times
IMAGE017.JPG
Radius caliper
IMAGE017.JPG (82.27 KiB) Viewed 3343 times
IMAGE019.JPG
Avid BB7
IMAGE019.JPG (100.7 KiB) Viewed 3343 times

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Re: Noob here with a legit question about disc brakes

Post by jateureka » Jul 30 2012 8:20pm

Is there much difference in stopping power between the Radius and Avid BB7?
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Russell   10 MW

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Re: Noob here with a legit question about disc brakes

Post by Russell » Jul 30 2012 8:48pm

jateureka wrote:Is there much difference in stopping power between the Radius and Avid BB7?

The BB7's are supposed to be the best mechanical brakes available however I never mounted my set so I can't say. The Radius calipers do use about the same size pads as the BB7's.

I don't know what your experience is with them is but mechanical disc brakes can be a disappointment for someone who hasn't used them before. It's not that they lack stopping power, it's just they require far more pressure due to less leverage than rim brakes. People often say "I can't lock up my wheel like I did with my rim brakes", which is true, but you really don't want to lock up your wheels when braking and discs offer better modulation. Also once you learn to really SQUEEZE the levers the stopping power of discs is substantial.

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Re: Noob here with a legit question about disc brakes

Post by teklektik » Jul 30 2012 9:38pm

d8veh wrote:With many motors you can solve the problem with a larger disk, which usually brings the caliper further away from the motor. Normally 180mm is enough. You only need a new disk and a new caliper mount.
This is an interesting point. In the pic I mentioned above, the adjuster part of the BB7 is actually hanging over the BMC motor with a 185mm rotor. In the picture below, the little silver thingie actually screws in and out as you turn the adjuster knob and is part of the inner pad adjuster screw (it's protuding with new pads, and withdraws with thinner used pads). If you have a larger diameter motor than the little BMC, the dimension in this photo is a more accurate representation than I gave above since it includes this adjuster component. (My Bad...).
AvidAdjuster.JPG
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mediumrare   1 mW

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Re: Noob here with a legit question about disc brakes

Post by mediumrare » Jul 31 2012 9:54pm

d8veh wrote:With many motors you can solve the problem with a larger disk, which usually brings the caliper further away from the motor. Normally 180mm is enough. You only need a new disk and a new caliper mount.
That's a good point.
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mediumrare   1 mW

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Re: Noob here with a legit question about disc brakes

Post by mediumrare » Jul 31 2012 10:05pm

Sacman wrote:Justin at ebikes.ca sells an Ahlonga low profile mechanical disc brake caliper for $30. It's supposed to be thin enough to fit fine between the front forks and a 9C hubmotor. Look in the Store - Parts - Brakes section.

Also, you can remove 1mm or 2mm of material from your bike frame's disc caliper mounts or the caliper's mounting brackets (either or both), in order to increase distance between your disc and the side covers to your hubmotor. Local bike shops do this all the time and even have the special tool to remove the material exactly perpendicular to the mounting holes. You can bring your bike to them and have it done if you're not comfortable doing it yourself.
Good stuff, thanks!
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Re: Noob here with a legit question about disc brakes

Post by Punx0r » Aug 01 2012 8:47am

Or use washers to space the disc away from the motor and then calliper away from the frame?

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Re: Noob here with a legit question about disc brakes

Post by spinningmagnets » Aug 01 2012 9:11am

$7 from ebikes.ca, easily sanded to make them thinner. Place sandpaper on a flat surface and move spacer in a "figure-8" motion.
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Re: Noob here with a legit question about disc brakes

Post by scriewy » Sep 01 2012 2:00pm

i checked few disk brake threads and Just to be clear, disc rotors are interchangeable between differend caliper brands if of same bolt patern and size.

for different rotor sizes we have different caliper adapter.

front rear calipers are usually the same, just the adapters different because of different angle of frame caliper mounts.

are the caliper adapters interchangeable between different brands for same size of disc ?

can caliper adapters be bought alone or usually just in brake kits ?

how to choose pad material, i noticed there are 3 types organic/metalic/forgot the 3rd one.

edit to add:
some time cleared to wonder around mtbr.com found out stuff.
caliper adapters can be bought alone, usually 10$ and up.

caliper adapters are not interchangeable between brands, they dont take that into accaunt, if your super lucky it'll fit

200mm & 203mm are actualy different sizes, not a local tradition from country to country to name differently, while 203 being the common size, so get 203 calipers.
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