Having trouble fitting disc brake - Help?

[olemetry]

Hi guys. I got a RockHopper 29er with a MAC 7T. I would like to have the bike setup such that I can use the hub motor wheel and non-hub wheel interchangeably. I dont think this is too unreasonable.

I have the same exact rotor for the MAC as my regular wheel using Tektro Draco brakes. But when I attach the disc rotor to the MAC wheel, it just doesnt line up.

So first, I tried putting small washers between the motor and the rotor. Two washers allowed the wheel to be set, but the rotor was rubbing on the brake pad. Three washers also allowed the wheel to be installed, but the rotor then rubbed on the other brake pad. I then removed the washers and tried to move the wheel over by using more washers between the frame and wheel on one side, but this caused rubbing on the rotor on a brake pad too.

Has anyone worked through this problem? I should mention that the wheel description does indicate the following:
"Note that the available space for the disk is a little limited at 15mm between the side casing and the inner face of the disk, so some care when selecting a suitable caliper is required or some spacing of the disk away from the side cover and possibly modification of the caliper mounting may be required for some models of disk brake caliper."

Can anyone help? Also, is there a recommended order of washers to be placed on the axles? Or do I just play with them until it fits the spacing of the dropouts. I also got some washers that are cut and bent a bit. Are these locking washers for the end nuts?

Thanks yall.

 

[NeilP]

I think it is just a matter of playing with it and various spacers till you find a combo that fits.

My thought when i read your post was... " What is he using for torque arms?, " that must be a pain removing them each time to go between powered and non powered wheel, or do you not have any torque arms?

 

[olemetry]

Yea, I got the GRIN universal torque arm. I wont be changing them multiple times a week, so I dont mind if it takes a few minutes. But the GRIN arm has two pipe clamps, so I figure I will quickly just take em off and put em on with a battery operated drill.

 

[fabiograssi]

I easy solve this problem: 203mm rotor and adapter...

 

[fabiograssi]

This adapter is for 180mm rotor I think, so I had to use some spacers in that moment. Now I have the correct adapter...

 

[olemetry]

Hmmm. You kinda lost me. Can you be more specific? I think I have a 160mm rotor. And if I want to keep my wheels interchangeable, I would think I would need the same 160mm rotor.

 

[ladz]

You can use the larger rotors on any caliper as long as you have the correct spacers and enough extra brake cable to place it in the correct location. This is what I did too (bb7 calipers), then you have plenty of space for the hub.

 

[olemetry]

so you are suggesting a larger rotor to use on both wheels, and I will have to relocate the actual brake pad thing (caliper?) itself? what would a larger rotor do for me? I will still have to properly space the rotor and wheel in the x-plane, no?

 

[NeilP]

Yes, you would still have the same issue if you went to a 203 rotor on both wheels, but it may make it easier to solve with a 203 rotor simply because you now have more freedom of movement of the calliper, there is less or no chance of the calliper now hitting the hub

 

[MadRhino]

The solution is simple: Either you file the spacers to set the proper fit, or you change your brake for a Magura Gustav M that is a floating caliper with pistons on one side only. The first solution is cheap and fast, the second will let you use any hub motor or your stock wheel indifferently.

 

[NeilP]

Never realised or even consideted that floating types were available for bikes. I have only ever seen twin or 4 calliper brake units
But yes, something with more lateral movement would be ideal

 

[neptronix]

A disc brake caliper that has adjustment for *both* pads can help ya.
Add 2 1mm spacers.

You may also need to use a minimum of a 180mm rotor.

=

Great success!

 

[olemetry]

Perhaps I misworded my original posts. It sounds like the suggestions to use a bigger rotor are due to the thought that my caliper is rubbing on the hub. This is not the case. The hub spins great and does not touch the brake. The problem is that the rotor is touching the inside of a brake pad and I am having trouble getting it centered. Sounds like I will just need to keep playing with it and be creative.

 

[olemetry]

I stand corrected. I don' know how I missed it. The hub is just barely touching the caliper. So the idea is to get bigger rotors and raise the caliper? is there some made up spacer/adapter to use raise the caliper uniformly?

 

[GMUseless]

Also, don't forget there's some play in the mounting of the caliper as well. Loosen the bolts that attach the caliper to the mounting bracket, and the entire caliper will shift around a bit. Adjust your pads in some, then squeeze you brake lever to tighten the caliper to the rotor. While still squeezing the lever, re-tighten the caliper/bracket bolts. Then, adjust your pads back out to get the desired clearance.

At one point I had a bike that I changed the rear tires out like you are doing...and every time I had to do the above procedure to get the clearance correct.

 

[NeilP]

I stand corrected. I don' know how I missed it. The hub is just barely touching the caliper. So the idea is to get bigger rotors and raise the caliper? is there some made up spacer/adapter to use raise the caliper uniformly?

Yes there are adapters for this purpose. different types depending on the type of mounting of the caliper

 

[GMUseless]

I'm not sure those Draco's come with a 203 in the rear? Most of the adapters I've seen available for the Draco 203s are front ones.

But after $5-10 for the adapters, and $25-30 for a 203 rotor...you could get a new 2011 Avid BB7 for $60 (http://www.pricepoint.com/detail/18749-115_AVDB78-3-Parts-158-Brakes/Disc/Avid-BB7-Mech-Disc-Brake-Grey-Fnt/Rer-2011-offer.htm?utm_source=SLI&utm_medium=datafeed&utm_campaign=FTP&zmam=3075515&zmas=1&zmac=41&zmap=115%20AVDB78)

And many have used the BB7 203's with the MAC motors. I'm using them with my Mac 6T and it fits perfectly.

 

[olemetry]

By buying the BB7 brakes, will this put the caliper the proper distance from the hub? or will i need spacers witht his brake too?

Hmm I now see that BB7 is mechanical, so I will have to change out the brake lever, cable, etc. as well.

I think I will stick with the hydro brakes, get adapter, and larger rotors. How do I know what kind of adapter to use?

 

[GMUseless]

Woops, didn't realize those were Hydro. Yes, you would then need levers and cables. The Tektro site says you need an I-4..but doesn't list it. You might have to contact them directly. Otherwise, get the A-4 and shim/file it until it works.

http://www.tektro.com/_english/01_products/01_prodetail.php?pid=25&sortname=Accessories&sort=1&fid=5

 

[Chalo]

By buying the BB7 brakes, will this put the caliper the proper distance from the hub? or will i need spacers witht his brake too?

Hmm I now see that BB7 is mechanical, so I will have to change out the brake lever, cable, etc. as well.

I think I will stick with the hydro brakes, get adapter, and larger rotors. How do I know what kind of adapter to use?

There is an industry standard for how far the disc rotor mounting surface should be inside the inner dropout face. I don't remember the exact numbers, but it's about 10mm for a front brake and 15mm for a rear brake.

Bush league Chinese manufacturers don't always sweat this kind of detail. Chances are you'll have to do some improvised spacing no matter what brake you use, but the Avid BB7 does have quite a bit of lateral and angular adjustment built in. It's better in that regard than any hydraulics I am familiar with-- the caliper tilts and moves in and out from the wheel, and both pads can be adjusted independently for clearance.

Chalo