Adapter for bigger brake rotor

On my KH24", the brake mount has holes that are parallel to the hub, and therefore it needs an adapter to install the brake caliper. It looks like that :

If I was to put a bigger rotor, I would need a different adaptor to have the caliper a bit further from the hub. Makes sense.

On my 36" QU’Ax uni, it’s different. The brake caliper is attached directly to the frame with a square mount welded to the bottom and with threaded holes that are parallel to the cranks:

I currently have a 160mm rotor. I was thinking about putting a larger one since the wheel has so much torque. But then, how do I do it? Just washers and longer bolts?

You have PM mount on the frame and PM caliper, so you need PM/PM brake adapter e.g.

Looking at my own photos, I realize that it may be a bigger job… Do I need to remove the bearing to access the rotor?
I don’t have a bearing puller, so if it’s necessary to have one, I might stick to that 160mm.

Thanks Vookash. Our unis are considered “Front mounts” from a bike point of view?

Can’t quite see in the photo and don’t know that uni, but very likely. I upgraded my disc on my 36" from 185 to 200 about 2 months ago and had to buy a bearing puller. There are some different ones and some different threads, but it’ll cost you $25-$60. I was a little skeptical about it but it worked out okay.

Yes. So depending on the mount you either need a PM-PM adapter (like on your 36) or IS-PM adapter (like on your 24).

Did it make a difference? I felt that if the first bite on the brake is pretty surprising, on longer descents, I need to press pretty hard to have some effect. Maybe I “just” need better pads and/or a bleed.

Yeah, it made a big difference and I really like it. With the 185 I was having to pull hard on the lever, but with the 200 it’s almost relaxing to ride downhill (that’s with the same brake and same pads). There was quite an increase in power (at least the feeling anyway).

On the other hand on my 26" I upgraded from a 160mm to a 185 disc and it was too strong. The bite was really strong so it was hard to do light dosage. While I’m sure you could get used to it, I switched back to the 160 and am much happier.

So from my experience the disc size really makes a difference: too big and it catapults you off and too small and you kill your hand pulling (I have lots of experience on mountain bikes where it makes much less difference and bigger is always better, except for weight, and it’s more an issue of preventing overheating and fade than pure power).

I like 160mm on 24" and 26" and 200mm on my 36". I don’t have a 29" but I think either 160/185 would be good.

That makes sense, I got the exact same feeling when I went down a rather long hill (not steep but constant). It felt like the more I went down, the more I had to really pull on the handle. It’s only later that it occurred to me that between the size of the wheel, and my weight applied to one wheel, 160mm was probably a bit small to have the usual braking power.

My brother confirmed he has a bearing puller, so I’ll go ahead with this mod. It’s cheap enough to get a rotor and a mount adapter, so why not!

Just talked to my brother, that’s the kind of bearing puller he has:

Would that work? I have a feeling I won’t be able to grab the bearing as there might not be enough room between the spokes and the back of the bearing. What do you guys use?

Looks right. There’s lots of different ones. The important things are the diameter size range (i.e. not too big or too small) and how the arm hooks sit on the back side of the bearing.

It depends on how tight they’re on. I bought a cheaper set than yours and bent them. If yours don’t work you could try to see if an auto parts store has a beefier set. They usually will let you borrow tools with a deposit. I did that and got one side off but had a really stubborn one. I ended up buying this set:

It works like a charm and I haven’t had any issues since. Note that if you really have to pull them off getting them back on won’t be a picnic. You want to get a section of seat tube or something similar you can use to bang them back on without wrecking them.

Those work just fine, it’s what I use. Depending on the frame you might have to remove it before the jaws will fit around the crank but I’ve yet to meet a crank/bearing that it can’t get.


I like 160mm on 24" and 26" and 200mm on my 36". I don’t have a 29" but I think either 160/185 would be good.[/QUOTE]

I’m interested in more opinions on this point. Thanks

160 works just fine for me on my 24". I’m now building a G27,5+ and will also use a 160mm Rotor. We’ll see how it works.