Magura Caliper Adapter for Radwagon 4 w/ 180mm rotors

[the_natural]

Hi all,

I recently acquired a full set of Magura MT5e brakes. However, the calipers won't mount to the Radwagon 4 front (and I assume, rear) post mounts out of the box, as the 180mm rotors are too large.

I'd just assumed this bike has mounts that could accommodate the MT5's without adapters, because the factory rotors are 180mm; but since Margura says the MT5 will mount with no extra hardware with 7" post mounts (the 'native' size for 180mm rotors), then it's clear that I don't have 7" mounts.

So I'm looking for some clarification from anyone else who's done this already, before I order the Magura QM40 adapter for 180mm rotors on 6" post mounts.

Thanks!

[EagleEyeAZ]

I ran into a similar issue this AM when installing an Avid BB7 Mtn S caliper on the fork of my recently received RadWagon. The OEM front disk had enough lateral runout to contact both pads during one wheel rotation, ~ .040" TIR. So I installed a 180mm Galfer Wave Floating Disc rotor, with orange buttons to match the Rad Power Bikes on my white Wagon's downtube. The peaks of the waves on this rotor were contacting the throat of the caliper. Aargh. So I have temporarily borrowed both pairs of spherical washers from one stock caliper SHCS and added one pair to each Avid mounting SHCS. This increased the standoff by 0.183", probably twice what is needed. So I won't be riding the Wagon this AM because I don't want to go through the bedding process until the caliper is properly located radially to just clear the rotor OD. The Galfer rotor runs true to less than .005", and it does allow slight lateral float. A short maiden ride yesterday has me pleased beyond my expectations with the ride & handling qualities of the RadWagon and somewhat allayed a pre-purchase concern with buying a bike that has only 1 appropriate tire that's available for it. So, the_natural, you may find that just increasing the caliper standoff slightly will allow you to use the Magura calipers.

[the_natural]

I ran into a similar issue this AM when installing an Avid BB7 Mtn S caliper on the fork of my recently received RadWagon. The OEM front disk had enough lateral runout to contact both pads during one wheel rotation, ~ .040" TIR. So I installed a 180mm Galfer Wave Floating Disc rotor, with orange buttons to match the Rad Power Bikes on my white Wagon's downtube. The peaks of the waves on this rotor were contacting the throat of the caliper. Aargh. So I have temporarily borrowed both pairs of spherical washers from one stock caliper SHCS and added one pair to each Avid mounting SHCS. This increased the standoff by 0.183", probably twice what is needed. So I won't be riding the Wagon this AM because I don't want to go through the bedding process until the caliper is properly located radially to just clear the rotor OD. The Galfer rotor runs true to less than .005", and it does allow slight lateral float. A short maiden ride yesterday has me pleased beyond my expectations with the ride & handling qualities of the RadWagon and somewhat allayed a pre-purchase concern with buying a bike that has only 1 appropriate tire that's available for it. So, the_natural, you may find that just increasing the caliper standoff slightly will allow you to use the Magura calipers.

Thanks, EagleEyeAZ, and sorry to hear about the temporary setback, I know that's frustrating.

To spare myself the embarrassment, what I didn't say in the first post is that I've been running these brakes for a couple hundred miles now. Initially I thought it was fine to use the same mounting hardware -- those same spherical washers, bolts, etc -- from the stock calipers (read: I didn't have your patience and wanted to ride the bike), as an adapter didn't even cross my mind since the stock rotors are 180mm so I assumed it would all be good.

Now, after a fair amount of mileage however, and having burned through a set of pads, plus some recent weird noise issues and probably a bit of a power loss to boot (the caliper is a tiny bit too far from the rotor, resulting in slightly wonkily worn pads), I'm finally getting hip to the idea I rushed it at the outset. That said, they're still way better than the stock cable actuated discs.

I did go ahead and order the above mentioned adapter, as I'm now pretty certain that will fix it. (Also interestingly, I was able to zoom in on the front fork of a Tern GSD and even those have adapters -- they use MT5e's as well -- so I wonder if stock post mounts in this category are just uniformly 6"?)

I'm trying the adapter on the front first, and then will get another if that does the trick for the rear -- or if I keep having issues I may ditch my recently acquired Magura MDR-C rotor (up front, stock still in the rear), jump to a 203mm rotor (with yet another adapter), buy another 180mm rotor for the rear, using the 180mm adapter I just bought, and do a full, fresh setup, bed-in with all new pads and see if a "full reset" does the trick. I'll update this thread with what I learn and how it goes.

I hope your stuff arrives soon so you can get out there!

[the_natural]

Here's an update on my Magura brake upgrade situation.

Yesterday I received and installed my Magura QM-40 caliper adapter. This was the adapter I was sure I needed because the MT5e caliper couldn't mount to the post mounts on the fork as-is, with a 180mm rotor, because the rotor was too large. And since Magura says that that caliper will mount without an adapter to a 7" post mount, clearly the RW4's front fork post mounts must be just one size smaller, at 6".

Nope.

With the adapter installed, the rotor was overlapping only about 25% of the brake pads. I don't have a pic from above, but here's a pic from the side, where you can see the caliper is too far from the rotor (and thus the fork).

https://ibb.co/7zHg7X3

This was disheartening. I looked at the Magura fitment guide a million times, and this should work if the post mounts were 6", one of seemingly several standard post mount sizes in the industry. So I guess Rad went with a one-off size? I cannot come up with any other explanation. With a 180mm rotor, the caliper should've mounted without and adapter if the mounts were 7". If they were 6", the adapter I bought should've worked. Neither does.

I called support, and they weren't sure, but someone is supposed to email me back about it. I'm not really holding my breath on that, as it's a very technical question that it seems like no one there really knows. Hilariously, at one point the guy suggested that I post in a group like this to try to find out which adapter I needed.

The adapter came with two long new bolts with convex/concave washers (akin to the stock ones). So for the heck of it I swapped those on in place of the adapter and it's just about the perfect distance.

https://ibb.co/mtLsgfj

The caliper could be a hair closer to the fork, but for now, I'll take it. I'm sure Magura wouldn't approve this mounting, but it's the same as the OE setup. Ultimately I'll probably use a bench grinder to grind down the thickness of the adapter to where I need it and then go with that (if the design will allow it, which I'm not sure it will).

Just for the heck of it, below is a link to the Tern GSD's front fork and MT5e caliper. It looks to me to be the same adapter as the one I bought, and the GSD's have 180mm rotors front and rear, so same size as the RW4.

https://www.ternbicycles.com/sites/default/files/images/bikes/keybike/gsd/gen2/GSD-G2-brakes.jpg

This has been a fun first cargo ebike, but I'm really starting to feel the pull of the higher end brands.

[rtfunk]

I installed the Magura MT5 on my Radwagon yesterday.
I did not needed an adapter but I "adjusted"  the calipers with something shims, so the bike passt perfectly fit to the Brake disk.

Braking performance is way better than before.

[p_ma]

Hi rtfunk, did your radwagon originally come with radius or tektro brakes?

[rtfunk]

Hi rtfunk, did your radwagon originally come with radius or tektro brakes?

Tektro were installed originally