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Hello everyone!

Happy to be a part of this awesome community. I have a question I'm hoping to get some clarity with.

I have a 2020 All City Macho King ACE that I've built out and am loving it! I'm new to this flat mount disc brake world and this frame calls for those. I purchased SRAM Rival flat mount calipers and the approrpriate front and rear mounting brackets (here's the brackets I ordered, for front and rear: https://www.competitivecyclist.com/sram-flat-mount-caliper-bracket). My rear brake is good to go, but my front is stumping me a bit. I have a 160mm rotor with a 160mm mounting bracket. However, when I attach the caliper to the mounting bracket and then to my fork the rotor rubs on the metal part. So I had to install some spacers that go between the fork and mounting bracket. But everytime I'm a little heavy on the front brake, my entire front end will pulsate and after each ride I have to re-adjust the caliper as I get brake rub. I've got the screws torqued to 6nm, but ultimately I don't know if having thoser spacers on there might wear a dent into them or is even the correct way to install the caliper. Shouldn't the rotor fit with the correct bracket? Attached are some photos of how I have things setup, so any help or direction would be greatly appreciated!

Thanks in advance!

 

IMAGES LINK:

https://imgur.com/a/syUyhbj

15 comments

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Pilot Pete [293 posts] 3 weeks ago
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You shouldn’t have those spacers in there. You definitely have a 160mm front disc rotor? I say that because it looks as if you are trying to mount the caliper further out to accommodate a larger disc rotor.

The judder will be caused by a combination of the spacers and the pad positioning relative to the rotor I would assume. I wouldn’t ride it like that, especially if you haven’t used longer bolts to account for those spacers...

Those of us outside the US can no longer view Competitve Cyclist links so can’t see which adapters you have. The one in the other pictures looks right and orientated correctly for a 160mm rotor.

PP

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timallday [5 posts] 3 weeks ago
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Hey @PilotPete, 

Thanks for the quick reply! I'm definitely sure it's a 160mm rotor. And you're right, the caliper had to be mounted furhter out as the wheelset I have (DT Swiss C1800) would not accomodate the caliper. It would rub. So I used the adatpers that came with the wheelset.

Here's an amazon link of the mounting brakcet I purchased: https://www.amazon.com/SRAM-Flat-Mount-Caliper-Bracket/dp/B01LY5TC0V 

It sounds like you're spot on with the reason for the judder. I definitely won't ride like that anymore, hopefully I can get to the bottom of this! I do have longer bolts to accomodate the spacers. I've tried 2 different 160mm rotors, both have the same problem. 

I'm at a bit of a loss... any other suggestions?

Thanks for your help in advance!

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StewartM [27 posts] 3 weeks ago
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Hmm. Your frame is listed as being native (for want of a better word) to 140mm rotors, so I guess you've got that part right. But I keep looking at that bracket and can't see how flipping it to different orientations can make up the 10mm radius difference between that and 160. But I guess, I've got to ask, are you sure it's in the right way around? It could be that it alters the position up and down the fork rather than away from the fork to achieve the bigger diameter.

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StewartM [27 posts] 3 weeks ago
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. . By which I mean try flipping to top to bottom.

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Miller [318 posts] 3 weeks ago
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Yes, you need to make sure the Sram backet is the right way round. Presumably the 'Front 160' legened should be uppermost with a 160mm rotor. There's a Shimano equivalent thing where the labelling is on the outside of the adapter, so if you have a 160mm rotor you should be able to read 160 on the outside.

Here it is with a 140mm rotor.

//live.staticflickr.com/65535/48885157648_f6c8539c44_b.jpg)

 

 

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timallday [5 posts] 3 weeks ago
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Thanks for the tips and suggestions, everyone! Good call out about having the bracket facing the right direciton to accomdate a 160mm rotor. I double checked mine and it is oriented to take a 160mm rotor (160mm is pointing upward). Just to be safe I even tried installing the bracket in the other direction, without the spacers I have installed, and no matter which way you flip it, the outter diatmer of the rotor still rubs metal to metal on the caliper. Super frustrating! I triple checked my rotor and it clearly says 160mm on it, I have another one I used as well. But it still rubs. I'm at a total loss and stumped! So I'm going to email All City to see what they have to say.

If you have any other tips or suggestions, I'm open to them! Thanks again for all your help.

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StewartM [27 posts] 3 weeks ago
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Tim,

Are you getting anywhere? I know none of us have the answer, but we hope we can help by throwing ideas at you.

FWIW, I've just come into my office, which also looks like a bike shop with so many colleagues on two wheels, and I can tell you that every flat mount disc bike we have her aheives a 160mm rotor mount by rotating the bracket up / down. One is a Shimano bracket. Another is a proprietray BMC RoadMachine bracket shaped to the fork. Bottom line is that none of them achieve the larger diameter by spacing AWAY from the fork. This differs from post mount adapters, that do a similar thing, but also tend to push the caliper away from the fork as well. Cynically, I suggest that this newer method is because Shimano told them to not undermine the flatness of their new flat mount standard with bulky brackets.

So, I'd say, presuming the manufacturer hasn't made some massive stupid deviation from the accpeted geomtery, that your answer lies in the positioning of that bracket. Stating the obvious and leaving nothing unsaid, there's 4 ways it can go, not just two.

Anyway, if you can't get anywhere with all of that, consider modifying the bracket by drilling two new holes. Flip the orientation until you find a place with the right amount of meat on it, and measure well! Dodgy as it sounds, it's probably better than your spacers. Your bike is already telling you that!

Good luck!

 

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timallday [5 posts] 3 weeks ago
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Hey Stuart et all, 

Thanks so much for taking a look at other bikes in your sort of shop, haha. I think I've gotten somewhere! I just heard back from the manufacturer and they mentioned the fork has adjustable drop outs and in the shipped stock position, there are some special plastic spacers they include for mounting flat mount brakes. Or I can adjust the drop outs position, which would then allow me to attach the mounting bracket directly to the fork without the need of spacers! My work day is almost done, so I'll be trying this right when I get home! 

I'll keep the thread updated. But much love to all of you for the coninued help!

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StewartM [27 posts] 3 weeks ago
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Bugger I don't win the prize. I nearly suggested that. I noticed the dropout looked removable in your photos, but ruled it out too quickly. We have a couple of Canyon Aeroads here that have reversible dropouts, but I just moved on assuming that you simply woudn't do that with a disc bike. Even though it got me thinking about how you'd have to adjust a rim brake's calipers to accomodate it!

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timallday [5 posts] 3 weeks ago
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haha, all good Stewart! I appreciate the help. I haven't tried it yet, but hopefully I get to tinker today. I wonder how much it'll change my bikes handling when I flip the drop out clips around... Hopefully that fixes the brake mounting problem though!

 

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Pilot Pete [293 posts] 3 weeks ago
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Hmmn, good call. Looking again though, the axle seems to be almost as far down in the dropout as it could be, so getting the disc rotor further away from the caliper to stop it fouling looks like it could only possibly be achieved by moving the axle around to the 7 or 8 o’clock position...

PP

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StewartM [27 posts] 3 weeks ago
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Pilot Pete wrote:

Hmmn, good call. Looking again though, the axle seems to be almost as far down in the dropout as it could be, so getting the disc rotor further away from the caliper to stop it fouling looks like it could only possibly be achieved by moving the axle around to the 7 or 8 o’clock position...

PP

If it's anything like the Canyon one, it'll change the geometry by moving the axle fore and aft, not up and down. It's intended to change the trail of the bike. I can see room for it to go aft and therefore pull the rotor away from the caliper.

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timallday [5 posts] 3 weeks ago
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Hey everyone! 

Thanks again for all your help and suggestions. I adjusted the drop outs, as recommended by all city, and the 160 bracket with the 160 rotor fit without the need of any spacers! I'm pumped. The brake judder is no longer there, more like a smooth pulsate/modulation. Totally normal now. Now I'm off to go rip around the Bay Area! 

For anyone else with a macho king ace or a Columbus futura cross fork, know that you might have to adjust the drop outs or use the supplied plastic spacers. If you're running 160mm rotors. 
 

Thanks again and have fun out there. 
 

tim

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Pilot Pete [293 posts] 2 weeks ago
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Excellent, enjoy!

PP

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Pilot Pete [293 posts] 2 weeks ago
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StewartM wrote:
Pilot Pete wrote:

Hmmn, good call. Looking again though, the axle seems to be almost as far down in the dropout as it could be, so getting the disc rotor further away from the caliper to stop it fouling looks like it could only possibly be achieved by moving the axle around to the 7 or 8 o’clock position...

PP

If it's anything like the Canyon one, it'll change the geometry by moving the axle fore and aft, not up and down. It's intended to change the trail of the bike. I can see room for it to go aft and therefore pull the rotor away from the caliper.

Surely if the adjustment is fore/ aft for the axle, moving it aft is going to put the disc rotor further aft, which means further ‘into’ the caliper, thus fouling even more? Surely moving the axle forwards would position the rotor further forwards and thus start to increase the gap from the jaws of the caliper to prevent fouling?

Here is a pic of the  Columbus  ‘multi rake’ fork components, just for future thread searchers with the same issue...