Keywords: flat mount bike

Post-mount vs flat-mount, 12 vs 15 mm

Gerard Vroomen - 04-Mar-2017
In one of the previous UPDATES, Geraint asked: "I'm sure you've written elsewhere that you didn't like 12mm or flat mount, Gerard? Why the change of tack?"



Since others may wonder the same thing, here is the explanation. 

I don't like new standards when they aren't really necessary. Post-mount works fine, so why do we need flat-mount? We don't. I think it's quite a cynical way to screw over consumers. But I can't singlehandedly stop the introduction of flat-mount, so when it is there and when for example Shimano makes the new DuraAce only with flat-mount brakes, Andy and I need to make an assessment how we deal with that. So then we have 3 options in this case:
  1. Start our own drivetrain company (that sounds like a lot of work for a 2-man company)
  2. Make our superlight frame with post-mount and force people to use something other than the lightest brakes (which then makes the complete system not so superlight)
  3. Make the superlight frame with flat-mount
If there were real technical issues with the flat-mount, we'd stick with post-mount, but in the end it's more a lateral move. Not better, not worse, just different (which is also why I was unhappy they "invented" it to begin with).

For the thru-axle, it's a similar story. 15 mm already existed and worked fine. It meant all road and mtb wheels would be inter-changeable, etc. Changing to 12 mm saves a few grams, but it doesn't outweigh that compatibility advantage in my view. But again, the industry moves towards 12 mm, it is now the standard for road disc bikes and so again Andy and I had to decide where to go.

With so many framesets and wheels coming out with 12 mm front axles, the compatibility advantage has been successfully killed. The difference in stiffness and all other technical considerations are negligible, it's another lateral move. So then it comes down to what standard we feel the most likely parts to be used on the UPPER will follow. And that's 12 mm. For the UP, it's a bit less clear-cut.

Comments & Questions

OPEN
As I understand it you can't get an adapter for flat mount brakes onto post mount frame, or do you have a solution Gerard?
Post #1 of 18. Posted by Pancho on 04-Mar-2017 05:39:26 GMT in reply to blog [0<--1561]
OPEN
Yup, my current bike won't allow me to upgrade to the new Dura Ace brakes as far as I know. Really frustrating.
Post #2 of 18. Posted by Theodore on 04-Mar-2017 06:17:02 GMT in reply to blog [0<--1562]
OPEN
Love the UPPER and your well thought out evolution of the design. The black colorway is spot on but the $1700 premium will take a little longer to justify as a consumer.
Post #3 of 18. Posted by Neil Ashton on 04-Mar-2017 06:53:53 GMT in reply to blog [0<--1563]
OPEN
I agree on the thing with what is considered standard. It's idiotic and it's same with 6-bolts vs centerlock.
However, Hope soon release RX4 caliper which i think will be better than any Shimano brake caliper.
It's a 4 piston design ment to have better clearance between disc and brake pads + better braking power.
They say it will be both post and flat mount, for either Sram or Shimano (they're different by design and usage of brake fluid).
UPper in all honor, it make sense for guys using THM crank and wheels like Bike Ahead Biturbo.
But from 2900 to 4500 Euro, puh, that is expensive.
The majority of gravel bikes cost as much or less, than the UPper frameset.
Post #4 of 18. Posted by wheels on 04-Mar-2017 09:06:13 GMT in reply to blog [0<--1564]
OPEN
Gerard,

Firstly, thanks for building these bikes. With modern distractions, getting off busy roadways is more and more apropos, especially for those of us that need to stay well to support our families. The U.P. line of frames is the answer to a question that many cyclists have been asking.

On to my question, which I have no doubt you will hate. It seems the industry--for better of worse--has determined that the road disc category will have a unwritten standard of flat mount brakes and 12mm axles front and rear. I understand that the UPPER addresses that standard. My question is, does Open have a plan in the future to change the UP frame to accommodate this industry evolution? I want to be clear, I think the UP is a fantastic machine. But as the standard evolves, I don't want replacement parts and upgrades to be unavailable.

Thanks for your involvement.
Post #5 of 18. Posted by Ben on 04-Mar-2017 13:56:02 GMT in reply to blog [0<--1565]
OPEN
I agree again on what Gerard wrote above. When you go for 12mm through axle in the front, it should raise problems if you buy 27.5'/ 650B MTB wheels as they most likely will be for 15mm through axle. Perhaps we can use an adapter for this, i don't know? I wonder why the industry makes decisions which clearly makes boundaries so obvious.
Else we may be forced to buy 650B wheels as custom builds, using a rear road hub using 12*142 for 11 speed road cassette, a MTB hub in the front to fit 15mm through axle.
Even if new Dura ace is only for flat mount, we can always hope they have both standards for Ultegra (which is more common in CX).
Or else, there is always Hope RX4 calipers (soon available).
Post #6 of 18. Posted by wheels on 04-Mar-2017 19:32:21 GMT in reply to post #5 [1565<--1567]
OPEN
Well, there are more and more 650b front wheels with 12 mm too, but definitely life would be easier with everything 15 mm.
Post #7 of 18. Posted by Gerard Vroomen on 05-Mar-2017 18:23:47 GMT in reply to post #6 [1567<--1568]
OPEN
I agree completely with what Gerard has written. However, given the industry developments I wholeheartedly welcome the UPPER with it's changes as an addition parralell to the UP. Why the indiustry has introduced 12mm on the front beats me. Anyway it is here and here to stay. However, I don't see the issue as a big problem. Yes it, makes it a little more complicated to switch wheels, but if you have a 15mm 650b MTB front wheel, chances are that the wheel manufacturer makes a 12mm axle kit for that hub too, certainly is the case with the Tune wheels we use on our OPEN builds. Just get a 12x100 front axle kit, and the wheel can be used on your mtb (with original 15mm axle kit) and on the UPPER with 12mm axle. Problem solved.
Post #8 of 18. Posted by Krischan Spranz on 05-Mar-2017 18:24:43 GMT in reply to post #6 [1567<--1569]
OPEN
Definitely for those hubs that offer that option, the problem is small. Right now quite a few hubs don't, but that may change. of course, if all wheels are dual 12/15 mm, then that does away with most of the advantage of the 12 mm standard anyway, so we could have just all stayed with 15.
Post #10 of 18. Posted by Gerard Vroomen on 05-Mar-2017 18:29:19 GMT in reply to post #8 [1569<--1573]
OPEN
Well, the UPPER has the advantage that it can accept most road wheels, the UP can accept most MTB wheels. Which is better? That's very personal. So we'll continue to monitor the market and what is available with which standard and then see if the UP should stay 15 or go 12.
Post #9 of 18. Posted by Gerard Vroomen on 05-Mar-2017 18:27:46 GMT in reply to post #5 [1565<--1572]
OPEN
So I have an unbuilt U.P. that I'm finally ready to build. Am I understanding correctly that I cannot use the new DA disc brakes on it?
Post #11 of 18. Posted by robertml1 on 06-Mar-2017 10:31:59 GMT in reply to blog [0<--1576]
OPEN
Not unless Shimano changes its mind. But you can combine the DA group with XTR brakes, which is a very nice solution (says the guy who is clearly biased since he happens to have that on his own bike :-)
Post #16 of 18. Posted by Gerard Vroomen on 08-Mar-2017 20:08:26 GMT in reply to post #11 [1576<--1586]
OPEN
Gerard,
Have you any plans for a quick release through axle system? I have seen a couple of elegant designs out there.
Post #12 of 18. Posted by Robert Franks on 06-Mar-2017 14:41:11 GMT in reply to blog [0<--1577]
OPEN
Not really. We've looked at all of them but to me they are completely pointless for a gravel/adventure bike. You always have a multi-tool with you on a ride anyway, and the 3 seconds it takes to unthread a thru-axle is irrelevant in the type of use of these bikes. The negative sides of extra weight, extra complexity that can fail and in many cases, a less secure connection that also is not as stiff far outweigh any positive.

Maybe on a road bike, with a life and death wheel change scenario, the argument in favour of a quick release thru-axle could be made, but even there I doubt it. A regular thru-axle simply isn't that slow, and has all the advantages mentioned above.
Post #15 of 18. Posted by Gerard Vroomen on 08-Mar-2017 20:06:55 GMT in reply to post #12 [1577<--1585]
OPEN
It´s not the post, or flat-mount i´m worried about - it´s the price tag hanging underneath that makes me wanna hit the brakes!
Don´t get me wrong; I really love the whole project and the philosophy behind OPEN bikes. I´m truly amazed how you guys can keep tweaking the original double-diamond design, and still find room for improvement. For this reason ( and a few others ) i was in the proces of getting used to the idea, that spending 2.900 usd on a frame kit that i intended to abuse heavily among slippery roots and unfriendly rocks, would make perfect sense. Now i just learned that 2.900 usd only gets me the second best ?!? That´s hard to swallow guys!
As for the color; i think matte black is a little tame (unless it´s because it´s unpainted) but maybe that´s just me..
Post #13 of 18. Posted by Mikster on 06-Mar-2017 15:27:59 GMT in reply to blog [0<--1578]
OPEN
2900 still gets you the exact same frame as before. Of course we could replace the UP with the UPPER and only offer the latter now, but we definitely don't want to do that. I'll continue to be very happy with my "regular" UP myself.
Post #14 of 18. Posted by Gerard Vroomen on 08-Mar-2017 20:03:12 GMT in reply to post #13 [1578<--1584]
OPEN
My Open UP frame (new version) arrived about 10 days ago. I am looking forward to riding my new bike someday, but have encountered a few problems building the bike. Although most of the problems are now solved, I am still wrestling with getting the front brake properly mounted. SRAM Force 1 flat mount brakes come with an adaptor that can be used in two positions depending on whether you choose 140mm or 160mm rotors. The Open UP expects 160mm rotors, and I have chosen 160mm Dura Ace rotors. It looks as if this adaptor needs to be removed, and you need 42 mm bolts as well as some washers to account for the adaptor. However, you will lose most of the ability to center the brakes if you try to solve the problem this way, since the brake will not have as much freedom to move back and forth. Please advise.
Post #17 of 18. Posted by Tom J on 21-Aug-2018 12:53:18 GMT in reply to blog [0<--13958]
OPEN
Hi Tom, sorry for the late reply. Yes you need remove that plate and you would need to have 37mm screws. The beauty of it is a much cleaner look and some minor weight savings. Adjustability should not be a problem. I send you some pictures by mail also
Post #18 of 18. Posted by Andy Kessler on 29-Aug-2018 11:19:45 GMT in reply to post #17 [13958<--13964]
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