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Re: Official P4 rear brake adapter thread [doublea334] [ In reply to ]
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This is great! I have a CNC and prototyping shop. Once you get it to a point, get in touch with me and I can give you a quote on getting it done out of aluminum and let me know if you need a hand with the design at all, although it looks like you have it under control :)

Cheers,
Omid

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Re: Official P4 rear brake adapter thread [doublea334] [ In reply to ]
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Not to be a Debbie-downer here, but why on earth would I want to bolt that to the bottom of my P4? The P4 rear brake isn't the greatest thing ever, but it's passable, and more importantly is very clean aerodynamically. This thing, while it's a tremendous engineering exercise (it really is a nice bit of engineering) is aerodynamically hideously bad. I can't see why, on a tri bike, I'd want to make that trade-off for perhaps slightly better rear braking?
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Re: Official P4 rear brake adapter thread [jkatsoudas] [ In reply to ]
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jkatsoudas wrote:
Not to be a Debbie-downer here, but why on earth would I want to bolt that to the bottom of my P4? The P4 rear brake isn't the greatest thing ever, but it's passable, and more importantly is very clean aerodynamically. This thing, while it's a tremendous engineering exercise (it really is a nice bit of engineering) is aerodynamically hideously bad. I can't see why, on a tri bike, I'd want to make that trade-off for perhaps slightly better rear braking?

For me, I am very happy to have dramatically better braking for the cost of maybe a watt of drag savings.
I don't have data to back it up, but below bottom bracket drag must be such a small number compared to everything else. Hell, the Shiv with Magura brakes does the exact same thing I am. Hangs it down super low for the wind to hit.

Alex Arman

Strava
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Re: Official P4 rear brake adapter thread [jkatsoudas] [ In reply to ]
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jkatsoudas wrote:
Not to be a Debbie-downer here, but why on earth would I want to bolt that to the bottom of my P4? The P4 rear brake isn't the greatest thing ever, but it's passable, and more importantly is very clean aerodynamically. This thing, while it's a tremendous engineering exercise (it really is a nice bit of engineering) is aerodynamically hideously bad. I can't see why, on a tri bike, I'd want to make that trade-off for perhaps slightly better rear braking?


how do you know the aerodynamics of the magura vs. oem brake?

for reference, on a p5, the faired vs. unfaired rear magura made absolutely no difference. so, just curious how you arrive at that conclusion.
Last edited by: jkhayc: Jan 3, 18 12:56
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Re: Official P4 rear brake adapter thread [jkatsoudas] [ In reply to ]
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I suspect it makes almost no difference aerodynamically because the flow in that location is already detached and turbulent. Add in the planned cover and they're all set.
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Re: Official P4 rear brake adapter thread [jkhayc] [ In reply to ]
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jkhayc wrote:
how do you know the aerodynamics of the magura vs. oem brake?

I don't, but I know that the OEM rear brake sits inside the cavity that this adapter bracket is sitting in, and is covered entirely by the fairing. With this setup, the rear brake sits entirely outside where the fairing would be, so in terms of aero cost it's not "OEM vs Magura" but rather "Magura vs. nothing" (if that makes sense).
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Re: Official P4 rear brake adapter thread [doublea334] [ In reply to ]
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doublea334 wrote:

For me, I am very happy to have dramatically better braking for the cost of maybe a watt of drag savings.

Just curious - have you actually ridden it and confirmed dramatically better braking?
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Re: Official P4 rear brake adapter thread [jkatsoudas] [ In reply to ]
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jkatsoudas wrote:
doublea334 wrote:

For me, I am very happy to have dramatically better braking for the cost of maybe a watt of drag savings.

Just curious - have you actually ridden it and confirmed dramatically better braking?

I have not. In fact, I have never ridden the P4 with stock brakes. But I have heard many people complain about its lack of power. Also, I have a friend who's P4 rear brake completely failed and ended with a crash. I do not wish to test for myself.

I have, however, used Magura brakes before on a loaned P5. And, my god, did I instantly fall in love. The confidence that I can lock up the wheel with a single finger really made things nice.

Alex Arman

Strava
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Re: Official P4 rear brake adapter thread [jkatsoudas] [ In reply to ]
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jkatsoudas wrote:
Not to be a Debbie-downer here, but why on earth would I want to bolt that to the bottom of my P4? The P4 rear brake isn't the greatest thing ever, but it's passable, and more importantly is very clean aerodynamically. This thing, while it's a tremendous engineering exercise (it really is a nice bit of engineering) is aerodynamically hideously bad. I can't see why, on a tri bike, I'd want to make that trade-off for perhaps slightly better rear braking?


From my understanding, it's less an issue of poor braking as it is an issue of the v-brake (both original and Evo) that are made for the P4 require constant adjustment to prevent from rubbing on the rim. This is an issue common to all v-brakes, but the narrow width of the P4 v-brake increases rubbing. So, I'm going to imagine that having brake rub nearly every pedal stroke is worth addressing.

I love the idea of having the adapter cnc'd. Further, I'd like to see a 3D printed cover that attaches to the cnc machined adapter, and fits the Tririg and Magura brakes.

Good luck, and great work. I look forward to seeing the final product.


now, to comment on braking: I've used DA, Red, Campy, EE rim brakes, and the Magura hydro-rim brakes are a dream to use - the ratio between lever movement and pad movement is perfect.

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Re: Official P4 rear brake adapter thread [milesthedog] [ In reply to ]
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milesthedog wrote:
jkatsoudas wrote:
Not to be a Debbie-downer here, but why on earth would I want to bolt that to the bottom of my P4? The P4 rear brake isn't the greatest thing ever, but it's passable, and more importantly is very clean aerodynamically. This thing, while it's a tremendous engineering exercise (it really is a nice bit of engineering) is aerodynamically hideously bad. I can't see why, on a tri bike, I'd want to make that trade-off for perhaps slightly better rear braking?



From my understanding, it's less an issue of poor braking as it is an issue of the v-brake (both original and Evo) that are made for the P4 require constant adjustment to prevent from rubbing on the rim. This is an issue common to all v-brakes, but the narrow width of the P4 v-brake increases rubbing. So, I'm going to imagine that having brake rub nearly every pedal stroke is worth addressing.

I love the idea of having the adapter cnc'd. Further, I'd like to see a 3D printed cover that attaches to the cnc machined adapter, and fits the Tririg and Magura brakes.

Good luck, and great work. I look forward to seeing the final product.


now, to comment on braking: I've used DA, Red, Campy, EE rim brakes, and the Magura hydro-rim brakes are a dream to use - the ratio between lever movement and pad movement is perfect.

This is exactly right. I bought my new 2011 P4 in Jan 2012. Enjoyed it for five years but was constantly having to adjust the rear brake / rubbing, etc. The rubbing issue cost me a podium more than once.The actual braking (lack of) I could live with. Only disc wheel that would fit was the original Zipp 900 because of the tight clearance. Last January, my LBS was doing it's annual tune and confirmed the brake couldn't be adjusted to prevent the occasional rubbing. Cervelo replaced with a 2014 P5 frame which I've ridden this past year. PITA to pack and ship but a superb bike and brakes work great. The P4 was a great bike....if you can get by just using the front brake. I don't know if I'd put a lot of time/money into this frame....just my opinion.
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Re: Official P4 rear brake adapter thread [gphin305] [ In reply to ]
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gphin305 wrote:
I don't know if I'd put a lot of time/money into this frame....just my opinion.

unless you're one of us folks who can't get low enough on a P5.

I'm on a Speedconcept and can't quite get low enough; the new P5x would probably do the trick, but the price.... so, this is where the P4 comes in nicely. It has amazing geometry.

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Re: Official P4 rear brake adapter thread [gphin305] [ In reply to ]
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gphin305 wrote:

This is exactly right. I bought my new 2011 P4 in Jan 2012. Enjoyed it for five years but was constantly having to adjust the rear brake / rubbing, etc. The rubbing issue cost me a podium more than once.The actual braking (lack of) I could live with. Only disc wheel that would fit was the original Zipp 900 because of the tight clearance. Last January, my LBS was doing it's annual tune and confirmed the brake couldn't be adjusted to prevent the occasional rubbing. Cervelo replaced with a 2014 P5 frame which I've ridden this past year. PITA to pack and ship but a superb bike and brakes work great. The P4 was a great bike....if you can get by just using the front brake. I don't know if I'd put a lot of time/money into this frame....just my opinion.

I'm moving from a 2009 P4 to Cervelo P2 with Magura brakes and can echo most of those sentiments about braking power. I used a Renn Disc and the aluminum braking surface was much better (provided adequate braking power) than a Zipp 900 that I tried.

However, adjusting the brakes for rub was never an issue for me(?). Just curious, but did you have an in-line barrel adjuster? I did, and perhaps that made all the difference to get the brake set up with the right clearance the first time.
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Re: Official P4 rear brake adapter thread [beston] [ In reply to ]
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beston wrote:
gphin305 wrote:

This is exactly right. I bought my new 2011 P4 in Jan 2012. Enjoyed it for five years but was constantly having to adjust the rear brake / rubbing, etc. The rubbing issue cost me a podium more than once.The actual braking (lack of) I could live with. Only disc wheel that would fit was the original Zipp 900 because of the tight clearance. Last January, my LBS was doing it's annual tune and confirmed the brake couldn't be adjusted to prevent the occasional rubbing. Cervelo replaced with a 2014 P5 frame which I've ridden this past year. PITA to pack and ship but a superb bike and brakes work great. The P4 was a great bike....if you can get by just using the front brake. I don't know if I'd put a lot of time/money into this frame....just my opinion.


I'm moving from a 2009 P4 to Cervelo P2 with Magura brakes and can echo most of those sentiments about braking power. I used a Renn Disc and the aluminum braking surface was much better (provided adequate braking power) than a Zipp 900 that I tried.

However, adjusting the brakes for rub was never an issue for me(?). Just curious, but did you have an in-line barrel adjuster? I did, and perhaps that made all the difference to get the brake set up with the right clearance the first time.

Yes, had the barrel adjuster....and also used the Zipp 900 with the aluminum braking track. The problem was (and was getting worse over time), the "stud" that attached the brake assembly to the frame was held by epoxy and was starting to loosen and wobble, therefore one side of the brake would not release properly when the brake would be first applied. I never realized this and spent a lot of time shaving down the pads. The last few races I did with the bike, I only used the front brake. After the 2016 season, my LBS contacted Cervelo who confirmed this was a common issue and was not repairable (I was hoping it was.....loved the bike). The stack and reach was close enough on the P5 and I was able to duplicate my position.....no issues. I think the P5 bike is more stable and handles better and I've kept or improved my bike times while switching to a pair of Enve 8.9s. And the brakes required no adjusting this entire last season. That's why I said I wouldn't spend a lot of money fixing a P4 over maybe a used P5, and you would have more rear wheel choices.
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Re: Official P4 rear brake adapter thread [milesthedog] [ In reply to ]
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I'll second this. I have a 2011 P4 that I absolutely love, however, that back brake makes everything so much more difficult. I couldn't figure out why everyone was passing me on the bike at Choo 70.3 in 2016 until I went to get my bike after the race and the back wheel wouldn't move. I'll gladly give up a watt or two if I can use a Tririg brake instead of that crap that's on the bike now which is not even remotely usable.
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Re: Official P4 rear brake adapter thread [milesthedog] [ In reply to ]
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The P4 was before I really got into tri. Something I have been wondering..... I have seen many people refer to the p4 as a flop. Why? It has great geometry, so why was it a flop? Help me understand what I am missing.

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Re: Official P4 rear brake adapter thread [stevej] [ In reply to ]
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stevej wrote:
The P4 was before I really got into tri. Something I have been wondering..... I have seen many people refer to the p4 as a flop. Why? It has great geometry, so why was it a flop? Help me understand what I am missing.

Well, I was selling Cervelo at the time. I liked it, but there were four things that I was hearing from customers and other shops that made it unattractive to buyers: the very skinny downtube, skinnier than the P3 and P3C, was deemed odd looking; the waterbottle was deemed non-functional and odd looking, especially with how the frame looks when the bottle is removed; and shops hated working on the rear brake, they hated how dirt collected inside the rear brake area, and tire/rim clearance was an issue. I saw shops not wanting to sell this bike.

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Re: Official P4 rear brake adapter thread [stevej] [ In reply to ]
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It's a flop because it didn't sell well. There are a lot of reasons for this, but basically that's why.

Most people don't ride long and low, or at least aren't fit long and low, so it's not great geometry for them. Think of the bike fits at your average tri, they'd be on a foot of spacers. Additionally the rear brake is difficult to set up and from the sound of things it is easily misaligned so it rubs while you ride.
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Re: Official P4 rear brake adapter thread [milesthedog] [ In reply to ]
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milesthedog wrote:
stevej wrote:
The P4 was before I really got into tri. Something I have been wondering..... I have seen many people refer to the p4 as a flop. Why? It has great geometry, so why was it a flop? Help me understand what I am missing.


Well, I was selling Cervelo at the time. I liked it, but there were four things that I was hearing from customers and other shops that made it unattractive to buyers: the very skinny downtube, skinnier than the P3 and P3C, was deemed odd looking; the waterbottle was deemed non-functional and odd looking, especially with how the frame looks when the bottle is removed; and shops hated working on the rear brake, they hated how dirt collected inside the rear brake area, and tire/rim clearance was an issue. I saw shops not wanting to sell this bike.
Love how looks came before the crux of the issue. :D Damn I love slowtwitch. Yep the rim/tire clearance was a big problem. And that stupid rear brake design.
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Re: Official P4 rear brake adapter thread [Dilbert] [ In reply to ]
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Well, if the looks are off then the customer will just bypass the bike for something else, so those other technical issues don't even come up.

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Re: Official P4 rear brake adapter thread [doublea334] [ In reply to ]
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Alright guys, here's an update. Had a new prototype printed and it is better.
I dremeled open the stock brake cover to allow the Magura to fit partially inside. The cover still covers up the shift cabling and keeps things clean. (I think it's clean - people will bitch that it's not 100% faired)

Tire and rim clearance remains the same as the stock brake, so that's good news. Looking to print off 1 final design this week and ride it. Then can give more feedback and see the interest in producing more to the lovely ST crowd.

Btw, there is another forum member, notaero, who has claimed to have created a similar adapter for Magura brakes. However, he hasn't responded to any of my PMs or other members requests for photos. So keep bugging him :)










Alex Arman

Strava
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Re: Official P4 rear brake adapter thread [doublea334] [ In reply to ]
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That looks awesome! Well done. Magura brakes (or tririg) on a P4 could definitely breathe new life into that frame.
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Re: Official P4 rear brake adapter thread [doublea334] [ In reply to ]
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Hi, nice work.

I am working away from home/my bike, so I do not have access to take photos, and rarely have the time to look at this forum. My concept is similar, however there is more spacing between the bolt closest to the BB axis and the Magura. I use 4 holes total. I have the brake a little closer to the frame, and the brake blocks are nearer to the end of their adjustment range. The side effect is the tyre clearance is a little larger, but the width between chain stays is the real limitation there. I used 5083 aluminium plate.

One note, the crank set in the photos is missing the NDS arm retention bolt, i would not ride that without it.
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Re: Official P4 rear brake adapter thread [notaero] [ In reply to ]
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Thanks, appreciate the info and your design. Just giving you some shit for no replies :)

I am going to try and space the brake a bit further away from the tire, and slide the brake shoes to the end of the caliper, like you mentioned. Currently, I am trying to figure out a way to mount the brake cover AFTER mounting the caliper and adapter. Right now, I have to mount them together - which isn't that big of a deal, just means the caliper has to be perfectly centered on the adapter at time of installation.

And yes, the crank bolt is missing, but it's just a pre-load bolt. No different than removing your stem top cap after properly torquing down your stem on the steerer.

Alex Arman

Strava
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Re: Official P4 rear brake adapter thread [doublea334] [ In reply to ]
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OT but, my caution comes from a singular experience seeing a Rotor 3D arm drop off the axle during a hill climb. The 500w - 0w crash resulted in the rider (who is a competent mechanic) laying on the wrong side of the road. We put it down to the arm working itself off the greased/antiseized spline. Secondary retention is nice.
Last edited by: notaero: Feb 7, 18 0:08
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Re: Official P4 rear brake adapter thread [doublea334] [ In reply to ]
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Latest update: It's complete! The final version was 3D printed out of pretty thick plastic. It's sturdy, so not yet sure if it needs to be made from aluminum.

I have yet to ride it outside :/ But will put it to the test in a race this weekend. So if I don't die, I'll have more photos and details for everyone next week.

Alex Arman

Strava
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