Monday, 25 February 2019

Mavic Open Pro UST - the most beautiful aluminum rims?

Many people say that aluminum rims are pretty boring comparing to carbon ones. I can't argue with that as indeed the high profile of carbon rims give nice look to almost every road bike, however with the latest Mavic Open Pro rims the situation turns a bit different. Actually I found new Open pro rims the most beautiful aluminum rims I've ever seen...


The new Open Pro is the lastest generation of Mavic's rims. The version with aluminum brake surface is available since quite a while, however the exalith is not yet there. There are some rumours that the anodised surface is not permanent enough so the rim's design is still in progress.

Anyway, let me share my thoughts regarding Open Pro rim with you.

First of all the look is gorgeous, it's really a game changer. On the daily basis I ride Ritchey Road Logic and there are not too many aluminum rims which I'd use for my personal build but this one I'd welcome with my open hands. It does look brilliant. The shape, the finish, the black shiny paint talks to me.

Second, the rim is light and stiff. 430g is very low comparing to the inner width which is 19mm. I don't know how much marketing is in Mavic's folders but they mention that this rims is made from Maxtal which is 30% more resistance than traditional 6106 alloy. Again, I don't know but during the build and spoke tension relieve I really could feel that the rim doesn't flex. My guess is that the specific shape of the rim (the sort of waves around spoke holes) make this rim stiffer, same like in car industry where steel is formed to achieve great stiffness. 


Rim has single eyelets, which is a bit old school comparing to the modern rims but that doesn't break the overall, good impression about those rims.
Another thing is that there is no 20h option, only 24, 28 or 32h drilling.

Mentioning this, let's talk about a bit negative side of those rims.

First of all they are symmetrical. As we all know, with 11s cassettes the offset rims really do help to achieve greater tension on NDR side which is better for overall wheel lifespan. In order to make the things even more challenging Mavic recommends max tension of 110kgf only. Now, if you combine those two dimensions together you really need to think about the type of hub and spokes you'll use in the build. If you'll take a very wide spaced flanges hub like Miche Primato, the NDR will be below 50kgf = NO GO. If you'll take a hub which is very narrowed spaced like Tune, the wheel won't be stiff enough (unless you'll use 32 spokes and pretty thick spokes).

In other words this rim is not for every build and rather for experienced builders. It can be nice, give a lot of fun but needs to be well thought and built with quality & calibrated tools.


In my build I used 24/28h D-light spokes as the rider is not too heavy.  I also decided to go with Bitex RAF/RAR12 as they are pretty well balanced in terms of geometry. A good mid point between very wide and super narrow flanges.
Front was laced radially and rear 2x cross on both sides. Brass 14mm nipples were used as wheels will be used in all conditions.


As per my best practice I never trust any manufacturer and I do measure all by myself, this means the rims and the hubs. Mavic says ERD is 589... well it's not, it's 591. Don't fall into the trap and either use my reference here or, better measure all by yourself.

The build itself was bit long I must say. I paid a special attention to the very equal spoke tension as there are some reports in the web that with tires installed those rims expand a bit and thus there is a drop in the spoke's tension. Knowing that the key to prevent potential issues is to tension the spokes very equally with calibrated tools and do several stress relieve steps until tension remains unchanged. 
In my build I used my new tension meter which was calibrated with my tension calibration jig. I went up to 115kgf on DR to maximise the tension on NDR as much as possible.

Another small secret is to work out the spokes so they support the hub's flanges. There are several techniques to achieve that, I just call it "the spoke massage". It's pretty time consuming process but in return there is no need to correct the tension after first few rides.


I also did couple of extra steps to ensure that the wheel will stay strong. 
First the spoke nipples were treated with spoke prep and for NDR side I used Sapim's threadlocker
Another thing I did is the spoke tying and soldering. That is very useful especially when NDR is not that much tensioned. With tied spokes, the load is distributed more equally and the spokes work in pairs so overall it's beneficial for the wheel. I also protected the soldering itself with black paint which prevents future corrosion. 



The whole set without rim tape came with 1446g on the scale. Pretty good result keeping in mind 52 D-light spokes and brass nipples.



Despite the extra hours spent on those wheels I find them very beautiful and interesting build. I seriously look forward to build similar set for my personal use.

The price starts from 449 CHF so given that, those are vey attractive option for one looking for good and light wheel set.

Wheels in this configuration are available in Blackcat wheels shop. Other configurations are of course possible, depending on the rider specifics and budget.

T.

blog-wheelbuilding

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