The reason that the OEMs do this is to save some costs on the components. By using some lower grade or non branded components, the OEM can lower the selling price of the bike and still maintain their profit margin. Most cyclists look at only the shifters and rear derailleur when looking for the groupset that is on the bike, which is why the shifters and RD are always of a higher grade than other components. There are some bike brands which advertise their bike as an Ultegra bike, when only the shifters and RD are of Ultegra grade.
On the other hand, some brands do try to put a full groupset on a bike. A good example is Polygon. For their new 2015 Polygon Helios C6.0, it has a full Shimano 105 5800 groupset on the bike. Besides the usual shifters, RD and FD, it also has a Shimano 105 crankset, brakes, cassette and chain. To sweeten the deal even further, it has a decent quality Shimano RS21 wheelset with the high end Schwalbe Ultremo ZX tires!
Now, back to the Merida Scultura 5000. One of the components that is not of Ultegra grade is the cassette, which uses the Shimano 105 5800 cassette. There is nothing wrong with using a 105 grade cassette, as it performs just as well as higher end cassettes. My Dahon Boardwalk also uses a 105 cassette with Dura-Ace chain and Ultegra Di2 groupset. The Dahon Vitesse uses a mixture of 10 speed 105 5600, 105 5700 and Tiagra 4600 components with no problem at all, as they are all compatible.
I was curious to find out for myself what is the difference between the Shimano 105 5800 cassette and the Ultegra 6800 cassette. Most people know the difference to be merely weight, but are there more subtle differences? Besides the weight, what are the similarities and differences? That was the reason I went to get myself a Shimano Ultegra 6800 cassette, 11-28T to make the comparison.
The original Shimano 105 5800 11 speed cassette, 11-28T.
The new Ultegra 6800 11 speed cassette, also in 11-28T.
Actual weight of Shimano 105 5800 11 speed cassette, 11-28T is 275 grams.
Actual weight of Shimano Ultegra 6800 11 speed cassette, 11-28T is 247 grams.
The Ultegra cassette is about 28 grams lighter than the 105 cassette, which is very little compared to the entire bike weight. It is not worth changing from 105 to Ultegra cassette just for weight savings. Let us take a look at the other similarities and differences!
First, let's see how to differentiate the Ultegra sprocket from the 105 sprocket. Looking at the surface treatment, the Ultegra sprocket has a matte sandblasted finish, while the 105 sprocket has a shiny Nickel-Chrome plating. This applies to all the sprockets in the 11 speed cassette.
Ultegra sprocket with sandblasted finish on the left, 105 sprocket with shiny plating on the right.
Next, we will look at the components of the cassette, broken down into the different sprockets for comparison. From the pictures below, it will be possible to see the similarities and differences in the structure of the two cassettes.
Ultegra cassette at the top, Shimano 105 cassette at the bottom. Spot the differences!
Shimano 105 cassette. One large aluminium spider for the group of 23-25-28T sprockets, all other sprockets are individual.
Shimano Ultegra cassette. One aluminium spider for the group of 23-25-28T sprockets, and a second spider for the group of 19-21T sprockets.
The main difference that can be spotted by looking at the two groups of sprockets shown above would be the structure of the cassette. The 105 cassette has only one spider for weight saving, while the Ultegra cassette has a two spiders for more weight saving. Consequently, there are 5 spacers for the 105 cassette and 3 spacers for the Ultegra cassette.
Let's take a closer look at the aluminium spiders of the cassettes.
Spider on 105 cassette, weighing 117 grams. Spider material is aluminium, and seems to be spray painted?
First spider on Ultegra cassette, weighing slightly lesser at 110 grams. Spider material is aluminium and is anodised.
Anodised aluminium spider on Ultegra looks very good!
19T and 21T sprockets from the 105 cassette, together with a plastic spacer. Weighs 59 grams.
Second spider of 19-21T from the Ultegra cassette, weighing less at 49 grams.
Another view of the 19-21T construction of the two cassettes. The Ultegra cassette uses a spider to group the two sprockets together, while the 105 cassette uses separate sprockets which weigh a little more.
The second spider on the Ultegra cassette looks really interesting, so let's take a closer look at it.
Second spider on Ultegra cassette, for 19-21T sprockets.
The second spider is actually made of PA-CF, which is a type of tough engineering resin used for high strength applications.
Another look at the front of the second spider on the Ultegra cassette.
PA-CF is a really strong engineering resin that can be used to provide a strong structure for many components. It is a mixture of nylon and carbon fibre, which gives it high strength, and yet can be shaped easily into complex structures by injection molding. Some other components on the bike where you can find PA-CF material would be the shifters and chainrings. PA-CF is also called carbon composite in some industries.
This PA-CF is apparently tough enough to be used in high strength areas such as this, where the spider needs to be locked securely against the serrations on the rear freehub body.
Besides the sprockets, the other differences would be the spacers and the lockring.
Aluminium spacer from the Ultegra cassette on the left, resin spacer from the 105 cassette on the right. Not much difference in weight.
Aluminium lockring from the Ultegra cassette on the left, steel lockring from the 105 cassette on the right. The Ultegra lockring is anodised for a nicer appearance.
Steel 105 lockring is 12 grams...
...while the Ultegra lockring is only 4 grams!
Ultegra cassette on the Merida rear wheel.
New Ultegra cassette with a nice matte finish.
1) Sprocket teeth design is the same from 11T to 17T, and 21-25-28T.
2) Shifting performance is similar. Can't feel any difference during shifting.
1) Two spiders on Ultegra cassette compared to one on 105 cassette.
2) Different construction of 19T and 21T.
3) Different spacer material.
4) Different lockring material and finishing.
5) Different surface finishing on sprockets.
6) Weight difference of 28 grams (7g from first spider, 10g from second spider, 8g from lockring and the remainder from spacers and rounding off errors)
7) Cost. Ultegra cassette costs about $20+ more than the 105 cassette on online stores.
Seems that there are more differences than similarities! However, most of the differences cannot be seen without taking apart the cassette. Since the shifting performance is similar, it is of no surprise that most OEMs will spec a lower grade cassette to save cost, since it is next to impossible for an untrained person to spot any differences.
As previously stated, I feel that there is no point upgrading the cassette for the small weight savings. However, it is nice to use all the components from the same groupset as it looks and feels nice. That said, the other components on the Merida Scultura 5000 that are not of Ultegra grade are the brakes, crankset, BB and chain...