Author Topic: Dura-Ace 7900 road group  (Read 4870 times)

0 Members and 1 Guest are viewing this topic.

shovelhd

  • Guest
Dura-Ace 7900 road group
« on: October 09, 2011, 07:34:21 PM »
I recently upgraded the Dura-Ace 7800 group on my Felt to 7900. The bike came with 105 from the factory, but I had a DA 7900 standard crank swapped out before taking delivery. The plan was to fill out the group with 7900 at some point, and last week was it. I'll try and compare and contrast the 7800 .vs 7900. To be fair, I bought the 7800 group used, so I can't say it was an apples to apples comparison. Take it FWIW. I purchased the 7900 group (shifters, derailleurs, brakes) on eBay from a seller in the Ukraine. Shipping was very fast considering all it had to go through. Total cost was $806 delivered.

Shifters/ergonomics:

The 7900 STI shifters have a very different shape than the 7800. The clamp end is fatter and more substantial, and the lever end is narrow, with a smaller knob at the end, and, of course, no cables sticking out of the sides. For the first few miles of my maiden voyage, I felt that I was stretched out too far, but it didn't take long to get used to it. I found that I have more hand position options on these hoods, both on the flats and on a grade. They are very comfortable once you get used to them. The extra reach puts me in a slightly more aero position with no stem change, and it further unloads the weight on my hands. There is a little less to grab onto when climbing out of the saddle, but the grip is comfortable with a nice sized notch for my thumbs. The levers splay outwards, which is very different than the 7800, and as I found out, that is because the lever throw is longer, no matter what Shimano says.

Rear shifting:

Silky smooth, positive, IMO as good as you can get in a mechanical setup, only eclipsed by DA Di2. With the KMC chain it's noisier than the 7800 but the sound is pleasant. Sweep upshifts are limited to 2 gears but that's not something I did very often when racing. It was a nice feature to use when training but I don't think I'll miss it much. Lever effort is a little higher than 7800 but that is to be expected with the hidden cables. One finger upshifts at the top of the lever are no problem. Lever throw is longer as I mentioned previously.

Front shifting:

The trim function was removed as Shimano says that the 7900 front derailleur can handle ten cogs without it. I set up the FD in one pass and was not able to achieve that goal. I get a little chain rub at the extremes. This may be able to be tuned out. Downshifts are positive and lightning quick. However, I am having a little trouble with the upshifts. My left index and middle fingers were amputated in a childhood accident, so I shift the left lever with my ring finger only. Lever effort is significantly higher, at least on my bike and with my cable run, which may be able to be optimized. If I don't give it enough of a push, the derailleur shifts but the shifter does not click, which pops the chain back down on the little ring. I found that if I give it a double pump it works 90% of the time. I feel that this issue is caused by my own limitations and really says nothing about the product. I'll get it worked out.

Braking:

The 7800 brakes were fantastic, but these raise the bar even higher. Excellent modulation, incredible power from the hoods or the drops, with the typical Dura-Ace adjustability. I cannot imagine anything better.
« Last Edit: October 09, 2011, 07:38:16 PM by shovelhd »

tetonrider

  • Guest
Re: Dura-Ace 7900 road group
« Reply #1 on: October 31, 2011, 09:16:13 PM »
nice review. 7900 levers have about 10cm more "reach" than that of the 7800 series. could be why you felt more stretched out on the hoods (esp if you didn't feel more stretched out in the drops).

shovelhd

  • Guest
Re: Dura-Ace 7900 road group
« Reply #2 on: October 31, 2011, 09:20:30 PM »
Now the right lever will sweep three gears. Go figure.

tetonrider

  • Guest
Re: Dura-Ace 7900 road group
« Reply #3 on: November 01, 2011, 10:06:11 PM »
interesting comments re: braking. using the same pads, i find that my 7800s braked a little more to my liking. that said, both are great. i've since switched to embraces (lighter, with excellent power and modulation).

shovelhd

  • Guest
Re: Dura-Ace 7900 road group
« Reply #4 on: November 02, 2011, 10:53:34 AM »
I'll keep them in mind when it's time for replacement, although I have two sets of 7900 pads ready. The biggest difference I noticed when braking was on the hoods, and it wasn't huge, just better with less effort.

Are those pads good for both carbon and aluminum? I will hopefully have a set of carbon wheels for next season and I don't want to be switching pads.

RUOkie

  • Guest
Re: Dura-Ace 7900 road group
« Reply #5 on: November 02, 2011, 11:10:48 AM »
Are those pads good for both carbon and aluminum? I will hopefully have a set of carbon wheels for next season and I don't want to be switching pads.

yes you do.
 
Even the SS yellows which are good for both wheels, it is not advised to go from AL to carbon because of the AL shavings in the brake pad.  It takes no time to switch, and is worth it to protect the expensive wheels.

tetonrider

  • Guest
Re: Dura-Ace 7900 road group
« Reply #6 on: November 02, 2011, 10:36:58 PM »
I'll keep them in mind when it's time for replacement, although I have two sets of 7900 pads ready. The biggest difference I noticed when braking was on the hoods, and it wasn't huge, just better with less effort.

Are those pads good for both carbon and aluminum? I will hopefully have a set of carbon wheels for next season and I don't want to be switching pads.

after testing, i've found the zipp cork pads to be most to my liking for carbon rims.


yes you do.
 
Even the SS yellows which are good for both wheels, it is not advised to go from AL to carbon because of the AL shavings in the brake pad.  It takes no time to switch, and is worth it to protect the expensive wheels.

agreed. a bonus with the eebrakes (for me) was that switching pads is REALLY trivial -- it's tool free. truly takes no time. not that doing it is hard with DA, but it does take a bit of work. if you must run the carbon-specific pads on an aluminum rim (e.g., flat in a race & the spare wheel is an alu rim), be sure to inspect the pad surface for aluminum shavings, at a minimum.

shovelhd

  • Guest
Re: Dura-Ace 7900 road group
« Reply #7 on: November 03, 2011, 09:57:31 AM »
I just can't see myself switching pads every week. That means staying aluminum or going all carbon.

RUOkie

  • Guest
Re: Dura-Ace 7900 road group
« Reply #8 on: November 03, 2011, 10:12:43 AM »
I just can't see myself switching pads every week. That means staying aluminum or going all carbon.

you could always buy some used zipps (non FC) that still have the AL brake track with the rest of the wheel carbon.  Those can be obtained cheap on ST nowadays

shovelhd

  • Guest
Re: Dura-Ace 7900 road group
« Reply #9 on: November 03, 2011, 03:15:43 PM »
Right, but don't those weigh a ton? Like over 1500 grams? The whole point of moving to carbon would be to gain a little aero and drop weight.

Offline ericm979

  • 1,000 and up!
  • *
  • Join Date: Jan 2011
  • Posts: 1,294
  • Location: Santa Cruz Mountains, California
Re: Dura-Ace 7900 road group
« Reply #10 on: November 03, 2011, 05:59:42 PM »
It's really not hard to switch pads.  Remove the screw and slide the pad out.  On the front I remove the wheel and apply the brake.  That moves the pads in so they can slide out of the holders without running into the fork.

I use magic marker to note F and R on the pads so they always go back in the same position.  That way I don't have to realign the holders each time.  That makes the swap quick. 

Remember that different carbon rims work best with different pads.  Some work great with cork, others work poorly and the cork pads will void the warranty.

shovelhd

  • Guest
Re: Dura-Ace 7900 road group
« Reply #11 on: November 03, 2011, 08:26:16 PM »
I know it's not hard, it's that I race a lot on the weekends and commute on the bike during the week once the weather is good enough, so it would become yet another ritual to deal with. I'll contemplate this whole thing and come up with something. Good point on the pad differences. All carbon wheels may not avoid the swap anyway. Thanks everyone for your input.