Replace 7800 Dura Ace crank arms?

Discuss light weight issues concerning road bikes & parts.
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trysixty
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Joined: Tue Jul 14, 2009 5:41 pm

by trysixty

with carbon? carbon/aluminum?

worth it? recommendations on crank arms? dont need chain rings, riding oysmetrics

thanks

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yourdaguy
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by yourdaguy

You can spend a lot of money and there are probably only 5 or so cranks that are overall slightly better and some of them require a different frame. If you are dying to spend money on your bike, for less than $200 you can get a ceramic BB for your 7800 crank. I recommend Enduro. http://endurobearings.com/
For certain parts stiffer is more important than lighter.

trysixty
Posts: 12
Joined: Tue Jul 14, 2009 5:41 pm

by trysixty

the information i found on this forum and other internet sources indicate only 1-2 watt increase with ceramic bearing in the BB.

on the lighting carbon crank website they were showing almost 170 grams lighter for their crank arms than dura ace ( just arms, no rings)

please show me if you have different numbers, in no hurry to blow money......just want to have the lightest cost effective bike. thanks

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WMW
in the industry
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by WMW

trysixty wrote:the information i found on this forum and other internet sources indicate only 1-2 watt increase with ceramic bearing in the BB.


No way is it that high.

And 1W saved would be faster than 170g lighter in every situation.
formerly rruff...

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yourdaguy
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by yourdaguy

The 7800 cranks are stiffer which to me means they are better because they transmit more of your power. 1 watt continuously over a 50 mile ride is something like 25 feet and probably no crank you can buy will give you that and a less stiff crank might loose you almost that much over 50 miles.
For certain parts stiffer is more important than lighter.

Tokyo Drifter
Posts: 480
Joined: Sat Jun 06, 2009 7:28 am

by Tokyo Drifter

there are other more worthwhile things you could upgrade to.

lightning cranks are not an upgrade.

maybe look at a really nice set of shoes, a nice carbon handlebar etc.

drchull
Posts: 377
Joined: Sat Jul 30, 2011 6:38 pm

by drchull

I have ridden the 7800, 7900, lightning, vumaquads, some FSA and a SRAM S900 Quarq over the last few years. As far as overall feel and shifting the Dura Ace 7900 are the best with 7800 close behind. Now I know you are using different rings which probably takes out the main benefit of the Dura Ace cranks. The Lightnings look and weigh good but as you will see on this board have had a number of problems with creaking and breakage. I broke mine, was picking carbon pieces out of my ankle for a while. They are definitely not a install and forget about them piece like the DuraAce they need attention, making sure everything is greased and tight frequently. That is not necessarily a bad thing but it depends on how much you like to fiddle.

The VumaQuads are great and I have liked being able to switch between compact and non-compact rings. They are stiffer, light and look better in my opinion than the lightnings. Unfortunately I am selling mine (175s) as I have switched over to a Quarq. There is a great deal on a package of Vumas on the For Sale page that is keeping me from listing mine as I can't match his price for essentially 2 sets of cranks (check it out if you ride 172.5s).

The FSAs were crap and ugly.

trysixty
Posts: 12
Joined: Tue Jul 14, 2009 5:41 pm

by trysixty

have replaced pedals and shoes with very light weight alternates to shimano, guess the crank arms stay 7800. down to not much to do on my TT bike except maybe skewers and shed the foam arm pads

sedluk
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Joined: Mon Sep 07, 2009 3:10 am

by sedluk

http://fairwheelbikes.com/cycling-blog/ ... est-4.html

Looking at the shootout, the 7800 cranks are heavy. You may like them and want to keep them, but that is not the same as saying they are light. It looks like you could easily save about 200 grams.

If you weigh 225+ lbs and really torque the cranks then you should probably keep them. If you weigh 165 lbs and spin your cranks with a nice smooth pedal stroke the 7800 are overbuilt for your application. The 7800 cranks are some of the best cranks out there, but not everyone needs them.

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