custom ultegra 6800 50/36 crankset?

User avatar
ohexploitable
Posts: 235
Joined: Thu Jun 14, 2012 12:39 am

custom ultegra 6800 50/36 crankset?

Postby ohexploitable » Wed May 20, 2015 8:35 am

so i currently have a 50/34 ultegra 6800 setup paired with either a 12-25 or 12-30 cassette, but i'm finding the 34 a little too useless for 90% of my riding - like say i'm going up a slight incline (~5%) on either the 50t ring or the 34t ring i'll be heavily cross chaining so i stick in the 50t ring

whereas on another bike i have a 52/39 setup and would use the 39t ring and have a good chainline, in fact I will be the 39t for 50% of the time on some rides

anyway but i digress, how would shift quality be if i mixed chainrings and replaced the 34t with a 36t on my compact? I understand that shimano's shift pins/ramps and specifically tailored to 50/34, 36/52, 39/53 blah blah blah, but how noticeable would the difference be?
I DIDN'T EAT FOR THREE DAYS SO I COULD BE LOVELY

User avatar
Tim
Posts: 1786
Joined: Wed Jul 07, 2010 5:02 pm
Location: Gippsland Lakes

Re: custom ultegra 6800 50/36 crankset?

Postby Tim » Wed May 20, 2015 9:00 am

I tried a mismatched 52/39 combination on my 6800 setup.
It didn't work very well.
Upshift, small to large ring fine, downshift no good.
See this thread;

http://www.bicycles.net.au/forums/viewtopic.php?f=34&t=83701

50/36 might work a little better. I don't know, haven't tried it.

Sydney Cyclist
Posts: 25
Joined: Mon Jan 19, 2015 12:23 pm

Re: custom ultegra 6800 50/36 crankset?

Postby Sydney Cyclist » Wed May 20, 2015 10:08 am

Powertap's soon to be released C1 will have a 50/36 option. I doubt they would release it if it had poor shifting.

User avatar
Tim
Posts: 1786
Joined: Wed Jul 07, 2010 5:02 pm
Location: Gippsland Lakes

Re: custom ultegra 6800 50/36 crankset?

Postby Tim » Wed May 20, 2015 10:14 am

Sydney Cyclist wrote:Powertap's soon to be released C1 will have a 50/36 option. I doubt they would release it if it had poor shifting.


He's asking about Shimano 11 speed rings which are specifically matched pairs; 34/50, 36/52 and 39/53.
These rings aren't designed to be paired-up in any other combination/s.
As I found out a mismatched pair (39/52) doesn't work very well at all.
Other normal rings work in all sorts of combinations such as the above, but Shimano 11 speed don't.

Jesmol
Posts: 442
Joined: Tue Feb 07, 2012 3:48 pm

Re: custom ultegra 6800 50/36 crankset?

Postby Jesmol » Wed May 20, 2015 10:27 am

I have a 52/36 setup on my 6800 cranks, but would prefer compacts, if you want to swap let me know.

User avatar
cyclotaur
Posts: 1398
Joined: Wed Jan 26, 2011 1:36 pm

Re: custom ultegra 6800 50/36 crankset?

Postby cyclotaur » Wed May 20, 2015 3:05 pm

By swapping inner rings between a compact 105 road and a 105CX crankset, I now have a much better 50/36 on the roadie and 46/34 on the CX. No incompatibilities or any other issues.

It reduces the clunky 16t gap on the roadie (which now runs 12-30 on both sets of wheels) and gives a bit more climb-y ability on the CX which is running an 11-32 mtb cassette through a standard 105RD with no problems. In fact the CX has a higher top gear at 46/11 compared to the 50/12 on the roadie.

WIN-WIN !! :D

Edit: Clearly to solve your problem you need a new CX bike !!
Here's my blog - A bit of fun :)
"Riding not racing...."

User avatar
Tim
Posts: 1786
Joined: Wed Jul 07, 2010 5:02 pm
Location: Gippsland Lakes

Re: custom ultegra 6800 50/36 crankset?

Postby Tim » Wed May 20, 2015 3:48 pm

But cyclotaur, are they 11 speed rings you are combining? That is the issue here.
As I mentioned earlier pre-11 speed Shimano rings mix and match without any problems, within reason.
11 speed are designed and engineered to work as specifically combined pairs ie. 34/50, 36/52 and 39/53.
My experience is that they don't work, at least with a 39/52 combo, and I presume don't work well in any other non-recommended mix.

User avatar
cyclotaur
Posts: 1398
Joined: Wed Jan 26, 2011 1:36 pm

custom ultegra 6800 50/36 crankset?

Postby cyclotaur » Wed May 20, 2015 5:51 pm

I can't see why 11sp rings wouldn't mix n match just the same.

They are all standardised with the same BCD aren't they? I can't see what other problem there could be, albeit I have no experience with 11sp myself.

The pins and ramps can't make that much difference, surely ....
Here's my blog - A bit of fun :)
"Riding not racing...."

User avatar
Tim
Posts: 1786
Joined: Wed Jul 07, 2010 5:02 pm
Location: Gippsland Lakes

Re: custom ultegra 6800 50/36 crankset?

Postby Tim » Wed May 20, 2015 6:56 pm

Below is a direct quote from the Shimano Dealers Manual in reference to Tiagra, 105, Ultegra and Dura Ace 11 speed cranksets;

• Be sure to use the specified gear tooth combination. If an unspecified gear is used, the chain may fall in between the gears, damaging them.

This was exactly my experience when combining non-recommended chainrings. I avoided any damage by fitting the correct rings as soon as possible.

Hillsaretheenemy
Posts: 40
Joined: Thu Aug 28, 2014 8:22 pm

Re: custom ultegra 6800 50/36 crankset?

Postby Hillsaretheenemy » Wed May 20, 2015 7:16 pm

I have used 50 36 on 6800 ultegra. While it shifted ok it did drop the chain off the inside for seemingly no reason, at that point I went back to 50 34.

User avatar
Duck!
Expert
Posts: 6338
Joined: Tue May 21, 2013 8:21 pm
Location: On The Tools

Re: custom ultegra 6800 50/36 crankset?

Postby Duck! » Wed May 20, 2015 8:56 pm

cyclotaur wrote:I can't see why 11sp rings wouldn't mix n match just the same.

They are all standardised with the same BCD aren't they? I can't see what other problem there could be, albeit I have no experience with 11sp myself.

The pins and ramps can't make that much difference, surely ....

It's not about the BCD. 11-sp, plus 2nd-gen 10-sp. Dura-Ace & Ultegra (7900 & 6700) outer rings have a noticeably angled inner face, which not only ramps the chain up, but also back down, as the angle is designed to pair to a specific small ring. Pairing a bigger-than-designed small ring places that ring further away from the ramping face of the big ring, causing the chain to "hang up" between the rings rather than meshing on the small. Tuning the derailleur in further to give the chain more of a shove increases the risk of throwing it off the inside.

It's not such a problem with the 10-sp. cranks because there isn't the range of rings available for a particular BCD.
I had a thought, but it got run over as it crossed my mind.

GTPilot
Posts: 123
Joined: Sun Jun 09, 2013 10:04 pm

Re: custom ultegra 6800 50/36 crankset?

Postby GTPilot » Wed May 20, 2015 9:08 pm

I bought a 36T inner ring from Bikebug for about $30 a couple of months back for the same reason and replaced the 34t on my compact crankset with it.
I have been running 36/50 for a while now without issues. both mechanical 6800 and Di2 ( recently upgraded). From what I understand the issue is when you have more than 16T difference between the rings due to shifter reach.

User avatar
Duck!
Expert
Posts: 6338
Joined: Tue May 21, 2013 8:21 pm
Location: On The Tools

Re: custom ultegra 6800 50/36 crankset?

Postby Duck! » Wed May 20, 2015 9:32 pm

GTPilot wrote:I have been running 36/50 for a while now without issues. both mechanical 6800 and Di2 ( recently upgraded). From what I understand the issue is when you have more than 16T difference between the rings due to shifter reach.

Your understanding is incorrect. The lateral spacing is the same for all ring sizes, therefore shifter reach is constant. The limitations are front derailleur contouring, chainring ramping, and rear derailleur capacity (coupled with cassette range).
I had a thought, but it got run over as it crossed my mind.

User avatar
Bentnose
Posts: 1076
Joined: Sun Jan 03, 2010 9:00 am
Location: N/E suburbs Melbourne, Victoria

Re: custom ultegra 6800 50/36 crankset?

Postby Bentnose » Thu May 21, 2015 4:36 pm

This is a big turn off for me upgrading to 11spd, I currrently run a 34/48 9 spd but with 10 spd front rings and will soon change to 36/50 full 10spd, I not a big fan of the 16 tooth gaps, I was hoping to go to full 11spd at some point but now I'm not so sure. I do, for some reason, find that my 9spd chain can sometimes get stuck between chainrings, I'm hoping that a full 10spd setup will fix this.
2017 last time I checked 3429km, 46,000M elevation, 161 hrs, 136 rides

User avatar
Carrots
Posts: 429
Joined: Sun Feb 26, 2012 8:50 pm
Location: Adelaide

Re: custom ultegra 6800 50/36 crankset?

Postby Carrots » Thu May 21, 2015 4:49 pm

Just to add my two bobs worth...

I've currently setup the girlfriends bike with 50/36 and it is shifting fine.... But only after I realised I'd installed the 36 back to front. Oops!

I'm currently also running 52/34 on one of my bikes. For extra protection I've added a chain catcher to it (plus I put my SRM on with that combo so it doubles as a cadence magnet). I've had no shifting dramas.

My only lesson learned from the mix match (which came about from the girlfriends bike) is that 6800 rings don't fit as nicely finish wise on 9000 cranks as the 9000 rings.

User avatar
Duck!
Expert
Posts: 6338
Joined: Tue May 21, 2013 8:21 pm
Location: On The Tools

Re: custom ultegra 6800 50/36 crankset?

Postby Duck! » Thu May 21, 2015 4:53 pm

Youu can run a 10-sp. crank perfectly well in an 11-sp. system.
I had a thought, but it got run over as it crossed my mind.

User avatar
Xplora
Posts: 8272
Joined: Sat Dec 11, 2010 12:33 am
Location: TL;DR

Re: custom ultegra 6800 50/36 crankset?

Postby Xplora » Thu May 21, 2015 10:44 pm

The quality of the shift could be affected with the specific 6800 or 9000 rings, but the actual for 14t gaps is awesome.

User avatar
Duck!
Expert
Posts: 6338
Joined: Tue May 21, 2013 8:21 pm
Location: On The Tools

Re: custom ultegra 6800 50/36 crankset?

Postby Duck! » Thu May 21, 2015 11:23 pm

Xplora wrote:The quality of the shift could be affected with the specific 6800 or 9000 rings

Not really, the differences are in material (grades of aluminium), construction (bigger hollow in the Dura-Ace) & cosmetics. The functonal bits such as ramping are identical due to the matching chain profiles also being common between groupset levels.
I had a thought, but it got run over as it crossed my mind.

Who is online

Users browsing this forum: No registered users