New rear cassette and chain is doing my head in.

Discuss light weight issues concerning road bikes & parts.
Post Reply
slick1
Posts: 211
Joined: Wed Nov 30, 2005 1:35 am

by slick1

Hi all. I have a slight problem and I don't really know where the exact issue lies.

I have a roadbike with 39/53 on the front and have installed a new 11/28 casette on the rear. I've calculated the chain wrap capacity to be 31.

The issue I'm having is that when I adjusted the new chain by putting the front onto the 39t and the rear on the 11t (worst case scenario for chain slack) and shorten the chain to suit, I can gear down to the 53/28t but when I do, the pedals lock up. My guess is that the chain is too short to be on the 53/28.

I then added extra links to the chain so I can go 53t on the front and 28t on the rear (even though I dont ride that combo but have done so accidentally) the chain has too much slack when I go to 39t and 11t on the rear.

I haven't checked my derailleur yet but I'm pretty sure it's a short cage. From what I've read, the short cage derailleur I have will accommodate a 11/28 rear cassette (chainwrap of 33 I think)

Has anybody got any advice on what I can try next?
Thanks

Sent from my GT-I9300 using Tapatalk

by Weenie


User avatar
BeeBee30
Posts: 1473
Joined: Sun Dec 21, 2003 8:32 pm
Location: WALES,UK
Contact:

by BeeBee30

I'm running that set up with no issues as I assume many others are. Two things spring to mind, is your rear mech springing back enough? maybe the pivot bolt is a little seized up? Or trying slackening off the B-tension screw, that will allow the mech to spring back more.
Ti or dye!

The Weenie formally known as CAADHEAD

slick1
Posts: 211
Joined: Wed Nov 30, 2005 1:35 am

by slick1

I took the derailleur off and made sure it wasn't seized. I haven't tried backing off the B tension screw but I will try rhat and let you know how it gows. Thanks for the advice.

Sent from my GT-I9300 using Tapatalk


Tenlegs
Posts: 273
Joined: Wed Jul 16, 2008 10:37 am

by Tenlegs

Chain length must be wrong, no other reason if the RD has a 33t capacity, in the small-small (39-11)
lower run of the chain should just be missing the RD cage like this, what RD are you running?
Image

slick1
Posts: 211
Joined: Wed Nov 30, 2005 1:35 am

by slick1

Thanks for your posts guys. I tried the link provided by Oswald and all is good now.

I am running a dura ace RD. I'll take a pic tonight of the RD position when in the 39/11 and 53/28. When in the 53/28 it doesn't jam up.

Sent from my GT-I9300 using Tapatalk

slick1
Posts: 211
Joined: Wed Nov 30, 2005 1:35 am

by slick1

Ok. Had another look at my setup tonight. I think that the chain might still be a link too long. If anybody has their ratios the same as mine, can you please measure your chain and I can do the same. In the ratio 39/11 the chain isn't completely slack but I think it could be a tad tighter.
Image

Image

Image

Image

Sent from my GT-I9300 using Tapatalk

slick1
Posts: 211
Joined: Wed Nov 30, 2005 1:35 am

by slick1

Also. I can't seem to get the RD pulley away any more from the 28t with the B adjuster. It is screwed all the way in.

Sent from my GT-I9300 using Tapatalk

desperado95219
Posts: 56
Joined: Wed Apr 08, 2009 7:49 pm

by desperado95219

The length of the chain isn't going to necessarily give you the answer you desire, because the chain stays will vary in length dependent on the make and size of the bike.

Oswald
Posts: 792
Joined: Thu Jan 08, 2004 10:11 pm

by Oswald

slick1 wrote:I tried the link provided by Oswald and all is good now.


Yep, Parktool website always comes in handy when you need to fix your bike. Whenever I have to fix something that I don't do very often, I check their site before I start working. :D

User avatar
743power
Shop Wrench
Posts: 745
Joined: Sat Nov 29, 2008 6:15 am
Location: Colorado

by 743power

the rd-7800 has a max cog size of 27t. This is obviously splitting hairs, but pair that with unknown hanger geometry; some bikes are shorter or longer then others; and that may be your problem with the pulley clearance. As far as length goes, you look right on. Another check you can do is put the bike in the 53/11 and see if the two pulleys are roughly perpindicular to the ground, if so you are good.
"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius -- and a lot of courage -- to move in the opposite direction."

eric
Posts: 2196
Joined: Tue Nov 11, 2003 9:47 pm
Location: Santa Cruz, California, USA
Contact:

by eric

That hanger looks pretty short. Maybe try an xx-27 cassette or use an RD-7900.

slick1
Posts: 211
Joined: Wed Nov 30, 2005 1:35 am

by slick1

Thanks @743power. I'll try it tonight.

I'm happy with the 11/28. I might upgrade to the 7900 RD. That will fix the problem I hope.

Sent from my GT-I9300 using Tapatalk

slick1
Posts: 211
Joined: Wed Nov 30, 2005 1:35 am

by slick1

Ok. I took some pics of the RD in the 53/11. The pulleys aren't directly in line. Looks like an additional link can come out.

Image

This picture is the RD position when I have selected 53/27 (worst case scenario for chain tension) with 1 less link. I did this by pulling the chain 1 link tighter when it was on the big chainring

Image


Sent from my iPad using Tapatalk

by Weenie


User avatar
743power
Shop Wrench
Posts: 745
Joined: Sat Nov 29, 2008 6:15 am
Location: Colorado

by 743power

I always prefer a longer chain. Puts less stress on the derailleur. The photo you posted previously of the bike in small small is the right length. If you are in that combo and their is tension on the derailleur cage but the chain is not running the tab in between the pulleys, you are at the right length. The latest photo in big big is still OK, but I would prefer one link longer.
"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius -- and a lot of courage -- to move in the opposite direction."

Post Reply
  • Similar Topics
    Replies
    Views
    Last post