Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

General Cycling Discussion Have a cycling related question or comment that doesn't fit in one of the other specialty forums? Drop on in and post in here! When possible, please select the forum above that most fits your post!

User Tag List

Reply
 
Thread Tools Search this Thread
Old 07-04-09, 01:25 PM   #1
greyhead
Newbie
Thread Starter
 
Join Date: Jul 2009
Bikes:
Posts: 3
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Chainwheel changes

I am planing to change chainwheels, (the granny at best) from a 30 to a 26 or 24T. The front derailluer os a Shimano 105. The rings are 52-42-30. What are the limits on the 105?

Greyhead
greyhead is offline   Reply With Quote
Old 07-04-09, 04:56 PM   #2
rdtompki
Senior Member
 
rdtompki's Avatar
 
Join Date: Nov 2008
Location: Hollister, CA
Bikes: Volagi, daVinci Joint Venture
Posts: 3,962
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I swapped the 30 on my wife's 50-39-30 for a 24t granny. You will want a chain keeper in any event, but based on our experience I would go with the 26t; a 42t to 24t seems like an awfully big shift. The 2008 version of the Shimano 105 FD did handle the 24T, but you could definitely drop the chain. Depending up your usage and your cassette you might consider a wider range cassette, at least up to what your RD will handle.
rdtompki is offline   Reply With Quote
Old 07-04-09, 07:08 PM   #3
BlazingPedals
Senior Member
 
BlazingPedals's Avatar
 
Join Date: Dec 2004
Location: Middle of da Mitten
Bikes: Trek 7500, RANS V-Rex, Optima Baron, Velokraft NoCom, M-5 Carbon Highracer, homebuilt recumbent
Posts: 9,082
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 157 Post(s)
The limiting factor will be the rear derailleur's capacity. A 105 triple FD should be able to handle 24 teeth difference. That's a 52/42/28T. More is possible, but it may depend on your seat tube angle and the cassette you're running. If you go beyond the derailleur's capacity, the chain will drag on the bottom of the cage. One of my recumbents is running a 30/44/56 with no problems.
BlazingPedals is online now   Reply With Quote
Old 07-04-09, 07:59 PM   #4
Nermal
Senior Member
 
Nermal's Avatar
 
Join Date: Jan 2006
Location: Farmington, NM
Bikes: Giant Cypress SX
Posts: 2,089
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
I made such a change. Don't recall how many teeth on the original chain ring, but we went to 24t first, and couldn't keep the chain on while downshifting. Went up to 26t, and a wide ratio cassette. It worked fine. There is a really big jump from middle to small chain ring, though. My perception is that shifting the FD one time is now like dropping two cogs on the cassette. It used to be two. Still, if you have some really steep hills, it's a solution.

The only problem has been that if you are in the small chain ring, you need to be in towards the largest cog in the rear. If you use the smallest cog, the jockey wheel is so far rearward that the the chain sort of doubles upon itself, and the chain is actually rubbing against another part of the chain. I can't say if this is common to all such modifications, or only mine.
__________________
Some people are like a Slinky ... not really good for anything, but you still can't help but smile when you shove them down the stairs.
Nermal is offline   Reply With Quote
Old 07-05-09, 02:42 AM   #5
stapfam
Time for a change.
 
stapfam's Avatar
 
Join Date: Jan 2004
Location: 6 miles inland from the coast of Sussex, in the South East of England
Bikes: Dale MT2000. Bianchi FS920 Kona Explosif. Giant TCR C. Boreas Ignis. Pinarello Fp Uno.
Posts: 19,915
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
The max teeth change recommended on a shimano front triple derailler is 22t. This can be stretched to 24- just about- but any more than that and you will have to be perfct in the set up of the derailler.

And a warning- Make certain that the chain ring you get is the same width and alignment as the one you are taking off. I fitted an "Incompatible" width on the Tandem once and the chain used to jam between the inner and middle rings.

But a member in a group I ride with has 50/39/24 fitted to his bike. He does not have any change problems- but he is carefull on changing without pressure on the pedals and derrailler alignment.

And if you run into R.Derailler cog problems as Nermal mentioned- You may have to change the rear derailler to a long cage form.
__________________
How long was I in the army? Five foot seven.


Spike Milligan

Last edited by stapfam; 07-05-09 at 02:45 AM.
stapfam is offline   Reply With Quote
Old 07-05-09, 03:24 AM   #6
Panthers007
Great State of Varmint
 
Panthers007's Avatar
 
Join Date: Sep 2008
Location: Dante's Third Ring
Bikes:
Posts: 7,479
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
My Shimano XTR FD is rated for a max. size of 44 - 48T chainring. I installed it anyways on my then-new Ultegra 52-39-30T crankset. It works flawlessly. My advice is to try it regardless of what the specs may say. I have see many other examples of Shimano specs being way off.

I know I'll be pounced on for saying this - but I'm just suggesting people to try. Then publish the results - Yay or Nay.
Panthers007 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 06:37 PM.