Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

105 Triple to Double

Old 12-14-06, 07:54 AM
  #1  
sisham35
Biking Brewer
Thread Starter
 
Join Date: Jan 2006
Posts: 32
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
105 Triple to Double

I've been thinking about changing my 105 triple to a double. In the two years I've had this bike I think I've used the small chainring once for a short time. I think by making the change I will get more usable gears in the range I like with out crosschaining. My questions are: By putting on a double chainring will I move the centerline of the chainring closer to the bottom bracket to prevent crosschaining from say the big ring to the big sprocket? I know this isn't ideal, but that gear feels pretty good. I hope I'm explaining this right. If the centerline of the double stays the same distance away from the bottom bracket as the triple is now, I don't think it will make a difference. Second, will I still be able to use the same front derailuer?

Thanks,
Scott
sisham35 is offline  
Old 12-14-06, 08:11 AM
  #2  
sisham35
Biking Brewer
Thread Starter
 
Join Date: Jan 2006
Posts: 32
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I guess I should have said I want to replace the whole crankset.
sisham35 is offline  
Old 12-14-06, 08:12 AM
  #3  
TallRider
Senior Member
 
TallRider's Avatar
 
Join Date: Oct 2005
Location: Fresno, CA
Posts: 4,433
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 115 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Yup, it sounds like the switch to a double makes sense for you. As long as you have no plans to take the bike to some more hilly or mountainous area for riding. (I've got two nice road bikes now, one with a double crank, the other with a triple and somewhat higher handlebars. I'll use the latter if I ever go to western NC mountains for some weekend riding.)

On the chainline issue: standard chainlinefor a road triple crank is 45mm (measured from the centerline of the bike and seat tube to the middle chainring). Standard chainline for a road double is 43.5mm (measured to midway between the two chainrings). If you're switching to a double crank, you'll probably need to get the appropriate bottom bracket.
Shimano 105 double crank (5500) uses a 109.5mm Octalink bottom bracket, whereas the triple crank version uses a 118mm BB.

Also, you shouldn't use the big chainring to big sprocket combination. It's more of a problem with a triple crank (as the large chainring is further away from the bike's centerline) but still a problem with a road double. Unless you have really long chainstays. Really, really long chainstays.

You can keep the same rear derailler and front derailler, and it'll work fine. If you want to replace the deraillers to look appropriate with a double crank (this is more noticeable with the rear der, btw), you can do so. But it's not necessary.
TallRider is offline  
Old 12-14-06, 08:49 AM
  #4  
slantrock
Junior Member
 
Join Date: Dec 2006
Posts: 13
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I am also thinking about replacing my triple with a double, and I've heard that, in addition to a new BB, I'll also need new shifters. Is this true?

Thanks,
slantrock is offline  
Old 12-14-06, 09:14 AM
  #5  
San Rensho 
Senior Member
 
Join Date: Oct 2005
Posts: 5,655
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 136 Post(s)
Likes: 0
Liked 1 Time in 1 Post
You can use the same shifters, thats not a problem. As far as the front der goes, I had a 105 triple front that I just couldn't get to work right. Went to a double 105 front and it shifts like a charm. But, I am using an old Stronglight crank, not shimano.
__________________
Il faut de l'audace, encore de l'audace, toujours de l'audace

1980 3Rensho-- 1975 Raleigh Sprite 3spd
1990s Raleigh M20 MTB--2007 Windsor Hour (track)
1988 Ducati 750 F1
San Rensho is offline  
Old 12-14-06, 09:31 AM
  #6  
TallRider
Senior Member
 
TallRider's Avatar
 
Join Date: Oct 2005
Location: Fresno, CA
Posts: 4,433
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 115 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Yup, triple-compatible front shifter can work fine with a double, but double-only front shifters can't handle a triple. This should be intuitive.
San Rensho might be right about the front derailler, although I don't see a reason why a double front der. would work better on a double crank than a triple front der which spends at least 2/3 of its time shifting between the two largest rings anyway. But I don't have experience with this directly.
TallRider is offline  
Old 12-14-06, 10:03 AM
  #7  
TO11MTM
Senior Member
 
Join Date: Mar 2006
Posts: 387
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
+1 for not having to replace the shifters. Depending on which 105 version you have you might lose some trim adjustment but it is doubtful.

As an aside, depending on what cranks you have now you may want to look into the new Tiagra cranks... they look like they're going to be an absolute steal for what you'll get...
TO11MTM is offline  
Old 12-14-06, 10:12 AM
  #8  
slantrock
Junior Member
 
Join Date: Dec 2006
Posts: 13
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
"If you're switching to a double crank, you'll probably need to get the appropriate bottom bracket.
Shimano 105 double crank (5500) uses a 109.5mm Octalink bottom bracket, whereas the triple crank version uses a 118mm BB."

If I go from a 105 triple to an Ultegra double, would I still need the 109.5mm BB, or would I need a different BB?

Also, I currently have a 9-speed 12-25 cassette. What are your thoughts on riding a 9-speed double? Should I buy a 10-speed double and get a new cassette to match? My suspicion is that I won't need a 10-speed since I don't use the triple now and I am comfortable with my gearing. What's the difference between a 9 and 10-speed double ring? Is it just the spacing between the rings?

Thanks,
RAS
slantrock is offline  
Old 12-14-06, 10:28 AM
  #9  
TallRider
Senior Member
 
TallRider's Avatar
 
Join Date: Oct 2005
Location: Fresno, CA
Posts: 4,433
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 115 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Don't worry about going 10-speed, unless you want 10-speed for its own sake. If you want a slightly lower gear you can get 12-27 9-speed cassettes, but I'd recommend you just ride the 12-25 for awhile and see if you ever find yourself wanting a lower gear. It'll cost you a lot of money to update to 10-speed.

On cranks, specify what sort of crank/bb you'll be using. There's square-taper, Octalink and integrated crank/bb systems. New 105, Ultegra and Dura Ace are all integrated (what Shimano calls Hollowtech II) designs. Last year's 105 was Octalink, and Ultegra was Octalink a couple of years ago. I think the switch to an integrated crank/bb system coincided with the move to 10-speed.
Btw, Ultegra triple and double octalink cranks took same bottom bracket lengths as 105 octalink cranks.
TallRider is offline  
Old 12-14-06, 10:50 AM
  #10  
Steev
Senior Member
 
Steev's Avatar
 
Join Date: Jul 2005
Location: Backwoods of Ontario
Posts: 2,152
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by slantrock
Also, I currently have a 9-speed 12-25 cassette. What are your thoughts on riding a 9-speed double? Should I buy a 10-speed double and get a new cassette to match? My suspicion is that I won't need a 10-speed since I don't use the triple now and I am comfortable with my gearing. What's the difference between a 9 and 10-speed double ring?
There is minimal difference between a 9 and a 10 speed crank, I believe the chainring spacing is slightly closer on the 10's, but functionally, there is no difference.
Steev is offline  
Old 12-14-06, 10:52 AM
  #11  
TallRider
Senior Member
 
TallRider's Avatar
 
Join Date: Oct 2005
Location: Fresno, CA
Posts: 4,433
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 115 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by Steev
There is minimal difference between a 9 and a 10 speed crank, I believe the chainring spacing is slightly closer on the 10's, but functionally, there is no difference.
Yeah, a 9-speed crank will work fine with 10-speed.
Cranks designed for 8-speed will work fine with 9-speed, though I'm not sure about 8-to-10.
TallRider is offline  
Old 12-14-06, 11:02 AM
  #12  
idcruiserman
Mmmmm potatoes
 
idcruiserman's Avatar
 
Join Date: Sep 2006
Location: Idaho
Posts: 1,921
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I just went through this with my cross bike. I had a std double with 9 speed rear (all 105). I replaced the RD and cassette and then decided to go with a compact crank and needed a new brifter. I would have gone 10 speed if I'd done things the other way around .

No problems running a 10 speed compact double crank with 9 speed rear, but all my parts are new.
idcruiserman is offline  
Old 12-14-06, 01:16 PM
  #13  
dbg
Si Senior
 
dbg's Avatar
 
Join Date: Nov 2004
Location: Naperville, Illinois
Posts: 2,669

Bikes: Too Numerous (not)

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 22 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Sorry to be the curmudgeon here, but why not just don't use the granny and leave everything as is. And if you're currently running 52-42-30 and want standard double gearing, couldn't you just swap in a 39 for the 42 and change nothing else. That way you'll still be ready when the invitation for a week long tour through the mountains comes in and you realize you're glad you still have that extra low range for that late afternoon pull over the pass with the loaded tank bag.
dbg is offline  
Old 12-14-06, 01:52 PM
  #14  
sisham35
Biking Brewer
Thread Starter
 
Join Date: Jan 2006
Posts: 32
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
The roads here in Michigan are pretty flat. At the most, very small rolling hills. Those 4 or 5 gears you can use in the small ring don't really get you anywhere. So, I know I'll need a new BB to make the switch, what about a new front derailuer? Can I use my old 3 chainring 105?
sisham35 is offline  
Old 12-14-06, 02:36 PM
  #15  
TallRider
Senior Member
 
TallRider's Avatar
 
Join Date: Oct 2005
Location: Fresno, CA
Posts: 4,433
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 115 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by sisham35
The roads here in Michigan are pretty flat. At the most, very small rolling hills. Those 4 or 5 gears you can use in the small ring don't really get you anywhere. So, I know I'll need a new BB to make the switch, what about a new front derailuer? Can I use my old 3 chainring 105?
I grew up in Holland, MI, and my parents moved to the "thumb" (to Harbor Beach) while I was in college. I used my granny ring all of three times in all of the riding I've done in Michigan, and each time I could have comfortably powered up the hill in the middle chainring if I was comfortable accessing the largest cogs, which I didn't do in the middle ring of the triple because of chainline.
So: I fully support your decision to go with a double crank. Unless you plan to do rides in NW Michigan where it's quite hilly.

Even here in Chapel Hill, NC, a 36/26 (middle ring plus large cog combo, which I still don't use because of chainline) would be plenty low gear for the vast majority of riding that I do here. My fast bike is eventually getting a 50/34 compact double to combine with a 12-26 9-speed cassette, whereas I'll keep another bike built up with a triple and with higher handlebars for longer, more comfortable rides, and for whenever I go to western NC for a weekend for rides in the mountains and along the Blue Ridge Parkway and such.
Triples are wonderfully useful in the mountains. In October I visited my sister, who works in Yosemite, and her boyfriend had a bike that's big enough for me, with a 46/36/26 triple and 11-24 7-speed cassette. Was great for riding around there: I used the inner chainring for extended up, the big ring for extended down, and the middle chainring for fluctuating (relative) flat areas.
TallRider is offline  
Old 12-15-06, 12:47 PM
  #16  
DMF 
Elitist Troglodyte
 
DMF's Avatar
 
Join Date: Jun 2006
Location: Dallas
Posts: 6,926

Bikes: 03 Raleigh Professional (steel)

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by slantrock
If I go from a 105 triple to an Ultegra double, would I still need the 109.5mm BB, or would I need a different BB?
Yes, a 109.5.

In fact, you might consider doing that with the triple. It will pull the chainline of the big rings in to where a double would be, giving you less cross-chaining. You then should be able to use the front limit screws to keep the chain on just those two.
__________________
Stupidity got us into this mess - why can't it get us out?

- Will Rogers
DMF is offline  
Old 12-15-06, 12:54 PM
  #17  
DMF 
Elitist Troglodyte
 
DMF's Avatar
 
Join Date: Jun 2006
Location: Dallas
Posts: 6,926

Bikes: 03 Raleigh Professional (steel)

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by dbg
Sorry to be the curmudgeon here, but why not just don't use the granny and leave everything as is.
I agree.

It's like having a 6-speed transmission and wanting to swap for a 5-speed because you never drive fast enough to use sixth gear. Pointless.

Btw, shisham, you do know that you can trim the front dérailleur when it makes chain contact, right? With a triple you may lose four gears to cross-chaining, only two of which are on the top rings. Switching to a double you'll get only one of those two back while losing another. Net gain is zero.
__________________
Stupidity got us into this mess - why can't it get us out?

- Will Rogers
DMF is offline  
Old 12-15-06, 05:46 PM
  #18  
sisham35
Biking Brewer
Thread Starter
 
Join Date: Jan 2006
Posts: 32
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I'm starting to agree. I have a hell of a time using the trim though. Sometimes I have to push so hard it downshifts to a smaller ring instead of trimming, other times it's not a problem. Is there a way to adjust the trim or is it just a matter of touch?
sisham35 is offline  
Old 12-15-06, 05:55 PM
  #19  
Phantoj
Certifiable Bike "Expert"
 
Join Date: May 2005
Posts: 5,647
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I used to think like the posters above... then I got a triple and found out its limitations.

I have a 105 double setup and a 105 triple setup. If I didn't use the granny ring, I would strongly prefer the double. There's no point in having that little granny ring taking up the prime chainline real estate.
Phantoj is offline  
Old 12-15-06, 05:58 PM
  #20  
barba
Senior Member
 
barba's Avatar
 
Join Date: Nov 2005
Posts: 4,083
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Phantoj
I used to think like the posters above... then I got a triple and found out its limitations.

I have a 105 double setup and a 105 triple setup. If I didn't use the granny ring, I would strongly prefer the double. There's no point in having that little granny ring taking up the prime chainline real estate.
I would tend to agree, but would take it as a lesson to buy a double on my next bike rather than spend money on the current one to switch to a double from a triple.
barba is offline  
Old 12-15-06, 06:15 PM
  #21  
sisham35
Biking Brewer
Thread Starter
 
Join Date: Jan 2006
Posts: 32
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Nashbar has a sale right now on a double 105 crankset and a new bottom bracket for about 85$ plus free shipping. That's a pretty good deal, that's why I've been thinking about doing this.
sisham35 is offline  
Old 12-15-06, 09:35 PM
  #22  
TallRider
Senior Member
 
TallRider's Avatar
 
Join Date: Oct 2005
Location: Fresno, CA
Posts: 4,433
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 115 Post(s)
Likes: 0
Liked 1 Time in 1 Post
If you never use the granny ring, I would actually strongly recommend (for reasons articulated above) that you convert to a double, provided you can do it without much cost. Biggest reasons are simplicity and chainline. But don't just do it because you can get something cheap at Nashbar. (Although, you can actually do cheaper than the 105 at Nashbar, if you don't mind going for something used on eBay.)

I don't think that DMF's analogy of swapping a six-speed transmission for a 5-speed because you don't us the 6th gear is a valid comparison, unless the sixth gear added weight and complicated the drivetrain.
TallRider is offline  
Old 12-15-06, 09:42 PM
  #23  
sisham35
Biking Brewer
Thread Starter
 
Join Date: Jan 2006
Posts: 32
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I didn't want to imply I just doing this because it's cheap. To me the small ring is useless, when there's not a hill within hours of me.
sisham35 is offline  
Old 12-15-06, 10:07 PM
  #24  
DieselDan
Senior Member
 
DieselDan's Avatar
 
Join Date: Mar 2003
Location: Beaufort, South Carolina, USA and surrounding islands.
Posts: 8,522

Bikes: Cannondale R500, Motobecane Messenger

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
If you are switching to a new Shimano 10-speed crankset, don't worry about changing the BB, as they all use outboard bearings that you will have to buy.
DieselDan is offline  
Old 12-16-06, 06:57 AM
  #25  
TallRider
Senior Member
 
TallRider's Avatar
 
Join Date: Oct 2005
Location: Fresno, CA
Posts: 4,433
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 115 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by sisham35
I didn't want to imply I just doing this because it's cheap. To me the small ring is useless, when there's not a hill within hours of me.
No I think it's worth doing in your case anyway, because you never use the small ring and it adds weight and changes the chainline unnecessarily. It sounds like you have reason beyond it just being pretty cheap.
TallRider is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.