Go Back  Bike Forums > Bike Forums > Classic & Vintage
Reload this Page >

Baffled by decaleurs

Notices
Classic & Vintage This forum is to discuss the many aspects of classic and vintage bicycles, including musclebikes, lightweights, middleweights, hi-wheelers, bone-shakers, safety bikes and much more.

Baffled by decaleurs

Old 12-23-19, 09:07 PM
  #1  
jonwvara 
Senior Member
Thread Starter
 
jonwvara's Avatar
 
Join Date: Apr 2006
Location: Washington County, Vermont, USA
Posts: 3,299

Bikes: 1966 Dawes Double Blue, 1976 Raleigh Gran Sport, 1975 Raleigh Sprite 27, 1980 Univega Viva Sport, 1971 Gitane Tour de France, 1984 Lotus Classique, 1976 Motobecane Grand Record

Mentioned: 57 Post(s)
Tagged: 0 Thread(s)
Quoted: 502 Post(s)
Liked 224 Times in 122 Posts
Baffled by decaleurs

As a C&V bike tourist, I'm always on the lookout for ever-more stylish, expensive, and complicated methods of mounting bags on my bikes. That has inevitably led me to consider one of those tall handlebar bags that are supported by a small rack below and a decaleur above. There's no arguing with their general French coolness (Randonneur! Constructeur! Decaleur! Look at all those -eur words!), but I'm kind of confused as to how they actually work.

Two questions (I think I know the answer to the first one, but I think I know the answers to a lot of things that I turn out not to):

First, when it comes to the effect of a load on a bike's handling, does it matter where the load is attached, or just the position of the load itself? In other words, a 6-lb load in one of those 1970s handlebar bags that mounts up high, on a metal-rod frame that fits over the stem and handlebars, is going to have a pretty pronounced effect on handling. If you mount that same bag and 6-pound load on a platform front rack right over the wheel, it's going to have a much smaller effect. I know that much from experience.

But if you were to position the same load on a front rack but partially supported by a decaleur, will it behave identically to the same load supported completely by the rack? Or does the fact that part of the load is supported by the decaleur raise the effective center of gravity, even though the bag itself is in the same position as the entirely-rack-supported bag? Does that question even make sense?

My hypothesis is that it's only the position that matters. But maybe there's more to it.

Secondly, how does one go about distributing the weight of a load between rack and decaleur? Depending on how high or low one drills the decaleur-mount holes in the bag, it seem to me that it would be quite possible to create a situation is which the bottom of the bag just barely grazes the front rack, with almost all of the load carried by the decaleur. Alternatively, it would seem possible to mount it in such a way that virtually all of the weight is borne by the rack, with the decaluer doing nothing more than preventing the upper part of the bag from flopping around.

Is that the case? Or through some sort of mystic Frenchness, does the load always somehow get divided 50-50 between bag and decaleur? And if not, does it matter?

Sorry to be so long-winded. This is quite possibly the kind of thing that becomes immediately obvious once you lay hands on it. Not sure when I'll do that, though.
__________________
www.redclovercomponents.com

"Progress might have been all right once, but it has gone on too long."
--Ogden Nash
jonwvara is offline  
Likes For jonwvara:
Old 12-23-19, 10:08 PM
  #2  
mpetry912 
aged to perfection
 
mpetry912's Avatar
 
Join Date: Jun 2009
Location: PacNW
Posts: 459

Bikes: Dinucci Allez 2.0, Richard Sachs, Alex Singer, Serotta, Masi GC, Raleigh Pro Mk.1, Hetchins, etc

Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 198 Post(s)
Liked 123 Times in 91 Posts
This is a really good question.i

Bikes that were built with a handlebar bag in mind seem to have pretty neutral response to loading. Having said that, I'd suggest that lightweight stuff (jacket, power bar, phone) go in the handlebar bag and heavier stuff go into panniers on the rear wheel.

Bearing the above in mind, you should not have to worry about distribution of weight between the decaleur and the rack. The decaleur is there to stabilize the load, and the rack takes the weight.

Again, heavier stuff goes in the back.

Mark Petry
Bainbridge Island, WA USA


mpetry912 is offline  
Likes For mpetry912:
Old 12-23-19, 11:53 PM
  #3  
TenGrainBread 
Senior Member
 
TenGrainBread's Avatar
 
Join Date: Sep 2015
Location: Madison, WI
Posts: 2,589

Bikes: Cherubim, Alps, a few Schwinns

Mentioned: 52 Post(s)
Tagged: 0 Thread(s)
Quoted: 1070 Post(s)
Liked 392 Times in 251 Posts
The position of the weight is the only thing that matters regarding handling. Where the attachment points are does not affect handling. The bag is fixed in position regardless of how it is mounted. The proximity of the bag to the steering axis and center of gravity affect the handling.

As far as ideal weight distribution between rack and decaleur, the rack should take most of the weight. The purpose of the decaleur is to stop the bag from moving and falling off the rack (aka stabilize). Whenever I build a decaleur I try to position it so that the bag has some sag over the rack so that the decaleur isn't holding the back off the rack.

Last edited by TenGrainBread; 12-23-19 at 11:58 PM.
TenGrainBread is offline  
Old 12-24-19, 11:43 AM
  #4  
gugie 
Dilberteur at large
 
gugie's Avatar
 
Join Date: Jul 2014
Location: Portland, OR
Posts: 9,038

Bikes: It's complicated.

Mentioned: 988 Post(s)
Tagged: 0 Thread(s)
Quoted: 3167 Post(s)
Liked 1,403 Times in 719 Posts
Originally Posted by mpetry912 View Post
This is a really good question.

Bikes that were built with a handlebar bag in mind seem to have pretty neutral response to loading. Having said that, I'd suggest that lightweight stuff (jacket, power bar, phone) go in the handlebar bag and heavier stuff go into panniers on the rear wheel.

Bearing the above in mind, you should not have to worry about distribution of weight between the decaleur and the rack. The decaleur is there to stabilize the load, and the rack takes the weight.

Again, heavier stuff goes in the back.

Mark Petry
Bainbridge Island, WA USA
As Mark noted, the decaleur is there to stabilize the load - it stops the bag from wagging left and right. Properly designed it won't take any vertical weight.

I'll be the contrarian on weight distribution. The rear wheel already has more than half the weight on a bike on it just from the rider. Try standing on the pedals uphill with a full rear panniers - there's the "tail wagging the dog" syndrome; it's hard to keep a straight line like that. To counteract the twisting forces on a frame, many bike designers design heavier gauge or larger diameter tubing, which deadens the ride. The Surly Long Haul Trucker is the best example of this genre. It's been said it rides the same loaded or unloaded - dead.

I like riding a light, lively frame, even when touring. If I'm credit card touring, my kit won't fit into just a handlebar bag, about 5-6 pounds goes into a saddle bag, about 8-10 goes into my handlebar bag. If I'm camping with tent, sleeping bag and cooking kit I forego the saddle bag and use low riders, and all the extra weight goes up front. The enabler is low trail.

Here's a pic of 10 bikes on the way to un-meeting 2016. All of us were going to be camping. Eight of the ten have most or all of the kit loaded in the front. Riding uphill on the zero-shoulder Columbia River Highway I could stand and pedal without wobbling from side to side.



Heavier stuff goes in the front when I ride on my low trail bikes. If you have a high trail bike, yep, keep the heavy stuff out of the front. It'll mess with your handling.
__________________
If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.
gugie is offline  
Likes For gugie:
Old 12-24-19, 12:46 PM
  #5  
gugie 
Dilberteur at large
 
gugie's Avatar
 
Join Date: Jul 2014
Location: Portland, OR
Posts: 9,038

Bikes: It's complicated.

Mentioned: 988 Post(s)
Tagged: 0 Thread(s)
Quoted: 3167 Post(s)
Liked 1,403 Times in 719 Posts
Originally Posted by TenGrainBread View Post
Whenever I build a decaleur I try to position it so that the bag has some sag over the rack so that the decaleur isn't holding the back off the rack.
Ditto!

More thoughts: traditional racks designed for handlebar bags have a "tombstone" or "backstop" built in. Handlebar bags designed for this have a strap in the back that the tombstone slides up into. The angle of the tombstone matches the head tube (~73 degrees).




A traditional decaleur has a set of pins and receivers and are angled perpendicular to the road. This mismatch helps keep the bag from flying off on bumpy roads. If you hit a bump, the bag moves up along the tombstone angle, but the decaleur constrains the bag to only a "straight up" trajectory, with the result that the bag "tightens" up on the system. You notice this when you take the bag on and off the bike - you have to bend the bag a bit to get it on or off.


pic courtesy of Eric Langley
__________________
If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.
gugie is offline  
Old 12-24-19, 12:54 PM
  #6  
mpetry912 
aged to perfection
 
mpetry912's Avatar
 
Join Date: Jun 2009
Location: PacNW
Posts: 459

Bikes: Dinucci Allez 2.0, Richard Sachs, Alex Singer, Serotta, Masi GC, Raleigh Pro Mk.1, Hetchins, etc

Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 198 Post(s)
Liked 123 Times in 91 Posts
Alright, so I agree on the low rider thing - esp. positioning the load so it is neutral to the fork axis of rotation.

is there a rule or formula for the ideal trail measurement when a front bag / decaleur combo is part of the design ?

Here is why I ask the question. I've owned several Alex Singer touring bikes and twice - twice - I have managed to steer myself out of a "for sure" wipeout when the front tire slid on wet or oily pavement. One of those times I was leaned over where I knew I was going down ! and was able to recover it. BOTH of those bikes were front bag / decaleur equipped "by design".

What do they know that we don't ?

Mark Petry
Coronado Island, CA
mpetry912 is offline  
Old 12-24-19, 01:37 PM
  #7  
jonwvara 
Senior Member
Thread Starter
 
jonwvara's Avatar
 
Join Date: Apr 2006
Location: Washington County, Vermont, USA
Posts: 3,299

Bikes: 1966 Dawes Double Blue, 1976 Raleigh Gran Sport, 1975 Raleigh Sprite 27, 1980 Univega Viva Sport, 1971 Gitane Tour de France, 1984 Lotus Classique, 1976 Motobecane Grand Record

Mentioned: 57 Post(s)
Tagged: 0 Thread(s)
Quoted: 502 Post(s)
Liked 224 Times in 122 Posts
Originally Posted by gugie View Post
As Mark noted, the decaleur is there to stabilize the load - it stops the bag from wagging left and right. Properly designed it won't take any vertical weight.

I'll be the contrarian on weight distribution. The rear wheel already has more than half the weight on a bike on it just from the rider. Try standing on the pedals uphill with a full rear panniers - there's the "tail wagging the dog" syndrome; it's hard to keep a straight line like that. To counteract the twisting forces on a frame, many bike designers design heavier gauge or larger diameter tubing, which deadens the ride. The Surly Long Haul Trucker is the best example of this genre. It's been said it rides the same loaded or unloaded - dead.

I like riding a light, lively frame, even when touring. If I'm credit card touring, my kit won't fit into just a handlebar bag, about 5-6 pounds goes into a saddle bag, about 8-10 goes into my handlebar bag. If I'm camping with tent, sleeping bag and cooking kit I forego the saddle bag and use low riders, and all the extra weight goes up front. The enabler is low trail.

Here's a pic of 10 bikes on the way to un-meeting 2016. All of us were going to be camping. Eight of the ten have most or all of the kit loaded in the front. Riding uphill on the zero-shoulder Columbia River Highway I could stand and pedal without wobbling from side to side.



Heavier stuff goes in the front when I ride on my low trail bikes. If you have a high trail bike, yep, keep the heavy stuff out of the front. It'll mess with your handling.
I know almost nothing about trail, frame angles, and all that stuff. But this thread is connected with my plan to go on a lightly-loaded four or five day tour with my PX-10, which I understand has a reputation for having lots of trail. It's not the bike I'd ordinarily tour on, but I'm bound for Eroica so the PX-10 seems like a logical fit for the event.

I'm going to go really light for a camping tour--basically just the clothes I'll be wearing, a super-light down jacket, light down quilt, foam pad, and bivy sack. So no panniers, front or rear (I ordinarily use only front panniers--I don't even own a set of rears). I'm figuring that most of the stuff will go in my Carradice Camper saddlebag. No doubt there will be a little overflow, which I guess will go into a Jannd handlebar bag (originally designed for stem mounting) that I plan to reconfigure so it mounts on one of the old Blackburn platform front racks to keep the weight low. Hoping to keep the total load to 15 lbs or less, with no more than 5 in the front bag. Based on what people have said here, that seems like a better option than a larger handlebar bag.

EDIT: I should have mentioned that I'll only be riding from San Francisco to Cambria, not all the way across from Vermont, more's the pity. I would need panniers in that case.
__________________
www.redclovercomponents.com

"Progress might have been all right once, but it has gone on too long."
--Ogden Nash

Last edited by jonwvara; 12-24-19 at 01:41 PM.
jonwvara is offline  
Old 12-24-19, 02:25 PM
  #8  
gugie 
Dilberteur at large
 
gugie's Avatar
 
Join Date: Jul 2014
Location: Portland, OR
Posts: 9,038

Bikes: It's complicated.

Mentioned: 988 Post(s)
Tagged: 0 Thread(s)
Quoted: 3167 Post(s)
Liked 1,403 Times in 719 Posts
Originally Posted by mpetry912 View Post
Alright, so I agree on the low rider thing - esp. positioning the load so it is neutral to the fork axis of rotation.

is there a rule or formula for the ideal trail measurement when a front bag / decaleur combo is part of the design ?

Here is why I ask the question. I've owned several Alex Singer touring bikes and twice - twice - I have managed to steer myself out of a "for sure" wipeout when the front tire slid on wet or oily pavement. One of those times I was leaned over where I knew I was going down ! and was able to recover it. BOTH of those bikes were front bag / decaleur equipped "by design".

What do they know that we don't ?

Mark Petry
Coronado Island, CA
"Several" Alex Singer touring bikes?
__________________
If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.
gugie is offline  
Likes For gugie:
Old 12-24-19, 02:37 PM
  #9  
repechage
Senior Member
 
Join Date: Jun 2006
Posts: 15,448
Mentioned: 102 Post(s)
Tagged: 0 Thread(s)
Quoted: 1726 Post(s)
Liked 612 Times in 475 Posts
Originally Posted by gugie View Post
"Several" Alex Singer touring bikes?
Some are twice blessed.
repechage is offline  
Old 12-24-19, 02:40 PM
  #10  
repechage
Senior Member
 
Join Date: Jun 2006
Posts: 15,448
Mentioned: 102 Post(s)
Tagged: 0 Thread(s)
Quoted: 1726 Post(s)
Liked 612 Times in 475 Posts
My thought on thefront bag system, is that bikes with a handlebar bag in mind often have lower trail. The rack imaged by @gugie does show a solution I like as well as it helps the bag from shifting around.
Still needs some restraint up top.
repechage is offline  
Old 12-24-19, 03:00 PM
  #11  
gugie 
Dilberteur at large
 
gugie's Avatar
 
Join Date: Jul 2014
Location: Portland, OR
Posts: 9,038

Bikes: It's complicated.

Mentioned: 988 Post(s)
Tagged: 0 Thread(s)
Quoted: 3167 Post(s)
Liked 1,403 Times in 719 Posts
anti-eject decaleurs

Originally Posted by repechage View Post
Still needs some restraint up top.
Indeed. Even with this designed-in way of keeping a bag from self-ejecting, it can still happen. To make it truly eject-proof, there are several solutions.

Compass Rene Herse decaleur with locking device:



RaClips from Waxwing bags



"Ortlieb hack" decaleur, an idea I stole from Ocean Air Cycles


I've also seen velcro used to attach the bag to the rack.



__________________
If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.
gugie is offline  
Old 12-24-19, 03:16 PM
  #12  
repechage
Senior Member
 
Join Date: Jun 2006
Posts: 15,448
Mentioned: 102 Post(s)
Tagged: 0 Thread(s)
Quoted: 1726 Post(s)
Liked 612 Times in 475 Posts
Waxwing bags look decent. I forgot about those.
repechage is offline  
Old 12-24-19, 04:00 PM
  #13  
palincss
Senior Member
 
Join Date: May 2017
Posts: 406
Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Liked 26 Times in 13 Posts
The decaleur stabilizes the top of the bag. It doesn't support the load.
palincss is offline  
Likes For palincss:
Old 12-24-19, 04:02 PM
  #14  
natterberry 
Senior Member
 
natterberry's Avatar
 
Join Date: Sep 2017
Location: Springfield, IL
Posts: 643

Bikes: 83/85 Trek 760, 82 Trek 614, 77/78 Trek 304, 74 Raleigh International

Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 263 Post(s)
Liked 173 Times in 114 Posts
I have a Waxwing bag, and ordered the raclips and Dock-It decaleur. I can take pictures of that setup Thursday.
natterberry is offline  
Old 12-24-19, 05:53 PM
  #15  
jdawginsc 
Edumacator
 
Join Date: Jan 2018
Location: Goose Creek, SC
Posts: 1,503

Bikes: '87 Crestdale, '87 Basso Gap, '92 Rossin Performance EL-OS, Faggin Matrix thingy

Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 443 Post(s)
Liked 345 Times in 229 Posts
Just going from an article I read in Bicycling magazine YEARS ago... I think I remember the formula for weight distribution was something like 50/20/30 (front pannier/handlebar bag/rear panniers+rack sackage). I think the article also said that handlebar bags were actually handling killers, except when panniers were also in the front.
jdawginsc is offline  
Likes For jdawginsc:
Old 12-24-19, 06:41 PM
  #16  
gugie 
Dilberteur at large
 
gugie's Avatar
 
Join Date: Jul 2014
Location: Portland, OR
Posts: 9,038

Bikes: It's complicated.

Mentioned: 988 Post(s)
Tagged: 0 Thread(s)
Quoted: 3167 Post(s)
Liked 1,403 Times in 719 Posts
Originally Posted by jdawginsc View Post
Just going from an article I read in Bicycling magazine YEARS ago... I think I remember the formula for weight distribution was something like 50/20/30 (front pannier/handlebar bag/rear panniers+rack sackage). I think the article also said that handlebar bags were actually handling killers, except when panniers were also in the front.
I'm pretty sure that Bicycling magazine actually invented the "horizontally stiff, vertically compliant" mantra.
__________________
If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.
gugie is offline  
Old 12-25-19, 09:15 AM
  #17  
TenGrainBread 
Senior Member
 
TenGrainBread's Avatar
 
Join Date: Sep 2015
Location: Madison, WI
Posts: 2,589

Bikes: Cherubim, Alps, a few Schwinns

Mentioned: 52 Post(s)
Tagged: 0 Thread(s)
Quoted: 1070 Post(s)
Liked 392 Times in 251 Posts
Originally Posted by jdawginsc View Post
Just going from an article I read in Bicycling magazine YEARS ago... I think I remember the formula for weight distribution was something like 50/20/30 (front pannier/handlebar bag/rear panniers+rack sackage). I think the article also said that handlebar bags were actually handling killers, except when panniers were also in the front.
Not sure how there could be a "formula" that exact without taking into account variation in design and geometry between bikes.

Most things written in Bicycling should be taken with a spoonful of salt...
TenGrainBread is offline  
Old 12-25-19, 10:32 AM
  #18  
rhm
multimodal commuter
 
rhm's Avatar
 
Join Date: Nov 2006
Location: NJ, NYC, LI
Posts: 19,600

Bikes: 1940s Fothergill, 1959 Allegro Special, 1963? Claud Butler Olympic Sprint, Lambert 'Clubman', 1974 Fuji "the Ace", 1976 Holdsworth 650b conversion rando bike, 1983 Trek 720 tourer, 1984 Counterpoint Opus II, 1993 Basso Gap, 2010 Downtube 8h, and...

Mentioned: 520 Post(s)
Tagged: 0 Thread(s)
Quoted: 1781 Post(s)
Liked 273 Times in 184 Posts
The lightweight racing bike is a certain aesthetic ideal. Clean lines, skinny tires, nothing attached to the bike except a frame pump and maybe a tiny little tool bag under the seat, and maybe a tubular tire. If that's your ideal, then an accessory like a decaleur is going to seem bizarre, if not downright perverse.

The thing is, a decaleur may look like an accessory you attach to a bike, but it makes sense only as a part of an integrated system. Obviously that system includes a bag and a rack, but it doesn't stop there-- or should I say, it didn't start there. The weight on the front wheel, turning with the rest of the front end, throws off the handing of the bike unless the frame was designed for it.

Hence gugifacazione.
__________________
www.rhmsaddles.com.
rhm is offline  
Old 12-25-19, 03:50 PM
  #19  
palincss
Senior Member
 
Join Date: May 2017
Posts: 406
Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Liked 26 Times in 13 Posts
Originally Posted by jdawginsc View Post
Just going from an article I read in Bicycling magazine YEARS ago... [snip] I think the article also said that handlebar bags were actually handling killers, except when panniers were also in the front.
True for certain front end geometries, most definitely not true for others. Of course, even though this was known as far back as the 1930s we forgot it by the time the Bike Boom rolled around, and didn't rediscover it until the turn of the new century.
palincss is offline  

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


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.