crazyguyonabike 
Topic: Bicycle Touring [change]
About  Help  FAQ  Sitemap  Options  Sponsors  Donate 

  Co-Motion Americano Rohloff Touring Bicycle - Unmatched frame reliability with the amazing Rohloff Speed hub's 14 internal gears!
www.co-motion.com
  
  Schwalbe Marathon MONDIAL
expedition touring specialist
www.wallbike.com
  
  CRAZYGUY T-SHIRTS, HOODIES, MUGS, AND MORE - Crazy Guy on a Bike merchandise at Zazzle. All profits go to support CGOAB.
www.zazzle.com
  
  Free Trial Adventure Cycling Membership - Never been a member? For a limited time click here for a FREE trial 6-month trial membership.
www.adventurecycling.org
  

 Home  My  Journals*  Articles*  Forums*   Reviews*  Resources*  Classifieds*  Serendipity  Ratings*  Directory  Search  Website
 Post  Polls

First Prev Next Last (page 1 of 1) Page 1

Forum: Components

Derailleurs, hubs, gears, brakes etc

View thread: Chronological Nested
    
View forum: Messages Threads

#1: V Brakes for Thorn tandem (thread)
By Mike Ayling on Sun 30 Sep 2012 23:31 (US/Pacific) Edit Delete   Reply (5)   Printable Relation | Link | Bookmark | Report
Thorn do not offer a disc brake option for the primary braking system for reasons outlined in their website but you can have one as a drag brake on your Rohloff hub.
Their standard spec is for Shimano Deore V brakes but of course you can upgrade to Shimano XT V brakes for another 35 quid.

Opinions please as to whether the upgrade is worthwhile or if we accept the base option what after market brakes should we consider after we have taken delivery of the bike.

Mike

      
#2: Re: V Brakes for Thorn tandem (thread)
By Emma Taylor on Mon 1 Oct 2012 03:38 Edit Delete in reply to #1     Reply   Printable Relation | Link | Bookmark | Report
Not on a tandem but Thorn Nomad Mk II's ...

Whilst we were not on a tandem, we did upgrade the brakes to the Shimano XT V brakes and also the rims to the Andora 30 CSS rims - the result was fantastic and fully laden the Nomad mk ii we have still outbrake our basic road bikes with them unladen (which is something I am now working on). As for weight - we never found a single person who could lift my husband's bike completely off the ground and many men tried. Inital set of pads lasted 7,000km before replacement; 2nd set are still going and show very little wear.

Our opinion is that the upgrade is worthwhile, but as an aside you can save a little money by upgrading the actually brakes but keeping the Deore levers which is what we did on my bike becuase I found the Deore levers easier than the XT V levers (but I have left hand issues).

      
#3: Re: V Brakes for Thorn tandem (thread)
By Dave & Jo Whitney on Mon 1 Oct 2012 05:48 Edit Delete in reply to #1     Reply (1)   Printable Relation | Link | Bookmark | Report
Mike,

I'm here again. My short answer is go for the best upgrade you can afford. We went for Shimano XTR V brakes and quite honestly they are in my humble opinion the best V brakes out there - end of story. We had the Rohloff option of fitting a disc brake but decided to forgo that and see how we went on. Needless to say it never got fitted.

The important thing is get the best type of rims to go with the brakes. We have a Mavic ceramic front rim and as mentioned on the other post the Rigida Andra on the rear with the CSS rim coating. This braking combination is just fantastic, in wet or dry, even when fully loaded. I can recall one or two emergency stops when such has been the suddenness of coming to a stop Jo has been out of her seat and halfway up my back, with some complaints of course.

Think of it like the difference in the braking requirements of a car against the requirements of stopping a truck! You need better quality and stronger brakes on a tandem.

Dave

      
#4: Re: V Brakes for Thorn tandem (thread)
By Peter Jacobsen on Mon 1 Oct 2012 05:58 Edit Delete in reply to #1     Reply (1)   Printable Relation | Link | Bookmark | Report
There shouldn't be a difference in breaking power between Deore and XT V-brakes. The geometry is identical, but XT might feel slightly more smooth to the hand (and they weigh slightly less).

If you're used to cantilever brakes, you will immediately feel the difference in increased breaking power when using V-brakes.

Disc brakes may have even more breaking power, but they put significantly more stress on the spokes, especially on a heavy bike like a tandem with two people and lots of luggage. Rim brakes don't really put stress on the spokes at all.

      
#5: Re: V Brakes for Thorn tandem (thread)
By John Meiners on Mon 1 Oct 2012 07:39 Edit Delete in reply to #4     Reply (1)   Printable Relation | Link | Bookmark | Report
Rim brakes don't really put stress on the spokes at all.

The friction of the brake takes place near the top of the rim, and that force needs to be transferred down to where the tire contacts the road. The rim transfers part of the force, but the spokes transfer most of it. This became clear to me when I broke a spoke while braking on a fast descent.

      
#6: Re: V Brakes for Thorn tandem (thread)
By Peter Jacobsen on Mon 1 Oct 2012 15:35 Edit Delete in reply to #5     Reply (1)   Printable Relation | Link | Bookmark | Report
The rim transfers part of the force, but the spokes transfer most of it.

Hmm, that doesn't seem very logical to me, but admittedly, I'm not an engineer. Can anyone clear this up?

      
#7: Re: V Brakes for Thorn tandem (thread)
By Mike Ayling on Mon 1 Oct 2012 15:53 Edit Delete in reply to #3     Reply (1)   Printable Relation | Link | Bookmark | Report
Thanks Dave for the advice about the CSS rim coatings. There goes another 180 quid!

Mike

      
#8: Re: V Brakes for Thorn tandem (thread)
By John Meiners on Mon 1 Oct 2012 20:15 Edit Delete in reply to #6     Reply (1)   Printable Relation | Link | Bookmark | Report
Well, I am an engineer, but that doesn't make me an expert at this. There are many, many force vectors involved here.

The brakes' job is to slow you down (i.e., cause deceleration). In order to do that, force must be applied to you in the direction opposite of your velocity (velocity includes both speed and direction). Since you only have three contact points with the bike (hands, butt, feet), the force must push on these three points. These three points are all attached to the frame of the bike, so we must first apply the force to the frame. The only thing we can push against to apply this force is the ground. The only contact points with the ground are the tires. The brakes job is to get the tires to push backwards against the ground. This force must then be transferred to the frame. The only connection point between the tires and the frame is through the rim to the spokes to the hubs to the dropouts. So the only physical way to decelerate the bike (ignoring air resistance and gravity) is to have the spokes push and pull against the hub.

      
#9: Re: V Brakes for Thorn tandem (thread)
By George White on Mon 1 Oct 2012 21:44 Edit Delete in reply to #8     Reply (1)   Printable Relation | Link | Bookmark | Report
Hi John,

The only connection point between the tires and the frame is through the rim to the spokes to the hubs to the dropouts. So the only physical way to decelerate the bike (ignoring air resistance and gravity) is to have the spokes push and pull against the hub.

This is the situation for disk brakes. The spokes have to withstand the whole torsional force.

For V brakes there is an additional contact point - the brakes to the frame. Now the forces change, the torsional force is taken by the rim and the main force on the spokes is horizontal, similar to the vertical load when sitting on bike. The two force vectors (brake and load weight) interact but the force is still primarily tension in the spokes with a small torsional component.

George

      
#10: Re: V Brakes for Thorn tandem (thread)
By John Nettles on Tue 2 Oct 2012 00:21 Edit Delete in reply to #1     Reply   Printable Relation | Link | Bookmark | Report
If you can, I would do both. I have an older Santana tandem with both cantilever brakes and a drum (not disc) brake. I also have a Thorn Mk II with standard Deore V brakes but have will switch out to XTR as I have an older set laying around.

For our tandem, I use the cantis for normal stopping. I use the drum as a drag brake for when going down long hills. As you know, you can build speed pretty quickly on a tandem so a drag is nice, especially since it is not on the rim. If you can't afford to do the disc brake now, at least be sure to get the Rohloff that is disc capable so you can add later. You can always buy a used Avid BB-7 on eBay and then you only need the rotor. Since you won't use the disc as often, it should last a pretty long time.

Happy trails!

      
#11: Re: V Brakes for Thorn tandem (thread)
By Dave & Jo Whitney on Tue 2 Oct 2012 03:46 Edit Delete in reply to #7     Reply (2)   Printable Relation | Link | Bookmark | Report
Oops, sorry about that. I should add you also have to get the special Swissstop Blue brake pads for ceramic and/or CSS rims. Another £25! They do last for ages.

Seriously though. For a long term investment in longevity with superior braking power Ceramic and
CSS rims on a tandem was the best decision I made. I am still running them without any sign of wear at all and have total confidence in them.

Dave

      
#12: Re: V Brakes for Thorn tandem (thread)
By Dale Oswald on Tue 2 Oct 2012 06:35 Edit Delete in reply to #11     Reply (1)   Printable Relation | Link | Bookmark | Report
The ceramic rim idea may be worth investigating, not for the tandem so much as for the single. My current main ride is the second bike I've had where the rims started to fail at about 13K miles, by the sidewalls spreading. That's due to the brakes eventually wearing the rim sidewalls thinner. Do ceramic rims last longer, or do they just provide better friction characteristics?

I'm not convinced that I need better friction. Both the OEM pads and salmons are more than adequate to lift off the rear wheel on the single and don't fade on a long, hard stop, wet stopping is good and modulation is very controllable. What more do I need?

      
#13: Re: V Brakes for Thorn tandem (thread)
By Dave & Jo Whitney on Tue 2 Oct 2012 07:36 Edit Delete in reply to #12     Reply   Printable Relation | Link | Bookmark | Report
The short answer is yes they do last longer. Apparently the ceramic coating insulates the rim by dissipating heat back into the brake blocks, reducing wear and tear. Have a look at this review of the rim type we have on the front of our tandem.

http://www.edinburghbicycle.com/products/mavic-ex721-rim

Dave

      
#14: Re: V Brakes for Thorn tandem (thread)
By John Meiners on Tue 2 Oct 2012 08:18 Edit Delete in reply to #9     Reply (1)   Printable Relation | Link | Bookmark | Report
Thanks George for correcting my omission. I guess the bottom line is that the rim transfers some of the force and the spokes transfer the rest. Without detailed testing and/or calculations, we have nothing to go on but gut feel as to how much is transferred by each. I have a several-hundred-page book called Bicycle Science, but even it doesn't answer this question. There is a woeful paucity of scientific research into bicycle science, despite considerable money in the sport (e.g., Tour de France). Even such simple questions as to how tire pressure affects rolling resistance have not been effectively answered by science (testing to date has been limited to stationary wheels against steel drums, which is a poor substitute for the real thing).

Nevertheless, we know that the spokes are capable of transferring significant forces to the ground, since that's the only path for pedal-driven acceleration.

I see a masters thesis or doctoral dissertation possibility here. The equipment necessary for the testing would be expensive, however, and would probably need to be specially built.

      
#15: Re: V Brakes for Thorn tandem (thread)
By Curtis Mahr on Tue 2 Oct 2012 09:17 Edit Delete in reply to #14     Reply (1)   Printable Relation | Link | Bookmark | Report
This might help to clear things up. Then again, probably not...

http://www.duke.edu/~hpgavin/papers/HPGavin-Wheel-Paper.pdf

Curtis

      
#16: Re: V Brakes for Thorn tandem (thread)
By George White on Tue 2 Oct 2012 11:08 Edit Delete in reply to #15     Reply   Printable Relation | Link | Bookmark | Report
Hi Curtis,

Probably not, sadly. Certainly I couldn't see anything. He looks at the fatigue effects of varying spoke tension cycles in normal, straight ahead rotation. He notes that cornering, braking &c add to these but does not go into details of their effect...

George

      
#17: Re: V Brakes for Thorn tandem (thread)
By Mike Ayling on Tue 2 Oct 2012 23:18 Edit Delete in reply to #11     Reply (1)   Printable Relation | Link | Bookmark | Report
Dave wrote:

"I should add you also have to get the special Swissstop Blue brake pads for ceramic and/or CSS rims. Another £25! They do last for ages"

If I am reading the price list correctly the blue pads are included in the GBP 87 cost for the CSS rims upgrade.

You have convinced me that it is the way to go.

Mike

      
#18: Re: V Brakes for Thorn tandem (thread)
By Emma Taylor on Wed 3 Oct 2012 07:06 Edit Delete in reply to #17     Reply   Printable Relation | Link | Bookmark | Report
"You have convinced me that it is the way to go"

it is the way to go, Mike. They are excellent and there is a line in both my husbands bike details and my bike details that agrees with the statement the cost is included in the CSS rim upgrades at least when we had our bikes built nearly 2 years ago it was!

Relation | Bookmark | Edit | | Report | Link
Click here for a larger version of the picture

      
#19: Re: V Brakes for Thorn tandem (thread)
By Mike Ayling on Thu 1 Nov 2012 23:08 Edit Delete in reply to #1     Reply (1)   Printable Relation | Link | Bookmark | Report
Well we have just sent off the final order confirmation specifying XT V brakes with the CSS coated rims. Based on Dave's experience we have not specified the disc brake fitting on the Rohloff hub.

A big thank you to Dave and Emma and everyone else who advised on the Thorn specs.

We hope to take delivery some time before Christmas!

Mike

      
#20: Re: V Brakes for Thorn tandem (thread)
By Graham Smith on Fri 2 Nov 2012 22:01 Edit Delete in reply to #19     Reply   Printable Relation | Link | Bookmark | Report
I'm late to the party Mike, but one final piece of assurance.

They are top brakes, especially with the ceramic coated rims.My set up is in the pic below.
I have disc brakes on my mountain bike and they are more responsive than the V brakes but not by much.

I've just finished a tour on my loaded up Thorn where there were a lot of brake testing hills. The V brakes were excellent under all conditions.

Relation | Bookmark | Edit | | Report | Link
Click here for a larger version of the picture

These XTR V brakes and the ceramic coated rims work well together. Not quite as good as disc brakes but still impressive and reassuringly effective with a full load in wet conditions. Blue Koolstop pads are very good. Worked a treat.

Before the tour I replaced the nobbly, heavy 2.0" Schwalbe XR tyres with lighter, slicker 1.6" Schwalbe Marathon Supreme tyres. More detail is on the next page.
This turned out to be a good move. The Supremes are much better suited to the Sherpa.

Image on journal page: Bike Pics and Specs: Thorn Sherpa Touring Bike in journal Lake to Lake Sitting on a Thorn by Graham Smith (Completed Oct 2012)


First Prev Next Last (page 1 of 1) Page 1


Website Copyright © 2000-2014 by Neil Gunton Fri 31 Oct 2014 06:30 (US/Pacific) (0.289s)      Top    Link    Report    Terms of Service