Wednesday, February 18, 2015

Can I Install Tern Handlepost/Fork on Dahon Frame? Part 1: Introduction

As discussed in the previous blog post, I have always worried about the strength of the special 31.8mm stem on my Dahon Boardwalk. In fact, the clamps have broken before, thankfully not during a ride. That was the reason why I decided to get the better Controltech Stem to replace it.

The Controltech Stem requires a T-shaped handlepost for mounting a handlebar, similar to the setup shown in the picture below.

Syntace Stem used on the Tern Verge X18, but the clamp size is for 25.4mm handlebars, not 31.8mm.

As I am already using the Fnhon 4 bolt handlepost, this means that it is not directly compatible with the Controltech Stem, which requires a T-shaped handlepost. I could use the bar section of the stem (as seen below), and clamp that section in the 4 bolt handlepost. This will create a T-shaped handlepost for the Controltech Stem to fix onto.

The bar section of the stem (on the left) that I can use to convert a clamp type handlepost to T-shaped handlepost.

However, I don't really like this setup as it means multiple joints, which causes lower stiffness and is not an elegant setup. There will still be many bolts at the handlebar area as the 4 bolt handlepost is still there.

The only way to install the Controltech Stem elegantly is to use a T-shaped handlepost. The Controltech Stem will then join the handlebar to the handlepost, clean and simple. The problem here is that neither Dahon or Fnhon makes T-shaped handleposts in such a short length. In order to maintain the handlebar height at about the same level, I will require a handlepost that is approximately 29cm in length (from top to base). The shortest T-shaped handlepost from Fnhon is about 34cm in length which is way too long.

During my search for a suitable handlepost, I found that Tern handleposts are actually shorter, and are quite easily available from www.premiumbikegear.com. There are a few choices available, with different lengths, tilt angle and colour.

The problem is, a Tern handlepost cannot be fitted directly onto my Dahon Boardwalk. This is because the Tern handlepost requires a longer section of the fork steerer tube for clamping, as compared to a Dahon handlepost. In other words, to have a chance of using a Tern handlepost on a Dahon bike, I will also require a new Tern fork with a longer steerer tube. Since this is the only option I have, I decided to get both a Tern handlepost and a Tern fork. The only way to find out if a Tern handlepost will work on a Dahon bike is to try it out myself!

First, I need to choose the handlepost. For most bikes, the tilt angle should be 12 degrees. This will put the handlepost pointing straight up when mounted on the bike. Checking the Tern Bicycles website will show the different bike models that uses 6 or 12 degree tilt angles. As for the length, I went for the shorter 290mm (29cm) version as that is exactly what I need.

Tern handlepost is available in Black or Silver colour, with 2 different tilt angles and 2 different lengths.

Tern Physis 3D handlepost, in the specifications I need.

Looks very sturdy!

Measures 29cm from the base to the centre of the T-shaped portion. I found that a good way to measure the handlepost length is to set the base flat on the floor, and measure the height from the floor.

T-shaped top portion is machined separately, and press-fitted onto the top of the handlepost

Metal pin used for hooking onto the rubber strap on Tern bikes when the handlepost is folded down. I will remove this pin since it is not required.

Very tall clamping section with 2 clamp bolts. You can see the rubber seal at the base of the handlepost.

3D forged profile is strong and seamless, with no welding lines to be seen anywhere on the handlepost.

Base of the handlepost, with the rubber seal removed. This base profile is special as it replaces the Upper Cover of the headset. More details in the next blog post.

Inside of the handlepost base. Note the tall clamping portion.

External locking mechanism, used on earlier versions of Dahon bikes before the clamp mechanism was changed to internal. Although the external clamp looks bulky, it still works very well.

Note the distance between the base hinge and the lever hinge. This gives a really wide joint interface which is good for ensuring high stiffness.

Safety catch on the locking lever which prevents the lever from opening on its own. It does not take any load when the handlepost is adjusted and operated correctly. Therefore, the handlepost can function normally even if the safety catch is broken.

Weight of the Tern Physis 3D handlepost. Weighs 710 grams, a whole 200 grams heavier than the Fnhon 4 bolt handlepost which weighs 511 grams. Hopefully the additional weight is worth the improvement in stiffness!

Now that I have introduced the new Tern handlepost, it is time to look at the new Tern fork. For 20" Tern forks, there is only Black or White colours to choose from. All other specifications are the same. As stated above, the reason for getting a new fork is because I need a fork with a longer steerer tube to be compatible with the Tern handlepost.

Brand new Tern 20" fork!

Unwrapped and ready to go

Main difference from Dahon fork is that the V brake bosses are at the rear of the fork instead of at the front...

...and the mount for the Magnetix plate is on the right side of the fork leg instead of the left. This is due to the different folding method.

The steerer tube area and the inside of the fork is similar to Dahon forks. Can still use the Elosix front brake adaptor for caliper brakes.

Weighs 438 grams on its own, comparable to the Dahon fork.

The key part of this Tern fork is the steerer tube, which is 140mm long. For reference, the Dahon fork has steerer tubes of 2 different lengths, 111mm (for Speed/Boardwalk/Vitesse frames) and 123mm (for Mu frames).

Another new discovery for me is that the inside of the fork is not threaded. Rather, it has a starnut inserted in the steerer tube, same as standard road bikes or mountain bikes.

Although there is no problem in dealing with a starnut, the problem is that neither the fork nor the handlepost comes with a top cap to be used with the starnut. As shown in the handlepost installation manual below, a top cap is required to pre-load the headset bearings during installation.

Installation manual for the Tern handlepost

Luckily, the missing top cap is just a standard top cap, which is the same as those found on road bikes or mountain bikes. It is easy to find a top cap to use with this Tern handlepost and fork.

Standard top cap used for pre-loading the headset bearings.

A standard M6 bolt of suitable length is used with the top cap.

The M6 bolt will thread into the starnut during installation of the handlepost.

Total weight of the Tern fork + top cap is 454 grams, lighter than the Dahon fork + steel compression bolt at 488 grams.

With a new Tern handlepost and fork in hand, I will be able to do a proper comparison between the handleposts and forks of Dahon and Tern. By doing so, I can see how to make the Tern handlepost and fork fit my Dahon Boardwalk frame. Is it possible, and is it easy? To be continued in Part 2!

Click here for Part 2!

36 comments:

  1. Hi Steve, Did you look at the litepro handlepost? I think there is a 29cm T joint available. However not sure how is stiffness of litepro handle post. This litepro handle post fold out.

    Regards
    Kel

    ReplyDelete
    Replies
    1. The Litepro handlepost is probably the same quality as the Fnhon type. I think you are right as I didn't come across the Litepro 29cm handlepost during my search. Never mind, I already got the Tern handlepost and fork, so will try to make those fit. Thanks for the info anyway.

      Delete
  2. Hi bro, thinking of changing my tern link c7's 2-piece handlepost and steel fork to single piece handlepost and alu/carbon fork. Possible?

    ReplyDelete
    Replies
    1. I think it should be possible, but I'm not sure what the construction and dimensions are. Some pictures would be useful.

      Delete
  3. Any issues with folding the Boardwalk with the Tern fork? With the magnetix mount being on the other side.

    Planning on using a Tern fork on my Dahon Speed D7 to mount a Tern Spartan rack up front.

    ReplyDelete
    Replies
    1. I have actually removed the Magnetix parts from the bike, as I can't fold it in such a way that I can use the magnet.

      If I fold it the traditional Dahon way, the magnet is on the outside and does not touch the metal plate.

      If I fold it the Tern way (N-fold), the magnet can touch the metal plate, but the whole bike will be unbalanced due to the different heights of the front and rear wheel.

      In the end, I will just fold it the traditional Dahon way, but without the magnet.

      If you use the Tern fork, you will have to cut off quite a lot of the steerer tube in order to reinstall the Dahon handlepost. I think it is not worth the trouble.

      Delete
  4. I see, thank you for the wonderful insight. I can understand some of the issues you pointed out, such as the bike being unbalanced when N-folded, which is mainly because of the straight main tube of the bikes.

    I was planning on mounting panniers up front for better weight distribution when touring. The discontinued Biologic Front Traveler Rack is hard to come by from where I am from, but there's tons of Tern Spartan Racks available here hence I am contemplating on changing to a Tern fork.

    One last question: Assuming a cut-down Tern fork is used, will there be any interference issues between the top cap and the Dahon Radius handlepost when locked into place? I'm assuming there is very little space in there and would probably need a top cap that is as flat as possible, if not inverted.

    Here's a shot of my ongoing "pocket tourer" project :) I'm still missing a front pannier rack and waiting for 32H 74mm front hubs to restock.

    https://igcdn-photos-e-a.akamaihd.net/hphotos-ak-xaf1/t51.2885-15/11008320_889785801089132_962039091_n.jpg

    ReplyDelete
  5. Assuming you cut down the steerer tube of the Tern fork correctly, it will fit the Dahon handlepost. You can use a top cap to secure the Dahon handlepost to the Tern fork, no problem. There is plenty of space in there for a top cap.

    If you want to install a Tern fork with your Dahon Speed D7 and a Dahon handlepost, you will need a steerer tube that is about 111mm long (same as original Speed D7 fork). This means cutting down the Tern fork from 140mm to 111mm.

    This is a huge amount to cut, and I strongly suggest that you check and recheck the measurements carefully. Also, I would suggest removing the original starnut in the Tern handlepost (by drilling out or otherwise), as it is too far in to push down.

    After cutting the steerer tube to the correct length, reinstall a fresh starnut (you can't reuse the original starnut).

    ReplyDelete
  6. Alright, thank you very much for the wonderful advice! :) I will consider these things as I weigh my options for front panniers.

    ReplyDelete
  7. Hi, Im Planning to change my existing Tern Link D8 handlepost to a shorter 290mm and install controltech+dropbar. Would a 6 degree angle be okay for the reach or will it feel too cramped? Do you think it will affect steering? For reference I'm 5'10 ft tall. The reason why I would like a 6 degree angled handlepost is just the symmetry to the seatpost and fork angle (when viewed sideways), just as a Verge x30h handlepost which is not tilted upright.

    ReplyDelete
    Replies
    1. I think 12 degrees tilt will be a better choice for a flat handlebar. The Verge X30h has a 6 degree handlepost because it uses a bullhorn bar. This bullhorn bar actually moves the gripping area forward compared to a flat handlebar, which is why the X30h is OK with a 6 degree tilt. For a flat handlebar a 12 degree tilt will feel better.

      Delete
  8. Hi Steve! I bought a boardwalk D8 for the wife last year and I really don't like the play that the telescopic handlebar post has unless clamped ridiculously tight. Recently I came across the Boardwalk S1 on the net and saw that the unadjustable post looks pretty long so was wondering if it can fit onto ours? Wife likes the upright riding posture so love to hear your thoughts!

    ReplyDelete
    Replies
    1. First, there is no need to keep posting a comment. It did not appear on this page because all comments will need my approval first.

      As for the handlepost which you want to fit, which handlepost are you referring to? The one on the Boardwalk S1 or the Tern Physis handlepost?

      The Boardwalk S1 handlepost is a very old design and is not compatible to your Boardwalk D8. The Tern Physis handlepost will require a new Tern fork.

      You can get a Dahon Mu Uno handlepost or Fnhon handlepost from Taobao.com. Those are compatible to the Boardwalk D8. You can start from litepro.taobao.com.

      Delete
  9. Hi Steve - Great stuff you have here. We definitely do not recommend using Tern fork with Dahon handlepost. The Dahon handlepost design depends a lot on the internally threaded steerer with bolt to keep the Radius attached to fork. Tern forks do not have the internal threading, depending instead on longer steerer and increased interface with the Physis. A starnut is fine for compression of headset bearings but is not designed to keep Radius attached to fork.

    ReplyDelete
    Replies
    1. Hi Joshua, thanks for the technical insight. In this case, pairing a Tern fork with Tern handlepost should be fine right?

      Delete
  10. hi steve,

    I am assuming you had experience riding with fnhon handlepost and tern handlepost. Is the experience huge in terms of stiffness for those riding on comfort position.

    tnx

    ReplyDelete
    Replies
    1. Comparing the Tern handlepost to the Fnhon one-piece handlepost, there is not much difference in stiffness.

      Delete
    2. Steve, what are my options for upgrading the handlepost of my tern link c7?

      Can i use handleposts from tern verge or d8?
      Can i use the clamp type from litepro?

      Delete
    3. For Tern Link C7, the headset and fork design is different from Verge. You can use LitePro/Fnhon handleposts, but not Tern handlepost.

      Delete
    4. Hi steve thanks for taking time. Can i use tern d8 onwards fork so that i can fit the physis handlepost?

      Delete
    5. I am not sure about the headtube height on the Link C7 frame. If the headtube height is about 101mm, the Tern handlepost and fork will go on without any additional work.
      http://handsonbike.blogspot.sg/2015/03/can-i-install-tern-handlepostfork-on_20.html

      Delete
  11. Hi Steve, great info/blog. I have just purchased a tern verge P18 but would like to shorten the handlebar/post height a few cm, preferably without increasing the weight. What would you recommend? thanks!

    ReplyDelete
    Replies
    1. You can use a stem to lower the handlebar height, or change to a shorter handlepost, which can be found on premiumbikegear.com

      Delete
  12. Thanks Steve. I purchased a two part stem locally, now looking for a tube cutter to make the centerpiece... but it wont lower the bar much. Thus I am quite tempted by the handleposts on premiumgear and elsewhere. I have written twice to premiumgear asking about the difference (weight, etc) between the 2D and 3D 29cm models (no reply thus far). I prefer to upgrade (i.e. 3D but not at the cost of added weight) I await their reply... but if you think others (jetstream, litepro, or maybe that dreambike/wheelsport one could work... I would be tempted. Any thoughts? Thanks again!

    ReplyDelete
    Replies
    1. The Physis handleposts on premiumbikegear are suitable for Tern Verge P18. 2D or 3D is just difference in manufacturing process. The other Dahon/Fnhon handleposts are not suitable.

      Delete
    2. The Physis handleposts on premiumbikegear are suitable for Tern Verge P18. 2D or 3D is just difference in manufacturing process. The other Dahon/Fnhon handleposts are not suitable.

      Delete
  13. ok great, many thanks Steve.

    ReplyDelete
  14. Hi Steve

    I'm upgrading my link uno and I'm confused which type of bar I should get. What's the difference in bar length and angle, can't seem to find these info on the website.

    I'm about 178cm (5'11") and I'm planning to get a bullhorn bar with the syntace VRO stem

    Thx!

    ReplyDelete
    Replies
    1. The website has different choices of angle and length for the handlepost. A lower handlepost will allow for a more aggressive riding position.

      Delete
  15. Hi Steve,
    I have a Tern verge x18 and would like to replace the 42cm handlebars with either 38cm or 40cm. Would any 25.4 handlebar fit the Syntace VRO 47 stem please?
    Many thanks
    Elaine

    ReplyDelete
    Replies
    1. Yes it will fit. Or you can cut short your current handlebar.

      Delete
  16. Hi Steve,

    I am thinking of "upgrading" my handlepost. How does the height of the handlepost affect the handling of the bike?

    I will like to solve the following issues at the same time and appreciate your comments whether a change of handlepost will help alleviate them:

    1. My bike is very sensitive maneuvering turns. I do not want to change my current handlebar which feels comfortable for me (low rise low sweep Monkeylite XC cut to 535mm)


    2. I am not able to fold my Dahon Boardwalk D8 2014 (HAC082) very neatly. I am thinking of a handlepost that folds outwards instead of the DAHON Forged Aluminum Radius-V Handlepost which folds inwards

    3. Prefer something black for aesthetic reasons


    What handlepost (or no change at all) will you recommend?
    Really appreciate any advice you can provide!

    Many thanks in advance.


    Victor

    ReplyDelete
    Replies
    1. Your handlebar is considered narrow, which makes steering more sensitive.

      Changing to an outward folding Fnhon handlepost will solve the problem of tucking in the handlebar neatly between the wheels during folding.

      Can get a black one piece Fnhon handlepost that is shorter for stiffness. Add a Litepro to put the handlebar ahead of the handlepost for better steering stability.

      Delete
    2. Thanks for the advice!

      I tried looking up the Litepro stem that you mentioned on Taobao, I could find it but it looks like I can't purchase it. This is the error I got:

      根据所在国法律法规或平台政策,此项商品限制下单购买。

      Do you know of any other alternatives?

      Delete
    3. Try to see if you can get it from other sellers on Taobao.

      Delete