Changed the fork, what next?

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cwah

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Hello all,

I have changed the fork of my dahon jetstream to allow front disc brake and better suspension:
2014-12-21%2013.40.35.jpg


It doesn't look as nice as I hoped... so I have few questions:
- Would the frame hold the weight with the new geometry? It does look like a lot of weight will be managed by the middle of the frame and I fear it may break someday in the middle?
- Is it better to have 20" or 26" front wheel? The fork is for 20" wheel
- The bottom of the fork doesn't completely fit inside the frame (it ends wider), is that normal? And what can I do?


Thanks guys
 
The fork looks like it's for a 26" wheel, not 20" as stated, although that shouldn't be a problem. Otherwise, since the frame won't "accept" the fork, this looks like a disaster waiting to happen. For your benefit, hope that Chalo or Dogman Dan see this and comment.
 
You can't install this 1 1/2" - 1 1/8" tapered steer tube into your 1 1/8" staight head tube. This should be obvious to anyone that it doesn't fit. You need a fork with a 1 1/8" steer tube, that's it.

The way it is now, it will fail sooner or later and believe me, it is not the kind of failure that you want to experiment.
 
MadRhino said:
...
The way it is now, it will fail sooner or later and believe me, it is not the kind of failure that you want to experiment.
Click to expand...
I experimented with that type of failure just once...
The experience led me to believe i should never repeat that. ever. again.
 
Nice fork, but it is every kind of wrong on that bike. Whoever told you it was for a 20" wheel - they lied -because Rockshox has never made a suspension fork for 20" wheels :|

You may want to consider snapping up one of these->

http://www.ebay.com/itm/Mekkem-Recumbent-Electric-Bike-Suspension-Fork-20-Tall-Carbon-20-Inch-Fork-/231392060875?pt=US_Forks&hash=item35e00aa5cb
 
Although it's not right, I can't see anything that would make it fail. I think it would be helpful if you guys above can explain how you think it would fail or exactly how you had problems with similar.
 
Did you notice that there is ~2" of 1-1/2" diameter tapered steerer tube exposed below the head tube?

That, plus 3" (because the fork is for a 26" wheel) means the front end is about 5" higher than stock(?!)

Seems totally goofy to me. How was the test ride, cwah?
 
Mostly it fails because it has several inches of steer tube showing, with the lower bearing several inches from the headset.

It now looks a lot like the bike I built that failed. I took a 24" bmx frame, and put a 26" wheel and fork on it. The result was a very slack head angle, and a tendency to wheelie. Once in a while the front wheel would touch long enough to actually steer.

You might get away with a different fort, one that fits your headset, and 20" wheel. But look for a very short travel one, like 100mm. 26" wheel will just jack it more to the rear, like mine did.

Obviously finding a nice 20" suspension fork is just about impossible.
 
Yeah, folding 26" bike would be able to fit a variety of regular forks. Doubtful that that fork will fit a new bike though. It's a fancy fork made for a high end DH bike.

My bike failed because the front wheel only occasionally touched the ground. I did have a big motor on it, but even with all the battery mounted forward it was a real wheeliemobile. Seriously, you had to jam the wheel back down, steer a little, jam it back down, steer some more. Otherwise you just rode around with the front wheel about 2" off the ground all day.

It was kind of fun to ride in loose dirt, kind of like a unicycle that hauled ass but with handlebars to hang onto. But as a usable bike, it sucked balls.
 
The major problem AFAICT is that the bottom race of the headset isn't flush with the top of the fork. This would seem (TO ME) to place a lot of stress on the fork tube in an area which wasn't designed for shear force. Tapered headsets are moving into mainstream MTB's and you might be able to locate a frame that isn't for downhill use.
 
I don't think I can return it because I started to trim the top tube :(

I was thinking to sell it back in ebay... or somewhere else :(

Would this one work for SURE?
http://www.winstanleysbikes.co.uk/product/64926/RockShox_XC30_TK_Coil_2015_Forks_RS8627000

Or maybe I sell my dahon jetstream and buy a proper 26" folding bike? Such as a montague?
 
That should fit, but most of the geometry problem would still be there. As mentioned above, a recumbent fork (look at ebay) might work but the trail (look it up in Wikipedia) might be different enough to cause other handling quirks.
 
2old said:
That should fit, but most of the geometry problem would still be there. As mentioned above, a recumbent fork (look at ebay) might work but the trail (look it up in Wikipedia) might be different enough to cause other handling quirks.
Click to expand...

Recumbent fork are pretty much a no go for me as they are so expensive and don't even have suspension....

What else can I do? Is selling the bike my only option? :(
 
Um, here's one that Stevil posted above that costs $69 shipped. Did you not see it or is there a problem with it I'm not understanding. You're in England, so it may cost a little more to ship I presume.

Stevil_Knevil said:
Nice fork, but it is every kind of wrong on that bike. Whoever told you it was for a 20" wheel - they lied -because Rockshox has never made a suspension fork for 20" wheels :|

You may want to consider snapping up one of these->

http://www.ebay.com/itm/Mekkem-Recumbent-Electric-Bike-Suspension-Fork-20-Tall-Carbon-20-Inch-Fork-/231392060875?pt=US_Forks&hash=item35e00aa5cb
Click to expand...
 
number1cruncher said:
Um, here's one that Stevil posted above that costs $69 shipped. Did you not see it or is there a problem with it I'm not understanding. You're in England, so it may cost a little more to ship I presume.

Stevil_Knevil said:
Nice fork, but it is every kind of wrong on that bike. Whoever told you it was for a 20" wheel - they lied -because Rockshox has never made a suspension fork for 20" wheels :|

You may want to consider snapping up one of these->

http://www.ebay.com/itm/Mekkem-Recumbent-Electric-Bike-Suspension-Fork-20-Tall-Carbon-20-Inch-Fork-/231392060875?pt=US_Forks&hash=item35e00aa5cb
Click to expand...
Click to expand...


I saw that but I'm not sure I want to go down that route for many reasons:
- Shipping + customs is going to double the price of the fork.
- Travel is still not enough. I'd like to get 100mm travel at least. I run over 30mph on the bike and there are LOAD of potholes on the road. A small 20" wheel + small travel = very bad journey and maybe accidents.
- It would have a negative effect on the bike foldability. It's acceptable if I can have a very good suspension that allow me to pass through the potholes, but if I don't have that and foldability is also affected... I'm wondering if it's not better to sell the bike and get a montague??

Any thoughts?
 
The way I see it, assuming he's used a standard 1 1/8 headset is that the lower bearing inner will be wedged at the top of the taper just like it normally wedges on the taper at the bottom of a straight 1 1/8 steerer tube. There's an Ahead cap and spacers above the top headset to clamp/adjust it properly. The only possible problem I can see is that the botom headset inner has nothing to hold it square, but I think it would self-centralise to bring itself square.
 
Yep, but the steerer tube is pressed in from below the stanchion/crown, and there is nothing preventing the stanchion from being knocked up and off the steerer tube = poor cwah face planting :shock:

Properly assembled, the lower bearing race sits flush on the stanchion. Once the bearing assembly and fork is inserted into the headtube, the headset tension is set and the stem is tightened. The stanchion is effectively drawn up and sandwiched between the bottom of the steerer tube and lower bearing = happy cwah hunting for potholes!
 
cwah said:
.... I'm wondering if it's not better to sell the bike and get a montague??

Any thoughts?
Click to expand...

I have a blue Montague in my stable, and I started appreciating it a lot more after reading David (Talking Heads) Byrne's book, "Bicycle Diaries".

DavidByrne.jpg
 
Is the frame steel? If so, perhaps you could have someone weld an additional headtube in front of the existing one, with bracing along the sides back to the "toptube". I did this on CrazyBike2 in order to use threadless 1-1/8" forks on it, when the front frame I used to build it only had 1" headtube to start with. I cut the new headtube off a different bike frame being used for other parts.

It's ugly, but it hasn't broken, deformed, or budged in the 2 or 3 years since I did that. :)

Or have them just replace the original headtube with a new one of the rigth type. I did not do that because there was the chance I would need to use 1" forks again at some point, for whatever reason.
 
cwah said:
Travel is still not enough. I'd like to get 100mm travel at least. I run over 30mph on the bike and there are LOAD of potholes on the road. A small 20" wheel + small travel = very bad journey and maybe accidents.
Click to expand...

I'm no expert, but I think you're expecting too much of a 20" folding bike if you want to crash through potholes comfortably at 30mph. Avoid the potholes and a any cheapo "50mm" (actually more like 25mm) fork will do. Potholes put huge loads on a vehicle - I always do my best to avoid them even in cars.
 
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