Bar and steer tube fitment, accessories - Dahon
10-09-19, 11:33 AM
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Bikes: Surly Disk Trucker, 2014 w/Brooks Flyer Special saddle, Tubus racks - Duo front/Logo Evo rear, 2019 Dahon Mariner D8, Both bikes share Ortlieb Packer Plus series panniers, Garmin Edge 1000
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Bar and steer tube fitment, accessories - Dahon
I got to looking at my bike trying to figure out some changes. For reference the bike is a Dahon Mariner D8.
What I want to do is set the bike up with different handlebars, but also keep the ability to mount accessories. To that point I am looking at the stem and how the handlebars mount. There is no "stem", per se, on the Dahon - the bar clamp is on the top of the steer tube (which telescopes).
What I did on my touring bike is added a second stem underneath the handlebar stem to hold a dummy bar and accessories. I like that set up as it frees up the handlebar. Interestingly to note - because the folder has such small wheels the vertical clearance I have up front is enormous. So that space is very much welcomed. With the telescoping steer tube I have quite a bit of space, I think, to drop a stem and dummy bar - if I can get the stem to mount to the upper steer tube. I will come back to this thought in a minute, but let me hit the handlebars next.
Because the bar clamp is fixed to the steer tube I am not sure I have a whole lot of options. I have seen folding bikes with conventional stems (that offset the bar mounting from the steer tube). The only difference I can see right off the start is that the steer tubes do not work under compression like a traditional bike fork/steer tube does. So the stem clamp that attaches to the steer tube is all there is holding things "together". I do not see any problem/challenge with that. Am I correct in that? Or have you found a situation where you have run in to problems?
Because the upper steer tube has a keyway in it to keep it straight when telescoping I can't replace it with another tube to use with the stem idea I am envisioning. That may mean I only have two options:
1. Either use the upper steer tube I have, or get a replacement, then cut off the bar clamp
2. If such an upper steer tube exists - buy one that is just the tube, no bar clamp
The keyway does give me a bit of pause as to whether or not it can take the clamping pressure of a stem?
Back to accessories -
The front of the frame has a block with 3x braze-on threaded inserts. I gather this is to mount a front basket, etc. Has anyone tried to use this mounting block before? My fear with trying to use that for a load on the front is that the threads will strip out (as in mounting bolts pulling through the metal) with much weight/vibration. By clamping around the steer tube I think there would be more strength and less worry of a gear failure.
On the same topic of the steer tube and the enormous space in the front - the other idea I have right now is to use a U-bolt clamp of some kind around the lower steer tube. This part is tapered and a larger diameter than the upper steer tube, so a clamp-on stem is out of the question. U-bolts would be more universal. As to how to distribute the pressure so as to not collapse, or bend, the lower steer tube - I am not sure yet on that one. There would have to be a balance between pressure and grip. I suppose on the upshot the taper of the lower steer tube is that it gets wider as it goes down, narrower at the top, so vibration and movement from gravity shouldn't cause the mount to drop on a ride, but what keeps it from rotating around the lower steer tube?
Has anyone put a front rack on a Dahon? The accessory mounts on the front dropouts (the only ones there) are taken up by the front fender. I don't think it would be too hard to make a plate that uses the axle (maybe both the axle and the fender mount to keep the plate from rotating - then replace the fender mount bolt with a longer one to go through the fender strut and the plate) to support rack struts. Then make some kind of attachment that uses the base of the steer tube for an upper mount. Or, just find a way to bolt the rack struts straight to the axle (bigger hole than a 5mm braze-on/accessory bolt)
What I want to do is set the bike up with different handlebars, but also keep the ability to mount accessories. To that point I am looking at the stem and how the handlebars mount. There is no "stem", per se, on the Dahon - the bar clamp is on the top of the steer tube (which telescopes).
What I did on my touring bike is added a second stem underneath the handlebar stem to hold a dummy bar and accessories. I like that set up as it frees up the handlebar. Interestingly to note - because the folder has such small wheels the vertical clearance I have up front is enormous. So that space is very much welcomed. With the telescoping steer tube I have quite a bit of space, I think, to drop a stem and dummy bar - if I can get the stem to mount to the upper steer tube. I will come back to this thought in a minute, but let me hit the handlebars next.
Because the bar clamp is fixed to the steer tube I am not sure I have a whole lot of options. I have seen folding bikes with conventional stems (that offset the bar mounting from the steer tube). The only difference I can see right off the start is that the steer tubes do not work under compression like a traditional bike fork/steer tube does. So the stem clamp that attaches to the steer tube is all there is holding things "together". I do not see any problem/challenge with that. Am I correct in that? Or have you found a situation where you have run in to problems?
Because the upper steer tube has a keyway in it to keep it straight when telescoping I can't replace it with another tube to use with the stem idea I am envisioning. That may mean I only have two options:
1. Either use the upper steer tube I have, or get a replacement, then cut off the bar clamp
2. If such an upper steer tube exists - buy one that is just the tube, no bar clamp
The keyway does give me a bit of pause as to whether or not it can take the clamping pressure of a stem?
Back to accessories -
The front of the frame has a block with 3x braze-on threaded inserts. I gather this is to mount a front basket, etc. Has anyone tried to use this mounting block before? My fear with trying to use that for a load on the front is that the threads will strip out (as in mounting bolts pulling through the metal) with much weight/vibration. By clamping around the steer tube I think there would be more strength and less worry of a gear failure.
On the same topic of the steer tube and the enormous space in the front - the other idea I have right now is to use a U-bolt clamp of some kind around the lower steer tube. This part is tapered and a larger diameter than the upper steer tube, so a clamp-on stem is out of the question. U-bolts would be more universal. As to how to distribute the pressure so as to not collapse, or bend, the lower steer tube - I am not sure yet on that one. There would have to be a balance between pressure and grip. I suppose on the upshot the taper of the lower steer tube is that it gets wider as it goes down, narrower at the top, so vibration and movement from gravity shouldn't cause the mount to drop on a ride, but what keeps it from rotating around the lower steer tube?
Has anyone put a front rack on a Dahon? The accessory mounts on the front dropouts (the only ones there) are taken up by the front fender. I don't think it would be too hard to make a plate that uses the axle (maybe both the axle and the fender mount to keep the plate from rotating - then replace the fender mount bolt with a longer one to go through the fender strut and the plate) to support rack struts. Then make some kind of attachment that uses the base of the steer tube for an upper mount. Or, just find a way to bolt the rack struts straight to the axle (bigger hole than a 5mm braze-on/accessory bolt)
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