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How to service bearings in Dahon Kinetix 74mm front hub?

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How to service bearings in Dahon Kinetix 74mm front hub?

Old 06-05-19, 08:11 AM
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tomtomtom123
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How to service bearings in Dahon Kinetix 74mm front hub?

How do I remove the bearings from the Dahon Kinetix 74mm front hub?

I used to have an older version where the bearings were flush with the outside of the hub, and the 2 end caps were threaded into an inner spindle. I could simply unthread 1 end cap with 4mm hex key on each side, the other cap would have a bit more friction and stay inside the inner spindle, then pull out the inner spindle, end cap and one cartridge bearing with pliers in one go, and then pull or tap out the opposite cartridge bearing. To put new ones in, I simply pressed in the new cartridge bearings until they were flush against the hub.

But now I have a newer version of the Kinetix hub. The end caps are not threaded in, but pressed and pulled out easily. With the end caps out, both bearings are still inside with the inner spindle. I don't see any internal recesses that I can tap against to get the bearings out.

Edit: I noticed the bearings are a different size. The old hub had 8x18x5mm 688 bearings. The new one seems to be 1/4" (6.35mm) bore and a little bit less than 16mm outside diameter. I haven't gotten it out, so I don't know the exact dimensions, but the closest I could find in specs is R4, which is 1/4"(6.35mm) x 5/8"(15.875mm) x 0.196"(4.978mm). Upon closer look, the inner spindle has the same bore diameter as the bore of the bearing, but at the very center of the spindle, there is a small narrower step, maybe 5.5mm in dameter. If I had a 6mm rod (I won't be able to find 1/4" here), I could probably knock it out. Or if I had a M3 x 60mm bolt maybe I could pull the bearing out to one side, but I doubt I could find such a long bolt at the local store.


Last edited by tomtomtom123; 06-05-19 at 09:43 AM.
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Old 06-05-19, 10:50 AM
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I saw this extractor, but doesn't seem to have 1/4" (6.35mm).
https://www.bearingprotools.com/products/bearing-puller




I might go to the hardware store and look for a 6mm anchor bolt and see if that works.

I don't want to knock the 5.5mm step in the middle of the internal spindle, because I'm worried that I might bend it. (I did try it with a hammer and a 6mm bolt, but nothing moved.
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Old 06-08-19, 06:16 PM
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Well, after a lot of frustrating failures, I finally got the bearings out. This is what I did:



I 3D printed 2 parts. The yellow colored cup and the red colored bushing sleeve. At first I did not have the bushing sleeve and I worried that I was damaging the hub spindle, so I stopped and waited for my printer to spit out the bushing sleeve before continuing the extraction.

I had to wait 3 days for a M3 x 60mm bolt to arrive in the post. It could have been 10mm shorter at 50mm if the 3D printed cup was also 10mm shorter, but I overestimated the length that I needed.

So what is happening is that the head of the M3 bolt is pressed against the little inner step at the center of the inside of the hub spindle. I turn the M3 nut at the end of the 3D printed cup, which then presses against the hub flange / spoke heads, and tries to squeeze out the cartridge bearing from inside. I only turned the nut. I kept the bolt stationary because I didn't want to strip the hex head or damage the spindle. I also had to hold the hex key (extra long version) and the wheel together to stop them from spinning.

The red colored 3D printed bushing sleeve is to keep the spindle centered on the bearing. When I wasn't using it, I was afraid that the spindle was contacting the bearing at angle and damaging the ends or bending it.

The M3 bolt is really weak and I was afraid I would snap it, but it seemed to withstand the forces applied to it. The M3 nut is so tiny, and it was really a struggle to turn it. I eventually found a socket wrench somewhere in my room and that helped make it turn faster.

During the first 10-20 turns, the bearing did not move. Instead, the plastic cup was compressing, or the M3 bolt was stretching. When the stress reached a certain level, it released all of a sudden with the bearing moving outward by 1-1.5mm. It made a very loud snapping sound and the slack caused the hex key to slip out of the M3 bolt. I thought I broke the spindle because it was loose and not touching the bearing, but that was because the bearing moved away. I had to tighten the nut to take away the slack. After the initial pop, the bearing slowly moved out with each turn of the nut.

I finally got both bearings out. But if you try this, you do it at your own risk. I take no responsibility.


Failures
1) I tried inserting a M6 bolt and then later a 1/4" bolt against the inner center step of the spindle, and hammered the bolt to try to push out the bearing, but it did not move at all. I was worried that I was damaging the spindle.

2) I tried 3D printing a plastic extractor that looked like one of those professional extractors. But the thickness was so tiny that it snapped when I touched it with my finger. (Wheels Mfg makes $20-30 bearing extractors, but they only start at 8mm. Bearingprotools starts at 11 GBP, but they said they don't have one as small as 1/4".)

3) I waited 3 days for some inch fasteners to arrive in the post. I got a 1/4" steel dowel pin, which is 20-30 metric microns thicker than the 6.35mm bore of the cartridge bearing. I tried hammering in the pin into the bearing and wiggle it out, but the bearing did not move at all. I was worried that I hammered too far inward past the bearing and into the spindle and stretched the opening of the spindle. I don't know if widening the spindle has any detrimental effect on the stability of the hub.



Oh, I noticed an error in my drawing. The older Dahon Kinetix hub probably can't fit a M4 bolt through the spindle. It probably needs M3, but can be shorter, maybe 30mm long.

So in the end, I spent about $45 on various rare sized fasteners to test. But I actually only needed to spend $8 (including postage) on the M3 bolt for extracting the bearings, and $3 on an M5 bolt and M8 narrow washers for pressing in the new bearings. A newly assembled complete wheel seems to be going for around $70.

Last edited by tomtomtom123; 06-08-19 at 06:47 PM.
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Old 06-09-19, 11:25 AM
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Today I pressed the bearings into the hub, using a M5 bolt, nuts and washers, and 8mm din 433 narrow washers that can fit inside the 15.875mm hole. The R4 bearings with 6.35mm bore is a huge pain to work with because metric fasteners have to be undersized, which are weaker and leaves gaps and creates the risk of tilt. One of the bearings didn't go in flat, and was tilted at a 5 degree angle but there was nothing I could do since I already got in halfway, except to complete the process. It was making really bad scratching sounds as the tilted bearing moved inward.

Towards the end, I forgot that I had planned to wrap the bolt on each end with a thin strip of masking tape to increase the section of the bolt from the bearing and a little bit into the spindle, increased to 6.35mm to serve as a kind of sleeve to fill in the gap, which would have reduced the risk of a tilted bearing. But it was already too late by the time I remembered. I did eventually add the tape sleeve for the last few turns of the bolt, and the bearing eventually flattened out and seated against the inner lip of the hub. But I don't know if I had caused any damage to the bearing that was tilted or the bore hole on that side of the hub. Spinning the wheel produces a feeling of a little bit of roughness in the bearings, but it still spins for several revolutions without stopping, so maybe it's ok. But the bit of roughness could be a symptom of some pitting in the trace from the tilted installation, which might quickly become worse. Well, there is nothing else I can do about it now. Those were the last 2 units of the Enduro R4 bearings that I could find commercially available at online stores in the entire country.

I noticed after pressing the new bearings (and before removing the old one) that one side of the hub has the bearing 0.4mm more inwards than the bearing on the other side. I'm not sure why it's like this, but the inner race tracks on both sides are already contacting the inner spindle, so they can't be pressed any further.

For my next front hub, I would avoid the Dahon Kinetix hubs that use the R4 bearing, and find one that uses the older design with the 688 bearing with larger inner diameter of 8mm. There are cheap pullers and presses available for 8mm bore holes. Handsonbike blog has a photo of the 688 bearing in the Novatec A551SB hub. So I assume that the A211SB and A215SB hubs probably also uses 688 bearings. Otherwise, I would instead go with loose ball bearing hubs which are easier to service yourself without special tools or requiring you to build special jigs. But there aren't many loose ball bearing 74mm hubs. The only one I could find readily available are Tern branded, but most of them are solid axle with nuts instead of quick release skewer. The loose ball bearing hubs have low chance of you damaging it when servicing, and has better lateral stability. And if the cones become pitted, you could simply buy a the really cheap hub again for $20 and swap the cones and balls, whereas a version with cartridge bearings requires you to go through the trouble of extracting them and pressing new ones in. The only issue with loose ball bearing hubs is your ability to feel how much is good preload to apply when tightening the lock nuts.


Last edited by tomtomtom123; 06-09-19 at 11:49 AM.
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Old 06-10-19, 10:13 AM
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I attached STL 3d models for the puller and press jigs. They're sized with 0.2-0.25 tolerance for FMD printers.

I redesigned them to center the bolts during the operation, so there is less chance of the bearings tilting.

Remove the 2 hub end caps. Put one of the "puller2 m3 bushing-02-025-03" into the bearing and spindle, to keep the M3 bolt centered on the bearing and spindle. The 3 files have different tolerances in case your printer has a minimum wall thickness, of -0.2, -0.25, or -0.3mm. "Puller3 M3" is used to pull out the first bearing, using a M3x60mm DIN 912 bolt. You also need some large diameter washers and a nut on outside of the puller. You can also place a DIN 433 M3 narrow washer under the head of the M3 bolt to protect the inside of the spindle. Normal DIN 125 M3 washers are too large to fit through the 1/4" R4 bearing bore hole. You will need the long version of the hex allen key to reach the M3 bolt head, as it is too deep inside the spindle for a normal length wrench to reach.

Once you have 1 bearing out, you can use the same jig to pull out the other side, if you keep the spindle inside the hub.

If you want to take the spindle out before removing the 2nd bearing, you can switch to "Puller3 M6" instead and use a M6 bolt to press directly from the back side of the 2nd bearing. But then you won't be able to use the the "puller2 m3 bushing" to center the bolt.

To press in the new bearings, you press one side at a time, not both together. I made an error and did both together. Place only one DIN 433 8mm narrow washer inside the "press cup large", put in a M5x100mm bolt with a few large diameter washers on the outside of the cup, and put it on the side with the bearing to be installed. Do not use regular sized DIN 125 8mm washers because they're larger than the R4 hub bore hole and it will break your hub. Place the "press cup small without washer" part on the opposite open side with a few large diameter washers and a M5 nut on the outside, without a bearing. Then slowly turn the nut and press in the bearing until you start to feel increased resistance. Do not overtighten. You can occasionally remove the cups to see how far the bearing has gone in, and if it is still going in flat. My DIN 433 washer was 1.4mm thick. On my hub, one bearing was recessed by 1.3mm and the other by 1.7mm. So depending on your hub and which side you are pressing, the bearing might or might not be completely seated.

Then flip the tool around to press in the 2nd bearing. Make sure not to place any washers in between the "press cup small without washer" and the installed bearing, so that the "press cup small without washer" is only contacting the hub, and not the installed bearing. Remember to insert the hub spindle before pressing in the 2nd bearing. Otherwise you'd have to remove the bearings again to get it in.

After pressing the 2 bearings one at a time, one or both of the bearings are not yet completely seated by 0.3-0.4mm. So remove both cups, and place "puller cup small" on both sides (it has a 8mm diameter step inside, while the "puller cup small without washer" does not) with one DIN 433 8mm narrow washer inside each of the cups. Do not use normal DIN 125 washers. This makes the cups recess about 2.4mm into the hub bore hole. Thread in the M5 bolt with large diameter washers and a nut on the outside of the cups. Tighten the nut to seat the bearings fully. Don't overtighten.

If the 2 bearings are fully seated and in contact with the inner spindle, then turning the inner ring of one bearing should turn the inner ring of the 2nd bearing at the same time. insert the 2 hub end caps. Spin the wheel to see how it feels.

I take no responsibility. This is just how I worked on my hub. You do this at your own risk.

The cups are designed for 19.2mm hub diameter for the new Dahon kinetix front hubs with R4 bearings. You could possibly use the same design for the older Dahon hubs or Novatec hubs that are using 688 8mm bore bearings, but you'll have to resize the cups to fit. You'll need to ask me to send you the STP files instead of the STL files. The older Dahon hubs and Novatec hubs use threaded end caps instead, so you could press the M3 bolt against the back side of the cup, then you could possibly use a shorter 40 or 50mm long bolt.
Attached Files
File Type: zip
wheel.zip (404.4 KB, 1 views)

Last edited by tomtomtom123; 06-10-19 at 10:34 AM.
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Old 06-19-19, 05:54 AM
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One problem I noticed with the new Dahon Kinetix front hubs is that the pressed in end caps (not threaded anymore) changes angle slightly whenever you remove and reinstall the front wheel into the fork. The brake pads no longer center on the rim. So I have to recheck the brake alignment each time I reinstall the wheel. I no longer have a functioning old hub with the threaded caps, so I can't test the theory, but I assume that threaded caps might be a little bit more consistent in centering. But the cone and cup hub with loose balls is probably much more stable.
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Old 06-19-19, 09:59 AM
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I saw Phil Wood Co makes a 74 wide hub, just not shown on their regular website..

when you get bored with doing all those overhauls.



My Bi Fri Tikit came with a loose ball type hub , it's an easy rolling one..

Swapped to a Schmidt bolt skewer.. in place of lever QR one,,
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