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Yes
Best fork bushings?
- Thread starter concours
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- Nov 26, 2009
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Concours - The slit is there because with Turcite you must account for thermal expansion. You can make an accurate bushing but without the slit the bushing can heat up and distort. But with the slit the bushing canl lengthen around the circumference and the slit will get smaller instead of binding. You get tighter clearances with the slit that you can get without it. The bushings aren't the problem. The problem is that some aftermarket tubes (like yours) are out of spec. One size does not fit all - it leaves a sloppy fit on smaller factory spec tubes.
Note that the Teflon bushings are also slit.
I think the slit is what Constantino missed when he copied my bushings - without the slit they were binding up and Kenny reported fork chatter. That fork chatter could have caused a crash and he could have been injured. Like I said I was sponsoring Kenny at the time and helping him. Why didn't Kenny just ask for them? I would have given him the bushings for less than the cost of material and they would have worked fine. But he went behind my back and Constanino's copies failed. Not cool.
I've already been through Teflon bushings. They wore out. When the Teflon wears off you have metal to metal contact and possible damage. The only way to avoid that is to dissassemble the forks to check and/or replace them. The Turcite bushings are not showing any wear and the forks work beautifully. They are slippery and they show no wear on the fork tubes. I could go back to Teflon anyday but I think that would be a step backward.
Note that the Teflon bushings are also slit.
I think the slit is what Constantino missed when he copied my bushings - without the slit they were binding up and Kenny reported fork chatter. That fork chatter could have caused a crash and he could have been injured. Like I said I was sponsoring Kenny at the time and helping him. Why didn't Kenny just ask for them? I would have given him the bushings for less than the cost of material and they would have worked fine. But he went behind my back and Constanino's copies failed. Not cool.
I've already been through Teflon bushings. They wore out. When the Teflon wears off you have metal to metal contact and possible damage. The only way to avoid that is to dissassemble the forks to check and/or replace them. The Turcite bushings are not showing any wear and the forks work beautifully. They are slippery and they show no wear on the fork tubes. I could go back to Teflon anyday but I think that would be a step backward.
Last edited:
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- Oct 12, 2009
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When using solid Turcite bushings you need to account for thermal expansion (slits) because the large volume of plastic you use expands a lot. With temperature change plastic changes volume a lot more than metals (almost 10x steel). That is why most plastic bushings are thin wall injection molded parts, if you minimize the volume of plastic used, you minimize the dimensional change. When you replace a chunky OEM metal bushing with a chunky plastic bushing, you can introduce some unforeseen problems like this. With a mostly metal DU bushing, the small volume of Teflon used (only the thin surface touching the fork tube) makes the thermal expansion relative to metals negligible, allowing closer and more consistent clearances. They are slotted because of the high quantity manufacturing technique from long strip that is sintered, pressed to precision thickness, cut, and coiled, not for necessity to compensate for material swelling. These are not concepts and techniques that I invented, they are generally accepted design principles that bushing manufacturers publish and encourage engineers to use.
>>The Turcite bushings are not showing any wear and the forks work beautifully
You seem to have removed the pictures from a previous thread I replied to that pointed out that machining marks worn away in only one area means that only that area was in contact with the tube: https://www.accessnorton.com/NortonCommando/synthetic-fork-bushings-2019.28758/#post-438991 And the wear was in the upper area near the flange, where there is more material, so more volume change as described above. Also, IMO with the load ratings of Turcite the length of your upper bush should be cut by half, which would provide smoother fork action under braking load, significantly cut material cost, and still be within the material's capabilities. And contribute less to the volume change issue.
I don't want to get into a pissing match of who stole what from you since nobody did. You used a newer material designed for high load bushings to make a high load bushing to improve an obsolete metal OEM design. That does not give you an exclusive license to that concept. I do agree that if I was selling a Turcite bushing set, you would have somewhat of a point to complain about, but I am not. I tested it and found it wanting and came up with another solution, of which I find the machined upper bush/seal holder to be the more significant improvement and don't see anything that you have done similarly. You find that Teflon bushes wear too quickly. The entire telescopic fork manufacturing industry disagrees. As do I. Maybe you did something wrong. I have seen (and felt!) Roadholder tubes so badly worn from the OEM bronze upper bush that they would likely tear up a new Teflon bushing, but the solution is to fix the tube, not the bush!
As an aside, my name is easy: Cosentino.
To all else being entertained here: you be the judge. But at least go out for a ride!
>>The Turcite bushings are not showing any wear and the forks work beautifully
You seem to have removed the pictures from a previous thread I replied to that pointed out that machining marks worn away in only one area means that only that area was in contact with the tube: https://www.accessnorton.com/NortonCommando/synthetic-fork-bushings-2019.28758/#post-438991 And the wear was in the upper area near the flange, where there is more material, so more volume change as described above. Also, IMO with the load ratings of Turcite the length of your upper bush should be cut by half, which would provide smoother fork action under braking load, significantly cut material cost, and still be within the material's capabilities. And contribute less to the volume change issue.
I don't want to get into a pissing match of who stole what from you since nobody did. You used a newer material designed for high load bushings to make a high load bushing to improve an obsolete metal OEM design. That does not give you an exclusive license to that concept. I do agree that if I was selling a Turcite bushing set, you would have somewhat of a point to complain about, but I am not. I tested it and found it wanting and came up with another solution, of which I find the machined upper bush/seal holder to be the more significant improvement and don't see anything that you have done similarly. You find that Teflon bushes wear too quickly. The entire telescopic fork manufacturing industry disagrees. As do I. Maybe you did something wrong. I have seen (and felt!) Roadholder tubes so badly worn from the OEM bronze upper bush that they would likely tear up a new Teflon bushing, but the solution is to fix the tube, not the bush!
As an aside, my name is easy: Cosentino.
To all else being entertained here: you be the judge. But at least go out for a ride!
IMHO this is taking this crap way over the line
johnm
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Over the years I found straight and parallel stanchions and sliders to be actually much harder to achieve than any issues with fork bushes.
Just because it happened that way I actually have Jim's bushes at the bottom and CNW lengthen bushes at the top. But getting it smooth with no stiction required hours of checking and straightening fork yokes reassembling and then dismantling again and again.
Then the concept of bouncing the forks before tightening the axle pinch bolt and even the mudguard stays didn't do much for me to align the forks. I found I had to carefully lever the fork leg over in tiny steps until I found the sweet spot and could tightening the pinch bolt.
So fork bushes are maybe 20 % of the solution for me. Getting the forks straight and parallel was way harder to acheive.
Just because it happened that way I actually have Jim's bushes at the bottom and CNW lengthen bushes at the top. But getting it smooth with no stiction required hours of checking and straightening fork yokes reassembling and then dismantling again and again.
Then the concept of bouncing the forks before tightening the axle pinch bolt and even the mudguard stays didn't do much for me to align the forks. I found I had to carefully lever the fork leg over in tiny steps until I found the sweet spot and could tightening the pinch bolt.
So fork bushes are maybe 20 % of the solution for me. Getting the forks straight and parallel was way harder to acheive.
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And that is?
I have more than that. Does that make me 2x as smart, or a better engineer?
I sincerely doubt it.
Jerry Doe
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It’s getting old. We are such a small group. Jim, I have nothing against you, but you are causing me problems. I am getting complaints from other members and it’s getting worse. I am on vacation right now in the middle of a 3000 mile road trip on Harley. The last thing I need is to be dealing with on going complaints from other members about your posts. I don’t care about your products. I don’t care about anyone’s products. It’s fine for members to post about their products. What I care about is members complaints to me. I want the forum to be a happy place. I am banning you from the forum for 2 months. Remind me then if you want to come back and we will consider it.
Jerry
Jerry
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