spdingtkts
Mechanical
How do you determine what the largest clamping shim OD you would use with a shim stack?
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Clamping Shim OD
- Thread starter spdingtkts
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Thanks for the MEI reference. I found it searching after realizing Traxxion didn't have any shims listed on their website. I believe I will need 20 mm ID x 24mm OD ring shims, which may be difficult to find.
I may have to buy someone in our machine shop a bottle of Jack Daniels. If I make the ring shims thick I can always fill up the interior with centering shims to adjust the preload.
I may have to buy someone in our machine shop a bottle of Jack Daniels. If I make the ring shims thick I can always fill up the interior with centering shims to adjust the preload.
edrush,
Don't forget that the centering shim will form part of the shim stack & you have to take it into account. Also from my limited experience (some of the others here may be able to provide more information) pre-loaded shim stacks are not universally used. You also may want to consider a two stage stack. What is the exact problem you are experiencing & what is your current shim arrangement.
Don't forget that the centering shim will form part of the shim stack & you have to take it into account. Also from my limited experience (some of the others here may be able to provide more information) pre-loaded shim stacks are not universally used. You also may want to consider a two stage stack. What is the exact problem you are experiencing & what is your current shim arrangement.
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spdingtkts
Mechanical
Traxxion does not list individual shims for sale but I am sure they would sell you whatever you need.
The OD on the Traxxion preload ring for the 25 mm pistons is 22 mm.
The OD on the Traxxion preload ring for the 25 mm pistons is 22 mm.
Yeah, good point on the centering shims. Thanks.
My problem was too much high speed compression. My suspension worked great in round whoops and for jumping, but any square edge bumps hammered me. The front beat me to death and the rear wanted to pile drive my head into the ground.
I tried a dual stage shim stack in the front and it resulted in very poor performance. It is possible that I just missed the mark, but it was so bad I wrote it off as a feasible approach.
I also tried Delta Valves in the front, then finally drilled out both stock "pistons". Current stack is a straight progressive (in size) of one each 24-22-20-18-16-14-? mm OD. I can't remember the smallest diameter. All .1 mm thick. As I recall the stock setup had two 24mm and two 22 mm shims. As you can see I am never going to make it as a tuner, even for my own bike, unless I start taking good notes.
The front end is pretty good now with the bleed valve shut off. From a philsophical standpoint I want to try some preload in the front and I need to stiffen it up a touch anyway, since I believe the orginal problem was the pistons more than the stack.
By the way, this is a 95 CR500 (I think the only year with Kayaba). I recently rode a new CRF450 and decided the motor was just as brutal as my 500, so I lost my desire to upgrade. I didn't push the CRF suspension because I had just wadded my bike I didn't want to wad up the nice man's new CRF. I was also experiencing some pain.
My problem was too much high speed compression. My suspension worked great in round whoops and for jumping, but any square edge bumps hammered me. The front beat me to death and the rear wanted to pile drive my head into the ground.
I tried a dual stage shim stack in the front and it resulted in very poor performance. It is possible that I just missed the mark, but it was so bad I wrote it off as a feasible approach.
I also tried Delta Valves in the front, then finally drilled out both stock "pistons". Current stack is a straight progressive (in size) of one each 24-22-20-18-16-14-? mm OD. I can't remember the smallest diameter. All .1 mm thick. As I recall the stock setup had two 24mm and two 22 mm shims. As you can see I am never going to make it as a tuner, even for my own bike, unless I start taking good notes.
The front end is pretty good now with the bleed valve shut off. From a philsophical standpoint I want to try some preload in the front and I need to stiffen it up a touch anyway, since I believe the orginal problem was the pistons more than the stack.
By the way, this is a 95 CR500 (I think the only year with Kayaba). I recently rode a new CRF450 and decided the motor was just as brutal as my 500, so I lost my desire to upgrade. I didn't push the CRF suspension because I had just wadded my bike I didn't want to wad up the nice man's new CRF. I was also experiencing some pain.
Sounds more like you have a problem with the balance belween your bleed circuit & cartidge. If you have the low speed bleed closed you may want to try a heavier grade oil to get yourself some adjustment & shim back accordingly. If your bike handles jumps ok but is upset by square edge bumps it is likely to have a bleed/blow off problem. I think a pre loaded stack will only make matters worse.
Also the clamping shim (smallest shim) od will have a great influence on your shim stack. What is your piston / cartridge dia & shim id.
Also the clamping shim (smallest shim) od will have a great influence on your shim stack. What is your piston / cartridge dia & shim id.
I now see the power of the clamp shims. And yes, changing the oil would stiffen up the entire circuit. But changing the oil is just as much work as revalving and I have no experience with oil viscosity changes.
My front end is pretty light, but if I can soften the rear to get some load off the front and also get rid of that nasty high speed kick I think I will be close.
Yes, my bike has a mid valve. The damping rod has a piston on the end with a rebound stack. On the top side of this piston is a check washer/shim (or two) with a scrawny coil spring behind it. I concluded the midvalve did not provide any compression damping except that created by the orifices in the piston, which I drilled out. I wanted the damping controled by the shim stack, not orifices. Now that I have removed the anodize from the piston orifices I suspect the holes may start growing in size.
Why do you say the midvalve can make the the suspension harsh? I do believe I fall into the "old and slow" rider catagory.
The problem with suspension design/tuning is that there are way to many variables. If it was simple the tuning wouldn't be nearly as much fun, but the riding would be a lot more fun.
My front end is pretty light, but if I can soften the rear to get some load off the front and also get rid of that nasty high speed kick I think I will be close.
Yes, my bike has a mid valve. The damping rod has a piston on the end with a rebound stack. On the top side of this piston is a check washer/shim (or two) with a scrawny coil spring behind it. I concluded the midvalve did not provide any compression damping except that created by the orifices in the piston, which I drilled out. I wanted the damping controled by the shim stack, not orifices. Now that I have removed the anodize from the piston orifices I suspect the holes may start growing in size.
Why do you say the midvalve can make the the suspension harsh? I do believe I fall into the "old and slow" rider catagory.
The problem with suspension design/tuning is that there are way to many variables. If it was simple the tuning wouldn't be nearly as much fun, but the riding would be a lot more fun.
Oil viscosity is just as important as valving. Some forks run a midvalve, ie. The check valve shim (on the rebound valve) lift is restricted to say 0.5mm and a shim stack is in place of the thick check washer. This allows for a light low speed compression circuit & a heavy high speed circuit.
btw I think stock compression stack for a 1995 CR500 is,
22 x 0.1
22 x 0.1
21 x 0.1
21 x 0.1
20 x 0.1
19 x 0.1
19 x 0.1
18 x 0.1
17 x 0.1
16 x 0.15
14 x 0.15
12 x 0.15
11 x 0.25
Which part of the valve did you drill, also standard KYB 25mm valves are steel, did you buy the bike second hand.
The standard transfer ports on KYB rebound valve are very large & should not affect the compression circuit to a noticable effect. From your description it sounds like you drilled the rebound circuit. Also removing anodising will not cause the holes to grow in size unless it is where the shims are seated on the valve.
Port sizing does not need to be as large a some people think. Often it is used to control the way the shims deflect. You can design pistons to be digressive though to being velocity dependent to give characteristics that you are after, but this sort of stuff is usually used only at factory team level.
Also if the rear is kicking hard, how? I suggest you sort out the rear before you start on the front.
Regards,
MB
btw I think stock compression stack for a 1995 CR500 is,
22 x 0.1
22 x 0.1
21 x 0.1
21 x 0.1
20 x 0.1
19 x 0.1
19 x 0.1
18 x 0.1
17 x 0.1
16 x 0.15
14 x 0.15
12 x 0.15
11 x 0.25
Which part of the valve did you drill, also standard KYB 25mm valves are steel, did you buy the bike second hand.
The standard transfer ports on KYB rebound valve are very large & should not affect the compression circuit to a noticable effect. From your description it sounds like you drilled the rebound circuit. Also removing anodising will not cause the holes to grow in size unless it is where the shims are seated on the valve.
Port sizing does not need to be as large a some people think. Often it is used to control the way the shims deflect. You can design pistons to be digressive though to being velocity dependent to give characteristics that you are after, but this sort of stuff is usually used only at factory team level.
Also if the rear is kicking hard, how? I suggest you sort out the rear before you start on the front.
Regards,
MB
I'm working of memory here because the parts are in my bike. And my memory is even worse than my note taking habits.
You may very well be right on the diameters and arrangement, but I do not remember two 19's. I remember two of the two largest diameters.
I am pretty sure I drilled both the compression valve ports and the midvalve piston.
I do have a midvalve and I shortened the travel on the midvalve check shims and I think I added another shim to stiffen it up. The check shim arrangement confused me. I didn't think it would have any significant effect on damping. It's nice to have some confirmation that those shims do have a purpose beside just being a check valve.
I will work on the rear before I do any more work on the front. The rear end kicks on sharp edged bumps. Every once in a while it kicks me in the arse and scares the pants off me. Plus I now have a balance problem. I was very suprised the Delta Valve didn't solve that problem because it is a blow off valve.
At this point I am a bit skeptical about digressive piston designs. But I would probably need to spend many hours studying my fluid dynamics book (or build a test bench) to form an intelligent opinion.
I bought the bike new.
You may very well be right on the diameters and arrangement, but I do not remember two 19's. I remember two of the two largest diameters.
I am pretty sure I drilled both the compression valve ports and the midvalve piston.
I do have a midvalve and I shortened the travel on the midvalve check shims and I think I added another shim to stiffen it up. The check shim arrangement confused me. I didn't think it would have any significant effect on damping. It's nice to have some confirmation that those shims do have a purpose beside just being a check valve.
I will work on the rear before I do any more work on the front. The rear end kicks on sharp edged bumps. Every once in a while it kicks me in the arse and scares the pants off me. Plus I now have a balance problem. I was very suprised the Delta Valve didn't solve that problem because it is a blow off valve.
At this point I am a bit skeptical about digressive piston designs. But I would probably need to spend many hours studying my fluid dynamics book (or build a test bench) to form an intelligent opinion.
I bought the bike new.
OK, I'm back at it. Working on the rear end now. I will remove my Delta Valve. I am pretty sure the Delta Valve is essentially a blow-off valve (i.e no progressive resistance once the valve opens). I believe if the Delta Valve didn't cure my high speed compression problem, no change to the external valve will. I am going back to the stock external valve.
My shock only had 70 psi, which I suspect is due to some Delta Valve leakage. Recently I have not been able to find a decent rebound setting, and for now I am blaming it on the low pressure.
The stock internal stack is (95 CR500):
format = (# of shims) OD x thickness
--Rebound side--
(3) 18 x 1.0 washer
(1) 21 x 3.0 washer
Shims:
(1) 25 x .31
(2) 26 x .3
(2) 28 x .3
(2) 30 x .3
(2) 32 x .3
(2) 34 x .3
(2) 36 x 3
(1) 26 x .1
(10) 36 x .15
--Piston/Valve body--
(12) 40 x .15
(1) 34 x .1
(1) 28 x .1
(3) 40 x .3
(2) 38 x .3
(1) 36 x .3
(1) 34 x .3
(1) 32 x .3
(1) 30 x .3
(1) 28 x .3
(1) 26 x .3
(1) 24 x .3
(1) 41 x 4.5 washer (thick sucker)
--Compression side--
Rebound plan: I will move the 26 mm shim to the middle of the 36mm shim pile. This should make the rebound more progressive. I am very tempted to make the rebound side an orifice type by getting rid of the shim stack and spacing that very thick 41 mm washer X distance from the valve. But I have no idea what X should be and if I take a guess I am almost certian to be re-valving after my first ride.
Compression strategy: The dual stage stack seems to explain the high speed kick. So I will remove the 34 and 28 OD shims to eliminate the dual stage. I will need to remove some 40 mm shims also, but I am not sure how many. Hmm, this is a difficult decision. I think I'll remove two of the .3 thick 40 mm shims.
Yes, those valve bodies are steel. I will probably drill out the compression ports in the valve a bit just to make sure they aren't contributing to my problem.
By the time any of you read this everything should be buttoned up, so I guess this post is mute. Sure hope my guess is correct on how many 40 mm shims to remove. I took out a lot of stiffness, but then then again the rest of the stack will be there for support (which it wasn't until the first stage bottomed out). Something tells me I will be able to use any info you guys might be willing to share when I re-valve again!
This certianly is a brain teaser. Is this a parallel or a series system? Some of both I guess.
Wish me luck.
My shock only had 70 psi, which I suspect is due to some Delta Valve leakage. Recently I have not been able to find a decent rebound setting, and for now I am blaming it on the low pressure.
The stock internal stack is (95 CR500):
format = (# of shims) OD x thickness
--Rebound side--
(3) 18 x 1.0 washer
(1) 21 x 3.0 washer
Shims:
(1) 25 x .31
(2) 26 x .3
(2) 28 x .3
(2) 30 x .3
(2) 32 x .3
(2) 34 x .3
(2) 36 x 3
(1) 26 x .1
(10) 36 x .15
--Piston/Valve body--
(12) 40 x .15
(1) 34 x .1
(1) 28 x .1
(3) 40 x .3
(2) 38 x .3
(1) 36 x .3
(1) 34 x .3
(1) 32 x .3
(1) 30 x .3
(1) 28 x .3
(1) 26 x .3
(1) 24 x .3
(1) 41 x 4.5 washer (thick sucker)
--Compression side--
Rebound plan: I will move the 26 mm shim to the middle of the 36mm shim pile. This should make the rebound more progressive. I am very tempted to make the rebound side an orifice type by getting rid of the shim stack and spacing that very thick 41 mm washer X distance from the valve. But I have no idea what X should be and if I take a guess I am almost certian to be re-valving after my first ride.
Compression strategy: The dual stage stack seems to explain the high speed kick. So I will remove the 34 and 28 OD shims to eliminate the dual stage. I will need to remove some 40 mm shims also, but I am not sure how many. Hmm, this is a difficult decision. I think I'll remove two of the .3 thick 40 mm shims.
Yes, those valve bodies are steel. I will probably drill out the compression ports in the valve a bit just to make sure they aren't contributing to my problem.
By the time any of you read this everything should be buttoned up, so I guess this post is mute. Sure hope my guess is correct on how many 40 mm shims to remove. I took out a lot of stiffness, but then then again the rest of the stack will be there for support (which it wasn't until the first stage bottomed out). Something tells me I will be able to use any info you guys might be willing to share when I re-valve again!
This certianly is a brain teaser. Is this a parallel or a series system? Some of both I guess.
Wish me luck.
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