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Old 11-06-2010, 07:26 PM   #101
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I'm sorry, but this wasn't is response to anything that you and I were discussing. That is why there not a quote.

I was trying to move on with this thread so people can actually read what they came here for.



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You are talking about low speed rebound vs bump tuning front or rear in order to tune the transient handling response, and I don't disagree with the concepts.

The concept I disagree with is "bump damping is for unsprung weight, rebound damping is for sprung weight".
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Old 11-06-2010, 07:55 PM   #102
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Sorry about that.

I've said what I've needed to say... I just really hate the myth "bump damping is for unsprung weight". The reasons for softer bump then rebound damping have nothing to do with unsprung weight. Readers can decide for themselves based on our conversation.
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Old 11-06-2010, 08:04 PM   #103
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Bernie,
You're awesome for explaining all this. Realy, I've learned so much in this thread. Too bad Miata.net locked that thread...well too bad for them.

Question:
I have NA HD's on my daily driver so I simply want comfort and enough spring to keep the tires from rubbing the fenders; this is a problem with the 1.6 springs currently. Is 300f/200r too much spring for that shock if I want to keep the comfort? There are a couple small "jumps" on the way to work that I must take slowly. I have a spare set of Ground Control perches so I can run whatever spring I want.

Thanks,
Huslteratronicon
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Old 11-07-2010, 01:59 AM   #104
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I have a set of 300# rear springs on NA HD's. It's totally livable on western Pa back roads. I'm sure they could be improved on some with revalving. It depends on your budget and the sensitivity of your butt dyno.
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Old 11-08-2010, 09:50 AM   #105
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If you are simply trying to get by till you have more time or money, the HD's will get you by.

That spring rate will keep the tires from rubbing the fenders, but you will run into wheel hop issues with RR crossings and rough back roads.

Do you have adjustable coil overs on the shocks now?


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Originally Posted by hustler View Post
Bernie,
You're awesome for explaining all this. Realy, I've learned so much in this thread. Too bad Miata.net locked that thread...well too bad for them.

Question:
I have NA HD's on my daily driver so I simply want comfort and enough spring to keep the tires from rubbing the fenders; this is a problem with the 1.6 springs currently. Is 300f/200r too much spring for that shock if I want to keep the comfort? There are a couple small "jumps" on the way to work that I must take slowly. I have a spare set of Ground Control perches so I can run whatever spring I want.

Thanks,
Huslteratronicon
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Old 11-08-2010, 10:40 AM   #106
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What causes the wheel hop? And what would you do to fix it? BTW, I only notice the sensation of catching air on really big bumps.
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Old 11-09-2010, 12:23 PM   #107
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Wheel hop is no different than a stone skipping across a lake. The spring is pushing the tire into the pavement at a rate that "shocks" the tire making it lose traction.

Wheel hop comes from too high a spring rate, or not enough rebound. Either have the same effect.

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What causes the wheel hop? And what would you do to fix it? BTW, I only notice the sensation of catching air on really big bumps.
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Old 11-09-2010, 12:47 PM   #108
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Quote:
Originally Posted by Bernie S. View Post
If you are simply trying to get by till you have more time or money, the HD's will get you by.

That spring rate will keep the tires from rubbing the fenders, but you will run into wheel hop issues with RR crossings and rough back roads.

Do you have adjustable coil overs on the shocks now?
Right now I have stock 1.6 springs, the collars and ERS 450/325 springs are in a box (from when they were on the track car). I have tire rub now, but its comfy.
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Old 11-09-2010, 03:13 PM   #109
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A type of wheel hop is caused by a combo of heavy wheel, soft sidewall, and insufficient damping. Look at SUV's and pickups with live rear axles go over small sharp bumps. Boioioioioing. The bounce frequency you see is the unsprung weight bouncing against the the tire sidewall spring rate. Either bump or rebound damping will damp this.
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Old 11-09-2010, 08:37 PM   #110
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Bernie, are you referring to low and midrange rebound on the NA's? I got the impression that NA Billies have plenty of rebound at higher velocities.
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Old 11-09-2010, 08:48 PM   #111
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Yes, I am referring to the low and mid speeds. Bilsteins typically have a much larger bleed than I use, so it makes it a lot harder for them to make any changes on low speed rebound or compression. Once you take the excessive bleed out, tuning the low speed is a lot more effective.



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Bernie, are you referring to low and midrange rebound on the NA's? I got the impression that NA Billies have plenty of rebound at higher velocities.
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Old 11-09-2010, 09:14 PM   #112
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Can you explain what bleed is and what it does.
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Old 11-09-2010, 10:11 PM   #113
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Bleed is the bypass in the shock that allows oil to flow past the shims and not affect the valving. It basically allows for uncontrolled movement of the shock in both the rebound and compression stroke. Once the oil has maxed the flow rate of the bleed, it then acts on the shims.

Bleed in a shock affects the low speed more than the high speed, but it carries through the entire stroke diminishing a portion of the valving.

Most shocks use bleed as their adjustment, allowing more or less oil to bypass the shims.

This is where it gets good. You can valve two shocks to look the same on a graph, but have two completely different methods of valving. What I mean by this is that I can build a shock with a thicker shim stack and a lot of bleed, and I can build the other with a small bleed and thinner sealing shim on the face of the piston with a pyramid stack of shims and both will look the same. However, they will not feel the same nor perform the same. Understanding this, and being able to actually do it, is what separates shock guys.
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Old 11-10-2010, 11:20 AM   #114
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Quote:
Originally Posted by Bernie S. View Post
Bleed is the bypass in the shock that allows oil to flow past the shims and not affect the valving. It basically allows for uncontrolled movement of the shock in both the rebound and compression stroke. Once the oil has maxed the flow rate of the bleed, it then acts on the shims.

Bleed in a shock affects the low speed more than the high speed, but it carries through the entire stroke diminishing a portion of the valving.

Most shocks use bleed as their adjustment, allowing more or less oil to bypass the shims.

This is where it gets good. You can valve two shocks to look the same on a graph, but have two completely different methods of valving. What I mean by this is that I can build a shock with a thicker shim stack and a lot of bleed, and I can build the other with a small bleed and thinner sealing shim on the face of the piston with a pyramid stack of shims and both will look the same. However, they will not feel the same nor perform the same. Understanding this, and being able to actually do it, is what separates shock guys.
Bernie, WE NEED PHOTOS!!!!

What do these mythical pistons and shims look like? How do you control bleed; it is with different pistons or are there other methods. Photos, please.....
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Old 11-10-2010, 08:36 PM   #115
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Old 11-10-2010, 08:37 PM   #116
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That should work
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Old 11-10-2010, 09:27 PM   #117
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Do the NA shocks have digressive pistons?
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Old 11-10-2010, 10:30 PM   #118
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Just wanted to jump in and say thanks Bernie, for starting the thread and helping to educate us all. Your wealth of experience is really welcome here.

With regards to piston bleeds, we ended up tweaking the piston design on the 5100 to create the Xida's for exactly the reasons you mentioned. Gaining enough sensitivity on the low amplitude/high velocity end while still having the high force/low speed damping. Too much preload gained us low speed damping but made the high speed insensitive and more hysteresis prone I think. For a set of Xida triples on one particularly nose heavy and powerful SBF V8 Miata (2550lbs-490whp-57/43%) we ended just about choking the bleed off with a one off custom set of pistons just for that car.
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Old 11-10-2010, 11:30 PM   #119
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Quote:
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That should work
Bernie doesn't get off the hook that easily. I'm looking for close up photos of actual Bilstein dampers.
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Old 11-10-2010, 11:34 PM   #120
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Can you explain what preloading the spring accomplishes? Does it have an effect on the ability of the shock to control the spring?
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