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Old 09-07-2004, 08:31 AM   #1
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Default Rebound foamies Vs. stiffer springs?

Howdy folks

just wondering ... what do these foam discs' compression response curves look like? Linear, like a spring? or something else? If it's simply linear, then they're useless... if not, then what are they like?

Basically I'm trying to understand what using different foams brings more than simply using a stiffer spring... Basically it's a rebound Vs. spring discussion... what do you guys think? Are Rayspeed and the likes BS'ing us with 5 different foam density for shock inserts, or is it a real tuning aid?

Thanks,

Paul
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Old 09-09-2004, 02:54 AM   #2
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You gotta love internet forums... a nice, clean, technical thread, and ZERO answer... Sure, nitro Vs Electric is an easier discussion

Why do manufacturers offer these funky little foam discs for their cars? What do they do from a physical standpoint that springs can't do? Nobody cares, or nobody knows? Neither?

Later
Paul
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Old 09-09-2004, 03:04 AM   #3
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Default Foam

Hi lonestar,

In my point of view those foam parts inside your shocks are mostly for getting a better rebound.

I have them inside my Serpent shock's and rebound time has improved.

I see no connection between shockcap foam and harder/ softer springs.

I,m not sure about this.
The only thing I can tell you are my findings.
If you really want to know more about this maybe you can call some manufacturers or e-mail them.

Thomas
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Old 09-09-2004, 07:07 AM   #4
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Finally somebody interested in this topic

Obviously it does change the rebound... that's the whole point! There's more of it, but is it better, or worse?

Basically, with the foam disc and without any spring, the shock has a stronger springing action, that without the foam, like if you already had a soft spring on it. How is it different from less rebound (no foam) and a slightly stiffer spring? And if we don't know the physics behind it, can you describe the change on the track?

Paul
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Old 09-09-2004, 07:46 AM   #5
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Lonestar,

When I tried with allot of rebound my car felt really stiff, did not want to roll much at all and I got less traction!

But I still use a really stiff foam most of the time and bleed the shock's so there is very litle rebound! The stiff foam supports the bladder so that when you hit a bump or going fast left to right etc. the bladder wont be able to bump up in the opposite direction if you know what I mean......

I like the shocks to work as there was no bladder there at all, but with this setup they are far more consistent and easier to bleed!

Sometimes I use one O-Ring or soft foam to gain tracton when the surface is low traction!

I hope this make sense and that you got the answer you wanted!

Cheers,
Eirik Andreassen
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Old 09-09-2004, 05:19 PM   #6
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Hey
I don't now so much about the foam, but the bladders seem to make a difference. HPI stock bladders seem to be very firm (at least as hard as Rayspeed firm)).

Switching to Rayspeed soft felt like a 5w oil change softer to me.
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Old 09-10-2004, 12:49 AM   #7
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Thanks Eirik!

Robk: Sure, bladders make a difference, but it's interesting to hear you felt it like a "damping" difference rather than a "springing" one... mmmh.

Paul
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Old 09-10-2004, 02:10 PM   #8
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"Robk: Sure, bladders make a difference, but it's interesting to hear you felt it like a "damping" difference rather than a "springing" one... mmmh."


Do you think it could be like pack in an off road car? It seems like the bladder is going to take the initial force of the piston, and then the bladder "runs into" the foam. I have seen setups from Asian drivers who use o rings instead of foam. HMmmmm.....
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