Dampers

[Henderbt]

I know the many pro/cons of mtb shocks as opposed to a higher quality damper such as ohlins. I was wondering if any one can tell me if they've had a noticable difference the the handling characteristics of their car after switching to a higher end set of dampers. I understand the quality difference is substantial, but I'm curious if the money spent is worth it for our applicatoin, or if they are a bit overkill. Just trying to justify taking money out of a tight budget. thanks for any input guys.

[Jersey Tom]

Stock out of the box.. a MTB shock is probably going to be a rebound monster. Way overdamped. The Risses are like that at least, even in their 'FSAE spec.' Their build quality last year was crap. Hysteresis isn't bad though. But, your car will be way overdamped in roll and will have a tendency to jack down.

The new Foxes out of the box are not good for racecar use, with position sensitive damping as well as velocity. Yuck. Push revalves them getting rid of the boost valve and propedal at least, but the adjustments they give you aren't just R&C. Its like.. low speed rebound and high speed compression or I dont know what.

If you ran a Cane Creek with a high motion ratio, out of the box it might work well for you. Expensive though. $550 a pop.

To do dampers right, even if its Ohlins or what have you, you're going to have to revalve them to a rate that works for your specific car. Start by figuring out what damping rates you need on your car for bump and for roll. Then, talk to some shock companies, see if you can get dyno curves. Evaluate what the performance will be for what motion ratio you have.

[mtg]

Yes, dampers are a large part of making a fast racecar. However, just putting high quality dampers on a car doesn't make it fast. High quality dampers that are tuned for maximum performance make a car fast(er).

There's usually an over-generalization with FSAE dampers- people say "mountain bike shocks suck, get Ohlins", or something like that. The truth is some mountain bike shocks suck, while others (ie Cane Creek Double Barrel) are very good and work well on an FSAE car. The Ohlins dampers that are generally used on FSAE cars is the ST-44, which is the low end formula car damper from Ohlins. If you research the topic, you'll find out that the Double Barrel is very similar in design to the Champ Car level Ohlins TTX-40.

Generalizing a shock as "overdamped" out of the box isn't valid- that depends on the natural frequencies of the car (sprung and unsprung) along with motion ratio. Otherwise, I could go to competition and say "school X has 3 clicks bump on their Fox shox, and I have 4 clicks of bump on my Fox, so therefore I have a higher damping ratio in bump than they do". That's not true.

[js10coastr]

Originally posted by mtg:

Generalizing a shock as "overdamped" out of the box isn't valid- that depends on the natural frequencies of the car (sprung and unsprung) along with motion ratio. Otherwise, I could go to competition and say "school X has 3 clicks bump on their Fox shox, and I have 4 clicks of bump on my Fox, so therefore I have a higher damping ratio in bump than they do". That's not true.

like a "Rusty is running 800 lbs springs on his car" thing.

[Tony K]

Originally posted by mtg:
The truth is some mountain bike shocks suck, while others (ie Cane Creek Double Barrel) are very good and work well on an FSAE car.

That's because the Cane Creek Double Barrel isn't a mountain bike shock and Cane Creek had nothing to do with the design and development of the damper. And yes, the Double Barrel is very similar to the TTX-40 with the only major differences being that it's not a through rod damper and it doesn't have a solid piston (probably due to the limited bleed orifice sizing and non-interchangeable valves), but it was developed by Ohlins by combining TTX-40 technology with the packaging technology they used for the new Audi R10.

Being that you get a real 4-way damper in a smaller package than the ST-44 2-way for the same cost (give or take $50), it's a real sweet deal. With the Double Barrel, it's not only the quality of the damper that makes it nice (low hysteresis, decent piston design, hopefully won't leak like the Risse's do), it's the massive amount of adjustment that allows it to be tailored to a greater range of suspension designs and conditions.

Colorado-Boulder and Colorado State are teaming up in the near future to test the Double Barrel on our damper dyno, so I'll be able to give quantitative results later; however, from what I know about the TTX-40, my overall experience with Ohlins, and what I've heard from other people, the extra money you spend really does make a difference.

[mtg]

Originally posted by js10coastr:

like a "Rusty is running 800 lbs springs on his car" thing.

Hilarious. To his credit though, is he actually doing better than Rusty now, or should that be to Michael's credit?

[Jersey Tom]

I generalize the Risse Jupiter 5's as rebound beasts and most likely overdamped out of the box on us having a ~2.5Hz unsprung natural frequency and a motion ratio of 1.7 and with the rebound in full soft having shock velocity histograms that were split 75/25% R/C.

Yea. That bad.

[tech3d]

Hi everyone!

I've been travelling trough the posts and replies and have only read about a few brands of shocks, like Ohlins, tanner, Cane creek, fox, tanner...

I'm trying to choose a new couple of shocks for this year. Our budget is very low so I'm looking up to some other brand of mtb ones.

Here in Spain Fox are very difficult to get, so I'm considering other options: Kindshock, X-Fusion, Progressive suspension... Have you ever heard about these names or have any experience?

Many thanks for any help.

[Chris_S]

If you expect to throw any damper at any car and expect it to work at 100%, you'd be very wrong. Of course you need to have them re-valved to your needs.
I've had to have the shock on my mtb re-valved to match my weight, riding style, and also the bike.



5th Element (or Progressive) are realiable, as long as you get the newer versions, Older versions had a tendancy to blow up.

Havent seen many FSAE cars fitted with the 5ths, have seen a few with Manitou Swingers (Helsinki, possibly graz). The swinger uses the same technology as the 5th, as 5th liscence the progressive technology from manitou.

[tech3d]

I still don't know what you all mean with re-valve or re-shim the dampers.

Can you explain it in a couple of lines?

Thank you again

[B Hise]

Can you explain it in a couple of lines?

http://ohlins.com/Portals/0/documents/manuals/07425-01.pdf

[tech3d]

B-Hise, thank you for your input, but it is impossible for me to open that link. Would you be son kind to send me directly to my mail? amiaire_@hotmail.com

I have keep searching things about damper choice in this forums, and I have noticed that nobody sais to have an experience about the two kind of shocks. I mean, to have tested bike ones and have changed to racecar ones, with the imporovement in performance.

I would apreciate any comments about this.

[B Hise]

Tech3d, make sure you have adobe reader installed on your computer. I sent you the file anyhow.

What you really need to know about dampers is what you want the shock to do, what amount of damping force you want. Most shocks will allow you to do this. If I were you, I'd buy some ohlins and get my car done ASAP so you can test.

-Bryan