Is there any reason not to use montain bike shocks?

[Paul V.]

Hey guys,
I appreciated your feedback on the previous question so I figured I would ask your opinion on another matter. I'm researching shocks, and people keep saying "don't use mountain bike shocks". But the best answer I can get why not is " because they're not for a race car." This is obviously not an adequate answer so I was wondering if anyone has any reasons for or against mountain bike shocks?
If this is a bad way to go where do you guys get affordable FSAE shocks?

Paul Vaughan
University of Alabama in Huntsville
FSAE Suspension

Kudos to McLaren for a podium this weekend

[Paul V.]

Hey guys,
I appreciated your feedback on the previous question so I figured I would ask your opinion on another matter. I'm researching shocks, and people keep saying "don't use mountain bike shocks". But the best answer I can get why not is " because they're not for a race car." This is obviously not an adequate answer so I was wondering if anyone has any reasons for or against mountain bike shocks?
If this is a bad way to go where do you guys get affordable FSAE shocks?

Paul Vaughan
University of Alabama in Huntsville
FSAE Suspension

Kudos to McLaren for a podium this weekend

[Big Bird]

Firstly, there are a lot of bloody good FSAE cars out there with mountain bike shocks, so any advice offered should be taken with this in mind. No they are not an ideal solution, but they are well good enough to get you into the top 10 of any FSAE event. Once your team is at a point where shocks are holding you back from further progress, and you know exactly why, that's when more expensive options need to be considered. Not many teams are at this sort of level, and a bit of honesty on this front can save a lot of money for more important things.

Having said that, I do know that the Fox Vanilla shocks that many of us use are being updated for downhill MTB use, and the mods are the exact opposite of what we want. The new ones have some valving system that locks the shock for low speed motion (pedalling) but frees it up for high speed (big hits). We rely on low speed damping to tune for corner entry and exit, so lock up is not a good thing for us.

Don't think that MTB shocks will ruin your chances in FSAE. They are cheap, reasonably adjustable, and are durable enough for what we do. The only failures I have seen are on cars where they did not fit spherical ends, so keep that in mind too.

How's that for a fence-sitting response http://fsae.com/groupee_common/emoticons/icon_smile.gif

Cheers

[Barnard1425]

Our team has had issues with mountain bike shocks that are not consistent from unit to unit. That is, one shock will have a different damping effect than another identical shock at the same setting. It's not that they're cheap shocks, it's just that they're not designed to be used in pairs. On a mountain bike there's just one at each end, and if they're a bit off you just adjust one until it feels good. It's not quite that simple in a formula car...

[Mi_Ko]

A bit out of topic

How expensive is a set of racing dampers. I can't find any sources for them.

In my experience you have to be careful with MTB shocks. If you set the compression to high, the seals can start to leak.

[Courtney Waters]

A quick note on the Fox Vanilla RCs, since quite a few teams use them and Geoff mentioned it in his post. I called Fox last week inquiring after a set for an off-road (non-MTB) project for work. Turns out the Vanilla RC is now discontinued in favor of their new DHX 5.0. They have a few left in stock, but no plans to make more. As Geoff said, the DHX 5.0 has "ProPedal" adjustment, bottom-out adjustment, and a schraeder valve to adjust compression. Maybe they could still be made to work, but it doesn't look like it would be as convenient as the Vanilla RC.

[1975BMW2002]

WE used MTB air shocks/springs last year, and I made everyone on the team this year swear that they would not even mention the word air shock again. I am not saying that MTB shocks are bad. I think a proper spring damper combo is great. but I am talking about the one where it has a good old fashioned coil spring. Do NOT use the shocks where your entire spring is an air bladder unless you are really good at design and can work through all of the pitfalls of nonadjustability that you will be stuck with.

When you use an air bladder as a shock your ride height and spring stiffness are both functions of air pressure. There is no way to change one without the other. You can always use adjustable rod ends on your pull/push rods to adjust height, but then you are messing with the geometry of how your bellcranks are supposed to sit at various points in the travel. This killed us. We had no way of lowering our car to the point that we wanted while still maintaining proper geometry and getting the intended spring rate.

The air bladder spring shcok contraptions are also really bad with stiction. they are not smooth at all. This makes setting your wheel weights innaccurate.

It is only at best a few pounds savings for hours of headaches. Just don't do it.

Whew... I'm done.

Bill

[RaID]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Mi_Ko:
A bit out of topic

How expensive is a set of racing dampers. I can't find any sources for them.
<HR></BLOCKQUOTE>

im pretty sure here in Australia a set of Penske 1/4 Scale Dampers were using are
$400AUD per damper

[B Hise]

I must agree with Bill, I worked on that car with Bill. Those dampers are no good. We will be using a regular spring/damper unit this year.

Bryan

[Mi_Ko]

Thanks for the info RaID!

That's around 250€ if my calculations are correct.
And I can get Fox vanilla for around 230, which is nearly the same.

And I assume the quality of the penske is on a much higher lever than that from fox.

[Brian Smith]

Hey Raid, Is that for 8100 series dampers? I cant find anything on "1/4 Scale".

[Charlie]

I wanna say he means 1/4 Midget shocks, which are not adjustable.