MTB shocks vs proper shocks

[clausen]

Hi,

Firstly, I'm just getting involved with FSAE for the first time.

What do you people know about just how well MTB shocks can work on these cars?

Their bore diameter is one thing that puts me off. Are they really capable of controlling a car, even this small, properly?

How about thier characteristics? Are there any that have the sort of force vs velocity curves that we'd like? (ie proper digressive)

Does anyone have any success revalving the run of the mill ones (fox, etc) to work properly?

Maybe the size isnt that bad a thing. I have heard of a works Van Diemen F ford that had some tiny shocks, similar size to MTB ones, which had Eibach written on them. This is on a very big budget car.

Thanks for any info,

Regards

Paul Clausen
Uni of Adelaide

[Angry Joe]

We use big ass Penske shocks. They are relatively heavy and a pain in the ass to package. They also perform superbly and we've never, ever had one leak or fail in the history of the team. If there's one place where you should sacrifice weight for performance, it's shocks in my opinion.

Are you sure the shocks were Eibach, or was it the springs?

Lehigh Formula SAE Alumni
Team Captain 2002-2003

www.lehigh.edu/~insae/formula (http://www.lehigh.edu/~insae/formula)

[ben]

We run Risse Jupiter 5Rs and we did our shakedown with a really old set that you could hear were full of gas bubbles.

When we reconditioned them (new seals, etc) the handling was transformed. Yaw response was dramatically better with the same suspension springs.

This clearly indicates to me that they are definitely adequate for Formula SAE. I'm by no means saying that they're the best dampers, but in terms of the performance vs. packaging compromise they are certainly better than some people think.

Angry Joe: As for Eibach, the British arm of the company makes some very neat dampers that have been used on FFords and F3s over here.

Ben

[Jarrod]

We have run Fox MTB shocks and springs on the Monash car, and I had similar concerns, coming from speedway, where the shocks get caned (rough tracks, huge unsprung weight). Had a quick chat with a guy from the Koni distributors in Melbourne at the Motorsports show, who told me they had tested a few MTB shocks for a team, and was very impressed with the quality of them, and had no hesitation in recommending them for use in FSAE. He was also very willing to help out with information. Can't find the card right now, but they were based in Melbourne's eastern suburbs.

Jarrod
Monash UNI FSAE

[woollymoof]

What Jarrod said has shot down what I'm gonna say, but anyway. Mountain bike shocks are generally designed for extremely large and fast compressions, ie jumping off a cliff, so are not really suited to the fine, intricate movements of FSAE. But anyway, Koni measured them and said they were ok, so go with that I reckon.

[spayce]

woolymoof, if that IS your real name...

The biggest problem in mtb is that we are weak, slow and have large reciprocating mass in 1/4hp legs. Kinematics can only do so much to stave off the inefficient 'bobbing' that occurs in dualies, so the brunt of pedaling efficiency is born by the specially developed low speed valving in the shocks. Especially circuits found in 5th elements, curnutts and swingers...(inbread really, all got the same parents)

excellent control at most shaft velocities, just watch your motion ratio's and alignment, they don't like anything but axial.

Given the reliability of mtb air sprung dampers... it's easy kilo lost?? http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[clausen]

Yes I'm looking forward to getting a 5th element shock on a damper dyno. They're pretty interesting bit of gear.

Regards

Paul Clausen
Uni of Adelaide

[woollymoof]

spayce, if that IS your real name...

The reason Fox? bought out the locking rear shock is because they are really crap at damping slow movements, every tried to ride a bike with dualies?

by the way it's woollymoof, not woolymoof.

[spayce]

look woolymuff,

Engineering trickery abounds and band aid solutions are put in place to keep unfit unsmooth riders happy. Some use basic valves to lock travel completely which require blow-off mechanisms so they don't shit themselves blah blah blah

the shocks previously mentioned have dedicated low speed damping circuits, under the guise of SPV to counter the low frequency resonance.

etc...

in conclusion.

been riding dualies for six years.

sorry for the insult i've obviously caused.
http://fsae.com/groupee_common/emoticons/icon_mad.gif

[woollymoof]

pretty fiery for your second post

[John Gregor]

I'd be very weary of 5th element type shocks and all mountain bike shocks for that matter. They are designed for mountain bikes after all. Unless you have run them on a damper dyno, i wouldn't trust them. Internet engineering can be dangerous.

[fsae_alum]

As stated, mountain bike shocks are REALLY made for a completely different application than racecar use. Yeah, they're light, they're cheap, and they're small... but so is a turd. Anyways, the late Carroll Smith addressed this issue year before last in his speech where he basically said that everybody should be running automobile racing shocks instead of mountain bike shocks. He was a judge (head judge) and so I think his opinion might matter.

In spite of...

[Jarrod]

sorry, forgot to mention in my earlier post (been a while since iv'e had to think about it), but valving was a concern. As the posts above state, MTB shocks are designed to operate in different conditions. I believe there is a kit available to modify internal valving, high speed shims etc. however I am yet to investigate this.

[J. Cheng]

Has anyone tried rebuilding/revalving Fox Vanilla units themselves? Is there a shop manual available for them? TIA

Joe

[Gareth]

We have found through dyno'ing both Risse Jupiter 5's and Fox Vanilla's that they're not particularly consistent. Perhaps if they were blueprinted, dyno'ed, re-valved, dyno'ed, re-shimed, and dyno'ed some more you could get close to a consistent setup. The trouble is that they're not built with sufficient precision to have them behave exactly the same (nor should they be for a mtb). I think the trouble is the time and monetary cost associated with going to a custom damper. There's a lot of work involved in determining the proper damping curves and then revalving/shimming to get those curves. But, hey, there's the people who don't have the money and the people who find the money...right Claude?

[fsae_alum]

Just remember the saying "You get what you pay for!" As my favorite bad kart driving FSAE judge from Belgium would ask "Does Ferrari win because they have the money, or do they have the money because they win?" Just something to think about!

In spite of...

[Sam]

I read on cornell's website that they redo the internals of their shockies.

Sam Graham
Engine Group Leader 2003
UQ Racing

[fade]

did the risse show similar dampening curves on the dyno to the fox?

[Scott Wordley]

Cornell actually made their own custom shocks this year. I asked Claude Rouelle about them and he said they were very good. Maybe Michael can shed some light on them... I haven;t been able to track down any pictures... yet.

Regards,

Scott Wordley

http://www-personal.monash.edu.au/~fsae

[clausen]

Making out own shocks is something thats crossed my mind, but to do it properly, its really a 4th year project on its own.

Regards

Paul Clausen
Uni of Adelaide

[Mick_P]

My first post boys so here i go...

In the Claude Rouelle Seminar I attended the topic of MTB shocks did arise and Claude went down the 'Ferrari comment' line & I have heard Carrol Smith did mention about the fact we shouldn't use them. My opinion is however if you can prove they work, then use them.
After all, the bottom line is that if you can justify everything on your car you will go far..

Oh, we used MTB shocks 2 yrs ago, and got canned about it, this years team is using \
http://fsae.com/groupee_common/emoticons/icon_razz.gif

Swinburne 2004 FSAE
Dynamics Leader

[Mick_P]

Cut off the end of the last post.. here it is....


"... Bilstein and we will go the same"

Swinburne 2004 FSAE
Dynamics Leader

[Dunford]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by J. Cheng:
Has anyone tried rebuilding/revalving Fox Vanilla units themselves? Is there a shop manual available for them? TIA

Joe<HR></BLOCKQUOTE>

Brown has run Fox Vanilla dampers for some years now with mixed results. This year I am planning on retaining the housings and modifying the internals. If anyone out there has modified Vanillas or similar MTB dampers and is willing to share info, did you resort to anything more radical than reshimming or, at most, drilling out/replacing the needle valve?

[Jakub]

Gday Pual,

I personally think MTB shocks can be used effectively in a FSAE car. We ran them for 2 years in our first two cars and didnt really have trouble with them. There is no doubt that the damper is more than capable of controlling the springs and masses, its just the problem of repeatability between dampers. It would be good to have left-right damper pairs within 5% of each other, when we tested ours they were more than 10% different.

We did go to a custom bilstein damper for the 3rd car, and the weight penelty is there, not only in the damper but the spring usually needs to be a larger ID for race/car dampers. As a damper it works quite well, although ours doesnt come with any external adjustment.

I asked the guys that do race dampers for a job and they said if they can get at the internals theres a good chance thay can modify most dampers to work for you.

Ive been thinking recently of using those a "air shocks" for MTB's. I had a word with Cluade about these and he said it could be a good idea (and at 200 odd grames it sounds really good), although it does have a very rising rate spring and this could be some trouble.

Jakub Zawada
UNSW

[Denny Trimble]

We used air spring shocks in '98 and '99. A couple things to think about:
-very high stiction/hysteresis from the air seal
-rising rate from adiabatic compression as you noted
-adding air pressure puts you further down this rising-rate curve
-changing air chamber volume is the only way to change how quickly this curve becomes steeper
-watch out for the Cane Creek "air damping" system. Compressible fluids for damping?

University of Washington Formula SAE ('98, '99, '03, '04)