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Discussion Starter #1
I've just installed gravel spec suspension on a Fiesta ST for Prepared category rallycross. Mostly firm to loose dirt...with gravel rally tires.

The new suspension has considerable front camber adjustment available and while maintaining required clearances I can adjust to as much as -3.5 degrees. My question is how much is desirable? I've never had this much adjustment available before so have no experience with it. Caster however is not adjustable due to shock tower rules in Prepared.

In asphalt autoX I can generally use as much camber as I can get. But I don't know if dirt is the same.
 

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I've just installed gravel spec suspension on a Fiesta ST for Prepared category rallycross. Mostly firm to loose dirt...with gravel rally tires.

The new suspension has considerable front camber adjustment available and while maintaining required clearances I can adjust to as much as -3.5 degrees. My question is how much is desirable? I've never had this much adjustment available before so have no experience with it. Caster however is not adjustable due to shock tower rules in Prepared.

In asphalt autoX I can generally use as much camber as I can get. But I don't know if dirt is the same.
I have little experience with this too, but recall that dirt is all about tire edges and asphalt is all about contact area. I would guess it's not a situation where max camber would be best. I'd throw it to the max both directions for some fun runs and note if it under or over steers as an indication of the grip change at the front.
 

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you have the stock ST knuckles, so the car remains very low?

After running the VW for a long time, I remain a bit concerned about FWD cars popping driveshafts if you change the suspension geometry too much.
 

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I have the M-sport Bilstein damper/spring kit on my as yet unfinished build. Like college, I seem to be dragging it out a bit more than ideal :D

They were on the order of $3k a few years back.
 

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Discussion Starter #7
My Fiesta ST gravel spec suspension is from Cusco, imported, adapted and installed by Yawsport in California. Am currently running stock height but have more droop than I need, so am limiting it.

Yawsport fits Cusco gravel spec suspension to several cars. He machines several of his own parts to complete the kit.
 

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Discussion Starter #8
you have the stock ST knuckles, so the car remains very low?

After running the VW for a long time, I remain a bit concerned about FWD cars popping driveshafts if you change the suspension geometry too much.
Yes...the car is currently stock height. But the Cusco/Yawsport suspension I mentioned brought so much droop the front CV joints locked up on the lift. Initially I fit droop limit straps to prevent that, but now I'm adjusting shock lengths etc, for a better fix.
 

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I can't remember if the ST struts are shorter, or if the knuckles are offset like the rear beam, or both.

Did both sides lock, or just the PAX side? I think it's the shorter of the two isn't it?

I pulled mine apart monkeying with the struts. What a pain in the neck to put back togther.
 

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Discussion Starter #10 (Edited)
You know...I'm not sure. I was working on the pass side, but I think I checked both sides as I was installing limit straps to protect the CVs. As to ST vs NA, I have no idea. Have no familiarity with the NA.

Nice thing about this suspension is it's double adjustable. So last night I raised the spring perch an inch, but independently shortened the shock an inch. So no net effect, but I now have one inch less rebound and one additional inch of jounce. So I can now remove the limit strap. Based on speed bump testing I think I have poor jounce travel. I can do a little more of this range adjustment, but perhaps I'll have to lift the ride height some. I've read that monotubes give up a little stroke compared to twin tubes due to the in-line gas pocket. So I may not have the max travel I'd like.

In fact, I'll make it a question for you rally guys. Given limited shock travel compared to off-road rigs, do you still try for equal jounce and droop travel or do you sacrifice droop travel to get additional jounce? RallyX courses are only smooth in the morning. :)
 

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In fact, I'll make it a question for you rally guys. Given limited shock travel compared to off-road rigs, do you still try for equal jounce and droop travel or do you sacrifice droop travel to get additional jounce? RallyX courses are only smooth in the morning. :)

I have operated in the "Is it broken?" realm of thought for the past 15+ years.

I have done little or no testing of almost anything for various reasons, and think that many, if not most, club level guys are in the same boat.

Doesn't travel just lower suspension loads and improve ride quality? What's the mechanism by which performance would improve, in terms of the car going faster and/or handling better?

Is it just a factor of saying that the mean surface roughness requires equal travel? What compresses must decompress? If that's the case, you wouldn't need equal travel unless you have equal damping rates would you?
 

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Discussion Starter #12
Someone, perhaps Alex, punched a strut through his shock tower. That's what we're trying to avoid by supplying adequate jounce travel. But since we have only so much total travel available you need to allocate it between jounce and droop. Track most often uses a 50/50 split, but they don't deal with rocks etc. I was wondering if you rally guys favored more jounce and less droop. That would not provide better handling but better reliability in abusive conditions. And allow you to press harder.
 

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How much travel are you guys working with?

I tend to go with the motorcycle 1/3 droop 2/3 bump rule. However, in rally I think if you have adequate bump to prevent bottoming, lots of droop is good because it tends to keep the wheels on the road. Steering, breaking, accelerating isn't very effective in the air.

If you look at the better cars, they tend to favor good handling setup and ride height with lots of droop travel to maintain control and land the jumps without bottoming.

If you don't have much to work with you just have to limit top speed to keep it controlled.
 

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Discussion Starter #14
Mine is an inverted strut so a little difficult to determine stroke since it's on the car. The polished hydraulic unit sticks up 6". That would imply 6" stroke at the strut and perhaps a bit more at the wheel given motion ratio. But I'm sure it won't actually stroke 6" because there's a bumpstop in there which takes away from stroke. Don't know what the Cusco bumpstop is but a similar Bilstein inverted strut uses a 67mm (about 2.5") bumpstop. Since it compresses significantly before becoming a thud, I figure I have maybe a 5" stroke at the strut.

I think it makes sense to go high on front jounce (bump) travel to maintain speed through the rough stuff, and high on droop in the rear to maintain contact in corners. The rear doesn't seem to bottom. And has no CV to damage.

I'm just finishing up my adjustments and decided the old O-ring tell-tale trick will work here. I tied a rubber cord around the hydraulic unit which will get pushed up as that unit descends into the threaded body. That should give me my jounce, droop and static height positions....and I can adjust from there.
 

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Someone, perhaps Alex, punched a strut through his shock tower.
i just noticed this thread sorry.
i didn't punch it through shock tower, mine are reinforced pretty good.
it was a tophat that failed.
M-sport recommended installing modified stock top mount which i did.
and they don't hold that well because made out of thin metal. took two rallies for one to fail.
now i take them off for inspection after every event and if one doesn't look good (dimple inside )then i just get a new one.
they're fairly cheap from a stealer.
and i use a sizable washer under it.
 
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