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Redwood FUCA impressions

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dsgerbc

Active Member
Jun 4, 2019
1,154
1,001
Michigan
I kinda wanted more camber than my MPP v1 can provide, and decided to try the RW arms to see if it's possible to dial in some extra caster as well and see if I like it.
Don't see many reviews on the forum, so I'm gonna post my thoughts here.

Just got them delivered a few days ago. At a first glance, the RW arms at max caster setting should be capable of moving the upper ball join ~4 cm rearward.
IMG_20220412_182041.jpg

But, sadly, that much extra caster is impossible with cutting metal. W/o cutting anything at all you can get only a few mm before you start rubbing on the plastic wheel well liner.

IMG_20220412_191836.jpg

But, if you cut the plastic liner up to sheet metal, you can get about 2 cm total of rearward movement of the upper ball joint, which by my crude math would be about extra 2ish degrees of caster (upper-to-lower BJ distance is ~53 cm). One can also cut some sheet metal to gain more clearance, but I'm not doing that...

Now, the arm itself doesn't have as much curve as the MPP arm, so its upward movement is more limited, and even more so if you dial in more caster. However, for those on RW Ohlins, the reduced range of motion does not appear to be an issue at the recommended shock length. Here, I've compressed the shock to the point of riding the bump stop hard.
IMG_20220412_233821.jpg
And the arm to body clearance seems just enough not start bending stuff.
IMG_20220412_233807.jpg
I don't know if people with other coilovers could run into issues.

So far, I took a bunch of camber measurements at different levels of compression/steering angle. I can generally get like 1.6--2 degrees more static camber than with MPP v1 arms. Not sure my absolute camber measurements are as accurate as the relative ones, but at full compression (riding the bump stop) I was getting near 4.8 degrees static camber, and over 6 degrees with the steering wheel turned 180 degrees, where with MPP v1's the most I got was 3.2 degrees static and 4 degrees with 180 degree steering.

Will try to take some more measurements tomorrow, as well as check for wheel/tire clearance at the maximum feasible caster angle. I doubt the latter would be that useful, since the widest tire I have in my garage at the moment is just 265mm on an 18x9.5 +35 wheel. I do have some tall winter tires tho, will try those as well.

The RW's method of arm adjustment - threaded bolt near the bushings - is kinda a pain to work with even while using their recommended crowfoot wrenches with long extensions. I suppose with enough practice it may get less painful, but at the moment it's taking forever to get the arms loosened-adjusted-retightened.

Given this, I'll probably set some fixed setup that I can daily drive and not mess with much at the track/autox. I'm thinking of setting static camber at ride height of around 3.5ish degrees, max possible caster and drive like that for a while to see if it's livable.

If anyone has suggestions of what useful measurements I can take - I'm all ears.
 
So, a bit more data on the value of caster.
While I don't have an exact measure of how much caster I'm adding, the estimate is above - 2ish degrees.
So I compared the setups:
1) Added caster (about 6 turns on the adjuster on one side from fully treaded in), about 4.3 degrees static camber, with the shock just starting to get into the bump stop. Another way to measure it: about 338mm from the bottom of the fender to the center of the hub.
2) No added caster (about 2 turns of the adjuster on each side), 4.3 static caster at the same compression.

The dynamic negative camber typically steadily increases with the turn of the wheel up to around 150 degrees, stay nearly constant through 220ish degrees and then starts declining in absolute terms.
setup \ steering anglesteering straight90 degree steering180 degree steering
1 (with caster)-4.3-5.3-5.8
2 (w/o extra caster)-4.3-5.0-5.2

I think at ride height these settings will yield 3.5ish degrees.

So, I think there's some value in extra caster for our suspension setup.
 
So, a bit more data on the value of caster.
While I don't have an exact measure of how much caster I'm adding, the estimate is above - 2ish degrees.
So I compared the setups:
1) Added caster (about 6 turns on the adjuster on one side from fully treaded in), about 4.3 degrees static camber, with the shock just starting to get into the bump stop. Another way to measure it: about 338mm from the bottom of the fender to the center of the hub.
2) No added caster (about 2 turns of the adjuster on each side), 4.3 static caster at the same compression.

The dynamic negative camber typically steadily increases with the turn of the wheel up to around 150 degrees, stay nearly constant through 220ish degrees and then starts declining in absolute terms.
setup \ steering anglesteering straight90 degree steering180 degree steering
1 (with caster)-4.3-5.3-5.8
2 (w/o extra caster)-4.3-5.0-5.2

I think at ride height these settings will yield 3.5ish degrees.

So, I think there's some value in extra caster for our suspension setup.
Did you happen to measure what six turns on the turnbuckle is in terms of inches/mm?
 
Do these require the inner joint be removed from the car to adjust?
You mean the ball joint at the knuckle?
Technically no, but adjusting with the ball joint disconnected it a ton easier, IMO, and can be done with regular wrenches.
Adjustment w/o disconnecting the joint is kinda a pain, and needs crowfoot wrenches and long extensions.
Did you happen to measure what six turns on the turnbuckle is in terms of inches/mm?
I think the thread pitch is 2.0mm, so, about 12mm?


One more bit of info. Redwood moved the wheel sensor wire mounting points to the inner edge of the arm, taking out some of the slack. As a result, it seems that the infamous 'zip-tie to the knuckle' mod is neither required, nor possible. I did an event with these on, and did not get any rubbing. I'm only on a 265mm-wide rubber though, but the same rubber ate through a sensor before I zip-tied them.
 
You mean the ball joint at the knuckle?
Technically no, but adjusting with the ball joint disconnected it a ton easier, IMO, and can be done with regular wrenches.
Adjustment w/o disconnecting the joint is kinda a pain, and needs crowfoot wrenches and long extensions.

I think the thread pitch is 2.0mm, so, about 12mm?


One more bit of info. Redwood moved the wheel sensor wire mounting points to the inner edge of the arm, taking out some of the slack. As a result, it seems that the infamous 'zip-tie to the knuckle' mod is neither required, nor possible. I did an event with these on, and did not get any rubbing. I'm only on a 265mm-wide rubber though, but the same rubber ate through a sensor before I zip-tied them.
That is good data to have. 12mm difference net you 2 degrees of caster.
 
You mean the ball joint at the knuckle?
Technically no, but adjusting with the ball joint disconnected it a ton easier, IMO, and can be done with regular wrenches.
Adjustment w/o disconnecting the joint is kinda a pain, and needs crowfoot wrenches and long extensions.

I think the thread pitch is 2.0mm, so, about 12mm?


One more bit of info. Redwood moved the wheel sensor wire mounting points to the inner edge of the arm, taking out some of the slack. As a result, it seems that the infamous 'zip-tie to the knuckle' mod is neither required, nor possible. I did an event with these on, and did not get any rubbing. I'm only on a 265mm-wide rubber though, but the same rubber ate through a sensor before I zip-tied them.
It looks like it would require removing the two inner pick up points to then turn the bearings for adjustment.
 
Gonna bump this for an update. I did run it for a while with ~2 degrees of caster and max camber given that.
I made a mistake of checking for clearances with the bumpstops in place, which in reality led to some minor contact between the body and the arm under hard cornering. Not an issue for performance driving, but a safety issue for hitting potholes. So, I redid the clearance check with the bumpstops removed to simulate bad pothole hits and I think it's only safe to dial an extra degree of caster. Which is a shame.

Not sure I noticed much difference in feel while driving with +2 degrees of caster, but the front seemed much more eager to turn in slow-ish corners requiring plenty of steering, so I think I'm gonna supplement these with MPP offset bushings to get back to extra two degrees of caster on top of stock.
 
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This is what I found when we had the RW FUCA or any caster adjustable FUCA. You have to be careful of your camber/caster settings to make sure that you don't contact the chassis. Mine has some marks on it. The MPP V2.5 arm we have has been getting -3 camber at 365 to 370mm hub to fender. Other guys have gotten -3.5 and the only difference was they had the compression rod bearings with more positive caster dialed in. Since the RW FUCA doesn't have the curvature of the MPP or the UP just be aware of the articulation on the bearing they use. It's actually a bearing with a machined "pin" run through it. If you use their Ohlins dampers and set your shock lengths accordingly you should be fine but anyone else should definitely remove their springs and put the shock through it's complete motion, sway bar endlinks disconnected, so that you can confirm that the "ball joint" doesn't max out before the shock bottoms out. Not to mention checking the chassis for clearance under full compression.
 
Gonna bump this for an update. I did run it for a while with ~2 degrees of caster and max camber given that.
I made a mistake of checking for clearances with the bumpstops in place, which in reality led to some minor contact between the body and the arm under hard cornering. Not an issue for performance driving, but a safety issue for hitting potholes. So, I redid the clearance check with the bumpstops removed to simulate bad pothole hits and I think it's only safe to dial an extra degree of caster. Which is a shame.

Not sure I noticed much difference in feel while driving with +2 degrees of caster, but the front seemed much more eager to turn in slow-ish corners requiring plenty of steering, so I think I'm gonna supplement these with MPP offset bushings to get back to extra two degrees of caster on top of stock.
On average the OEM caster is somewhere in the +5 to +5.8 deg range depending on your ride height. So you're saying you're running north of 7 degrees of positive caster? Any pics of your front wheel with the car settled on the ground?
 
If you use their Ohlins dampers and set your shock lengths accordingly you should be fine but anyone else should definitely remove their springs and put the shock through it's complete motion, sway bar endlinks disconnected,
Not just the springs, the bumpstops as well. I had no contact when I fit them initially, when jacking the relevant arm until the corner was about to get raised from my lift's arm. It was not enough to simulate hard cornering or a bad pothole hit.

I'm at RW's recommended shock lengths (although I did have to adjust a few months back, since the springs appear to have settled some more since my initial install and the first adjustment for settling shortly after).

I'm definitely not at >7% any more. When I (likely) was, my not-too-meaty tires (255/265-wide, sub 26.2" diameter) weren't causing any rubbing issues.
 
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