Negative Camber Topic is solved

[Tonyx]

I just filled up very empty(indicated 0 miles to empty) with 15 gal. Trip odometer was 400 miles. So that's about 27mpg. That's what I'd expect and have had in the past. I'm happy with that for the level of comfort and utility. Those are commuting mile btw at 50 miles/day.

In comparison, my 2015 Ford Focus with 2.0L got 38mpg over 1700 mile trip to and from Boston last week. That's with A/C on and 75mph average speed, mostly all on highway.

Fuel cost difference between the two cars would have been $41 at $2.25/gal fuel cost. Not a deal breaker but a satisfaction I've burned less fossil fuel than if I had taken my XC70.

[mrbrian200]

I'm in the category: like something nicer, don't mind spending a -little more- in gas in/around town so long as it isn't a total guzzler (Ugh BMW, MB) but when I go longer distance I'm object to needlessly throwing away a ton in gas$ just to get there.
No go's are major catastrophic mechanical issues such as 2G-Early 3G Acura TLs (rotten trannys) P2 "T6" Volvos (again, rotten trannys) or cheap looking gawdy plastic center console/stack (just about everything else).

I do really like where Volvo/Greely is going with regards to styling on the new SPA vehicles, but they really need to get the curb weight down on the sedans. The new S90s are a good 800 lbs more than should be considered acceptable. Gas is relatively cheap at the moment but we all know that is temporary. Someday when prices spike back up weight will be Volvo's Achilles heel on these new sedans, as will be with many other heavy mid range luxury models that attract price conscious buyers who by nature are more sensitive to this. People who don't care buy SUVs and high end muscle. Volvo engineers led the way through the steel shell era with regard to structural resilience/safety. But a new era is dawning: light weight composites. I hope they don't back themselves into a weighty corner with the SPA platform and find themselves once again behind the times as they were during the Ford years, just in a different design area.

On a note: week ago Saturday I drove from 20mi NE of downtown Colorado Springs (Falcon/Peyton) to Denver round trip on a hair less than 1/4 tank (approximately 4 gallons). The major stretch along I-25 has a speed limit of 75, traffic moves at 80. Pleased with that to say the least. Calculates to 38mpg neighborhood. Very pleased.

[mrbrian200]

Update. Another long trip to a wedding. South Bend IN to Rutland VT (800mi give or take a few) on 1.5 tank fill, or approximately 22 gallons (premium). More than half of that on rural interstates with traffic flow between 75-80mph. Neighborhood 37mpg. At those speeds I consider that impressive for a mid size fully loaded to GVWR with 3 people and luggage.

I'm pretty much down to objectionable handling issues on bumpy/uneven side roads via the front end. Handling and noise improved with a bushing between the strut top washer and mount bearing cut from a spare bump stop. I had previously tried a spacer/washer cut from a used tire sidewall, but that was too stiff and transferred noise and vibration from small pavement "cracks". The material from a (Monroe branded) bump stop seems to have the right qualities both for handling and probable longevity, controls travel but is still able to "squish" a bit and absorbs noise instead of transferring it through the chassis. Now I'm down to the issue of too much play in the control arm front bushings. Had I realized this was in inherent design flaw (some suggest this bushing isn't robust enough for the weight of the car), instead of replacing the control arms when I bought the car (OE bushings were shot) I would have instead spent that same approximate amount $ on replacing the bushings on the existing control arms, probably with the powerflex which by accounts I've read provide excellent control of play/handling without transferring excessive noise into the passenger compartment. The aftermarket "HD" control arms/bushings are plagued with excessive road noise on certain types of pavement into the front floor area, and also "thumping" noises over sharp bumps/cracks/holes which I relate to the design of these bushings being a slight change from OE and tends to make a little (noticeable) thumpy noise when the inside part of the bushing contacts the outside at speed. The new design powerflex front CA bushes are somewhat pricey so I'm inclined to try a few things on my own before plunging on those. Which might be dramatically less expensive if I can find/figure out something that both works and is durable. I'm thinking of filling the void, but as with the top plate/bearing it needs to have specific qualities and be durable and hold in place/not fall out.

EDIT: and I almost forgot the reason I came on here and started typing. It occurred to me while looking at that front CA bushing and brainstorming - toe error at speed (flare) would result in tension and either pull this bushing in or out, which should be observable with one of those small battery operated IP cameras mounted to observe this bushing while driving. If toe is optimized to compensate for flare at your preferred speed, on smooth/flat pavement these bushings should remain centered. I don't have a small camera to mount under there, but they are cheap enough I just might.

[mrbrian200]

Google search finds some other examples of people attempting to shore up worn OE front CA bushings on these (and other makes with similar style CA bushings) without replacing them with outright. Mine are replaced/new, aftermarket, not worn. Of the various poly based sealants and adhesives readily available I think Loctite PL-S30 might do it (medium tensile, medium-low hardness, elastic properties looks to be more than adequate.

The goal appears to be to let the existing rubber bushings do their thing first 1-2mm with progressive resistance/damping properties beyond that. Beyond simple wheel hop the suspension feels to have a pronounced mechanical resonance that gets set off over bumps/holes that feels to be around 10-15hz, felt only mostly through the steering wheel, not through the chassis. I'm certain it comes from these front CA bushings springing back/fourth like a rubber band 2-3 times until it stabilizes.

http://www.loctiteproducts.com/tds/PL_SEAL_RF_tds.pdf

I'll give it a whirl. Cure time ugh.

[mrbrian200]

I got it. Barking up the wrong tree with the front CA bushing. The problem is the rear CA bushing rubber is *no match* for the forces involved over potholes and/or a good bumpy side road at speed. It would appear that the rubber gives too much (probably more than engineers had intended). The CA/Bushing outer metal sleeve contacts the subframe (noise), this excessive movement is also responsible for the tracking/handling instability. For now, this got rid of the noise and improved handling, cut from the sidewall of a used tire, the shape of a washer with a hole in the middle. A radial slit from the center was made so I could get it in there without removing the control arm (as a test). Ideally the ring would be left closed and installed with a new control arm, possibly with a cushion of softer closed cell poly (like the bump stop material) to fill the gap completely. Excessive movement is probably both up and down you need this on both the top and bottom. In the picture you can see a 'dent' along the edge of the metal bushing sleeve: this is where it was banging against the subframe.

[mrbrian200]

Ok this is what I'm coming up with here. So the OEM CA bushings are less elastic. But this property leads them to tear and fail prematurely (problem noted on CAs I took off the car). Aftermarket CA/Bushings attempt to address this by using "more virgin rubber" etc.. but this alters the characteristics and the bushing becomes more elastic and stretchy resulting in vertical play, poor handling and noise.
Short of a total redesign of the CA or this bushing I'm thinking the line I'm following with this is probably is the only real viable permanent solution- the "stretchy" CA bushing was a step in the right direction as it will be more resilient against tearing with the pivoting motion of normal suspension travel , but they didn't do enough testing to see that vertical extension of the bushing presents an issue under load with (probably) the easiest way to address this being external second bushing between the CA and subframe- that probably should be packaged with the CA.

What confounds me is that I'm new-- I bought the car only a year ago, my first experience with a P2/Volvo. Please tell me I'm not the first one to be figuring this out. Volvo factory engineers? Dealer techs? Aftermarket suppliers? These cars with this front end design have been on the road going on 15-20(?) years now. From what I can tell has been a thorn both to owners and service departments from pretty much day 1.

[mrbrian200]

This is what I came up with. Pic is one for the bottom, goes in snug (without removing the control arm) with petroleum jelly. Ones for top are thicker (not pictured). Improvement in tracking and handling up bumpy/uneven pavement is pretty dramatic. I'm not sure about longevity, I suspect the rubber will last awhile. The question is the closed microcell bump stop material (lighter color). I'm not sure the poly bushes sold here and there are the answer either. What it really needs there is some sort of sealed ball joint surrounded by rubber to the CA or a total redesign of the front control arm and it's mount points to the subframe so that the ball joint sits at a 90 degree angle out from the front bushing which would concentrate the stress of up/down travel onto that pivot point (like you see on virtually all other models (Lexus/Honda/cloud cars etc) that use a similar LCA configuration (front pivot, rear anchor).

[mrbrian200]

Looking at this from an engineering point.
I have two underlying problems. One from Volvo, another courtesy of the aftermarket 'hd' control arm.

Volvo should have used of two pivot joints or changed the CA dimensions. This configuration only works well when the front bushing sits at a right angle to the ball joint/axle with the rear anchor trailing behind at no less than 1x the distance between the front two attachment points. These CAs are closer to an equilateral triangle. As such the rear bushing gets forced vertically (instead of a pivoting motion) stretching the bushing into a conical shape at which point it becomes weak to lateral forces resulting in unstable geometry and premature bush failures.

Then comes the aftermarket 'HD' control arm. Attempting to address issues of longevity and response/handling they closed up the front bush so that its almost solid (the OE front bush is open along the sides). With an equilateral triangle increased stiffness/resistance to pivoting at the front bush results in additional vertical forces at the rear making a problematic OE design even worse. It would be ok to close up the front bushing for better steering response *if* you do NOT bond the center post to the rubber, then somehow address vertical 'float' on the rear of the control arm to restrict motion in the bush to pivot more like a ball joint.

Volvo changed this on the P3s. They corrected the angle to 90 degrees at the front two attachment points, oddly applied a fix to the rear bush that was probably no longer necessary and then placed the anchor bushing up front at the highest stress location? OMG!

[mrbrian200]

Final determination: Front bushing needs to *not* be bonded to the center steel arbor. Tendency of rubber and poly to "squeak" as the arbor turns inside can be resolved. Crew at powerflex already figured this out with their new design. Virtually all other OEs have solved this. However, as the ball joint/axle doesn't sit straight out from the front bush/pivot point the rear of the control arm will still want to float up or down vertically resulting in unstable handling behavior. Putting a stiffer poly bush there may tame things but doesn't really address the core issue. But that can be addressed externally via the inserts I'm coming up with, which need to be thicker on each end (front/rear of car) to control whole vertical movement of rear of the CA while still allowing a pivoting motion with normal suspension travel. A sealed greased spherical bearing back here would work well, but needs to have a rubber or poly surround between it to the CA to dampen noise and vibration. Spherical bearings seem mostly designed for track use (no rubberized or poly surround/all metal).
I really have trouble wrapping my head around the P3 and SPA CA designs. That looks like an untenable problematic nightmare and may well put the brake on ever thinking I may want to own one, despite the exterior styling/interior design teams pretty much batting a grand slam on the new SPAs. From P2 on I get the impression Volvo front suspension engineers have been darting around what amounts to be a tried and true designs adopted by virtually everyone else (because it works): Either LCA ball joint straight out from a front pivot style bush with the rear fixed bush trailing behind, or equilateral A arm with two pivot style joints, or a different style bush up front that would bee less prone to tearing/failure (see BMW).

[mrbrian200]

Pic is of a MY 2011 Subaru Sti OE LCA bush with the dust boot removed to see inside. I repeat: that's Subaru OE equipment, not an aftermarket pillow ball.

Obviously this one would not directly fit a P2 Volvo (the ball would need to be modified with cylindrical extensions to mount to our subframe with a thru-hole bolt).

But the concept is applicable and more in line with what we really need on that rear LCA bush. On the newer Volvos this bush was moved to the front position and I would suspect something like this design Subaru came up with might be desirable on the front position of newer MY Volvos as well.

The inner ball controls LCA movement while the outer rubber bush provides NVR isolation desirable for a daily driver. It would be imperative with this that the front bush be free from resistance to movement (like the powerflex bush where the bushing material, be it poly or rubber isn't bonded to the center bar). Resistance to movement up front results in more upward/downward 'float' force on that rear bush which would stress out the rubber part on this.