At wit's end with lack of inside rear traction...

[Bluemustang]

Not yet but I think I'm going to do those before the LCAs. It's important to me to install one mod at a time so I can evaluate the good/bad and decide if the mod stays or not.

So, my next mods will be in this order:

1. Diff bushing inserts, then
2. FR toe bearings, then
3. LCA bearings




Oh yes, totally, not to mention the LCA bouncing fore/aft as the wheel fights for traction. I've also got high hopes for the diff bushings.

Note taken on the poly links although my car will never see a drag launch if that's worth anything. That said, once the diff/toe/lca parts are in I will remove the links to see if anything is lost, since, they seem to provide only a marginal benefit at this point.

You might notice a good difference with FR toe bearings. I do not have the diff bushings or the LCA bearings as you know. I tried several takeoffs like you described - the car just drifts and then hooks up and corrects. No tire shake or wheel hop. Much better than stock. I think there is a good reason Ford put it in their track kit.

The poor traction in the rain has always been there in my car but no wheel hop cornering.

Still, I am willing to bet I could improve it significantly with 1. Better tires and 2. LCA bearings and then 3. The diff bushings. I will be doing this most likely in the spring once I've saved up enough cash.

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[Rebellion]

The banging and clunking in those scenarios are the diff, half shafts and driveshaft going absolutely bananas.

Interested to see how well those links hold up. My customers have not had much luck with the Poly lasting very long on the links.

[MENTION=9985]BMR Tech[/MENTION]

Curious to know if the ones that failed are due to track duty or just "normal" spirited driving. Is this the actually bushing part that fails, or the structural part of the links?

 

[EricSMG]

You might notice a good difference with FR toe bearings. I do not have the diff bushings or the LCA bearings as you know. I tried several takeoffs like you described - the car just drifts and then hooks up and corrects. No tire shake or wheel hop. Much better than stock. I think there is a good reason Ford put it in their track kit.

The poor traction in the rain has always been there in my car but no wheel hop cornering.

Still, I am willing to bet I could improve it significantly with 1. Better tires and 2. LCA bearings and then 3. The diff bushings. I will be doing this most likely in the spring once I've saved up enough cash.

Better tires, like a MPSS, would help immensely in the wet. But the 'system' is still flawed and my quest is to resolve this.

I will be tackling the diff bushings tomorrow, stay tuned for an update!

Edit - I also have Steeda's LCA bearings on my workbench. Impressively heavy duty little SOBs. I'm devising a pusher/puller assembly out of various pullers I have, tackling that another day - gonna have to get creative.

 

[BmacIL]

Better tires, like a MPSS, would help immensely in the wet. But the 'system' is still flawed and my quest is to resolve this.

I will be tackling the diff bushings tomorrow, stay tuned for an update!

Edit - I also have Steeda's LCA bearings on my workbench. Impressively heavy duty little SOBs. I'm devising a pusher/puller assembly out of various pullers I have, tackling that another day - gonna have to get creative.

Hopefully you don't hate the driveline whine with the bushings. Keep one thing in mind: the tire chatter is going to mostly come from inconsistencies in the control members it's directly connected to (all the rubber bushings in the suspension). The wheels and diff are connected by halfshafts that allow for a good deal of relative movement before any sort of binding would occur.

 

[EricSMG]

Hopefully you don't hate the driveline whine with the bushings. Keep one thing in mind: the tire chatter is going to mostly come from inconsistencies in the control members it's directly connected to (all the rubber bushings in the suspension). The wheels and diff are connected by halfshafts that allow for a good deal of relative movement before any sort of binding would occur.

Good input. Regarding wine - this is why I went with Steeda so I could install the softest (red, 80A durometer) bushings available. My approach with suspension and driveline mods is to always take the more conservative option. The new BMR kit looks killer but it also uses very stiff poly.

Also - while I do expect the diff bushings to help with wheel hop to some degree, probably minimally, I'm installing them primarily to remove the rubbery rock'n roll feel of the driveline.

 

[Brazenbuck]

You're going to get driveline whine regardless.

 

[Norm Peterson]

Installed Boomba vertical links (poly at both ends) today and noticed a positive difference in various aspects. First, the inside rear wheel hop is calmer - the wheel still spins faster than the outer wheel but the slip/grip/slip action is smoother and more consistent and the car accelerates easier. Now - it is pretty warm today so there's that variable but so far I'm pleased.

The links also seemed to have calmed down the "jiggle" in the rear suspension over bumps, providing a quicker settle-down and overall less nervous driving experience.

What may gave happened was that the aftermarket vertical links made the SVIC locations and anti-squats (think instantaneous wheel loadings) more stable.

OE bushing compliances are typically great enough to allow slight/small geometry changes from static under actual operating conditions. That lets the SVIC's wander around a bit, and anti-squat then varies as a result.

Be careful about stiff bushings (any poly is stiff) in joints that need to permit rotation about axes different from the ones straight along the attaching bolt centers. It is possible to DIY a couple of "voided bushing" approaches to minimize the forces that are induced by off-axis rotation (commonly aka "binding"), once you know the directions that the bushing needs to be more flexible in.


Norm

 

[Bluemustang]

Better tires, like a MPSS, would help immensely in the wet. But the 'system' is still flawed and my quest is to resolve this.

I will be tackling the diff bushings tomorrow, stay tuned for an update!

Edit - I also have Steeda's LCA bearings on my workbench. Impressively heavy duty little SOBs. I'm devising a pusher/puller assembly out of various pullers I have, tackling that another day - gonna have to get creative.

I like that you are taking a somewhat scientific approach to this and I think we will all learn something from this. I think you are correct - the system is flawed, based on the situation you've described and other situations which can lead to unpredictable handing and characteristics that don't flatter a sports car. I did my mods mostly all at once so it hard to describe what each part does on it's own. But I did that for cost reasons more than anything else.

I am at a point now where I need new tires because the IRS mods I have done are making the rear more connected to the ground and so traction above all else is key. However, the LCA bearings and the diff bushings are probably the final pieces. I've experienced significant NVH increases given the springs and shocks and everything else being stiffer. But I've learned that this can be controlled to a certain degree by how I drive. For example, knowing when to let the car coast, rather than braking or on the throttle can help the car handle bumps and imperfections with less harshness. But it only goes so far and that's the price to pay in order to feel more connected to the road. Especially with the shocks, the weight transfer reacts right now and so as I become more accustomed to it I can feel what the car is doing.

What's cool now though is I can step away with much less or no wheel chatter and when I push it too far,the nannies reign the car in without being obtrusive. Right now I am enjoying turning traction control off and leaving advancetrac on. It allows the car the drift a bit without getting out of control.

I look forward to your updates and take it one step at a time. I'm confident you'll get it.

 

[EricSMG]

Okay - I made two changes today. Ideally I'd only make one change but in this case, due to how much work was involved, it had to be.

Changes:

- Steeda red diff inserts
- Removed BMR Lockout Kit

It's been raining all day so again, hard to really get a feel for how these mods affect the inside wheel hop, but, other very obvious affects are evident already.

1. The driveline is much more responsive, much less rubbery. I'd say 50% more. Keep in mind that I added stiffness via the diff inserts but removed stiffness via the lockout kit, so the 'net' result is about 50% less driveline 'rock' on/off the throttle than before the changes. It feels good now - like you'd expect a sports car to feel. Even the clutch grab point is much more obvious as the link between motor and rear wheels is more direct, but not too much like a racecar. Further, I'm shocked to report virtually zero increase in additional wine or driveline noise inside the cabin. Windows up, radio off - the same as before - and I'm extremely sensitive to even the slightest increase in NVH. I might say there's a barely detectible ultra soft wine on decal but boy do I have to really strain to hear it, and, I can't be certain it wasn't there before.

2. I'd noted an immediate increase in NVH when I installed the lockout kit and wanted to remove it to 'see' what the car was like stock, again. Wow. What a difference, for the better. Car is much quieter inside the cabin and considerably smoother riding over harsh impacts. Will I notice the reduction is stability once the roads are dry and I push the car? Surely - at that point I'll be able to truly report the 'net' change but I'm almost certain I won't be reinstalling that mod again due to the decrease in comfort that comes with it. Now - this is not a bash against the lockout kit at all - it works as described and works extremely well. For the money it can't be beat, but it is a hardcore part and isn't for me.

Net/net - while the install of the diff inserts was a total and complete bitch on jackstands, today was a very good day for me and this car as the two changes, together, gave me back a bunch of comfort AND an increase in precision that I'm used too. Awesome! I will report back after I've had a chance the flog this thing in the dry as-is.

 

[EricSMG]

Very cool today in San Diego (~50 degrees) so of course the Pzeros are useless but it was dry at least.

Inside wheel hop? Virtually unchanged from bone stock. I'm still unable to apply even 1/4 throttle without inside rear wheel spin which then immediately turns to a sloppy hopping mess with very little forward push. Unbelievably ridiculous for this kind of car.

Summary thus far: the diff bushings, links and lockout kit all have an inconsequential effect on this problem - none are even partial solutions.

I'm really hoping the LCA bearings are the silver bullet here without adding a bunch of harshness.

Edit - the little voice in my head keeps telling me this will not be truly solved without ditching the Torsen. Hope I'm wrong.

However - the car, as it sits now (Steeda red diff inserts and Boomba vertical links, otherwise bone stock) has never felt better. The driveline response to throttle and clutch inputs is crisp and feels properly 'calibrated' if that makes sense. The car is MUCH more fun to briskly whip through the gears, in town, partial throttle. I don't have to focus on perfect clutch timing anymore and can just drive the car. Further, the improved comfort from removing the lockout kit is remarkable and so far, I really can't say I notice the loss in precision. Sure, the car doesn't feel as 'on rails' as before but not in a bad way. There's a natural amount of 'give' to sharp edges and quick lateral transitions rather than the instantaneous chassis acceleration provided by the lockout kit.

 

[Brazenbuck]

I'm still unable to apply even 1/4 throttle without inside rear wheel spin which then immediately turns to a sloppy hopping mess with very little forward push. Unbelievably ridiculous for this kind of car.

So are you saying your car would just do donuts in this scenario?

 

[EricSMG]

So are you saying your car would just do donuts in this scenario?

Exactly not that. I would kill for that - what you get with a really good LSD and proper wheel control. Both wheels grip or spin together, as a unit. When they spin, you get a nice controlled power overseer.

Not happening with this car from a stop while turning - the inside wheel just skips and hops and jumps all around like it's trying to do all the work while the outside wheel is simply along for the ride. My educated guess at this point is that it's a combo of:

1. Very poor fore/aft wheel control due to way too soft front LCA bushings, plus
2. Shitty tires, plus
3. The Torsen's natural requirement for resistance to be present in order to transfer torque to the other wheel

When you put all of these together you get a grip/slip/grip/slip (aka: wheel hop) event at the inside rear wheel when trying to put power down while turning at slower speeds. The outside wheel doesn't make a peep. The system is totally out of balance.

 

[Norm Peterson]

Does it do this on neutral or trailing throttle? Or is it only when you're giving it some throttle?


Norm

 

[BmacIL]

Eric, I'm honestly starting to wonder if you've got something wrong with your torsen.

 

[Competition Orange]

Eric, I'm honestly starting to wonder if you've got something wrong between your ears.

I agree.

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