MS6 Suspension Data & DIY Bilstein Coilovers

[Fstrnyou]

The front diff carrier / tranfercase interaction was discussed some 20 posts ago.

The front diff carrier spins at the same rate as the rear diff...since they are mechanically synced up with the clutch engaged.

Now that you've seen how it all connects, the parts breakdown exploded view should make much more sense with the passenger side intermediate shaft running inside a hollow transfercase shaft.

[Fstrnyou]

Originally Posted by KevinK2 By "diff" you you mean the carrier that the ring gear is attached to, in this case ? If so: For any diff, front or rear, when you turn the outer wheel spins faster than the inside wheel. The outer half shaft spins faster than the inside one. This applies to the side gears in the diff too. The diff can not be at the same speed as either side gear. If the car speed does not change in the turn, I believe the average rpm of the wheels is the diff rpm. Your demo proved the average rpm of the wheels is the diff rpm. A quick google should help out here. .

That is correct.
Simple experiment: Hold one axle still, spin the other axle. The diff will spin 1/2 the rotations, proving 1 wheel can spin faster than the diff and further showing the diff speed is the average speed of both axles.

[phate]

It does spin at the average. Just confusing myself, I said it was the average in the last discussion, and it still is haha.

Still doesn't bode well for the rear diff clutch pack since I can spin a front tire pretty easily.

Got a reply from Shaikh with good info. I should have the dampers sent out this week and decide on a couple minor changes to go with them.

[Fstrnyou]

Is it the rear diff LSD clutch pack or the AWD clutch pack?

[phate]

Originally Posted by Fstrnyou Is it the rear diff LSD clutch pack or the AWD clutch pack?

AWD clutch pack at the pinion is what I'm referring to.

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[KevinK2]

Originally Posted by phate It does spin at the average. Just confusing myself, I said it was the average in the last discussion, and it still is haha. Still doesn't bode well for the rear diff clutch pack since I can spin a front tire pretty easily. ...

I agree, the center coupling's clutch pack could have worn discs, allowing more than expected spin at the inside front tire in a corner. But I'd be surprised if the control module is signaling for max lock at the coupling, during tight corners.

Any thoughts on bench testing the current and replacement couplings?


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[KevinK2]

Originally Posted by phate Steady state cornering, without braking or accel, the car doesn't lift either wheel. It's only when you get into the brakes or gas that they lift. Dive and squat resistance need increased to combat this. I don't want to decrease roll resistance at any point. You'll end up increasing load on the front end by decreasing rear roll resistance, as well as increasing roll in the corner. More roll + more load = unhappy tire. Car needs more dive/squat resistance, or decreased load transfer. Lower the car more to decrease load transfer - that's pretty realistic and easy to accomplish. Increase spring rates to increase dive/squat resistance - as long as the dampers are valved appropriately, I think this is going to happen. ...

By now I think the dampers have been shipped out to get tuned for a lower, stiffer spring set. As you said, this should lower the CG and reduce the rear tire unload during braking when cornering. But just the increase in rates will not reduce unloading due to pitch, only the amount of pitch. It's just like with roll rates, you need to reduce the cg, and/or increase the wheelbase, to reduce weight transfer due to dive.

The rear tire lift could be due to:
1) stiff roll rates
2) lack of droop at the dampers --- I thought the piston rods were shortened.

If there were no rear bar, soft long-travel rear springs with adequate damper drop distance, the inboard rear tire would not lift, but with little rear roll rate the car would have terminal understeer. Your roll rates and their F/R balance work great for you, making it hard to make changes to keep the inside rear tire planted, other than a lower CG.

I had a rwd track car with high front roll rate, and it lifted the front tire ~2" off the track on a 90 mph corner at the limit. It had stock springs and a big front bar that transferred sprung weight faster that the rears bar and springs. There was not much squat due to the modest hp, and limited 4th gear pull.

Hopefully the lower CG will delay or eliminate lift.


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[phate]

Side project:

YouTube Short

YouTube Short

These will be replaced with solid units. Total pain to get them out, but should be worth a little bit. Front subframe is all torn apart, rear to follow the next weekend I'm home.



Ordered new wheels for next season. 10.5" wide will be retired to street tire duty

[KevinK2]

Originally Posted by phate Side project: These will be replaced with solid units. Total pain to get them out, but should be worth a little bit. Front subframe is all torn apart, rear to follow the next weekend I'm home.

Please correct me if I'm wrong, but during a run that bushing never flexes that way, due to the high stiffness of the frame and sub-frame that it connects together.

The oem goal was for minimum NHV (harshness) so like most stock suspension bushings, the bolted joint is isolated with rubber. That allows some vertical give, as well as side to side and front to back give.

The advantage of solid mounts for racing is to eliminate any "give" that may affect suspension positions under loads of braking, accelerating, and cornering. The motion in your video shows the presence of this rubber isolation that allows give, but is not an indication of an actual deformed shape when driving. A new oem bushing would flex in that same way with the same prying loads.


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[phate]

Of course they don't see a torque like that. I was barely applying any force, maybe 20 lbft in that video, and the deformation was what you saw. They are very, very soft, and I'm sure they contribute to camber loss from lateral loads.

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[KevinK2]

Originally Posted by phate Of course they don't see a torque like that. I was barely applying any force, maybe 20 lbft in that video, and the deformation was what you saw. They are very, very soft, and I'm sure they contribute to camber loss from lateral loads.

I never questioned your knowledge of the benefit of solid mounts .... I even asked you to correct me if I was wrong. Simply tried to explain what happens, for those that may not know. Sorry for the confusion.


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[phate]

I have a torsen LSD in the works. Should have it for the start of next season. More details next week.

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[phate]

Originally Posted by phate I have a torsen LSD in the works. Should have it for the start of next season. More details next week.

This project is a go. Deposit paid and the first CAD model is already finished. I spoke with the shop in person with the stock open differential in hand, and they're confident about the project. I'm going to drop off the 3 shafts that mate with the diff (axles and PTO output) this week and that should allow them to better measure the splines for the diff.

12 week delivery time, but I'm hoping that will improve.

There's also some GOOD potential for transfer case strengthening, as the company also has experience in this realm. That's a separate project at this point, and one that can finish later than the diff since I can always swap a tcase in a few hours.



Next year might be more exciting than I thought!

[nindoja]

Originally Posted by phate This project is a go. Deposit paid and the first CAD model is already finished. I spoke with the shop in person with the stock open differential in hand, and they're confident about the project. I'm going to drop off the 3 shafts that mate with the diff (axles and PTO output) this week and that should allow them to better measure the splines for the diff. 12 week delivery time, but I'm hoping that will improve. There's also some GOOD potential for transfer case strengthening, as the company also has experience in this realm. That's a separate project at this point, and one that can finish later than the diff since I can always swap a tcase in a few hours. Next year might be more exciting than I thought!

I know I wasn't in for the LSD just yet, but count me in for a strengthened t-case.

[Tomas]

Please take a closer look at the rear diff on the 6. Even if you have had it in your hand.
The 6 already has a rear LSD. Not an open one.

[KevinK2]

Torsen is for the front.

[Tomas]

Ah.

[phate]

While I have a few big projects going on, I'm taking the downtime to do some smaller maintenance items.

When I pulled the engine, I found the rear main seal to be leaking. I'll clean that up and swap in a new one. Not sure why this one failed, I've done several and this has been the only one to leak. I'm going to pull the pan and reseal the entire seam.

New clutch! The first version of the FX400 that I ran was incredible. Very little pedal travel required and it worked like a champ for 2 seasons. The updated pressure plate required less force, but required nearly every bit of available pedal travel to work. I've never liked the updated version, so I'm swapping over to an ACT 6 puck with prolite flywheel.

Exhaust mani is getting coated by Swain Tech. I just saw they charged my card, so I think I'll have it back soon.

New brake lines. I've had the same braided stainless lines on the car for about 5 years, and the teflon cover isn't looking good in a few spots. I'm just going to swap all 4 corners out for new ones.

Going to a fixed mount driver's seat and getting rid of the adjusters. The sliders are heavy, and we found out that we can have the same seating position and get by. I'm going to raise the seat ~1" from where it is now.



This week I'm going to pull the rear subframe and get measurements for the bushings. I'm planning to do solid aluminum on both the front a rear subframes.


Edit: I'm also prepping the current TCase with upgraded bearing caps and new seals.

[phate]

Exhaust manifold is finished. It's a very coarse, thick finish. Hopefully drops under hood temps a bit to make things easier to work on between runs. I'm planning to have the downpipe reworked before the season begins and I'll have it coated, as well.

Getting wheels has been a pita. I've ordered from 2 places that had them "in stock", only to find out they don't have them. May have to special order them but that puts delivery out to February. That will probably be OK, I can always run the first event on the Bridgestones if needed.

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[phate]

Wheels are in. The 2nd company made things right and found the wheels at a 3rd place. Not the color I wanted, but beggers can't be choosers I suppose. I'm undecided if I'll have them painted or just run them in this obnoxious color scheme.

The next weekend I have free is MLK weekend. Plenty of work to do, now including a test fit of these with the 315/30 (pictured).

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[phate]

Front subframe bushings.

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[aviator79]

I had posted before how there is a ton of adjustment in front subframe. IIRC the bushings are slotted and the subframe holes were slotted? I always worried I would not alight the subframe correctly when reinstalling. Thou now my bolts are seized in the frame so I have not even been able to remove but will need to some day.

Never made sense to me but assume if the eccentric washers for the bolts in FLCA did not fix alignment then the subframe could be moved if both were off the same direction...IDK.

Were the slots in the subframe as well? Either way these should center it and assume thats best so long as subframe is straight.

What were the slots for?

[phate]

Originally Posted by aviator79 I had posted before how there is a ton of adjustment in front subframe. IIRC the bushings are slotted and the subframe holes were slotted? I always worried I would not alight the subframe correctly when reinstalling. Thou now my bolts are seized in the frame so I have not even been able to remove but will need to some day. Never made sense to me but assume if the eccentric washers for the bolts in FLCA did not fix alignment then the subframe could be moved if both were off the same direction...IDK. Were the slots in the subframe as well? Either way these should center it and assume thats best so long as subframe is straight. What were the slots for?

The rear left bushing, in stock form, has a cross-car slot. All others are round. I've left those hole dimensions in the bushings the same so that I could have adjustment in the subframe - I've never had it shift.

I have corrected cross-camber by shifting the subframe slightly. Works great.

[phate]

Busy weekend. First things, first, I armed myself with some necessary equipment.



First item on the list was to get the front subframe bushings in. I double checked all the measurements and new pieces, and in they went.





I did have a little hang up on the rearward bushings. The OD interfered with the curvature of the lateral cross member. Of course, that's the only thing I didn't measure. Minor massaging took care of this.






All done.






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Now that I have the fronts in, I can start on the rears:



I won't go into much detail, here, as it's going to get a devoted thread - bushing removal for 3 of the 8 bushings is not easy.






They're all out, I just need to clean up some dimensions and I'll get them over to the machinist.



While I was in there, I discovered this gem. This is the second time a CPE diff mount bushing has failed, so it will not be going back into the car. Looks to be a huge bubble in the poly:




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Third item was to install billet transfer case bearing caps and reseal the case. Easy job:





Other things in the works to reinforce the cases, as well.



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You might be wondering about the tire in the first picture...

This was my first test fit of the 315/30/18 on an 18x12. For reference, 315 on the left, 285 on the right:



Rear is easy, no problems back there except needing to move the flares up and maybe get bigger ones.





The front...



The front isn't quite so simple, but they're going to fit. I need to trim the rearward portion of the fender just a bit so they don't have any chance of rubbing. I'm well within the rules to cut more. The green line is where I want to cut.



This shows approximately how far inboard I can cut (but don't need to).



That's a project for the next weekend I'm home.

[phate]

Got the new springs tested like I did my last ones. I went with 1100 lb/in for the front and 900 for the rear. That nets me about 30% more stiffness in pitch and about 15% more stiffness in roll compared to last year's 850/700 combo. That also puts me at sprung mass frequencies of ~ 2.5/2.8 Hz, maintaining flat ride.

I'm really pleased with these new springs from blue coils (SSS). The last ones I had (800's that I ran for a short while) were pretty progressive gaining upwards of 200lb/in/in. Here's the plot of those old ones vs the QA1 700's I went back to last season:







And here's both pairs of new springs. These blue coils are gaining less than 25 lb/in/in, so significantly better than the old ones and right on par with Eibachs.





Lots of things to do this weekend to prep for the season. Front diff isn't done yet, that might be as far off as the first week of March.

Bilsteins are finished and scheduled for delivery next Tuesday. More to follow when I wrap up the weekend.

[phate]

Some updates from last weekend:

I replaced the rearward LCA in the front suspension with caster bushings:







I resealed the oil pan and put the new rear main seal on. There were a couple spots on the pan seal that looked like there wasn't adhesion of the RTV. Hopefully that's all good now, it caused a mess. After that, I put the new clutch on (ACT 6 puck with prolite flywheel):






For tire clearance, I've been mostly worried about the weld flange in the back of the wheel well. The caster bushings are a two-fold advantage - they give me more caster (obviously), but that also means they push the wheel assembly forward in the car, allowing for more clearance to that weld seam. I knew 315's fit from the last weekend of work, so I had to try some 335's

At full bump, they look something like this:







Most importantly, I can get plenty of steering angle at full bump to run them. Looks like I'll be going with 335's this year!




During the week, I've received the Bilsteins back:





And got word that the rear subframe bushings are finished:







I ordered a new steering wheel, hub, and quick release to replace the stocker. I'm downsizing to a 32cm OD wheel from the stock 37mm. That should make the car feel a little snappier, and I'm hoping the increased steering force isn't too much (~14%).

I also got word that the front LSD case halves are in finish grinding today and will (should) be assembled and ready next week. Lots of work for next weekend, but the car might be together and running.

[KevinK2]

Originally Posted by phate Some updates from last weekend ... I ordered a new steering wheel, hub, and quick release to replace the stocker. I'm downsizing to a 32cm OD wheel from the stock 37mm. That should make the car feel a little snappier, and I'm hoping the increased steering force isn't too much (~14%). I also got word that the front LSD case halves are in finish grinding today and will (should) be assembled and ready next week. Lots of work for next weekend, but the car might be together and running.

On my old Triumph I autox'd (and won) I also put on a smaller steering wheel and noticed quicker response ( more turn per inch of hand motion ). It had no power steering, but was less than 2000 lbs, and I didn't notice more torque to turn the wheel.

I have a Torsen rear diff on my last big track car, FD Rx7, and it worked great. But I'm sure you know that it is a myth that worm gears are involved, just special helical gears. If you lift a front wheel on a turn, it will act like an open diff. That could be good or bad, don't know.

Good example of a rwd car with torsen and one wheel up:
https://www.youtube.com/watch?v=9r-QPzt9Pvk

BTW your car should be crazy fast with all the changes, and a National contender. Did you reinforce the transaxle case? "Other things in the works to reinforce the cases, as well"


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[phate]

Originally Posted by KevinK2 On my old Triumph I autox'd (and won) I also put on a smaller steering wheel and noticed quicker response ( more turn per inch of hand motion ). It had no power steering, but was less than 2000 lbs, and I didn't notice more torque to turn the wheel. I have a Torsen rear diff on my last big track car, FD Rx7, and it worked great. But I'm sure you know that it is a myth that worm gears are involved, just special helical gears. If you lift a front wheel on a turn, it will act like an open diff. That could be good or bad, don't know. Good example of a rwd car with torsen and one wheel up: https://www.youtube.com/watch?v=9r-QPzt9Pvk BTW your car should be crazy fast with all the changes, and a National contender. Did you reinforce the transaxle case? "Other things in the works to reinforce the cases, as well" .

Lifting a wheel is still my biggest concern - that's why I bumped spring rates this year rather than bars. I think the increased pitch stiffness will help this greatly.

The transfer case, for now, will only have the billet bearing caps. The shop doing the front LSD is the same shop doing the transfer case reinforcements - the front LSD was priority. I can swap a transfer case in much more easily than a differential.

[KevinK2]

Originally Posted by phate Lifting a wheel is still my biggest concern - that's why I bumped spring rates this year rather than bars. I think the increased pitch stiffness will help this greatly....

That would suggest just a concern for rear wheel lift, no?

[phate]

Originally Posted by KevinK2 That would suggest just a concern for rear wheel lift, no?

I'm more concerned about the front than the rear. Powering out of a corner as hard and as soon as possible is my main priority. With the limited slip up front, and a little more pitch stiffness, I think we'll pick up a ton of time being able to power out better.

[phate]

New hub and quick release are in:






As well as the new steering wheel and front diff:



Looks good. I'll crack open the trans this weekend and possibly have things running by Sunday night. Lots of work to do.

[phate]

Starting with post 979, I have a ton of pics in each post.


In post 984, I switched to using google photos. Can anyone actually see the pics from that point, on? They come up on mine just fine.

[kTaLgsTo]

986 and on are dead space...

[phate]

Originally Posted by kTaLgsTo 986 and on are dead space...

Thanks. Photobucket holding pictures hostage has really complicated life...looking for a fix.

[KevinK2]

Originally Posted by kTaLgsTo 986 and on are dead space...

Same here.

[phate]

Originally Posted by KevinK2 Same here.

Yeah, the hot links from Google photos are visible to me, and apparently not anyone else.

Looking for a reasonable fix...

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[phate]

I uploaded pics from 984 and on to the MSF server, so everything should display now.

I can't believe you guys let me get away with that.




I think you have to be logged in to see them - can someone confirm they're working?

[davychronic]

Originally Posted by phate I uploaded pics from 984 and on to the MSF server, so everything should display now. I can't believe you guys let me get away with that. I think you have to be logged in to see them - can someone confirm they're working?

All good now

[kTaLgsTo]

That's a sweet steering wheel

[JohnnyTightlips]

I have been using imgur to host all my car pictures. It works well but if you can use google I am sure that is just as easy.