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Old 03-14-2019, 01:30 AM   #26
mck1117
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Originally Posted by DrZiplok View Post
Any theory needs to account for how this *only* affects the RR.
This is a thing that Panhard bars do. Your options are:
  1. Move the right side of the panhard bar downward.
  2. Switch to something symmetrical instead of a Panhard bar like a Watts link, Mumford, IRS, etc.

The lateral-g link above explains this pretty well, in the middle of this post (heading "If the car is working the rear tires different in RH corners versus LH corners"): http://lateral-g.net/forums/showpost...68&postcount=6
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Old 03-14-2019, 01:49 AM   #27
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And a drawing:



This is an extreme case for sake of explanation, but it illustrates the point. If you lower the car so far that the panhard bar points straight at the left hand contact patch, a right hand corner will pull on the panhard straight toward the left contact patch. If that force vector is pointed at the left tire, the right tire is doing diddly squat.

A more level panhard (right side down) allows the right spring to keep the right tire on the ground.

Edit: and in left hand turns, the force vector points high and to the right, so both tires get loaded more evenly.
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Old 03-16-2019, 01:20 PM   #28
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Originally Posted by NotSoFresh View Post
Incorrect spring weights and damper valving can cause odd weight transfer behavior, possibly loading and unloading the rear tires.
Per my note above, this doesn't account for the left vs. right difference.

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Id also check that the rear swaybar is not bent. If it is twisted, it will lift one side and load the other.
That's easy to check, because it's sitting on the shelf. No rear sway on this car.
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Old 03-16-2019, 01:25 PM   #29
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Originally Posted by mck1117 View Post
The lateral-g link above explains this pretty well, in the middle of this post (heading "If the car is working the rear tires different in RH corners versus LH corners"): http://lateral-g.net/forums/showpost...68&postcount=6
Yes, sorry, did not mean to address your comments / references with mine; just wanted to encourage folks offering ideas about front spring / damping to think about how to square those suggestions with the very asymmetrical behaviour we observe.

As an aside, I just (re) discovered Vsusp courtesy of the Retropower series about Gordon Murray's Mk1 Escort, and was sad to see it still doesn't have any support for solid axles. 8(
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Old 03-16-2019, 06:40 PM   #30
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Originally Posted by DrZiplok View Post
just wanted to encourage folks offering ideas about front spring / damping to think about how to square those suggestions with the very asymmetrical behaviour we observe.
Me too, as I've also observed my rear-slammed-240 to pick up the right rear when in hard right hand corners. Which I observed at an autocross after installing some suspension before I prove out the suspension...at a Lucky Dog race. See you there!
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Old 03-17-2019, 04:32 AM   #31
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Originally Posted by DrZiplok View Post
Yes, sorry, did not mean to address your comments / references with mine; just wanted to encourage folks offering ideas about front spring / damping to think about how to square those suggestions with the very asymmetrical behaviour we observe.
Is this not just the standard behaviour of a car with a solid rear axle due to the torque reaction through the engine/propshaft?
The standard way of dealing with that (for drag racing at least) is to add some pressure to the right rear tyre by raising the ride height slightly on that side. I'm not sure how appropriate to circuit use that is, but have you tried it?
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Old 03-17-2019, 04:44 AM   #32
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Is this not just the standard behaviour of a car with a solid rear axle due to the torque reaction through the engine/propshaft?
The standard way of dealing with that (for drag racing at least) is to add some pressure to the right rear tyre by raising the ride height slightly on that side. I'm not sure how appropriate to circuit use that is, but have you tried it?
Remember, for there to be torque applied to the driveshaft, there has to be grip. If the right rear wheel is spinning, there can't be any meaningful amount of torque being applied to the driveshaft.
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Old 03-19-2019, 09:32 AM   #33
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My kid and I were talking about this last night and wondering if the driver's weight and location were being taken into consideration. I wonder what swapping the mount points left to right would do? That is to say, axle mount on the driver's side and body mount on the passenger's. If the car then had the tendency to spin the LH tire, you'd have ~200lbs on that side to help counteract it. That's probably 7-8% of the car's weight.
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Old 03-19-2019, 11:21 AM   #34
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Watts:

Another grpA 242 rear axle (full droop, hence not parallel w/axle/ground):

From here: http://240grupp-a.se/sa-byggdes-en-grupp-a-volvo/
Is that an oil pump for the rear axle?
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Old 03-19-2019, 11:45 AM   #35
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Is that an oil pump for the rear axle?
Yep, they run an oil cooler as well. There was probably a transmission cooler and pump setup as well.
Very common in road racing as the diff oil gets so hot.
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Old 03-19-2019, 12:08 PM   #36
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Neat
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Old 03-19-2019, 12:36 PM   #37
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Common in road / endurance racing with a clutch diff for sure. I've heard of some BMW lemons teams running diff coolers. All sorts of systems, from added fins to the diff cover to actual pumps & oil coolers like that one.
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Old 03-23-2019, 02:10 AM   #38
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Common in road / endurance racing with a clutch diff for sure. I've heard of some BMW lemons teams running diff coolers. All sorts of systems, from added fins to the diff cover to actual pumps & oil coolers like that one.
We have been considering this as well, but wanted to put a sensor in first to be sure it was worth it. The rear end (with the TruTrac in it) does run "very hot" but we have no real way to quantify it. We ran the last race with Swepco 210 in it, haven't taken a sample to see how it held up...

Quote:
Originally Posted by shoestring View Post
My kid and I were talking about this last night and wondering if the driver's weight and location were being taken into consideration. I wonder what swapping the mount points left to right would do? That is to say, axle mount on the driver's side and body mount on the passenger's. If the car then had the tendency to spin the LH tire, you'd have ~200lbs on that side to help counteract it. That's probably 7-8% of the car's weight.
BMW kind of took this into account when they slanted our motor over; the bulk of the mass of the block and head are to the right of the vehicle centreline. Closer to the centre, but closer to the front. Battery is also in the passenger footwell for the same reason (well, that and it's the only sensible place to put it).
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Old 03-23-2019, 02:12 AM   #39
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Originally Posted by CAPT_BLOTTO View Post
Is that an oil pump for the rear axle?
Yup, diff cooler pump on the left, transmission cooler pump on the right.
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Old 04-23-2019, 04:42 PM   #40
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Let's see how this works out...

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Old 04-23-2019, 04:45 PM   #41
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Quick and dirty, I like it.
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Old 04-23-2019, 06:55 PM   #42
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I also like it!!!

It should make a big difference.
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Old 04-23-2019, 09:57 PM   #43
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Quote:
Originally Posted by DrZiplok View Post
Let's see how this works out...

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Originally Posted by blkaplan View Post
I also like it!!!

It should make a big difference.
I look at this and my mind goes to how to make it bolt on.
If you clamped the panhard mount around the axle tube on either side of the torque arm mount and located it using the torque arm bolt, I think it could work. It still would require cutting off old mount of course.
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Old 04-24-2019, 12:42 PM   #44
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Originally Posted by NotSoFresh View Post
I look at this and my mind goes to how to make it bolt on.
If you clamped the panhard mount around the axle tube on either side of the torque arm mount and located it using the torque arm bolt, I think it could work. It still would require cutting off old mount of course.
The way i wanted to do it was something that uses the torque rod mounting holes and also the stock panhard stud to anchor it and hung down from there. Would be tricky to get all the measurements correct with how the factory brackets are made but it could be done
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Old 04-24-2019, 01:27 PM   #45
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I'm I correct in assuming I can apply most of this knowledge to my 122S as well?
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Old 04-24-2019, 03:05 PM   #46
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I'm I correct in assuming I can apply most of this knowledge to my 122S as well?
Yes, any lowered car with a solid axle and panhard bar follows the same "laws"
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Old 05-15-2019, 03:07 AM   #47
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Cool thread. I havenít experienced this too much in the General Leif, but definitely have in my 240. Iíll be following along.

Mck1117 are you the guy I met at the Ridge a couple weekends ago volunteering?

Iíd like to see this video with Pobst and this 245, too. Link?
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Old 05-15-2019, 11:37 AM   #48
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Iíd like to see this video with Pobst and this 245, too. Link?
Weird; the post seems to have vanished. I know I didn't delete it. Anyway, enjoy:

https://www.youtube.com/watch?v=SvF7IwiQQ2Q
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Old 05-21-2019, 11:37 AM   #49
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Originally Posted by DrZiplok View Post
Weird; the post seems to have vanished. I know I didn't delete it. Anyway, enjoy:

https://www.youtube.com/watch?v=SvF7IwiQQ2Q
That's insane. I'll continue on the other thread where this conversation started.
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Old 05-28-2019, 02:56 AM   #50
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Just a brief update; the relocation seems to have helped somewhat, but still hasn't fully cured the issue (or made it symmetrical).

We did notice a bit more rear-end looseness (as implied), though some poor tire decisions left us running the whole weekend on less than fresh rubber which made comparison more difficult.

Enjoy the last lap of the weekend, with Racer Simon almost, but not quite, passing the Chotus: https://www.youtube.com/watch?v=43bE...ature=youtu.be
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