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[240] Right rear spins turning right, left rear does not spin turning left. Wut?

This probably has way more detail than you want.

https://www.collectionscanada.gc.ca/obj/s4/f2/dsk2/tape17/PQDD_0011/MQ39983.pdf

Its primarily the development of a mathematical model describing a beam axle with panhard rod system. The model also includes spring rates, damping rates and lots of other stuff. The interesting part is around page 48 where the author starts getting into the effect of lateral forces (going around corners) and the load transfers that occurs across the vehicle centerline just because of the panhard geometry.

So the short of it is that the panhard geometry can contribute to a difference in left - right side loading that might make your problem worse. That is not to imply that it is the sole cause of your problem.

Since the vehicle seems to like the left hand turns, perhaps you should switch to stock car racing? From my extremely limited knowledge the stock car dudes treat the panhard rod angle as a desirable component of chassis tuning. If you insist on turning left and right, the geometry lesson in the paper says the longer the panhard rod and the smaller the mounting angle, the less the difference between left and right hand turns. The Watts linkage does seem to be the go to solution for turning right and left at high speed if you have a fair amount of suspension travel (I have never bothered to check the linkage motions to confirm that it really does eliminate the panhard rod problems). If you have limited suspension travel and can get the rod angle small and the rod long enough the panhard rod's undesirable behaviour might not be significant.

I can't remember what the 240 was like; but, on my 140 optimizing the panhard geometry to minimize left - right differences did not seem to be uppermost on Volvo's design file.
 
Yes, thats better. lowers the rear roll center.

Been wanting to release product for a while now that does that.

BTW.. since you have that fancy ass ABS, why not rig up a traction control strategy? If you can get the rear to slightly drag in the inside rear caliper... the truetrac can work.

Honestly, I haven't looked to see if the e-differential stuff can be coded in and whether it will work without the steering angle sensor. It's not a terrible idea, and probably less work than most of the alternatives. 8)
 
Your situation is way too extreme in my opinion to just be the panhard rod mounting. Watching the video of Pobst driving the car makes me cringe, I would be so annoyed!

First question, have you lowered the rear yet or is it still jacked way up? If the ride height is anything like the pictures of the bus on your page that was linked to in another thread I came across, it looks like you need to lower the rear an inch or more! That is and should've been step one a LONG time ago(so maybe you've already addressed it, but this video makes me think not). I would either get scales and corner weight the car, or measure at the pinch seam behind the front wheel wells and in front of the rear wells and make them more even. You can't use the wheel well openings as a judge for the car being level as the rear ones are so much smaller than the fronts. On the General Leif, we have a 51.5/48.5% weight balance front to rear and you should be able to get this even closer to 50/50 considering you're in a wagon.

If the problem still occurs after doing that, I would cut some more off the right front spring to put more weight on the left front and right rear as I assume your corner weights are not near even. Or you can cut some more off the left rear. Or if you don't want to lower the car any more, you can put a spacer in between the upper spring perch and the chassis in the right rear to raise that corner and put more weight on that and the left front wheel. Our cross weight in the General Leif last time it was measured with me in it was 50.7%, so that's 50.7 percent of the vehicle's weight was on the right front and left rear wheels. If that gets closer to 50% of the weight, the car will behave closer to the same in left turns as it does in right turns. It hasn't been enough of a priority for us to dial that in more as there's always something else that's going on and it's been "close enough".

Also, yes, your springs are super soft and not ideal for racing, but if you have the rest of the car balanced out well enough, it should be fine, as it is in shoestring's car(140+rwhp B230F on cut stock springs with nothing special for shocks/struts). I suspect they don't even have roll correction spacers. Do you, shoestring?

Thanks for the data & suggestions. We have tried the welded rear end, loved the traction, did not like the grenade aspect. Looking for someone to make a spool, but probably not going to be cost-effective.
[...]
https://i.imgur.com/9E8FKRwh.jpg
I was going to mention the roll correction stuff up front until I saw this picture. We ran a welded differential in the General Leif for years with no problems having it come apart. I assume it needed more welding?

Yes, thats better. lowers the rear roll center.

Been wanting to release product for a while now that does that.

BTW.. since you have that fancy ass ABS, why not rig up a traction control strategy? If you can get the rear to slightly drag in the inside rear caliper... the truetrac can work.
Get on with making that product, then! You have a perfect tester here to verify the fix, it seems(however, I don't think the panhard rod is the main problem).

Also, getting the ABS to drag this wheel is still just a band-aid for something that shouldn't be nearly as bad as it is, so I would suggest trying the basics of chassis setup before doing something that fancy.
 
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Also, yes, your springs are super soft and not ideal for racing, but if you have the rest of the car balanced out well enough, it should be closer fine, as in shoestring's car(140+rwhp B230F on cut stock springs with nothing special for shocks/struts). I suspect they don't even have roll correction spacers. Do you, shoestring?

Um no.

I think I mentioned earlier in this thread that one or two of my teammates can spin the RH inside tire in extreme circumstances, maybe a handful of times in a 2.5 hr stint. I never do. I am maybe a second a lap slower than them, at most, on tracks that have an average lap of between 1:40-1:50. I cut my teeth roadracing in a '69 Camaro with a 361whp small block, and I always fed it throttle, never used it as a throttle "switch". That habit has carried over into my style in this car. I'm pretty sure that these differentials need to see load before they'll work correctly, and I have to think that's the difference.
 
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Necro'ing this thread; got the car on some scales:

zAmB6B1h.jpg


So, already quite a bit of LF/RR preload. Another good idea shot to hell.
 
We ran a day at Buttonwillow (lots of RH corners) with the front right lowered ~3" more than the left. That made it better, but it gives a wicked initial pull to the right when braking hard.

https://www.youtube.com/watch?v=pfzQ3_o2w-0

Then we ran a day with the front jacked 'way up (about 1" down from full top on Ben's coilovers)... that took it back to bad again.

https://www.youtube.com/watch?v=18w4w2s01RM

Next outing will be ~thanksgiving. Going to try a milder version of the RH front drop to see if that helps any...
 
Necro'ing this thread; got the car on some scales:

zAmB6B1h.jpg


So, already quite a bit of LF/RR preload. Another good idea shot to hell.
I missed this earlier but just had to go find this thread after watching the continued wheelspin and general rear looseness of the fast lap video just posted.

That's a large chunk of weight on the LF/RR already indeed! I can't explain your issues, but I think you should be able to do better than 45% weight on the rear wheels. I would think the wagon would have a lot more weight back there than our 142 that had 49% weight back there previously and 48% currently with our revised fuel cell location being closer to the rear diff.

Have you tried lowering the rear of the car more? Like, an inch? And leaving the front where it is?

So crazy.
 
Necro'ing this thread; got the car on some scales:

zAmB6B1h.jpg


So, already quite a bit of LF/RR preload. Another good idea shot to hell.

Is this with driver/gas? Seems pretty heavy. I think our 245 was almost dead on 2500 lbs with no driver and half a tank of gas. 53% on the front axle and almost 50/50 cross weights. I think the stubby nose of the 140 helps more than having the wagon rear end with regard to weight distribution.

I guess that's a little beside the point though...
 
Is this with driver/gas? Seems pretty heavy. I think our 245 was almost dead on 2500 lbs with no driver and half a tank of gas. 53% on the front axle and almost 50/50 cross weights. I think the stubby nose of the 140 helps more than having the wagon rear end with regard to weight distribution.

I guess that's a little beside the point though...

That is with driver, I am sure. One of the team asked how much we weighed on FB recently before the LDRL Thunderhill race last month.
 
Necro'ing this thread; got the car on some scales:

zAmB6B1h.jpg


So, already quite a bit of LF/RR preload. Another good idea shot to hell.
Do you remember what the ride heights were for this trip to the scale? I really want to know if you have the pinch weld in front of the rear wheels even with or lower than the pinch weld that is just behind the front wheels. If you don't have it level or some slope down to the rear, get some!
 
Do you remember what the ride heights were for this trip to the scale? I really want to know if you have the pinch weld in front of the rear wheels even with or lower than the pinch weld that is just behind the front wheels. If you don't have it level or some slope down to the rear, get some!

Slamming the rear compared to the front will help with the pissing-dog-cornering problem, but not change the weight distribution, by the way.

For comparison, here's my LDRL '91 240 sedan's weights with most of a tank of gas, and no driver:

XBsqEiV.jpg


2489 total, 54/46 front rear, and within 0.5% on the diagonals and L-R. Slightly biased left with a person in the car, but diagonals stay good.

It does the same thing that DrZiplok's car does, but not as bad (though it's hard to tell, as we make less power than their BMW engine).
 
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but I think you should be able to do better than 45% weight on the rear wheels. I would think the wagon would have a lot more weight back there than our 142 that had 49% weight back there previously and 48% currently with our revised fuel cell location being closer to the rear diff.

Remember that they're running a BMW M52 up front. Total ~200lb heavier than my B230 sedan, with the same F/R distribution.
 
Slamming the rear compared to the front will help with the pissing-dog-cornering problem, but not change the weight distribution, by the way.

For comparison, here's my LDRL '91 240 sedan's weights with most of a tank of gas, and no driver:

https://imgur.com/XBsqEiV.jpg

2489 total, 54/46 front rear, and within 0.5% on the diagonals and L-R. Slightly biased left with a person in the car, but diagonals stay good.

It does the same thing that DrZiplok's car does, but not as bad (though it's hard to tell, as we make less power than their BMW engine).
Yes, but I still really, really, want to know because I don't remember getting an answer and it is the easiest thing to try.

Remember that they're running a BMW M52 up front. Total ~200lb heavier than my B230 sedan, with the same F/R distribution.
I didn't know if their engine was all aluminum or not. Their weights I am sure are with a driver. The weights without a driver don't matter too much as it isn't what's being represented on the track.
 
Necro'ing my old thread, but the answer we've reached is a Gripper and a 60" wing off an old Radical. No more RR wheelspin.

Our engine's the regular cast M52. Nothing special there. Rake is essentially zero (pinch welds level with the ground, given that neither the welds nor my shop floor are particularly "straight").
 
Necro'ing my old thread, but the answer we've reached is a Gripper and a 60" wing off an old Radical. No more RR wheelspin.

Our engine's the regular cast M52. Nothing special there. Rake is essentially zero (pinch welds level with the ground, given that neither the welds nor my shop floor are particularly "straight").

What ramps and preload did you go with for the Gripper, more curious than anything :)
 
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