What do you think of running no rear Sway Bar?

[cyrus]

What do you think of running no rear Sway Bar? I was reading

 

http://alteredz.com/suspensionmods.htm

 

I have heard others do it to. Can I just increase the rear spring rate and omit the bar?

[JMortensen]

Yes. Question is how much sway can you tolerate, and how much spring rate can you tolerate?

[datsunlover]

That link doesn't work for me, but FWIW, I run without the rear bar and like it in my 75 280z. For a short time I had a 240z rear bar on and before it caused problems, it worked.. but I didn't like it.. The rear would get 'hard' and want to step out if I got on the throttle a lot out of a turn.. more wheel spin from a standing launch too.. didn't 'squat' very well..

[2126]

From all that I've read on this subject, I'm thinking about removing my rear bar as well to see how it works. Currently, I have 8" x 275 lbs springs in the rear, 10" x 200 lbs springs up front, 25mm bar up front, and 19mm rear bar. Since I installed the LSD, the rear wants to step out a bit easier but corner exit speed has certainly improved. Any comments?

[JMortensen]

2126, I see your rear spring rate as being a little high vs the front rate, you might also try a little toe in in the back and see how you like it then. A little toe in back there makes a BIG difference. You could remove the rear bar but I think it's going to plow really bad afterwards.

[2126]

2126, I see your rear spring rate as being a little high vs the front rate, you might also try a little toe in in the back and see how you like it then. A little toe in back there makes a BIG difference. You could remove the rear bar but I think it's going to plow really bad afterwards.

 

Thanks for the input. As my Z is currently set-up, it seems to be pretty neutral though corners of more than 25 mph. Mind you, This is still a street car with Yokohama ES100s (215-40 x 17 front & 235-40 x 17 rear) Also, my rear LCAs are stock. I'm also about 80% done with doing the front LCA pivot relocation and fully adjustable LCAs and TC rod. Maybe adjustable rear LCAs are in the future. With the 275 lbs rear spring, do you really think it will cause the front end to understeer a considerable amount? I guess the answer lies in experimentation...just like evryone else has to do. John C., any input on this issue?

[260DET]

Answer depends on a lot of things, particularly body stiffness, amount of power and spring rates. But the consensus among my lot seems to be that a light rear bar is the best, no rear bar is too extreme.

 

A light bar is anything from 12 to 18mm, depending on the variables mentioned above.

[260DET]

2126, I see your rear spring rate as being a little high vs the front rate, you might also try a little toe in in the back and see how you like it then. A little toe in back there makes a BIG difference.........

 

Care to elaborate on that Jon?

[JMortensen]

Sure, I've been running 3/16" total toe in in the back for years now. I used to work for a shop where I had access to an alignment machine, and I tried everything from 0 toe to 3/8" total toe. 3/16" total works best for me. Some will tell you that you are "dragging the tires" at 3/16", but lap time to lap time it is the fastest for me. Makes the car more stable under braking and makes it slide very consistently.

 

As to the spring rates, I run 200/250 and I had some MASSIVE plow until I dialed in a whole bunch of negative camber and positive caster. I don't think 200/275 is going to make up for the lack of a rear bar.

[Drax240z]

Jon, what size bars are you using with 200/250?

[JMortensen]

I was running 1" front and 7/8" rear MSA bars. I am now installing a ST 3/4" rear mounted bar, because the MSA was binding on the frame rail.

[johnc]

Sure, I've been running 3/16" total toe in in the back for years now.

 

Were you breaking any stub axles with that much rear toe in? I know others who have tried numbers like that in ITS cars and they noticed more cracking around the flange and had to shorten the replacement interval.

 

On topic...

 

Chet Whittle was very successful running without a rear anti-roll bar on many tracks back east. He did run springs up in the 350 lb. in. range (and higher on some tracks). Generally, the more spring you run the smaller your anti-roll bars need to be.

 

For a street 240Z no rear bar is fine. It basically puts the balance back to factory stock and reduces the tendency for the rear to step out in a corner under drop throttle or braking.

[JMortensen]

Were you breaking any stub axles with that much rear toe in? I know others who have tried numbers like that in ITS cars and they noticed more cracking around the flange and had to shorten the replacement interval.

 

On topic...

 

Chet Whittle was very successful running without a rear anti-roll bar on many tracks back east. He did run springs up in the 350 lb. in. range (and higher on some tracks). Generally' date=' the more spring you run the smaller your anti-roll bars need to be.

 

For a street 240Z no rear bar is fine. It basically puts the balance back to factory stock and reduces the tendency for the rear to step out in a corner under drop throttle or braking.[/quote']

Running a stock front bar would put the balance back to stock. Running a 1" bar with no rear isn't going to restore the balance back to stock. It's going to make it worse than stock.

 

I have never broken a stub axle in 4 seasons of autoxing on 10" slicks, maybe 20 track days mostly on slicks, 2 seasons autox on DOTs, and 2 seasons on sticky street tires. None of the 510 guys I used to run with ever broke a stub, and they all ran at least as much toe as I did, on DOTs and slicks also (240 and 510 stubs are the same).

 

2126, I had an idea. You could just pull one end link and see how it feels. I wouldn't think that leaving the bar in with the other endlink attached would cause any problems. Then you'd know for sure.

[2126]

I just love sucking up this sort of info, that you guys have gained from experiences on the track...certainly reduces my learning curve! Thanks so much for sharing. I quess its just time to experiment with the rear bar. Maybe my set-up is actually not too bad, because my only concern is coming out of slow tight corners and un-weighting the inside rear wheel too much. I just don't want to have a stub axle failure and or overwork the LSD. Time will tell.

[tube80z]

If you're looking to put power down better than a smaller rear bar will be a better option. If you know all the data about your car you can determine how much roll resistance each axle pair has in total and you can use this to switch between spring and bar.

 

One trick I've used that I think works quite well is the use of droop limiters. I started doing this to use less limited slip and trying to improve turn-in. What I found is that it also helps to put the power down. This isn't something you run on the street but can be quickly added (cables and turnbuckles) when you race.

 

I use an 1/8 to 1/4 inch of droop in front and around 1.5 inches in the rear. This helps to keep the limited travel in the suspension being used for what we wanted, not overall body movement.

 

It's a path to explore at least. You may find it doesn't work at all but you won't be out much trying.

 

Cary

[260DET]

As far as going back to stock by doing away with the rear bar goes, don't forget that in many/most markets outside the US S30's had rear bars, stock

 

My understanding is that the US cars had no rear bars so as to give a softer ride, nothing to do with the rear stepping out.

[katman]

"Chet Whittle [sIC- Wittel] was very successful running without a rear anti-roll bar on many tracks back east. He did run springs up in the 350 lb. in. range (and higher on some tracks). Generally, the more spring you run the smaller your anti-roll bars need to be."

 

JohnC recalls correctly. In the southeast we were blessed with several new tracks (Kershaw, VIR, Barber) and several repavings (Road Atlanta, Roebling Road, Charlotte). On smooth tracks I always preferred big spring to big bars to maintain compliance with the inside tires. We almost never had a rear bar on and in fact our front bar, a custom 4130 hollow, was only about the equivalent of a 15/16ths solid. In our case, spring rates in the 350F/285R and 400F/350R worked best to get the power down. I dare say our suspension package (shocks, springs, bar, alignments, "tweaks") was "HOOKED UP" like no other, as back-to-back ARRC victories attest.

 

BIG CAVEAT: Over the years I've come to the conclusion that front to rear spring rate balance you need is very sensitive to roll center (function of ride height- more sensitive the lower you go, not too sensitive at streetable ride heights) and how many low speed corners your track has. At Mid Ohio for instance, a 240Z wants a lot more rear spring than we run at RA. You end up with asomething more along the lines of the "west coast" setup- 250F/300R or something like that- opposite in balance and softer than what we run on the higher speed tracks. And then there's this: On street cars that we've also done driver's schools or other track events with, we've had extremely fun setups with 115F/145R and a standard combo of bars (say 1"F, 3/4R, mounted in poly), and also a 185F/185R and solid mounted bars 7/8F, 5/8R. Same drivers as with the ITS car, same amount of balance and fun. Bottom line, YMMV.

 

Regarding 3/16 toe in the back, I'm afraid I'm from the "low drag" school. I always preferred to find other ways to make the car handle without pointing the tires somewhere other than straight. With our "east coast" setup on the ITS car we did need to run about 1/8 toe out in the front to help turn in on slow corners like 7 at Road Atlanta, but could always make zero rear toe work everywhere (on a street car that retains some rubber in the rear you still want a smidgeon of toe in to control trailing throttle oversteer). And as far as droop limiters- anything that's non-linear in a race suspension can't be good. Y'all are scaring me...

 

Hope that helps.

[260DET]

Not having the faintest idea of your class, katmen, the cars you were talking about had well tied in roll cages? Stiffer body than stock allows the use of 300lb and more springs?

[katman]

The race cars were ITS or EProd. In ITS you can't cage forward of the firewall but you can have a strut bar (as long as it only attaches at the shock towers, no triangulation). Not really any difference in the rates we ran with the shock towers tied in to the cage on the EP car verus not as on the ITS cars, but I will say between 350 and 400 hard to see any difference on the ITS car proly due to the flexibility of the unmodified chassis. IMHO what gets you in a non caged car isn't a 300#/in spring, it's the shock loads necessary to control it (not to mention the shock $$$). We never found any added fun over the aforementioned 185 lb/in springs on a street car, and have had gobs of fun (and I'm talking about rolling out of the seat LMFAO type fun) on the track in cars that were in the 115-145 range. This with drivers used to the race cars.

 

Now if you want to discuss my humble theories on spring rate as a function of driver experience....

[johnc]

Now this was fun! Even though it was just an autocross we could get the 810 in some amazing lurid slides on its 185/70-14 Michelins, with 4 people in the car laughing and banging their helmets together like billiard balls.