E92 M3 ZCP in SCCA Solo F Street

[Datka]

I would highly recommend Dinan front bar with their adjustable end links.
I tested it at WGI and improved my PB by 1.5 sec.
Same car, same set up, Dinan bar was the only part that was changed. Stock bar was replaced.
Just wanted to see what difference would it make with everything else being equal.

[Rassilon]

Originally Posted by CSBM5

Note that it's definitely worth a call to Eibach unless someone here can definitively answer the hollow vs solid question about their front sway bar (and if the rep just reads the published text, you have to press for a definite answer from their design group).

Their front bar is 29mm, and its stiffness would not be high enough if it was hollow to match up with their 25mm rear bar for the M3. It's solid I'm guessing...since I have their rear 25mm bar on my car (what a fun job installing that was) that is advertised as hollow also, and I can guarantee it is solid. I have it matched with the original Dinan solid front bar which is 28.5mm. If I get time later, I may call their support line and force the issue since they need to update their marketing material.

I suspect they are at the more solid end of the hollow compared to the dinan bar. The rates seems similar to dinan, and I am curious the weight of dinan bar vs eibach bar. http://eibach.com/america/en/eibach-...ll-kit-2008-13

[CSBM5]

Originally Posted by edwardgtxy

I suspect they are at the more solid end of the hollow compared to the dinan bar. The rates seems similar to dinan, and I am curious the weight of dinan bar vs eibach bar. http://eibach.com/america/en/eibach-...ll-kit-2008-13

Yeah it definitely is solid or very close to solid as opposed to as hollow as the stock or Dinan bar. If it had a similar ratio of outside to inside diameter as the stock bar, it would weigh about 1.3 times as much, or using their weight data (7.5 * 1.3) = 9.8lbs. They list the weight as 12.1 lbs. Of course this all depends on the wall thickness of the hollow bars, so I assume they could have a very thick wall perhaps and still call it "hollow".

Similarly the rear bar would weigh about 7.0 lbs versus their spec weight of 10.6 lbs. Having handled the rear bar and the stock one at install time, there's no question the rear bar is solid or very close to it. The other assumption here is that density of the spring steel used for each bar is the same, and this should be a very good assumption within a couple of percent or less.

EDIT: Here's a link to the Hotchkis stiffness data. Too bad they don't show the bar weights.

[Rassilon]

Originally Posted by CSBM5

Yeah it definitely is solid or very close to solid as opposed to as hollow as the stock or Dinan bar. If it had a similar ratio of outside to inside diameter as the stock bar, it would weigh about 1.3 times as much, or using their weight data (7.5 * 1.3) = 9.8lbs. They list the weight as 12.1 lbs. Of course this all depends on the wall thickness of the hollow bars, so I assume they could have a very thick wall perhaps and still call it "hollow".

Similarly the rear bar would weigh about 7.0 lbs versus their spec weight of 10.6 lbs. Having handled the rear bar and the stock one at install time, there's no question the rear bar is solid or very close to it. The other assumption here is that density of the spring steel used for each bar is the same, and this should be a very good assumption within a couple of percent or less.

EDIT: Here's a link to the Hotchkis stiffness data. Too bad they don't show the bar weights.

I think the stiffness depends on OD^4 - ID^4. 32mm^4 - 24mm ^4 ~= 29mm^4, assuming everything else is the same, so the eibach one is very likely solid. I wonder why eibach marketed the bar as tubular, as they do distinguish between solid and hollow/tubular in other ones. The Hotchkis set looks really good, I hope they sell the front one separately.

[The Father]

Originally Posted by Richbot

Current Dinan bar is hollow, adjustable, and available as just the front (I just bought one a couple months ago). The old Dinan was not (Chuck has that one)

I'm pretty taken aback that they charged you. just off-putting as heck when they know it's been an issue. That's just a red flag and a half to me.

Oh well, probably my fault because I have lots of posts on this board telling people my "RD Bar is just fine blah blah blah what could possibly go wrong" and then it broke leaving my driveway

Where did you buy your Dinan bar? They've been sold out everywhere since I started looking in February. Dinan had a delivery date of May 25th. However the manufacturer could no longer produce a bar to pass Steve's specs. Steve sent an email saying there is now no eta on stock.

I've called everywhere trying to find old stock sitting on a shelf without success.

Btw, everyone I call says they have them in stock. Then I tell them to look, and they're like doh! No we don't.

I'll probably go with Eibach. I've used their bars for years. Never an issue.

[The Father]

Also, the diameter of a bar and whether its hollow or not will give you very little info on stiffness. The only way to know would be a spring dyno.

It was tested in the RSX world I used to be a part of.

Hollow wasn't necessarily lighter or stiffer/less stiff (this was a big argument prior to testing), and thicker wasn't necessarily stiffer.

You're almost better off trusting the percentage over stock the company claims.

Best bet is to simply ask you guys what works!

[CSBM5]

With known dimensions, and known modulus, you can exactly calculate the stiffness of a torsional spring...exactly as in a closed-form solution, no estimating. Pretty basic stuff that's been proven for well over 100 years....

[Richbot]

Got mine from ECS. But I think they are just a dealer drop shipping from Dinan. So I suspect I must have gotten one of the last ones if they are out of stock now

[CSBM5]

I find it odd that someone claims to have received an email from Steve? He sold Dinan four years ago, and last year came back from Ganassai to CA and bought the two former Dinan repair shop locations and started sdautotech. Although he has a business relationship with his former company, he's not a part of it any longer.

[admranger]

Originally Posted by Richbot

Got mine from ECS. But I think they are just a dealer drop shipping from Dinan. So I suspect I must have gotten one of the last ones if they are out of stock now

Did you sort the end links out? Mine were too long (in my opinion) too. I should be in a position to start working on a car in the new townhouse garage again sometime in August...Just getting the list of things to do started.

[Richbot]

Originally Posted by admranger

Did you sort the end links out? Mine were too long (in my opinion) too. I should be in a position to start working on a car in the new townhouse garage again sometime in August...Just getting the list of things to do started.

I went back to my very old Turner? endlinks. They're quiet and the right length and all is well now

[The Nebulizer]

I'm using the Eibach bar as I had one already (M3 bar) from the 135i I sold. I'm just using stock endlinks. I have it set to full stiff, which by my calculations/understanding is a little stiffer than Dinan at full soft. I'm the last person to ask about how it is working - feels good to me though.

[Maypo]

Originally Posted by Richbot

I'm pretty taken aback that they charged you. just off-putting as heck when they know it's been an issue. That's just a red flag and a half to me.

So was I, since a wrecked car, or worse, could have been the result.

[The Father]

Originally Posted by CSBM5

With known dimensions, and known modulus, you can exactly calculate the stiffness of a torsional spring...exactly as in a closed-form solution, no estimating. Pretty basic stuff that's been proven for well over 100 years....

I would imagine you are correct. I won't take the time to look up what modulus means. The problem with this is not one company or person has done this calculation....ever. Well, maybe they are doing it when they get their 120% as stiff as stock (but I would bet they aren't doing math, but using a dyno...and more likely just throwing out a believable number).

In my gut though, I think its not correct. All the different bends, lengths, other variables, even for the same bar thickness. I can't imagine that would be an easy calculation.

Math is hard.

[The Father]

Originally Posted by CSBM5

I find it odd that someone claims to have received an email from Steve? He sold Dinan four years ago, and last year came back from Ganassai to CA and bought the two former Dinan repair shop locations and started sdautotech. Although he has a business relationship with his former company, he's not a part of it any longer.

You are correct, sir.

I don't know much about Dinan, but the email was very informative and obviously written by someone other than a salesman (or their salesman are just really knowledgable).

I thought the name at the end of the email was Steve (no last name).

It was not. It was Scott.

[SkysTheLimit]

Is EDC delete allowed for ZCP cars?

I might be joining the fun with a "tired" ZCP suspension and am not sure I want to spend the coin on getting a new set. The Bilstein ones look good, but seem to be much heavier than the OE Sachs bodies.

The other option is to pick up a used OE set from the forums, but there doesn't seem to be many ZCP EDC sets. Mostly Non-ZCP EDC.

[Richbot]

You can replace adaptive shocks with non-adaptive units and install a device to tell the computers everything is ok

You can't, IIRC, replace adaptive with different adaptive shocks; which is a little odd but I guess keeps people from going full tilt moron on some of the aftermarket racing adaptives that are out there if you have access to a truckload of $100 bills

[The Nebulizer]

Originally Posted by Richbot

You can replace adaptive shocks with non-adaptive units and install a device to tell the computers everything is ok

You can't, IIRC, replace adaptive with different adaptive shocks; which is a little odd but I guess keeps people from going full tilt moron on some of the aftermarket racing adaptives that are out there if you have access to a truckload of $100 bills

This is out for review in the latest fasttrack.
The proposal is to allow replacement EDC shocks for EDC equipped cars, but you can't change the computer/controller. It has to run off the stock signals.

And, yes, you can run non-EDC on EDC cars currently.

[SkysTheLimit]

Originally Posted by The Nebulizer

This is out for review in the latest fasttrack.
The proposal is to allow replacement EDC shocks for EDC equipped cars, but you can't change the computer/controller. It has to run off the stock signals.

And, yes, you can run non-EDC on EDC cars currently.

Richbot that's what I was hoping to hear.
Also by Bilstein I meant the "OE" style B6 and not B16 setup. I'd love to be able to swap to conventional shocks to reduce cost...don't think I'd be losing anything over a tired set of EDC dampers even with the continuously variable sport mode.

Interesting idea though on the latest Fasttrack proposal. Would only benefit those who care to spend to win...which I am not about in street class.

[CSBM5]

Time to keep this epic thread going with a turn back to tires for a moment. Assume one is using RE-71Rs, 275/35-18 all around; is there any need for more rear grip and/or can setup be changed to take advantage of a wider and larger in diameter tire? I'm thinking of the 305/30-19 out back in this thought stream. Given how wide RE-71Rs seem, would the 305 even fit?

[Type_Yarr]

Originally Posted by CSBM5

Time to keep this epic thread going with a turn back to tires for a moment. Assume one is using RE-71Rs, 275/35-18 all around; is there any need for more rear grip and/or can setup be changed to take advantage of a wider and larger in diameter tire? I'm thinking of the 305/30-19 out back in this thought stream. Given how wide RE-71Rs seem, would the 305 even fit?

I've seen someone run 315/30/18 Rivals on an BS M2. They stuck out of the fenders about a half inch but never rubbed due to enough camber gain. That car really needs more rear rubber to make use of its thrust though.

I run an E92 ZCP in FS on 275/35/18s, and I think it rotates too slowly as is with a stiffer front bar. Any more rear tire and I'd be worried you'd just be wasting it trying to throttle steer it around the tight stuff.

Anyone else run staggered with success?

[CSBM5]

Originally Posted by Type_Yarr

I've seen someone run 315/30/18 Rivals on an BS M2. They stuck out of the fenders about a half inch but never rubbed due to enough camber gain. That car really needs more rear rubber to make use of its thrust though.

I run an E92 ZCP in FS on 275/35/18s, and I think it rotates too slowly as is with a stiffer front bar. Any more rear tire and I'd be worried you'd just be wasting it trying to throttle steer it around the tight stuff.

Anyone else run staggered with success?

That was my thought too. I would think it would be overkill and ruin rotation as you mentioned, but I was curious if anyone thought about such a setup. Outside the box thinking, but something like a stock FSB but an adjustable rear bar and use the 305s out back (or the 315 Rival S').