Making an E30 (Really) Handle

Springs and shocks. What keeps your car tight around corners?
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Making an E30 (Really) Handle

Postby blasphemy101 » Wed Jan 13, 2016 4:05 pm

I'd like to start a discussion about making an E30 handle as well as possible. To start, we'll have to define "handling" - is it responsiveness to driver input, overall lateral grip, lowest lap times, or something else? We'll also have to have some constraints on the car itself. From there, we can then move to a discussion of each system on the car and how it affects handling as we've defined it.

For constraints, I suggest stock suspension mounting points and fenders must be retained, with the motor output set at 145whp/145wft-lb. This should cover 99.9% of E30s. I think the suspension constraints are pretty reasonable, but I'm wondering about limiting the power to Spec E30 levels. Aside from Spec E30 and ChumpCar/LeMons, most performance-oriented E30s seem to be gravitating to the M5x motors due to parts availability, cost, and reliability.

[EDIT] D'oh! I forgot the most important part...WEIGHT. What should our hypothetical E30 weigh? What should its weight distribution (longitudinally and laterally) be? Has anyone had their E30 on a set of scales?
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Re: Making an E30 (Really) Handle

Postby M20_fever » Wed Jan 13, 2016 8:39 pm

I scaled my car before I put the cage in. I have the slip somewhere, but I think it was around 2650# with 1/4 tank of fuel and a fat ass driver, so dry it's right around 2400# and was nearly 50/50 front to rear. Defining best handling is impossible unless you focus on one application. Drift, rally, circuit, spirited roads? I can say that on the old H&R sports I had and 205 summer tires the car was a blast on country roads, but sucked ass on track. With the J-Stocks and 225 ultra performance summer tires the car sucks on any public road because you have to go WAY too fast to feel at all like your pushing the limit, and the ride isn't very comfy.
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Re: Making an E30 (Really) Handle

Postby blasphemy101 » Wed Jan 13, 2016 11:04 pm

M20_fever wrote:I scaled my car before I put the cage in. I have the slip somewhere, but I think it was around 2650# with 1/4 tank of fuel and a fat ass driver, so dry it's right around 2400# and was nearly 50/50 front to rear.

Wow - quite a bit lighter than I expected. Numbers are good.

M20_fever wrote:Defining best handling is impossible unless you focus on one application. Drift, rally, circuit, spirited roads? I can say that on the old H&R sports I had and 205 summer tires the car was a blast on country roads, but sucked ass on track.

That's why I'm asking for opinions. I'm not much interested in rally, so I'd like the discussion to stick to asphalt (pun intended), unless someone else has a particular need. Instead of looking at the applications for an answer, it might help us to narrow it down by the features that benefit those applications:

Drift:
Yoshi wrote:Drift cars don't like too stiff. Makes them snap back real bad. Soft is preferred for the gentle transitions. Just like road race setups.


Autocross: Higher Gs, responsive and slightly front-biased suspension to ensure power application on corner exit at the cost of absolute cornering speed

Circuit: Highest Gs possible (lateral and longitudinal), good feedback

Public Roads: Lots of driver feedback, responsive steering, driver comfort; all considered above absolute cornering speed

M20_fever wrote: With the J-Stocks and 225 ultra performance summer tires the car sucks on any public road because you have to go WAY too fast to feel at all like your pushing the limit, and the ride isn't very comfy.

Well, sure, but it handles better, doesn't it? ;)

What tire should our armchair E30 have? Does anyone know how much room there is under the front fenders? I know it is under-sized, but I'm leaning towards the Spec Miata Hoosier (205/50r15) as a model, since there should be lots of data available.
Last edited by blasphemy101 on Fri Jan 15, 2016 5:04 pm, edited 1 time in total.
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Re: Making an E30 (Really) Handle

Postby Yoshi » Thu Jan 14, 2016 2:38 pm

Drift is funny. More grip is preferred so you're almost at a road race setup. Then it's up to preference.

I'm gonna say J stock because it's modeled after the old gruppe N days. It was THE E30 racing class. With your constraints, that is hands down the best try tarmac performance you will get.

For tires, on stock steering angle, the best I've fit is a 215 up front without modifying stock fenders but man that's tricky. Rear, I've fit up to a 255 with just a fender roll. But then your car will be super understeer happy.
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Re: Making an E30 (Really) Handle

Postby M20_fever » Thu Jan 14, 2016 3:26 pm

Yoshi wrote:I'm gonna say J stock because it's modeled after the old gruppe N days. It was THE E30 racing class. With your constraints, that is hands down the best try tarmac performance you will get.


This. People argue me o this point a lot because "I can dial in adjustable coils to track conditions, etc..", which in some instances may be true, but the limiting factor in 90% of these situations is the human element. You need to actually know what your doing to design and tune a proper suspension, not just bolt on some off the shelf parts and "dial it in". I went with J-Stock because I know my limitations, and figured it was better left to people far smarter than me to engineer a proper suspension for the chassis. To date, I have yet to see an e30 that handles better than mine, and I take no credit for that aside from "I installed it". The spring rates, shock valving, and geometry is all perfect, and I don't have to "dial" anything in. The only thing I'm still missing is the proper sway bars, which is on the short list, but so far hasn't been a real issue.

Tire wise, bone stock fenders without even rolling them? At stock ride height you could get 215s with the right wheel offset. Mine are rolled and pulled and pretty low and I still fit 225s with a huge section width. The tire is almost 11" from sidewall to sidewall.
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Re: Making an E30 (Really) Handle

Postby blasphemy101 » Thu Jan 14, 2016 3:42 pm

Yoshi wrote:Drift is funny. More grip is preferred so you're almost at a road race setup. Then it's up to preference.

Interesting. I understand the need for grip, but I would think there would be some trade-off to make the suspension "too stiff" (as compared to a race car), in order to make it more responsive.


Yoshi wrote:I'm gonna say J stock because it's modeled after the old gruppe N days. It was THE E30 racing class. With your constraints, that is hands down the best try tarmac performance you will get.

I have the J Stock springs and dampers on my E30, so I agree. The spring rates seem to be a very good choice, and I can only assume the dampers are as well, but I don't have a good feel or understanding of them. I'd like to go through this process, and see if I arrive back at the same conclusion, though. There's also the matter of the rest of the car - how are other changes going to affect the spring rate and damping we need? In this regard, the J Stock dampers and springs are very limited, because they are not adjustable.

Our tire selection is also very important. Turner tested the J Stock suspension on street tires, so it is probably not optimized for the kind of grip they provide.

Yoshi wrote:For tires, on stock steering angle, the best I've fit is a 215 up front without modifying stock fenders but man that's tricky. Rear, I've fit up to a 255 with just a fender roll. But then your car will be super understeer happy.

I have fit a 225/45r15s street tire up front. Hoosiers run wider because they are "squarer." I don't think you can go much, if any, wider than that. I cannot fit a finger between the tire and spring perch. There is more room on the outside, but I still don't know if it is enough room to step up another tire size. Not to mention, I don't think 15" 235 tires exist. Like you've confirmed, there is much more room in the rear wheel wells. Do you know how much room you had on either side of the tire? I think a staggered setup could be made to work, especially when you consider how poorly the E30s rear suspension geometry seems. Larger tires are less load and camber sensitive. Running a slightly wider tire, with its better "behavior" and wider track width, as well as a stiffer rear suspension might be beneficial and serve as a band-aid for the rear suspension issues. But again, running a 235 or larger rear tire is going to require stepping those wheels up an inch or two in diameter. Since traction isn't a significant issue, I don't think a lot of stagger would necessary or beneficial, unless a ton of rear spring rate is required to prevent lots of squat (it isn't on a stock motor).

For a car with more power, no one can say for sure (without in-depth tire data), but I don't think you can run too much tire under stock E30 fenders. That said, there are a lot of things at play that go against a staggered setup on E30s. E30s have a long, heavy motor in the front, this coupled with big rear tires and a diff that takes advantage of them (depending on the type) is probably going to cause some turn in problems. Most off-the-shelf spring packages (H&R, J Stock, cheap coilovers) are also slightly front-biased. This is usually then mitigated by adding large, adjustable swaybars that reduce the total grip (F+R), but can make the car feel more neutral. This seems to work, so I wonder if it can be taken to further lengths on an E30 with staggered tire widths/wheels, or is the car going to be too limited by the lack of front-end grip?
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Re: Making an E30 (Really) Handle

Postby blasphemy101 » Thu Jan 14, 2016 3:51 pm

M20_fever wrote:This. People argue me o this point a lot because "I can dial in adjustable coils to track conditions, etc..", which in some instances may be true, but the limiting factor in 90% of these situations is the human element. You need to actually know what your doing to design and tune a proper suspension, not just bolt on some off the shelf parts and "dial it in". I went with J-Stock because I know my limitations, and figured it was better left to people far smarter than me to engineer a proper suspension for the chassis. To date, I have yet to see an e30 that handles better than mine, and I take no credit for that aside from "I installed it". The spring rates, shock valving, and geometry is all perfect, and I don't have to "dial" anything in. The only thing I'm still missing is the proper sway bars, which is on the short list, but so far hasn't been a real issue.

On a personal level, I agree with you; those are the same reasons I went J Stock on my car. BUT, I'm just armchair engineering here. I think the J Stock springs/dampers are the best OTS option, but there's no such thing as the absolutely perfect solution. For example, there are definitely some geometry problems with the J Stock suspension. The E30 suspension does not like to be lowered. Is some way to fix those issues, or is the trade-off for the the lowered (by a couple inches) center of gravity worth it?

M20_fever wrote:Tire wise, bone stock fenders without even rolling them? At stock ride height you could get 215s with the right wheel offset. Mine are rolled and pulled and pretty low and I still fit 225s with a huge section width. The tire is almost 11" from sidewall to sidewall.

At stock right height, you could run 80s F1 tire, because they're just stick out the sides -grin-
[EDIT] ^^^ Am I drunk? This was supposed to read "At stock ride height, you could run 80s F1 tires, because they'd just stick out the sides."[/EDIT]

Yes, I think measurements would show 225-235 is the maximum width for a tire that fits inside the fenders.
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Re: Making an E30 (Really) Handle

Postby M20_fever » Thu Jan 14, 2016 5:25 pm

I ran a staggard setup for a couple years, 215 front and 245 rear. It wasn't bad at all, in terms of understeer. The tires were regular 200 tread wear street tires so lateral grip was limited, but handling characteristics were still good.
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Re: Making an E30 (Really) Handle

Postby blasphemy101 » Thu Jan 14, 2016 7:30 pm

M20_fever wrote:I ran a staggard setup for a couple years, 215 front and 245 rear. It wasn't bad at all, in terms of understeer. The tires were regular 200 tread wear street tires so lateral grip was limited, but handling characteristics were still good.


Interesting that it seems to be relatively insensitive to the stagger.

You're running 225s with an ~11" section width? Hoosier's site says their 275/35r15 is that wide...
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Re: Making an E30 (Really) Handle

Postby M20_fever » Thu Jan 14, 2016 8:26 pm

yup, the 225/45/16 Star Specs I;m running have a 10" contact patch, and the overall section width is 11". They are WAY wider the 245/35/16 Toyo T1r I used to run in the rear. Dunlop did it to get around AutoX class restrictions on tire width. Thats why I always look at overall section width when sizing tires. The fit is so tight in the rear due to the late model arches that you can't just go off tread width.
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Re: Making an E30 (Really) Handle

Postby blasphemy101 » Thu Jan 14, 2016 10:11 pm

M20_fever wrote:yup, the 225/45/16 Star Specs I;m running have a 10" contact patch, and the overall section width is 11". They are WAY wider the 245/35/16 Toyo T1r I used to run in the rear. Dunlop did it to get around AutoX class restrictions on tire width. Thats why I always look at overall section width when sizing tires. The fit is so tight in the rear due to the late model arches that you can't just go off tread width.


Pretty crazy. +1 for shiny bumpers lol
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Re: Making an E30 (Really) Handle

Postby M20_fever » Fri Jan 15, 2016 2:21 pm

yeah, probably the biggest down side to a late model. Once I get the turbo installed (never at the rate I'm going) I'll be looking into some flairs and new wheels to get something in the 305-315 width in the rear.
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Re: Making an E30 (Really) Handle

Postby Yoshi » Fri Jan 15, 2016 3:43 pm

Man a lot happened here since I was last on.

Drift cars don't like too stiff. Makes them snap back real bad. Soft is preferred for the gentle transitions. Just like road race setups.

My way was getting J stock rates and accordingly valved dampers so that I could muck with it if need be. But so far, I haven't. I run 215s up front and 245s out back. I definitely notice the understeer.
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Re: Making an E30 (Really) Handle

Postby blasphemy101 » Fri Jan 15, 2016 5:02 pm

Yoshi wrote:Drift cars don't like too stiff. Makes them snap back real bad. Soft is preferred for the gentle transitions. Just like road race setups.

Good to know. I'll update my post with this tidbit. I need to get up to speed on drifting setups. I would have expected the suspension to be slightly stiffer in the rear (than a road race car), so it would be more neutral or even 'naturally' oversteer.

Yoshi wrote:My way was getting J stock rates and accordingly valved dampers so that I could muck with it if need be. But so far, I haven't. I run 215s up front and 245s out back. I definitely notice the understeer.

What are you running for swaybars?
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Re: Making an E30 (Really) Handle

Postby Yoshi » Fri Jan 15, 2016 5:31 pm

Uh. well for newbies that is what I would suggest. At the pro level, I see most setups being understeer prone. You want that traction to hook up and physically travel faster to get away from the guy that's chasing you. But you still want to be sideways. You know? This is why high hp is required and why people call it a "sideways drag race".
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