How do Improve the E9 handling

Hi all -

I have a '73 CS and, while I realize that an E9 is more of a grand tourer than an autocross demon, I still think the handling is a bit too sloppy and there is too much body roll. I'd like to tighten up the handling "the BMW way" rather than just slap on a bunch of aftermarket parts. Can I assume that the CSLs handled better? If so, how? Larger sway bars? Different springs or shocks? What's in the RealOEM parts bin that I can use?

Any advice would be appreciated. Thanks.

parts

go to www.realoem.com and follow what comes up. You can find all the factory bits there as were provided for cars sold to the public. As for in-house stuff, or aftermarket tuners, you're out of luck at realoem.

Look for old racing versions prepared by tuners of the day, many of which are by now gone on to other things.

As always, how much money you want to spend will be the critical factor.

Many start with the tried-and-true collection of carbs (3), headers, higher compression, larger capacity, slide throttle induction... but fuel injection may offer a more efficient means of induction than carbs. Always make sure you have a cooling system that is working at full capacity.

Other bits include larger rims and tires, stiffer springs, stiffer shocks, thick sway bars, chassis stiffening and so on

In terms of the handling, there are several ways to go. Based on the forum reviews I have read, Carl Nelson's spring/shock/sway combo is very, very good overall.

I do not think there were many "period" upgrades that can be found and modern/recent items have been able to dramatically improve the nose diving that the original configuration fell victim to under relatively mild turning.

The most instant (one day) handling improvement I made was the installation of the Carl Nelson large sway bars but it should be in consortium with other upgrades especially brand new HD's. Also getting larger than 14" tires was a large help as well but requires you to find a set of Alpinas, BBS, etc. Good luck.

1. New Bilstein HD's, all the way around
2. ST/Nelson large sway bars
3. Carl Nelson lowering springs
4. 16" Alpinas

I have the setup Shawn describes for my 2800 and would recommend it. It simply handles better than my stock CSL (City Package). Unless you need to remain OEM, I'd go with Carl's setup.

The only item I would add to Shawn's list (assuming you're not doing a full restoration where you can add chassis stiffness directly) would be to add a crossbar support between the rear shock towers, and move the battery back there at the same time.

I've actually moved up to 17"s on my car but they are of course not period and require the fenders to be lightly rolled.

Fixed or adjustable camber plates on the front.

Anything you can do to stiffen/strengthen the chassis is worth doing (like the front strut tower bar). Seam welding any and every joint between the panels that make up the unit body is a cheap but labour intensive DIY project that makes a big difference.

Doug

front strut bar

I have Carl's set up also and it is very good although when I discussed it with him years ago, he preferred a 14" based wheel/tire solution. There are lots more tire options with 16s so I went that way.

May as well get a front strut bar (I'd get a front over the rear but both would be the ultimate). Unlike on a lot of cars, strut bars actually make a difference on Coupes.

With this set up, these cars will actually handle kinda well in a 70s-technology-No-B-pillar sort of way.

Also consider KW coilovers - variant 3?

http://e9coupe.com/forum/showthread.php?t=3341

How about changing bushing to polyurethane or Delrin. Camber plates. Are there any products that change Caster (more negative)?

I would first check the OEM setup. Suspension Strut Mount, Sway Bar Bushings things like that. I have always had CSI’s one CSL so the OEM front stabilizer bar (anti sway bar) was already there. Positively HD Bilstein shocks and would I stayed with new OEM coils for the California pot-holes slalom course now days. You don’t want to hit to hard I seen a window crack once from running Koni shocks on a friends CSI years ago. And always run high-end Pirelli Tires too. The polyurethane bushing are good watch Delrin material, worked with it for years it goes bad with any direct sunlight contact.
Before a strut tower brace check the body structure out real good. Shock towers body metal, rocker panels, the sub-frame connection from front to back is in there.

With everything tight and new as I said with new stock OEM coils a 250 pound guy can push very hard on the roof side and it won’t move 1” inch, stiff enough for the road more if you’re street racing.

Cross Bar Support

I would second the recommendation to add the rear shock tower cross bar. In fact I have the CN lowered springs, CN/ST sway bars, and Bilsteins. And the shock tower bars (front and rear) were the most significant handling improvement of the bunch for me. Part of the improvement maybe be perception because of reduced body flex, but if I had it to do over I would start with the shock tower bars front and rear.

The 29mm ST/CN front bar adds a lot of chassis stress and I have blown out the chassis mounts twice. First the tabs broke off, then reinforced tabs pulled the top of the subframe up and cracked it on the sides. I have re-welded it and hopefully it will hold this time. Too much fun I guess! But understeer/oversteer is nicely balanced with the front/rear ST/CN bars so I think they are worth it. As I recall I upgraded to the 29 mm bar from a heavier than stock 25 mm bar which I had used previously.

rear strut bar

Jan,

Where did you get your rear strut bar?

The rear shock bar must stiffen the body somewhat, but it can't have any appreciable effect on handling.

In the front, yes, those are struts and the tops carry significant lateral loading....a bar there will make a difference.

However, the rear shocks always have zero lateral load. Always. All the lateral forces are carried by the trailing arms and the subframe.

Sorry...pet peeve of mine...I think they look cool, but they're not "strut" bars.

Thanks for your input

I can't tell you exactly how or why it works. I bought directly from Top-End Performance Import Engineering, 7452 Varina Avenue, Hollywood, CA (www.racetep.com).

But it did seem to make a big difference on my car. I had a direct before and after comparison with no other change other than battery location. My perception before and after was that it was about as important as the front bar. And I wasn't drinking (or enjoying anything else) at the time.....

I guess it is possible I was dreaming, but I don't think so. I have made a lot of modifications to my coupe over twenty years, and I think the rear bar (whatever you want to call it) was one of the best. I think the two bars in combination are more important than heavier sway bars, at least with the CN springs. But it is just my perception. I did not do any skid pad testing. I am just going by how the car felt and how confidently it handled. Perhaps it is just that the body is stiffer so I am more comfortable pushing the car closer to its limits, I don't know.

Thanks for the other views as well. I did not use the proper terms. The official name for rear the brace from Top End is "Rear Battery/Shock Brace". I appreciate the correction. The brace includes a bar connecting the rear shock towers horizontally along with angular braces bolted to the floor surrounding a battery holder in the center. I will post pictures. They sold these for both the coupe and 2002. I have not checked to see if they are still available. I hope so. It is a good cross brace. I will post a picture soon.

I have put twenty years of labor and love into my coupe; thanks for letting me share what I think could be of value to others. I have no interest (although I like to support CN who has been of immense help to me over two decades).

Hi JAn, if possible could you post a photo or link to the rear bar?

'69 2800cs said:

The rear shock bar must stiffen the body somewhat, but it can't have any appreciable effect on handling.

In the front, yes, those are struts and the tops carry significant lateral loading....a bar there will make a difference.

However, the rear shocks always have zero lateral load. Always. All the lateral forces are carried by the trailing arms and the subframe.

Sorry...pet peeve of mine...I think they look cool, but they're not "strut" bars.

Click to expand...

Right on!!!! Rear end springs are attached to "chassis frame", not shock towers. Loads that the shock towers see are only generated by intermittent bumps and for only very brief periods of lean. Shock towers do not support constant loads and have little effect on leaning in turns. I think you'd have to be doing very aggressive rapid chicane shifts to notice otherwise. If these were coilovers, it would be a totally different story. If your suspension bushings haven't been refreshed in years, I think you are best served by starting there. Relative cost for new "A" frame rubber, steering linkage rod ends, associated rubber bushings and poly bushings for rear trailing arms is not bad and can make a big difference. After that, beefy bars and springs are the way to go..... Huge difference! Carl's set up offers nice and flat cornering but not overly harsh ride. I think seam welding some of the points in the rear can add just as much integrity if not more than a rear support bar. I'm ready to take some heat on this, but I think if you want junk in the trunk, move the battery back there, ideally as low and as far forward as possible. If I could do without a spare tire (for crash protection et al), that's where I'd put it.

Rear Shock Brace and Battery Holder

Here are the pictures I promised. Hopefully they will be helpful.

A few thoughts on this rear cross brace. When I first got the brace I did not think it would fit. It looked off by almost a half inch (too wide). But with some elbow grease if popped in nicely. I was surprised how much the body parts moved.

I was also reluctant to put bolt holes in my shock towers. I had inspected them closely and the prior owner had done a nice job reinforcing the washer at the top with a TIG welder and they were solid with no rust so I went ahead and am glad I did. I have never had any second thoughts on this.

The brace bolts to the floor in front and above the spare tire and has no impact on spare tire access. It is very strong and protected by the wheels to the side, the subframe below and the trunk to the rear. There is sheet metal (also protected) in front, so I have no qualms about the battery in an accident. BTW I have been very happy with my gel battery.

I guess what to do about suspension depends on where you start and what you want. I originally had a 25mm front sway bar and also one in the rear (12 mm?). Prior to the cross brace, I had already welded my seams with a bare metal restoration a few years earlier. I had also replaced all of the rubber suspension bits at that time. These helped a bit (my rubber was in good shape before actually) but I felt like I was driving a boulevard crusier and that the car still felt like it might come apart if I hit a big bump hard. It shook like early american convertibles. I wanted a car that handled like a BMW. At the time my daily driver was a 1990 325ix. I don't race or autocross, but I am an aggressive street driver who appreciates the curvy roads of Northern California.

I didn't feel like I had achieved a BMW result until I added the rear cross brace. In retrospect I suspect I would have been happy with the rear cross brace, the front strut brace, the CN springs and my original sway bars. Handling would be less flat (more like a late model M3 whcih feels pretty soft and rolls a bit), but I would be happy.

I am starting my third repair now on the chassis mounting points for that beefy 29mm front bar. But that is over 70K miles. And I certainly plan to keep it. In fact I was talking to customer support at ST when planning this repair and they indicated the bar has been discontinued. I am sure CN has a good inventory (he always does), but if you want the bar you might not want to wait too long.

If you are curious, the vinyl covered box in the picture above the rear stress bar is an air suspension box for the sub woofer (and other speakers) mounted in the rear passenger shelf.

agree...

connecting the rear shock towers would have limited results on a street car with rubber subframe and trailing arm bushings. If you're connecting the towers the subframe mounting area should be tied in as well to triangulate the forces but again, overkill for a street car (Edit: just like the pictures- nice).

The battery relocation makes a noticeable difference in handling and with some of the new gel batterie you can hide them, like under the rear seats. The rear-end hooks a up a lot better with some weight back there.

Like Ed says- start with the 35 year old wear items first, then play with bars and springs. My first E9 was a mostly dissolved 2800CSa hotrod done on a low (can you say no) budget. I cut one coil off the stock springs, moved the battery to the trunk, bolted on a 635 front sway bar and left the original rear bar in place. I'm sure my romantic reminiscing has clouded my memory but I recall that car handled like it was on rails but was still compliant enough for daily driving.