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      12-28-2016, 10:25 AM   #1
DailyN54
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XI on Road course

I wanted to get advice and impressions from some of you XI owners that take your car to the road course or auto-x events. I have been building my car for straight , However, I now want to improve my breaking and handling. I am going to put coilovers and sway bars . Is there anything else our cars need to handle well on a road course? What are your driving impressions at the road course? Does adding in a locking diff with AWD help?
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      12-28-2016, 11:43 AM   #2
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I don't track a Xi, but the chassis is not that different than mine. Save the money on coilovers, they do no good on track. Heavy sway bars ruin the handling too. A bigger front bar, Bilstein B6 shocks, and the M3 control arm upgrade and you will be good to go. Braking is always a problem till you move to a big brake system. The OEM calipers just can't take the heat.
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      12-28-2016, 02:45 PM   #3
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i ran mine at an autocross event years ago, i think i only had the UUC front/rear sway bars at the time, and it tended to understeer a lot, but that could have been driver error too :P
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      12-28-2016, 06:28 PM   #4
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Quote:
Originally Posted by E30_335i View Post
I don't track a Xi, but the chassis is not that different than mine. Save the money on coilovers, they do no good on track. Heavy sway bars ruin the handling too. A bigger front bar, Bilstein B6 shocks, and the M3 control arm upgrade and you will be good to go. Braking is always a problem till you move to a big brake system. The OEM calipers just can't take the heat.
Your the first person I have heard that says that coilovers or sways will not help at all. Can you elaborate? The dampening on the stock ride seems quite soft. Also the XI feels like it's on stilts. lol
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      12-28-2016, 07:46 PM   #5
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IMO, BMW did a great job with the E90's suspension, and the 335i's just need some enhancements to be great track cars. The dampening on anything from the factory sucks. The Bilsteins take care of that. I run stock ride height with the factory sport springs as the car likes some body motion to really be effective. A 28mm front bar with Powerflex bushings and spherical rod ends controls the sway, and M3 control arms give better caster/camber and quicker turn in. Then some Dinan camber plates to maximize negative camber, better trailing arms and a good alignment. For the rear bar I use the OEM 13mm with Powerflex bushings. Car turns quicker laps at couple of tracks with no rear bar at all as I can get the power down earlier, and the big front bar keeps the roll in check.
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      01-12-2017, 08:25 AM   #6
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As my name indicates this is a daily driver 90% of the year so I'm not interested in making this a racecar, just a very well-behaving car for both. Alignment is aggressive for the street but way short of a spec car on the track.

I'm on eibach springs and koni yellows half a turn from firmest on front and full firm on the rear, stock swaybars, stock control arms. Springs are actually for the i, not the xi - they lower the car pretty drastically and still pair well with the yellows. With this setup and good tire pressures the car rotates absolutely fine, I can even induce oversteer whenever I want. There's just some roll I would next love to take up with a front bar, like e30_335i describes.
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Originally Posted by E30_335i View Post
Save the money on coilovers, they do no good on track. Heavy sway bars ruin the handling too.
Tend to agree.
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Originally Posted by E30_335i View Post
Braking is always a problem till you move to a big brake system. The OEM calipers just can't take the heat.
Disagree, but I think it depends on the track. For instance Watkins Glen is the hellspawn demon consumer of brakes and tires. I found some mild fade toward the end of my sessions but I was able to manage it. If cash wasn't tight, I would adore a BBK, but I found a half dozen other valuable upgrades for that $2-3000.

Personal note - starting with only shocks and springs I feel I learned the car mechanics more easily and my skills improved a lot faster. (I was even reluctant to put my first set of rcomps on and considered staying on my all-seasons, for fear of losing that rate of improvement.) I incrementally discovered and executed what I wanted to do next - I haven't been for want of too much other suspension change. Perhaps after ctr arms and a front bar I'll revise this post.
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      01-13-2017, 07:01 PM   #7
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Quote:
Originally Posted by E30_335i View Post
I don't track a Xi, but the chassis is not that different than mine. Save the money on coilovers, they do no good on track. Heavy sway bars ruin the handling too. A bigger front bar, Bilstein B6 shocks, and the M3 control arm upgrade and you will be good to go. Braking is always a problem till you move to a big brake system. The OEM calipers just can't take the heat.
Don't want to open a can of worms here but the OEM XI suspension is very different from RWD. In a word it sucks, maybe worst ever put out but BMW. Too tall, too much body roll, over sprung, under damped and with the RFT's, just plain horrible.

One reason to get coilovers on XI is, contrary to RWD, XI is very hard to lower and get enough travel and the F/R rake right. But yes if you don't have to, get some decent shocks, lowering springs (ZSP work), at least a front bar (UUC makes the only one, there is a GB going on in the XI section). EG I had to go Eibach front springs, ZSP rear to get the rake right, rear was far too low with Eibachs. This is a problem with nearly all springs on XI. With CO at least you can adjust ride height and maybe depending on what you want to spend, get some extra travel in front which is very limited otherwise.

Nothing control arm-wise from M3 fits in front, but everything that fits RWD in back does. Beyond that you get into subframe bushings and so forth.

Tons of threads on this here in the XI section, OP I recommend you start reading more. XI suspension is very tricky to get right, even trickier setting it up for track.
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      01-13-2017, 07:05 PM   #8
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Quote:
Originally Posted by ajsalida View Post
Don't want to open a can of worms here but the OEM XI suspension is very different from RWD. In a word it sucks, maybe worst ever put out but BMW. Too tall, too much body roll, over sprung, under damped and with the RFT's, just plain horrible.

One reason to get coilovers on XI is, contrary to RWD, XI is very hard to lower and get enough travel and the F/R rake right. But yes if you don't have to, get some decent shocks, lowering springs (ZSP work), at least a front bar (UUC makes the only one, there is a GB going on in the XI section). EG I had to go Eibach front springs, ZSP rear to get the rake right, rear was far too low with Eibachs. This is a problem with nearly all springs on XI. With CO at least you can adjust ride height and maybe depending on what you want to spend, get some extra travel in front which is very limited otherwise.

Nothing control arm-wise from M3 fits in front, but everything that fits RWD in back does. Beyond that you get into subframe bushings and so forth.

Tons of threads on this in XI section, OP I recommend you start reading there. XI suspension is very tricky to get right.
Agree 100%. After not only owning a RWD and now having an XI the Xi suspension is definitely lacking out of the box compared to the RWD counterpart.
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      01-13-2017, 07:12 PM   #9
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Agree 100%. After not only owning a RWD and now having an XI the Xi suspension is definitely lacking out of the box compared to the RWD counterpart.

Yep. I've driven a number of stock RWD e9x cars and it is amazing how bad the factory XI susp is in comparison. I think the XI also needs at least a better front sway bar, to keep that McP strut AWD front end from washing out. Too bad only one is UUC, but it is a good one.
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      01-13-2017, 07:54 PM   #10
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Originally Posted by ajsalida View Post
Yep. I've driven a number of stock RWD e9x cars and it is amazing how bad the factory XI susp is in comparison. I think the XI also needs at least a better front sway bar, to keep that McP strut AWD front end from washing out. Too bad only one is UUC, but it is a good one.
Yep for sure.

The UUC sway bars are coming back We are taking pre-orders now.
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      01-17-2017, 02:20 AM   #11
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ajsalida is right about the XI suspension, it's horrible.

I've spent years on track, first racing GP motorcycles in both Europe and the US and then Karts, and cars, up to instructing in high horsepower AWD Audis before I hung up my track shoes and nomex a few years back.

First, the car needs a rear bar FAR MORE than a front bar on track. The cars are way to tight and literally plow into corners. More front bar just makes it worse.

An Xi will pick up an appreciable amount of camber as soon as you lower it to a reasonable height, even without adjustable CA's, and that will improve turn in a bit (as will 0/0 toe on front) but the last thing these cars need is more front bar until your spring rates are WELL north of 600. Trust me, you're not going there on a car you use on the street.

The Bilsteins are okay, as are the FSD's if they are properly sprung. Both benefit from the Eibach pro springs. Beyond that look at Eibach's ERS springs, they are better than any of the other common tuner springs most people go with (and I've seen the H&R's fail). Check vendors in Germany and the UK for the correct springs. Eibach's distributor in the UK knows their stuff.

A better setup altogether would be the Ohlins road and track setup. It's as good as you're going to get without going to TTX36's or a 4-way Moton setup, and that's gunna be in the $7k+ range to start.

PSI at Sears Point (Sonoma) Raceway can put a set together for you for just around $2000 and that may be the very best suspension shop you'll ever work with unless you have a truly big dollar racing program (and even those guys use PSI). They have done suspensions on two of my track cars and I have never found anyone close to them in the civilian market.

The OE bushings, in particular the fluid filled thrust arm bushings, are a complete train wreck. Get a press and swap them for high durometer poly. Do the same for the rear upper bushings. If you can afford it, do every bushing in the car. Just the thrust arm bushings will change your perception of the car's handling. Do all the bushings and you'll think the car can read your mind compared to the OE rubber.

Do not skimp on the bushings. The difference is NIGHT AND DAY.

As for swaybars; most people put too much bar in their track vehicles. Get the spring rates sorted first, then worry about swaybars.

When we did setup in my 440WHP (520+ crank) 3100lb Audi we did initial rate setup on the suspension WITHOUT ANY BAR. Once we had it dialed we went to a blade adjustable rear bar and a slightly bigger front bar, only to go back to the OE front bar. The car was ultimately a little loose, but very, very fast. The BMW has proven to be very similar in that respect (albeit better out of the box, but not by much).

Cars with too much bar tend to exhibit very twitchy, light switch handling characteristics on the edge. A properly damped and sprung car with less bar will be much more predictable and easy to drive at speed.

So, my advice..

1. Bushings throughout
2. Don't even bother with the Bilsteins or Koni's and go right to the Ohlins with Eibach ERS springs
3. Proper wheels with the correct offset so you can maximize the car's footprint width. Spacers if you can't replace your wheels. It will make a noticeable difference
4. Rear bar (though if you're doing the rear subframe bushings you may as well do this then as you're already there)

Then go drive the hell out of the car and destroy a few sets of tires. You'll end up getting the car dialed in for your favorite track and learning what you want in terms of tight/loose playing with the bar. Guaranteed it'll be different road vs track, so make sure that rear bar is adjustable. I actually run more bar on the street than the track, believe it or not.

The UUC bars are good, not many others are. The UUC bar on soft will get the car to rotate for a change and then you can dial the cars compression and rebound to your liking and getting the alignment/camber so that your tires are heating evenly. Aim for <8F difference across the width of the tire as a starting point. Adjust camber & temps till you find a sweet spot. This will all change as you get faster.

Once that's done start playing with more bar.

If you're not on full hard with the rear bar, adding a front bar will be pointless. If there's too much roll, try by adding compression damping and/or higher rate springs. A bar is no solution if the dampers and springs aren't dialed. It only masks the real issue and slows you down.

After you get the car initially set up, take notes, lots and lots of notes, and use the expertise of the guys at PSI, they know their shit and work with some of the best teams in the country on their setups. This is the main reason for buying from them.

Your next problem is going to be brakes. Once you start modding the brakes be sure you don't make the same mistake most make and screw up the piston ratio front:rear. Once you alter that the EBD is going to be totally messed up. Without reprogramming it and the car will be a disaster on corner entry, especially when trail braking. FYI - I don't know anyone who's successfully reprogrammed the brakeforce distribution on Bosch ABS controllers without shelling out huge $$$ for parameter definitions. Remember it's all tied into the traction and stability management. It's really easy to mess the car up here.

Last edited by NiNeTyOne; 01-17-2017 at 04:03 AM.
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      01-17-2017, 07:34 AM   #12
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+1 great post. Lot of good info.

On the rear bar only, I have to disagree. I ran my car (on the street) with Koni/eibach, subframe bushing inserts, and E92 M3 rear bar/bushings, and stock front bar. Absolutely crazy amount of snap oversteer. Under power say coming out of a corner front would wash out, wash out...wash out...then sudden bang, outside front tire dig in and rear end comes around. You could control this with gas pedal, changing F/R weight distribution. Off gas or under even mild braking coming into a corner, you could feel it want to rotate all the time around that outside front tire in even the smallest steering inputs, got to be really annoying. Stock 18" staggered wheel/tire sizes.

Fun at first like a drift car is fun but after just a few days it was tiresome and frankly scary waiting for the back end to come around all the time. I went with a UUC front bar, thing is nice and neutral now, slightly rear-biased. Really can't tell it is AWD from the handling balance at least. Supple, compliant, not too harsh and I live around some really bad roads (remote high Rockies SW Colorado).

Good point about springs, get them and relative F/R roll stiffnesses, ride height etc. sorted out first then bars to tweak. But, I prefer for street cars at least, relatively softer springs and bigger bars. Also this platform, and AWD version of it especially, the front bar does not add tons of understeer, counter intuitively it helps the McP strut front end keep the tire in better alignment with the pavement, so you actually get more front bite out of it under heavy cornering loads, not less. This has been my experience at least on the street and not with sticky race tires or going all out limit driving (which is stupid IMHO on the street at least, esp where I live).

I know it sounds odd about the front bar but I do have some experience setting up and driving tracked cars: street, dual duty street/track, and all out track cars. I had read all the theory and hated the way the OEM XI susp and later the K/E set up understeered (plowed) so badly. So I was really surprised when a small mod like a larger rear bar had such a dramatic effect with the oversteer. I am not sure how it would work with only a front bar but other have noticed it actually tames the understeer, which is as I said very non intuitive. Plus the rear bar install is so time consuming and the front very easy, front can be done right away and rear wait until time/money is right. Then there's the UUC thing and front bars may not be available much longer.

I guess another way to look at this is, understeer due to loss of traction in front can happen in two ways. One is the standard way, with the tire in optimal orientation to the road, with all the tread in contact. eventually side loads overcome lateral traction and the tires slides sideways. The other way is the tread is not fully in contact with the road, the orientation is not optimal, the tire is leaning over the wrong way (positive camber WRT road surface) inner edge of the tire is lifted up or has less downforce on it. So the front washes out just due to poor susp geometry and goofy tire orientation under load. Add AWD to this and it is even more screwy because power is being sent to those front wheels same time.

The front bar fixes the latter issue so that loss of lateral traction (and forward due to AWD!) in front if it happens, happens in the best fashion: only after getting ALL the stick you can out of the front tire, then ALL the tread is overcome by side loads, not just a small portion of it. So fix this first then add rear bar to suit.

Anyway JMHO.

Oh, and one last thing, about bushings. Get rid of those big fat front fluid-filled tension strut bushings ASAP. Enormous improvement in steering feel, response, and precision. Literally night and day. Also they (OEM) are one big source of poor front wheel alignment under loads, they deflect quite a bit, they pop and leak etc. Really awful pieces. I went with Strongflex poly, some guy is making spherical bearing type if you want to go that way though they are a lot more expensive. Whatever, just get rid of them.

Last edited by ajsalida; 01-17-2017 at 08:05 AM.
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      01-17-2017, 09:11 AM   #13
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Heres my two cents for whats its worth. I just installed a set of Synchro Design sealed spherical bearings and I can say they are amazing. The difference between stock and even inserts is so much better. The only downside is the cost and a little more road vibration but considering I never will need to buy another set of thrust arms its totally worth it.
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      01-17-2017, 08:43 PM   #14
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Quote:
Originally Posted by ajsalida View Post
The front bar fixes the latter issue so that loss of lateral traction (and forward due to AWD!) in front if it happens, happens in the best fashion: only after getting ALL the stick you can out of the front tire, then ALL the tread is overcome by side loads, not just a small portion of it. So fix this first then add rear bar to suit.
Snap oversteer after understeer is without question a damping and spring rate issue that is possibly exacerbated by inadequate rear brakes. This is made all that much uglier by the fact most car's rear toe links are shot (and are sloppy rubber to start with). If you can this is one area where the highest durometer poly makes a big difference. I have seen this issue so many times on student cars I cannot tell you.

This is probably the most common setup problem I've seen over the years (like 30+ of them). Most people mod the front brakes, put inadequate springs for the job on the car and then pile into corners pitching all the weight on the front, then the toe link ends are moving all over the place as the rear suspension comes back into play... Plowwwwwww and then, wait for it... SNAP!

BTW, Dinan has a nice fix for this but it's not cheap.

If I had $10 for every time I've seen cars set up like this I could retire in Monaco.

One other pro tip here.. add a tiny bit of toe to the rear when you do all this. Not much, just a couple seconds of arc. It will radically improve the stability of the car under hard braking once you add more rear bar. As a bonus, the car will be significantly more planted off the corner on throttle and not have a tendency to step out as much, giving you much better drive out of corners. I think factory is 0/0 toe in the rear.

On the e91 I run 0/0 front and toe the rears in 00'02"

Depending on the age of the car, what's worn and what's being replaced it's almost impossible to guess what the car will really handle like out of the box, but corner balancing the car will be a good start once the new dampers and bushings are in. I'd calculate the rake as it comes from the factory, lower the car on all four corners about 1-1.3" till it balances and you have essentially OE corner weight distribution and then drop the front about 2-3mm more. Much more than that and the camber is going to be too extreme for good tire wear on street until you get adjustable upper arms.

Keep in mind the car will settle over a couple weeks when you put all the new bits in.

Drive it and report back, but keep in mind, if the car has even 20k on it your bushings are garbage by any performance measure, so start there and at least make sure the chassis connection is solid.
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      01-17-2017, 08:48 PM   #15
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Quote:
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Heres my two cents for whats its worth. I just installed a set of Synchro Design sealed spherical bearings and I can say they are amazing. The difference between stock and even inserts is so much better. The only downside is the cost and a little more road vibration but considering I never will need to buy another set of thrust arms its totally worth it.
I have run a lot of spericals on track over the years, but if you're going to be on the street they will get dirt and dust in them and be toast in short order, then you're replacing them every year or even more frequently.

The sphericals on my dedicated track car were sloppy after less than 2000 miles, and that's pretty good. Most race teams that use them expect them to be replaced annually. We replaced them on the Pro3 car annually. That car saw a Pro3 season plus once endurance race a year, and they were trash when they came out.

If yours last longer than a year with regular road use I will be VERY surprised. If you were up here where it rains sideways half the year, I'd be impressed if they lasted 4 months.

Just use high durometer poly throughout if you plan to drive it on the street.

The earlier mentioned Strongflex bushings are pretty damn good. The red ones are even tolerable on the street if you have really nice dampers.
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      01-17-2017, 09:17 PM   #16
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It sounds like you guys have a bit more experience with bars and camber etc. If I'm being honest I'm at the "very good intermediate" level and yet unable to feel finite camber differences, or lacking the experience in a car that has a much more track oriented suspension. I feel I understand the car's mechanics well, I'm able to throttle lift oversteer and trailbrake for the result I want in and out of corners, but I would imagine a couple of you guys would think it's sloppy. Perhaps it's a lot like having never driven a 700hp car and believing your 400hp car is lightning fast (which mine is!).

So...my own question for you guys -
Is the reason I believe the K/E setup is a good one, because I'm an inexperienced driver who hasn't driven a better setup? Just noting massive improvement from my track days with stock springs and blown shocks? Or am I actually a great driver with a relatively sloppy car?!

The discussion on poly bushings has me regretting not popping them in before replacing my shot control arms.

Because I believe I like the stock plus K/E setup, or at least well enough for a dual duty vehicle, I may aim to get a bar in there and see what changes. (I've heard conflicting advice before on front bar vs rear vs both... There was a Randy Pobst article in GRM about installing a FRONT bar rather than a rear bar, and I believe to ajsalida's point, trusting in a bit of understeer mechanics).
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      01-17-2017, 09:18 PM   #17
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Quote:
Originally Posted by NiNeTyOne View Post
I have run a lot of spericals on track over the years, but if you're going to be on the street they will get dirt and dust in them and be toast in short order, then you're replacing them every year or even more frequently.

The sphericals on my dedicated track car were sloppy after less than 2000 miles, and that's pretty good. Most race teams that use them expect them to be replaced annually. We replaced them on the Pro3 car annually. That car saw a Pro3 season plus once endurance race a year, and they were trash when they came out.

If yours last longer than a year with regular road use I will be VERY surprised. If you were up here where it rains sideways half the year, I'd be impressed if they lasted 4 months.

Just use high durometer poly throughout if you plan to drive it on the street.

The earlier mentioned Strongflex bushings are pretty damn good. The red ones are even tolerable on the street if you have really nice dampers.
You missed a very important word in my post ....sealed. I would never use a typical open sherical bearing in this sort of application. These are sealed spherical/monoball bearings produced in Germany. He's been making thrust arms for other BMW series for a while with nothing but great results.

As far the inserts...been there and done that. IMHO dont come close.
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      01-17-2017, 09:21 PM   #18
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You missed a very important word in my post ....sealed. I would never use a typical open sherical bearing in this sort of application. These are sealed spherical/monoball bearings produced in Germany.
Yes, sealed makes all the difference.

What does he want for a set of these? Does he make rear toe links as well? If I could get those in a sealed assembly I'd be all over it (Dinan's are a bit too precious).
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      01-17-2017, 09:33 PM   #19
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$500 and some change. Not cheap but I figure if I bought two or three more sets of thrust arms during ownership I would walk away with a win since they improved the car so much and I would basically have paid the same thing over the life of the car.

He could probably make you up a set of rear toe links. He's set up as a fab shop and I have discussed a few other things I would like him to work up including a new lsd center diff.
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      01-17-2017, 09:41 PM   #20
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If you're looking for a rear LSD you should call Dan at Diffs Online, even the guys at OS Gikken send people to him, he's that good.

190 Rear Main Street Unit 1, Wilmington MA 01887 Phone 800.219.0485

He even redoes the bearing races and tosses the shit ones BMW uses.

I don't think anyone is as good as Dan in the LSD department with these cars.

If you have a chance to inquire about those bearings, I'd like to know who's bearings he's using. I've done a lot of work with Barden on ceramic motorsports application stuff. If he has a press in solution for one of the good arms I'd be interested in that for sure, especially the upper rears.
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      01-18-2017, 02:03 AM   #21
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Originally Posted by FamilyManTrackSedan View Post
If I'm being honest I'm at the "very good intermediate" level and yet unable to feel finite camber differences, or lacking the experience in a car that has a much more track oriented suspension. I feel I understand the car's mechanics well, I'm able to throttle lift oversteer and trailbrake for the result I want in and out of corners, but I would imagine a couple of you guys would think it's sloppy.
Use temperature to determine how to twiddle your camber and in 99% of all cases you'll be on mark.

If the inside of the tire is hotter than the outside when you pit, you have too much camber, too hot on the outer edge, too little camber.

This is a basic rule of thumb, and there are good reasons to go break the rule sometimes, but it will provide a good starting point for you.

I ran slicks on track and shot for contact thermometer readings at 4mm depth of 192-198F typically staying inside a 6 difference across the tire once I had pressures figured out. Pressures factor here as well as track temp, so make sure you keep notes on all those as you record your progress. It's all interrelated.

Just start with a good setup, talk to PSI (as they are not snake oil salesmen) and then go experiment and take notes.
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      01-18-2017, 07:07 AM   #22
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Snap oversteer after understeer is without question a damping and spring rate issue that is possibly exacerbated by inadequate rear brakes. This is made all that much uglier by the fact most car's rear toe links are shot (and are sloppy rubber to start with). If you can this is one area where the highest durometer poly makes a big difference. I have seen this issue so many times on student cars I cannot tell you.
Umm again, disagree. This is a big fat rear sway bar issue. This was on a barely 2 year old car with under 20k miles. The snap oversteer occurred ONLY after adding a bigger rear bar. Brand new Konis, brand new Eibach pro kit springs (which are admittedly sort of soft but that's what I wanted). Good alignment. Konis set mid range. Good tires etc. and without bar exhibited same kind of understeering behavior stock car did, just with a lower ride height and better damping of wheel & body motion with the konis. Just too much body roll. Furthermore if it were due to bushings or toe or whatever, a near-matching front UUC bar would not have fixed it. You can't have wildly different (total) front vs rear roll stiffness and expect a car to handle well. Rear brakes? Come on, man. I am not saying the issues you raise don't affect car's handling, and students do some strange things with their cars, but this is not that.

Don't want to get into a pissing contest here, just FYI for people considering this mod to think it through and beware the handling after adding a giant rear bar only may be very squirrelly. Esp on track at the limit. It may feel "awesome" to a novice but I found it scary and dangerous. Quite a few hard core track e9x non-M and M drivers run with no rear bar at all, esp with stiffer rear springs. The thing with McP strut and front bar/understeer is pretty well known. It was an issue on my old 2002 ITB car 25 years ago. All adding the front bar does to this specific chassis under these specific circumstances is make sure the tire gets all the traction it can get before letting go, under conditions of better matched F/R roll stiffness. Once you get the susp so it can let the tires get the most stick they can, then you can tune with relative F/R rates and so forth (adjustable rear bar helps, wish I'd gone UUC instead of M3 for this reason). Then there is a whole other issue of rears bars and LSD.

I also have a E36 M3 set up similarly. Owned since new. Koni/Eibach pro kit springs and F/R sway bars. Remarkable how similar they handle now, the XI esp after adding the front tension arm bushings to tighten up steering feel. XI of course is a pig weight-wise in comparison but factor that and the AWD out the overall balance and feel is very close. In fact that was what I was shooting for modding the XI suspension, the OEM was so bad I wanted to see if it could get close in feel to the M3. So far so good.

Not a lot of discussion about this, but a lot depends on spring stiffness vs bar stiffness. For example H&R race springs are very stiff, esp in front. Eibach pro kit are very close to stock RWD sport package (ZSP) rates, so relatively soft vs most aftermarket, even a bit softer than OEM XI. Therefore the contribution to overall roll stiffness from just the springs is much higher in the H&R than the Eibach, and more in front. You add bars to both (or even just to OEM XI) and you'll get very different results. Neither is "wrong" you just have to be aware of it. As I said earlier I prefer due to the terrible roads where I live, softer springs and stiffer bars. IE I get a lot of my roll stiffness from the bars, so adding a big rear bar to ZSP-like springs went way over the line to oversteer. That may not be the case with another set up. Another way to say this is, if adding only a big fat rear bar "fixed" your handling, your front springs were probably far too stiff.

If you haven't personally modded an XI in this manner it may surprise you. It isn't an Audi, which is a FWD platform with AWD grafted onto the rear. It is a RWD platform with AWD grafted onto front, and AWD biased to the rear. The other reason I'm bringing this up in detail is there is only one company making front XI bars, UUC. They had stopped but a vendor here got them to make a limited run. If you want one you'd better get it now. GB thread is in this section, no affiliation whatsoever.

Finally, I was not aware Ohlins made coil overs for XI? I am only familiar with them from motorcycles but they are pretty (damn) good shocks. Just a set of 2 for a motorcycle is close to 2500.

Last edited by ajsalida; 01-18-2017 at 08:20 AM.
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