strange wear in front wheelwells

[AC]

anyone else getting the plastic splash guard things in the top part of the front wheel wells worn through? My car's not lowered and I have 17" wheels yet the small outer lip is almost separated from the rest of the piece and there seem to be holes forming towards the middle (from inside to outside) of the piece? could it be tires rubbing at full compression? Road debris sandblasting the part? Heat? :confused:

[TeamM3]

yep, tire rubbing under full compression and/or body roll

what size wheels/tires?

do any track/autox?

[AC]

both autox and track

As you know front tire size is pretty much strut clearence limited so both track and autox rims have 225/45/17 for the front.
It must be very soft plastic because I see NO evidence of rubbibg on the tires.
I have to see if I can get them replaced under warranty:eeps:

[TeamM3]

what is the front wheel size and offset?

check and make sure a rear swaybar endlink did not pop off the bar end.

[daven]

Its been a long and involved process. About 18 months in the making.

1. First time on the track with stock suspension and 16" stock wheels= severe body roll - but no rubbing.

2. Upgrade to 17" staggered wheels (slightly different offset than stock with stock size tires) and Bilstein Sport shocks (no $, so stay with stock springs.) Reduced body roll but rubbing thru the passenger wheel well. Gets worse, as I get better at the track.

3. Upgrade to H&R sport springs. Much better performance.
But rides like a brick on the street and the rubbing has gotten critical. Now its on both sides and so far through the plastic, the tires are leaving rubber on the inside of the hood. Not a happy camper.

4. Talk to Mike Morris of Schneller BMW, a local tuner, that owns and runs an S52 M Coupe. He's baffled at first, but looks closely at the car. He discovers that there is practically no travel left on the shocks with the H&R springs. He says that he has found that Bilsteins are "too soft". He has modified the suspension on his M coupe and wants to try coil overs but needs to sell his suspension. He cuts me a deal I can't refuse and we put in the following:

- Koni M Coupe Adjustable front Sport struts in
modified E36 M coupe strut housings
- Offset M3 strut tops
- H&R M Coupe front sport springs
- 23mm M coupe front and 19mm rear swaybars
- Koni Adjustable M coupe rear shocks with E46 M3 shock
mounts
- B&G E30 M3 Rear Road Race springs

The car is now pleasant to ride in on the street, the performance on the track is unbelievable and there are no holes in the my fender liners.

I am now a very happy track junky.
:thumbup:

[AC]

I'm running the stock wheels with 225/45/17 and a 5mm spacer to accomodate the fatter Pilot Cup tires when I use them for track. The car is set up for SCCA AStock, Koni DA, a (questionable) Dinan front adjustable sway bar

[BTW team z4, I think you know about this, is it possible I was sold an e36 m3 bar? Anything beyond the second of four holes and the links bind with the brake hose mounting clips on the strut, the bar preloads...the geometry is way wrong...but the car becomes a monster slalom/offset machine!??]

[TeamM3]

my past E36M3 bar had 4 holes, the Z3 bar had only three, both were Dinan but the bar for the non-M Z3 is most likely a different diameter than the MZ3 version

is there not any way to add washers and stand the endlinks off further from the struts to gain additional clearance, you may need aftermarket heim endlinks to accomplish this (GC, etc)

you might also be able to get someone to bend the swaybar arms in a bit to accomplish the same thing

you might also be able to bend the hose brackets some for additional clearance

these bars also have a tendency to shift off-center, the drop hoop in the center creates bending forces as well as twisting forces, bolt-on collars are available to keep the bar centered between the frame mounts

[AC]

Thanks Mark,
I have already bent the tabs but I think the right way is an adjustable lenght end link, if anything to be able to take the pre-load off the bar which is heavy past the second hole. This bar has 4 holes (I have an MCoupe btw) it's the same size as stock because it fits in the original bushings perfectly. Clearly, past the second hole it's nor really right and I'm kind of surprised Dinan would even make it that way. HOWEVER when I did have it in the third hole and the steering was heavy and it was binding at full lock.....man could the car transition! A slalom beast, 65mph offset? no problems! sweeper required more patience but hey I could deal! So what, in tuning terms, was going on there and how can I get that back, the right way?

[TeamM3]

sounds to me like you have the E36 3/M3 bar. though I'm pretty sure there should not be an issue with that on the MZ3Z front suspension

there also shouldn't be much of a pre-load issue regardless of what hole position you are using, but I suppose it is possible. You may want to make sure that the new position is not just taxing the available rotation capability of the OE endlinks. The aftermarket endlinks allow for a wider range of rotation. You really can't go wrong with the GC endlinks at $99/pair

Pre-load is a tricky thing to get just right, there are a lot of variables that lead you to think there is pre-load and you then actually adjust true pre-load in trying to fix a problem that does not exist, so be careful

otherwise it sounds like you are on the right track, the sweeper condition would be easily resolved if you had rear alignment capability but unfortunately that is one of the limitations of the Stock setup. There are some other allowable things you can do; custom shock valving, custom wheel offset, etc, to help compensate but it can be a rather involved both in terms of cost and time. Learning when to be aggressive and when to take it easy as a driver can usually yield the best improvement for the least cost.

[AC]

how would custom offset come into the picture (dynamically)? As I understand you can only change the track by +/-6mm. how does track change the dynamics?
Anyhow, I more or less set up the car and chaged my driving style after reading an article you wrote about running e36 m3s
http://patriot.net/~m3/uuc/howto/suspensn.html
minus the alignment stuff which is not possible. I have Koni DA front and rear valved by GC, they have a good range, I find I'm never all the way in any adjustment.

BTW, will you be at the DC stop on the Tour? I hought of running the coupe but it was logistically to difficult so Carlos Gomez and I will pool our efforts and drive his M3 in AS.
thanks for the input!

[TeamM3]

now you're asking me to spill 7 years worth of hard earned experience ... :eeps:

unfortunately I cannot make the DC Tour event, it's a 825 mile trip each way and I have too many other things going on that month

my next big event is the Peru Tour on July 4th weekend.

[AC]

Originally posted by TeamZ4
now you're asking me to spill 7 years worth of hard earned experience ... :eeps:




booooooo!:tsk:

fine, be a tease!:drink:

[TeamM3]

well, if you were going to order custom wheels how would you order the offset and what would be your reasoning for doing so?

[AC]

Hmmm? well, all I can think is I (for stock class)would get the maximum allowable track, in the front anyway. So OEM track + 6mm?

Aside from a wider track I would look to get the maximum clearance from the strut in order to fit the widest possible tire.

[TeamM3]

that's 6.2mm/0.25" x 2 = 0.5" track change

and your reason for wanting a wider front track (other than the strut clearance)?

[AC]

Wider track = more front stability (yikes, it's the Pontiac ad!), more stability= less understeer?

But if that's true then conversely less rear track equals more tendency to oversteer hence (ideally) if you were to go +.25" front and -.25" rear you could keep a wider rubber in the back for more grip yet have balanced the car's rotational attitude somewhat? (if you were to order custom wheels that is because I haven't seen negative spacers for sale anywhere, have you?):rofl:

[TeamM3]

you're getting warmer :thumbup:

and what are the OE MZ3 track widths?

[AC]

56" front, 58.7" rear.....56.5F, 58.2R maximum correction....:dunno:

[TeamM3]

OE difference = 58.7 - 56.0 = 2.7" wider rear track supplied by BMW

custom wheel = 58.2 - 56.5 = 1.7" wider rear track for Stock

one of the reasons these cars understeer is because of the rear track width bias, using the 1/4" allowance to it's fullest you just closed that gap by 1".

Next question, what is the impact of offset on the effective spring rate?

[AC]

I know where this is heading....I'm going to spend alot of $;)
I'm going for a wild guess on the springs:

Wider track=more leverage=softer effective spring rate, the opposite in the back?

stiffer rear+softer front=less understeer.

but what about corner exit traction?
(sorry, next chapter)

fascinating!

[TeamM3]

and what might you then do with the adjustable front bar?

[AC]

BLING!.... extra stiff=less body roll=best contact patch! :thumbup:

[TeamM3]

well, there's a bit more to it than that but you're on the right track

the whole purpose of leading down that long winding path was for you to get a taste of the thinking process

good luck

[AC]

:thumbup: :beerchug: