Track FC - Weak Points?
 

Hey gang,

I was lurking around over at the Improved Touring forums (http://www.improvedtouring.com/) and they were having an interesting discussion about about structural failure points on E36 BMWs. Specifically the rear subframes which apparently have a tendency to crack. One of the comments was that as a racer you needed to know the weak points in your car and inspect them religiously.

So that got me thinking - for my FC, what should be on my list of items to really keep an eye on through the course of a season and even while at the track? I have a pre-event checklist as well as a longer one for going through the car completely at the beginning of the season. So the basic things like fresh fluids, check pads, lugs, etc are already covered.

A few basics that I always try and pay a little extra attention to:

1) Front wheel bearings and hubs - been through several sets. They just seem to like getting loose.

2) Front diff and tranny mounts.

3) Front camber plates - I have the Cusco's and have heard that there have been problems with the adjustment bolts shearing.


So, does anyone have any other suggestions?


Thanks,

-b

Good idea for an FC thread.

If this was an FD you'd just drive it couple of years and then either replace everything or set it on fire... jk :D

camber plates are a good one! we've seen/heard of many failures.

1. aluminum upper plates crack, steel bends

2. some plates put the spring load thru the bearing, which is harder on the bearing.

other than that, we really didnt have problems with the car, not like a BMW where the subframes all pulled out of the floor (it was a big deal, even street cars has this problem)

Check the outer 'tabs' that hold the rear suspension arms. I've heard of them ripping off where they attach to the subframe. Other than that these things seem pretty bullet proof, chassis wise.

I've seen the struts/shocks punch through the metal too on the BMWs. I also heard MINIs have the same problem.

Weak point.....I say the transmission synchros.

Hell, tranny issues are assumed! I think the OP is thinking about stuff that can put him into a barrier at 100mph when it fails. Structural weak points or serious mechanical parts that hold you off the ground, etc.

Yeah, pretty much I'm looking for stuff whose failure mode is sudden and that are difficult/non-obvious to inspect. Trannies are certainly a weak spot, and are difficult to inspect, but you do tend to get a bit of a warning when they are failing.

(Which reminds me that I need to change the fluid in mine before the next event. Shifting was starting to get a little chunky the last time out.)

Thanks,

-b

Is it the bearings going bad, or are the bearings going loose on the spindle?

I ask because I play with big-bearing FBs, which have the same outer wheel bearing as FC, and spindles are a wear/maintenance item. After a while the bearing is a rattle fit on the spindle, and even if you cinch the spindle nut tight, you can rock the hub around because of that play. It's noticable to the driver when they start to get bad, the car wanders a lot more on the road and at traction limits the front tires shudder, which is not a good feeling.

Good question - so far with mine it looks like mainly the bearings. (Here is the confession: ;) ) I have had a bunch of used bearings/hubs that I have been working my way through - pull, clean and repack the bearings prior to use. They seem to snug-up okay when initially installed, but slowly loosen up over time and then won't tighten up at all. The passenger side seems more finicky than the drivers.

I now have a hub with a completely fresh set of bearings and races installed, and that's the next one that will go on. So if it's a marginal spindle, I should know it soon.

Are the spindles all the same between 4 and 5 lug cars? Or between the S4 and S5? Just wondering where I need to look for a replacement set if needed.

Thanks,

-b

As far as I know, all spindles are the same. At least, 4 lug/5 lug is interchangeable. I know of plenty people running 5 lug hubs on originally 4 lug spindles.

Whether Mazda made geometry changes between S4 and S5, I will leave to The Experts. I kind of doubt it, but there's always that lingering doubt because some manufacturers diddle with the geometry constantly. (How many different spindles are there for Fox body Fords? Not even counting the SN95 options...)

That's the noticable failure mode I get. You can literally crank the spindle nut down until there is actual bearing preload, and you can still rock the hub around on the spindle. If it wasn't for all the grease, I'd try Loctite Green, the expensive stuff used for setting bearings on loose shafts. I also kind of want to try jamming shim stock in between the bearing and spindle but that seems like a lot of trouble for the benefit... assuming that it doesn't come loose and wreak havoc.

anything else guys this is a good thread

I just replaced all 4 wheel bearings on my car

I agree on the front bearings. The rears held up pretty well over all, but the fronts I changed pretty much every 6 events or so.

the tranny/diff mounts have held up just fine with the stockish power levels my car puts out, but I wasn't doing a whole lot of standing starts. I replaced them when I built the car and haven't changed them since, no need.

Camber/Caster plates have held up just fine.

I haven't observed any stress related metal fatigue type failures in my car or in any 2G cars I'll been around on track, aside from one horrible gas tank strap mounting failure which caused a nice fire. Don't know the full story on that one, might have been user error on that.

The only difference I have found is between ABS and Non-ABS spindles. I have a bunch of either kind with sensors if you need a pair.

I must be driving wrong! I've only had to tighten the bearings a couple times since I've been running the car, usually in over 100 degree weather. What kind of grease is everyone using? I use the redline synthetic cv-2 and have not had any issues....

http://www.redlineoil.com/product.aspx?pid=82&pcid=17