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DonPeaslee
05-10-2006, 02:07 PM
We run a much modified '80 Rabbit in hillclimbs. It uses larger Audi front wheel bearings. They are a stiff press fit in the uprights, and the axle nut is tightened in excess of 300 lbs, a practice advised by a local VW race shop to avoid bearing failures in the '84 GTI I was running in ITB five years ago.

Last year we installed new bearings as above, went to a climb, and had tech inspection note that we had looseness (were allowed to run anyway). We subsequently installed new bearings of a different make. One of them appeared a tad loose. We jumped on the extension pipe over the head bar some more, it aaparently tightened up, and we ran several more events with no problems.

Last week we did a pre-season session on an alignment rack, and found looseness again, both wheels. The nuts are tight. We are nonplussed; the car has all of 25 runs on it, no offs, about 100 racing miles. Has anyone else experienced this problem? These bearings are tighter than the proverbial bull's rump. WHAT is going on here? We're mystified.

P.S. When originally developed on an engine dyno this CIS motor ran a fairly consisent 12.5 fuel/air ratio. Now it's running at 13-15, which is too lean. The system pressure was 80psi, with the control pressure sitting as high as 70. I am assuming that the control pressure regulator is degrading in some way. Adding mild pressure to the CPR vent causes the control pressure to rise 5psi, as opposed to reducing, which I expected after perusing the Bosch book. Comments on both these issues are much welcomed.

racer_tim
05-10-2006, 05:47 PM
Regarding the front wheel bearings, and the amount of torque that your on them. I've heard both sides of the argument for either "stock" torque, or jump on the end of a breaker with a 4' pipe extension.

I used to use the 4' pipe extension on the 3/4" breaker bar, but was told that this too would also lead to bearing failures since you were "crushing" the bearing with the excessive torque.

So, I've gone back to the "Stock" torque of the axle nut, and simple swap out the hubs/bearings/ and 1/2 shaft assemblies every year.

Put new bearing in the hubs, and use the spares that you dragged around all last year as spares on the car. Same with the 1/2 shafts.

I've only had 1 CV failure in over 8 years of racing a locked front diff, using the above "normal" maint practices.


Can't help with the CIS stuff. If it's not broke, I don't fix it.

eimc
05-10-2006, 07:07 PM
On the front wheel bearings we only use german bearings( China etc are loose to begin with and don't usually last more than a couple of hundred miles of street use) You can also carefully pry out the seals and install a better grease(it looks like they pack these with vaseline & not very much) and carefully reinstall the seals. We torque them to stock spects plus 1/4 turn. As far as the CIS goes we usually modify the warm up reg and adjust it to what we need to what enging we are running. regards Paul

racer14itc
05-10-2006, 08:22 PM
The failure mode of the warm-up regulator is to result in the control pressure equalizing to the system pressure. Install a new warm-up regulator and it should solve your problem.

On the wheel bearings/hubs, I use the best hubs & bearings I can find. I use a 3' breaker bar and torque them tight! After 4-5 race weekends I pull the hubs & bearings out of the carrier. To test them I throw them in the closest lake or pond. If they float, then I keep them as spares. Otherwise, it's time for new bearings and hubs. :cavallo:

I don't repack the grease in the wheel bearings. When inspecting them after removing them (and before performing the water density test), occasionally the bearings have some wear but most of the time they look fine.

Doing this regularly, I haven&#39;t had a bearing or hub failure in 11 years of racing <sound of wood knocking>

MC

:024:

Ryan Williams
05-10-2006, 09:32 PM
Check the small circular "filter screen" on the inlet port of the CPR. If this filter screen get clogged, then the Control Pressure is wrong.

With the factory setup, the CPR should create about 58 psi when the engine is completely hot. However this amount of Control Pressure is too high for an engine under race conditions at WOT.

If your rules allow a modification of the CPR, then make it manually adjustable so you can set the Control Pressure to about 48 to 50 psi.

Once you disassemble a CPR, then you will quickly understand how to make it adjustable.

Cheers, Ryan.

eimc
05-11-2006, 07:08 PM
When I spoke of packing the front bearings I meant new bearings before installing , not REPACKING USED BEARINGS. Cheers Paul PS I run an entire season with no wheel bearing failure or play etc.

67ITB
05-12-2006, 12:09 PM
We check and tighten the fronts every time the car sets a wheel on the track.
Some times there is some take up on them, sometimes nothing.
We change the bearings every 6 events. And use only quality German bearing (can’t remember the name, but I think they come in a blue and red or orange box)

I have actually broken a Snap On 1/2 breaker bar tightening them. I am FAT, and use the calibrated beer belly :birra: to really get them tight. But using this method I have never had a failure.(knock on wood)

ryotko
05-12-2006, 03:17 PM
On the front wheel bearings we only use german bearings( China etc are loose to begin with and don&#39;t usually last more than a couple of hundred miles of street use) You can also carefully pry out the seals and install a better grease(it looks like they pack these with vaseline & not very much) and carefully reinstall the seals. We torque them to stock spects plus 1/4 turn. As far as the CIS goes we usually modify the warm up reg and adjust it to what we need to what enging we are running. regards Paul
[/b]

Paul,

Where do you guys find German bearings? I looked all over and wound up with SKF parts made in Italy. The local dealer didn&#39;t even have them in stock (guess these cars are considered old or something) and were unable to tell where they were manufactured.

I already pressed one side in, I&#39;ll do the other side Sat. morning, so I&#39;m stuck with them but I would have preferred Deutsche parts.

Anyone have experience with Italian SKF bearings? The seemed fine but I&#39;m all ears.
Thanks,
Bob

msogren
05-12-2006, 08:54 PM
You might try for "Timkin" bearings They last longer. Autozone handles them for me. Not all "dubs are covered tho, but I think that the small ones are covered . The Fag(OE) and SKS are made world wide. Sometimes the outer race is German and the inner is Brazil or Italy. They is a possabilty of overtightening maybe if the hub came loose once or the axle has a strange flange.

RE CIS&#39; I raced this for quite some time. (still do)The control pressure determines how easy the pancake door opens . Less pressure and the the pancake opens very easy, IE cold run .
It will go quite a bit faster if you hang the cp regulator on the core support, unplug the heater wire and keep as cool as feasable. This will require leaning the warm run mixture , maybe one turn before it is not too rich. It will definitly go faster. . Wire the cold start to the starter wire, if the thermo time stuff fails to work.
I switch the fuel pump direct to an old rear defog switch)30amp) to direct control the pump, without a relay. I have found that relays often dont like the vibrations involved in racing, esp ice racing or rally.
Also this takes care of the rev limit.( the computer opens the ground side of the fuel relay)
I know that many race cars have many relays that work fine. I just like to keep the race cars simple and easy to diog porblems.
Take some time to balance test the injectors., and the fuel box.
Mike Ogren

DonPeaslee
05-16-2006, 07:21 PM
I&#39;d like to thank everyone for their thoughts on the two problems outlined. Here&#39;s what has happened:

After my insisting that the bearing nuts were super-tight, we checked them. One was at about 60#! The other was tighter, but.... . Most embarrasing. The nuts were removed, cleaned up, and reinstalled with blue Loctite. We kept tightening and trying. One came in good at 200# plus. The other required 300#; maybe more. Tools were a 1/2" head bar and 4&#39; of pipe. The bearings, installed last year, were made by FAG. We will now check bearings every couple of climbs!

As for the fuel/air ratio, a local race shop told me to drill and tap the steel plug on the front of the CPR so that it could be jacked a ways up out of its hole. They had the right idea, but the wrong direction. Pulling out made the CPR stop working at all, with control pressure being the same as system pressure. At that point all we could do was try the other direction, pushing the plug back in with a c-clamp. The CPR started working again at its original insertion point- and further push resulted in the control pressure heading right on down! I wonder if the two CPR&#39;s I threw out when racing ITB could have been fixed this way? Sure woulda been cheaper. We are now at 42# (which we hope equals 12.5/1) and plan to measure/adjust pressures between runs at the first climb of the year, coming up this weekend at Mt. Ascutney, Vermont. The course is 3.2 miles, about 40 turns. Ryan, we have taken careful note of your 48-50# recommendation and will observe response and performance in that light. As for "quickly understanding" after opening a CPR: didn&#39;t try. In salty, corrosive winter NE the CPR screws don&#39;t want to turn to get the thing apart. And I probably wouldn&#39;t have understood anyway.

Further comments:

racer_tim: only one CV in 8 years with a locked diff? Wow. Driving around the paddock must be interesting.

michael ogren: my brain trust wants to concentrate on adjusting the plug for control pressure, rather than hanging the CPR in the breeze, etc. He wants the engine heat to modulate things as the Bosch guys intended, plus using a heated strip. The idea is to run like stock, just richer. We run 1000&#39; elevation changes in 2 plus minutes, and base temperatures varying from 40F to 85F. We won&#39;t even get into the setups required to successfully run on super-high cambered uphill asphalt surfaces! As for using big switches instead of relays, I&#39;m with you.

Again, thank you ALL for the help. Now, if flooded, sodden NE will just drain down well enough for us to race this weekend... !

Don Peaslee

Bill Miller
05-17-2006, 11:03 AM
It&#39;s not really a good idea to re-use those axle nuts. In fact I think VW suggests that you don&#39;t. There&#39;s really no need for the Locktite, if you crank them down enough. But, if you&#39;re going to use it, use the Red, not the Blue.

mgyip
05-17-2006, 01:01 PM
It&#39;s not really a good idea to re-use those axle nuts. In fact I think VW suggests that you don&#39;t. [/b]

That&#39;s true but no one follows that to the letter - it&#39;s like head bolts that are one-use (2 or 3 times). The biggest problem with VW front hubs is that no one at VW was bright enough to install some sort of positive stop for the nuts once they&#39;re tightened like they do on Hondas.

On the A2, I change hubs annually wether I need to or not. In 9 years, I&#39;ve broken 2 hubs due to my own negligence. - shame on me :bash_1_:

racer_tim
05-17-2006, 07:34 PM
Further comments:

racer_tim: only one CV in 8 years with a locked diff? Wow. Driving around the paddock must be interesting.

Don Peaslee
[/b]

Yes Don, driving around the paddock is not that difficult, as long as you don&#39;t have to make 90 degree turns. :D

JamesB
05-18-2006, 08:21 AM
Exactly as long as you keep everyting as a sweeper or perfect the 72 point turn your just fine. However, once I broke 2nd gear in MARRS1 I chose to install a diff on the new trans since it had to be cracked open and inspected anyway.