caster ? overcaster ? need advice !

[pegase747]

Hi to all,

Ok I've just introduced myself in the general forum, you can see the thread link on my signature.

So now I wish to ask a technical question to the suspensions/axle/handling/alignement specialists here.

I have an Alpina B3 2.7, so the original suspension set has the following feature :

the front strut upper bearing is offset in 2 axis, the strut top attachement is then moved toward inside the car and towards the back. All in all it adds some negative camber, and some positive caster
here is a picture to illustrate :

A is the added negative camber.
B is the added positive caster.
C's are the original strut axis.





The Alpina factory specs are as follow, with Alpina springs fitted and original Bilstein shocks :

Camber : -2 +/- 0.3
Caster : +9.1 +/- 0.3

This is basically what you get on an original M3 with offset CAB's, as far as caster is concerned.

I plan to install Powerflex CAB centered or offset, so my question is :

How much more degres of caster I will get if I install offset CAB ??


It is important to know that because due to the caster induced by the upper strut mount, I may be overcaster if I put offset CAB.

If anyone has a before/after caster value for the installation of offset CAB or THR eyeballs that probably would help.

What is the risk ? The wheel will probably not touch the inner well, because as much as the offset CAB will move the wheel a tad forward, the offset strut mount are slightly moving the wheel aft.

So the main concern I have is overcaster, will the car will be over stable, or is that ok ? will it apply to much force on the steering system ( I have power steering ). I drive the car anywhere, small muntain roads, highway, normal street driving, never race...

If it is way over caster, then I will go for centered and keep original specs, now maybe the increase is not that big, and fitting offset is ok.

I hope someone can help.

Cheers / Pierre

[E30-323ti]

It is probably more a case of "do you like it? or not?"

Does it suit your style of driving and/or the roads/tracks you use??

The other way to look at it is, Alpina modded the E30 to what they thought was best, if you think you know better then go ahead change it.

Not very constructive sorry.

[pegase747]

well

Hi there,

well, whatever Alpina did on the car, the CAB are still the original piece of shitty rubber that you find on any E30, as well as the rear shock mounts.
The question is not if I like it or not.

Question is that I don't want to have a fuzzy or dangerous handling if I do something wrong with the caster.

I love the way it handles with the original geometry ( centered CAB ), but as I already have the Powerflex offset bushings at home, I wanted to know if I can install them, or it would be a safer option to install the centered one, to keep original Alpina geometry.
In this case I have to buy the cenetered Powerflex bushings.

Anyone got more idea ? I just would like advise. what do the race boys think about that matter ? is more than 9.3 degres caster is safe ??

thanks / Pierre

[pegase747]

Really nobody knows ???

Come on give me a help here !!
Pierre

[wazzu70]

As I am sure you already know increasing caster makes the car more stable at high speeds at the expense of low speed turning effort (at the wheel). Positive caster uses the cars weight to return the wheels to their center position (let go of the steering wheel and it want to return to a center position). The more caster you introduce to the geometry the steering will try to recenter itself at lower speeds. I think this would be a bad situation for you, especially since not all your driving is done at faster speeds where more caster would be helpful. Im thinking the less is more addage is going to apply to you here.

I would just go with the centered LCA bushing for this reason. An other option is to put in the offset bushings since you have them and see if you like it or not. It never hurts to try, however, just be aware of the potential dangers.

[pegase747]

thanks

Hi Wazzu,

well that was the plan I had anyway.
I guess the offset bushings will be a bit of too much caster for the car.
The offset upper struts ae doing a good job and the car is really stable at high speed.

Also the upper strut will be replaced as well as the Bilsteins quite soon, so I just have to find some good Centered CAB, I was leaning towards the powerflex centered bushings because they are so easy to install.

Many thanks for your answer !
cheers / Pierre

[wazzu70]

No problem, glad to help. report back how the additional caster works out if you install the other ones to see what its like. I would be curious to know. Also do you know if those Alpina upper strut mounts are still available? Looks like a slick thing for the average road warrior looking for a little performance.

[pegase747]

Alpina Struts

Hi Wazzu,

well you can get those Alpina struts I guess.
Since I have a genuine Alpina car with a serial number, I can get ALL the parts for my car from any official Alpina dealer in Germany.

Now some Alpina parts are available to everybody, and I guess you can get the struts and many other Alpina stuff through Walloth & nesch in Germany. They do speak english. They don't carry E30 parts on the site, but they actually can provide E30 Alpina parts, at a price...
www.wallothnesch.com

the part numbers for the strut are :
31 31 141 for the LH side
31 31 142 for the RH side
31 31 143 for the set of both LH & RH.

Back to the caster, yes those strut bearings are great, increasing caster and also camber at the same time, without moving much the wheels within the wheel arches.

Hope that helps.

Cheers / Pierre

[Andreas]

Hey pegase747,

I'd bet some money that you didn't think that you would find a fellow Alpina B3 2.7 (12 of 15) owner in South Africa who can answer your question.



The Alpina B3 is my track toy and has seen a few suspension upgrades, the last of which was E30 M3 offset CABs. Unfortunately I put them in at the time I was finishing a rebuild and since the car was standing for almost 2 years I didn't exactly get a before / after feeling.







The car handles awesomely and is always one of the fastest cornering cars on a track day. I had a full interior and semi slicks and was roughly only 1-2 seconds slower than stripped 2.7 E30s with full slicks and adjustable camber and roll cages (a big handling improver).

I drive without power steering. I don't understand wazzu70's concerns about slow speed driving, I certainly had no problems whatsoever, maybe he can explain in more detail what he means and then I can say if any mentioned behaviour occured on my car or not.

I don't know if those Powerflex bushes you refer to are solid polyurethane or rubber. A word of warning : Our E30s (even Alpinas) are not Formula 1 cars, the suspension is not built with 100% accuracy and when suspension components move up and down they need some "play" as offered by rubber. Now poly bushes do not flex to accomodate your suspension's little inaccuracies and your suspension will "load up" and be very resistant to moving (bad for handling). Something "has to give" and (luckily) it is usually the poly bush that breaks - I've seen quite a few threads of people saying that this or that poly bush is crap.

[Axxe]

Just put the offset bushings in.

[wazzu70]

Andreas, since I have never driven a car with mor positive caster I was merely working off the definition of how positive caster will affect a vehicle. If you have run them without problems then, like I mentioned he should give them a try. Your application is obviously for the higher speed driving for which the added caster is beneficial, while he was just going to use the car for spirited driving.

I didnt try and make it sound like something catastrophic was going to happen to the car if theats the impression you got. I just wanted him to be aware that at slower speeds the positive caster will require more steering effort, and the suspension will center faster than it currently does.

How much more force will be required and how much faster the car will center is unkown.

[pegase747]

Well...

Hello to all,

Andreas, you're from South Africa, that's great ! Yes that was a surprise. I've never been there in South Africa, but I used to handle aircrafts from "Suid Afrikaanse Lugdiens" while I was still in Paris, and really enjoyed springboks rolling "r" accent..
Now I work in japan, so not anymore...

Anyway, what do you mean your Alpina B3 is #12 of 15 ???? there has been 15 imported in SA ?
Thanks for your informations, I am glad to know that the M3 offset bushing geometry is OK on the Alpina with its offset strut bearings. I was'nt too worry about the position of the wheel in the wheel arch, but more about the excessive caster...
Now you say it makes faster cornering, I am not surprised, already the Alpina by itself is a good cornering car...

Power steering I have it and want to keep it because it feels great in my opinion. Actually I have an E36 rack waiting to be fitted on the car.

About the powerflex bushings, yes they are made of polyurethane but they have a design that makes them more like a bearing, there is one part ( purple ) that slide on the aft side bit of the control arm, and one part ( black ) which is inserted into the bracket bolted on the car frame.
The purple part is lubricated and will rotate into the black fixed part, so the suspension up/down movement will not resist, they will just act as an inner and outer parts of a bearing.
On the other way, they will stop the L/R side movement of the control arm, enabling more accuracy of the movements of one wheel toward another during steering, and sideload forces.

I also read a few stories about poly bushes braking, but we allways hear bad stories, not much the good ones. I guess a lot of people have no problemes with their Powerflex bushings. Depends how you drive too I guess. I am not racing and am not asking so much to my car. I just like to have more accurate handling. Now I also thought about the Treehouse Racing eyeball arm, but they may be a bit arsh...

Wazzu,
right I may give it a try and see it is going after a while...I am not too worry about them braking, and was more affraid of the extra caster anyway.

well we'll see and I will let you know...

Cheers / thanks // Pierre

[Andreas]

pegase747, BMW SA built 15 Alpina B3s, probably some license agreement, by converting a normal 2-door 325i. The engine is 2.7 with Alpina cam and computer box & chip, 16 inch Alpina rims (back wider than front), Alpina front spoiler and rubber boot spoiler, thicker anti-roll bars, Bilstein shocks (don't know about springs), Alpina offset strut bearings, 3.91 diff, Alpina / Momo steering wheel, Alpina gear knob and full leather interior with recaro seats.

Now after all that, can you believe that they left the standard 325 brakes, i.e. 260mm 4-stud with no ABS.

Does yours have bigger Alpina brakes and / or ABS ? What else does yours have that my SA edition does not have ?

By the way, the front tyre does rub against the front of the wheel well. The plastic cover that holds the brake cooling duct has a hole worn through it. Funnily I only heard it rub in the morning for a short period while everything was cold. It is a minor rubbing and I would not worry about it.

Here are two pics of my new brakes.

[pegase747]

My Alpina

Hi Andreas,

well your Alpina has been built like the UK models with Sytner I guess, that means Alpina got some agreements with some dealers to install Alpina equipement, and make them genuine Alpinas. Do you have the plate certifiying your car as genuine ? In case I guess you have a genuine Alpina, since it has been approved by Buchloe ( Alpina factory in Germany ).
I know also that SA had the BMW model 335i E30, which has been devellopped together with Alpina, with the M30 engine.

My Alpina is #224 of 257 models builts. There has been 101 Model B3 2.7 builts. Mine has not been fitted with a catalyst at the factory, and then has ( had... ) 210 HP like the model C2. I don't know if it is including UK and SA modells.

So back to my car.
It has been built by Alpina factory and have all the Alpina goodies :

-97 liters total fuel quantities with the extra Aluminium in the trunk.
-bilsteins front and rear shocks.
-rear Alpina sway bar, adjustable to 3 positions.
-Alpina progressive springs.
-Alpina front 296mm brakes ( bigger than the original E30 M3 )
-7x16 & 8x16 front and rear Alpina wheels.
-front and rear Alpina spoiler and rubber boot.
-Recaro seats in Alpina cloth colors & alpina cloth on door trim.
-Alpina/momo 4 branch sport wheel.
-Alpina/VDO digital instruments in the center/left air outlet exhaust grill.
-ABS is there and was normally fitted on ALL 325i in Europe I believe.
-Alpina cluster with orange hands, bigger fual gage, tachometer 260km/h.
-wood plated dashboard, glovebox, gearknob surrounding trim.
-Alpina model plate in the hood ( my cert. of reg. is Alpina, and BMW is never mentionned ).
-3.73 LSD at the back. ( are you sure you have a 3.91 ??? )
-custom made Stainless exhaust system from Alpina header to the exhaust tip.

few pictures for you :

























do you have the Alpina exhaust header ?? ( without you may lose a lot of power... )

Well that is about it.

Your new brakes look really good. What diameter are those disks ????

Cheers / Pierre

[Andreas]

Hi pegase747,

Yes I also have one of those plates certifiying my car as genuine. I am the third owner of the car and one of the previous owners scratched away most of the plate's writing in the center - maybe they put the first owner's name on the plate in SA and this didn't suit the second owner. However, my chasis tag is BMW and I see yours is Alpina.

Non of my original anti-roll bars were adjustable. I am sure about the 3.91 diff, I even replaced it with a 4.44 LSD.

BMW SA built a 333i that used the 3.2L from the old 733i. The 333i had the 296mm brakes and that readout in the aircon vent. The 333i had a dogleg gearbox and only about 200 (not 100% sure) were made. I did test drive a 333i once and it seemed a lot less lively than the B3 2.7

As far as the exhaust goes, I think it had the standard 325i cast iron exhaust manifold. Due to rust, I had the complete system replaced by a local tuner's exhaust, then turbocharged it, then back to NA with yet another exhaust (sold the previous system).

Currently I am pursuing a 15 year old dream and converting the intake to an individual throttle body system with a fully programmable stand-alone system.

Seeing how pristine and pure your Alpina is, you might not agree with my project of converting it to a full race car with virtually the whole body incl. doors and roof being made out of carbon fiber and hopefully weighing less than 950kg.

once upon a time


and now




here is a pic of the throttle bodies