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Christopher Schimke Mon Nov 20, 2006 11:56 pm

r39o wrote: Plus in order to keep the scrub radius right (so I am told) you want to run an ET in the mid to low 20's for those 7.5 rims. GoWesty uses ET23 on their 16x7.5



The stock 30mm offset wheels put the scrub radius right near zero and the stock 39mm offset wheels put the scrub radius around negative 9mm.

Provided the wheel offset doesn't change, the width of that wheel will have no effect on scrub radius. In other words, a 14x6 et30 will have the same scrub raduis as a 16x7.5 et30. A 16x7.5 et23 wheel will affect the scrub radius and not in a good way.

Scrub radius should be kept close to zero or negative. Positive scrub radius can cause instability under braking and increases steering effort. To what degree depends on how far positive the scrub radius is. Increased positive scrub radius has much greater effect on suspension dynamics than increased negative scrub radius.

Would I run a 7.5 et27 wheel? Yes I would but I would be happier with a 30-32mm offset. Not that it means much.

r39o Tue Nov 21, 2006 12:08 am

Chris,

Then tell me why 3 sources are running less than ET30?

Also, how do you know the Steering Axis Inclination ( or whatever it is called! ) to be able to tell what the Scrub Radii are for various offsets?

( Come to think about it, tire diameter also affects the Scrub Radius..... )

I am VERY curious as there is some reason why the factory used a different ET for different width wheels.

What is the magic here?

-W

r39o Tue Nov 21, 2006 12:19 am

pete000 wrote: I think the Vanagon can hold some really wide tires on back. I tried some 10's and they fit, but the opening door is the deciding factor.
In order to fit wider tires and not hit the door, you can modify the U thingie on the slider on the body so it makes the door stick out more. Modify means to cut it and weld an extension. I seen it done already. No worries there. You may even be able to buy modded ones from Germany.

Ericthenorse Tue Nov 21, 2006 12:32 am

In order to get the same clearence on the inside of the rim, you have to change the offset... if your wheel is already close to the suspension, and you want to add a wheel that is 1 inch wider, your ET has to change by about 13mm to keep the same amount of clearence....


OK... my turn to ad....

MBZ wheels... 16x7 ET (will look at wheels and post)... Spacers not needed, but added 10mm anyway.... Used stock lugs...center cap does not fit



MBZ SLK wheels 17x8.5 ET ? 10mm spacers front and rear(only added in rear to keep thingss balanced) converted to long front studs and longer rear studs... Center cap fits on...

Christopher Schimke Tue Nov 21, 2006 10:48 am

r39o wrote: Then tell me why 3 sources are running less than ET30?

Probably for a couple of reasons. Among them and not necessarily in order:
Lack of knowledge
Money
Ease of installation
Lack of available exact fit wheels

Many wheel and tire vendors take very little consideration of making sure that you maintain proper wheel to suspension geometry when installing a new set of wheels. If it fits without rubbing, they sell it.

What Markus says about his zero offset Ronal wheels supports this.

[email protected] wrote: These are actually wheels that Ronal pumped out for some special edition GM Tahoes, The center caps actually have GM stamped on the inside them. I don't think they fly off the shelf so Ronal drills another set of holes (as you can't see whats unerneath that cap) in this case 5x112.

The wheels "fit" but not ideally, they stick out too far in the front and rub a little at the slider. I originally tried 225-60-16's on them and had rubbing issues at the top of the wheel wells, the slider rubbed as well.

And yet, apparenty his van goes down the road very well. Go figure!

r39o wrote: Also, how do you know the Steering Axis Inclination ( or whatever it is called! ) to be able to tell what the Scrub Radii are for various offsets?

It has to be measured. At ride height, a line is drawn through the kingpin axis (centerline of upper and lower ball joints. aka Steering Axis Inclination). A line is also drawn through the centerline of the tire. The distance between these two lines at ground level is the scrub radius. If a particular scrub radius is zero, adding negative offset will also add negative scrub radius. Adding positive offset will in turn add positive scrub radius. For example, adding 5mm negative offset to a vehicle with zero scrub radius changes the scrub radius to 5mm negative.

On a Vanagon, because the scrub radius is zero with a 30mm offset wheel and a stock height tire, it's easy to figure your scrub radius for any given offset.

r39o wrote: ( Come to think about it, tire diameter also affects the Scrub Radius..... )

Yes, it does, but unless you are radically changing the diameter of the tire, the changes are very minimal.

By the way, the scrub radius numbers that I stated in the previous post were calculated using a 25.5" tall tire.

r39o wrote: I am VERY curious as there is some reason why the factory used a different ET for different width wheels.

What is the magic here?

In my opinion, there is no magic. Just like most of the wheel vendors in the world, if it fits without rubbing, run it. But if you want it to be as accurate as possible, it will take more work to acheive that. Your choice!

Christopher Schimke Tue Nov 21, 2006 11:00 am

Thank you to all of you who have taken the time to add to this thread.

This is a bit like the brickuard thread except that I hope this one includes as much information about installing wheels onto Vanagons as is possible. Lug, stud, center bore, center cap, clearance and any other issues relating to the installation of wheels on a vanagon should be included here. The more information that we have in one place, the easier and quicker it will be for anyone to look up the information.

Even if all we documented was what offsets work (including any spacers necessary) with what widths, that narrows the fitment concerns down quite a bit.

Thanks again guys!

r39o Tue Nov 21, 2006 12:04 pm

Chris,

So you measured the Steering Axis Inclination angle, then. Answer is?

Also, changing offset by X does not change the Scrub Radius by X. It will do so, if and only if, the Included Angle is equal to the Steering Axis Inclination or Camber is ZERO. We don't run zero camber.

The reason for all this is to choose a good ET. Fine. Good ET means that not only does it fit with out rubbing, but we maintain the steering geometry as intended by the factory. That should, hopefully, keep the bearing loading just as the factory intended (or better?) I won't mention other changes that should be done based on changing wheel widths and so on.

I know very well that any offset that doesn't rub will allow the van to go down the road. But, for example, if we get the Scrub radius wrong (positive) and there is a brake failure (dual diagonal system fault) the steering to a stop could be hard, as an example. Or worse cause an accident. Also, I don't want the tires to wear funny too. I just hope I am not asking too much!

*IF* the factory used all the same offset for the two wheels it offered, ET would not be a question. But going to a 7+ inch wide rim is a significant difference from the stock sizes of 5.5 ET39 and the 6.0 ET30

My fingers are itching to call the wheel place to get the bits to mount my wheels. ...... I have been reading for hours on this stuff. It is getting time to deal with it.

I also do strongly hope I have not missed something important and not be like a broken record.

Christopher Schimke Tue Nov 21, 2006 1:33 pm

r39o wrote: So you measured the Steering Axis Inclination angle, then. Answer is?

Oh, yes, sorry, I thought I included that. The SAI on a Vanagon is 16. That's a pretty steep angle when you consider that most rear wheel drive vehicles are in the 6-10 range. 16 is up there with the front wheel drive, MacPherson strut cars who usually run negative scrub radii. Mostly because of torque steer but also because of the high SAI.

r39o wrote: Also, changing offset by X does not change the Scrub Radius by X. It will do so, if and only if, the Included Angle is equal to the Steering Axis Inclination or Camber is ZERO. We don't run zero camber.

Actually, the camber should be at 0 (+ or - ) empty. When I took the measurments for the scrub radius, they were taken using 0 camber. But you are right, changing the camber alters the scrub radius values.

r39o wrote: I know very well that any offset that doesn't rub will allow the van to go down the road. But, for example, if we get the Scrub radius wrong (positive) and there is a brake failure (dual diagonal system fault) the steering to a stop could be hard, as an example. Or worse cause an accident. Also, I don't want the tires to wear funny too. I just hope I am not asking too much!

I hope that you didn't take that the wrong way. I was not suggesting that you just install whatever fits. I meant that as a reference to the way a lot of things are done when it comes to wheel installation.

I think that you are very wise to take these things into consideration especially when you consider the consequences of getting it horribly wrong. However, I think that there is a relatively decent margin of error that one can play within and still not induce any signifcant negative safety issues. Proof of this is the huge variety of different types and configurations of suspensions among the OEMs.


r39o wrote: *IF* the factory used all the same offset for the two wheels it offered, ET would not be a question. But going to a 7+ inch wide rim is a significant difference from the stock sizes of 5.5 ET39 and the 6.0 ET30

Yes, but for the issues that we have been discussing here (scrub radius and wheel bearings), keeping the wheel offset between the factory 30-39mm maintains these values to within what the factory felt was acceptable.

It would be a very interesting comparison to drive a Vanagon with both sets of factory wheels back to back on the same vehicle taking careful note of what if any differences can be felt in the steering wheel as well as the seat of your pants. Of course they would have to have the same tires on them as well.

K58 Tue Nov 21, 2006 8:30 pm

pete000 wrote: Here are the 17 X 7 and 17 X 8's on my Carat. I am using 1" adaptors. Fit perfectly, but sliding door bairly clears the rear.

I think the Vanagon can hold some really wide tires on back. I tried some 10's and they fit, but the opening door is the deciding factor.


those wheels look like they'd make great "curb feelers" :lol:

bill89westy Wed Nov 22, 2006 11:05 am

I upgraded to the GoWesty 2.3 engine and had this wheel set installed. Excellent results all around.

Tires are Michellin 215/60R16 Hydoedge. Nice ride, excellent steering, far less reaction to side winds. No rubbing in or out of drivesways. The front tires protrud just enough to through dirt up the side so sometime in the future someone will have to craft a fender add-on for that. GoWesty includes a full set of wheel bolts and the Socket Wrench. Tire Pressure is 45 pounds. Ride is quiet. Also drive a BMW and Mercedes and now this ride is so much better.

A nice feature is the embedded VW symbol. See my web page
[url]http://www.biztek.com/k6acj/westphalia_info.htm[/url]

JoshG Wed Nov 22, 2006 1:46 pm

Here is another Porsche option:



http://www.thesamba.com/vw/forum/album_page.php?pic_id=316878

[img]http://www.thesamba.com/vw/forum/album_page.php?pic_id=316877[img]

[img]http://www.thesamba.com/vw/forum/album_page.php?pic_id=316876[/img]

The details:

Wheels are from '97 Porsche Boxster. Fronts are 16 x 6, et 50 with a 20mm adapter. Rears are 16 x 7, et 40 with a 20mm adapter.

Tires are Nokian WR SUV 215/65/16 98H.

Ride is fantastic!

(Not sure why the pictures are not appearing but they are in the gallery)

DeMinimis Wed Nov 22, 2006 3:56 pm

Loogy, hope this helps the thread.

15x7 ET23 AT Ilatia wheels
215 75R BFGs
No spacers
No rubbing
Longer studs (can't remember the length)

r39o Wed Nov 22, 2006 6:39 pm

What diameter are the VW emblems people are sticking on their other marque - other brand wheels?

camit34 Sun Nov 26, 2006 7:57 pm

Reading through the posts here, something like this would need about a 1" spacer...is that correct?


Christopher Schimke Sun Nov 26, 2006 8:22 pm

I would be more inclined to run between a 10 and 15mm spacer with those wheels. A 1" (25mm) spacer will drop your effective offset down to 20mm and push those wheels way out toward the fender lips. I know, people run 20-25mm offsets quite a bit but I just feel that you are much better off running more like 30-35mm for a number of reasons.

camit34 Sun Nov 26, 2006 11:57 pm

loogy wrote: I would be more inclined to run between a 10 and 15mm spacer with those wheels.

OK..that's not too bad. I just have this voice in my head that would have a hard time using such a large spacer (1")...Thanks!

I most likely missed it, but where do you buy spacers from...

Christopher Schimke Mon Nov 27, 2006 8:39 am

I got a note from Wellington asking me to ad his wheel and tire selection to this thread. Here's what he had to say:

Quote: I can't figure out how to post pictures on the forum, so I'll ask you to
file this. These are the wheels I'm running, CV-900 from Derek Drew. 16 x
6.5 et 30 rated at 900kg each. I always look for the negative on products
and the only thing I can complain about is the hole in the center of the
wheel is not quite big enough for a 46mm socket to fit in to remove the axle
nut, that is untill I turned down a socket, the hole measures 57.8mm at the
outer most lip. I'm running 195/65/16 Vanco 8.
Thanks Wellington

And here's a picture of the wheel:



Wellington also included a link to a good article about wheels by Derek Drew.

All About 16" Wheels and Tires And The CV-900

This article also supports the use of 30-35mm offset wheels for the Vanagon.

r39o Mon Nov 27, 2006 3:52 pm

Some good info I don't want to lose.:
http://www.thesamba.com/vw/forum/viewtopic.php?t=152971
http://www.thesamba.com/vw/forum/viewtopic.php?t=197483
http://www.thesamba.com/vw/forum/viewtopic.php?t=187265

Christopher Schimke Mon Nov 27, 2006 3:59 pm

Thanks for adding those Walt.

Christopher Schimke Thu Dec 07, 2006 11:46 am

Here's a good description of fitting 15x6 37ET 1995 Mercedes C220 wheels.

MERCEDES C220 WHEELS



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