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Beetle specs for engineering
The Stump - October 23rd, 2008 at 05:37 PM

Guys,
Need help - my dream is smashed I think. :-(

Was hoping to fit to my beetle some retro Porsche Turbo wheels (would have needed wider guards).
The wheels are something along the lines of 7" and 9" by 16 - but with quite a deep dish on the back set.

Talking to the engineer today he said I would be limited to:
Track - max increase of up to 25mm over std

Tyre width cannot exceed +30% of original tyre width - which is not that much 205's perhaps.

To begin calculations I need to know what the front and rear track measurements were for a 68 Beetle semi-auto "IRS" Pan.

I also need the tare weight of said same vehicle

Anyone???

greedy53 - October 23rd, 2008 at 06:05 PM

have you got an standard wheel and tyre if so out with the tape and measure

mactaylor - October 23rd, 2008 at 06:07 PM

ill go and have a measure for you mr stump, report back soon!

Bizarre - October 23rd, 2008 at 06:57 PM

I think it is more the ET of original wheels Vs what you want to put on

This will calculate what the difference is
COmpare a standar wheel against your new wheel and it will tell you how much wider the track is
http://www.1010tires.com/WheelOffsetCalculator.asp 

You need to get what the widest original wheels were

I have a document that shows 1973ish beetles having a 5 1/2 ET 26sports wheel - which is bloody wide

But a 9" is going to be a struggle.
REAL struggle

Sides - October 23rd, 2008 at 07:06 PM

Seems this ET thing is a popular subject at the moment !!!

Hey Bizarre, any chance of getting a copy/scan of that doc you have on 73's ???

Bizarre - October 23rd, 2008 at 08:58 PM

Here you go

Joel - October 23rd, 2008 at 08:59 PM

u can go over those guidelines it just means u have to get it engineer certified

i was in that boat when i ran my 18s
the were larger than what was permitted but if i wanted to keep them i had to get an engineer to check them out and certify them

mactaylor - October 24th, 2008 at 06:10 AM

just measured the rear track of a 76 its 1537mm centre to centre "track" will measure the front today at work.

Sides - October 24th, 2008 at 06:37 AM

On Samba I found some scans from a US spec 1970 Owners Manual...which looks to be a BJ IRS with 1600 engine.

http://www.thesamba.com/vw/archives/manuals/70beetle.php 

It quotes there 1310mm track front and 1350mm track rear with 15x4J rims. Page 62. There's no detail on ET, but other info I have says a standard 4 stud steel wheel is ET34.

Don't know if I trust those numbers though, since I'm sure the track at the front is actually wider than at the rear (they're also a lot different than what mactaylor's rear track measurement)

The Stump - October 24th, 2008 at 05:22 PM

Quote:
Originally posted by Joel
u can go over those guidelines it just means u have to get it engineer certified

i was in that boat when i ran my 18s
the were larger than what was permitted but if i wanted to keep them i had to get an engineer to check them out and certify them


Hey Joel - yeah I had hoped for this outcome, but I have just had a talk to the engineer before I originally posted, and his word was:
no more than 25mm increase in track - final!!!

I will persist though - the rears are actually 9.5 inches inner bead to inner bead and on measuring about an offset of -3 (i.e. from centerline further IN toward the car!).... But the dish on these suckers is absolutely delishious!

Track is one thing - I can fudge my way around that by fabricating some narrower trailing arms and getting shorter half shafts made up. But the killer may be on the actual wheel width. Rules say that tyre width can only be increased by up to 30% (which allows a 205 - would be too much of a stretch on the wheels I think. I could give it a try but the engineer will definately not approve that)

Other rules rolling diameter can be reduced by up to 15% (I think) but only increased by 3% (I'll have to check that).

I have read the Aussie VW mag with the article on Dino's beast running 18x9 budnicks - I will try to contact him (Is he flintstones on this forum?)

All others - many thanks for your feedback guys. I will let you know how I progress.

Cheers.

1303Steve - October 24th, 2008 at 10:48 PM

Hi

I'm not sure about the ACT but in NSW for PRE 1973 cars it goes on the finished weight of the car.

Most Porsche wheels will actually decrease track. If the ACT equivalent of the RTA is anything like ours they most likely have the wrong track info anyway, ask your engineer to supply the official numbers.

Steve

The Stump - October 28th, 2008 at 03:35 PM

Quote:
Originally posted by 1303Steve
Hi

I'm not sure about the ACT but in NSW for PRE 1973 cars it goes on the finished weight of the car.

Most Porsche wheels will actually decrease track. If the ACT equivalent of the RTA is anything like ours they most likely have the wrong track info anyway, ask your engineer to supply the official numbers.

Steve


Ha ha - so in NSW, to get my Beetle registered with the wheels I want I would have to:

Narrow the front beam - to ensure not exceeding 25mm extra track

Fabricate custom rear trailing arms and shortened half shafts - to ensure not exceeding 25mm extra track

BUT! I can do that AND use the 9.5's I have for the rear - IF I add a shitload of weight to the car (around 500kg!)

I am thinking that it would almost be easier to start with a Porsche 911 shell and build it to accept a Beetle body on top.:!:

The Stump - October 28th, 2008 at 03:39 PM

I have to say -

Why only 25mm???

I could understand it for FWD applications, but surely on RWD it would be limited by the amount of "over engineering" that had been designed into the rear bearings by the manufacturer - so for a Porsche as example, you are talking a fair bit wider.

So the 25mm is obviously an arbitrary number plucked out of some f*kwits arse! :grind:

They are slowly clamping down on every aspect of modifying - and killing off a culture. We would not have Hot Rods if they were so strict from the beginning! They want us all to drive the same shaped cars with the same wheels, painted the same colour, with the same performance and fuel usage.... (snoring sound)...

76bug - October 28th, 2008 at 03:59 PM

could u engineer it as an ICV?

Flintstones - October 28th, 2008 at 06:31 PM

ICV...you've got no hope then :o)
Understanding the rules will kill you before you've even started.

Cheers
D

1303Steve - October 28th, 2008 at 10:59 PM

Hi

My understanding is that is if you widen or narrow your track mechanically, say narrow beam or fit wider trailing arms etc you have to subtract or add the widening or narrowing from your final allowed track.

A 1500 bug used 4x15 ET 40 wheels, so if you widen your track to the allowed 12 mm per side your 7 inch front wheels would need to have an ET of 28, but please ask your engineer to give you the specs that they work on

I expect my new bug to weigh in at 1001 kg and as its on a pre 1973 chassis I'm allowed to up to 8 inch wheels.

Steve

Stock Beetle wheel sizes,

Bizarre - October 29th, 2008 at 06:48 AM

Quote:
Originally posted by 1303Steve
I expect my new bug to weigh in at 1001 kg



How very convienent :lol:

Sides - October 29th, 2008 at 07:28 AM

Quote:
Originally posted by 1303Steve
... widen your track to the allowed 12 mm per side your 7 inch front wheels would need to have an ET of 28, but please ask your engineer to give you the specs that they work on ...


Lines up with what I've been told - however because there was also that ET 34.5 wheel you could ge anywhere between ET40 and ET22.5.

I've never heard of a Porsche 16x9" rim with an ET that small, but they could be out there. ET36 is pretty common for 6" rims, and ET 23.3 and 23 is common for 7"s (narrow body 911's used 6" ET36 on the front and 7" ET23 on the rear, which makes them perfect for Beetles)

1303Steve - October 29th, 2008 at 08:45 AM

Hi

Good point, that's correct you also deduct the 12mm ET as well. To keep the rego people happy maybe 3 piece wheels would be needed, that way the track can be adjusted to keep everyone happy.

The 34 ET wheels are from a 1977 model bug, 4 digits in the middle part of the chassis number means its a post 1970 chassis number.

Steve

The Stump - October 29th, 2008 at 09:04 AM

Steve,
Many thanks for those snippets of information - they will be most useful!

Ha ha - the wheels I was hoping to use are a 3 piece retro BBS rim (E50 centers) from a 76 Porsche Turbo!

Hahahahahahaha...

I measured them up:
Fronts are - 16x8 et 3 (i.e. center line of wheel plus 3mm toward the outer edge of rim [not sure if that is et of -3 or +3])

Rears are - 16x9.5 et -14 (i.e. center line of wheel plus 14mm toward INNER edge of rim!)... But they have great dish!

:crazy:

1303Steve - October 29th, 2008 at 09:09 AM

Hi Stuart

No worries, maybe you could have some new outers made up, but you would loose that deep dish look.

Steve

Sides - October 29th, 2008 at 11:21 AM

Best bet I reckon is explain in detail beforehand to your engineer what you want to do, then get the same guy to sign-off on it afterwards.

Has worked well for me with all my mods so far - seats, bases, harnesses, cage, wheels and brakes.

:tu: