Wheel Fitting Help

Fitting wheels is a bit of a nightmare, we are constantly asked "I have XX wheel, what do I need to put them on?" and the simple answer is "we have no idea, but..."
Before you want to fit any wheels to a T3 you need to find out a few measurements from the wheel itself first before you even bother buying parts for them as they may not fit in the first place. see fig 1.

PCD - or Pitch Circle Diameter - you need 112mm, nothing more, nothing less if you want them to bolt directly on, if the wheels you are interested in are anything but these then you will need to buy some wheel adapters to change the PCD of the van to match the PCD of the wheel you intend to fit. the most common use of wheel adapters is for the fitment of Porsche wheels. see fig 1.

Centre bore - this is the hole in the centre of the wheel, you need it to be at least 66mm, any less and the wheel will not fit over the front bearing cover. see fig 1.

Wheel width- this is in inches, standard T3 steels are 5.5inches wide, standard alloys are 6" wide and there are some syncro wheels that are 6" wide steels also. see fig 1.

Wheel diameter - measured in inches this is the dimension from bead to bead directly across the centre of the wheel. Standard T3 wheels are 14", and a limited number of syncro models are available with 16" wheels. See fig 1.

ET - meaning "Einpresstiefe" in German, this translated as "Insertion depth", or literally translated means back spacing. ET is the measurement from the bolt face of the wheel to the centre-line of the wheel. This measurement is crucial on a T3, get it wrong and your van will not be a nice vehicle to drive and you will forever be scrubbing tyres.
On a T3 you want to achieve an ET of around 30 to 36 ish. Standard wheels drop within this range. The rear isn't usually a problem but the front is. If you dip below 30 then the further away you get the heavier your steering will become, the more likely it will be to "tram-line" meaning the van doesn't want to do anything other than go in straight lines and the inside of the tyres will scrub. Dipping below 30 a little won't really matter too much but when you get down to say ET23 then weird things happen. See fig 1.

Bolt hole - Obviously, if the wheel fittings that you intend to use are M14, meaning the outer diameter of said fitting is 14mm then you need a 14mm hole to put the bolt/stud through! This may sound silly but there are some wheels out there, especially Mercedes wheels that use 12mm wheel fittings. If you intend to use wheels that have 12mm wheel fittings then you are going to have to open up the hole to at least 14mm. see fig 1.

Wheel nuts/bolts seat types - Please be aware that there are 2 types of wheel nut/bolt seat styles in regular use. Generally VW use the radiused seat style [fig 2] along with Mercedes and Porsche, other manufacturers and the aftermarket tend to use the tapered style [fig 3]. Before ordering please make sure you check your wheels that you intend to fit for what style of seat they have as although the wrong sort will fit they won't be right. The purpose of the seat is to get the wheel to centre on the hub, incorrect seat types will damage the wheel.

 

Fig 1. A basic cross section of a typical wheel

 

 

Fig 1. A basic cross section of a typical wheel

 



Fig 2.

 

 Radiused wheel nut, note rounded shape of the part that touches the wheel.

 

Radiused wheel nut, note rounded shape of the part that touches the wheel.

Fig 3.

Tapered seat, note flat sides of the part that touches the wheel.

Tapered seat, note flat sides of the part that touches the wheel.

 


Please note that T3's that left the factory with alloy wheel actually have tapered seats.



Making your chosen wheels fit.


Spacers.

Spacers should be used to correct the offset of the wheel you are fitting. VW spent a lot of time and money developing the suspension on the T3, all the steering geometry, wheel bearings etc. are all set up for standard wheels. If you vary from factory settings then you are likely to gain some strange handling characteristics and accelerated tyre wear.


T3's that came from the factory with steel wheels have a ET of 39 while T3's that left the factory with alloy wheels came with a ET of 30.
So, in my eyes if you are fitting alternative wheels you should be aiming for anywhere between ET 30 and ET 39. When using a wheel that wasn't designed for the T3 then you are unlikely to get the correct ET, this can be remedied by the use of spacers.

 

e.g., if your wheel has a ET of 45 then the use of a 10mm spacer shim would reduce the effective ET to 35, which is in the middle of the range of factory wheel offsets and would be acceptable for use. Wheels with a ET of less than 30 tend to stick out more and give the vehicle a feeling of not wanting to do much more than going in a straight line, wheel bearing load will be increased, steering will be heavy and the tyres will wear more on the inside edge and in my eyes are to be avoided. Spacers are also used for clearance issues, if wide wheels are used then sometimes there is the chance of them fouling the suspension. You can't really go much more than 8" at the front without touching the suspension or having wheel arch clearance issues. Sometimes if you are adamant you need to fit a certain wheel the only way to do it would be to disregard what the ET is and use sufficient spacers to keep the wheel from touching the suspension, this is not ideal and not recommended.

 

Conversion studs.
The conversion studs we stock are a real bonus for anyone who has ever tried to fit a wheel to the front of a T3 which has spacers fitted. Before ordering, please do a little homework first and measure the distance from the bottom of the wheel nut seat (narrow end) to the rear bolt face of the wheel. 

Fig 4.

Cross section of a alloy wheel showing the bolt hole detail.

Cross section of a alloy wheel showing the bolt hole detail.

 


Above is a cross section of a alloy wheel [fig 4], to be able to order the correct conversion stud you will need to know the ET (offset) of the wheel plus the measurement from the bottom of the seat to the bolt face.


e.g..

ET 45
Depth of wheel bolt hole 10mm

So, with a ET of 45 you will need a 10mm spacer to bring the ET down to 35.

You have a 10 mm spacer plus the depth of the wheel bolt hole is 10mm giving you 20mm up to the bottom of the nut.
A wheel nut is generally around 25mm deep giving 45mm.

 


10 + 10 + 25 = 45

or

Spacer + bolt hole depth + 25 = conversion stud required

 


Therefore you will need a conversion stud that protrudes by 45mm from the disc.

Of course, it doesn't always work out nice like my little example but you get the idea, right?