Wheel and tyre advice

[Muderick]

Hi guys...

I need some consensus as to the size of tyres I can use on a set of BRM's I bought a few months ago. The rims are 15" x 5,5" wide with an offset of ET10

Can anybody explain what ET10 means, in light of me dropping my bug 2.5" in front via dropped spindles, and 1 spline turn at the back.

I have purchased 2 Hankook 175/50/15's for the front, and I am leaning towards 185 or 195 / 65 or 60 / 15's in 205PCD, so no adaptors luckily for the rear to try and stay with the stock geometry.

What I need to have answered is the following. I did not have a choice in the wheel offset, so what does ET10 mean considering the options I would like to use. How will the wheels fit the fenders front and rear... will they stay tucked behind the fenders or be wider than the fenders?

Muds

[vader]

From what I understand the edge of the rim ( outside ) is "pushed" 10 "units" (notsure if its mm or cm) out. So basiclly that lip/dish you have is 10 units further out than std.

I think you should clear the fenders but there is only one way to find out...

But then again Darren you are only running 175/50/15 so you shouldn't have issues...

The rear should be fine as well you dont have HUGE rubber....

[Dutch_Diver]

Muds, I had the same worries with the Fuchs on Mo. In the end, I went to the Tyre place in Stellenbosch and the owner fitted some tyres and then we fitted the wheels on the bus to check clearance and fit. Worked well. He gained as I bought 4 tyres and I had comfort.

If you want the details of the place I can give them but the owners name was Jean and his son also works there but can't remember his name!

[Tony Z]

I heard the ET is a measurement from the mounting flange on the rim to the fender wall (verticle line drawn from fender to ground).
I have ET35s and just clear (but i have discs all round). So my distance in further than yours would be.

There has to be aproper explanation online somewhere if you search long enough

[smeegle]

found this explanation ET gets explained at bottem
http://www.driverstechnology.co.uk/wheel-offset.htm

hope it helps

[Tony Z]

thanks smeegle

Another important thing is the wheel offset, which is the distance between the middle line of the centre of the wheel width and the mounting surface of where the wheel bolts to the hub on the vehicle. The offset is described by the term ET, which is from the German word 'Einpresstiefe' translated as 'insertion depth'. Most wheels have a positive offset which means the mounting surface is further outboard than the wheels centre. If you reduce the amount of positive ET on the wheel the the vehicles track is widened and vice versa if the ET number is reduced.

[Muderick]

Thanks Guys!! so this means that the ET 10 offset on my wheels should hopefully ensure that the wheels would sit inside the fenders?

[powerbug]

Hi Muderick

Hope this helps you to understand what ET is.

Courtesy of http://www.csp-shop.de

The offset of a wheel is not the discount one can get by buying a set of four. Rather it is the parameter that tells whether a wheel will fit under a particular wing, whether and by how much the wing should be widened, or whether the roll radius that stabilises the tracking will be held constant if this wheel is fitted.

For the front axle the roll radius is the distance between the right-hand and left-hand average point of contact of the tyre with the ground (the centre of the wheel footprint). If the offset is positive the roll radius reduces, and if the offset is negative or spacer disks are fitted the roll radius increases. The smaller the roll radius, the more pleasantly the car drives and the easier it is to control in difficult situations. The visual effect is of course a matter of taste, and many people like the wide look! To be able to assess what looks OK, what doesn't look OK and what generally makes sense the one thing that must be fully understood is how offsets are calculated.

For tuning enthusiasts offset is therefore a parameter of particular interest. It not only simplifies the correct selection of wheels and bodywork parts, but also shows, for example, whether technically necessary modifications to the chassis (such as can occur for instance when installing non-standard braking systems) can be compensated for by the use of particular wheels.




Each wheel has a surface that fits against the connecting face of the brake drum or the brake disc (only if it is bolted to it as designed, of course!). This surface is called the flange. The second parameter that is important here is the wheel well. This is the region between the wheel rims. The distance between the wheel rims is the width of the well, and this provides a measure for the wheel width (always defined in inches). One inch corresponds to 2.54 cm. A "9-inch wheel", for example, measures approximately 23 cm in width.

The wheel offset defines the distance of the flange from the centre of the wheel mouth in millimetres. If the offset is zero, the flange is located exactly in the centre of the wheel, and the wheel extends exactly as far outwards as inwards. For example, a 9 inch width wheel with an offset of zero extends 11.43 cm outwards and 11.43 cm inwards. A positive offset (e.g. +25) indicates that the wheel extends further inwards (towards the centre of the vehicle) than outwards (towards the wing housing).

Starting from zero, the track would become narrower by 25 mm. A negative offset (e.g. -25) would mean that the wheel extends outwards and the track would be wider (again by 25 mm starting from zero). If we therefore had two pairs of wheels of equal width to choose from, one having an offset of plus 25 mm and the other minus 25 mm, we could make the track 5 cm wider on each side by fitting the pair with the negative offset rather than the other pair. In total the track would be 10 cm wider than with the "positive offset" wheels.

The running surface of the tyres, which is still a fundamental parameter for the TÜV inspection in accordance with German standards (if not European) does not alter its location at all as a result of any variation in wheel width, but solely as a result of its offset. If therefore there is insufficient running surface cover, no narrower wheel will help, but only one with a greater offset.

At the present time there is an enormous number of wheel types. Only three-component wheels allow exact matching of width and depth, and these wheels also have the advantage that, for example, in the event of kerb damage only the outer ring has to be replaced (cheaper than buying a new wheel or getting the damaged wheel ground and repainted).

[calooker]

When I was hunting for tyres for my notch with BRM's the 185/60/15 in the rear was a problem but on Gerard's beetle they were fine and he had longer (later) axles, as we tried diffrent combos as well landed up going with smart car tyres front & rear for the notch.
If you have short axles on your bug then a wider than a 185 in the rear should be no problem at all. We also tried the same 185/60/15 in the front of the beetle & it was just inside the fender but it looked too close for comfort as I'm sure it would touch when hiting a bump during driving.

[Guardian]

Great advice on here, and a quick related question - if going 17", what would the 'J' need to be in order to get the wheels to fit nice and snug juuuuust adequately beneath the stock fenders of a '77 Beetle? (i.e. 17 x 7", 17 x 7.5", 17 x 8", 17 x 8.5" ???). p.s. I don't particularly dig the negative camber look...makes me feel sad for the tyres.

Busy shopping for a decent set of rims for my car because my disc kits will be arriving soon.

[Tony Z]

any J size will fit, its the offset that you need to check.

I run 35mm offset and it fits my car snug. but I have disc brakes on all 4 corners. Using wheel adapters will make the tires stand out further.

Buy a set of adapters and take them with to the tire place. Then check.

[Tony Z]

BTW, 7" or wider makes the turning circle crap. Trust me, I know, I have 7.5J

[Guardian]

Thanks Tony, much appreciated.