Looking at fitting some non Škoda alloys to my Elegance estate when it arrives, just to be a little different to others. I know 18" alloys will fit, but the genuine Škoda are 7.5 the ones I'm looking at are 8" so I need to look at different offsets. My question is what offset would these need to be, most are +45 but then I have to select either a 72 or 76mm hub. Does any one know which is needed? Any info would be great.

Have a look at: http://www.wheels.oponeo.co.uk/

 

You should find something there that will "float your boat" 

Easiest way to work it out...

 

If your standard offset is 51, for every 1mm you reduce that offset your wheel will move 1mm further out towards the edge of the car and away from the suspension (the offset being the distance between the centre-line of the wheel and mounting face of the wheel hub).

 

If you're wanting to replace your 7.5J (approx. 191mm) wheel with an 8J (approx. 203mm) wheel, you're increasing the rim width by 12mm (essentially 6mm on both sides), and if the 8J wheel has the same offset as your 7.5J wheel (51), you're therefore going to be 6mm closer to the suspension and 6mm further out towards the edge of the car than you were with the 7.5J wheel.

 

If your 8J wheel has an offset of 45 (i.e. it's moved 6mm further out towards the edge of the car) then you're going to be 0mm closer to the suspension and 12mm further out towards the edge of the car than you were with the 7.5J wheel.

 

With regards to the hub, it's generally a non-issue as long as it's larger than your car's standard (which I think will be 57.1mm - please someone correct me if I'm wrong on that) as you can get spigot rings to reduce the bore to suit (most reputable retailers will ask this question when you purchase the wheels and supply the relevant rings).

 

Consider also; PCD (pitch circle diameter) of the bolt pattern and number of bolts, wheel bolt length and seat type (radius or taper/cone) - these may differ on aftermarket wheels, brake caliper clearance (more notably an issue on the larger endowed vRS), and tyre stretch (if using your standard tyres on wider rims).

 

There's a lot to consider (especially from the safety point of view), and one of the best sources of information on the internet can be found here - http://www.carbibles.com/tyre_bible_pg4.html

 

Read and digest this and you'll be an expert within the hour (or maybe hour and a half). There's also some extremely useful Javascript applications to help work out changes in offset, rim width, tyre size and rolling circumferences (and it's effect on your speedometer/odometer).

 

Mine's soon to be fitted with 8.5Jx18 ET42's on the stock supplied tyres with 40mm lowered suspension, and no issues.

 

I've seen a couple of pics of people running 9.5Jx19 ET35's on 225/35 tyres and coilovers on the new Octavia, but this is perhaps a step too far… and the ride must be awful.

Easiest way to work it out...

 

If your standard offset is 51, for every 1mm you reduce that offset your wheel will move 1mm further out towards the edge of the car and away from the suspension (the offset being the distance between the centre-line of the wheel and mounting face of the wheel hub).

 

If you're wanting to replace your 7.5J (approx. 191mm) wheel with an 8J (approx. 203mm) wheel, you're increasing the rim width by 12mm (essentially 6mm on both sides), and if the 8J wheel has the same offset as your 7.5J wheel (51), you're therefore going to be 6mm closer to the suspension and 6mm further out towards the edge of the car than you were with the 7.5J wheel.

 

If your 8J wheel has an offset of 45 (i.e. it's moved 6mm further out towards the edge of the car) then you're going to be 0mm closer to the suspension and 12mm further out towards the edge of the car than you were with the 7.5J wheel.

 

With regards to the hub, it's generally a non-issue as long as it's larger than your car's standard (which I think will be 57.1mm - please someone correct me if I'm wrong on that) as you can get spigot rings to reduce the bore to suit (most reputable retailers will ask this question when you purchase the wheels and supply the relevant rings).

 

Consider also; PCD (pitch circle diameter) of the bolt pattern and number of bolts, wheel bolt length and seat type (radius or taper/cone) - these may differ on aftermarket wheels, brake caliper clearance (more notably an issue on the larger endowed vRS), and tyre stretch (if using your standard tyres on wider rims).

 

There's a lot to consider (especially from the safety point of view), and one of the best sources of information on the internet can be found here - http://www.carbibles.com/tyre_bible_pg4.html

 

Read and digest this and you'll be an expert within the hour (or maybe hour and a half). There's also some extremely useful Javascript applications to help work out changes in offset, rim width, tyre size and rolling circumferences (and it's effect on your speedometer/odometer).

 

Mine's soon to be fitted with 8.5Jx18 ET42's on the stock supplied tyres with 40mm lowered suspension, and no issues.

 

I've seen a couple of pics of people running 9.5Jx19 ET35's on 225/35 tyres and coilovers on the new Octavia, but this is perhaps a step too far… and the ride must be awful.

This has been super useful trying to understand the different figures and how they relate! Nookiebear, what dimensions do you think will work with the RS? E.g. how close and how far away from the suspension?

I too will be looking at an aftermarket set for my winter tyres later in the year, so thanks for the useful info and links.

 

One quick question though, is there anything special required for the Tyre Pressure Monitoring System to function correctly? Or is it just calculated by the electronics from a (amongst other things) variance in wheel speeds across an axle?

It just uses variance in wheel speeds, a fairly simple system

This has been super useful trying to understand the different figures and how they relate! Nookiebear, what dimensions do you think will work with the RS? E.g. how close and how far away from the suspension?

As mentioned, I'm fitting 8.5J ET42's (with the standard 225/40 tyres) which will be 21.7mm further outboard towards the wheel arch and 3.7mm further inboard towards the suspension. Several others have also done this (at ET42-45) without issue. Another user has just fitted 12 & 20mm spacers front & rear on the standard 19" ET51 extremes and is very pleased with the look.

In answer to your question regarding what works, I personally think 7.5J is too narrow for the standard wheel, so I would say look at 8-8.5J. The majority of the wheels you'll find will be 8J which is a very popular size for aftermarkets. ET will depend on which you choose, and again ET45 is a very common offset (especially for vehicles with a 5x112PCD such as most modern VW's, Audi's, Seat's, Skoda's and Mercedes), but I would say you need to keep the inner edge of the rim to within 8mm, and the outer edge to within 27mm, of their current positions (maximum).

Suggestion wise, 8J ET45 works well on the RS, but if you want a bit of a wider stance consider 8.5J ET40-45.

If you're buying online you need to do the calculations (use the JavaScript applications on http://www.carbibles.com/tyre_bible_pg4.html), but most good sites will ask you the make and model of the car anyway and state if a wheel is suitable based on a database of vehicle info they hold.

If you're buying from a bricks & mortar showroom, then they should be happy to try the rim on your car if they have it in stock so you can see how it looks.

As a final point, with the RS pay heed to the info you put in on any website, i.e. make sure if the option to state 'vRS' is given, that you tick the box as this should take into account the rather substantial front brake discs unique to it and knock out any wheels that may conflict with them and/or the calipers.

 

One quick question though, is there anything special required for the Tyre Pressure Monitoring System to function correctly? Or is it just calculated by the electronics from a (amongst other things) variance in wheel speeds across an axle?

The TPMS operates on a basic wheel speed/revolution system to the best of my knowledge, so no issues as far as I'm aware and I've not come across any posts on this forum to indicate the use of aftermarket wheels has caused problems for anyone.