Wheel sizes

[Brandonmac]

On my ibiza cupra at the minute I’ve got 215/40/r17
I’ve came across some wheels that are 225/45/17 front and 245/40/17 back am I going to have any major fitment issues here

 

[SRGTD]

That’s the tyre size you’ve quoted rather than the wheel size.

To understand if you’ll have any fitment issues, you‘ll need the spec details of the wheels. From the size of the tyres, we know the wheels are 17 diameter, but you also need;

• PCD (bolt pattern) and centre bore size to ensure they’ll bolt on to the car’s hub assemblies.
• wheel width (the ‘J’ size). As the tyres are different widths for the front and back, the rear wheels may also be wider than the fronts (i.e. a staggered set up).
• Offset; if the offset is quite aggressive, there’s an increased risk of rubbing / clearance issues, especially with the larger tyre sizes you’ve quoted. You’d also get a speedo reading error as the overall rolling radius will be larger than with your existing wheel / tyre set up.

If you use a calculator like the one on www.willtheyfit.com and input details of both your existing and new wheel / tyre set up, it’ll calculate the important numbers for you (e.g. changes in tuck, poke and % speedo reading error).

Bear in mind fitting different wheels is a modification for insurance purposes so you’d need to inform your insurer. Depending on how mod-friendly your insurer is, they may alter your premium.

 

[DAN@ADRIAN FLUX]

Hi.
If you have any issues with insurance at all for a change of wheels then please feel free to drop me a line.
Regards,
Dan.

 

[Brandonmac]

That’s the tyre size you’ve quoted rather than the wheel size.

To understand if you’ll have any fitment issues, you‘ll need the spec details of the wheels. From the size of the tyres, we know the wheels are 17 diameter, but you also need;

• PCD (bolt pattern) and centre bore size to ensure they’ll bolt on to the car’s hub assemblies.
• wheel width (the ‘J’ size). As the tyres are different widths for the front and back, the rear wheels may also be wider than the fronts (i.e. a staggered set up).
• Offset; if the offset is quite aggressive, there’s an increased risk of rubbing / clearance issues, especially with the larger tyre sizes you’ve quoted. You’d also get a speedo reading error as the overall rolling radius will be larger than with your existing wheel / tyre set up.

If you use a calculator like the one on www.willtheyfit.com and input details of both your existing and new wheel / tyre set up, it’ll calculate the important numbers for you (e.g. changes in tuck, poke and % speedo reading error).

Bear in mind fitting different wheels is a modification for insurance purposes so you’d need to inform your insurer. Depending on how mod-friendly your insurer is, they may alter your premium.

Hi mate so the tyre size is 7J, originally on I think are 6J at the minute, if the alloys fit I’m happy to change Tyres ect to make it work

 

[SRGTD]

Hi mate so the tyre size is 7J, originally on I think are 6J at the minute, if the alloys fit I’m happy to change Tyres ect to make it work

7J is the width of the wheel, not the tyre size.

In your original post you quoted the wheel sizes as 225/45/17 front and 245/40/17 back. Those are the tyre sizes, not the wheel size. For the 225/45/17 tyre;

• 225 is the tyre width in millimetres
• 45 is the sidewall height; expressed as a percentage of the tyre width, so 225mm x 45% = 101.25mm tyre sidewall height
• 17 is the diameter of the wheel that the tyre fits.

You need details of the offset of the wheels you’re interested in - without that information, you won’t be able to determine whether or not you’ll have any clearance issues. Also, the bolt pattern needs to be the same as your existing wheels (PCD 5 x 100), otherwise the bolt holes in the wheels won’t line up with the bolt holes in your car’s hub assemblies, meaning you won’t be able to bolt the wheels onto your car. Also check that the centre bore size of the wheels you’re interested in is 57.1 or larger (57.1 should be the centre bore size of your current wheels - assuming they’re the original factory wheels on your car) - if it’s larger than 57.1, you can get a set of spigot rings of the correct size to reduce it to 57.1. The wheel spec information is normally stamped into the reverse side of the wheel spokes - e.g. 7J x 17“ ET40 (this is just an example of what information to look for on the spokes and is unlikely to be the actual spec of the wheels you’re interested in).

Once you‘ve got wheel width (the J size), offset (ET value), wheel diameter, and tyre size information for both your current and new wheel / tyre set up, put the information into the wheel calculator at the link I provided in my previous post. The calculator will give you the critical numbers to enable you to assess whether or not you’d be likely to have any clearance / rubbing issues, and the % of any speedo reading error. Note that it is illegal in the UK for a speedo to show less that the actual speed your car is travelling at. The speed can show a higher speed that the speed you’re travelling at; the permitted margin of error is 110% of the true speed +6.25 mph - see article at the link below;

How accurate is your car speedometer? #AskTCE

Have you noticed that your car speedometer reads faster than your satnav says? Find out why this happens in this week's #AskTCE at TheCarExpert.co.uk

www.thecarexpert.co.uk

Edit; something else to consider is wheel bolts. Seat OEM alloys use bolts with a radius / ball seat; the seat of the bolt matches the profile of the bolt hole in the alloy to ensure the maximum contact patch between the two surfaces is achieved. If the alloys you’re considering are an aftermarket set rather than OEM Seat alloys, be aware that most - but not all - aftermarket alloys use bolts with a tapered / conical seat. You can see the difference in the picture below (bolt with tapered / conical seat on the left and radius / ball seat on the right). For safety’s sake (to ensure the bolts don’t come loose when the car’s being driven), it’s really important the correct bolt type is used for the alloys being fitted.