How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • Go back-and-forth until satisfied
    Rate the answer you receive.
Ask Kevin Your Own Question
Kevin, BMW Technician
Category: BMW
Satisfied Customers: 7661
Experience:  Diagnostic technician at Kemsing motor company
Type Your BMW Question Here...
Kevin is online now

I am hoping to get some advice regarding my tires, Sizing

This answer was rated:

Hi, I am hoping to get some advice regarding my tires
JA: How old are the tires? And have they been a problem in the past?
Customer: Sizing wise I’m not sure what’s compatible other than the ones I’ve got
JA: What is the model/year of your BMW?
Customer: 14 plate 420 Msport
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: I wanted to either go down to 18 inch tired or 17 inch currently it’s 19 inch
JA: Is there anything else the Mechanic should know before I connect you? Rest assured that they'll be able to help you.
Customer: No issues at all with the car other than advice needed for sizing pls

Hello and thank you for using JustAnswer. My name is***** am a vehicle master tech located in the UK and I will do my best to assist you. During this conversation, you will be given an automated offer for a phone call. You may accept or decline that offer. I don’t personally offer this service so if you take this another tech may call I’m sorry that you’re having trouble with your vehicle. Don’t worry though, we’ll be able to figure this out. Please understand that I do not know your knowledge or capabilities so I may need to ask questions to find out basic information to help solve your specific problem. My aim is to give you the best service possible and to help you. If you have any questions or concerns, please don’t hesitate to let me know. Sometimes it may take a moment for me to respond because I may have to look up information about your concern. I appreciate your patience and will provide responses as soon as possible. Can I first ask who I have the pleasure of speaking with today, please?

Customer: replied 9 days ago.
My name is Muna
Customer: replied 9 days ago.
Phone call would be amazing too
Customer: replied 9 days ago.
Cancel that
Customer: replied 9 days ago.
Didn’t realise it’s chargeable

Hi, Muna I hope you are well. Can you tell me the reason behind the change in size?

Customer: replied 9 days ago.
Hi Kevin, I used to have a smaller size on there previously
Customer: replied 9 days ago.
I just can’t remember

ok so are you wanting to go back to the smaller size that was fitted from the factory?

Customer: replied 9 days ago.
I want to go back to factory settings

perfect that's no problem at all. If i can take the vehicle identification number i can look this up for you

Customer: replied 9 days ago.
My car registration is Rv14ghb if you can kindly advice what size I could go down to safely

no problem give me a few mins while i look this up

Customer: replied 9 days ago.
Perfect thank you
Customer: replied 9 days ago.
if you can also let me know what the recommended tyres should be
Customer: replied 9 days ago.
Are you still there?

ok, so the 225/50/17 or the 225/45/18 are regularly run sizes so both the 17 and 18 in rim could be used. but after fitting the system should be programmed so the car knows it's running a different rolling diameter of wheel and tire. you also currently have a staggered rim size so the rim on the rear is deeper than the front ones.

18 in rim size should be rear 8,5JX18 front 8jx18

17 in rim size should be rear8.5jx17 front 8J x17

Customer: replied 9 days ago.
when I choose either 17 inch or 18 inch do the front and back both need to be the exact same size?

yes, they can run the same size tire.but after fitting it needs to go to BMW so the computers can be told the wheels are a different size

Customer: replied 9 days ago.
Is BMW the only one who offers this service? Do you know how much this costs?

as far as I'm aware yes. Average cost around £100

Customer: replied 9 days ago.
Thank you Kevin and does Bmw recommend 18 inch?


Customer: replied 9 days ago.
Thank you so much
Customer: replied 9 days ago.
I haven’t been charged for the phone call have I?

You are very welcome. I don't control charges as I'm just a tech working here but if its not used and its charged for typically its refunded

Customer: replied 9 days ago.
Lastly what does this mean? 8,5JX18 front 8jx18

that's the alloy wheel sizing

Customer: replied 9 days ago.
do I purchase any 18 inch run flat or do I need to covert that

yes run-flats would be recommended

Customer: replied 9 days ago.
Does it matter 225/45? Or any

225/45 is a recommended size from BMW for the 18 inch type

Customer: replied 9 days ago.
Thank youuuu
Customer: replied 9 days ago.
How can I rate the service?

you're very welcome. Thank you again for visiting JustAnswer, please let me know if you need me to clarify anything or if you have any additional questions-I am happy to help!

Kevin and other BMW Specialists are ready to help you