What is the max sidewall size I can have on my 16 inch wheels I currently have 205 45 r16 could I fit a 205 50 r16 or even a 205 55 r16 how much will this effect the wheel arch gap I am on stock suspension which is about 4cm from the tyre to the arch.
If you go to 205/55 16 it will be 2cm more radius and will change the gearing by 7% making your speedo illegal (and the car looking like a 4x4) Not a good way to fill the wheel arch gap. Handling will be worse also as you will get noticeable tyre roll, and a higher centre of gravity
Try it is the answer.
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Trying it will be costly if you need to change the speedo. The best way is to lower the suspension by fitting different springs - not expensive, at least for parts. Which model do yo have?
Don’t worry about the speedo argument. Most speedos read up to 10% over anyway.
7% of 30 mph is 2.1 mph. Go out in your car and see what a gps speed app says at an indicated 30 mph.
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It will certainly have an effect on the ride - will potentially increase ride comfort as there will be a bit more sidewall depth, but may correspondingly decrease handling - however unless you are very sensitive, it will probably not be noticeable…
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I tried on my FN2 Type R
19"/35
18"/40
17"/45
16"/50
To be honest in terms of of handling the bigger rims felt quicker to turn even though my 18" were around 10kg per rim and my 16s was 7kg. In the end I settled for 18" with 40 profile.
The big side walls on the 16s didn’t improve ride comfortable and overall vs the 18" with 40 profile the 16s were smaller and this lowered the right height too much. Was around 10mph speedo difference between the biggest and smallest rim sizes.
Like said it’s best to try but unless you can find some very cheap 114.3x5 rims with the 67.1mm center bore or bigger it would be a costly and long process.
Use this page for a before and after comparison of the shapes of the different tyre sizes and on the speedo reading, etc., though this won’t help with the fitment question.
I mocked up your question, to show the difference on speedo and a clue on sizes:
https://www.willtheyfit.com/index.php?width=205&aspect=45&diameter=16&wheelwidth=6.5&offset=35&width2=205&aspect2=55&wheel_size=16&wheel_width=6-5&offset2=35
The difference isn’t that big but, at 30, it’ll read 28 and at 60, it’ll read 56. It’s the fact that you’ll be going faster than you think which would be the main issue in reality. If you’re reading 60 and actually doing 65, it might be enough for a stingey copper to give you a ticket.
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These measurements are useless without providing the width of each tire.
The numbers you have here (35, 40, 45, 50) are just percentages of the width.
E.g. 245/40 has the same sidewall size as 195/50.
17 18 19 were 225 and 16s were 205.
Out of interest - how will the speedo be illegal? There’s no legal requirement for speedo accuracy as far as I am aware (or even the presence of one!).
Edit: I Googled! The Road Vehicles (Construction and Use) Regulations 1986 cover the presence of one. Every day is a school day.
Speedo can be reading up to 10% fast but cannot read slower than the vehicle speed
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What actual car is this. I assume a MK2 and if so you may very well have arch clearance issues, especially on full lock. If it is a MK3 then the tyre size would be 205 50 16 to start with and 205 55 fit with no issues.