Wheel rim choice – Diamond Cut or Powder Coated?

Post edited as I got the numbers back to front!

Going from 19” to 20” actually makes the overall diameter of the wheels about 8mm bigger at the front, so 4mm extra ground clearance. For rear it’s about 10 mm extra with 20’s so 5 mm extra clearance at the back.

Fronts

245/40 R19 = 678.6 mm diameter
255/35 R20 = 686.5 mm diameter
 
Correct answer but not sure about the maths :D

I think we're talking diameter rather than circumference (unless you're working out your final drive ratio).

Results above are transposed for 19" / 20", but obvious what you mean.

What you're really looking for is the increase in axle centreline height, so half diameter + 1x side wall height.

Of course your clearance decreases then with tread wear, or under-inflation.
 
Lunar said:
Correct answer but not sure about the maths :D

I think we're talking diameter rather than circumference (unless you're working out your final drive ratio).

Results above are transposed for 19" / 20", but obvious what you mean.

What you're really looking for is the increase in axle centreline height, so half diameter + 1x side wall height.

Of course your clearance decreases then with tread wear, or under-inflation.
Click to expand...

Thanks Lunar, I’ve edited my post to try and save some dignity!
 
GusA said:
Post edited as I got the numbers back to front!

Going from 19” to 20” actually makes the overall diameter of the wheels about 8mm bigger at the front, so 4mm extra ground clearance. For rear it’s about 10 mm extra with 20’s so 5 mm extra clearance at the back.

Fronts

245/40 R19 = 678.6 mm diameter
255/35 R20 = 686.5 mm diameter
Click to expand...


Good to know that there’s extra ground clearance with the 20” wheels and tyres.........this should mean less scraping of the front bumper lower air deflector!

I’ve attached two screenshots showing details of the front 245/40 R19 and 255/35 R20 tyres. This shows tyre width, rim diameter, sidewall height, tyre diameter and circumference etc.

I have seen a few F-Type owners saying they’ve reverted back to 19” wheels as the ride was too firm on the 20” so I was trying to find out how harsh the difference actually is? As my car has the sports suspension with adaptive dynamics, do you think this would help to compensate for the firmer ride on the 20” lower profile tyres or would it have no effect?
 

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Can’t really give an objective answer but I have 20” and adaptive dynamics and find the ride perfectly acceptable and remarkably good over poor road surfaces. I did read an article a long time ago that said the adaptive suspension made a big improvement to ride comfort over the base system, but again this is one persons opinion.
 
RPSN said:
I have seen a few F-Type owners saying they’ve reverted back to 19” wheels as the ride was too firm on the 20” so I was trying to find out how harsh the difference actually is?
Click to expand...

Interesting, I've seen posts from people who've gone from 19" to 20" and claim not to have noticed any difference! Go figure ... :?
 
Found these mixed opinions on 19” versus 20” wheels......

https://www.ftypeforums.co.uk/viewtopic.php?f=17&t=4121

One of them saying.......

”There’s no doubt in my mind that:
- 20’s are harsher than 19’s simply due to basic physics that you have removed 1/2” of tyre suspension. Some will notice it others not.
- Tyres cost more and rims and tyres are more vulnerable to pothole and kerbing damage.
- Looks are way better on 20’s and really suit.
- easy item to upgrade when new tyres due if the perfect car is currently on 19’s.”

As I mentioned earlier, I’ve not long had new Michelin PS4S tyres fitted on the rears so I’ll wait until I’ve had good wear out of them before making a decision on the 20” wheels......glad I’ve looked into this beforehand though!
 
RPSN said:
- 20’s are harsher than 19’s simply due to basic physics that you have removed 1/2” of tyre suspension. Some will notice it others not.
Click to expand...

As a 20" man (ooer!), I have to point out that we say "firmer", not "harsher". ;)
 
Lol. It depends in which context it is said.......read through my own posts as a 19" man who uses the words 'firmer' and 'harsh'!

When you say ‘we’, I hope you've excluded the 20” men in the link I posted above who said.......

“20’s are harsher than 19’s simply due to basic physics that you have removed 1/2” of tyre suspension. Some will notice it others not. All down to choice. To me 20’s were the only choice.”

and....

“I went for a car with 20's as I preferred them over the style of the 19's. I don't find the ride harsh at all.” ;)
 
I've noticed that :lol:

Time to get on the garden lounger now and take advantage of this warm spell whilst it lasts........changing tomorrow according to the forecast!
 
Get the 20” wheels for the summer and keep the 19” wheels to fit winter tyres!
 
That’s a good idea and I did think about it but I don’t have a garage to keep the 4 x spare wheels. Also, my garden shed doesn’t have sufficient space to store the wheels. I thought about putting them in the attic (floor boarded) but it would be a real PITA to get them up there and back down again!

The other thing is, if I bought and fitted the 20” wheels, the car's speedo would need to be recalibrated. If I then changed from 20” to 19” wheels for the winter periods, the speedo would be out of sync unless it was recalibrated again, and so on. I think this costs approx £120 - £150 each time, at my Jaguar main dealer.
 
Believe me, mounted tyre size not withstanding, you would not be able to lift a 20" wheel and tyre up a ladder into the attic.
Even just hefting them up onto the wheel studs is a workout.

I made room in my shed to stack them so have the winters wearing Sottozero and the summers (20") wearing PS4s.
...I also now have 8 wheels I can curb!

Regarding recalibration, the rolling circumference of a 19" and a 20" wheel differs by 31.8mm per rev. (assuming same tread depth and tyre pressures).
So a 20" travels 1.5% further per rev which, for our national limit of 70mph, equates to 1.05mph.
If you really want to spend that cash on recalibration then I'd be happy to take it from you and tell you I've done it (within normal 1.5% tolerance) :D

Assuming that the engine overcomes the increase of torque needed to turn the 10mm bigger diameter and heavier wheels you're also getting a 1.5% increase in acceleration, which is almost 1/10th of a second - although I reckon that's an assumption too far.

...all pedantic replies welcome ;)
 
I’ve also noticed that when removing the 19” Propeller wheels & tyres from my car, how heavy they are and like you say about the 20”........ “Even just hefting them up onto the wheel studs is a workout.”

Those 20” Turbines must be quite a bit heavier than mine so if I decided to buy them I can rule out storage in the attic!

I much prefer to remove the wheels myself when doing maintenance etc on the car so the heavier 20” wheels & tyres could become a problem for me as I’m getting older! This may be an influencing factor in deciding whether or not to go from 19” to 20” ?

There’s definitely no need for a speedo recalibration based on your statistics for the 19” and 20” wheels! This information would save some money for those who are considering having it done when increasing the wheel size!

You’ve mentioned an increase in acceleration of 1/10th of a second due to the larger wheels........I wonder if there would be a slight improvement in mpg?

I’ll leave any pedantic replies to the regular contributor :)
 
Some of the guys on the US forum have gone for VS forged wheels which save a considerable amount of weight over the stock ones. They claim to have improved handing noticeably, albeit at a price.
 
I can well imagine that - it could make a fair difference to the handling when you weigh up the 4 corners.

I remember weighing a rear as I was surprised at the weight - think it was 38.6kg but don't quote me on that.
 
RPSN said:
I’ve also noticed that when removing the 19” Propeller wheels & tyres from my car, how heavy they are and like you say about the 20”........ “Even just hefting them up onto the wheel studs is a workout.”

Those 20” Turbines must be quite a bit heavier than mine so if I decided to buy them I can rule out storage in the attic!

I much prefer to remove the wheels myself when doing maintenance etc on the car so the heavier 20” wheels & tyres could become a problem for me as I’m getting older! This may be an influencing factor in deciding whether or not to go from 19” to 20” ?

There’s definitely no need for a speedo recalibration based on your statistics for the 19” and 20” wheels! This information would save some money for those who are considering having it done when increasing the wheel size!

You’ve mentioned an increase in acceleration of 1/10th of a second due to the larger wheels........I wonder if there would be a slight improvement in mpg?

I’ll leave any pedantic replies to the regular contributor :)
Click to expand...

You guys need to man up. Try lifting and fitting 35 or 37'' MT tyres. Typically they get knocked off the Jeep rims in tight V shaped ruts and with long travel suspension you need to jack the corner up anything up to 1m and lift 60kg onto the studs. Usually done stood in a stream or deep mud..

Where I do agree is the lack of need to recalibrate. People often compare static wheel/tyre diameters, but as posted it's rolling radius that matters
 
scm said:
Some of the guys on the US forum have gone for VS forged wheels which save a considerable amount of weight over the stock ones. They claim to have improved handing noticeably, albeit at a price.
Click to expand...


Thanks 👍

Just had a quick look........some nice wheel designs here!

http://vsforged.com/wheels/
 
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