Recommended wheel size change
Discussion
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perry690 said:
Can anyone one tell me whats the best size alloy to run on chimera as i want to change alloys
The answer really depends on whether or not you have PAS, or intend to upgrade the dampers to adjustable ones like Nitrons and then, of course, get the suspension properly set-up front & rear afterwards. I would say if you don't intend to touch the suspension 17" all round and if you do you could probably go to 18" but be prepared to spend £1,500 on top of the wheels on suspension. Bobfather said:
You trying to kill him. 17" front 18" rear, any bigger and the car will handle like a pig
I thought that was just PH hearsay.I 'm not aware of anyone who has tried!? Alot of people reckon that Chims/Griffs don't handle on 17/18's ( usually people who haven't tried it)but mine was a lot more surefooted than on 15/16's. No doubt the car would handle completly different than what it does at the moment but I doubt it would be totally horrible with some proper suspension set up.One day I may be the first to try 
Requirements vary: looks, comfort, or performance? (Remember that even the later T-series cars were designed to run on 16” wheels.)
Assuming that you keep the rolling radius the same then larger wheels will:
Downside: - cost more, have more expensive tyres, perform worse in the wet, perform worse on bumpy roads, be more susceptible to tram lining, increase the weight of the car, increase the unsprung weight, produce a harsher ride, increase the rotating unsprung weight (second moment of inertia) and be more liable to scuffing on kerbs when parking.
On the plus side they should: - prevent the tyre from distorting thus giving greater cornering grip in the dry and on smooth roads, be more direct giving greater steering feel and control, have less tyre wall flex (thus reducing both heat and fatigue and be better for long high speed journeys) and they should look good. Perhaps most of all they allow you to use top quality (UHP) rubber.
Larger wheels will effectively increase the spring rates and fitting lower section tyres with less sidewall flex can make the car more sensitive to suspension geometry changes. There are advantages to tyre wall flex when cornering too; this flex gives a lot of feedback and enables more progressive oversteer. Reducing this flex gives more ultimate grip but when it reaches the limit there is less opportunity to control it.
If a car was set up for one wheel size then by increasing the wheel diameter, keeping the same rim the same tyre widths the same rolling radius and the same tyre model then the mathematical advantages are not as much as the disadvantages, even after minimising them by adjusting the suspension set-up. Check whether the weight and the cornering speed of the car are not enough to mean that the tyre rolls onto its sidewall causing sidewall scrub during cornering.
Tyres for 14” wheels are a low point for performance rubber. From there the larger the wheel diameter the better the quality of rubber that is available.
Wheels have a mounting offset from centre known as ET (German = Einpress Tiefe, literally meaning "push in depth,") for the Chimaera this nominally needs to be 25mm front and 35mm rear. The Pitch Circle Diameter (PCD) needs to be a three inch square, or approx 108mm and the Centrebore needs to be checked. Wheel spacers can only reduce this ET value, irrespective of the wheel diameter.
Also consider whether you think that very large wheels will look appropriate on a car that was designed with more modest wheels.
16” all round (with 7.5” front and 8.5” rear rims) is probably the best combination. The real choice should be from the roads which you use, your driving style and your preferences.
Cheers, Jonathan
Assuming that you keep the rolling radius the same then larger wheels will:
Downside: - cost more, have more expensive tyres, perform worse in the wet, perform worse on bumpy roads, be more susceptible to tram lining, increase the weight of the car, increase the unsprung weight, produce a harsher ride, increase the rotating unsprung weight (second moment of inertia) and be more liable to scuffing on kerbs when parking.
On the plus side they should: - prevent the tyre from distorting thus giving greater cornering grip in the dry and on smooth roads, be more direct giving greater steering feel and control, have less tyre wall flex (thus reducing both heat and fatigue and be better for long high speed journeys) and they should look good. Perhaps most of all they allow you to use top quality (UHP) rubber.
Larger wheels will effectively increase the spring rates and fitting lower section tyres with less sidewall flex can make the car more sensitive to suspension geometry changes. There are advantages to tyre wall flex when cornering too; this flex gives a lot of feedback and enables more progressive oversteer. Reducing this flex gives more ultimate grip but when it reaches the limit there is less opportunity to control it.
If a car was set up for one wheel size then by increasing the wheel diameter, keeping the same rim the same tyre widths the same rolling radius and the same tyre model then the mathematical advantages are not as much as the disadvantages, even after minimising them by adjusting the suspension set-up. Check whether the weight and the cornering speed of the car are not enough to mean that the tyre rolls onto its sidewall causing sidewall scrub during cornering.
Tyres for 14” wheels are a low point for performance rubber. From there the larger the wheel diameter the better the quality of rubber that is available.
Wheels have a mounting offset from centre known as ET (German = Einpress Tiefe, literally meaning "push in depth,") for the Chimaera this nominally needs to be 25mm front and 35mm rear. The Pitch Circle Diameter (PCD) needs to be a three inch square, or approx 108mm and the Centrebore needs to be checked. Wheel spacers can only reduce this ET value, irrespective of the wheel diameter.
Also consider whether you think that very large wheels will look appropriate on a car that was designed with more modest wheels.
16” all round (with 7.5” front and 8.5” rear rims) is probably the best combination. The real choice should be from the roads which you use, your driving style and your preferences.
Cheers, Jonathan
Edited by JR on Tuesday 16th June 12:23
RichB said:
JR said:
...for the MX-5...
All good stuff Jonathan. The OP relates to a Chimaera, for this the PCD is 108mm 4 x stud (Ford) ET / Offset is 25mm front and 35-40mm rear. Of course, if you increase the rim width you need to take this into account when calculating required off-set. 
k it handles though 
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