KEI 17" Wheels on a Chim
Discussion
Hi everyone. I'm new here, just about to buy my first TVR ('96 Chimaera 4.0)
I love the styling of the Chim but feel it could do with some better (bigger) wheels. I know the general concensus (bigger the wheel, worse the ride, poorer the handling) as I've been checking through the forum pages. 17" are considered the max and that's fine - I'm no Max Power reader!
Just want your thoughts on these
http://cgi.ebay.co.uk/17x7-Kei-Racing-Force-10-All...
they're by KEI Racing and have the 4-stud fitting. One piece Aluminium and will take W-Rated Avon ZZ3T at 205/40.
Will they fit the 4-stud Chim hubs and what's this offset stuff all about?
Any advice on this much appreciated!
DB
I love the styling of the Chim but feel it could do with some better (bigger) wheels. I know the general concensus (bigger the wheel, worse the ride, poorer the handling) as I've been checking through the forum pages. 17" are considered the max and that's fine - I'm no Max Power reader!
Just want your thoughts on these
http://cgi.ebay.co.uk/17x7-Kei-Racing-Force-10-All...
they're by KEI Racing and have the 4-stud fitting. One piece Aluminium and will take W-Rated Avon ZZ3T at 205/40.
Will they fit the 4-stud Chim hubs and what's this offset stuff all about?
Any advice on this much appreciated!
DB
7" rear is fine for a 225 width tyre, but no more. So okay for a Chim 400.
Offset will depend on the width of the rim. Standard front is 7" width with offset ET25, rear 7.5" with ET33.
If you go for 17x7 all round (max 225 width rear tyre), then offset needs to be ET25 all round. For 17x7.5 all round, you need offest of ET33 all round, though ET33 is very hard to find so get close to is (ET35 is more common)
The wheels in the add may be 4 stud, but the stud pattern is wrong. Needs to be PCD 108 - the add is 100/114.3.
I've been looking for wheels for the best part of two years and to the best of my knowledge KEI do not make any wheels with the correct PCD and/or offset, which is a real shame cos some of their wheels are fantastic
These links may be useful:
Article on my blog about wheels
Offset calculator
Offset will depend on the width of the rim. Standard front is 7" width with offset ET25, rear 7.5" with ET33.
If you go for 17x7 all round (max 225 width rear tyre), then offset needs to be ET25 all round. For 17x7.5 all round, you need offest of ET33 all round, though ET33 is very hard to find so get close to is (ET35 is more common)
The wheels in the add may be 4 stud, but the stud pattern is wrong. Needs to be PCD 108 - the add is 100/114.3.
I've been looking for wheels for the best part of two years and to the best of my knowledge KEI do not make any wheels with the correct PCD and/or offset, which is a real shame cos some of their wheels are fantastic
These links may be useful:
Article on my blog about wheels
Offset calculator
Also, check out Rochford Tyres. Probably a bit far from you, but their website is very good and you can search for wheels with various offset. Also, if you just browse the range of wheels, if you select a particular wheel, it will show the sizes/PCDs/offsets, so could be useful in your quest to find wheels!
The offset is the hardest thing to find - i dont know why manufacturers dont list this on their websites
The offset is the hardest thing to find - i dont know why manufacturers dont list this on their websites
What are your requirements? Looks, comfort, performance?
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; unless 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 was inch front, inch and a quarter rear. Wheel spacers can only reduce this ET value irrespective of the wheel diameter.
We also know that if a car was set up for one wheel size then by increasing the wheel diameter, keeping the same rim and tyre widths and the same rolling radius then the matematical advantages are not as much as the disadvantages, even after minimising them by adjusting the suspension set-up; as long as the car's weight and cornering speed are not enough to mean that the tyre rolls onto its sidewall causing sidewall scrub during cornering.
The real world isn't always as clear though. For the Griff/Chim cars it appears to be simple: if you fit 16" or 17" wheels all round then this allows you to fit bigger front brakes, higher performance tyres such as GSD3s, and rims usually more suited to the tyre widths;this appears to have been shown by quite a few to outweigh the disadvantages.
Your choice should be from the roads that you use, your driving style and your preferences.
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; unless 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 was inch front, inch and a quarter rear. Wheel spacers can only reduce this ET value irrespective of the wheel diameter.
We also know that if a car was set up for one wheel size then by increasing the wheel diameter, keeping the same rim and tyre widths and the same rolling radius then the matematical advantages are not as much as the disadvantages, even after minimising them by adjusting the suspension set-up; as long as the car's weight and cornering speed are not enough to mean that the tyre rolls onto its sidewall causing sidewall scrub during cornering.
The real world isn't always as clear though. For the Griff/Chim cars it appears to be simple: if you fit 16" or 17" wheels all round then this allows you to fit bigger front brakes, higher performance tyres such as GSD3s, and rims usually more suited to the tyre widths;this appears to have been shown by quite a few to outweigh the disadvantages.
Your choice should be from the roads that you use, your driving style and your preferences.
Thanks very much for your replies and help on this matter. After considering all points, I've decided to go for the SP12's on Toyo T1's offered by Silverstone Performance with correct offsets front and rear that they specifically supply for the Chim. They don't look as good as the KEI but handling and ride are a factor that need consideration.
Thanks again everyone.
DB
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