Discussion
Like for like they weigh a lot less. And losing unsprung mass is very, very beneficial to handling. Especially on lightweight cars.
Big wheels were typically used on performance cars in days of not so old to allow the fitment of bigger brakes. Which is important on heavy cars but not so much so on lightweight ones.
Then people started to think bigger wheels looked "trick"/"wicked"/"well gud", manufacturers started making and fitting them more which prompted tyre companies to focus on them, which increased weights on vehicles, which necessitated bigger brakes and hence we have a bit of a horrible vicious circle rather than a virtuous one. Also reduced the number of tyre options available (check out the size of wheel on many classic 60s and 70s cars and try pricing up some decent tyres...)
There are, of course, lightweight bigger wheels and tyres these days. BUT they're expensive, and still much heavier than if you were to use the same constructions on a smaller wheel.
If you haven't done so, you should try some tiddlers on a 7...
Big wheels were typically used on performance cars in days of not so old to allow the fitment of bigger brakes. Which is important on heavy cars but not so much so on lightweight ones.
Then people started to think bigger wheels looked "trick"/"wicked"/"well gud", manufacturers started making and fitting them more which prompted tyre companies to focus on them, which increased weights on vehicles, which necessitated bigger brakes and hence we have a bit of a horrible vicious circle rather than a virtuous one. Also reduced the number of tyre options available (check out the size of wheel on many classic 60s and 70s cars and try pricing up some decent tyres...)
There are, of course, lightweight bigger wheels and tyres these days. BUT they're expensive, and still much heavier than if you were to use the same constructions on a smaller wheel.
If you haven't done so, you should try some tiddlers on a 7...
13's are more progressive on the limit, amd give a better ride. Becuase they have more sidewall to give.
There's no weight to a Seven, so do you need low profile tyres?
Have a look at race cars, and see how many use 13's.
Allso, have a look at the size of the sidewalls on an F1 car. Although a F1 car uses the tyres for suspension, as they don't realy have any suspension movement.
13's used to be a no cost option. Are CC charging extra for them now?
There's no weight to a Seven, so do you need low profile tyres?
Have a look at race cars, and see how many use 13's.
Allso, have a look at the size of the sidewalls on an F1 car. Although a F1 car uses the tyres for suspension, as they don't realy have any suspension movement.
13's used to be a no cost option. Are CC charging extra for them now?
Just to add my 2p
I upgraded to 13 inch after 2 years of track using the 15 inch. I think the ultimate grip is similar but the bigger profile of the 13 inch makes them more compliant at the limit and you can push harder with more confidence. They were worth about 2 seconds on my Knockhill lap times.
For road use the benefits are less obvious as the low profile on the 15 inch provide a sharper response than the 13 inch.
I upgraded to 13 inch after 2 years of track using the 15 inch. I think the ultimate grip is similar but the bigger profile of the 13 inch makes them more compliant at the limit and you can push harder with more confidence. They were worth about 2 seconds on my Knockhill lap times.
For road use the benefits are less obvious as the low profile on the 15 inch provide a sharper response than the 13 inch.
Edited by David Long on Friday 25th June 14:07
I got an answer from Andy Noble (Caterham):
'Yes, the 13" are more expensive. Reason being is that we buy less 13" than 15" and that the rear wider tyres are more expensive than the 6" and 7" tyre.'
Btw, have you noticed any difference in cornering, apart from being more progressive. I mean, is the car more understeering or oversteering? I suppose that having a bigger rear tyre means more grip on the rear end and therefore a natural increase in the tendency to understeer when pushed to the limit.
'Yes, the 13" are more expensive. Reason being is that we buy less 13" than 15" and that the rear wider tyres are more expensive than the 6" and 7" tyre.'
Btw, have you noticed any difference in cornering, apart from being more progressive. I mean, is the car more understeering or oversteering? I suppose that having a bigger rear tyre means more grip on the rear end and therefore a natural increase in the tendency to understeer when pushed to the limit.
Elapido said:
I got an answer from Andy Noble (Caterham):
'Yes, the 13" are more expensive. Reason being is that we buy less 13" than 15" and that the rear wider tyres are more expensive than the 6" and 7" tyre.'
Btw, have you noticed any difference in cornering, apart from being more progressive. I mean, is the car more understeering or oversteering? I suppose that having a bigger rear tyre means more grip on the rear end and therefore a natural increase in the tendency to understeer when pushed to the limit.
I find the 175/205 front/rear mix works well on the R400 and gives a good balance when pushing hard. For lower BHP cars, the rears are maybe too wide but it's really a matter of opinion. 'Yes, the 13" are more expensive. Reason being is that we buy less 13" than 15" and that the rear wider tyres are more expensive than the 6" and 7" tyre.'
Btw, have you noticed any difference in cornering, apart from being more progressive. I mean, is the car more understeering or oversteering? I suppose that having a bigger rear tyre means more grip on the rear end and therefore a natural increase in the tendency to understeer when pushed to the limit.
Oversteer and understeer in a Caterham is really down to how you drive it and control the weight transfer. The geometry also plays a much bigger part than the tyres or wheels.
Edited by David Long on Friday 25th June 22:09
Over the years, vwe've had (I think) 7 caterhams. On most, we've ended up playing with them, wether that be simply suspension setup, or more usually changing the anti roll bars, then setting them up. Over a combination of narrow track roadsport, widetrack superlight, and CSR200, the only time we've struggled to get a car handling brilliantly was when it was on 15's. The second you change to 13's, you get much better compliance over bumps, and better stability on quick left-right direction changes.
I have no idea why this would be the case, as we've always been keen cub racers not pro's. However, after the first 15"'d car, with every subsequent one we've simply sold the 15's the week we got the car, then bought 13's and CR500's before even starting to set the car up.
PS - it is common custom for manufacturors to put "must have" options as options. Makes you pay more!
I have no idea why this would be the case, as we've always been keen cub racers not pro's. However, after the first 15"'d car, with every subsequent one we've simply sold the 15's the week we got the car, then bought 13's and CR500's before even starting to set the car up.
PS - it is common custom for manufacturors to put "must have" options as options. Makes you pay more!
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