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Discussion
I'm not sure I understand this whole thing in making your cars performance worse than standard. If you're wanting fun driving (and you consider the car moving about on big sidewalls, and low grip levels as fun - I don't), the Boxster/Cayman is the wrong tool for the job. Better off in an Elise, MR2, VX220, Cappuccino, etc...
Genuine question, rather than branded smaller tyres, why not budget tyres in the standard size on the rears? You'll get the same result or am I missing something?
Genuine question, rather than branded smaller tyres, why not budget tyres in the standard size on the rears? You'll get the same result or am I missing something?
anonymous said:
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In the simplest sense it is correct. Assuming constant type pressures, to support the same mass of vehicle requires a constant contact patch area.
The contact patch will increase until the point at which the area of tyre on the ground, multiplied by the pressure, matches force required to support the vehicle.
With a narrower tyre, that same contact patch area will look longer and thinner than a wide tyre.
Obviously starts to get complicated with weight transfer, tyre deformation, heat generation/dissipation etc. which all effect grip (and are all beyond my levels of knowledge), but the actual area of tyre on the ground is purely a function of weight and tyre pressure
IcedKiwi said:
In the simplest sense it is correct.
Assuming constant type pressures, to support the same mass of vehicle requires a constant contact patch area.
The contact patch will increase until the point at which the area of tyre on the ground, multiplied by the pressure, matches force required to support the vehicle.
With a narrower tyre, that same contact patch area will look longer and thinner than a wide tyre.
Obviously starts to get complicated with weight transfer, tyre deformation, heat generation/dissipation etc. which all effect grip (and are all beyond my levels of knowledge), but the actual area of tyre on the ground is purely a function of weight and tyre pressure
Great post Assuming constant type pressures, to support the same mass of vehicle requires a constant contact patch area.
The contact patch will increase until the point at which the area of tyre on the ground, multiplied by the pressure, matches force required to support the vehicle.
With a narrower tyre, that same contact patch area will look longer and thinner than a wide tyre.
Obviously starts to get complicated with weight transfer, tyre deformation, heat generation/dissipation etc. which all effect grip (and are all beyond my levels of knowledge), but the actual area of tyre on the ground is purely a function of weight and tyre pressure
anonymous said:
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You're going to have to address the point about budget tyres (on the rear) as I don't understand why that's silly. It seems you derive driving pleasure from being on the edge of the available grip. You've mentioned that smaller tyres bring the grip level down and that makes it a more interesting driving proposition, a pair of Triangle tyres would also achieve this. I find it fun to go around say an empty roundabout as fast as I can, where the available grip is so good you are practically hanging on to the steering wheel. I come off the roundabout impressed with the speed I can carry and that's enjoyable. I have a grin from ear to ear, that's what a sports car is about in my opinion.
Escy said:
I'm not sure I understand this whole thing in making your cars performance worse than standard. If you're wanting fun driving (and you consider the car moving about on big sidewalls, and low grip levels as fun - I don't), the Boxster/Cayman is the wrong tool for the job. Better off in an Elise, MR2, VX220, Cappuccino, etc...
Genuine question, rather than branded smaller tyres, why not budget tyres in the standard size on the rears? You'll get the same result or am I missing something?
Worse is a relative term. And why is a Boxster wrong for the job?Genuine question, rather than branded smaller tyres, why not budget tyres in the standard size on the rears? You'll get the same result or am I missing something?
Granted I've never tracked a car but never did I once think my Boxster on 17's could do with more grip on the road.
You'd have to be driving in a pretty reckless manner for lack of grip to be an issue on the road.
anonymous said:
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Hang on, I didn't mention wheel size. John asked about new tyres on his 17's you've suggested smaller width rear tyres. I'd like to know why you'd suggested narrower width tyres rather than a brand simply offering less grip? The end result is the same as far as I can tell? 
Per previous, I'm fully onboard with the arguments against big wheels and rubber but there are some practical limitations, again being ignored by people on this thread.
For example, I've been trying to track down some Michelin PS4s for one of my cars (Michelin appear to have stopped making the standard size) so I've spoken to various parties over the last week on the subject, including hypotheticals of what can be fitted to what.
Michelin's own people won't talk about any tyres that are outside the envelope of manufacturer's recommended specifications, citing safety and their liabilities. My local tyre fitter won't fit one, even if a waiver were signed. And my insurer won't cover the car.
Other than that, crack on.
For example, I've been trying to track down some Michelin PS4s for one of my cars (Michelin appear to have stopped making the standard size) so I've spoken to various parties over the last week on the subject, including hypotheticals of what can be fitted to what.
Michelin's own people won't talk about any tyres that are outside the envelope of manufacturer's recommended specifications, citing safety and their liabilities. My local tyre fitter won't fit one, even if a waiver were signed. And my insurer won't cover the car.
Other than that, crack on.
Patrick Bateman said:
Worse is a relative term. And why is a Boxster wrong for the job?
You'd have to be driving in a pretty reckless manner for lack of grip to be an issue on the road.
The advice was to fit narrower tyres than originally supplied on the car, I'd suggest that's making it worse.You'd have to be driving in a pretty reckless manner for lack of grip to be an issue on the road.
I agree on the reckless driving, that video with the Elise was daft, if you want to drive your car like they did on a road you'd be an idiot and a danger to others. I'm not the one suggesting lowering the grip levels below what Porsche intended to make the car more fun.
anonymous said:
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Hanging on to the steering wheel if a figure of speech, not literally. Of course you know that.It's ironic you're promoting fitting narrower tyres to lower a cars grip levels so you can feel it move around more on the road yet I'm an accident waiting to happen. It's also ironic that the guy made his Lotus slower with those modifications yet still managed to spin it off the road with the new spec. It might be more fun but so is a set of tea trays under the back wheels of a Corsa or a set of space savers on an AMG Merc.
I notice you've swerved my hypothetical question on your preferred narrower tyres vs budgets 3 times now. I'll answer it for you and you can correct me if I'm wrong. Both will lower the grip levels which is what you say the car benefits from but suggesting narrower tyres sounds better than saying run a set of Linglongs to make your car more fun. That's basically the narrative you've been pushing for the last few pages. Correct me if I'm wrong...
anonymous said:
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It's a good enough assumption to be starting with. Wider tyres = bigger contact patch is just wrong. More lateral grip maybe, but also maybe a faster transition between grip and no grip.. Anyway, I've BTDT with 225 section tyres all round on a 986S, didn't die at Donington, Curborough, Spa, Cadwell etc.. anonymous said:
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I have had tyre fitters refuse to fit odd or different tyres to alloys too so I've gone home and removed the alloys and then transported them back to the same fitter in the boot of another car and then they will comply with the request. You just need a big estate or similar. Moo and I have discussed this before and I think the crux of the tyre grip thing is you need a tyre which has good feel and good tyre wall flex and a good balance of grip which reduces in a good way as the tyre deforms .... in a good way. I have used the word good several times to emphasise it's not about lower grip it's about the way in which the grip changes as the tyre moves towards its limits. Generally this implies you need a good tyre which has been well designed. Not just some cheap rubbish tyre which has no grip.
Of course a cheap rubbish tyre with less grip would add some fun to a car with too much grip but may remove some feel and remove some finesse and reduce stopping distances.
So even though we are looking for ultimately less grip it is the way in which it is achieved. A fat 18 inch cheap tyre may just grip grip grip and then fall off a cliff. That's not fun unless you like going on roller coasters without the seatbelt on. You want the tyre to give you some clues that its starting to deform and therefore that the grip is starting to reduce in a nice steady controllable and understandable way.
Of course a cheap rubbish tyre with less grip would add some fun to a car with too much grip but may remove some feel and remove some finesse and reduce stopping distances.
So even though we are looking for ultimately less grip it is the way in which it is achieved. A fat 18 inch cheap tyre may just grip grip grip and then fall off a cliff. That's not fun unless you like going on roller coasters without the seatbelt on. You want the tyre to give you some clues that its starting to deform and therefore that the grip is starting to reduce in a nice steady controllable and understandable way.
Escy said:
The advice was to fit narrower tyres than originally supplied on the car, I'd suggest that's making it worse.
I agree on the reckless driving, that video with the Elise was daft, if you want to drive your car like they did on a road you'd be an idiot and a danger to others. I'm not the one suggesting lowering the grip levels below what Porsche intended to make the car more fun.
Only if you think less grip automatically makes a car worse. We're not talking about turning the thing into something comparable with using slicks in the pouring rain.I agree on the reckless driving, that video with the Elise was daft, if you want to drive your car like they did on a road you'd be an idiot and a danger to others. I'm not the one suggesting lowering the grip levels below what Porsche intended to make the car more fun.
And I'm talking about swapping out 18 or 19 inch wheels down to standard Porsche 17's here, it's what I did and it's not exactly chucking space savers on the back, is it?
Also, crap budget tyres aren't going to behave in near the same manner as premium tyres for a given size.
ATM said:
Moo and I have discussed this before and I think the crux of the tyre grip thing is you need a tyre which has good feel and good tyre wall flex and a good balance of grip which reduces in a good way as the tyre deforms .... in a good way. I have used the word good several times to emphasise it's not about lower grip it's about the way in which the grip changes as the tyre moves towards its limits. Generally this implies you need a good tyre which has been well designed. Not just some cheap rubbish tyre which has no grip.
Of course a cheap rubbish tyre with less grip would add some fun to a car with too much grip but may remove some feel and remove some finesse and reduce stopping distances.
So even though we are looking for ultimately less grip it is the way in which it is achieved. A fat 18 inch cheap tyre may just grip grip grip and then fall off a cliff. That's not fun unless you like going on roller coasters without the seatbelt on. You want the tyre to give you some clues that its starting to deform and therefore that the grip is starting to reduce in a nice steady controllable and understandable way.
Hitting the nail on the head.Of course a cheap rubbish tyre with less grip would add some fun to a car with too much grip but may remove some feel and remove some finesse and reduce stopping distances.
So even though we are looking for ultimately less grip it is the way in which it is achieved. A fat 18 inch cheap tyre may just grip grip grip and then fall off a cliff. That's not fun unless you like going on roller coasters without the seatbelt on. You want the tyre to give you some clues that its starting to deform and therefore that the grip is starting to reduce in a nice steady controllable and understandable way.
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