mmm-five wrote: ↑Thu Mar 21, 2019 4:02 pmOwners are free to fit what they want, as long as it meets or exceeds the OE spec.
I was just pointing out anything that might contribute to the OPs ‘harsh ride’.
You don’t have to find an 88 rating, but on the other hand you also don’t need to find the stiffest tyre you can find. There are plenty on non-XL tyres around - im sure you know a higher load rating does not make it an XL tyre - only the labelling will tell you that.
It might be more common to find XL (extra load) now, but XL tends to be for heavier cars, not specifically sportier cars, and XL has nothing to do with being a new or old design, so I’ve no idea where you’ve got that from.
Too high a rating and you may get more understeer and a twitcher ride/tramlining.
When I bought my last set of Supersports for the Z4M the rears were available in 97 or 101 ratings and the front were available in 91 or 95 ratings. Both meet/exceed what is specified for the car (91 front / 95 rear), yet only one of them is XL (the 101) - and that was intended for a mich heavier Mercedes saloon.
Maybe they’re making everything XL now as a marketing exercise - or just because cars are becoming a bit heavier
Perhaps it is, but I was just stating the newer tyre releases, in 225/40/18 at least, all seem to be a 92 load rating which is XL, whereas the only tyres in 88 load are the older ones (i.e. Goodyear haven't released an AS3/AS5 in 88 load, only 92. Same as the Michelin PS4 etc)
It's also very dependant on tyre size. The rears on mine are 245/40 (so 10mm narrower than the M) and a load rating of 97. This is XL in that size, yet up the tread profile 10mm and it becomes the normal tyre. So the load ratings on my car right now are 92/97, both of which are classed as XL, yet they're nearly identical to the M 'non-xl' spec.
Take this extract from an article on the subject:
The advantages of reinforced tyres resulting from their increased load capacity are:
When normal and reinforced tyres are used in the same way, the latter will last longer. XL tyres can travel for a greater total distance without suffering internal damage, even when under intensive use. This applies as long as the vehicle manufacturer’s recommended pressure is being adhered to.
Reinforcement of the tyre improves resistance to mechanical damage caused by, for example, driving at high speeds into the curb.
Better traction and adhesion properties. The tyre’s greater rigidity ensures stability, more effective transmission of the vehicle’s power to the road surface, better handling on corners, a faster reaction to turns and a greater resistance to additional loads and forces (acceleration, braking, centrifugal forces on turns).
Of course, there is no such thing as a perfect tyre. All models are a designed and calculated compromise between various parameters and this still applies to reinforced tyres. The more important drawbacks to reinforced tyres are:
Higher noise levels. The tyre certification requirements permit reinforced tyres to produce 1 dB (decibel) more noise than normal tyres.
The use of reinforcement may involve increasing the thickness of the face (under the tread) and shoulder of the tyre. This, in turn, can cause increased rolling resistance and greater fuel consumption.
Reinforcement usually involves an increase in the tyre’s weight and mass, which again leads to higher fuel consumption.
Modifications may lead to a lowering of driving comfort, when compared to using normal tyres, although such differences will be minimal and rarely felt by the driver.
So basically, a stiffer tyre improves the driving dynamics of a sports car by ensuring the tyre makes better contact, at the price of a bit more noise and a bit more resistance - hardly elements considered when choosing UHP tyres for a sports car. I'd also expect you'd have to be a pretty skilled and experienced driver to notice the difference in a tyre thats a few hundred grams heavier, hell my wheels are about 5kg lighter each than the 108s it had on and the difference is negligible.
