Porsche 991 wheels - How big is TOO big?
Discussion
So, can a wheel be too big?
The answer has to be 'yes' of course as the wheel cannot be bigger than the car! We have seen wheels growing 1 inch with every new model of the 911.
This cannot be sustained obviously and there are many views on here that the new 991 has gone too far already.
So what size should wheels be ideally then? Are Porsche going bigger for looks alone? Or is there a genuine dynamic advantage?
F1 wheels are tiny.
MTR
The answer has to be 'yes' of course as the wheel cannot be bigger than the car! We have seen wheels growing 1 inch with every new model of the 911.
This cannot be sustained obviously and there are many views on here that the new 991 has gone too far already.
So what size should wheels be ideally then? Are Porsche going bigger for looks alone? Or is there a genuine dynamic advantage?
F1 wheels are tiny.
MTR
Edited by mollytherocker on Tuesday 15th November 22:16
F1 tyres are huge though and form a good part of the suspension.
However, I agree about the race for bigger wheels - I think the 996 18's always looked big enough? My current cars have 19 and 20" wheels and the replacement tyre costs are ridiculous.
I had to change a 20" wheel in France this summer and they are a right handful to deal with on the hard shoulder!!
Sensible wheel sizes and associated rubber costs will definitely factor into future purchase decisions.
However, I agree about the race for bigger wheels - I think the 996 18's always looked big enough? My current cars have 19 and 20" wheels and the replacement tyre costs are ridiculous.
I had to change a 20" wheel in France this summer and they are a right handful to deal with on the hard shoulder!!
Sensible wheel sizes and associated rubber costs will definitely factor into future purchase decisions.
mollytherocker said:
Wills2 said:
I think 18-19" is more than big enough, rubberband tyres on 20" have to be vunerable on the UK's pothole d roads.
Why would a larger diameter be more vunerable to pot holes? Surely, they would be less vunerable?MTR
A few friends made the mistake of getting silly sized wheels on their Range Rovers and all of them buckled wheels and went back to the standard range rover 19" rim with deeper tyres with no issues.
All IMHO could be nonsense.
Trev450 said:
The reduced height of the tyre sidewall with larger diameter rims certainly makes them more prone to pothole damage and as already mentioned, gives a much less compliant ride. And thats without the additional unsprung weight to take into consideration.
Fair enough. Its not the diameter 'per se' thats the problem, but the resulting reduced tyre side wall.Extra unsprung weight is a good point!
MTR
Big wheels have two benefits - looking good and housing larger brakes. Everything else is a downside, especially weight and the fact that the larger the wheel the farther the majority of that weight is from the centre of rotation so the more inertia there is.
Swap from 18s to 16s on a 993 and you will marvel at the improved steering feel, better ride and generally more delicate driving experience, but try stopping a big hefty 991 on brakes that fit under 16s and you'll be missing those big wheels all the way through the hedge.
Swap from 18s to 16s on a 993 and you will marvel at the improved steering feel, better ride and generally more delicate driving experience, but try stopping a big hefty 991 on brakes that fit under 16s and you'll be missing those big wheels all the way through the hedge.
MrCooke said:
Big wheels have two benefits - looking good and housing larger brakes.
Make that one [theoretical] benefit as looks are at best subjective and a skilfull designer can work around the issue...For example, does anyone think that the original Countach looks anyhting other than well shod on its 14" rims?
I recall a design programme on the BBC where Peter Stevens (ISTR?) showed us what Ferrari were doing when they put 18" wheels on the 355. It made the body of the car appear to shrink as we all have a perception of what size wheels should be and when you see a 'well designed' car on big wheels, you get the impression that the wheels just 'look right' but that the car itself appears smaller than it is.
Regarding the size issue.. 'Big brakes' are an advantage but whereas increasing diameter is 'the best' way to increase performance as the force is multiplied by moving the pads out, the alternative is to make the discs thicker so that they can deal with the heat better. I don't have the figures to hand but would not surprise me if the discs on the 993 were thicker than the discs that we see these days. Certainly F1 disc are mega thick (2"?).
Another issue is that we all know that overall braking performance is heavily dependent on the performance of the front brakes due to weight transfer. Consequently, rear brakes are often that bit smaller/less substantial as they have less work to do. However, what I have never seen is a car with smaller diameter rear wheels...
Logically, this should be possible and the increased sidewall depth that could be obtained would almost certainly benefit traction in a RWD car (just look at dragsters and F1 cars again).
Aesthetically, you would have to say that putting smaller diameter rims on the rear axle of car could look rather odd so for that resason alone, it is perhaps unlikey, but it bugs me whenever I see that larger diameter wheels have been fitted on the rear of a car as I cannot believe that there is a sound engineering reason to do this - only a styling issue that could have been addressed in other ways... Rant over!
mollytherocker said:
Massive brakes are not necessary either. And even if they were, you can put them inboard of the wheel.
Again, F1 brakes are not very big are they.
But 911s don't have inboard brakes and F1 cars weigh less than half what a 911 does and have brakes made from unobtanium which isn't practical for a road car. I'm not sure of your point?Again, F1 brakes are not very big are they.
Interesting that the 991 is close to the weight of a 993 C2, I hadn't realised that. That's a very significant saving over the 997.
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