Disadvantages of bigger diameter & lower profile (Heavier wheels)
- Thread starter 924Srr27l
- Start date
924Srr27l
New member
Eldavo said:
Yes true the market caters and offers more choice for even bigger diameters today than 5 years ago, not to mention 10 !
But 205/55/16 & 225/50/16 sizes are still available in "N" (Porsche approved) like:
Michelin Exalto, Bridgestone S02 & Continental, also many
other major brands in Non N rated like Pirelli and Goodyear...etc..
R
Your car is a light road car on skinny tyres though on a cold/damp track.
I've got KW Clubsport suspension with race geometry, RE top mounts, monoball castor mounts, polybushed syspension, semi slick tyres as well as a big chunk more power and torque - my tyres get worked.
My personal experience tells me that i will melt road tyres on a warm trackday. I can spin up the 255 rears in third if I'm really on it - and 4th in the damp is a bit worrying when you don't expect it.
I've got KW Clubsport suspension with race geometry, RE top mounts, monoball castor mounts, polybushed syspension, semi slick tyres as well as a big chunk more power and torque - my tyres get worked.
My personal experience tells me that i will melt road tyres on a warm trackday. I can spin up the 255 rears in third if I'm really on it - and 4th in the damp is a bit worrying when you don't expect it.
924Srr27l
New member
Eldavo said:
Yeah the Pilot Sports were well worked rising 5psi, they would of had more heat had it of been totally dry and Hot etc.. but they as all higher profile tyre sizes have a high treadwear durable rating (320) to cope with the heat.
I did take my 8x16" Cup set of wheels & R888's (100 Treadwear) but never felt like putting them on as the track was November damp and greasy.
Even in these conditions I never had any wheelspin anywhere but the 55 series narrow tyres assist with this giving better traction and braking footprint compared to a 255/40/17. The Torque per weight is more than a stock 952 & 968 so it's not like it's not got much waft, the Wavetrac LSD obviously plays it part. Don't forget also the moment the throttle butterfly is opened I have instant torque and response, no LAG !
My 190Lbs front 2.25 ID Race coils are not high in rate for Racing, but probably similar to KW Road kit for a 952 which is (35%+ heavier), the rear Torsion bars are Hollow 27mm, the rear trailing arms Sport Shore hardness rubber both from Elephant Racing and the Torsion carrier Powerflex.
The ARB's are also large against the weight (1040kg) front (944 turbo) 26.8 Rear / 16mm but with OE Rubber Bushes and Front bracebars
The geo and Corner weights have been set by a Race team and are in between a Race and road set up
It wasn't silly stiff on track but certainly too soft should I decide to race it.
R
924Srr27l
New member
A Slight Variation on this Wheel & Tyre Theme (Bigger & Wider) is next years F1 Regs are up for a
big change in Wheel and Tyre width and also more Aerodynamic downforce, which they predict these new car's will be 1-5
seconds faster in lap times compared to this year...
On very fast (straights) tracks like Monza it's said that such is the extra Drag of the Wider wheels lap times
will not be that much quicker than this year, but on other slower and tighter circuits the extra downforce and
rubber molecules will provide faster corner speeds.
This Picture clearly illustrates, a lower narrow chassis with 4 HUGE lumps hanging off it! No wonder the Drag is a big factor.
http://a2.espncdn.com/combiner/i?img=%2Fphoto%2F2016%2F0907%2Fr122861_1296x729_16%2D9.jpg&w=570
R
big change in Wheel and Tyre width and also more Aerodynamic downforce, which they predict these new car's will be 1-5
seconds faster in lap times compared to this year...
On very fast (straights) tracks like Monza it's said that such is the extra Drag of the Wider wheels lap times
will not be that much quicker than this year, but on other slower and tighter circuits the extra downforce and
rubber molecules will provide faster corner speeds.
This Picture clearly illustrates, a lower narrow chassis with 4 HUGE lumps hanging off it! No wonder the Drag is a big factor.
http://a2.espncdn.com/combiner/i?img=%2Fphoto%2F2016%2F0907%2Fr122861_1296x729_16%2D9.jpg&w=570
R
924Srr27l
New member
edh said:
Have you ever been to Santa Pod or seen the size of the Tyre Sidewalls?
They want maximum Traction (No Wheel spin) Tall sidewalls give a longer (Front to rear) contact
with the road surface, if they fitted wide low profiles they will sit there and spin......
Circuit Racing isn't a drag race as such (It is between each corner) but involves cornering at forces
as high a possible (Higher corner speeds) and a narrow tyre and high sidewall (as the dragster aove)
would overheat for Racing Circuit use because the LONG patch does not "Cool" the tyres very well
and every revolution isn't enough exposure enough air to cool it.
A wide Tyre with a low profile sidewall has a wide thin patch across which cools quicker but it's not as good front to rear for
(Braking & Acceleration) hence the higher profile tyres are better for traction (Acceleration & Braking)
But the downside of the taller sidewall profile is it can overheat, so it has to have a Higher Rubber compound
(The America's call this treadwear) to cope with the heat.
Your other extreme is the Sport of DRIFTING........the Objective to loose grip and hold a long slide..
So HUGE Rims, & TINY tyre Profiles are the best for this, and higher tyre pressures.
R
edh
New member
I understand that wider tyres have a narrower contact patch. I have no interest in drag racing (or drifting).
944 S2 / Turbo (and 968) racers appear to choose 17" rims over 16", and 255 section tyres over 205's. There must be some reason for this.. You've suggested that any temporary advantage is soon overcome by other factors (i.e. it's worse in practice)
Higher treadwear / harder rubber doesn't always last longer on circuits. In my experience some road tyres degrade and wear very quickly on hot days. Some softer tyres (AD08's for example) fare much better.
944 S2 / Turbo (and 968) racers appear to choose 17" rims over 16", and 255 section tyres over 205's. There must be some reason for this.. You've suggested that any temporary advantage is soon overcome by other factors (i.e. it's worse in practice)
Higher treadwear / harder rubber doesn't always last longer on circuits. In my experience some road tyres degrade and wear very quickly on hot days. Some softer tyres (AD08's for example) fare much better.
924Srr27l
New member
edh said:
Yes but you've not taken on board what I've just explained? The Drag Racing and Drifting is a wide illustration of each Sport
and what each Tyre Profiles characteristics are for each catorgary.
You understand Traction under acceleration is so much better with a high tall sidewall yes?
And that a Slim small profile loses grip quicker like the Drifter yes?
If there's always one thing that gets mentioned and "in the way" it's the RACTRACK mentality suggestions....
The Whole Road tuning Industry pushes the Racebred marketing and it's taken on board and digested too much
so people get blinkered and think whats good for Circuit racing is good for Public Roads! it Isn't.
This thread "Disadvantages of bigger diameter & lower profile (Heavier wheels)" is aimed at ROAD use
It can and is relevant for Racing too (Lightweight Wheels produce faster laptimes) but the Tyre situation
is not as clear cut as explained before they have a massive issue with
"HEAT"
Hence why Racing tyres, Slicks and even Semi Road legal tyres like R888's etc...have STIFFER Sidewalls, compared to ROAD
tyres because SOFT Sidewalls flex more give a bigger contact patch and overheat when used on a racetrack.
I have R888#s in the same size as my Road set 205/55/16, the Compound is 3 times softer and stickier and the sidewalls
much stiffer to cope with the heat which my Road Pilot sports would struggle with on a Dry track in Hot conditions etc..
However there were Ideal on a Damp drying Oulton Park last Friday, and they are also ideal on the public roads as they have
a hard compound which means I can drive the car hard for many hours without wearing strips off them, and needing to replace them every week!
R
924Srr27l
New member
edh said:
Your getting better! but I think from the above you're now thinking about Road Use which I was also.
So to summarise, the track and it's abuse to a car's tyre's has a serious amount of HEAT generated from the
criteria to push the limits of adhesion in all 3 planes (acceleration / cornering & braking) far more than is possible on the public roads.
So wider contact patches deal better with this heat on a Race track and also smaller sidewalls, and stiffer sidewalls..
Bigger profiled Racing Tyres are still better on the track than any Road version EG: 205/55/16
But bigger sidewall Profiles on the ROAD are really good because the compound is much harder than Race tyres, and hence
they do not have HEAT issues when pushing a car on the road.
Bigger profiles on the road are also good because the wheel is smaller and lighter, this then goes into the Unsprung weight subject etc...
Bigger Profiles have better Traction and Braking grip on the ROAD.
So whats good for the track is not always good for the road, but Wide ass Tyres and Rims sell well especially when the marketing
is pointing towards the racetrack, and surprisingly not many people can or won't? complain their car is slower and handles worst when they upgrade to bigger and wider wheels & tyres where as in fact they have gone slower... [&:]
The very slightly higher COF is not enough to outweigh the benefits that lighter wheels have and bigger sidewalls.
The Motor Industry has gone down a the Electronic route of features where modern cars compared to the 40yr old Porsche transaxle have so many driver aids..these all get round the traction losses (Wheelspin) and locking brake issues (ABS) not to mention the Stability control etc..Most people have no idea or could feel all these sensors are working within milliseconds to avoid
a major accident and hence car's have become less involving but safer.
R
edh
New member
924Srr27l said:
Not really, just saying how pointless this is becoming. You said that your wheels were better on track, I suggested not..
As I've said before, I like the way lighter wheels drive on a 944 on the road. It's the feel more than anything. As for your claims above, I think you're way over the top, again as I pointed out earlier in this thread.
924Srr27l
New member
Not Really, oh dear! Pointless ? Charming! that's nothing more than plain arrogance thanks.
If your interested and willing to learn fine, but just because you can't or don't want to understand it doesn't mean you have to undermine the topic.
You're not the first, or will you be the last to fail to grasp it...
This is not a Religion that you either follow or don;t ! It's factual Pneumatic Tyre and handling traits, Physics and maths not some claims I've made up!
If you followed this better , you'd of noticed I said my 55 series Tyres were good on track (No wheelspin or locking), Not the wheels, even though they also were good because they are very light.
Had it of been a Summer's day the higher cornering speed (And HEAT) on the Road tyres would of been poor, and I would of fitted my R888 and heavier Cup Wheel Set.
I would estimate the difference in laptime in dry & Hot conditions between the 7x16" road & 8x16" Track set could be 15 +seconds quicker a lap. [
]R
Yeah Ed, you obviously know nothing and I have no idea how you coped in life never mind on a track to now.
Good job this expert has appeared to educate you or you'd never learn.
Btw 924bore - my tongue is firmly in my cheek, suggest you lighten up a bit. I saw a quote recently that said "Religion is like a penis. It's fine to have one and be proud of it but you don't need to wave it around in public or try and stick it down my throat"
Your car is obviously your religion. Stick a build thread up and people can ask you questions and you can answer in epic monologues on there rather than turning every thread into "have I told you about MY car".
Im off for some wine - have a good weekend all.
Good job this expert has appeared to educate you or you'd never learn.
Btw 924bore - my tongue is firmly in my cheek, suggest you lighten up a bit. I saw a quote recently that said "Religion is like a penis. It's fine to have one and be proud of it but you don't need to wave it around in public or try and stick it down my throat"
Your car is obviously your religion. Stick a build thread up and people can ask you questions and you can answer in epic monologues on there rather than turning every thread into "have I told you about MY car".
Im off for some wine - have a good weekend all.
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