Larger rims vs higher section tyres

[Petrus]

Fínallt found something from the F1 technicians!!

"The subject of bigger wheels has been raised many times over the last five or eight years," said Mercedes executive technical director Paddy Lowe.

"The broad consensus is that going to bigger wheels is not a good direction. From a grip point of view it's not positive.

"Like for like, such tyres will have a lower grip and the weight will go up considerably, so it's not an attractive direction performance-wise."

As a car corners its tyres deflect a little to keep in contact with the tarmac - stiffer sidewalls will mean less deflection and therefore less contact with the tarmac.

The size of the wheel rims will also increase mass at the hub - it takes more effort to spin the larger mass; also increasing the unsprung weight (https://en.wikipedia.org/wiki/Unsprung_mass)

" The amount of movement, for short bumps, is inversely proportional to the weight - a lighter wheel which readily moves in response to road bumps will have more grip and more constant grip when tracking over an imperfect road."

So it makes sense to keep the rim weight down and the tyre-wall height up from a performance point of view.

[Petrus]

and a like for like test:

https://www.caranddriver.com/features/a15130598/upsized-wheels-tires/

[Petrus]

Bottom line:
If not for looks or a specific purpose; for the road best stick to the OEM rim/tyre size and get the best rubber for the purpose.

[1979scotte]

Bottom line:
If not for looks or a specific purpose; for the road best stick to the OEM rim/tyre size and get the best rubber for the purpose.

It's been said for years.

[Petrus]

It's been said for years.

There is a snag though.
Marketing/fashion have sínce those years gone factory bigger rim/lower section and worse still the néxt step ´up´ is larger overall diameter.

Formula 1 is resisting and sticking to the 13" rims but has for years been under pressure to larger, 18" even, for no other reason than marketing/fashion.

[StuC]

Big wheels = Fashion = tarty!

Understood!!

[Ardent]

I will confess a 2 "looks" good on 17s.

Personally, I felt the driving experience was awful.

For a short period I had two 2s and swapped and changed the wheels around to do direct comparisons.
Which ever car was on the 15 16 set up danced like margot fonteyn.
The 17 set up was more like 7 year old trying to walk in their mams/dads heels.

[Johnny5]

Best tyre size I ever drove on was 205/60 15, on an E36 328i, a 147 mph car.  Nowadays, shopping hatchbacks are on 17s and it only gets much worse from there.  Interestingly, the Toyobaru GT86, which comes on 17s, is available in its native Japan on 16s as standard.  I'll hazard a guess that is the optimum size for maximum grin factor at road speeds.  Why minimum 17s here in the UK?  Bling status and supercool overriding subjective entertainment of the driving dynamics.

[1979scotte]

Best tyre size I ever drove on was 205/60 15, on an E36 328i, a 147 mph car.  Nowadays, shopping hatchbacks are on 17s and it only gets much worse from there.  Interestingly, the Toyobaru GT86, which comes on 17s, is available in its native Japan on 16s as standard.  I'll hazard a guess that is the optimum size for maximum grin factor at road speeds.  Why minimum 17s here in the UK?  Bling status and supercool overriding subjective entertainment of the driving dynamics.

Didn't the gt86 come with rubbish fuel efficient rubber from factory?
Stupid.

[Johnny5]

Didn't the gt86 come with rubbish fuel efficient rubber from factory?
Stupid.

Yeah, I think the aim there, allegedly, was to provide tyres that weren't too grippy to make the fun available at road speeds.  Good concept, but putting better tyres on smaller rims would be an even better idea. 

[Petrus]

Didn't the gt86 come with rubbish fuel efficient rubber from factory?
Stupid.

Well, thát had another reason. Same reason why I stuck with El Cheapo rubber for some months: To learn explore the limits of the car at lower speeds because the rubber lets go at a lower level.
The GT86 is a bit dífferent as that car was conceived as a drift thing for the open road really. Tbh I would stick to n eco rubber on that one too. Maybe not as bad as OEM because you dó want to be able to brake well, but ob that one it would defeat the purpose to go for máx grip rubber.
Nankang NS2R probably.
On the subject though; after market lightweight 16", nót larger.

In Japan the GT86 is also available in a basic version without all of the electronic crap, no airco etc. which the r.o.w. gets standard :-(
It even has steelies as the factory knows they will fit RAYs or Enkeis anyway.

Why not for the row? Because it has a higher list price = more profit in a market which in all honesty ís less street performance oriented. Especially over here in Europe the crap ís a selling point, the practically ís an essential to be able to sell the car to the gf/fiancee/wife. Why else would it have a uni kid seat option!!??
The group of boy racer bachelors with slush funs ís way larger in Japan than in the row, especially Europe.
Thus Toyota sticks to unification of the model which is for a niche market anyway.

[Petrus]

Yeah, I think the aim there, allegedly, was to provide tyres that weren't too grippy to make the fun available at road speeds.  Good concept, but putting better tyres on smaller rims would be an even better idea.

The problem is brake distance.
For fún, 185/55 all round on  6J 15" would be better still but that would seriouly add brake distance.

The larger eco rubber is a marketing/safety compromise leaving the fun aspect intact.

The braking distance is a real bummer as it is thé most important factor on the road in mý opinion.
We all know you can gain/drop 10 even 20% there!! That is easily a meter or way more from 100 km/h.
My current rubber adds a third!!!! over AD08Rs on a wet road, 15+ meters 
Scary idea no?!
Larger rims loose out there too. Do nót look better when half a meter under a lorry instead of just not. It amazes me that this is never ever mentioned by motoring journalists.

[tom256]

Not always small rims are better:

https://grassrootsmotorsports.com/articles/do-larger-wheels-and-tires-really-make-you-faster/

[Petrus]

Not always small rims are better:

https://grassrootsmotorsports.com/articles/do-larger-wheels-and-tires-really-make-you-faster/

Only if you can live, literally, with a longer brake distance.
On the public road lap times are slightly less important than brake distance no?!

Ofcourse everything has it´s own set of inherent advantages and drawbacks: Take your pick.

Just be aware that bigger is nót always better.

[Ardent]

So so true. 

[Petrus]

The larger rim diameter syndrom stems from looks as well as the Nordschleife syndrom; Nürburgring lap times chasing by marketing departments of the industry and revered by the motoring press.
Loer section tyres with more wall stifness give more exactness at the price of less compliance and more weight. The compliance is a non issue with racing rubber on a smooth race track surface. The cost of the extra weight is limited on the Nordschleife bcause it is by and large a high speed track.
On the real world roads however the two combined result in much less road contact. Not something you want when emergency braking. You curse those say two meters lost when surprised by a lorry only ónce...

For those who find it hard to understand:
A long time ago reverent Dunlop re-invented neumatic tyres for his bicycle racing son. The superior compliance won the day.
The latest generation of hypersports cars come on 30 section rubber. That is only a small step away from bonding the rubber directly to the rim again. This does a power of no good to real world roadworthyness and they only get away with it because of the high tech, high cost, highly special suspension systems which would work even better with a bit better compliance of the tyres.
I have never been a fan of the Top Gear comedy show and less so of the current farce but James May was spot on with his Nordschleife peeve.

[shnazzle]

So so true. 

LOL!
So, what you're saying Jason is that you're maybe not as nimble as your larger counterparts but by jingo can you stop quickly and offer a comfortable ride

[Ardent]

Def. Built for comfort.

[silversprint]

 Total Tread Surface Area (TTSA)
Contact patch shape.
Size of brake discs

Best article on choosing wheels and tires is this one.

https://motoiq.com/how-to-properly-select-and-size-tires-for-performance/3