imitek

Specificly between a set of 17" and 19" Rim
Can u please Explain why smaller rim is better
Also the effect of the 19" rim with lower profile tyre on a track compared to
17"rim with low profile tyre same raito so i have an idea

I ask this due to i have got a set of 19" wheels and havving doughts now
Due to all the work ive put into car i want it to be able to preform on track
Should i get smaller wheels or would tracktyres be ok on wheels
Also the reason i got massive wheels was i wanted massive brakes in there

I no u all hate big rims so be nice

Zoolander

iTrader: (8)

From what I've read on this site, 17's seems to be the best balance for performance and comfort while still upgrading the look. I think 19's will be very uncomfortable while not performing as well. I hear some auto-x'ers change out their large wheels for the stockers on event days.

Hopefully, the experts will chime in and also help me out with this that is along the same line as your inquiry: I just went from the stockers to 17x8 with 235's F and 17x9 with 275's R, all balanced and aligned. The ride quality still doesn't seem as smooth as the stockers....I know I should feel more of the road since they are bigger and wider but how much more exactly? I'm also more tuned into them now too...so it could be my paranoia. These are used wheels and tires from a trusted forum member. Maybe it's the old tires? I think I feel a slight vibration at highway speeds, which makes me completely paranoid and unsafe behind the wheel.

Did you feel a big difference between the stock 16's and upgraded 17's?

limepro

iTrader: (2)

Check the weight of the rims also sometimes its a 20lb difference on each corner.

Neo

iTrader: (4)

If I remember correctly, simple physics dictate how something will behave.

Classic example is the figure skater. You want to spin faster you tuck in your arms. You want to spin slower, throw your arms out.

Same thing applies for wheels. Giant wheels (apart from weighing alot more, unless they're forged, even then...) you generally don't want. Too far from the center, requires more energy to rotate and to stop.

As a rule of thumb, you generally want wheels that clear your brakes with just enough room.

The industry nowadays want to put on the biggest wheels because that's what "looks" good.
Regardless of the fact you're running tiny little 11" brake rotors on a 3500+lb vehicle.

17" wheels on the FD is more than enough for either street or track.
There are a few people who will go to 18's because of a certain width they want to run.

But overall, 17's is lots of wheel/tire for the FD. Especially for daily duty.

Now, if you're just interested in being "baller", then put whatever wheels you want on the vehicle. It won't matter because whatever you put on it, will never be enough to stand up against the other moron who wants to put huge *** "dubs" on a sports car.

imitek

Ive never used 19" an track and just want to no will it make cornering worse
Or shell i down grade to 18" i want to fill the arches
the Tyre on my 19 are rear 265 rear and 235 front
If i do change wheels smalest id go would be 18"
Thanks for evry 1z input

jkstill

iTrader: (11)

I don't think it is quite that simple.

The wheel is usually lighter than the tire, at least up to 18 inch wheels. Having no experience with 19's, I can't say how much heavier they may be, and how much more of the weight is concentrated at the rim in comparison.

As long as the overall diameter is the same it probably doesn't make that much difference.

To maintain that diameter however would require a very narrow sidewall on a 19" wheel, which would not be a good thing for track work.

Not the fast ones.

Natey

iTrader: (19)

Not the fast ones, the BROKE ones.

The guys who change their wheels back to stock for the track are guys like me who don't have the money, time or even desire to buy bling wheels to use 1 weekend a month.

I have r-compound tires on my stock wheels, so I use them at the the track.

imitek

Do u normaly run 40 profile on 18" or would it be 35
Im gona get new rims at some point
But just for this thread
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
265/30-19 3.1in 12.6in 25.3in 79.4in 798 0.0%
225/50-16 4.4in 12.4in 24.9in 78.1in 811 -1.6%

Thats only somthing like 11mm from standerd wheel to 19
How much diffrence will that make

imitek

Also is their an optimum sidewall thickness for track

jkstill

iTrader: (11)

If you mean sidewall height:

The more sidewall, the more forgiving the tire.

The less sidewall, the faster it will break way, in general.

I'm not the expert on track tires, mostly I do autox.

The same principles apply, though the consequences of sudden break away at the adhesion limit are somewhat less at an autox event than a track event.

oyvindjs

iTrader: (4)

Its mainly about unsprung weight. In this, its the hub, brakes, rim, wheel, half of both A-arms, half of shock and spring..
You want to keep as little unsprung weight as possible on the car. Less unsprung weight = less force working against the car when the wheel is bounced up into the wheelwell when cornering, driving over uneven track surface etc...
As the car has more mass then the unsprung parts, it will have greater force and take more force to move. Its connected through the spring, witch have , lets say for now, linear spring rate, to the hub/wheel/brakes-combo mentioned above.

Think of a ship on the ocean for a sec. A large tankship cuts the engine. The force of the mass, the kinetic energy it contains, makes the ship move for miles and miles before the opposite force of the water stops the ship. A small boat will stop within a hundred metres.

The less unsprung weight you have, the less force the unsprung weight will transfer to the spring weight/ everything above mid-spring/shock. The spring/shock have an easier job keeping the lighter wheel to the ground.
And, as less force is transfered through the spring to the body of the car, the body will stay more stable too, as the spring itself has an easier job keeping the tire to the ground, and the force from the lighter mass of the wheel/hub is less than a heavier wheel/tire/hub combo.

sorry if it didnt make so much sence, it would be easier to have this conversation in norwegian... for my part that is

imitek

Nice wright up had to do resurch on unsprung weight but i understand what u are saying
So the only reason people upgrade to bigger wheels is ether for a wider wheel
or bigger brakes an ( looks)

Also this brings me to another question with what your saying that means sollid suspention ( im saying no spring at all compleatly sollid) would also make poor handeling due to all weight transfer would load the tyre on a corner Due to no absorbtion threw springs
So much to thinkabout

imitek

It would be realy intresting to see a test done same rim with a thin side wall and a thick sidewall tyre See how much diffrence it makes at the moment i have no idea all i can say is what youguys have told me and it makes sence. It would be good to see a chart with a % of traction lost at a certain g and tyre thickness for each wheel size

Natey

iTrader: (19)

Chiming in again from the broke side.
17" tires are not only lighter weight, they're also cheaper. Something to think about.

Mahjik

iTrader: (1)

The main problem is that the selection of performance tires is getting much smaller in the 17" range.

Julian

iTrader: (14)

This is where one needs to start. Pick tire selections for what you want to do, be it track, Auto-X or street then pick wheel dia.

Years ago I went to 17 in because of bigger brakes and after doing lots of research on tire availabilities and combined weights. Go with the smallest that fit but with future in mind. In hind sight I should have gone 18" due to tire market moving away from 17". Not a big deal changing wheel size, right .. except I buy 16 rims at a time - street, new dry, used dry, wet.

My new Lotus which still has not arrived comes with forged 19 front / 20 rear and only has a single fitment (OEM & aftermarket) in its size of a of a Pirelli P-Zero Corsa originally developed for Lamborghini at a Lambo price of some $800 a corner. For track and Auto-X use and my affordability I have ordered their 18 in Motorsport rims which will open up my tire availabilities.

FYI, RX-7's are cheap to buy maintain and mod. This Lotus has cost me $20 k already in just rims, and headers.

whitelight7

iTrader: (5)

IMO 19" is too big for the FD. 19" is good if you want that look, but hurts performance. Also 19" is harder to fit on a FD, and the necessary low profile tires will be more vulnerable to potholes, curbs, etc.
Consider that most of the weight/mass of a tire is in the tread and belts, and not the sidewall, so smaller wheel diameters are usually lighter. In general, a large 19" wheel adds more mass than a 17" wheel. Remember wheels are not just weight, they are unsprung rotating mass.
I agree with others that availability of performance tires is part of wheel choice.

Lightweight wheels are very important to performance, especially on a light car like the FD. Light wheels improve acceleration, braking, and handling. Spending more $ on lighter wheels is cheaper than upgrading your engine, brakes, and suspension to compensate for cheap heavy wheels!

BTW, I have 17x9 wheels, 255/40 tires, 1" drop springs, and no clearance problems at all.

juicyjosh

iTrader: (29)

Consider also that the stock FD wheels have a conservative +50 offset and fat sidewalls, which helps the car's tracking over bumps.

When I was running a significantly wider track and smaller sidewalls, I immediately noticed an increase in bump steer. It was only a small amount of bump steer, so it wasn't a big deal, but I never experienced bump steer with the stock rollers. I won't go into the physics on this one, but the concept should be somewhat intuitive.

oyvindjs

iTrader: (4)

You want big enough brakes to manage what you want to do. Heavy racing = big brakes. Big brakes = bigger rims. Big rims = more unsprung weight(usually). How to counter more weight on a bigger rim/tyre-combo? Expencive forged rims and racing tyres. Ideally, you want the rim to juuuust fit over the brakes you need for your application, be as light as possible, and utilize the tyre you need.

No suspension, think of a Gokart. On a sleek and no-bump track, a gokart, for ex. a geared 250cc race gokart, NOTHING can beat that monster on a twisty track. It has no springs at all, so all the force from a bumpy road will transfer right into the gokart and decrease the force created from the gokarts total weight + downforce(from aero) pressing the wheels to the ground, and creates less grip.
Thats why a gocart-track must be perfectly smooth. Take the same above mentioned gokart onto a regular road, and any decent performance car will have it for lunch. Why? Car has springs and shocks.



PS, if you ever get the chance, try to lift a stock Mazda Miata NA(1st gen) rim..... It weighs close to nothing. Its not the Engine that makes the miata so DAMN good to drive, its the way Mazda optimised(as much as they could for a regular driver that wants comfort too) the complete suspension package, and managed to keep the weight down on all aspects of the car, like for ex. unsprung weight

imitek

Thanks again for takin the time to post guys Its helped me loads

imitek

Also does the ofset effect handling

oyvindjs

iTrader: (4)

yes



http://www.miata.net/garage/offset.htm

imitek

thanks m8
It just clicked i always thort them top mount adjusters was pointless on mazda i thort it was to camber adjust only Now makes perfect sence its for the scrub raidus I never even thort of askin any 1

Mahjik

iTrader: (1)

I don't think you'll get much compassion on this site for being able to buy an $80k automobile.

dgeesaman

iTrader: (7)

DareISay, it could even cost the relevance of your opinion in this forum. J/K.

For the OP:
As for smaller wheels being faster - yes in broad generalization. Everything is a compromise. Bigger wheels and tires cost more. They weigh more too, but in most cases you're also going wider at the same time to gain some cornering grip.

If you don't change tire width, you're not achieving anything. Lower profiles don't tend to improve the suspension tuning. Lower profile tires will feel different to the driver, but tests by Grassroots Motorsports indicate there is little or no difference on the clock.

Many large wheels you see rolling on the street weigh a metric ton. So while they might look good, they will not be fast for racing. If you have a set of larger "street" wheels, a set of stock wheels + race tires is an affordable and significant upgrade for autocrossing. If you want to be really fast then you will buy the widest race tires you can possibly fit on the car and buy the lightest wheels that support them. You also won't drive that car on the street anymore. That's out of my budget, which is why I autocross with stock wheels and race tires.

Serious road racers usually look at the brakes they need to stop the car and fit a wheel over that with the widest rubber they can fit. So if you need 17" or 18" wheels to fit over the smallest brake kit that doesn't melt down during your session, then the loss of acceleration due to the larger wheel is necessary. Road racers also want the lightest wheelset they can get away with, so this gets pretty expensive. We're talking $4k wheelsets fitted over $5K brakesets, consuming $500 in brake pads and $1500 of race tires per track weekend.

As for the general availability of performance tires being better in 18" vs. 17" or 16", I'm not sure I buy into that. There are some performance tire models that start at 17" or 18" and exclude smaller sizes, but for each of those there is another tire model of the same type/performance that is readily available in 16" or 17" too.