Cornishblue

Hi,
can anyone tell me if 19inch wheels fitted on a 2004 WRX would effect performance.

Went to local HIFI/wheel centre and one of the salsmen said that 19inch wheels could slow the car down. He felt 18 inch ones would be better.

Is this true?

Im thinking of 19inch Silver OZ superleggers on WRblue.

Cheers

l6ves

Im not sure if they fit a 2004 but i have 19's on my 93 WRX, and to be honest with you the only difference i noticed is that they look a lot better!
the difference in speed is probably so minimal you wouldnt notice!
Lucie.

TonyBurns

iTrader: (3)

Your quite right to be worried about performance, you will loose some with every wheel size you go up, just due to inconsistancies in the likes of tyres, you could loose upto 10% on 19's over the likes of 17's, your ride may be a little rougher due to the size of the tyre wall (ie it being smaller so less flex, so that = harder ride). 18's are probably the best compromise on a new age car with both looks and drivability (plus you may find that the tyres are a bit more expensive for a good manufacturer on 19's).

Tony

sammyh

iTrader: (1)

I disagree

I really did not notice any difference in performance when I put the 19's on my car.

What i did notice is that when I reverted to my 18's the handling was not as sharp and felt soggy if that makes any sense. I was all set to put the 19's on my type 25 but the new cars have a different stud pattern

Elmer Fudpucker

I've changed from 19'' Super leggs to 18'' Speedlines on my 03STi

but,mainly for ride comfort reasons as I spend a lot of time in Antwerp where even a mountain goat on a motocross bike would struggle on some of those roads,let alone a lowered perforformance car with elastic bands for tyres

can't say as though I noticed any performance losses/gains or any different handling traits between the 2 at all really


...except that everyman and his dog has SL's and I hate them with quite an unhealthy passion

Jon

7 Foot

When I fitted 18"s on my MY00 i noticed quite an obvious loss of acceleration.

Scoty

Would have thought it would have made the car a bit quicker, your covering more ground with the bigger wheel/tyre on every turn of the wheel.

WR1 Wannabe

It will make the top speed higher, but will reduce acceleration as you are applying the same amount of torque to a larger radius (= less force/acceleration). Also, depending on the difference in tyre profile, your speedometer may read incorrectly (not sure where it's hooked up to on a scoob...?).

Edited to rearrange the torque bit to make it more understandable.

Scoty

But torque at the outer driveshafts will be the same will it not regardless of what size of wheel is on?
Put a 17 inch wheel and a 19 inch wheel together and give them a one time push over a certain distance, the 19 will get there quicker, but you are using the same force to push them both wheels.

7 Foot

What about the weight issue? My Diablos weigh a shed load more than th OE 16" ers they replaced.

elgordano

the radius surely stays the same because you are using thinner tyres on a 19 than a 17.

Jay m A

iTrader: (2)

Its not size that matters most, as said earlier the rolling circumference should be similar due to the lower profile tyres.

Weight is the key. The supsension is set up with a lot of things in mind - one is the unsprung weight of the car. Ride will be affected one way or the other if weight of the wheels is changed.

Take as an example a light 16" wheel and a heavier 16" wheel. Usually if weight is added to the wheels there will be a double performance loss. Firstly acceleration will be less since there is more mass to turn. Also responsiveness in steering will be less due to more inertia in the wheel, finally the suspension (if correctly setup for the lighter wheels) will be underdamped, resulting in poorer ride.


Some 18" wheels are lighter than OE 16/17" wheels, but just as strong - price is the key usually.

911

Jay is right.
the larger the wheel (the aluminium bit) the higher the inertia of that wheel compared to smaller ones.
The engine on a 19'' car has to accellerate the heavy wheels, the smaller the wheel the less mass it has to acellerate.
This is very true of '0 to 60' tests.
F1 cars run small wheels/large sidewall tyres for a number of good reasons, but the rotating mass is minimised, critical for accelleration and turn-in.They are good at both!

The low profile tyres that come with 18/19's afford a decrease in 'delay' for the car to respond in a bend to the steering input as there is less lateral movement in response to weight shift as the car turns in. the car feels more stable.
Enter the real world now; the 18 inch car will cover ground on a good A or very good B road really well, and the inertia issue diminishes. Just that you need to choose a road without pot holes........now that can slow you down........
911

Hoppy

Bearing in mind that any change in wheel size demands an opposite change in tyre size in order to maintain the same circumference, I cannot see any significant change in accelleration, intertia, gyroscopic effects or whatever. Overall, all you're doing is making the wheel a little bit bigger and the tyre a bit smaller.

The only thing that would change this would be a substantial increase/decrease in weight and while I think it's generally true that bigger wheels and tyres are heavier than smaller wheels and tyres of the same diameter, there's very little in it and sometimes the reverse applies (magnesium alloy etc).

I would like to see proof in changes to 0-60 times - surely the difference would not be measurable?

The most significant changes you will find will be a) cost, b) cosmetic, c) harsh ride, and d) beware pot-holes. Maybe rubbing arches, too. Less significant will be faster turn-in.

Richard.

PS As an aside, there's a Ferrari F1 front wheel in the office at the moment (magazine competition prize). It is absolutely huge with a tiny wheel and very high profile tyre - 265/55x13. But the most amazing thing is the weight - I'm guessing, but I'd say under 10Kg (half most road cars?). Tell me, why does F1 run such high-profile tyres? It doesn't make sense, unless it's some regulation size or something. Surely any track car will go better on a big wheel and low-profile tyres - and then there's more room for bigger brakes which Williams and Toyota might appreciate

Jay m A

iTrader: (2)

Hoppy, its exactly that - regulations re: F1

Weight is an issue and the effects are noticable, for example on my Westfield the original wheels were 15" Fox racing with Yoko A539's - weight per corner 18.5 kg

Now running 13" minilites with Yoko A048's - weight now 12kg, if I'd have gone for an even lighter tyre (avons) I'd have got it down to under 10kg a corner.

A saving of 25+kg on a 600 kg car is good

But its 25+ kg of unsprung rotating mass, and once rotating that 25kg saved is amplified more (braking, acceleration, turn - in)

7 Foot

I know this is a wobbly statement as you can't really quantify these things but -

I would honestly say that the difference I noticed in accelleration, once I had fitted my 18" Diablos, was just as noticeable as the change in handling/ride.

The difference in weight I felt pulling the OE 16"s off the car and putting the 18"s on was huge.

I kept the OE wheels in my shed for months, to use on trackdays, but never actually put them back on my car as I simply didn't want to face up to the difference in performance.

Sold them to SiPie in the end.

Hoppy

Jay,agreed. You are saving 30% weight which is a lot, and the unsprung weight saving on such a light car will make a big difference to handling. But it's not a 1,400kg Scoob!

It is weight, not size, that is making the difference, but I can't believe that a couple of kilos is going to make a measurable difference to accelleration especially when you've got the discs to spin as well, and all compared to the massive relative weight of the car.

Just for interest, I weighed a some wheels/tyres. 17in Radius R3 with new Uniroyal Rainsport is 18.5kg on the bathroom scales. 17in Radius R3 with absolutely track-shagged B'stone SO2 (thanks, Floyd ) is 18kg. For comparison, the SIDC site says an OEM 16in wheel/tyre is 16kg so not a big difference, really.

7 Foot, what do your 18s weigh?

Richard.

Hoppy

Just out of curiosity, what do you think that F1 front wheel actually weighs (see above)? Bear in mind it's absolutely massive at 265/55x13 which works out at approx 26in high by 13in wide - much bigger than a 17in Scoob wheel and tyre that weighs 18kg.

Total weight is bang on 10kg.

Richard.

SlowBoy

iTrader: (1)

It would make a measurable difference. That's why the hardcore sprinters go to the trouble of removing carpet, fitting lightweight 'glass', etc.

If you're saying a couple of kilos each corner wouldn't be noticed by most drivers, on road, then I'd agree.

RareRims.co.uk

Its not the static weight that makes the difference!

Rotational weight effects are far great.

Example - lightweight flywheel on a car, not a lot of difference in KG terms, but as its rotational, makes a big difference.

Rule of thumb - 1kg of wheel weight = 10kg in car weight

vindaloo

Cars do sometimes feel slower with larger diameter wheels. Usually the tyre and wheel width goes up too, which implies an increase in weight.

Think of the wheels as four flywheels attached to your driveshafts. The engine's got to expend energy accelerating them.

Even if the wheel/tyre is the same weight, however, it's how the weight is distributed. A bigger wheel/tyre combination has more mass concentrated near the outside of the wheel, rather than the inside. You can still lose straight line performance.

Both the static weight and the distribution (dynamic weight?) also make a difference to how the suspension and steering work/feel.

J.

7 Foot

Since this thread has been running I have replaced the heavyweight 18" Diablos I have been running on for a set of 18" Superleggeras. I have not been able to test the car fully, as I am bedding in new discs and pads all round, but it is certainly pulling harder with the lighter wheels fitted.

Will give it a true test in a couple of hundred miles.