CabbyRS

As above?

JamesH

iTrader: (21)

Slower accelerated but more top speed IIRC

But then not sure how much difference it makes once you start thinking about profile tyres cos it may end up the same (overall diameter)

ON-UJAH

Depends what you mean by slower?

Acceleration may be slower, but cornering may be faster due to lower profile tyres with stiffer sidewalls.

Weight plays a factor - something like a Volk Racing CE28N can weigh ca. 5.5kg in 15" much less than a standard cast alloy wheel in 14".

s1rststeve

i am sure it does, where i live there are loads of corsas and 106s with big wheels which sound like they are going fast but are slow as fook!!!

CabbyRS

BM08

Exactly, where as i make half that noise and sail past all the cora and saxo boys

Mr Sam

i had pepperpots on mine for ages went back to 12" pranwheel steels for the MOT and left them on

2kg lighter a wheel inch less diameter loads better accel

Fast Guy

Not neccesarily. I went upto 16"s and they weigh 5.1kg each. Lighter than the 15s I had on before at 5.9kg each. I also put 215/35/16s on at the same time and went 0.3s quicker over the 1/4 mile (but I had lost about 50kg or so at the same time)

tabetha

Depends on the OVERALL weight of the wheel tyre combo, where the weight is!!, and overall diametre, a combination of all three.
If the wheel is heavier it could still be better as it may be that the lower profile tyre is lighter thereby moving mass towards the centre of the hub if you see what I mean, ie if the heavier weight is nearer the centre it will accelerate better than one of the same weight that is heavier on the outside of the wheel, as wheel acts as a lever.
Lighter wheels really do make a hell of a difference but not as much as some say, a man on thursday evening at snetterton told me how his road going porsche does 228mph on 450bhp "because he has lighter wheels".
tabetha

starturbo

in a nutshell,if you increase the overall diameter it will slow your accelaration and give you a higher top speed.its all do do with gear ratio.it also puts your speedo out.

rssteve

also it will only increase top end if you have a shit load of power, i.e. enough to get to the limiter in top gear. otherwise it will just make the sameish top speed but at a lower rpm as the engine will run out of power to push it faster.

morto

here,s a pic of the wieght of my volks TE37 there 520kg sorry for the quality but you can just make the weight out





im just in the process of swapping them for some new 17in but there realy light

andy

Fast Guy

520KG

My 7x16 Volks are 5.1kg

ON-UJAH

15x6.5 ET45 TE37s in 114.3x4 weigh...

4.21kg



If anyone needs to know info on Volk Racing wheels - just ask!

DROPTOP

think its more likely to be the 1L engines that make them slow as fook not the wheels lol

Stu @ M Developments

iTrader: (12)

Everyone seems to have missed teh fact that if you fit bigger wheels you then change teh tyre size so that teh overall rollimg circumference is exactly teh same.

So, if teh wheels you fit were the same weight, then no you wouldnt affect teh speed of your car at all.

foreigneRS

depends where the weight is carried stu as it could increase the inertia and slow acceleration (like a heavier flywheel) - in theory

i can't see it making much difference on a vehicle weighing over a ton though

Fast Guy

I fitted bigger wheels and then changed the tyre to the smallest diammeter I could get to increase acceleration. (over 1" smaller diammeter and I can live with the lost 2 or so mph)

rssteve

but there not always the same overall size, well all of mine have never been the exact same.

Stu @ M Developments

iTrader: (12)

If you use a decent wheel and tyre supplier there is rarely a need to ever be over 1% out on your rolling radius.

Stu @ M Developments

iTrader: (12)

You CHOSE to do that by fitting the wrong tyres though... it wasnt a fault of fitting bigger wheels was it? Your speedo was also overeading. Most people DONT want that, which is why you keep teh gearing teh same...

GARETH T

it can make a masive difference,, my friend went from 15" comp mo's to 13" alloy spun radical wheels (same rolling radius), and his car was over 1second faster around pembray (where he was already fastest in class)

he thinks its the best move he has ever done to his race car

Fast Guy

No, I chose the right tyres for the job I wanted them to do

Stu @ M Developments

iTrader: (12)

On same rolling radius tyres?
I am amazed at that if its a heavy car and therfore stand corrected.

Stu @ M Developments

iTrader: (12)

Yes, but thats not what this topic is about is it, the topic is about changing wheel sizes not tyres...

You personally would have got a very similar effect by changing teh differential ratio and teh topics not about that either.

St3V3_C

Perhaps CabbyRS can give us some before and after sizes of both wheel and tyre.

But, in a nutshell, the answer is probably no, not as much as you'd really notice.

foreigneRS

i certainly feel that my 'ring taxi' cossie on original 15" wheels is better than my other one used to be on 17"

what do you think about the flywheel then gareth? can that have a noticeable difference? there's even aluminium FEAD pulleys available that have claims of increased acceleration

buzznwood

The radius of the wheel has more impact than the weight. Generally when people go up a size (as pointed out by stu) the tyre comes down so you normally end up with the same radius.

It's all to do with angular momentum and the moment of inertia which is wheel mass * radius^2 as the radius is a squared it has more effect. In simple terms the bigger the radius the more torque is required to get the wheel spinning so a smaller radius wheel would take less.

GARETH T

as far as i know stu they was very close,,,,
he got different diff ratios, so its not like he cant gear it the same also

im not really too sure about flywheels as to how the engine would accurate under load,,, ofcause off load it makes a massive difference

foreigneRS

of course off load. maybe some noticeable effect in lower gears, but not in higher ones

but with wheels, the gearing also affects the inertia that the engine sees, so could be quite noticeable thinking about it.

also, a heavier wheel is not good for the suspension as the unsprung weight increases and tends towards the sprung weight.

not to mention the gyroscopic effect of larger wheels making them more reluctant to change direction.

all of that is why you should only use wheels that are big enough to cover the brakes that you need and no bigger - whereas most people these days fit big wheels cos they 'look better' and then buy big brakes to fill the wheels increasing the unsprung weight further

GARETH T

on the flip side there is a reason why tourcars run big wheels,,, and its not the brakes

they can control tyre temps alot better,,,, and wear rates because of larger area