wheels

[tom t]

just been up the road against my m8s 106 gti.
got my new turbo on there, running just uner 1 bar. and ive put my 16" wheels on the front.

baiscally i raced him before with a standard turbo which smoked, and i had 13" wheels on and was running 0.5bar. and i done him then.

but this time with the turbo and the bigger wheels on he done me really. do bigger wheels really make that much difference?

:disagree:

[RAGOONEY]

what turbo and boost you running?

[scratcher]

smaller wheels will get you moving quicker.
because of the smaller radius it acts as kind of a lower gear than if it was a larger wheel, if that makes sense?

[Schakal]

smaller wheels will get you moving quicker.
because of the smaller radius it acts as kind of a lower gear than if it was a larger wheel, if that makes sense?


what he said ^^^
also smaller wheels are likely to weigh less :smokin:

[tom t]

same turbo as k-tec 230.
and just under a bar of boost. i really need 2 get another couple of standard wheels then for the back. but i think they look pants compared to my other wheels... dow:disagree:

[tom t]

and that does make sense about the lower gear thing people ta.

there was a chart on the old site that showed the difference in speed bigger wheels mad on the old site i think? has any1 got this knocking about? cheers

[Matt@CodeRedMotorsports]

what he said ^^^
also smaller wheels are likely to weigh less :smokin:

Less rolling resistance too..........

[wrightygtt]

no idea mate, but I've said in the past 106 gti's are quicker than standard fives/ fact, they are alot quicker than people give credit for. Try the smaller wheels, perhaps you just couldn't drive on the day:cooter::burnrubber:

[5alldaway]

or maybe he just got the jump on you

ive been up against a very tuned 106 gti in a raider with about 10 mins worth of mods on it and it smoked it every time

[gttjames]

no idea mate, but I've said in the past 106 gti's are quicker than standard fives/ fact, they are alot quicker than people give credit for. Try the smaller wheels, perhaps you just couldn't drive on the day:cooter::burnrubber:
nope.

3 of my mates have gti's, when i first got my 5 it was standard, standard boost, wheels, suspension the lot. Only thing different on it was a airfilter sitting right next to the turbo (couldnt have been doing any good for cold air).

Raced all 3 of them and beat them, granted not much in it as standard, but r5 deffinatley quicker.

now with a bit better setup, air filter to front, strapped intercooler, scorpion exhuast and bigger downpipe and 12psi boost from the standard t2 and its easy work shredding gti's

ino its nothing to go by but parkers guide 0-60 time for a 5 is 7.1 i think and gti 7.8 is it?

[wrightygtt]

maybe, but i'm sure they tested the gti with 3 passengers and a tank full of fuel, to keep the insurance down. :)

[Scoff]

looking at book 1/4m numbers for both cars they each trap at about 86mph, so they're about as quick as each other. the list I looked at showed 2 versions of GTI though, a 135hp edition too, which was a gnats cock faster at 88mph ;)

[tom t]

yeah they are quite quick def. but i wasnt happy as i done him last time. and considering ive got a new turbo and more boost annoyed the hell outa me. ill be looking at putting the old wheels on and trying it then.:confused:

and he definatley got the jump on me the first time we went 4 a spin, then the next rund i got the jump on him then he caught me up lol

[ollyhock]

no idea mate, but I've said in the past 106 gti's are quicker than standard fives/ fact, they are alot quicker than people give credit for. Try the smaller wheels, perhaps you just couldn't drive on the day:cooter::burnrubber:


The 106gti is only the same engine as the Saxo vts, infact the pug is slower to 60 on paper as it weighs more, I've had a vts from new and it wasn't as fast as my gtt

I've got a 56 plate mitsy colt cz turbo , and my gtt is quicker than that aswell

[tom t]

could have been the driving lol. but i bet when i get the smaller wheels back on ill lick him :laugh:

maybe il have to get them polished or something to look a bit better.

[ollyhock]

could have been the driving lol. but i bet when i get the smaller wheels back on ill lick him :laugh:

maybe il have to get them polished or something to look a bit better.


I've just put 15" turbines on my gtt and it ain't made any noticsble difference

I think I'd smoke a standard 106 gti. IMO

[wrightygtt]

Just keeping it real. I honestly don't care whats faster, tbh, just stating the fact that there nippy for what they are! and quicker than the book time suggests. Also if your not running a standard setup i.e standard boost(mine was 8psi when I bought it), its not really a fair comparison.

[markey b]

my mates 106 gti i ran down the pod for him,

was std, apart from powerflow catback exhaust, cheap ebay induction kit, and it had 15" cyclones rather than the 14" std wheels. ran a 15 dead

[BriC]

I've just put 15" turbines on my gtt and it ain't made any noticsble difference

I think I'd smoke a standard 106 gti. IMO

I seem to remember that my 15" TSW's had the pretty much the same rolling circumference as my speedlines - obviously due to the lower profile tyres. (Can't remember the tyre sizes though)

[ollyhock]

I seem to remember that my 15" TSW's had the pretty much the same rolling circumference as my speedlines - obviously due to the lower profile tyres. (Can't remember the tyre sizes though)

yeah if i remember , i didnt jack the car up any more to get the speedlines off and the turbines on.

its only a small difference if any in the dia

[haizyr5gtt]

yes bigger wheels always make a hell of a difference. the ex had the same problem with her mx5 when she put 17s on it. she couldnt even beat a vts after that. im stickin with 13s on my raider.

[jantheeven]

yes bigger wheels always make a hell of a difference. the ex had the same problem with her mx5 when she put 17s on it. she couldnt even beat a vts after that. im stickin with 13s on my raider.

All depends on what tires you use mate... just use thinner tires when your wheels get bigger, it's as simple as that. On my original speedlines I had 165/60R13 tires and now I have 195/45R15, which results in approx the same circumference

[tom t]

there 195/45R16. but surely there must be something else up if the 5 running just under a bar didnt do him? but it did on 0.5 bar wit smaller wheels?

prob just me being annoyed tat i didnt beat him lol. plus i dont wana have to put the standards on lol

[jantheeven]

there 195/45R16.

well there you go then... if I were you, I'd use 195/40R16 tyres when your current ones are gone :agree:

[tom t]

is there much difference in complete size from that size wheel and tire then to standard wheel and tires? cheers m8

[Trevhib]

Weight also has a say in this equation (though to a lesser extent), not just diameter.

[jantheeven]

is there much difference in complete size from that size wheel and tire then to standard wheel and tires? cheers m8

Simple calculation... Let's start with the original 165/60R13 wheels & tyres.
The wheel's radius for a 13" wheel (without tyre) is 165.1mm.
But you also have a tyre, and the height of the tyre is 60% of the width (165mm), which equals to 99mm. So the total radius for wheel and tyre together is 264.1mm.
This gives us the circumference: 2*pi*radius = 2*pi*264.1 = 1.66m.

The same calculation for the 195/40R16 results in a circumference of 1.77m.

For your 195/45R16 it's 1.83m... and my 195/45R15 it's 1.75m.

So you can see that - compared to original wheels and tyres - the 195/45R15 tyres "only" have a difference in circumference of 9cm (5.4%) and your 195/45R16 a difference of 17cm (10.2%). Draw your conclusions from this... ;) :agree: :coffee:

I'm spent now... :laugh:

[D4WNO]

Jan....blimey!! :laugh:

Lol fair play for working that out :D

[jantheeven]

Jan....blimey!! :laugh:

Lol fair play for working that out :D

Thanks... :laugh:

Yeah... well... I have a Master's degree in mechanical engineering, so it would be pretty embarrassing if I couldn't manage this :wasntme:

[Trevhib]

Simple calculation... Let's start with the original 165/60R13 wheels & tyres.
The wheel's radius for a 13" wheel (without tyre) is 165.1mm.
But you also have a tyre, and the height of the tyre is 60% of the width (165mm), which equals to 99mm. So the total radius for wheel and tyre together is 264.1mm.
This gives us the circumference: 2*pi*radius = 2*pi*264.1 = 1.66m.

The same calculation for the 195/40R16 results in a circumference of 1.77m.

For your 195/45R16 it's 1.83m... and my 195/45R15 it's 1.75m.

So you can see that - compared to original wheels and tyres - the 195/45R15 tyres "only" have a difference in circumference of 9cm (5.4%) and your 195/45R16 a difference of 17cm (10.2%). Draw your conclusions from this... ;) :agree: :coffee:

I'm spent now... :laugh:

Quite. And what does a 5% and 10% increase in rolling circumference have on acceleration?

[D4WNO]

Sadly enough, I could follow almost all of it :eek:

Well Jan, you can never be told you're not thorough :wasntme:

[jantheeven]

Quite. And what does a 5% and 10% increase in rolling circumference have on acceleration?

lemme work on that one for a minute...

and might I add... 195/40R15 gives an even smaller difference... the rolling circumference is then 1.69m, a mere 3cm or 1.8% deviation...

[Trevhib]

lemme work on that one for a minute...

and might I add... 195/40R15 gives an even smaller difference... the rolling circumference is then 1.69m, a mere 3cm or 1.8% deviation...

Ace.

195/40/15. Yeah but are those tyres available? And for a reasonable cost? In the UK?

[jantheeven]

Ace.

195/40/15. Yeah but are those tyres available? And for a reasonable cost? In the UK?

Yeah I know... those are expensive... if available at all! That's why most people choose 195/45R15

[tom t]

cheers 4 that m8 really helpfull. and damn 10% like you say that would definatley increase accleration especially compared to when i had the small wheels on it.

there definatley going back on lol.


and it seems a long while since school so i kinda leave maths out of the equation now lol lazy i know. cheers people :agree:

[Andrew Cooke]

So you can see that - compared to original wheels and tyres - the 195/45R15 tyres "only" have a difference in circumference of 9cm (5.4%) and your 195/45R16 a difference of 17cm (10.2%). Draw your conclusions from this... ;) :agree: :coffee:


what conclusion should I draw? That a bigger wheel means that at 65mph I'm in 2nd rather than 3rd, and am thus going to accelerate faster with bigger wheels? The more you look at gearing the more you realise that the correct answer to any gearing question is 'it depends'...

btw, isn't the standard tyre a 195/55/13, so dia is 1.71m - not that you can trust the size on the tyre to agree with reality :laugh:

[jantheeven]

what conclusion should I draw? That a bigger wheel means that at 65mph I'm in 2nd rather than 3rd, and am thus going to accelerate faster with bigger wheels? The more you look at gearing the more you realise that the correct answer to any gearing question is 'it depends'...

No... the smaller your wheels, the faster you accelerate. Up to a certain point, where the bigger wheels give you a higher top speed... (leaving gear ratios and gear changing out of the equation of course)

[Andrew Cooke]

No... the smaller your wheels, the faster you accelerate. Up to a certain point, where the bigger wheels give you a higher top speed... (leaving gear ratios and gear changing out of the equation of course)

your belief is too simplistic. Either take my word for that, or start with a torque curve and work it out for yourself.:)

[jantheeven]

your belief is too simplistic. Either take my word for that, or start with a torque curve and work it out for yourself.:)

I am simple... :laugh:

No I know what you mean... but sometimes you have to make certain assumptions and simplifications to calculate something. I know what a torque curve looks like and that's far from linear or simple. But it is true that (up to a certain point) your acceleration is greater with small wheels than with big wheels... and that top speed is higher when you have bigger wheels. ASSUMING no losses anywhere, linear acceleration and constant power. Which isn't the case :wasntme:, I know... So the difference in acceleration is certainly not the same as the 5% or 10% in circumference difference I was talking about due to a number of other factors, but it gives you a rough estimation. ;)

[ollyhock]

motor world near me are doing proxes for £40

[Andrew Cooke]

I am simple... :laugh:

No I know what you mean... but sometimes you have to make certain assumptions and simplifications to calculate something. I know what a torque curve looks like and that's far from linear or simple. But it is true that (up to a certain point) your acceleration is greater with small wheels than with big wheels... and that top speed is higher when you have bigger wheels. ASSUMING no losses anywhere, linear acceleration and constant power. Which isn't the case :wasntme:, I know... So the difference in acceleration is certainly not the same as the 5% or 10% in circumference difference I was talking about due to a number of other factors, but it gives you a rough estimation. ;)

just for you I've made a few curves using Mudslinger's torque curve. I've not scaled the axes, so the units are rubbish, but vertical is torque at the wheels and horizontal is speed. More torque at the wheels gives more acceleration, obviously you can only use a certain amount of torque before the wheels spin. Lets guess that figure is 400, anything above that is wheelspin. The curve shows the 1st 4 gears, and compares 2 sets of tyres, the pink curves are 10% smaller than the blue. As you can see, there are speeds where smaller wheels are better, and speeds where bigger wheels are better. Over all there isn't much in it.

[jantheeven]

cool... nice info! :agree:

[Trevhib]

Looking at the chart I'd say overall there is enough in it for it to be noticable and possibly worthwhile choosing the smaller wheels. That's MO. Great graph again and with a correct legend this time... :innocent:

[jantheeven]

Okay... I could have saved myself the trouble of calculating all this myself and use this nice tool instead :wasntme:

http://www.miata.net/garage/tirecalc.html

At least this calculator agrees with my calculations... :D

[ranj]

maybe its the tuning that caused the loss and not just the wheels ...... before u had 0.5bar and a smaller turbo ..... now you are running 1 bar with a bigger turbo .... has the fuelling been checked ???? Have you altered the carb jets ??

If not then maybe the there is loss of power due to the car running very weak ..... Only a suggestion :)

[tom t]

was thining this. need to get it checked. ive turned the boost down a bit now. just incase. it seems to me like there is plenty of fuel as the exhaust is all sootted up. i know thats prob not very accurate lol. really need to invest in a afr gauge just skint at the mo.