Are Lighter Rims Worth The Money?

been seeing posts in forums pop up where people are asking if lightweight rims are worth it.

well, i myself have been toying with the idea of lighter rims. not only would they look better on the putra but they'll be lighter! by alot.

now, i'll try to make the calculations here explained as clearly as i can. however, if you don't understand or if i have made a mistake with my theory, then please correct me! i don't like to give wrong info so help me work towards providing the right answer if you can ok?

now back to the topic.

let's look at the wheels i've chosen for this comparison. wheel weights were taken from WheelWeights which is THE best collection of wheel weights. really.

i currently have the 15x6.5" Enkei RSF-2 which are these:

quite ugly to me as the spoke design is quite 'ugggggh' to me.
these rsf-2 weight according to wheelweights, a hefty 7.4 kg each without the tyre.

the rims i'm interested in are these white Desmond EVO Regamaster. i've no idea WTF 'regamaster' means but it's a really lightweight wheel that looks the business.

these wheels weigh only 3.88 kg each without the tyre. check out this jap guy's page regarding the wheel: Kotori's Homepage.

ok so if you do some basic math, the rsf-2s weigh in total 29.6 kg compared to the evos which are only 15.6 kg! you'd save 14 kg in unsprung mass. it seems a lot right? but how do we quantify something quite abstract like this? i propose that we look at the price-performance ratio to see if spending about RM2500 for a set of SECOND HAND condition evos are worth it or not. because sadly, the company, Desmond, does not make them anymore. neither can i find the company on the internet. so, oh well.

first, take a look at some formulas i'll be using. we have the rotational inertia of a hoop about a central axis, I=MR^2. where M is the weight of the rim (assumed as a hoop for simplicity) and R is the radius of the rim in meters(m), which is 0.1905 m (taking it as a 15" rim). then there's the kinetic energy equation for a rolling body and since a rolling object has two types of energy: a rotational kinetic energy due to it's rotation about its center of mass (COM) and a translational kinetic energy due to translation of its COM, we use:

K = 0.5*(I,com)*w^2 + 0.5*M*(V,com)^2

I is the rotational inertia as mentioned in the paragraph before, w (actually greek for omega) is the angular velocity of the wheel, M again is the mass of the wheel and V,com is the velocity of the wheel's center of mass.

now we proceed to obtain the rotational inertias of each wheel. I1 is for the RSF-2 and I2 is for the evos.

I1 = 7.4kg*(0.1905m^2) = 0.2685 kgm^2

I2 = 3.9kg*(0.1905m^2) = 0.1415 kgm^2

already, you can see that the lighter wheel has a lower rotational inertia which is obvious. but we still can't quantify it in terms of performance gains. so we must press on to the next set of calculations.

we need to find the kinetic energy of the rolling body (ie. the wheel) at a fixed speed. let's make it 100 km/h which is represented by V,com. converting from km/h to m/s we get

V,com = 27.7778 m/s

this is done to make sure we are working in the right units. next up, is to find the angular velocity of the wheel.

w = V,com/R = 27.7778/0.1905 = 145.82 rad/s

now that we have the necessary information needed, we can plug these values into the equation for obtaining the kinetic energy of a rolling body which for the RSF-2 is:

K,RSF-2 = 0.5*(0.2685kgm^2)*(145.82rad/s)^2 + 0.5*(7.4kg)*(27.7778m/s)^2 = 5709.564 J

and the Desmond Regamaster EVO:

K,RSF-2 = 0.5*(0.1415kgm^2)*(145.82rad/s)^2 + 0.5*(3.9kg)*(27.7778m/s)^2 = 3009.023 J

J stands for Joule which is the unit for energy however, we you guys wanna see it in terms of horsepower (hp) right? so, let's convert these values to hp. i'll convert Joule to Watts first, but in order to do that, we need to divide 1 Joule with 1 second (i assume 1 second for ease of calculation) in order to get it in Watts (W) which is the unit for power. now from watt to hp, we use this conversion factor

1 watt = 0.00134102209 hp

now do some basic maths again, and we can get the required horsepower to keep rotating and translating this wheel at 100 km/h (on the horizontal plane ok, cars don't defy gravity :P)

Power required, RSF-2 = 7.65 hp

Power required, Desmond Regamaster EVO = 4.04 hp

now, how to interpret these values? the difference between these two wheels would give you the amount of hp that you could 'gain' which would be

Nett power gain = 7.65hp - 4.04hp = 3.61hp

this is for only one wheel. so by right, for both driving wheels since the putra is a front-wheel driven vehicle, the total hp gained would be an optimistic 7.22hp! just from using lighter wheels.

let's not get ahead of ourselves here. i should include a 'confidence' factor to that value to bring it down to about 6 hp gained. so, spending RM2500 for this rims to gain 6 hp would give mean 0.0024 hp/ringgit malaysia(RM). let's compare with a camshaft upgrade from powerzone (assuming their cam prices for the 4G93P is RM1500 from their catalogue), based on their claim of up to 20% increase in hp, gives you 0.0154 hp/RM. hmm, so it's up to you actually whether you'd wanna spend that amount of money for the little gain in hp. but don't forget, lighter unsprung mass gives you better handling characteristics and because the overall mass of the vehicle is reduced, you get faster acceleration as well.

man, it's insane if you wanna play NA...so many things to tweak to get the same result if i'd be less stubborn and put a turbo kit.

any monetary sponsors are always welcome regardless of whether individuals or companies wishing to advertise their products (space for sponsor's company logo available and for individuals wishing to sponsor, your name will be placed around the boot/rear wing location of the putra).

This Is Malaysia.

in malaysia, you get to see buses like these run around town unnoticed by the local authorities.



i mean, for fucks sake man, think of the hazard of leaving a metal object scrapping the road producing sparks near the fuel tank. need more hints? then let the bus blow up and send bodies flying onto the street and walls then ONLY will SOMEBODY take action.

some people in certain bodies aren't doing their jobs well if not at all.

there's the number plate, so if you have contacts or power with people in high(er) places, do the general malaysian public a favour and make sure things get done.

Sheet Metal Brackets.

ah, it's holiday time so i decided to fabricate some brackets to keep my banged up apexi power intake which has actually been held by some cable ties over the past few months. so, after much procrastination, i finally went and did it.

took some stainless steel sheets i had lying around my garage and cut it to size then the end product is a very shiny, sturdy and functional piece of fabrication. :)







while i was working, my dog decided to pose. so here she is, ms. brandy.



and a little something i made for deardear with the spare stainless steel bits. shabby i know.

Guess Where This Is.

rate this pic guys. and if you can guess where this is, i'll give you bragging rights. ok?

Go Go Go-Kart Sunday!

it's 9.30am, the spirit of competition was high. when suddenly, BANG!


yup, that's me crashing into john sabah the moment the race started. one lucky cameraman was there to capture it digitally. so how did all this start?

well, Monash Engineering Club decided to hold a 'non-competitive' go-karting event. but how can you NOT be competitive when it comes to racing where fast lap times and 1st, 2nd and 3rd placing count!?!?

yup, which was why i crashed into john sabah. both of us were late-braking into the first hairpin and our brakes didn't bite thus me crashing into john, but things got worse when one of my wheels was up on his, his brakes bit. so i practically smacked john sabah's head with the nose of my kart. oh well. sorry ar john.

but we all had fun. finishing 2nd despite that crash was the most thrilling part for me as after the crash i was down in 10th placing (out of 10 drivers).

preparation. no 'X' pit-stop strategy here.


walking the course to get a feel for it. never been on this track myself so thought it might be a good idea.


shortly after that, we were called back for briefing.


now fast forward to the grand final (fastest 10 drivers compete).


and shortly after that pit-lane bickering, this happened (refer to the beginning if you forgot).


me trying to catch up.


after the race, john sabah describing how the crash affected him mentally and physically.


but at the end of the day, competition or not, we all had fun. :) great day guys! round 2 after the finals yeah.


results for those curious.

Practice and Qualifying
Finals
Grand Finals (Top 10)

Bad Practice.

i was at MPH earlier today flipping through a local car magazine which i won't mention here, and i was going like 'hey, nice car...' when suddenly i saw this:



can someone tell me what is fundamentally wrong with the rollcage of the car?


well, for starters, the front 'A' pillar bars are useless in a frontal crash because:

1. tubes were crush-bent.
2. even my cage by safety21 is BUT the difference is my bend angle isn't as much (about 20 deg. max at some points) as this guy's one which from the pic is like more than 100 degrees!
3. due to the stupidly bent tubes, in a roll, the bend region has already in a sense (crumpled) due to the inherent flaw of crush-bending method.
4. if he really wanted to avoid cutting his dashboard to fit the cage, he should have fixed a diagonal at the biggest bulge of the faux-cage to in lay mans term 'push' that portion AWAY from the driver.

well, i wish the guy best of luck and if anyone reading this blog/post knows the owner of the baby blue dc5-prelude, pls inform him to properly design his rollcage for his occupants and his own personal safety.

people nowadays.

Weight Savings 2.

mum fixed the seat good. all in all cost like RM50 if i include the 10 hrs of labour my mum put into the seat.

tada! i know it isn't the best pic but it was late and all i had was my k750i.


considering the amount spent, i'd say it's a well worth investment, having your mum to stitch these minor damages. nuff said. i mean, RM50 vs RM450, which are you gonna choose considering when you look from the outside of my car, you won't notice the difference until you go up close to it.

well, here's what it feels like to drive a car that is about 100kg lighter than factory. i notice that acceleration is quicker but the key handling characteristic i'd like to point out is that due to a decrease in weight to the passenger side of the car, cornering is not so much linear but more like exponential as in when you start slipping the tires up front they loose traction and then bite the road...the word transient comes to mind. it's funny but i can only assume at this point that it's due to the bulk of the weight up front and biased towards the driver side (the side where i put my ass at).

after putting back the refurbished seat, tools and spare wheel, i decided to whack the same corners again (i'm not telling where but it's a very nice short stretch of downhill road where you can easily hit 100 kph through the corners :D) and found that although the acceleration was not as quick as it was before, BUT weight shifts (left to right) felt more linear than before. maybe i should try without the passenger seat and whack those corners again. or lower the moment created by the backrest of the passenger seat by reclining it till it is almost parallel to the floor pan...hmmmmmm.

oh, and here's rajiv's 4th wife.

Weight Savings.

the car above has gone through a lot. however, let's just focus on the diet program its been on since i got the car nearly 3 years ago. i shall introduce you, the reader to my thesis/final year project which is currently underway where i am designing a lightweight lower control arm replacement for the proton putra.


since i started autocrossing, i've been a fanatic at keeping the weight down as much as i can. and what i've done thus far is remove most of the sound deadening material although there's still some left on the cabin-side of the firewall, most of the insulation material, carpets, plastic trimmings, roof liner, back seats, radio, speakers and antenna, stock air filter box and replaced the driver-side recaro njoy to a sscus non-fia bucket seat and finally replaced the stock muffler with a 2.1" ID pipe. believe it or not, removal of these items has reduced the weight by approximately 40kg. so, from the kerb weight of the car which is ~1050kg, it has now dropped to 1010kg.

on race day, the weight drops by another 35kg with the removal of the passenger-side recaro njoy (notice the torn parts? mum's trying to stitch them back to save me RM450 so results will be posted when she's done with it.);

and the spare wheel plus the tools required to jack the car and change it.

the items mentioned weighed in at 16kg for both the njoy and the spare wheel and about 3kg for the tools. this brings the weight of the car further down to 975kg.

now, why should we reduce the weight of a vehicle? take a look at the proton wira which had a kerb weight of 1050kg 12 years ago when it was first introduced and look at its replacement the proton persona which weighs 1170kg. bare in mind, both wira and persona compared are the baseline 1.6 models with automatic transmission and no ABS. where does this weight come from? it can't be from the slight increase in length (~10cm longer than the wira) but it could be from the added safety and luxury items due to customer demands and advancement in automotive safety.

now if we can reduce the weight, what can we benefit?

1. improved car handling characteristics (Puhn, 1976)
2. fuel savings (Borns & Whitacre, 2007)
3. decrease environmental impacts from reduced CO2 emissions
4. increase in engine performance

just to brush the surface of my points, Fred Puhn states in his book that reducing the sprung and unsprung mass of a car would result in better handling. handling consists of not only cornering or maneuverability of the car but also breaking performance of the car.

fuel savings as mentioned by these two Alcoa Industries reps, have been proven by companies like BMW who have reduced the weight of a test car by 10% and thus experience better fuel consumption by providing 2.5 extra miles per gallon. due to this reduction in fuel usage, impact on the environment from vehicles can be reduced from the reduction in CO2 or NOx gases due to internal combustion engines. since fossil fuel is not a renewable source of power, this reduced fuel consumption would enable our fossil fuel reserves to last just a little bit longer.

on a more personal note, i have experienced quicker engine response due to this reduction in weight due to the fact that the lighter the car (ie. less mass) the less load there is on the engine to propel the car to a predetermined speed like the 0-100 kph time for example.

tune in next time when i discuss the topics of interest regarding my thesis.


ps. all SSG batch mates, there'll be a Alumni dinner in SSG hall

this hall, on the 29th of September, 2007 and all the teachers and current principal would appreciate if we, the pioneer batch of SSG would attend this dinner. have to buy tickets though at RM50 i think. to purchase these tickets, just head to SSG's Principals office and look for his secretary.

Catch Dry?

was at bangsar village doing my weekly grocery and while waiting in line at the checkout counter, i noticed amongst the cigarette racks there was a mini fridge/cooler that had a sign which said,

Dear Smokers,
No chewing, no smoking, enjoy.

or something like that, but yeah, it caught my attention because it was an alternative to tobacco. before i begin, NO, i have not started smoking again...that phase has been long behind me now. just wanted to give this product a shot, because it wasn't your regular nicotine patch or gum that smokers use to get their fix.

so i picked up the 'Cassis Menthol' pack and paid my RM6.90.

this is what you get,



inside, there's about 16-20 little packets with material if not similar to your little tea bags to allow your saliva to wet the 'baccy and you get the 'baccy juice. not too sure how the the older generation used to chew baccy and beetle nuts to get high (were they?). anyway,


so what you do is you take a little packet and stuff it behind your upper/lower lip and 'ENJOY' as the container says...but i was far from enjoyment/ecstasy or what-not.

firstly, you look like you've got serious buck-teeth problem or someone punched your lip to make it look swollen.

secondly, it smells good (like various fruity shesha scents) but tastes BITTER and SALTY!!! wtf man.

so to my parents amusement at the weird facial expressions that i made while the thing was in my mouth i left the thing behind my upper lip while sufferingly swallowing the baccy juice bit by bit.

i tell you, this product would make you rather have a damn ciggy because of the stupid way you look and also because of the taste. to me, it just puts me off.

high? well, i did feel light headed for like 10 minutes but after that, nada.

so was it worth RM6.90? to me, hell NO!

say, TAK NAK to CATCH DRY! :P

however, if you wanna know more, go to GothiaTek the creators of this smokeless tobacco product.