Slower 1/4 mile times with Larger Rims ????

XR6-VCT-2000 · 09-02-2006, 12:56 AM

Ok , what im about to ask , consider it like the following so everyone knows what im on about .......

Basic question im asking is..... if anyone has thinks rim size really effects your 1/4 mile time ??? without changing diff ratios ???? .... reason im askin ....... -->>>>

breaking things down to a size everyone can follow for eg....

Say consider the engine output ratio/per rpm at the diff as like a cogg/sprocket - say the size of a 10 cent piece , then your rim size is like a cogg/sprocket too say the size of a 20 cent piece ( with say 16" rims ) ..... now - ratio has it that only 1 turn of the smaller cogg/sprocket will only turn the 20 cent size rim/cogg/sprocket half a turn roughlly ( give or take a bit etc etc , u get the idea ) ... now if u had say a rim 19" / size of a 50 cent piece , then the smaller 10 cent piece size sprocket/cogg would only turn the 50 cent size cogg/sprocket/rim about a quater turn ...... now if u can see what im getting at - i know u can have the effect of like say-- a quicker take off but less travel distance - versus - more travel distance but slower takeoff ...... anyone noticed any dramatic 1/4 mile time changes after changing their rim size say 2 to 3 inches larger ( eg.. 16" to 18" or 19" ) without modifying the diff ratio , faster or slower times , i would be very interested ...thanks ..

XR6-VCT-2000 · 09-02-2006, 01:05 AM

Just the thing that makes me wonder is I know u could pull a 1/4 mile faster if u can travel more distance quicker ( bigger rims turns less per rmp/ and less tourque, so takes longer to pick up the rpm's - but has more travel distance because of its size ) . But can this be justified over having an engine that can turn the smaller rims more easilly with more tourque thus changing gears faster etc etc etc and achieving more speed and distance faster ?????????

JC · 09-02-2006, 01:37 AM

The rolling diameter of the rim/tyre combo should be the same whether running a 16" rim or a 19" rims. ie you run a 225/5016 or a 235/35/19. Rolling diameter is within a few %, so no major change. From my understanding, it's the weight of the rim that ***can*** make a difference - ie more power required to get the rim turning, so slower takeoff. Personally, I doubt that a 1 or 2 kg difference on a car weighing 1700kg would really be noticeable.

Tyre width may be a factor though. Too wide = too much traction = bog down at start.

XR6-VCT-2000 · 09-02-2006, 01:42 AM

ok , maybe i have confused some people , alot of thread reads , but no posts ..lol .I'll explain propperly why im asking then it might make sence .....

Years ago when i had my old XE i went from the origin stock size rims to 16" rims ( that was huge back then and very hard to get hold of ! - so were they tyres to fit back then ! ) ....anyways ... I put 16" rims on it but left the diff ratio as is ... after doing 1/4 mile time try-outs i found the car was a tadd slower with the 16" rims i put on. note , were same 'width' tyres and same 'width' rims with the 16" as the originals ( well i had 14" x 8's on it be4 and 16" x 8's after ) . In takeoff the car used to smoke them a bit if planted to the floor and reved out really quick through the gears ( could feel the pull ) , with the 16" rims it took off more boggish , took longer to revout , but was also at a faster kmph speed when gear changing than with 14's - i think i prefered the pull of the 14's more backthen and i did pull slightlly faster times ... but asyin all this , i know the ratio of each gear in ya gearbox/auto and the diff ratio in ya car can have heaps of effect on the output .... some might get faster times in some cars depending on their other ratios in the diff / gear of each gear in gearbox , some might get slower times with a larger rims , might be un-noticable ....... but im just wondering mainly with a I6 AU2XR6 VCT stock - if going larger rims will give me this 'boggish' experience i had in my XE ????? - or is the ratios of my car/diff/auto suited better for larger rims ( give me a tad faster time , slower time , same time on a 1/4 mile ) ?????????????????

XR6-VCT-2000 · 09-02-2006, 01:48 AM

JC - well the original rims were plain old heavy steel , the newer rims i had were 'original americal centerlines' - halo star pattern , billet alloy ( i could pick each rim up with a tyre on it and it felt no heavier than ust the tyre ) - allthough i got tadd slower times , i also had a lower profile tyre of the 16" rims so the outside diameter was as close as what i could get be4 but lookin a tadd bigger ( outside diameter top to bottom on the tyres on the 16" rim was about 1" larger all up ONLY tahn the total outside diameter on the 14's) - yet it seemed to make a HUGE difference !! - from only 1" larger ( like half inch extra bigger at the bottom , and half inch higher to the guard up top ) .

XR6-VCT-2000 · 09-02-2006, 01:55 AM

I thought that too that with a same width tyre and rim as be4 but only a tadd bigger ( and these new rims were like 1/10th the weight of the original steel rims too ! ) wouldn't of made buggerall difference , if anything i expected a tadd faster maybe ... but it seemed the ratio of my diff and tranny back then better suited the smaller rim , it didnt seem to work then engine as hard having to turn a smaller rim/wheel , thus letting the engine work more freely / faster getting to redline and bla bla bla , although it was nearlly 1 second faster all up with the original smaller steel rims with the ratios setup i had ..Im just curious about the times with a AU2 XR6 VCT standard how larger rims will effect the takeoff etc etc , or effect performance at all .

stiddy · 09-02-2006, 02:03 AM

YES, the is a HUGE difference, speaking from personal experience too..

Agreed the overall diametre is the same.. but the lower profile you go the harder the car is to get off the line.. with 16's you get so much more sidewall flex.. which means traction basically..
rim weight does make a difference too.. but lower profile, less sidewall flex, more wheelspin = slower time..

when i went from 16's to 18's i droped upto .3 off my 1/4 times purely because i was wheelspinning, drop it back to 16's or 17's launch it exactly the same, and i pick up .2 - .3 over the 1/4 because i had more traction.

Other then that, and a stiffer ride, no other real difference with bigger rims.

XR6-VCT-2000 · 09-02-2006, 03:54 AM

Hmmm , I was thinking maybe some bigger nice rims , but hearing that - i think my car is a stiff enuff ride as in the vct ( i like it as is - but dont want it to much stiffer - and i remember having lower profile tyres years ago i felt every bump ! ), im quiet happy with its take off at the moment as it is and don't want to loose that. I do actually like the stock rims/sort-mags that come standard on the AUIIXR6-VCT ( not bad ), not a bad size either. For the sake of how much more extra lower profile larger size tyres cost at the moment & the rougher ride i think i might just stick with the orignal rims for now , maybe just lower it a bit more to get rid of some of the gap between the tyres and guards .
It's a nice car allready the AU XR's and there is a point where i will compromise with this car ( as they go good as stock allready imo - for a stock car ! ) as far as weather looks/power means more than compfort - im happy with so to say 50% compfort / 50% power/looks , rather than 90% looks/power & 10% compfort ..lol ..thats just me though , after years of having a XE with a lumpy *** cam , noisy as all ИИИИ exhaust , rock solid susspension etc etc .... i think i've rattled every bone loose in my body and half deaf from really deep resonating etc etc ..lol.. i need the compfort more these days ...lmao

stiddy · 09-02-2006, 10:48 AM

For cheaper than the price of getting new rims, you could get a JMM 3000rpm stall, oil cooler and shift-kit and launch it stupid amounts harder..
Ive been in one I6 will a stally so far, useless's wagon, and god can that thing get off the line... its a 1700kg+ barge and has 2.17 60ft's
the difference is huge, more then any set or rims/tyres will ever give you..

XR6-VCT-2000 · 09-02-2006, 11:21 AM

I would but the missus has to drive it too :( , i remeber having exactelly that / a 3000rpm stall convertor and shift kit with b&m ratched quick shift, parking it in carparks was hell , it was like nothin - then all of a sudden BAM of it goes ..lol , had to ride the brake heaps , ok for me , but not the missus , it definatelly gave me a heaps better launch back then too ;).. im pretty happy with the car as is , is running nice and no problems , i dont need to create any problems ..lol , maybe when i get the missus another car then ill start going mad on mods ..lol

Casper · 09-02-2006, 11:33 AM

Quote:

Originally Posted by XR6-VCT-2000

I would but the missus has to drive it too :( , i remeber having exactelly that / a 3000rpm stall convertor and shift kit with b&m ratched quick shift, parking it in carparks was hell , it was like nothin - then all of a sudden BAM of it goes ..lol , had to ride the brake heaps , ok for me , but not the missus , it definatelly gave me a heaps better launch back then too ;).. im pretty happy with the car as is , is running nice and no problems , i dont need to create any problems ..lol , maybe when i get the missus another car then ill start going mad on mods ..lol

I have the JMM 3000 hi stall in my car, you wouldnt even know its there untill you what to slam it off the line, then you notice it.
My wife drives it around all the time, she didnt really even notice it, just said it now feels a little slugish at 2000rpm or so.
She only noticed it taking off a little quick round a corner one day and just lit up the rears.... she loves it now.

stiddy · 09-02-2006, 11:39 AM

actually, Master G has one in his BA XR6T, and when he took me for a drive, i didnt even know it had a stall until we got to a set of traffic lights and he could stall it to 2500rpm without trying..
if i had an auto, the stally and shift kit would be my first mods without a doubt, before any exhaust, or anything..

XR6-VCT-2000 · 09-02-2006, 01:14 PM

i might have to check them out then maybe , sound like they have improved a bit over the years since i last drove a car with a stall convertor then , cheers ..