Wheels,Tires & BrakesPost Wheel, Tire & Brake related modification information and/or questions here.
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I made it official today, I weighed my Speedmasters. The wheel, the tire and 37 lbs of air in them+ the lugnuts and centering ring = 29.0 lbs. The wheels are supposedly 11 lbs a piece so the tires run about 18 I guess which sounds pretty light. Compare this to my light ass OZs (15.1 lbs, 17x7) which came to 36 with the tires on them, or the stock Si wheels which run about 38 with rubber. This is all on the bathroom scale, but its pretty accurate (my weight on it agrees with the one in the gym and the Dr's office, so either all 3 are equally off, or its right).
Now bolt them on the car, multiply the by 4 for the effective rolling weight since they're unspring.... (36-29)*4 wheels=28*4 corners=112 lbs effectively off the car this year vs. last year's race set up. Believe me, you feel it, A LOT. Both in the acceleration (6% shorter tires help too), but most notably in the steering effort. I switch them, the steering gets so easy its not funny.
I know everyone doesn't care since small wheels aren't "cool", but for those of you who like going fast.... take notes. Lighter is better, smaller is better, lighter and smaller is best.
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yea that is true i should have taken notes and gotten 15x 7 slipstreams or something like that rather then 17' subzeros, i defientely agree with the steering the steering feels weird with a 7.5 in wheel, its hard to learn how to drive the corners
i like bigger, but i like lighter... man i just hit a ****ing curb at 40 mph, i lost control... i poped my tire like nothing, and my rim has a tiny bit of curb damage... i wonder what would have happened if i didn't have my forged rims, i think i wouldn't even have the rim stilll
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I had 15x7's on my '99 vic. Those things definitely were better for performance than the torque-killing 17's I have now on my '02.
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my 15x7 Kosei K-1's with 205/50 Potenza S-03 weigh in at 33 lbs. even with 32psi... my winter rollers (15x7 TSW Edge's with 195/65 Dunlops) weigh in at 39 lbs. and I can notice a huge difference going between the two in terms of acceleration...
hey boilermaker1....i just a flaw in ur math 36 - 29 does NOT = 28...its 7
and did u weight urself w/ the rim tire?.....cuz scales dont give u an accurate rreading at low weight. my friend weighted his and its 36lbs...and when he weighted him w/ the rim tire and it turned out to be 39lbs
he was doing all corners
36-29 = 7 x 4 corners x 4unsprung weight
anyone know how much a 205/50/15 victroracer weight? i cant wait to find out how much different with at least 10lbs off each wheel/tire + the smaller diameter wheel.
Last edited by macrossranma; 04-20-2004 at 08:11 AM.
Originally posted by Civic_Racer9 hey boilermaker1....i just a flaw in ur math 36 - 29 does NOT = 28...its 7
and did u weight urself w/ the rim tire?.....cuz scales dont give u an accurate rreading at low weight. my friend weighted his and its 36lbs...and when he weighted him w/ the rim tire and it turned out to be 39lbs
There's 4 on the car. 7*4=28. I'm not wrong, I'm just doing it in my head and not writing it all out.
Remember that not only are you reducing the Actual weight, but also the rotational Inertia of the wheel its self (By moving the Mass closer to the center of rotation)
THis is the big thing that the guys with the light weight 17s and 18+ forget, that even though the weight of the wheel is low, the rotational Inertia is much Higher with a Larger diamiter wheel = slower acceleration.... Because Acutal weight affects handling, Rotational Inertia affects acceleration.
I have 15" Rota Slipstreams. I don't think I noticed a difference when I put them on from stock. My new Falken tires made a huge difference, tho. Then again, I'm not an autocrosser so maybe I don't notice things like that.
Hey, here's a question. You say bigger wheels have more rotational inertia, so a 12lb 15" wheel is faster than a 12lb 17" wheel. But what about the tire weight? If the 15" wheel and 17" wheel have the same outer diameter (with the tire), would the bigger one still have more rotational intertia?
so yea ... anyone wanna buy my 16" ssr comps? ... the orange OZ's are replicas of the SSR's ... or the SSR's are replicas of ... ah, who knows, they look the same, except mine are silver and weigh 11.5 pounds each...
on another note ... I'm gonna try to buy 17x7 type R rims ... but the offset is +60, would that make it stick out too much or be too much in the fender?
They're not OZs. They're Speedmasters. Why you'd want the ITR rims, I don't know. They're $500 and heavy as hell. +60 pushes the wheel way in, all the offset is built into the brake hat.
well, I would get the itr rims more for looks than functionality ... I like stuff that is rare ... stuff that you don't see on everyday cars. I am also geared more towards performance. Though the itr rims are "heavy", they are not heavy by various rim standards ... there are some heavyass rims that weigh like 25-30 pounds each that people here put on their cars ... ridiculous. Might as well swap a d15 into their car
I haven't seen any pics of itr rims on any car other than an itr ... it would be nice if I got some pics with it on my car ... however, if it wouldn't fit, then I suppose that idea will be thrown out
Originally posted by IronFist Hey, here's a question. You say bigger wheels have more rotational inertia, so a 12lb 15" wheel is faster than a 12lb 17" wheel. But what about the tire weight? If the 15" wheel and 17" wheel have the same outer diameter (with the tire), would the bigger one still have more rotational intertia?
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K&N FIPK II / HP Top Portion Header / Neuspeed Front Upper Strut Bar / RSX 19mm Rear Sway Bar
Generic Rear Upper Strut Bar / 15" Silver Rota Slipstreams (11.8lbs) / 205/60/15 Falken ZE-512's
Originally posted by IronFist Hey, here's a question. You say bigger wheels have more rotational inertia, so a 12lb 15" wheel is faster than a 12lb 17" wheel. But what about the tire weight? If the 15" wheel and 17" wheel have the same outer diameter (with the tire), would the bigger one still have more rotational intertia?
since you asked twice......
Tire weight does make a difference, but think of this...
a bigger wheel will have the total weight of the tire farther from the center of rotation, and a smaller wheel with a taller profile tire on it will spread that weight out more.
Look the the tire calculator. (stock 185/70-14, new 215/35-18) see the black area? thats the tire area of the 18. the white line on the inside is were the tire would start on the 14. so, more of the tire is closer to the center of rotation.
Autocross: Because Life is more fun on three wheels......
"I know Solo only comes one minute at a time, but what an intense, non-stop, fast-forward car control exercise minute it is. Sure, the velocity is higher in road racing, but inside the car it is slow-motion in comparison. In Solo, the turns come like machine-gun rounds. "
Randy Pobst
