shadwsndst

ive been in the market for rims for some time now, looking at top of the line, middle weights and even knock offs. i got into a conversation with my uncle whos a engineer of sorts and asked what made forged rims so expensive vs shot peened or cast or whatever... he gave me a quick rundown: forged rims are stronger/ less susceptible to flex in racing situations which equates to a more precise "feel" but more brittle or prone to fracture. i was changing the oil on my friends DC5 who has CE28's and noticed some hairline fractures on the inside of the rims... it was extremely discouraging to me seeing a set of 2100$ rims with signs of stress, with no track time. the rims are probably a 8.5-10 in terms of condition and have not been run up any curbs. 2000$+ is a lot of money to be spending on something that is prone to fracturing with regular use and made me think twice about what i should be spending my money on. as of now i will not be tracking my car so i do not need the extra strength of a forged rim but my eyes are always drawn to that style ie: Volk CE28, LE30, Prodrive GC-07 etc mostly because these rims are the choice for most show or race spec S2000's. Any suggestions or pictures on a "sport" (im not one for deep dish or polish lips) oriented rim, something unique that will last and be between 1000-2200$ (no rotas please)

if it matters, i am looking for something to compliment the V2 Cwest, amuse, or new AP2+CR lip front ends. and will be most likely rolling or getting wider fenders (no wide body)

shadwsndst

should i even worry about rims getting hairline cracks in them?

nightcrawler7188

check out the work emotion xt7. they even look way better in person. they're cast but they're still pretty lightweight for 17s.

shadwsndst

does it matter if they crack?

INTJ

Don't run cracked rims. I don't want to have to swerve around you, or get tied up by the gapers at your accident.

ZDan

Forged 6061-T6 has a much higher yield strength than sand cast 356-T6 or die cast 380 alloys. For this reason, you can make lighter wheels for the same strength or fatigue life with forged. Since they are thinner wall, they are not "less susceptible to flex". Modulus of elasticity is the same (close anyway) for all aluminum alloys, so less material/less weight => less stiffness. Racers use forged rims for less unsprung and rotational mass. Wheel "flex" shouldn't be a huge issue, if they're designed to have any kind of fatigue life at all..

Cast rims can and do crack as well as forged.

Given enough load repetitions, any aluminum structure will eventually crack (no fatigue limit stress).

Wheels designed for racing are lighter weight and more prone to cracking than wheels designed for road usage. Frequently they'll be labeled as racing use only, because they don't meet required standards for fatigue life for road usage.

Whether a wheel develops cracks is not so much a function of whether they're forged or cast, but rather what kind of margins they're designed to, and what kind of environment they're actually exposed to, and for how long/how many miles.

ZDan

Long/short, don't assume that the type of construction (forged, sand-cast, PM cast, or die cast) will tell you anything regarding whether it is more or less prone to cracking.

shadwsndst

^^^you my friend are awesome, thank you for spelling that all out for me. i was just a little concerned from seeing what had happened to my friends CE28's. i don't plan on doing any hardcore tracking anytime soon, but don't want to have to deal with these hairline cracks in a 2k$+ set of rims.

i wonder if a suspension setup has anything to do with wheel stress. more aggressive valving/ spring rates not absorbing enough of the road trauma... then again, after the tires, they are the first things to bare the load of the road... i am by no means a racer, engineer or mathematician.... i just want my big ticket purchases to be good ones.

nightcrawler7188

i'd think that the stiffer the suspension, the more force acts on the tires, and the greater the force acting on the tires, the greater the stress on the wheel.

PJCC

Also, racing equipment is thoroughly(?sp) checked before, during and after every use by people who know how to identify these wear signs.