Hello all

In a little dilemma.. Should I get forged rims or cast ones GIVEN a S$1500 difference in price? Both rims are 18" and would be fitted on a 6AT.

The forged rims in question are about 8kg a piece and the cast ones weighing in at about 10kg a piece.

Can the extra $1500 be spent on mods which would make up for the extra weight? Thanks for all the help.

 

U still thinking about it dude??!!

I thought u've already decided..

 

Cast Rims has a longer life span.

Example
1) When you drove over a hole accidentally? the car will sink in for a moment and will be out of the hole immediately. But this in and our vertical movement may or will cost the Rims to be out of shape. cos the forge wheels are quite SOFT.

2) everytime u change tire, dent markes will appear to be more promp then Cast rims cos Cos is softer.

 

Go for forged...its alot better than cast rims...unless ur cast rims r from advan...
coz apparently, the casting technology of advan is comparable to forged...
at least thats wat i was told?

Anyway, i'm using advan rims...think its quite light...ard 7-8kg if i'm not wrong?
At least lighter than the stock rims lah...heehee...

 

forged rims are supposed to be much stronger (and of cos, lighter) than cast rims.

 

Forged Stronger.. YES, less likely to crack but will deformed more easily compare to Cast.


Forged Process - The material are heated and are hammer to its shape. during this process the molecules are hammer closer together to make the bonding between the molecules stronger. as a result the rims are not easily crack.
(just like the same process those ancient chinese used to made swords)
But they are usually make of softer material so that the rims are lighter.
So Forged Rims may not get cracks as easily like Cast rims, but there are more likely to be deformed due to it lighter and softer material used.

But u cant compare a $2000 Forged rims to a $100 cast rims.
got to compare those expensive cast rims with those forged rims around the same price, cos there are cast rims make from very good material as well.

 

Ok.. maybe its easier to tell you what the rims in question are; Forged - TE37 and Cast - Work Emotion CR Kai.

For $1500, i could probably get an after market exhaust for a couple of hundreds more, but would the gains from such a mod make up for the extra weights from the cast CR Kai?

I'm sorry if this is a stupid question, but haven't been able to find anything on this topic.

 

It would take a "Very Sensitive Guy or Girl" to be able to tell the diff between both rims.
We are talking about around 1.5kg differences between one rim right? so ask your self can u tell the diff when your rims are 1.5x4=6kg more? if not , dont waste the money on the forged rim.
Unless u really love the design and looks of the forged rim so much that u have to buy them, then thats another case. (its not about the looks but not the money)

 

Hi

Urs is an AT car. I may be slammed here but we know AT car has less power than manual. If u have the $$$, u shld get as light a rim as possible. This is concerning unsprung weight. Other bro can help here.

I did not specify cast or forged cos some cast rims can be very light as well (Advan comes to mind). Forged rims does indeed exhibit more flex but it depends on where u drive and how u drive.

Since rims is a personal thing, u may like the look of cast rims and prepare to sacrifice on performance. Then go for the cast one. Only u know.

Cheers

 

I got forged 17". Its way lighter than the stock 16". Definately better in accel, stop and handling.

1.5kg is not alot. But when you consider the reduced rotating mass. 1.5kg is actually alot. Plus its unsprung.

Casts ones are heavier because of the minute imperfections so rims makers have to use more metal. Personally, i know at least 2 people who had sheared cast rims. One is on a kia rio ferrying 4 people going over a hump. So is it a wise investment on the rx8 especially people who track? I rather err on the side of caution and spend that little more.

 

6kgs may not sound like much, but like Emperor pointed out, the majority of the 6kgs are rotational mass as well as unsprung weight. There was some study done (but I have no reference to it) that unsprung weight is equivalent to 4x normal weight. So lugging 6kgs of unsprung weight has the equivalent effect of lugging 24kgs of the car's bodyweight around. I can't verify it so please take it with a pinch of salt.

 

I also hear something like that but cannot remember where.... total abt 4 time savings.

Dont quote me oso, I fail my science hehehe

 

it's called rotational inertia. a function of k * Mass * Radius^2. it's generally true if wheel radius is the same with reduction in weight.

however, do note that an increase in radius plus a reduction of mass does not always mean improvement, given the Radius^2 factor.

 

Thanks for all the responses people. I've decided to get the TE37s.

So my next question is which tyre profile, rim width and offset to take.

For the rims, I'm undecided on 18 x 7.5 or 18 x 8.5 and the offset +30 or +40. Stock should be +50 if i'm not wrong, but I would prefer my wheels to be slightly protruding out. Would +30 be too much and rub the fender? I don't intend to change suspension or get lowering springs for the moment.

For the tyres, whats a good profile? 235/40/18? Stock is 225 right? I remember reading somewhere that for street use, getting a rim width which is 90% of the thread width is optimum.

Would appreciate any type of advice or opinion on the above matter. Thanks! By the way, specs for the TE37 can be found at: http://www.rayswheels.co.jp/cgi-bin/...modelName=TE37

 

Hi

Next to the specs of rim, VR also recommends wat the configuration for diff cars.

For 18", u can see below for RX8. U can also check other sizes (17" or 19"). They recommend staggered for RX8.
http://www.rayswheels.co.jp/cgi-bin/...37&inchIndex=5

If I were you, I'll consider 17" as it is an auto car.

Cheers

 

... and bigger rims (on auto) does not mean that it will make the car slower. Thought we had proven that already.

 

sart lor...... 19" rims but outrun others on smaller rims lor.....

 

Ok.. but i'm not intending to use staggered..

would an offset of +30 be too wide for the car and rub fender? Anybody has +30 offset?

What do you guys think of this setup?

18x8.5, offset +30 and 235/40/18 all round?

 

8.5 +30 may rub... if 8.0 +30 shld be no issue. Check with ur rims/tyre supplier

 

not sure if it fits but you may want to know that your setup equates to 26mm additional outward protrusion compared with stock 18". sounds agressive and may affect handling. on rubbing of fender, etc, i supposed it's ok for the back but not sure if it's ok for the front wheels.

why not stick to volks' recommendation? 8.5 w 40 offset for the front (16mm additional protrusion compared with stock 18")?

 

Sorry u mean same driver, same car, same type of rims, same type of tyre, just diff rim and tyre size and bigger rims will not lose out??
Weight doesnt count??

Thanks

 

the question shld not be the size of the rim but the amount of contact your tyre have with the road surface. tyre with larger width (usually comes with bigger rims) need more frictional force to run the same distance hence acceleration and fc performance will be less than the same car running smaller rims.

 

Did anyone notice why race cars usually run 17" and some 18" but never 19"?

Weight does matter. If 10 nm of force moves 2 kg 10 metres. This same amount of force may only move 4kg 5 metres. If speed is constant. So logic says if the torque stays the same then if weight is increase, it should take longer to accel, deccel over the same distance.

And then theres the overall size of the wheel. Big wheels turn slower than small wheels; equates to less torque transmitted. Maybe thats why lorries have small rear wheels.

 

We had tried the following :
1) Same Car (same set-up)
2) Once on 19" (F 245 / R 275) and another on 16" (stock) on a different day
3) Same driver

Conclusion is the tyres play a big part in the test where 19" using conti sc2 for front and michelin ps2 for the rear, 16" on totally "wan chng" RE040.

 

Sorry, I don't know if race cars uses 17" but i know u are ..

....not mathematically inclined enough to reply your weight x force + accel - torque question. sorry .........

why are we on lorries wheels ?

End of the day, wheels are quite personal and voice down to the purpose of performance or show car look only. Yes, i do love to have the 22" bling bling wheels