Weight of STi rims?

[AdamW]

Does anyone know the weight of combined STi rim & tyre (on MY08)?

[sundayDriver]

No, but I asked this question to Rolfe Classic Subaru in Canberra last year and this is their reply
>>>
I have been forwarded your e-mail in regards to your questions about STI ENKEI wheels.



1) how much does the STi wheel weight (without rubber)?

2) how much does my GT-B wheel weight (without rubber)?

3) if I put buy the STi rims, will I need to do any other modifications to the suspension to use the STI rims? (because my rims are 18x7 and the STi ones are 18x7.5)



I have spoken with an array of people regarding your questions and have come up with the following:

1) I have spoken to our STI master technician in our w/shop and he believes they are around 7.5 -8.5KG

2)Our master technician believes they are around 11.5-12.5KG, the difference being about 4 kilograms per wheel (which is a great weight saving!)

3) There should be no need to alter the suspension set up if these wheels were to be fitted, their should be ample room in the guards to fit as the width difference is only Half an inch.

STI parts offer two different versions of these wheels the difference being in colour. Shadow chrome and Charcoal. With no difference in price. ($3344 without tyres, for 4 wheels)

>>>

[AdamW]

Damn #%$#&$.. I was told by peeps back home that my new wheels & tyres weigh about 25kg.. That seems awfully heavy for a supposed light weight expensive wheel to me thou...

[3rspecb]

Does anyone know the weight of combined STi rim & tyre (on MY08)?

I presume you have a full size spare? if so take it out and weigh it, alteast you have a start.

contact bridgestone and ask them the weight of the RE050a tyre, then - from the total weight of your spare to get your answer.

It might not be 100% but it's better then a so called STi technician's word.

[AdamW]

I presume you have a full size spare? if so take it out and weigh it, alteast you have a start.

I am still over in the Jungle (central PNG) at the moment but have asked the peeps back home to do just that.. They rarely check their emails thou..

[sundayDriver]

It might not be 100% but it's better then a so called STi technician's word.

so you prefer to trust the word of a bridgestone technician?

[PHAT GT]

this maybe some help with the weights

below rims are all same as fitted to STI Libertys (Enkei same wheel we are talking about) weights are from STI Japan

18x8 +50.... 9.5kg as fitted to a STI WRX Jap spec
17x8 +50....8.8kg

STI Japan dont list a weight for the 18x7.5 (fitted to the AUS Liberty) but do the math and you'll see that they would be around the 9+kg mark unlike the 7.5-8.5Kg quoted by ACT subaru

[AdamW]

this maybe some help with the weights
below rims are all same as fitted to STI Libertys (Enkei same wheel we are talking about) weights are from STI Japan
18x8 +50.... 9.5kg as fitted to a STI WRX Jap spec
17x8 +50....8.8kg
STI Japan dont list a weight for the 18x7.5 (fitted to the AUS Liberty) but do the math and you'll see that they would be around the 9+kg mark unlike the 7.5-8.5Kg quoted by ACT subaru

Thanks Phatman..

Just managed to get the peeps back home to weigh the wheel - MY08 stock STi rim with stock tyres and came to 20.3kg each..

My new wheels (inc tyres) are 25.6kg each..

They say the equivalent sprung weight is about 8 times the unsprung weight..

So an extra 5.3kg at the wheel is approx 42kg per wheel or 170kg total of equivalent extra weight… well that kind of sucks…

[Arith]

Well, they are 19's compared to 18's after all. But like Phat says, they probably won't amount to too much difference on the road.

[AdamW]

When I had my last car I went from light weight 15” simmons rims to heavier 17” and I noticed a fairly big difference.. Car just didn’t feel as responsive.. And it was a 5L V8.. So I am sure a 2.5L will feel it even more.. Guess I will never know thou, as it will be five weeks since I drove the car last time.. 170kg is a fair bit of extra equivalent weight to be carrying around..

[Arith]

I dunno. From my experience when I had the MY05 GT, I went from the factory 17's to the heavey HP Design chrome 19's. The tires they originally slapped, Falkens, made the car feel like crap and sluggish as anything. But after switching over to Kumho tires (keeping the same wheels), the car felt alive again, if not better. Guess I'm just saying there are a lot of factors involved, and you can't always just go by the weight of the wheels on how the car feel like on the road.

[Ric]

Just doing some quick calculations on tyre weight, from published figures for Bridgestone 050A tyres.

215/45R17: 22 lbs = 10.0 kg
215/45R18: 24 lbs = 10.9 kg
225/40R19: 27 lbs = 12.2 kg

[AdamW]

Also just doing some quick calculations… Using moment of inertia & kinetic energy sums to work out the energy required to accelerate a wheel of diameter 19” with a 5.3kg (as this is the extra weight per wheel).. Also assuming an even weight distribution across the wheel/cylinder (k=0.5).…

0-20kmh… 0.2kW… assuming it takes 1 sec
20-40kmh… 0.3kW… assuming it takes 1.2 sec
40-60kmh… 0.4kW… assuming it takes 1.2 sec
60-80kmh… 0.6kW… assuming it takes 1.2 sec
80-100kmh… 0.7kW… assuming it takes 1.4 sec

Total of 6 sec to get to 100kmh..

I guess these do show a pretty minimal power loss..

Also if you assume the extra weight of the wheel is all at the extremity (near tyre), giving it a moment of inertia constant of k=1 (this is worst possible scenario) it still only gives small figures..

0-20kmh… 0.3kW… assuming it takes 1 sec
20-40kmh… 0.6kW… assuming it takes 1.2 sec
40-60kmh… 0.9kW… assuming it takes 1.2 sec
60-80kmh… 1.1kW… assuming it takes 1.2 sec
80-100kmh… 1.4kW… assuming it takes 1.4 sec

emmm I should probably get some real work done now…

[GTSPECB STI]

LOL Adam

Good work and now we know who to ask when we need physics and maths calculations, now get back to work!!

[CJ1177]

Just managed to get the peeps back home to weigh the wheel - MY08 stock STi rim with stock tyres and came to 20.3kg each..

My new wheels (inc tyres) are 25.6kg each..

Well that makes my 20" rims (inc tyres) not look to bad then, I've got mine off at the moment so I put one of them on the scales & they came in @24.0Kg assuming my digital scales are reasonably accurate

Chris