PDA

View Full Version : 15" Stock to 17" BBS RK; Performance Differences



TheBestCow
11-13-2002, 02:32 PM
I'm contemplating switching from my 15x7" stock bottlecaps (style E) to 17x8" BBS RK. I need to explain to my Dad how this is not a safety issue. Keep in mind I have Koni Sport Shocks and H&R Sport Springs.

If I understand this correctly, what I need to try and avoid is larger overall diameter, especially with a 4 cylinder, as this will bog down acceleration and also throw my speedometer off.

15x7" with 195/65/15
15" = 381mm
381mm + 65mm + 65mm (rim diameter plus the two sidewalls of the tire, going for overall diameter here) = 511mm diameter

17" BBS RK with 235/40/17
17"= 431.8mm
431mm + 40mm + 40mm (again, rim + two sidewall = overall diameter) = 511.8mm

The RKs weigh less than the stocks, I am assuming though. So with tires the RKs would still weigh less.

Basically I am trying to convince my Dad that the larger rims will not be a safety issue, and, in his words "mess with the engineering of the car" [negatively]. Correct me if I'm wrong, but handling will improve? Any other benefits other than looking a lot better?

Will the lower profile tires on the 17" make them more likely to allow damage [i.e. bending] of the rims? I know the RKs are strong but I'm driving 300 miles each time I go home to college or vise versa, and the interstates aren't exactly perfect, especially at some of the bridges and it really slams into it hard (read as: random drop/jump in pavement height where a bridge meets the road).

Thanks guys/gals!

318power
11-15-2002, 06:25 PM
This question deserves a bump as I have the same concerns!!
Jason

b0rf
11-17-2002, 01:37 PM
You'll be fine--just as safe as any BMW running OE 17'' Rims/Tires.

The bumps may just FEEL harder b/c of your suspension setup.

Jim@tirerack
11-20-2002, 12:58 PM
Kevin,

Everything you mention is correct. You will get quicker turn in response and lateral stability with the 17". You will also improve traction by increasing your contact patch. With the RK being lighter than the OE wheel the 17" package will either be lighter or around the same weight.
With 235/40R17 or the 225/45R17 the overall diameter is about the same as the 15" and would not change the speedometer or odometer on the car.
The wheels will be more likely to bend from potholes because there is less tire to protect the wheel.
If I can help let me know.
Thank you

Jim 800-428-8355-364