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I have 18" BBS LM wheels on my car and absolutely love the look of them, but as the car spends more and more time on track I have been thinking more and more about "down-grading" to 16" or 17" wheels. I have been smitten lately with the modern Fuchs variants (Outlaw, and current Fuchs models), but boy oh boy are people proud of those wheels!
For anyone who has switched to a smaller diameter wheel did you notice a marked improvement/decline in performance/turn in/acceleration/etc.?
I love how the 18s look, but after driving my buddy's varioram swapped SC and noticing the sharper turn in/better feedback it got me thinking on whether or not this is something to pursue further.
Gratuitous picture for reference.
Normally, people go with a smaller wheel and more rubber for the street, and larger wheel with less rubber for the track. This is because more rubber helps to soak up the kinds of bumps and imperfections you see on the road, and actually helps roadholding in that setting. It's also much more comfortable.
Regarding your impressions vs your friend's SC-- have you gotten an alignment done recently that's focused on handling and turn-in? The right caster and camber can transform a car.
I have 18" BBS LM wheels on my car and absolutely love the look of them, but as the car spends more and more time on track I have been thinking more and more about "down-grading" to 16" or 17" wheels. I have been smitten lately with the modern Fuchs variants (Outlaw, and current Fuchs models), but boy oh boy are people proud of those wheels!
For anyone who has switched to a smaller diameter wheel did you notice a marked improvement/decline in performance/turn in/acceleration/etc.?
I love how the 18s look, but after driving my buddy's varioram swapped SC and noticing the sharper turn in/better feedback it got me thinking on whether or not this is something to pursue further.
Gratuitous picture for reference.
The big factor affecting performance is tire OD followed by the mass of the rotating assembly, in this regard 18s can actually be better than 17s or 16s when all the other variables are factored in.
For a 964 where performance is the primary want, 8.5x18 w/ 245/35 & 10 w/ 275/35 tires is a great setup, for a less aggressive install 225/40 & 265/35 tires can be used and 285/30 paired w/ 245/35 front is more aggressive. You can get as good turn in and feedback as a nicely setup 911 by proper setup, 993RS uprights would help this but using wheels that provide a little larger negative scrub radius is the most important thing for the feel part. 8.5 ET48 front wheels do just that.
I tried to go 245/275 but I couldn’t find a 245 in a track tire I wanted to run. So I went 235/275. I recently switched to 235/265 in order to get the extra torque Bill mentions with a smaller diameter tire.
What are the cons of 235/265 vs 225/265? The size delta is about the same, and you get somewhat less staggered and more width up front. Seems win/win, so I assume I am missing something.
I can’t comment on 18’s but I can state that changing from 16” to 17” made a HUGE difference in the canyons. Far less body roll and transitions are much faster/tighter. But I could also feel the added weight which doesn’t allow the suspension to move as quickly over the road. That likely has more to do with my wheel choice than the diameter.
Thanks for the thoughts and feedback everyone. One of the problems with Modification-itis is always looking for ways to improve the car, even incrementally.
I tracked my C2 with 8&10 18's with 225/265 setup for years. I tried 235/275 but it didn't seem to add much grip and rubbed a bit more. The 225/265 gave me more tire options but that car has been retired and I am now running 245/295 on my current track car and will be moving up to 255/315 with my next set of wheels but my car is setup for this.
The biggest limitation with 17s is tire width. The widest rear tire I can find that would take to the track here in Japan in a 17 is 255. That said while and 18 inch wheel with a small profile tire gives better feedback I’m not convinced that it is necessarily faster in the same width.
Additionally My understanding is that a 17 inch wheel and tire set with the same OD as an 18 inch set will be slightly lighter. In my case with the tires that I run (yoko Advan 050) my 18” option would be limited 265’s in the rear. For me (not racing- just having fun at the track) I doubt that extra 1cm is going to matter.
If this is a car that will see street use and your into the Fuchs style wheels on a 17 I’d consider 225/255’s on Zuch’s Made by Fiske. There light and great looking to boot.
I tried to go 245/275 but I couldn’t find a 245 in a track tire I wanted to run. So I went 235/275. I recently switched to 235/265 in order to get the extra torque Bill mentions with a smaller diameter tire.
What are the cons of 235/265 vs 225/265? The size delta is about the same, and you get somewhat less staggered and more width up front. Seems win/win, so I assume I am missing something.
a 235/40 x18 is a good match for a 265/35 x18, that combo will have a bit less understeer than a 225/45 & 265/35, wheels make their own inputs here to, 235/40 on an 8.5 will have less understeer and better turn in than a 235/40 on an 8. what you use just depends on what tweeks you want from the basic suspension characteristics.
in back I like the 265/35 better than 275/35 assuming 9.5 or 10 is used. The 265 is .3" shorter and will have less inertial & gearing cost and gives up little in grip unless the 275 is on a 10.5 or 11
I can’t comment on 18’s but I can state that changing from 16” to 17” made a HUGE difference in the canyons. Far less body roll and transitions are much faster/tighter. But I could also feel the added weight which doesn’t allow the suspension to move as quickly over the road. That likely has more to do with my wheel choice than the diameter.
tires don't add to or subtract from body roll except to the extent that you can go faster or slower through the corner. They can certainly make a difference in transitions as does the influence of the wheel width & ET.
tire weight and OD makes a difference in gearing & inertial cost, but that is seen most in acceleration and deceleration. In extreme cases I've seen 45lb-ft loss from a wheel/tire change
The biggest limitation with 17s is tire width. The widest rear tire I can find that would take to the track here in Japan in a 17 is 255. That said while and 18 inch wheel with a small profile tire gives better feedback I’m not convinced that it is necessarily faster in the same width.
Additionally My understanding is that a 17 inch wheel and tire set with the same OD as an 18 inch set will be slightly lighter. In my case with the tires that I run (yoko Advan 050) my 18” option would be limited 265’s in the rear. For me (not racing- just having fun at the track) I doubt that extra 1cm is going to matter.
If this is a car that will see street use and your into the Fuchs style wheels on a 17 I’d consider 225/255’s on Zuch’s Made by Fiske. There light and great looking to boot.
Both Hoosier and Maxxis have very tasty 275/35 x17 track tires, @24.6" OD these are very efficient and(depending on the wheel) almost as grippy as the 285/30 x18 which have the same OD
Both Hoosier and Maxxis have very tasty 275/35 x17 track tires, @24.6" OD these are very efficient and(depending on the wheel) almost as grippy as the 285/30 x18 which have the same OD
Jealous! I’d have to import those. Here in Japan availability is limited to 255. The 050 USA great tire though.
OP-Sounds like your answer is to get a set of 17s and keep the 18th for the track try both.
Bigger and bigger wheels and tires are the biggest fallacy to a good handling car. Not only is it uncomfortable and prone to wheel damage on public roads with minefield like portholes, it also adversely have negative good handling attributes. Look at any F1 wheel/tires setup and you'll take note of the tire profiles having quite substantial sidewall depth. There is a reason because even on F1 circuits, the tarmac gets bumpy and the softer sidewall becomes more compliant to cushion the bumps,. Otherwise the car will dance around like a pogo stock. Bigger wheels/tires/spaces, and stiffer suspension sure makes the car looks good, but vanity and performance does not necessarily go together.
Bigger and bigger wheels and tires are the biggest fallacy to a good handling car. Not only is it uncomfortable and prone to wheel damage on public roads with minefield like portholes, it also adversely have negative good handling attributes. Look at any F1 wheel/tires setup and you'll take note of the tire profiles having quite substantial sidewall depth. There is a reason because even on F1 circuits, the tarmac gets bumpy and the softer sidewall becomes more compliant to cushion the bumps,. Otherwise the car will dance around like a pogo stock. Bigger wheels/tires/spaces, and stiffer suspension sure makes the car looks good, but vanity and performance does not necessarily go together.
Amen to this. A lot of my friends have taken to replacing their stock wheels with smaller wheels and running thicker rubber. Wheel diameters on newer cars, especially, are getting downright ridiculous.
10-09-2019, 04:28 PM
Wheel size effects on handling/accelleration
