[cgnahc]

Looking to track using 19" BBS. Has anyone tracked using 19" rims? I know 18" is preferred but it's not in the cards right now. I have old 17" with used RFTs to play with.

[TTBM]

19's are fine but if you want to get serious go with 17's or 18's. do you plan on tracking a lot?

[S4to335]

Lots of reasons not to go with 19s on track...here are a few of mine:

1) Not many R compounds offered in 19 inch size...or 19s in general, much more options in 17 and 18.
2) 19" tires are more expensive than 18s..or 17s.
3) rim is too close to pavement..and if you hit some debris on the track..or a berm..you are DEFINITELY going to bend/break/damage your 19" rims.

[LOLrance]

I say just use the 17" and get rid of those run flats. That should be good for track.

Tracking with 19"s is a big NO in my book.

[Lane]

Originally Posted by S4to335

3) rim is too close to pavement..and if you hit some debris on the track..or a berm..you are DEFINITELY going to bend/break/damage your 19" rims.

There are no potholes on tracks. It is more likely to bend 19" wheel on a hwy pothole.

Both 19" and 18" should beat 17" lap times.

[S4to335]

I beg to differ. where did you get that 19" rims would beat lap times of 17" rims...the most important thing is unsprung weight...and probably rim width..there are good 19" race wheels out there..but Fikse, Compomotive, and other similiar makes aint cheap.

Oh..and on tracks..you get two wheels off..and there is usually a nice "pothole" at the end of that section...before you get your right or left side tires back on the track. Yes, there is no "pothole" in the middle of the track..but some berms..like the ones at Laguna before they replaced them...were as big as alligators and totally upset the car when you hit them...BTW, I have seen many bent rims on race cars...including mine.

[Lane]

To avoid unsprung weight use light forged 19" wheels. The tires will weigh a lot less than the same width higher profile tires of 17" wheels. No major differences on the total wheel+tire weights though.
Less sidewall flex with 19" provides excellent response and keeps rubber level on the ground. More rubber on the ground, more grip.

[uberschnell]

Originally Posted by Lane

Both 19" and 18" should beat 17" lap times.

Misinform"ing" post of the year nominee.

Most high performance tires have reinforced sidewalls for added stiffness. 19" provide side-wall stiffness as a result of less area, not design. I'd be happy to compare my 17" k1 track set up overall weight to any 19" set you got.

[Lane]

Originally Posted by Magna3

Misinformed post of the year nominee

Please, share if you have some data, info or theory. Thanks

[Hegemony]

Originally Posted by Lane

Please, share if you have some data, info or theory. Thanks

That's a two way street.

[Lane]

See e.g. Sport Auto 7/2007 (german)
On dry (slalom&lap time Hockenheim) the best was 20" before 19" and 18" (On Porsche 997)

[uberschnell]

Consider the fact that whether you go 17, 18 or 19, the applicable tires will result in more or less the same diameter. So the two factors that effect performance are sidewall stiffness and weight. There are far more choices for racing tires in the 17 and 18 inch category, and again, most all racing tires address side-wall stiffness in their design. Weight wise, no advantage to the 19’s for tires (example: Dunlop Sport Maxx 255/30/19 = 26lbs, 255/40/17=26 lbs). Yet, wheels will be anywhere from 2 to 6 pounds lighter for a forged 17 vs. forged 19. So any advantage that you may get from stiffer sidewall on the 19 will not make up for the un-sprung weight penalty over the 17, or 18. Add to this the much bigger selection of race tires available in 17 and 18 inch applications vs. the 19 and you can see why making an argument that the 19 inch wheel will give you better lap times then a small wheel makes no real-world sense.

[uberschnell]

Originally Posted by Lane

See e.g. Sport Auto 7/2007 (german)
On dry (slalom&lap time Hockenheim) the best was 20" before 19" and 18" (On Porsche 997)

I could not pull anything up re this report. Where the tires the same width on all three rims?

[Hegemony]

Originally Posted by Magna3

I could not pull anything up re this report. Where the tires the same width on all three rims?

Would probably need contact patch, section width, and outside diameter comparisons to be far, don't ya think?

[uberschnell]

Doesn’t rim width also play a factor in contact patch? In an apples to apples comparison (same width tire, same width rim, same brand) between 17 and 19 inch rims I think the 17 has the advantage due to weight.

[Hegemony]

I'd assume, if we're trying to compare apples to apples, you'd have the same rim width at each wheel diameter. Seems like it would throw in too many variables to vary that as well.

[uberschnell]

Should mention that the 17 inch rims scarcely fit over stock 335 brakes. Any bbk and you would have to go 18, maybe 19.

[Hegemony]

the wheels in the pics in my signature are 18's and fit with plenty of room to spare on a 6 piston front BBK

[cgnahc]

I believe I can track with 19" on some stiffer sidewalled tires, but I have the Generals for my daily use. It's true that there is more room to damage my 19" rims, but how about I increase the tire pressure another 5 psi. I'm thinking give up a little more grip and not roll the sidewalls as much. Wishfull thinking? I plan to do about 2-3 events 2008. Tracks at Willow Springs & Buttonwillow should be rim friendly. Laguna Seca & Parump?

Holding on to my 17" 161 and maybe replace rears with nonRFT and keeping fronts as is with RFTs. Weights will drop with nonRFTs... that's a plus.

[uberschnell]

No ones arguing that you can't track 19's. Heck, you could track 20" spinners if you wanted.(maybe not)

http://home-and-garden.webshots.com/...48758236yukaQH

[heavychevy]

19's have actually been proven to have a bigger contact patch that smaller wheels. Contact patch increases with diameter and width. This is why you see 19 inch hoosier R6's and Michelin Sports Cups not to mention many Porsches, Vipers, Vettes, Ferrari's, Lambos all coming with 19's. It's the biggest size you can get while still keeping "some" tire and not affecting the ride height too much.

Now whether the contact patch can nullify the unsprung weight, I dont have an answer for that. But there is certainly much more contact patch on a 19 inch wheel than a 17 inch wheel with a fat tire assuming the widths are close.

Run the 19's, you'll be fine. although the arguements posed by S4to335 are all legit, it will cost more, but you shouldnt worry about breaking a wheel, chances are that can happen with any size, but the selection and price will get you.

[judec]

well, not sure I understand U, chevy. Maybe it's because I assume wheel diameter and tire outter diameter are two different things. Also preferably U keep your tire diameter constant and as close to stock as possible. Also we abstract from changing tire width, it's also constant (lets say 245). So how will the contact patch increase by changing from 17" to 19" wheels?