180 vs 190 rear tire

[entropy]

I am currently running a Pirelli Dragon Super Corsa Pro  180/55ZR17 SC2 and like it fine, but a pal o' mine into RR asked why not run a 190 for potentially better straight line traction.

Any thoughts??

[narider]

Everything's not always as it appears in the numbers. Depending on rim width and tire aspect ratio a 190mm tire can (and many times does), have less of a footprint (contact patch) then a 180mm tire....the narrower the rim the moreso this will hold true. Hopefully others will give some specifics on common rim widths and tire brands.

Also take into consideration the weight difference between the two if it's at all discernible or matters to you. And more contact patch for traction also translates to more drag at top end if your traction outweighs your available horsepower (Bill Warner is certainly expempt from the last part of that statement, and I imagine will prove to change some of the fast guys minds on the subject as he progresses forward). 
Todd

[Racetrack14]

I have run both tire sizes at the Texas Mile and did not see a great deal of difference. It was not a good test because the tires were different brands - Bridgestone and Michelin. The 180 Michelin was maybe 1 MPH faster on a NA Busa.

The 180/55 is designed for a preferred rim width on 5.5" and the 190/50  for a 6" rim width. In the drag racing world on the SS1000 almost everbody is running the 180 on a 6" rim for a combination of reasons - good contact patch, lighter, taller for gearing and cheaper.

I prefer the 190 on the turbo LSR Busa at Texas because of the wind. You have to think about the side contact patch when the bike gets to leaning way over at Texas. Running on the rim width designed for the tire gives me more of a comfort factor at those speeds. When you increase the width of the tire with a wider rim the side contact patch can be compromised.

A good way to check or compare the contact patch is to take a white sheet of paper, jack the bike up, place the paper under the tire, you can dust it with carpenters chalk and sit on the bike, raise it back up and see what it looks like. You can just roll it through to check the width. A tire with a larger circumference will also add to the the contact patch. Some times the rules only govern the width of the contact patch so running a 17" tire versus 15" is better if your stock car racing.

Racetrack

[bobu]

I think a taller tire, 55 opposed to a 50 could have a larger patch in curves and smaller on straights, like he said rim width might affect this also.

[entropy]

thanks for the info!!!

Mr Racetrack14,
will you have yr team at the Oct Mile???

I'll wear out the 180 i am using now, but am considering options for next spring.

[Racetrack14]

thanks for the info!!!

Mr Racetrack14,
will you have yr team at the Oct Mile???

I'll wear out the 180 i am using now, but am considering options for next spring.

We are planning on being there. I may just let Jen run the bike but I may hop on it one time and make another pass over 200. I plan on starting work on the bike after we get back from running at Indy. I will probably take the bike to San Antonio and let Jen shake it down a few times there and work on the tune some more in the lower gears. Looking forward to seeing the whole gang back at the Mile. Let's hope for good weather and low winds.

Racetrack

[TRNorBRN6001]

It'll be good to see you all at the Mile in Oct. Sorry I missed you all over at JC, but I went on vacation right after Maxton.