6 inch vs. 5 inch tires on 125 shifter

lloyds1 · Joined: 08 Aug 2001 Posts: 7

What are the advantages / disadvantages of the 6 inch vs. 5 inch tires. I am new to the sport and seems to me the more rubber the better. I dont know if driver hight and weight plays are role, I am 6'1" and 235lbs.

Oscar Aguilera · Joined: 18 Jul 2001 Posts: 1614

6 inch are not allowed in most classes. You can use them in some RR series, special event street races, or if offered as a local option. 6 inch are better for the "big" guy because they offer less side wall flex. They are no longer used at any FIA events so tire compounds in the 5 inch category are better with up-to-date technology.

Example of classes: Here in Houston we race G-1(5 inch BS SKUSA license) or 125 heavy (local option class where 6 inch Vegas are allowed) Southwest Road Racing allows 6 inch or 5 inch in their 125 classes.

If you switch during testing from one to the next you also have to adjust your gearing.

[ August 09, 2001: Message edited by: Oscar Aguilera ]

Michael Taksa

Wow, Oscar, are you saying that the OD is so much different that you have to change gearing??? Somehow I think it is not the case.....
BTW, I am on 6's, because I don't want to invest in new rims... Local Club has "open tire rule" But if I do, I will go the route of 5 inches.

Matt Kull

OD is 1/2 inch bigger on a 6" wheel changing the overal ratio.

Marc Miller · Advertiser Joined: 18 Jul 2001 Posts: 1834

Oscar and Matt are both right... you may have to go one complete gear to get the same ratio.

I have had to do that before. I've also had to check my gear ratio difference when switching from Bridgestones to MG's this year. Tire circumference changes, so does gear ratio.

MM

lloyds1 · Joined: 08 Aug 2001 Posts: 7

Thanks for the info.

My track allows 6" tires.

So do you think the benefit of less side wall flex and bigger contact patch of the 6" out wieghs the newer tire compounds of the 5"?

Michael, I noticed you live in Boston. Where is your local club located?

Michael Taksa

Well, It is not so "local"

OVRP, www.ovrp.com much closer to yuo then me. But closest one to Boston.

lloyds1 · Joined: 08 Aug 2001 Posts: 7

Thats where I plan to do most of my driving. Hmmm....maybe I can trade you a set of my 5s for your 6s. How often do you go there? What chassis do you run?

Michael Taksa

I do not go very often. Once every month or so, I run 97 Haase Scorpion. On the rims: I would like to have a few setts, so I am not willing to trade mine, just have to get enough money to buy 5''.
See you at the track.