wannabe
Pro
Posts: 1931
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posted March 18, 2003 02:04 PM
M/T max tire pressure
OK, as a lot of you guys know, I've been running the 7" Mickey Thompson slick on the back. I've done a lot of experimentation with tire pressures, but I've just about confused myself. At the last test & tune, I went up as high as 12psi in the slick, and I'm still bogging off the line. (I just dump the clutch....no slipping.)
Everyone else is telling me that they run around 7psi on the MT slick. Have you guys ever heard of anyone running more than 12 psi on a MT slick or should I just try to lower my wheelie bars a bit to unload the rear a bit?
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"There are only three sports: bullfighting, motor racing, and mountaineering; the rest are just games." - Ernest Hemingway
  
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zrxdean
Needs a job
Posts: 2225
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posted March 18, 2003 02:58 PM
I'm no pro, but I think we need some more details. Are you running a lockup clutch? What RPM do you leave at? What's your gearing?
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wannabe
Pro
Posts: 1931
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posted March 18, 2003 03:13 PM
Sorry, Dean. I forgot.
I'm running 16/48 on the stock wheelbase with wheelie bars. I don't have a two-step yet, so I'm just dumpinig the clutch off the rev-limiter. I'm not running a lock-up. I'm using the Muzzy's clutch pack and billet basket. Right now I have the wheelie bars set at 2" off the ground with my fat butt on the bike.
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"There are only three sports: bullfighting, motor racing, and mountaineering; the rest are just games." - Ernest Hemingway
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zrxdean
Needs a job
Posts: 2225
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posted March 18, 2003 03:29 PM
Most folks use a lockup to get it to slip off the line. You can set it up with low static spring pressure, to keep it from bogging, and a little weight on the snowflake arms to keep it from slipping once you're up and running. It'll be hard to make your tire spin consistently enough to run the number.
Didn't someone say once that bar would lead to a slick, would lead to a two-step, would lead to a lockup? 
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wannabe
Pro
Posts: 1931
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posted March 18, 2003 03:37 PM
I knew about the bar leading to the slick. I found out about needing the two step at the track. (It's on order.) I had no idea about the lockup. Dang, I have more research to do. Hopefully, this road doesn't necessarily lead to an air shifter too. ;-)
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"There are only three sports: bullfighting, motor racing, and mountaineering; the rest are just games." - Ernest Hemingway
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Cowboy
Pro
Posts: 1061
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posted March 18, 2003 05:45 PM
those guys telling you to run 7 psi are running a 18 inch slick right?Deans right about the lockup.You should try taking the 3 heavy duty muzzy springs out and running all stock springs.As long as your not running a dry shot you won't be slipping the clutch up top.Air shifter would help a lot also for consistancy and you could then run more gear so you finish at the top of 6th.12 psi is not too much for that slick in my book.We used to run between 10 and 14 psi and leave on the rev limiter with 17/51 and it would carry the front tire through the first 3 gears.This was with the stock clutch and basket also.Ran low to mid nines all year without changing the clutch(i don't know how either).
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RedBull
Expert Class
Posts: 406
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posted March 18, 2003 05:46 PM
You don't need a lock up ! ( YOU NEED AN AREA RUG ! )
I'm just joking...
I know that my 11 doesn't make as much power as your 12...
And your on the right track with setting the bar lower,
I leave on all four wheels, unless it starts charging...
My bike doesn't have a 2 step,
however that will help you be consistant.
Instead of just throwin' the clutch away,
try easing it out of your fingers, gently, but quick !
It's going to be a whole new ballgame for me with this 60" program !
Red, *<(:{)-
____________
1998 Prostar West Super Gas top ten.
1999 Prostar West Super Gas Champion !
2000 NMRA / Prostar Pro E/T runner up.
2001, 2002, & 2003 NMRA Pro E/T Champion !
2004 #3, 2005, & 2006 NMRA Pro E/T runner up.
2007 Pro St. Legal #6, NMRA Pro E/T Champion !
2008 Motorcycle Drag Race Assoc. SS Champion !
www.dragbike.com - www.MDRA4U.com
www.PMRcomponents.com www.NAARDEN.biz
Photos by www.HooliganUnderground.com
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wannabe
Pro
Posts: 1931
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posted March 18, 2003 06:22 PM
Cowboy, yeah, I've been thinking about going up another tooth in the rear. As it is now, I'm still getting my foot in there with a whole bunch of time to spare before I have to shift to 2nd. I was also thinking about putting the stock springs back in, but I'd prefer to slip my tire rather than my clutch. It's nice to hear that I have a couple more psi to play with.
Red, thanks for the clutch slipping advice, but I can't seem to get any decent reaction times without totally side-stepping the clutch. For some reason, my left hand is really slow if I have to slip the clutch. So, I'm just going to work on my set-up to get around that. It's nice to hear that I'm at least on the right track.
I'm gonna try things 1 psi at a time up to 14psi then, if I need to, start lowering my wheelie bars half a turn at a time until I get it close to OK. I know the track conditions will be different every day, but if I get a good starting point, the race-day tweaking will be minor from there.
Ooh, I can't wait for the race in Sacramento this weekend. This will be the first race since I've started where I feel like I actually have a chance to win.
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"There are only three sports: bullfighting, motor racing, and mountaineering; the rest are just games." - Ernest Hemingway
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DR JOE
Expert Class
Posts: 352
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posted March 19, 2003 10:07 AM
Hey Wannabe
Quick lesson;
If you go down on the front spocket 1 tooth is = to 3 up in the back
so only going up 1 in the back is a waste of time and money.( my 2 cents ) If you want to see if going bigger in the back is what you need, put a 16 on the front and see what that does. Then you can go back to the 17 ft and a 51 out back.
You have to remember that you went from a tire contact patch thats about the size of your fist to the size of your hand and fingers spread out.
DR JOE
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kcadby
Pro
Posts: 1733
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posted March 19, 2003 11:37 AM
The M/T slick is a LOT "taller" than the street tire...put a 16 tooth on front to try it (as per DrJoe)...then decide what rear cog you you need to go through the traps at the top of 5th gear...
I agree with Dean (he's a smart man) if you are serious about leaving the bars/slick on the bike...I'd get the lock-up and use soft springs to start out 
There is nothing wrong with going even higher than 14psi if you need to...the tire will just wear out in the center first and won't last as long as it would if you had the "right combination" and "normal pressure"...
Lowering the bars will help also...
Let us know how it turns out...
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DR JOE
Expert Class
Posts: 352
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posted March 20, 2003 09:37 AM
One more thing there Wannabe,
Do one thing at a time, don't make 2 or more changes. This way you know what worked and what didn't. I know its more time consuming but its easier to figure out one thing at a time.
I see guys at the track do this all the time. They make 2 or 3 changes then they spend all day chasing grimlins... My 2 cents....
DR JOE
P.S. Is there anyone out there thats running a wheelie bar and slick? And what gearing are you running??? With what motor combo??
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RedBull
Expert Class
Posts: 406
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posted March 21, 2003 07:43 PM
quote:
Sorry, Dean. I forgot.
I'm running 16/48 on the stock wheelbase with wheelie bars. I don't have a two-step yet, so I'm just dumpinig the clutch off the rev-limiter. I'm not running a lock-up. I'm using the Muzzy's clutch pack and billet basket. Right now I have the wheelie bars set at 2" off the ground with my fat butt on the bike.
It already has a 16 in the front...
Remember air will make you tire taller...
You are on the right track, just continue with the seat time,
your bike can already run the Super Gas numbers
So now let's just have some fun racing...
Red, *<(:{)-
____________
1998 Prostar West Super Gas top ten.
1999 Prostar West Super Gas Champion !
2000 NMRA / Prostar Pro E/T runner up.
2001, 2002, & 2003 NMRA Pro E/T Champion !
2004 #3, 2005, & 2006 NMRA Pro E/T runner up.
2007 Pro St. Legal #6, NMRA Pro E/T Champion !
2008 Motorcycle Drag Race Assoc. SS Champion !
www.dragbike.com - www.MDRA4U.com
www.PMRcomponents.com www.NAARDEN.biz
Photos by www.HooliganUnderground.com
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wannabe
Pro
Posts: 1931
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posted March 22, 2003 06:52 PM
quote:
You are on the right track, just continue with the seat time,
your bike can already run the Super Gas numbers
So now let's just have some fun racing...
Red, *<(:{)-
I like that, Red. Is that your nice way of saying that I'm close enough and I should shut up and go race? If I'm not rained out tomorrow, we'll find out just how close I really am.
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wannabe
Pro
Posts: 1931
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posted March 23, 2003 08:23 AM
Well, it's tomorrow. No race. I got rained out. 
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