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Author Topic: Tire Pressure recommendations  (Read 12325 times)
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joea
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« Reply #15 on: May 22, 2015, 09:37:52 PM »

Rebek...""I called Mickey Thompson before posting and they said: "Our tires are not approved for landspeed racing." (and) "The recommended pressure is whatever it says on the sidewall."  Manufacturers aren't much help when we exceed the design criteria of their equipment.  That's when we either need each other, or just to buck-up and go for it.""

there has been much SAGE advice given, yet you seem to want direct answers/direction about very
serious issues....that cant be blanket answered, TOO MANY VARIABLES

front runners should NOT be grouped together with respect to how they are utilized....

they ARE NOT apples to apples....!!!!

goodyear for example has standard front runners built and designed for one set of variables,
and other "front runners" made from same mold and built very differently, they both say
front runner on sidewall, but other designations reveal much more like built for sustained high
speeds, with much different carcass and bead structure and inflation specs 


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RebekahsZ
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« Reply #16 on: May 22, 2015, 10:26:07 PM »

There you guys go off on tangents again...
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Peter Jack
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« Reply #17 on: May 22, 2015, 11:55:26 PM »

Joe just gave you some very good advise which you seem to choose to ignore or even berate. Go into the Goodyear racing catalog and look at their landracing tires. They come from the same moulds as frontrunners but are a totally different tire.

I was on your side up until now. Smarten up.

Pete
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Milwaukee Midget
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« Reply #18 on: May 22, 2015, 11:59:09 PM »

There you guys go off on tangents again...

Contrary to the direction we travel, LSR is NOT linear.

One more variable - and I don't know the answer, but it may germane.  Are you running tubes?
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joea
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« Reply #19 on: May 23, 2015, 10:40:49 AM »

Rebek....your post

""That's two guys who are running front runners of some kind or another (even dry-rotted ones) to 65psi, so I'm gonna try increasing to at least 50psi.""

compelled me to try to communicate my previous information, ie that there can be vast differences
in front runners, not apples to apples etc
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Stainless1
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« Reply #20 on: May 23, 2015, 12:40:04 PM »

OK, just tell us what you want someone to tell you...
Do guys run tires above sidewall pressure number...?  sure all the time
Do you want us to tell you that your problem is tire pressure and not bump steer and you should try lots more pressure before you look into bump steer.., probably aint going to happen... I can tell you that a little bump steer twitch can look insignificant until you transition from power to parachute and end up 1/4 mile right of the course... luckily that year, that was the correct way to go if you had a problem  shocked
When you ask, try to listen, even if it is not what you want to hear
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RebekahsZ
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« Reply #21 on: May 26, 2015, 06:14:06 AM »

Thanks guys, I am listening, and I really do appreciate your advice. I will take a look at the Goodyear catalog. I'm not running tubes, but I'm open to it, especially with these two piece wheels. I have searched for small, skinny tubes before and couldn't find a vendor, any suggestions?
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Peter Jack
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« Reply #22 on: May 26, 2015, 06:54:10 AM »

Scroll down to page 4 on this link. http://www.racegoodyear.com/tires/pdf/Goodyear_Drag_Catalog_2015.pdf

This should give you the information you want other than they don't offer a maximum tire pressure, only a minimum. These tires are a different construction than the drag tire so the recommendations are for lsr tires only.

Pete
« Last Edit: May 26, 2015, 06:59:23 AM by Peter Jack » Logged
RebekahsZ
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« Reply #23 on: May 26, 2015, 01:18:42 PM »

I wonder why they only list a minimum pressure....thanks so much for the link.
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RebekahsZ
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« Reply #24 on: May 27, 2015, 01:01:47 AM »

That chart is super informative, thanks so much!  The minimums are all either 50 psi or 70 psi. Also interesting that the narrow tires are $600 each and the largest tire is $260. I'm sure you can't judge apples to oranges, but I will look up the weight on the MT front runners and see how it compares to the Goodyear Eagle Landspeed tire in weight.
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Bob Drury
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« Reply #25 on: May 27, 2015, 11:57:10 AM »

  One more thing to think about is tire circumference.  Before you make a pass, lay your fronts and rears in the Sun for say 15 minutes minimum.
  Then check the circumference at the psi you wish to run.  If they are more than 1" in circumference apart (I am not a tire engineer) I would advise you to add additional air in the smaller tire to bring it up to as close as you can to the mate tire or better yet, buy another pair of tires.  
  A word of warning to those trying to replace a single tire.  It is not uncommon for variations in "listed" tire size due to multiple molds, and perhaps other production factors.  I know that M/T matches their tires in pairs (I believe aired up) before shipping.
                                                                                            One Run Bob  Dead Horse
« Last Edit: May 27, 2015, 11:58:59 AM by Bob Drury » Logged

Bob Drury
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« Reply #26 on: June 04, 2015, 04:57:03 PM »

Also be wary - not trying to change subjects again but some front runners are bias ply while others are radials and that dramatically changes inflation pressures. 
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« Reply #27 on: June 09, 2015, 05:15:32 AM »

Just back from June ECTA meet with feedback.  Ran with 50psi cold in MT front runners in front and 40 cold in MT 275/60/15 Drag Radial Pros in back.  Did not check air pressures on Saturday when it was cool, but on Sunday when it was hot, the fronts had risen to 60 and the rears to 45 coming off the track after a run.  Ran an airdam that increased my top speed from 167 to 174.  But, the airdam increased downforce and changed my dynamic alignment settings.  Also found that the suspension is very active (too active).  With the front end down from the airdam and splitter, the added nose down of braking made the car a little scary at the transition point and i found myself using the second turn-out most of the weekend, just so I could brake easier.  Clearly I had bumpsteer from the toe-out induced by the nose dropping from downforce, further aggrevated by braking (I have road racing brakes).  Spend Saturday afternoon cutting off the splitter and Sunday experimenting with different toe settings.  Increasing toe helped A LOT in braking, but made the car more twitchy during the speed section of each run.  On the last two runs, I dropped my air pressure down to 35 all the way around and ripped into a big headwind and ran 167.  Car felt better, although my video shows more driver input at speed than my mind remembered.  I think perhaps the softer tires allowed the tires to deflect instead of the suspension (maybe?).  Lots to learn and lots of TnT to do next year.  Will probably wait till June meet due to 2 daughters graduating next year.  I have a couple of autocross/road course events to do this summer, so the toe is getting pulled back out.  Then this winter, I'm going to zero camber, as much caster as I can get into it and DOUBLING the spring rate.  Gonna make a variety of aero devices to try out in June.  Will aim to stay in the 170mph range next year, but get the car handling before doing anything that would increase speed. Will plan to stay at the 35psi tire pressure as a starting point for next year.  When surveying drivers at the meet, tire pressures were all over the map.  Thanks everybody for all the encouragement and advice.  Even though I started this thread with the specific intended goal of a tire pressure survey, it was super educational and I read every post and I really appreciate everybody's advice.
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joea
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« Reply #28 on: June 09, 2015, 06:42:37 AM »

Major kudos to you for you results and efforts !!
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RidgeRunner
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« Reply #29 on: June 09, 2015, 08:12:34 AM »

     A very analytical and logical approach.  Thanks for sharing, you have me thinking deeper about a couple things.

              Ed
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