Tech Services

Recent Updates & Announcements

Turbocharger Bolt Rule Clarification

If your ½” bolts are as close to the turbo housings as possible, then you are good. You don’t have to add, but if they are more than 2” away from the turbo housing, then you need to install two


Attention Super Farm Competitors 

There will be a stainless exhaust wheel cage available for all competitors at Bowling Green, OH starting Thursday from the welder which would replace the bolts. In order to run Bowling Green, OH and the rest of the 2023 season,


Tech Questions & Answers


Mr. Richwine, I bought a new Trick Titanium belhousing for my Mod FWD. I received it in January 2022. It has a current SFI sticker on it and all legal, but, it only has 13 bolts holes around the flange. It also has the 4 big quadrant holes. Do those holes count to meet the 15 bolts requirement? If not, do I need to drill two holes in it to be legal?  I see the rulebook states either 15 or 18 bolts around it to be SFI legal. Please tell me what to do.


 No, don’t drill any holes in it. If they sold it to you as a SFI certified belhousing with only 13 holes it’s legal. If you modify it by drilling extra holes in it won’t be re-certified when you have to send it to Trick Titanium for re-certification because you have modified it.

 Since the rulebook was printed this has come up a couple of times. The bottom line is NTPA wants you to have a “current SFI certified” belhousing properly installed on your vehicle starting January 1, 2023. If Trick Titanium sold you the can as “SFI certified” then NTPA will not tell you to modify it.


Richwine, what’s this I hear about the Scheid injection pump that I’ve been running in the Super Farm class for the past 5 years may not be legal?

How the hell can that be true?


The question was raised at Louisville as to the legality of a “P” pump that wasn’t a P7100 housing in the Super Farm class.

The 2022 NTPA rulebook pg 62 under SF rules states that the pump must be a “P” pump but, doesn’t specify that it has to be “7100 series”.

After research, review and consideration the NTPA exe board has decided that this issue should be reviewed in September of 2022 by the SF division and better clarified at that meeting for the 2023 rulebook.

So, the Scheid pump you’ve been running can continue to run for 2022.


Richwine, I was told at Shipshawanna that the rules had changed and I had to have 1/2 “ bolts instead of 3/8” bolts as close to the exhaust wheel as possible, Is that true?


Yes, the rule changed two years ago. You have to have 2  – 1/2 “ bolts in the horizontal part of the pipe as close to the exhaust wheel as possible.  Also, the turbos that have a cross in the turbo exhaust housing from the manufacture doesn’t count. The exhaust pipe still has to have the cross bolts (1/2”) in the horizontal part of the pipe.


Mr. Richwine

Is BioDiesel legal for NTPA competition in 2022?  I see where you raised the dielectric reading to 150 but I thought that would eliminate B100. Is this not true? There seems to be a debate if Bio is legal or not.


We did raise the dielectric limit to 150 for diesel fuel, but, the rules for BioDiesel did not change. The B100 rules are exactly the same as they have been in the past. So, yes biodiesel is still legal.


Mr. Richwine, my partner and I are coming to Ocala and run the LLSS class. What all do I have to do to pass inspection? We run about all the different groups here in New England, but, we’ve never ran at a NTPA event.


The NTPA rules for all classes will apply to all of the classes that are scheduled at Ocala. This includes all safety rules like inner side shields, cross bolts in the turbo exhaust pipes, rollcage and attachment, firesuit and equipment, etc. Better get there early and get checked ASAP.


Larry I’m getting close to ready to loading and headed Fl.  I’ve been hearing people needing a neutral light on back of tractor ???  Is this a new rule?? A neutral light and neutral safety switch??? Not sure how power it with safety switch being ground. If it needed.  Sending memberships in next week  so I don’t have new rule book thanks


NTPA requires a 2 inch white light on the rear of the vehicle to indicate “reverse” as well as a “neutral” switch to keep it from starting in gear.
The other group requires amber light for neutral.


Mr. Richwine, I was told I can’t use hex socket head bolts to attach my belhousing to my engine / block plate. Is this true?  Some of the bolt holes are so close to the bell that a normal hex head bolt can’t be used. What the heck should I do?


I understand that this is a problem on some belhousings, so, in this case, you will be allowed to use a hardened hex socket head bolt as long as all the other fasteners are grade 8 bolts and / or studs.


Hey Richwine, what’s this BS that I’ve gota get my steel Lakewood belhousing inspected by Lakewood and have a sticker on it? You guys stamped it so I didn’t have to worry about the sticker or if it was current.


Yes, Starting Jan 1, 2023 all SFI belhousings regardless of material i.e. steel, titanium or aluminum must display a current SFI sticker with a expiration date affixed by the manufacture. The NTPA steel stamp will no longer be acceptable as a replacement for SFI decal after Jan 1, 2023.


Hey Richwine, Did the Mini Rod trans mounting rules change after Bowling Green?


No, nothing changed yet. The number of bolts may change for 2022 but, we will finish the 2021 season same as in the past.


Mr. Richwine,

Will there be pulloffs at BG this year? I’ve noticed that you havent had pulloffs at any events this season.


Yes, there will be pulloffs if they go past 350 feet. The NTPA rulebook allows for a max distance of 350′ I realize we’ve exceeded that distance at several events but there’s not really enough “runoff” room past 350 here at Bowling Green to allow it. The pullers will be red flagged if they go past 350 and will be required to come back for a pulloff. 


Can I run if I don’t have a turbo blanket but have it ordered?
Also, can I build a steel shield around my compressor housing instead of buying a blanket?


No, you are required to have a Kevlar blanket around you “high pressure” or last turbocharger’s compressor housing in a multi turbo setup. 

Also No, a steel cover instead of a blanket will not contain the fragments as well as a properly installed blanket.

If you show up at a NTPA event without a blanket you will have to borrow one or just not pull.

Note: A turbo blanket is only required in classes that allow a turbo inlet larger than 3 inches.


Mr. Richwine, I’m new to NTPA, how do you guys measure the turbo? I say that the wheel where it sticks thru the housing should be 3” and everybody tells me I wrong it’s the housing.


Sorry, they’re correct and you’re wrong. When NTPA first started measuring the Super Farm class and actually made them tear the turbo down to be measured and sealed  we set the president of measuring the bore of the housing at the face of the wheel like the rules state.

We measure several different classes now and they’re all measured the same way. We use a slug or a  “Go /No Go” gauge. Sounds like if measured at a NTPA event that your turbo will not pass.


Mr. Richwine,

Are the LLSS rules set in stone? What about the WTPA tractors that don’t fit the rules you published? Are you gona allow front suspension?


The rules that are posted are final and in place for 2021. I suggest that any changes you or any group wish to make be subbmitted for the September meetings of 2021. If they are adopted, they would be in effect for the 2022 season.


Hey Mr. Larry,

Did the NTPA raise their diesel fuel spec like the other guys did?


No, its still at a max number of 100 for 2021.


Mr. Richwine, My engine builder wants me to run 3-4 cables around my engine after the Light Pro explosion at a non sanctioned event this summer, can I do that?


No, only one cable is required or allowed around in line engines in NTPA competition. I understand your engine builders concern but, years ago when the cables were first required we required two cables. We found that only contained the explosion enough to make smaller pieces fly. The cables job is to flip the assembly away from the driver. Everyone always says “but the cable broke” and thats true, but, before it breakes or pulls out of it clamps it does the job as intended.

If you come to a NTPA event with more than one cable on your engine you will be told to take all the extra ones off before you’re allowed to run unless you have a Moline or case, then they require a cable for each head.


Richwine are you doing “Super Tech” at Ft Recovery?


Yes on Saturday from 11am – 2PM on Mini Rods and Unlimited only


Hey Richwine, I hear that the Super Farm pullers had trouble in Rockwell passing the new water test you have. Is that true? what the heck are you doing?


NTPA does have a new test but, it’s no different that PPL’s, so if your water will pass there, it will pass here.



Is the MSD 600 CDI unit legal on my mini rod for NTPA competition?


The Msd 600 cdi by definition of the timing control rule is a legal component when used as only an energy provider for individual coil packs. It only becomes illegal if an external controller is used in conjunction with the 600 cdi in order to adjust ignition timing during a competition run.


Mr. Richwine,

Please explain how a “Rain Out” works. When can the promoter call it off where I don’t have to show up to get rain points etc. I’ve heard a bunch of different versions of what should or has happened.


Page 88 of the 2019 NTPA rulebook under letter E Inclement Weather states:

#7. If a session is cancelled more than 24 hours prior to start time
at GN/SN or 8 hours at RN/PN/state level, no points will be given
for that session.
#8. If a session is cancelled prior to start time, competitors will
receive refund of paid entry fees, but no other compensation.

With that said, if the event isn’t canceled within the time period described in #7 then you do have to travel to the event with your pulling vehicle and check in so the entry personnel can record your entry in order to receive rain points. The entry trailer must remain open until scheduled start time of the event in order for you to “check in”.

As to “Why do I have to take my pulling vehicle with me?” page 81 under Event Procedures and Requirements #4 reads:

#4. Vehicle must be present on the ground in running order and
ready to compete before being allowed to enter.



When the rule says exhaust limit 4.5 inch and the wheel must proturde .125 inch into the bore, will the nut count? Its part of the wheel. Or if I have a couple of little fins in front of the regular wheel will they count? Answer:
No, the nut doesnt count. The rule says

  1. Turbo limited to 4.5 inch diameter exhaust to be measured at the face of the wheel.
  2. Exhaust wheel tips of wheel (each blade/fin, nut does not count) must protrude into the 4.5 inch bore by 0.125” minimum.
  3. All exhaust must exit the 4.5 inch bore.
    We are going to measure the turbo just like we have on the Super Farm class’s 3 inch bore since the days when we “sealed” the turbo with a lead seal.

If we question how deep it goes into the bore you will be required to disassemble your turbo so we can measure it.

I included a picture of how / where we will measure the wheel

turbo exhaust


Mr. Larry,
Can I run my 24.5 tires in the Hot Farm class? I dont want to buy 20.8’s but, my tractor fits the hot farm class all but tires.
If not, WHY not.


No, you can’t run the 24.5 tires in the Hot farm class. The reason is that the class needs to and does look different than all the other classes from the grandstand.
You will be surprised how good your tractor hooks up with 20.8 tires on it.


Can I run my tractor with an expired roll cage sticker?


Yes as long as the old sticker is still in place. The Techs know (because they have been told in tech school) that you can run until you find one of the roll cage inspectors.


Mr. Richwine,

What’s the deal with the new “V” hitch I’ve heard about for Mini rods? Are they legal? Are they gona be allowed in all classes? Asking for a friend.


No, they aren’t legal the rulebook states in general rules as well as some class rules that nothing can obstruct the chain or the hooking or unhooking of it. The “V” cut design not only would cause difficulty in hooking (if not straight with the sled) but would also make unhooking harder than it already is. Also, when the hook tries to go from side to side when the vehicle gets sideways it will affect the angle of the hook and change the draft of the chain.

The cross sectional thickness of the point of hook is also spelled out in the rulebook for all classes. This too can affect the hook and the draft of the chain.
Drawbar Design


Mr. Richwine,
Can anyone attend the tech school or do you have to be one of the “Click” to attend??


The school is open for anyone to set in on but, in order to take the test and become a NTPA licensed official you must be endorsed by either a NTPA member state or by the NTPA itself.


Mr. Richwine,

I hear that Hart has a new 3″ charger that measures a fuzz over 3 inches.It was allowed to run last weekend in NC at a non NTPA event. Will that be allowed to run at a UPOC event? If so what’s the limit?


I heard about the new turbo and have had a couple of calls already. I can assure you that NTPA won’t allow that and if they are found to be on a tractor at a NTPA event, they won’t be allowed to run or if they are found to have run after the fact the tractor will be DQ’d.As luck would have it, I will be at Pinetops and Benson and will make sure the SF chargers are checked.


Hey Richwine,
I’m new to NTPA and I can’t find the rollcage mounting spec anywhere in the rulebook. I have a D-21 and need to mount an AccuFeed cage to it. Where is it and what do I need to do?


The Rollcage spec is a SFI 47.1, that’s all that’s listed in the book. The mounting to a OEM chassis is as follows:

Mounting must use at least 3 axle housing bolts on each side as well as 1 bolt before and after the axle housing. There bolts must be in sheer (horizontal ) with a total of 2 9/16” bolt material. 
mounting cage


Mr. Richwine,
I am building a Mini Rod and have a question about the webbing between the upright tubes? Can they be lightened? If so, how much? I have included a photo of the chassis that is available and they look like they have been lightened a lot.


Yes the shear webbing that goes between the up tubes can be lightened by 40%.
The Spec says: shear web may have lightening holes but must retain 60% material and must have a minimum of 1 inch around the perimeter of the web on all four sides. This applies to both Mini Rods and Big Tractor rollcages.
After looking at the photo you are correct this will not pass the SFI / NTPA inspection and will have to be corrected before they are allowed to compete with NTPA.


Mr. Richwine,
I’m not a member of NTPA but, would like to run at the upcoming event. I need to get my cage inspected, is there a charge for that?


Here’s the program that’s been in place since 1999 when the cage was implemented.
All vehicles that compete at a NTPA event must have the rollcage inspected and display a NTPA/SFI certification sticker or the vehicle will not be allowed to hook.

  1. Upon passing inspection and paying the fee of $75.00 per cage to NTPA on vehicles that have a paid NTPA membership. The rollcage will have a certification sticker applied to it that denotes the inspection date, it will be valid for a period of five (5) years before being required to have their rollcage reinspected. Unless an accident occurs that involves the rollcage.
  2. A service fee of $100.00 will be added to a cage that is on a non NTPA member vehicle. This $100.00 fee will be applied to a regular membership (not per hook) if the vehicle joins NTPA within a 60 day period from the date of inspection.

Marvin Epperson
Director of Technical Services

(317) 852-0630

To order a NTPA rulebook, order online, call the NTPA office at 614-436-1761 or mail $6 plus $2 shipping and handling to WPI/NTPA, 6155-B Huntley Rd. Columbus, OH 43229.


The following people are certified as rollcage inspectors, please contact them to get your rollcage inspected. Rollcages are certified for 5 years.

Scott Doty (MI)734-755-3959
Dale Quamme (MN)952-500-0820
Jay Barrett (NC)​ 315-559-9568
Marvin Epperson (OH)​ ​317-852-0630
Tom Jackson (OH)330-465-6828
Dennis Long (OH)​ ​740-837-0582
Matt Steinmetz (OH)​ ​419-239-3820
Steve Zimmer (OH)* ​​740-525-0639
Mike Griffin (TN)931-629-2244

* Travels a​ ​lot so reach out to see if in your area.


It is the competitor’s responsibility to notify a certified inspector and arrange an inspection prior to the deadline indicated on the NTPA-issued rollcage certification decal. (Re-)certification inspections may be requested at the entry trailer or during standard on-site tech inspection.

For rollcage inspections at a site other than an NTPA event, contact NTPA Tech Services to make an appointment.

Please note: Inspection dates do not necessarily coincide with event dates. Check the Schedule page at for event dates and session start times.

Rollcage inspections have been completed for 2022.

All Updates & Announcements

Turbocharger Bolt Rule Clarification

If your ½” bolts are as close to the turbo housings as possible, then you are good. You don’t have to add, but if they are more than 2” away from the turbo housing, then you need to install two (2) new ½” grade 5 bolts as close as possible. Anything that is farther than 2” away can be removed from the exhaust pipe.

Attention Super Farm Competitors 

There will be a stainless exhaust wheel cage available for all competitors at Bowling Green, OH starting Thursday from the welder which would replace the bolts.

In order to run Bowling Green, OH and the rest of the 2023 season, this must be installed.

Attention Competitors: Effective Immediately 6/6/2023

  1. Effective immediately, the Limited Pro Stock will be allowed to enter the 5.0 Regional Pro stock class for this 2023 season. Providing they meet all competition rules and safety regulations.  Still no Light Pro Stock or Super Farm.
  2. Any class requiring an SFI  – 4.2 Blanket must have them installed correctly and will be held to the same criteria as the bellhousing in competition. If you have the proper blanket installed but it has and out of date tag,( outside of the 5 year window) you will be able to run but you must make the effort to either get them recertified or replaced and by January 1.2024 they must display an up to date certification on the SFI Tag.

Region III / WTPA Competitors: No Roll Cage Inspections at Ellsworth; Inspections Available After May 1 by Appointment

Any competitor that has a new vehicle for 2023, or needs to re-certify, must have their roll cage and chassis inspected by Dale Quamme.

There will not be a roll cage and chassis inspection in Ellsworth this year. Dale will be available to travel around Wisconsin after the weekend of April 28-29.

Please contact Dale (952.500.0820) to schedule an appointment to get this done before the season starts or if you have any questions.

Note: If the roll cage certification decal is punched 2017 or older, the certification is expired and requires recertification.

Effective Immediately 3/16/2023

1. GN Light Modified division weight limit is now 6200 lbs. for 2023 season.

2. Super Farm, Light Pro Stock, and Limited Pro Stock divisions cannot enter the new RN Heavy Pro Stock 5.0 class. Entering of stated vehicles in divisions other than RN Heavy Pro Stock 5.0 as permitted by 2023 NTPA Pulling rules is still allowed. 

3. The WPI Executive Board moved to limit Mini division at all levels to any current 18.4×16.1 – 6 ply tires already in competition from 2022 season (Pioneer, Cepek, Mayhill). No changes to construction or dimensions of these tires will be allowed for the 2023 season. Limiting Mini division to these tires will maintain current vehicle dimensions and weight limit while keeping competition at an already high level.

Correction to Rules for the 2023 Rulebook

Page 75 at top under both 1) and 2)

the letter d) rule should be deleted.

d) Rotors must be contained within a one-piece rotor case. 

Light Limited Super Stock subsections 1. Engine o) & p) & 2. Turbocharger Restrictions

o) Maximum of 470 cid. for single turbocharged diesel engines.

3.This engine combination can run a maximum of one (1) 3.4X4-inch smooth bore turbo OR (1) 3×4 turbo with maximum of .200-inch MAF enhancement ring, no forward facing MAF.

p) Maximum of 370 cid. for single turbocharged alcohol engines.

1. No intercoolers allowed.

2. This engine combination can run a maximum of one (1) 3X4 smooth bore turbocharger.

2. Turocharger Restrictions

a) All turbo compressor and exhaust wheels must protrude into the housing restricted opening no less than 1/8-inch.

b) Engines limited to a 3×4-inch turbo, the 3-inch compressor wheel must protrude into the housing 1/8-inch and compressor wheel must measure no larger than 3 inches at face of wheel.

c) Diesel engines limited to a 3.4X4-inch smooth bore turbo, the compressor wheel must protrude into the housing 1/8-inch and the compressor wheel must measure no larger than 3.400-inches at face of the wheel.

d) No superchargers allowed.

Attention Competitors with a Modified Mini

It has come to the attention of NTPA Technical Services that certain variations in construction of the SFI 47.3 rollcage do not meet standards set forth by SFI or do not meet NTPA roll cage mounting guidelines. The SFI 47.3 standard for vehicles that compete at 2,000 lbs., namely Modified Mini division, has been in place since 1998 and the specifications for construction and mounting of the rollcage have never changed.

Therefore, the WPI Board of Directors has determined the following corrective action is necessary.

  1.        All 47.3 rollcages must have a diagonal bar installed between the front and rear vertical tube on each side of the rollcage as specified. This tube may currently be installed in the horizontal position and will need to be removed and a new tube fitted diagonally in the correct location according to the SFI specifications.
  2.        NTPA rollcage mounting standards for both tube type or channel type chassis require a 1/4-inch x 3-inch steel web plate be properly welded at base of rollcage on each side between front and rear vertical tubes as well as across the rear of the rollcage. The flat, 1/4-inch x 3-inch steel plate needs to be installed between each vertical tube all the way around the rollcage, connecting all vertical tubes together.

Any SFI 47.3 rollcage that is in violation of the issues described will have until June 01, 2023 to complete the repairs in order to compete during the 2023 season. Once the roll cage has been updated to meet the requirements described, the rollcage will be re-certified by a NTPA Rollcage Inspector at no charge to owner and a new 5-year certification sticker will be installed.

NTPA Technical Services recommends that competitors contact their chassis / rollcage manufacturer for more details regarding any corrective action necessary. A copy of any SFI standard can be obtained by contacting SFI directly at 858-451-8868 or follow the following link to order,
A copy of NTPA Rollcage Mounting Standards can be obtained by contacting NTPA Technical Services.

Marvin Epperson
NTPA Director of Technical Services

You can reach out to your chassis builder if needed: Here are three which have agreed to help in expediting this process for you and have the SFI 47.3 Spec in their possession. 

TRB Machine | Zeeland, MI

GMS Manufacturing & Machine | Hamilton, OH

Modern Machine & Tool | Van Buren, IN

Examples of acceptable ways to fix the diagonal brace.


Examples of acceptable ways to fix the webbing.




Webbing must retain 65% material of the 1/4-inch X 3-inch flat bar when scalloping for weight; which means retaining 1-inch material at any edge.


WPI Executive Board of Directors: Statement on Aftermarket Super Stock and Pro Stock Engine Blocks

(Updated February 4, 2023: Bore Spacing Specifications)

The WPI Executive Board of Directors voted to clarify rules related to dimensions and configuration of aftermarket recast and billet engine blocks used in Super Stock and Pro Stock Divisions. Rules are specific to any legal block with a cylinder bore spacing of 5.875-inches or less at Grand National level only. The only change from rules printed in 2023 NTPA Pulling Rules is to allow altering of head bolt position based on engine block bore spacing.

All other divisions and competition levels where a recast or billet aftermarket block is allowed are not affected. Those divisions will continue to adhere to all stock OEM block and cylinder head specs including OEM head bolt position as found in 2023 NTPA Pulling Rules.

The following is a summary of rules currently found in 2023 NTPA Pulling Rules with the addition of allowance to alter original OEM head bolt position only.

  1. GN Super Stock and Pro Stock Engines (5.875-inches or less bore spacing)
    1. Specifications for block to be based on factory OEM specs of the block chosen to be replicated.
    2. To be considered a legal block:
      1. Must swing a stock OEM crankshaft and retain stock OEM bore spacing of make and model OEM block replicated.
      2. Overall height, width, and length of block must be same dimension as stock OEM block replaced.
        1. Super Stock block not to exceed 5/8-inch total increase to OEM deck height of block measured from centerline of crankshaft. An additional .130-inch head gasket is allowed not to exceed 540 maximum cid. No deck plate or additional block deck height allowed on Super Stock engines over 540 cid.
        2. Pro Stock block not to exceed 1-inch total increase to OEM deck height measured from centerline of crankshaft to cylinder head surface including any gaskets and/or spacers.
      3. Crankshaft location must be same as stock OEM block replicated.
      4. Alteration to stock OEM head bolt pattern allowed including quantity, size, and position of head bolts attaching cylinder head to block. This is the only exception to OEM gasket requirement. All other OEM dimensions, specs, and component position must be maintained as described in previous rules.
      5. Manufacturer must submit aftermarket block for approval by NTPA Technical Services before being allowed to compete.
    3. OEM Block Cylinder Bore Spacing
      1. The following specifications are the accepted cylinder block bore spacing dimensions accepted by WPI/NTPA when replicating a stock OEM block for use where legal in NTPA competition.
        1. Big Block John Deere 619
          • 6.000 inches
          • Cylinders 1 thru 6
        2. Small Block John Deere 466
          • 5.375 inches
          • Cylinders 1 thru 6
        3. IH DT466/530
          • 5.330 inches
          • Cylinders 1 thru 6
        4. Detroit 40 Series 466/530
          • 5.330 inches
          • Cylinders 1 thru 6
        5. Case 504
          • 5.563 inches
          • Cylinders 1 thru 6
        6. Ford / New Holland 401/456
          • 5.130 inches
          • Cylinders 1 thru 6
        7. Allis Chalmers 426
          • 5.188 inches
          • Cylinders 1-3 & 4-6
          • (Center Space – 5.563 inches)
        8. White/Oliver (Hercules 478)
          • 5.313 inches
          • Cylinders 1-3 & 4-6
          • (Center Space – 5.875 inches)

2023 NTPA Pulling Rules Tire Approval and Measuring

General Rules

Tire Approval

  1. – Any new tire and/or tire size(s) other than those currently approved for NTPA competition must be approved by NTPA Technical Services before being used in NTPA competition.
  2. Company name and/or brand along with tire size and ply rating required to be molded into sidewall of tire from manufacturer and must remain visible on any tire used in NTPA competition at all times.
  3. Any new tire or anytime an existing approved tire is sold to a different manufacturer or is rebranded with a different name, the tire must be submitted by manufacturer to NTPA Technical Services for approval directly from the mold before cutting.
  4. It is the manufacturers responsibility to submit any new or rebranded tire to NTPA Technical Services for approval before tire is cut or used in NTPA competition. Violation of this rule(s) is subject to any penalty determined appropriate by the WPI/NTPA Executive Boards.

Tire Measuring

  1. Tire to be measured using NTPA tools specifically designed for such purpose with tire mounted on specified rim width and inflation pressure adjusted to specifications set by tire size.
  2. Tread to be measured from outside to outside of tire or tread face with caliper extending outside and to bottom of any radius at outer corner of tire face or tread.
  3. Tire must measure less than maximum specifications for both circumference and width before being approved by NTPA Technical Services.

 Mitas 24.5 Tires – (unapproved tire exception to NTPA Pulling Rules)

  1. Mitas 24.5 tire required to be corrected by cutting or grinding tire to maximum width of 24.5 inches in order to be used in NTPA competition. Corrected tires will be allowed in GN Pro Stock competition only. This exception to NTPA rules is limited to 60 sets maximum of inventory currently in the US as of December 2022. All tires brought to the US by Mitas from this date forward are required to be approved and meet NTPA tire dimensions out of mold before cutting. Corrected tires meeting 24.5 inch width specification will be branded with date of inspection before being allowed to compete.

Tire 48 Lug Rule

Region National classes limited to 24.5 x 32 tire with a maximum of 48 lugs are:

– Super Farm

– Light Pro Stock

– Limited Pro Stock

– Heavy Pro Stock – 5.0 turbo

2023 NTPA Pulling Rules

Competition Rules

Heavy Pro Stock – 5.0 Spec Turbo

WPI/NTPA Executive Boards voted to adopt the Wimer 5.0 x 5.370 spec turbo as the only turbo allowed in RN Heavy Pro Stock competition beginning in 2023 season.

Supercharger Overdrive Measuring

If your class or division is governed by a certain percentage of overdrive; be advised it will be checked in 2023 and should be at or under the number set forth in the rule book.

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