45 replies to this topic

[IRRA Retro Racing]

In the interest of closer competition and to better fit to the approved Stock Car bodies, the BoD has made a minor change to the specification of the Stock Car chassis.

The Stock Car chassis wheelbase is now specified as 4.50 inches (nominal), rather than the previous "4.50 inches minimum."

 

(posted for the IRRA^® BoD by Greg Wells)

[Rotorranch]

Now I have to double-check all my brand new cars!       

 

Rotor

[slotcarone]

Can you please clarify the difference here?

[Cheater]

The spec was formerly a Stock Car chassis wheelbase had to be "4.50 inches minimum."

 

Under that restriction, a Stock Car chassis with a wheelbase 4.75 inches would be legal. Under the new spec, it would not be.

[DavidR]

So basically 4.50" means 4.50". Is there no margin of error? Minimum allowed length?

[Cheater]

The stated spec is a 'nominal" 4.5 inches.

 

As with many dimensions in the IRRA rules, no plus/minus tolerance is specified. How short or long is 'too short" or "too long" is at the discretion of the tech inspector.

[Jay Guard]

This "nominal" thing is a really bad plan! Given a plus or minus tolerance makes the tech inspectors (and builders) job a lot easier.

[MSwiss]

On some things, the tech director has to make executive decisions.

An example is guide lead. How can you get an accurate measurement on an assembled car?

So how do put a plus minus on something you can't accurately measure?

In the case of guide lead, you can't even get a super accurate measurement, if you take the car apart.

Wheelbase is a bit easier, but depending on how the front axle is installed in the chassis, you might have to make a judgment call on it.

[Phil Smith]

I 100% agree with Jay.

 

If I'm teching wheelbase will have to be +/- 0.002". If I'm in a bad mood +/- 0.0005".

[MSwiss]

If you put a + or -, some racers will then build to the side of the tolerance they perceive gives them a performance advantage and your fictious scenario of a tech inspector in a bad mood could still come in play, and with a dimension that is difficult to measure, and could be impossible.

Regardless, this is a silly argument.

At the upcoming Sano 14, the IRRA^® will be celebrating its 13th anniversary and I've never heard of a car being bounced in tech over a wheelbase issue.

[tonyp]

A few thousands either way and the tech guy will have no issues.

The problem is building an 1/8" longer car to fit a 4.5” body. Because of the funky wheel wells on some Stock Cars, saying wheels must be centered in wheel arches doesn’t really work.

4.5" makes it easy. Time for a Chicago land stock car tech tool. LOL.

[Eddie Fleming]

Some of the bodies just cover 4.5" and keep the wheels in the opening. 

[DavidR]

Bodies that don't put wheels in proper position should be removed from approved list. Let bod makers adjust their molds then resubmit for approval.

[John Streisguth]

My question is, who actually built chassis longer to fit the bodies? Seems more than allowances were made on the wheelwell positioning. 

 

IMO, it would be more productive to write a rule to address that.  

[tonyp]

Don’t want to give his name. He has fixed them and will be ready for the Palooza.

He was building 4-5/8" wheelbase chassis and running with Charger bodies. The rear wheels were way out of place.

[Phil Smith]

Did that 4-5/8" wheelbase car have an advantage, or was it an aesthetics issue?

[tonyp]

Both.

[Phil Smith]

That's interesting. I've only had one 4.5" car ever, a flexi years ago. I never could get it to work anywhere near as good as a 4" flexi.

 

So my assumption has always been that anything much longer than 4" wheelbase was detrimental to performance. So going longer than 4.5" would never dawn on me.

[tonyp]

The Stock Cars are a different beast. .050" front to rear clearance and a 3 inch width. Plus a ton of body up high.

[Upfront slot cars]

This racer and myself discussed this for some oval racing a while ago. Either way, that trick is over with for now. That's what happens when your stuff starts running up front. People start looking closer trying to find out what's different about the chassis.

 

Besides, the guys that really know what they are looking at, including that tech inspector that's in a bad mood, can eyeball that wheelbase.

[Cheater]

It's very prototypical. The never-ending struggle between the racers and the rulesmakers.

[blkdout76]

So I'm guessing going forward, ALL stock car bodies of every racer will need to have the body off so the tech director can start teching this and not juat who they feel like teching?

[MSwiss]

Why would the tech director need the body off?

They would just have to put calipers or a steel rule along side the body, front axle center to rear axle center?

Whatever they would do, wouldn't it be the same thing to check to make sure the wheelbase isn't under 4.5"?

[CDavis7]

What egregious violation of the pre-existing rules could have occurred under the COVID lock down to necessitate this rule change? The min wheel base was fine for years. As a chassis builder, do I now have to re-evaluate all of my prior builds? For what purpose?

And few people can accurately measure the center line from the front axle to the rear.

What a waste of energy and time.

[CDavis7]

While we're at it, let's decide on a min and max weight with a tolerance of zero.