Besides the obvious (nowhere does it say you CAN), what prevents competitors from cambering live axles in stock, SP, ST etc?

As an example, there's no stated camber measurement in the Ford service manual for my car. How could it be protested successfully, if a car had measureable negative rear camber?

Believe me, between being a guy who would never cheat and the implications (think bearing wear, for starters), I have no personal interest, but it is a topic which came up recently. In some classes, like ESP, it could be a really beneficial modification.

I jumped a solid axle RX2 so high and far once that it ended up with "rear camber" even though it is a 4 link rear end. 20 miles later, one of the axles snapped at the splines at the diff.

Oops!

FM

LOL, but not quite what I had in mind...[:D]

There are tons of race cars out there with cambered rear ends...all it takes is a fixture, some hydraulic force and a little heat....next thing you know, negative camber. I'm just curious how you would successfully protest, in a class that didn't specifically say it was allowed/disallowed and where the service manual doesn't have a spec for rear camber measurement.

Live axle race cars with camber?

The axle isn't going to flex, is it? 

You plan on machining the splines or diff. so the axles can come out at an angle?

Bend the axle and you have a wheel that goes from neg. camber to toe-in to pos. camber to toe-out every revolution.

So you just get some friction and wear at the diff/axle splines?

It was a long time ago but I saw an article in a car magazine on this and they round the splined part of the axle so it doesn't bind in the carrier. I'm guessing the axles have to be replaced often but in racing where every little thing counts, the cost is a small price to pay.

I've never run a car with this modification, so I'm no expert, but my understanding is that bearing wear is accelerated with the uneven side loading, particularly the axle bearing (less so carrier). Limiting total negative camber allows the axles, side gears etc to live. This isn't a mod you'd do to a daily driver.

Question remains, though...how could it be protested?

Isn't there a rear spec in the crash repair manuals? I can remember showing up to ESP at Nationals in 1992 or 3 and a lot of the cars had more negative camber in the rear then others.

Besides the rule issue, cambering a live axle is not a big deal. On a standard axle setup, .5 to .75 is generlly considered the most you can get away with without tearting up the diff. On full floating axles, you can go up to 2.5 degrees with no problem. They use a cambered snout, rounded splines and hardened drive plates and it works fine. The Sprint Cup cars are all highly cambered and they run 500+ miles under race conditions.

In my experience with the POS Ford 8.8, the axles flex enough with big tires that you would want to start with some negative static (assuming it was legal). On my full floating axle, I use 1 degree and it works well. You have to be careful of pinion angle with camber, as camber becomes toe when the axle rotates, and live axles are not tolerant of any toe out.

DaveW

Thinking this through, I'd have to imagine if a car were protested in a class that doesn't specifically allow the type of modification we're talking about, that the protest could be upheld if the live axle measured out equal l/r negative camber and toe in values that would be seen as performance improvers. That would be enough coincidence to make it impossible to argue "crash damage" or "manufacturing variance". Given that even a few tenths of negative camber is pretty easy to see from the back of the car, maybe this isn't something that needs to be spelled out in the rule book?

I dunno, it was just a conversation which came up in my local autocross group on a topic I hadn't thought about since starting Solo a few years ago.

It is outlined in the rulebook.

[quote]Except for modifications authorized below, Stock Category cars must be run as specified by the factory with only standard equipment as defined by these Rules.

This has been done for years. Many solid axle cars have a spec range, and people bend to the max.

As long as it is within spec, how do you determine intentional versus production tolerance?

DaveW

That's a question I have, too. Also, what about "accident damage"? What about cars where there is no spec in the service manual?

I'm not wrapped around the axle (pun intended) on this one, I'm just curious how it is dealt with by a PC. Like I said before, you measure out a stock class car and both sides are entirely consistent, say something like -.5 to .-6 with 1/16-1/8" toe in, I'm calling it a cheater and would expect a protest upheld, even if the crash spec allows up to -.5. There's no way that is anything besides an illegal modification.

I have no fricken clue where to find it, but there has to be a spec somewhere for every car. How do they determine whether to replace an axle in a crashed car?

Assuming you have a spec, and are over it, you are illegal whether it was intentional or not. Your opinion of someone being a cheater won't factor into it :):)

DaveW

To find an "example" - I pored-over the Mustang factory shop-manual(s) last night after reading this - couldn't find a spec anywhere. I thought the "gotcha" might be concealed in a runout/straightness spec on the axle, or perhaps even a go/no-go "special tool" - no dice.