Petition for solid axle handicap in 2008

[fast_frank_d]

In the 2007 TT rules we have various hp/wt adjustments for "handicapped" or "gifted" cars. Generally the categories are fundamental advantages or disadvantages in the car’s design that separate it from a "typical sports car". Some examples are the –0.5 for AWD cars and +0.4 for a wagon. I am proposing a similar adjustment for solid axle cars due to their inability to adjust rear toe or camber and sizably increased unsprung weight. Also, the differential is not positively located, pretty much requiring a panhard bar or equivalent to prevent snap overseer. (I’m assuming that super exotic cambered live axle housings are not within the spirit of the “free camberâ€

Edited August 16, 2007 by Guest

[heavychevy]

I dont have a solid axle but I'll sign a petition for that as it is a big disadvantage.

[fast_frank_d]

That's one aye.

 

Any other votes?

 

FD

[Pat L.]

What about the advantages of running a solid rear axle? The ability to adjust roll center easily or the fact that you can push the chassis a mile ahead of an indipendent rear end, allowing for quicker transitions to power. Unless we're racing in the rain in '08, I'd vote for no change.

[fast_frank_d]

What about the advantages of running a solid rear axle? The ability to adjust roll center easily or the fact that you can push the chassis a mile ahead of an indipendent rear end, allowing for quicker transitions to power. Unless we're racing in the rain in '08, I'd vote for no change.

 

Those types of changes are already assessed points under the current rules (either via "adjust suspension mount points", or "add/modify torque arm" and similar line items).

 

FD

[Greg G.]

I have not seen any evidence that we need to handicap the solid rear axle cars so far. I guess that the AI race class would be the best example. My understanding is that there is a real debate as to which setup is better.

[fast_frank_d]

I have not seen any evidence that we need to handicap the solid rear axle cars so far. I guess that the AI race class would be the best example. My understanding is that there is a real debate as to which setup is better.

 

Greg,

 

It's safe to say that you know the rules better than I do, but I think your example is a Red Delicious apples vs. Granny Smith comparison. I think the AI guys can put on torque arms and cambered axle housings within their rule set. TT guys have to soak up points to do that.

 

If this is true, then the inherent solid axle disadvantage may still exist under the Time Trial rule set.

 

Frank D.

[D Algozine]

I'm not a TT driver, but if I understand Franks point, then I would have to agree. My understanding is a stock solid axle vs a stock IRS car. I would have to give a significant advantage to the IRS car. I also, assume this doesn't exclusively have to do with Mustangs, as there are many high performance street cars with very capable IRS's.

[D Algozine]

I have not seen any evidence that we need to handicap the solid rear axle cars so far. I guess that the AI race class would be the best example. My understanding is that there is a real debate as to which setup is better.

 

I think the debate in AI is weather a fulled modified (within the rules) solid axle is better or worse than a fully modified (within the rules) IRS.

That doesn't sound like that is the question in this case. My understanding of Franks question is a stock solid axle vs stock IRS car. I would give the nod to the IRS car. Weather it is a Mustang or real sports car with an IRS.

[Greg G.]

Ok, then we need to back up a bit. Frank's original question has to do with the formula we use for calculating "adjusted weight/power ratio" for our upper level classes (TTS, TTU, and TTR). In those classes, there are no modification points like in TTA-TTF. Those cars are almost unlimited in the types of suspension mods that they can do. So, I think that we are talking about fully developed IRS vs. solid axle.

 

Now, if we are talking about the cars in the lower classes that need to take points, then items such as the lovely solid axle OEM suspensions on old Mustangs get taken into account in the base classing of the individual car model. If you look at the base classing of old Mustangs, and compare their specs (wt., hp, wt/hp, etc) with similar newer cars with IRS, I think you will find that they start off in a lower base class already.

[Pat L.]

Guys, some of the fastest ST2 cars have been stick axle AI cars on Hoosiers. Vageli Karas put a whoopin' to the ST2 field in NorCal earlier this year that those guys are still feeling. Maybe those running solid rear axles that feel they are out-gunned just need to talk to some fellow competitors that are making it work.

[John Graber]

Pat,

Three garages for the Championships? What's going on there buddy?

[fuzznutz]

+1 on the voting from me....it requires so many extra points in the lower classes to just make the car predictable with the solid rear axle. i feel there should be a slight helping out here. +4 panahard and +4 for the torque arm addition, its seems a bit unfair to loose 8 points just to make the car drivable and high speeds. just my .02

[Pat L.]

Pat,

Three garages for the Championships? What's going on there buddy?

 

Us Best-Coasters travel in packs

 

Looking forward to seeing my Ohio/Indiana compadres!

[John Graber]

What class is that S4 running in?

 

Look for ALL the Mid Ohio TT records to fall this weekend.

[Pat L.]

Probably ST2 since I've got a tired motor in the car. I'm really anxious to see some of the TT action - should be even better than last year!

[fast_frank_d]

Ok, then we need to back up a bit. Frank's original question has to do with the formula we use for calculating "adjusted weight/power ratio" for our upper level classes (TTS, TTU, and TTR). In those classes, there are no modification points like in TTA-TTF. Those cars are almost unlimited in the types of suspension mods that they can do. So, I think that we are talking about fully developed IRS vs. solid axle.

 

Agreed... my initial petition for +0.4 based on stock components was flawed. I have edited my petition to be more appropriate for TTF-TTA.

 

Now, if we are talking about the cars in the lower classes that need to take points, then items such as the lovely solid axle OEM suspensions on old Mustangs get taken into account in the base classing of the individual car model. If you look at the base classing of old Mustangs, and compare their specs (wt., hp, wt/hp, etc) with similar newer cars with IRS, I think you will find that they start off in a lower base class already.

 

Maybe... I think I know the answer to this, but is this factored in when being base classed on the engine swap rule?

 

Here's 36 TTE based cars. I probably should have picked another class since there aren't many solid axle cars in this class, but oh well. One table is sorted by hp/wt, the other is sorted by adjusted hp/wt.

 

Frank D.

 

[kbrew8991]

while we're on this subject I think the FWD credit is a bit on the large side,

 

and I think a solid axle credit somewhere in the 0.20-0.40 range would be adequate

[Keith]

FWIW, you can safely get around -0.5 deg camber and some toe in on a live axle car without risk of tearing up the bearings (that is according to Herb Adams and I believed it and followed his statement with success). And since (at least) the GM shop manual's spec for rear camber on their f-bodies can be as high as -1.5deg, you should not be "docked" for being within manufacturer's tolerance.

 

...you don't need as much rear camber in a live axle car as an IRS car because the rear doesn't compress in the same way...

[fast_frank_d]

FWIW, you can safely get around -0.5 deg camber and some toe in on a live axle car without risk of tearing up the bearings (that is according to Herb Adams and I believed it and followed his statement with success). And since (at least) the GM shop manual's spec for rear camber on their f-bodies can be as high as -1.5deg, you should not be "docked" for being within manufacturer's tolerance.

 

...you don't need as much rear camber in a live axle car as an IRS car because the rear doesn't compress in the same way...

 

Thanks Keith, this is great info for dedicated racecars.

 

However, since this involves permanently bending the axle housing, I don't think many TT drivers are going to be willing to do that to their dual-purpose cars (which is most of us). Because of that, I feel the free camber allowance is only really “freeâ€

[kbrew8991]

F-Bodies don't have that issue... you're just in the wrong stick axle car my friend

 

- Ken

Mustang Owner as well

[fast_frank_d]

I'm beginning to think so....

[Keith]

However, since this involves permanently bending the axle housing, I don't think many TT drivers are going to be willing to do that to their dual-purpose cars (which is most of us).

 

Good point. When I jumped into the thread, I was think about my experience running PTC this year since TT/PT use the same rules.

 

The suspension bind-up that virtually requires the +4 panhard bar is slowly becoming my biggest beef.

.

 

Axle hop under braking is a constant terror in the f-body. Even with all the goodies under there. Trust me. I learned to adjust my rate of braking but still forget sometimes.

 

I have posted a step by step way to bend a rear axle on another forum including the math and photos if anyone is interested.

[fast_frank_d]

I have not seen any evidence that we need to handicap the solid rear axle cars so far. I guess that the AI race class would be the best example. My understanding is that there is a real debate as to which setup is better.

 

Since there were a couple people that mentioned American Iron as an example of equitable classing, I decided to take a closer look. According to my estimation, AI cars would be base classed at TTB with a wt/hp ratio of 9.5. I won’t go through the math, but AI prepped cars would be final classed deep into TTA and the more modified (but still AI legal) cars would run TTS.

 

No insult to the Midwest AI drivers, but the best AI cars have a real hard time beating the lap times of the best TTA cars (qualifying included). FYI, TTA winners are Corvettes and AWD cars (pretty much nationwide). I’d even bet $1 that the AI car that has occasionally edged out the TTA lap times would be TTS classed (or have an IRS). Not to mention the fact that these are fully dedicated, no compromise race cars.

 

Does this go back to my question about engine swap base classing for solid axle cars?

 

 

Frank D.

Edited August 23, 2007 by Guest

[QUASAR]

What about a handicap for heavier than stock axles? I run a Dana 60 axle in my car for strength in drag racing on a sticky tire. I have added 90-100lbs of UNSPRUNG weight to it when guys are doing everything to save a couple lbs under there. Its can also be a nightmare for axle tramp (wheel hop) under braking.

 

I only bring this up because there might be other vehicles with upgraded rear axles for strength out there that put themselves into a severe handling disadvantage in order to have a dual purpose vehicle. Food for thought...