Jacking rails for F-Street?

[Ugly John]

So I know since jacking rails aren't listed in the rules, they are not allowed for F-Street. Why is that? Do they really stiffen the chassis that much? Is there a significant performance advantage to using them? I hate using the pinch welds every time I have to change tires out, and a set of rails would let me change both tires on a side with just jacking once.

Sponsored

 

[HoosierDaddy]

So I know since jacking rails aren't listed in the rules, they are not allowed for F-Street. Why is that? Do they really stiffen the chassis that much? Is there a significant performance advantage to using them? I hate using the pinch welds every time I have to change tires out, and a set of rails would let me change both tires on a side with just jacking once.

How long does it take to bolt and unbolt them if they won't let you compete with them on?

 

[kz]

So I know since jacking rails aren't listed in the rules, they are not allowed for F-Street. Why is that? Do they really stiffen the chassis that much? Is there a significant performance advantage to using them? I hate using the pinch welds every time I have to change tires out, and a set of rails would let me change both tires on a side with just jacking once.

I wouldn't worry to much about them - locally nobody (hopefully) will protest you for them and they're probably more of a disadvantage since it's weight.
Locally I had people in F Street that had CAIs, wider wheels than stock, one guy showed up with 2.0T Genesis lowered, with a tune, wide wheels and who know what other shit he had there.

If you end up competing in national events, just take them off.

 

[SteveW]

edit: disregard

 

[qtrracer]

We went through this with the Fox chassis and sn95 cars except for SFCs. No question these helped the flexi-flier Foxes and to some extent the sn95s. Even STBs and G-loads were outlawed for a bunch of years. Fox sand sn95s couldn't compete; had to go to ESP or CP. but even in those classes, "jacking rails" were not allowed even if SFCs were.

Frankly, I can lift one whole side of my '16 GT from either a forward or rearward jacking point - not using the pinch welds.

Coming from the Fox and sn95 cars, the 6G is light-years ahead for body integrity and rigidity. I can see perhaps a vert needing them but not a coupe. Just extra weight.

 

[boardkat]

jacking rails are specifically prohibited in *S/ST*/SP* and outlined as such in the rules. legal in SM*/*P/*M. see 15.1 for *SP (and below) exclusion here:

http://cdn.growassets.net/user_file...lo_Rules_w_front_cover_reduced.pdf?1471970253

 

[Ugly John]

Well nuts. That's pretty specific there... How difficult is it to install and remove the jacking rails? I HATE using a puck and jack for each wheel...

 

[boardkat]

Well nuts. That's pretty specific there... How difficult is it to install and remove the jacking rails? I HATE using a puck and jack for each wheel...

are you competing @ NTs/MTs/pros/nats? if not, i wouldn't worry. S550 chassis is solid, it's definitely more of an issue with older cars (and the stiffening advantage, perceived or otherwise). locally/regionally, it's a non-issue on our cars IMO (or a simple conversation with your competitors)

 

[SteveW]

jacking rails are specifically prohibited in *S/ST*/SP* and outlined as such in the rules. legal in SM*/*P/*M. see 15.1 for *SP (and below) exclusion here:

http://cdn.growassets.net/user_file...lo_Rules_w_front_cover_reduced.pdf?1471970253

I wiped out my post above. I was way off and probably delirious from shoveling all this snow we're getting today.

 

[DickR]

If your jack has an appropriate lifting pad you can jack the rear at the diff and the front at the cross member. The front probably needs to be on low ramps such as https://www.summitracing.com/parts/bti-rr-scale-2/overview/ Also I'm MUCH more comfortable jacking this way when using jack stands.

Works well at home but I don't change tires at events so carrying the ramps and an appropriate jack in not an issue.

 

[Ugly John]

Thanks for the replies. I went ahead and ordered the Steeda rails, but I plan on placing the jack stands on the original pinch welds...

 

[HoosierDaddy]

If your jack has an appropriate lifting pad you can jack the rear at the diff

With the previous gens, the diff was welded to axle tubes which were supported by springs which were supported by the chassis. So the forces of jacking the diff went thru components designed to support the weight of the car. The diff in an S550 is bolted to the chassis with bolts that only need to be strong enough to support the weight of the diff and any torque it transmits to the chassis.

 

[DickR]

With the previous gens, the diff was welded to axle tubes which were supported by springs which were supported by the chassis. So the forces of jacking the diff went thru components designed to support the weight of the car. The diff in an S550 is bolted to the chassis with bolts that only need to be strong enough to support the weight of the diff and any torque it transmits to the chassis.

Interesting. However, I'm not a mechanical engineer and my physics is very rusty but what about the engine torque multiplication by transmission and/or differential gear ratios? Don't those twisting forces also have to be resisted by the diff bolts?

Thanks,

 

[HoosierDaddy]

The diff in an S550 is bolted to the chassis with bolts that only need to be strong enough to support the weight of the diff and any torque it transmits to the chassis.

Interesting. However, I'm not a mechanical engineer and my physics is very rusty but what about the engine torque multiplication by transmission and/or differential gear ratios? Don't those twisting forces also have to be resisted by the diff bolts?

As noted.

I'm sure people have jacked these up on the diff. I'm just saying it could be asking for trouble.

 

[c_reber]

I hate using the pinch welds every time I have to change tires out, and a set of rails would let me change both tires on a side with just jacking once.

Are we not supposed to do this? (note: I have a coupe, not convertible). I regularly jack the car from the pinch weld near the center of the car and change both tires.

Sponsored