Peteinjp

Of course it is in the event of an accident- but in terms of torsional stiffness?? My body guy said he's suggest keeping it for torsional rigidity of the body. However I'm beginning my quest for weight removal and starting with the rear. FVD has a kevlar/carbon replacement that seems like a good place to start.

His excellent thread starts with the FVD unit here: https://rennlist.com/forums/964-foru...l#post16541163

His car is caged- however mine is not. I'll be doing a bolt in cage but that is a few years off as the kids still manage not to hit the rear glass...

What say ye rennlisters... significant structural unit or just for crash protection??

Pete

jonathant

Won’t matter at all for torsional rigidity since the anchors (the bumper spring/piston units) are round tubes that can rotate (although they are stiff).

If you have the welded RS collapsing tube supports, rather than the heavier stock spring/piston units, then it may provide a little extra, but not a lot due to the long torque arm.

koenig_roland

Removed it and it made nothing negative at my car, even at the track.
You`ve to find a solution for a tow hock, if you plan to track your car. The Kevler part from FVD does not offer a thread for fitting the OEM hock....

Front and rear bumper beam are roughly 10kg and this is what matters :-)

Goughary

Can i mention....the tow hook - if you "tow" at a track and pull from the bumper- you are very likely to rip the entire bumper from the car. Those tow hook holes and the oem tow hook is designed to roll a car onto and off of a trailer. Trying to pull a car buried in a sand trap....not gonna happen from the bumper without damage.

So be careful. And no...you don't need it for that. You can mount tow hooks under the car for trailers...and if you plan to track the car- install a real tow hook front and rear.

As to crash protection- the bumper is there for low impact bumps. And since it's a huge beam, I'm sure it does something for high impact hits under certain circumstances- but i don't know what...

Question- what did the actual 964 cup race cars use? I imagine since they competed in a spec class they didn't go too light weight...but I'd be interested to see how different the bumper bar is relative to the over-done bricks we have front and rear. As if someone were going to expect to have a hard hit- you'd imagine the race cars would have expected it and been designed for the impact...this should give you a sense for how light you can go and still be reasonably street safe.

Peteinjp

Trying to stay out of the sand but I have been there! Although I didn’t Need a tow.

So what is a real tow hook and where does it attach?

I wonder what the cup cars used? Is there anyway to find out?

cobalt

The BaT auction selling the US cup car going on now has gobs of info that might help. I just replaced the 5 mph impact absorbing supports with the support tubes for the front and rear bumpers on my track car and it did save several pounds in total. Although I don't know what your regulations were or if your car came with them. I also found as i mentioned in another thread that the non impact absorbing rear 996/997 bumper supports are identical to the 964's fronts at a fraction of the cost new.

You can save some money and have holes cut into the aluminum bumper to lighten it. I just don't see the value in the kevlar piece. Although something to protect the tub from a rear end impact is worth keeping. I am currently rebuilding an engine from a car that spun and hit a pole going backwards and although the impact was decent enough to go past the bumper without it the damage would have been far worse. The engine damage was extensive enough with a broken distributor, A/C bracket, Rear engine support, Rear pulley, power steering pump, engine tins, One of the bosses that mounted to the engine support stud broke off, The trans also sustained a broken mount and the end of the trans where the rubber support rod goes snapped off. The engine is apart and is being inspected for a bent crank or any other damage since the pulley took a hit. Hopefully the engine will be salvageable, so far I believe it is. IMO if the rear support wasn't there the engine would have been toast.

Although IMO the best weight savings comes from above. If you have a sunroof it is worth removing.

Peteinjp

Haha- I was the one to egg you on with the sunroof removal! I don't have a Pino but luckily being in Japan my car is slick stock. I hear you about the rear impact and engine protection. That is a serous consideration. Drilling may be a better way to get some weight out without loosing much protection. Bill V sure did a number on his bumper. I wonder how much the kevlar unit would do for protection. Kevlar is tough stuff..... The German site has abetter price coming out to $823- and either way I have to ship to Japan so its significant cheaper.

I'm not sure what bumper supports I have in the Japan car. May already be the tube type so I need to check that. FVD has a "motorsport" version that is .3lbs but looking at it what it consists of the price hurts pretty bad. These aluminum ones seem interesting at that price:

https://www.netzwerk-911-shop.de/s/cc_images/cache_12281006.jpg?t=1585309978


I'm seriously leaning towards the lexan rear window- that's a good one and not way to expensive to purchase and install. Easy to go back and I never use my rear defroster.

Pete

cobalt

I kept the front and rear glass in my track build but replaced the sides with polycarbonate. The FVD units are the same as the factory. Try part number 99650501901 for the fronts they are $37.57 from Sunset Porsche vs $93.29 for the 964/993 parts and are identical.

JasonAndreas

Having been hit three times myself, and watched numerous 964 and 993 at various speeds hit the walls up at Loudon and each other at Lime Rock, I can't imagine removing it to save weight. Kiss your engine good bye. You want to dissipate and spread the energy as far away as possible from your engine and gearbox. Once either of those are cracked, your insurance company will total it.

There is some reinforcement welded to the front of the chassis endplate for the tow hook on the RS and CUP, i believe? But for a quick tow around the track and back to the pits, i've never seen one fail.

Peteinjp

Don't want to be kissing my engine goodbye...... definitely reconsidering this one. Is Kevlar structurally worthless? Thanks for the real world input.

Pete

RSA964993

A friend of mine and I raced our RS America’s for years and we were always looking for something that improved the performance of the car. Weight was always the enemy and he decided to move the rear bar as any weight savings were good, from the rear even better. He looped it at turn 2/3 at Road Atlanta during a race and backed it right into the wall. Engine took direct hit and the roof was actually wrinkled. RIP RS America. Anyone who looked at the car concluded the crash bar probably would have saved the car.

Peteinjp

OK OK - I give.... keeping the beams!

Goughary

Little factoid- i raced in the very first race at London when they rebuilt the track from the old road course to the now-oval with bits of the old track up the hill...back in 89 (i think) in the class that was then called Sport Renault (now spec racer Ford). No one knew the track as it was the first open weekend. So, needing track time, i had asked around to get a ride so i could see the track from a car prior to my first session - Ken Payson agreed and out i went in the passenger seat (i was 18 or 19 yrs old) of a, Showroom Stock A, Peugeot 505 sedan to learn the track...it was because of that 505- that wonky floaty bouncy trouncy tigger of a 505, that my little tube frame four banging Sport Renault felt so easy to drive, and sure of itself, that i was the only person in our field that wasn't lifting going into the banking ( flat out) and i was 25 seconds ahead of the second place car by two laps from the end of the race. (And then stupidly i looped it and hit a wall backward on the last lap, car stalled, he caught and passed me, and i finished second -can't win them all)...

On the tow thing- i agree- pulling the car in the direction it rolls is not really a problem- i was talking about hooking it to a crane and lifting and pulling the car hard by the bumper bar. It's held on by four m8 bolts- and if it lets go, the plastic bumper cover is bolted to the rear quarter panels- silly amounts of damage would be done.

For the comment about what the euro cup race cars did- i meant - what did they do for a bumper bar? Was it the same heavy weight bar we have? Or was it a lighter version of the same?

cobalt

LOL my father had a 505 diesel for a short time. I think I understand

Goughary

It was Showroom Stock B, not A...

Really wish SCCA never killed off the showroom classes. They were great.