"More expensive"
According to one trader, less expensive, because normally all you buy as the replacement is the plastic bit, not all the metalwork.
"Heavier"
Not much. Do you measure your fuel by the half litre?
"Can't bend them straight or weld them up"
Seen someone do both. Welding a metal bumper can only be done under very limited circumstances as the book says the main part is a single piece of metal, from bumper bolt to bumper bolt, not two bits of metal welded together. Many scruts will fail a re-welded bumper.
"Increased inertia makes the kart less responsive"
Take off the datalogger. It has as much inertia.
"Increased drag=slower at end of the straight"
That's a possible. However at the NKRA grande Final, the number 4 driver (who set a fastest lap) was using a plastic bumper.
"Makes it easier for following drivers to fire you off"
At the same time it makes it more difficult for following drivers to lift and flick, the favoured manoeuvre for those wanting to remove a rival from the track. I've seen drivers survive shunts that with a metal bar would have probably have dumped them in the tyres spinning, because the kart stays going forward, including a high speed impact at the end of Buckmore straight that ripped the bumper clean out of its mountings. That would have been much more serious if done to a metal bar.
"When you do go off backwards your neck absorbs the impact rather than the bumper bolts "
When you go off backwards, the plastic absorbs more energy in deforming than its metal equivalent. Then the bumper fastening deforms before you get to the bumper bolts.
If you hit hard enough that we are comparing the tensile strength of bumper bolts, you have a lot more to worry about that necklash.
I'm impressed by the reports of those who have driven them regularly, I think it's going to be personal opinion as to whether any particular incident is / would have been more survivable with either type. This includes one incident where the end of the bumper was bent so far it went inside the tyre and wore away the bottom half as it returned to shape. Not a survivable incident with a metal one.
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Plastic rear bumper tryed one yet by 'jack17' (19 Oct 2008 @ 19:15)
