Weight Difference - Worth It?

[lukeydoo]

I can get a rollcage welded in made of CDS steel or T45 steel - the T45 costs an extra £600 which brings the cage to around £2k. The T45 weighs 10-15kg less than CDS.

Is £600 worth it for a weight loss of 10-15kg? Opinions please.

[lamcote]

It depends what you're doing. I think it would make a measurable difference over a typical lap. I would guess roughly 0.2 seconds faster per typical racetrack lap for each 10kg lighter (10kg slows an F1 car by c.0.3 seconds per typical lap) so if you are racing, it may be worth it. In terms of how it would feel, I would say, since it is in the middle of the car you won't feel any difference to performance or handling.

If I drive without the spare wheel in place (which is about 10kg right at the front) I can't feel any difference in acceleration, but the car definitely responds more easily/quickly on turn in.

[JoeCool]

Personally I'd check whatever the MSA requirements are for whatever you intend to use the car for. It could be a compliance issue.

If it's just for a track car, then no,10Kg savings is not worth £600 unless you're actually in motorsport with a high chance of winning.

[smart51]

Fractions of a second aren't noticeable behind the wheel.  It only makes a difference in a head to head race or against the clock.  A few tenths per lap might win you a race.  That might be worth £600.

[lukeydoo]

I'm just building it for the giggles - family members do tarmac rallying but I wanted to build a K20 MR2 from a bare shell up as an ongoing project to stop me from going mad at work, not to race. I like the doing, the learning and the research.

I'm thinking of the weight saving against carbon panels - the average carbon bonnet will net circa 2-3kg weight saving from a metal one which has been hole-sawed for a cost of £500 whereas the T45 cage would net 10kg and would remove weight from higher up in the car which is always a bonus.

[JoeCool]

It would... but you're into dimishing gains by that point anyway. Have you taken all other steps to reduce the weight of the car? Light wheels/tyres, interior stripped, roof removed, buckets to replace seats, light exhaust system, A/C removed (guess so if you're going K20).

If it's a no expense spared car and built to be as light as possible then of course, go for it, but personally I'd just run the car with 10L less fuel in the tank or go on a bit of diet myself for £600!

[lukeydoo]

It'll be running a smaller tank placed at the front of the car. Hmmmm, all good points though. £600 buys a lot of tools for instance, plus my cage design is reasonably Spartan so there shouldn't be much weight in it - I just don't want to weigh it at the end and think it could have been 15 kg lighter.