Weight Loss Vs Grip

[Harry]

A little while ago I put up a post about getting round the track quicker with a minimum budget to spend over winter the most cost effective suggestion was weight loss (by removing interior etc not high tech carbon panels) as put forward by Gareth.

This got me thinking is there a point at which weight loss would compromise handling and if so would the adverse effect be more pronounced on low or high speed corners, obviously tyre choice would also impact on the outcome using sticky (888 for example) over non-sticky tyres my car runs pretty well on Kumho so they would remain.

I doubt very much that I would remove more than 50-100 Kg but this would raise the power output from 230 BHP/Tonne to between 240 and 250 BHP/Tonne based on a static weight of 1175 KG and a BHP of 271 and torque of 240 lb/ft (as measured at the APT Dyno Day last year)

Torque would be increased from 204 lb/ft/Tonne to between 213 and 234 lb/ft/Tonne.

Not huge power but enough to be entertaining the question is how much weight would need to be removed before affecting grip through corners over the standard weight.

[Stuart]

In my experience of taking a 1500kg car with 195/50/15 tyres and 150hp down to 1050kgs with the same power and the same tyres, I would say that there is nothing you have to worry about. I reckon you could theoretically go down to about a tonne, maybe lighter, without causing any issues.

[Harry]

Hello Stuart it was really a hypothetical question to flex the old grey matter, but you never know what some of our expert builders have found.

Certainly what I have in mind wont cause any problems

[Stuart]

Factors to consider then

power
weigh
weight distribution
drivetrain
tyre width
tyre compound
suspension type and poundage rates
downforce
ARBs and stiffness

All of those will need to be chewed over before you get a meaningful answer H.
The Sierra, M3 and Golfs were all massively lighter than standard without any extra power or downforce and had huge levels of grip. I reckon that the Sierra @ 1050kgs would have needed 250hp to be genuinely fast and another 100 or so to become a handful on R888's, but then you'd just use better tyres, driver training and complimentary mods (better brakes, harder suspension to 'use' the tyres, improved cooling and oil supply) to manage things. If 300 bhp per tonne is manageable with a good set up, you would probably need to get into Hayward territory with 500+ per tonne to get something that requires relearning to drive properly. The trouble is mate, if you have that kind of power surely you have that kind of standard brakes, suspension etc?

Tough one mate; make it more quantifiable

[Danny@APT]

I think the only noticeable effect you'd feel from minor weight loss (rear seats, spare wheel, simple trims, etc) is the improved acceleration and braking. When I had a track session in the Ford with the rear gutted, it certainly felt like it was more eager to get going, whether that was partly down to the increased road noise or not I don't know.

I think it's only when you get to Gary/Logan's level of weight-loss that you'll feel handling differences due to the imbalance front to rear. Most of the weight in Evo's is on the front, but most of the area to trim the weight is from the engine bay-back, which is where corner-weighting and altering coilover heights is necessary to return the balance. I don't know how Scooby's compare though?

[Ben]

The white MKII I had was fitted with some very good coilovers, even with terrible tyres it still handled amazingly well, almost to the point it no longer felt like a FWD and more RWD, it was very odd how you could slide it through the bends (prior to chucking it in the dirt at marham ). I remember stuart having some good tyres, my suspension compensated for the woosung dark horse kevlar tyres allowing me to easily keep up through the bendy stuff .. remember my MKII was the 8v as opposed to Stu's 16v with the longer legs.

I would have loved to try the car with 888's, that combo with the suspension would have made that car sensational through the bends.

[maff]

The biggest difference having the 200 stripped made was all the extra road/tyre/diff noise.

Sounded much more like a race car and that alone has to be worth 1 second a lap

[Harry]

First thing to say is that the car handles very well as it stands now due to the work carried out by the previous owner Mikey S and his guru Mike B so the starting point is a pretty solid platform. To be honest the only problem I have (apart from the driver) is under heavy braking on downhill bends such as Coram where the back end goes very light, cant bring myself to left foot brake and add power to balance the car

Stuart to answer your points

power circa 250 bhp/t and 230lb/ft/t
weight target 1100Kg
weight distribution 60/40 front to rear and 50/50 across the car
drive-train 4 WD
tyre width 215 40 17
tyre compound Rubber Black (whatever happened to white wall tyres)
suspension type and poundage rates Adjustable Coil Overs
downforce front P1 bumper rear boot mounted Spoiler
ARBs and stiffness front and rear but no idea of stiffness assume standard
with this set up the car corners very flat with little body roll

Dan you hit on a very valid point with the weight distribution if the weight saving is from the rear of the car then the balance (60/40) a 100kg saving would change the balance to 65/35

One advantage of a Scoobie is the low centre of gravity brought about by the flat 4 engine so perhaps the weight differential is not so pronounced.

would corner weighting and suspension adjustment bring about a 50/50 balance?

[Mr Fletcher]

get your wheel barrow and fill it with dirt and run down the garden in and out of some flower pots then empty it and try again

basicly leave Russ in the pits :biggrinjester:

[Harry]

get your wheel barrow and fill it with dirt and run down the garden in and out of some flower pots then empty it and try again

basicly leave Russ in the pits :biggrinjester:

Great strategy Jason but then I would only get lost and take longer to do a lap