Tyre footprint
Turbo Mini Forums

The friday that I went to Avon I let the Sprint down off the axle stands and realised I still had 1.5 degrees negative camber on the front. Since I was just about ready to leave I couldnt be bothered to change it to 0 degrees so left it.

This week I decide to chalk the tread and take a print of the tyre footprint on a piece of black wood with negative camber and 0 camber. Believe it or not the 1.5 degree footprint is considerably bigger with the same tyre pressure.

Any thoughts? I thought it would be the other way round

Paul

I seriously doubt it!

the footprint isn't the whole story though. Presumably the actual pressure acting over larger (neg camber) footprint will be less even?

Obviously there is correlation between total grip and footprint, but i'd be interested in some sort of pressure plot accross the entire tread for both setups.

I also wonder how the footprint changes as the tyre spins up? I.e. I wonder if the neg camber footprint is still larger when actually trying to get off the line.

not exactly a helpful answer I know...

Too many projects!

could it be due to how you are measuring the foot print?

are you baking sure the suspension isnt compressing (and therefore changing the track)

JP, those were my thoughts too but dont have any way to measure the pressure across the print, hence wondering others thoughts. I must admit the smaller print is brighter which could indicate more even pressure but, could be due to more chalk.

I seriously doubt it!

Joe, the width of each print is within a few mm, but the front to back size is the difference - by about 20mm

I seriously doubt it!

hum, interesting,

any chance of pics of the two footprints?

I seriously doubt it!

Heres the pic. The left is negative camber, right is 0 camber. Both from the same wheel with the same pressure.

I seriously doubt it!

ok, from that I think the right hand one has not printed properly, the top edge of it does not seem to follow the same profile as the bottom edge. (unless its just the pic)

I see what you mean but it was sat there on the wood for 2 days in the garage without moving. Cant see Id get a better print

I seriously doubt it!

I would say the 0 camber looks more even - nice bit of wood BTW

On 5th Sep, 2011 Vegard said:
I stand corrected. You should know

I seriously doubt it!

given the inward bias of the -ve camber, it should give less scrub radius and less torque steer too that said straight up should just be better.. lol

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Re - bit of wood. I,m glad I,m not the only one who has to push or drive the car on to a piece of wood before I can even get the low entry jack under it !

How long have the tyres been running on the car with -ve camber? Tyres ware to their camber so if they have been on there for a time then you would expect them to show a wider print. However if the tyres are new then it explains nothing.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

How did you take the print, Roll the car onto the wood, or dropped straight down off a jack?

Neil

Got A GTM With A Honda In the Back, and huge Nitrous bottle where the passenger seat should be when racing!

Theyve done about 20 miles

I seriously doubt it!

ive got a copy of Race car engineering by Warren Rowley and it has a very detailed section on tyre perfromance, more then welcome to borrow it

http://www.rowleyrace.com/publications.htm#pos5

1972 998 TURBO SLEEPER

I seriously doubt it!

Paul, i would ahve thought the most accurate way to measure the goodrich would be to roll the tyre one full revolution , maybe even two revs to allow it to settle, then look at the results,

think when you adjust the front suspension you roll the car back and forth to settle the tyre/suspension.

even better , roll the car over a tacky pach of some sort or another , them measure out one full tyre rev and compare,

carl

WWW.FORCE-RACING.CO.UK PLEASE CLICK HERE

well when i wasn't running 1.5 camber, my tires would wear on the in side (giving a lesser foot print i guess) now they wear much flatter and evenly, giving a more even and bigger foot print i'm guessing, so it doesn't suprise me mate.

Good work BTW on the chalk idea :)

Edited by Miniwilliams on 24th Jul, 2010.

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If your going to look into this in any depth, Id sugest getting a load of graph paper and an ink roller, and lock the suspension up at ride height before you start.

I would tend to agree, an interesting idea, but mabe a repeat of the test is what is needed.

If any testing I do gives odd results, I always check how it was measured and what could have caused an odd result (by the method). If all that check out then spend time analysing the results.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

^^^ you see what he said, well that was me as Ben was loggeg in on my laptop.

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