Matt21
|
| posted on 13/4/14 at 08:52 AM |
|
|
Trackdays - questions :)
Good morning
After having a brilliant track day yesterday at blyton park (my first dry track day since getting the car!!!)
I have a few questions
firstly, the positive camber on the back of the mk indy, how can this be sorted?
I have recently had the geometry set up and the back was set to (i think) 0.5degrees, but i cant remember now. this gives me a few problems, obviously
the first being the massive positive camber when cornering, secondly on my NS rear wheel, it rubs the arch on cornering and has worn into the tyre a
lot!
to solve this yesterday I put on a bit of rear camber, maybe 1.5 - 2degrees now, this solves the rubbing and I assume helps with the camber in
corners?
what effects will this have on handling?
at the same time as doing this I put slicks on and didn't notice and adverse handling apart from understeer (don't think i could get the
fronts hot enough)
secondly, body roll
I felt like I was going to tip the car over before I lost grip as there was that much roll!
I assume stiffer springs? I'm not sure what are on them at the moment as there are no markings, what's recommended for a 520kg car and
80-90kg driver? the shocks are protech
Damping next,
I stiffened each shock up by 3 clicks from my road set up to start with, 9 on the rear, 8 on the front. this was good but I added another click to try
and counter out the body roll a bit, didn't seem to do much. this was with R888s. once I put the slicks on I noticed a lot more understeer so
tried softening the fronts off but this didn't seem to help either.
can anything be done or do I just need softer compound tryes so they warm up faster?
tyre pressures (may be the cause of understeer too?)
on my slicks I had 19psi on the rear and 17psi on the fronts, I have no idea what they should be so just guessed, can anyone give me a better idea
what they should be?
dunlop sp sports
I think tha'ts all for now!
|
|
|
|
|
daniel mason
|
| posted on 13/4/14 at 09:07 AM |
|
|
check your rear upright hasn't bent and folded on itself! and make sure theres no cracks/fractures in them!
slicks will need a few laps to get warm then they should come good!
I have some formula Renault slicks for sale if you need some as with slicks.age and storage can make or break them! what age are they and have they
been always covered?
what size wheels are you running and what ride height/rake do you run.? id recommend 13" wheels/tyres with a decent sidewall and slightly
stiffer springs to sort fimness of ride out,then fine tune damping to suit!
|
|
|
rdodger
|
| posted on 13/4/14 at 09:37 AM |
|
|
Have a read of yellowcab's rebuild thread in the BEC section. If I remember correctly procomp changed the pick up point on the rear upright to
cure the rear camber issues.
|
|
|
DIY Si
|
| posted on 13/4/14 at 11:22 AM |
|
|
The rear camber issue is down to poor geometry, and will require surgery of one form or another to fix properly. IIRC the Indy gains positive camber
at the rear, which you can feel if you push hard enough as the back goes all weird and loose.
As for roll, stiffer springs is probably the answer. Stiffer dampers won't limit roll, but they will affect how quickly the car rolls. Might be
best to see if somewhere local to you can measure the springs for you, so you know where to head next. Otherwise you're just going in blind.
Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
|
|
|
jossey
|
| posted on 13/4/14 at 11:55 AM |
|
|
I saw you the night before going through gainsborough and dropped down to the track. it looked good.
didn't you have odd front tyres??
Thanks
David Johnson
Building my tiger avon slowly but surely.
|
|
|
britishtrident
|
| posted on 13/4/14 at 01:39 PM |
|
|
There are a three ways of tackling excessive body roll: springs, anti-roll bar or raising the roll centres.
Changing the springs to stiffer ones is the simplest and probably the best first move for you but you have to know what rate springs you already
have.
Springs normally have the rate in lbs/inch engraved on the top of the area of the spring that is ground flat.
From your description sounds like you need to stiffen the rear of the car more than the front.
Stiffening the rear more than the front should also reduce understeer perhaps by too much.
Once you have changed the springs an tested the effect you can consider the geometry mods to the rear that have been mentioned.
Stiffening the dampers as already mention has no effect on roll except to dampen the rate at which roll builds up, making the damping too stiff can
result in the tyres suddenly losing effective contact with the road. It is always better to err on the side of having the dampers soft than too
hard.
[I] What use our work, Bennet, if we cannot care for those we love? .
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
Matt21
|
| posted on 14/4/14 at 08:48 AM |
|
|
thanks guys
I have found out that the rear springs are 8.5 x 200, i assume the fronts are the same
the slicks I'm using are just some I got stupidly cheap, so totally unsure of the life of them, they're only for trackdays and I
don't think I could justify paying for another set tbh
the rears gripped fine after a few laps, but I just don't think there was enough weight over the fronts to get them warmed up enough.
another quickie, my engine seems to be using oil, theres no smoke and no signs of a leak :S
It's used around a litre in half a trackday :S
98 cbr900
|
|
|
