1300 Kg Track SUPRA project

[josbeat]

I am frustated , three days in front of the computer and I have not idea what tyres will be the righ choice.

I have 245/40r18 toyo R888 at the front and a 265/645 R18 pirelli slick at the front and the slick is biger in height than the toyos but on the Toyo web page say the diameter of the 245/40 is 653 mm !!!!! so how big is the slick?? if on the side say 645 mm how mutch is the diameter really????
I am lost because I am trying to select a set of tyre for the track and set the floor height of 100 mm to the ground and then after the trackday put a set of street tyres which can give me 20 mm more of heighy to rise up the car to a safe height but is really difficult because nobody say the truth on hes tyres.

Like the supra dont have to much room in the wheel arches so if I like to use the flat floor and reading that 100 mm is the minimum height to get downforce I have two ways to get it ,
1 - lowering the overal flat floor till get the desirable height, using some spacers and using an air dam at the front bumper to lower the splitter and then I can use slicks but the slicks have big diameters so to use the Supra o the streets I need so much taller tyres or adjusting the height of the damper.... no way
2 - using a semislicks I can lower the desirable height with lower profiles tyres and small adjuste on the dampers thanks to the small diameter giving more room on the arches and for street, use a normal street tyres with 20 mm bigger diameter.

on the first point the use of slick will need harder springs and special settings...... uhmmmm no way because on the public roads will be a non-viable use. but slicks are slicks , full of grip and lower weight.

on the second point , maybe with the help of the flat floor, lower center of gravity due a lower chassis position and harder sidewall on the tyres .... maybe we can get the same grip of a full slicks eh??? then no need to use an agresive chassis and suspension settings so the use on the public roads wil be viable

what do you think guys, are my reflections correct?


at the moment I ike a lot the posibility of drive my supra any day I want so.... I will have time in the future to radicalice it only for track use with plexi , no window lifters ,no central looking , full stiff suspension and a full welded cage but not now.

 

[atmperformance]

I've run into this problem before. i think they have 10mm of wiggle roll so a 215mm tire could still be called a 225 at the same time so can a 235. normally you have to go with the same brand to have some kind of consistency but even that's not guaranteed.

 

[jdmfreak]

I know with big mud tires some companies measure including tread and some measure not including tread so a 33in tire could be 35" or 33" overall brand new and then 33" or 31" bald respectively....... I don't know why Street tires would be any different.... This could also account for some of it

 

[Van]

Like the supra dont have to much room in the wheel arches so if I like to use the flat floor and reading that 100 mm is the minimum height to get downforce I have to ways to get it ,
1 - lowering the overal flat floor till get the desirable height, using some spacers and using an air dam at the front bumper to lower the splitter and then I can use slicks but the slicks have big diameters so to use the Supra o the streets I need so much taller tyres or adjusting the height of the damper.... no way
2 - using a semislicks I can lower the desirable height with lower profiles tyres and small adjuste on the dampers thanks to the small diameter giving more room on the arches and for street, use a normal street tyres with 20 mm bigger diameter.

on the first point the use of slick will need harder springs and special settings...... uhmmmm no way because on the public roads will be a non-viable use. but slicks are slicks , full of grip and lower weight.

on the second point , maybe with the help of the flat floor, lower center of gravity due a lower chassis position and harder sidewall on the tyres .... maybe we can get the same grip of a full slicks eh??? then no need to use an agresive chassis and suspension settings so the use on the public roads wil be viable

what do you think guys, are my reflections correct?

Josbeat,
U know that the semi wets or full wets get greasy on dry pavement and have a shorter life span on dry pavement. I would continue to look at more slick manufacturers until U find the correct tire for U. It may still be out there. What tire brands have U looked at?
I too find it frustrating trying to find a combination that works best for both the track and street. So, I'm leaning toward the Dunlop Direzza Z2 as an all around tire, but it too will get greasy when it gets outside of its ops temp. When that happens, I'll wish I had slicks!
If I had more cash, I would buy a separate set of slicks and rims for the track, like U have.

 

[miekedmr]

Would these be allowed? Have you ruled them out?
http://www.cambertire.com/technology/Default.aspx

 

[josbeat]

Josbeat,
U know that the semi wets or full wets get greasy on dry pavement and have a shorter life span on dry pavement. I would continue to look at more slick manufacturers until U find the correct tire for U. It may still be out there. What tire brands have U looked at?
I too find it frustrating trying to find a combination that works best for both the track and street. So, I'm leaning toward the Dunlop Direzza Z2 as an all around tire, but it too will get greasy when it gets outside of its ops temp. When that happens, I'll wish I had slicks!
If I had more cash, I would buy a separate set of slicks and rims for the track, like U have.

Pirelli , Dunlop , Avon , Michelin.... minimum is they have is 645 mm Pirelli have those in 285 and 305

I found that the Kumho v70 semis have the set I like and they have the correct diameters in 285/30 and 305/30 wit 623 and 636 mm of diameters and then will be easy to get a set of street tyres with bigger diameters.
dont know what to do yet but I have time, the slicks I have still in good shape so..

happy new year!

 

[josbeat]

Would these be allowed? Have you ruled them out?
http://www.cambertire.com/technology/Default.aspx

I have no idea , but they don have my tyre sizes at the moment but will be good to follow the site.
thanks
happy new year

 

[josbeat]

the difusser I made and the current oil tank fitted
the diffuser have 7º but it is adjustable
the flat floor is finished with a new medium part modded
soon some videos with air flow tests
and also the new exhaust is on the way , 3" height instead 4" I have now

 

[Van]

Hi Josbeat,
From what I've read your diffuser should lessen the turbulence of the air off the rear of the car. For example:

 

[josbeat]

Hi! Van
I hope to get a good amount of downforce with it and the flat floor, the angle of the diffuser is different for every car and the rear wing and or a rear spoiler interact with the diffuser but 7º is the starting point, it is the maximum without turbulences but it posible to use high angles if the rear wing help.
but the flat floor height is not the ideal but now I know how to do it, I found a piece of plastic to use like an air-dam so now I can lower the front splitter and the rest of the floor will be easy to do it just with some spacers in between .
the idea is 100mm with street tyres and 85 mm with track tyres, now it have 135 mm. so 30 mm. spacers and 5mm. lowering the suspension, then it leave me a 80 mm supension travel, suficiente I hope.
soon the results

here it is what I did this weekend

 

[Van]

WOW! This is really coming along Josbeat.
On the Time Attack Forum http://www.timeattackforums.com/for...eal-height-introduction-my-mk2-golf-aero.html, I read a build in the Aero section, where they added side skirts using angle aluminum and screwing on vinyl so that the air that is split at the front stays under there all the way to the diffuser. It is an interesting read. I'd like to hear your opinion on that set-up.

 

[josbeat]

WOW! This is really coming along Josbeat.
On the Time Attack Forum http://www.timeattackforums.com/for...eal-height-introduction-my-mk2-golf-aero.html, I read a build in the Aero section, where they added side skirts using angle aluminum and screwing on vinyl so that the air that is split at the front stays under there all the way to the diffuser. It is an interesting read. I'd like to hear your opinion on that set-up.

yes that was my first idea , I bought a plastic angles( easy and cheap to replace in case of impact) it have 40 mm walls if you see the diffuser it was made with that height on the sides but some people say that it is dangerous because it can loose downforce over bumpers and loose grip on the middle of the corner.
I been looking for race car with those walls fitted and the only one is that Golf (not really a race car)
I desingned the outsides walls of the diffuser thinking to keep the wheel turbulences out of the clean air and thinking to follow a line to the front of the floor with those angles.
but not sure if I will use it

 

[Van]

Are U referring to the problems in F1? For example they've been forbidden as some cars got punted off course and injured the drivers.
Here is a quote from Wikipedia: "In following years other teams copied and improved on the Lotus until cornering speeds became dangerously high, resulting in several severe accidents in 1982; flat undersides became mandatory for 1983.[9] Part of the danger of relying on ground effects to corner at high speeds is the possibility of the sudden removal of this force; if the belly of the car contacts the ground, the flow is constricted too much, resulting in almost total loss of any ground effects. If this occurs in a corner where the driver is relying on this force to stay on the track, its sudden removal can cause the car to abruptly lose most of its traction and skid off the track."

 

[josbeat]

yes something like that jejeje
today I did a little test with the diffuser at the higher possition and the rear wing at the lower possition (street setting) and........ a lot of turbulences jajajaja no miracles here jajaja

ideal as I read will be flat front splitter and flat floor but with a 20º angle just in the edge at the front of the splitter and a little rear bend arround 2º-3º at the back of the floor and 7º diffuser , all with a 3" floor height
all is possible but if I want to keep using the car on the public streets I`ll need to finde a good compromise.

how we can see if with a 100 mm car height and those angles closing the flat floor is the same as have the car height set at 50 or 60 mm ??? ....with a expensive wind tunnel .
no way!

I am thinking to go back to normal height with the correctly roll center and lowering the body of the car and the floor .
what will be the best? roll center - high car or no roll center - low car ?

 

[Van]

Josbeat,
I now realize U have developed the MK3 Supra as no one else has on SM. Also, I've decided to follow your lead in developing my Time Attack Supra, although I'm about two years behind U in the development process. I think that as we test our set-up we might both profit from us sharing what we discover along the way.
As regards your question about roll center and making adjustments there, that is an area of chassis tuning I leave to my friends at VIP Performance, so I can't help U there.

 

[josbeat]

my car keep my mind busy jaja and my pocket empty jajajajaja
I feel well when I change something and it works
like the dry sump, front splitter, gearbox...

 

[josbeat]

it is very similar to my car and similar in chassis measures with our supras eh?

http://www.gtspirit.com/wp-content/uploads/2013/03/Maserati-GranTurismo-MC-Trofeo-2013_2.jpg

 

[josbeat]

first test , road configuration
http://youtu.be/fJV_Qn3KHdo

second diffuser test, not full race configuration
http://youtu.be/uV-sb0DqT5g

 

[Van]

Hi Josbeat,
I'm surprised the diffuser moves as much as it does in the middle, despite the stiffening that has already been done to it... Do U think, in any way, that movement affects the effectiveness of the design?

 

[josbeat]

Hi Josbeat,
I'm surprised the diffuser moves as much as it does in the middle, despite the stiffening that has already been done to it... Do U think, in any way, that movement affects the effectiveness of the design?

yes I think and the guy who made it was with me in the car and he told me to return it to hes place to reinforce it in the middle.
but the most important is that the diffuser work weel also on the sides at 10º ( the desing of the diffuser is 7º ) soon I will try with the angles fitted on the side of the floor which is the max angle I can run it with out stall.

now also I am looking to replace the fuel tank model and location , I need to cover it or separate it from the copckit.
I like to use it http://www.proalloy.co.uk/userdata/PRODPIC-293.jpg where the rear seat are and fitting it in the midle so it will be better but I dont know where move the battery.
do you have any idea were?
I was thinking to move it to the back of the right bucket but I need to move the seat foward too much ( i need to keep two seats) moving the head of the passegers too close to the roll bars... dont like.
or smaller gel battery ( no need a sealed box ) and maybe it fit there??