SUPRA SAEINDIA 2012

[Aman Ved Kalia]

Hello Members,
Me and my team are participating this year in the Indian version of Formula SAE called SUPRA here.The competition is mostly similar to the international versions apart from a few different restrictions.
I need a small help from the members who have already participated in the FSAE events as this is my teams'first time in the competition. I have a virtual design presentation in 3 days and i'm kind of stuck on the tyre selection.

Factors to keep in mind while selecting the tires. Initially, i considered 13"tires 205/60 for the car. But, i don't know the perfect reason for selecting those. I just considered them because of optimum diameter and suitable width. Please guide me as to what to look for while considering the tire so that i can keep my point more confidently in the presentation.

P.S. I did search regarding selection of tires in the forum before posting but most of the topics were regarding hoosier, goodyear or dunlop tires which are not available in INDIA.

[Aman Ved Kalia]

Hello Members,
Me and my team are participating this year in the Indian version of Formula SAE called SUPRA here.The competition is mostly similar to the international versions apart from a few different restrictions.
I need a small help from the members who have already participated in the FSAE events as this is my teams'first time in the competition. I have a virtual design presentation in 3 days and i'm kind of stuck on the tyre selection.

Factors to keep in mind while selecting the tires. Initially, i considered 13"tires 205/60 for the car. But, i don't know the perfect reason for selecting those. I just considered them because of optimum diameter and suitable width. Please guide me as to what to look for while considering the tire so that i can keep my point more confidently in the presentation.

P.S. I did search regarding selection of tires in the forum before posting but most of the topics were regarding hoosier, goodyear or dunlop tires which are not available in INDIA.

[PatClarke]

I thought the tyres were a standard steel belted radial road tyre in SUPRA?

If this is the case, I doubt many FS/FSAE teams can help because generally they run on dedicated racing tyres.

With road tyres, I would just choose the best deal you can get on 'sports' rated tyres. Maybe a little twisted logic here, but maybe the tyres with the worst wear rating, based on the supposition that the worst wear rating equates to the softest rubber compound and hopefully, the best grip?

Pat

[Jon Burford]

I think you can Toyo R888 in that size if memory serves me.
tripple 8's are road legal track tyres. they give good grip.
Although just a suggestion!

[shark.ashwa]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PatClarke:
I thought the tyres were a standard steel belted radial road tyre in SUPRA?

If this is the case, I doubt many FS/FSAE teams can help because generally they run on dedicated racing tyres.

With road tyres, I would just choose the best deal you can get on 'sports' rated tyres. Maybe a little twisted logic here, but maybe the tyres with the worst wear rating, based on the supposition that the worst wear rating equates to the softest rubber compound and hopefully, the best grip?

Pat </div></BLOCKQUOTE>

Yes I do agree with Pat here, I dont think you can get the Race specific tires that we generally use in FS. You can however go for tires that have the worst wear rating (I think they come as intermediate tires IIRC). I doubt you would get any data from the tire manufacturers about these tires but real world testing might probably be the best thing right now. I hope you have done your research on what dia, aspect ratio, etc is best for you....

Regards,
Sharath

[Aman Ved Kalia]

Well these are the points I considered for the tire without getting too much into the technical data.
1. Availability and Cost.
2. optimum aspect ratio for a 13"rim, to provide adequate stiffness against lateral forces.

This helped me select Bridgestone tyre : 205/60R13 87H. Organizers have introduced a new rule this year that a separate set of dry tires are also needed. Now how to recognize a dry tire and a rain tire if both are treaded.

And are considerations mentioned above satisfactory to support my selection?

Also as i'm using Lotus Suspension Analyser, the tire data requires some parameters that I don't know where to find, could anyone of you help me out. I have placed a "Red Question Mark" beside the query term in the pic attached.
https://docs.google.com/drawin...DieoOajN_voeeMU/edit (https://docs.google.com/drawings/d/1TjECLicz7bFOv9NZMwvykTfFyDBQDieoOajN_voeeMU/edit)

[Kirk Feldkamp]

How does one define an "optimum" aspect ratio?!

[Aman Ved Kalia]

I meant out of the possible width and aspect ratio available for the 13" rims 205/60 was suitable.

[Kirk Feldkamp]

Yeah, be careful throwing around that "optimum" word. There are rarely any optimumal solutions to real world problems... usually only trade-offs. http://fsae.com/groupee_common/emoticons/icon_wink.gif

[josh2417]

Aman,

you must understand that 205 mm width will have a lot of rolling radius. with the low power engine cut off at 4500 rpm, you want to use the thinnest tires. As such you can improve your cornering force and braking distance but your top and acceleration will drop. Plus unsprung mass will increase.

Betw we are coming as well, which uni are you?

Suspension guy
GS racing
India

[Aman Ved Kalia]

@josh2417: I know that too, that is exactly what is causing the dilemma, I think I will stick to 205 only for the time being.
I'm from Maharaja Agrasen Institute of Technology, New Delhi. Team Shaurya! First timers, so a bit tensed and confused :P

[Zac]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PatClarke:
I thought the tyres were a standard steel belted radial road tyre in SUPRA?

If this is the case, I doubt many FS/FSAE teams can help because generally they run on dedicated racing tyres.

With road tyres, I would just choose the best deal you can get on 'sports' rated tyres. Maybe a little twisted logic here, but maybe the tyres with the worst wear rating, based on the supposition that the worst wear rating equates to the softest rubber compound and hopefully, the best grip?

Pat </div></BLOCKQUOTE>

I think last year that was the case, but it looks like the Indian comp has updated their rules to something more in line with the other comps. This scares me somewhat.

"3.2.3 Wheels and Tires
3.2.3.1 Wheels
The wheel size of the car must be 203.2 mm (8.0 inches) or more in diameter. If any wheel
mounting system that uses a single retaining nut, it must be supplemented with an additional
device incorporated to retain the single nut and the wheel, even in the event that the nut loosens.
3.2.3.2 Tires (The tires may be of any size or type.)
Vehicles may have two types of tires as follows: Dry Tires: The tires on the vehicle when
it is presented for technical inspection are defined as its ?Dry Tires?. The dry tires may be any
size or type. They may be slicks or treaded.
Rain Tires Spec: Rain tires may be any size or type of treaded or grooved tire provided:
1. The tread pattern or grooves were molded in by the tire manufacture.
2. There is a minimum tread depth of 2.4 mms (3/32 inch)."

Given the rules, my first choice would be some sort of racing slick. Any team that figures out a way to get a Goodyear, Hoosier, Dunlop, Avon, Bridgestone, or other FSAE tire onto their car will be at an advantage. Even a F3 or other sports car tire would be a big advantage over a street tire.

Second choice would be a 13" DOT competition tire. Hankook, Toyo, Kumho and probably others make something in this segment.

Third choice would be a "summer" radial tire. I'd look for something with as closed a tread pattern as possible (not many grooves or lugs), as low a tread wear rating as possible, and as low a sidewall height as possible. I'd also consider shaving down the tread to increase the cornering stiffness and/or doping the tread with something like hot lap.

[josh2417]

Aman,

We are first timers as well, but we went in fr 13 inch for packaging only, otherwise would have stuck with 12 inch. But makes sense to go with thinner ones.

Zac,

Just think about this. The engine produces 37 bhp at 5500 rpm. The ECU is flashed to cut off at 4500 rpm. With exhaust tuning and Intake , you might get an extra 2 Bhp???? But the car will weigh 320 kg with driver minimum. Calculate the power to weight and you get hardly 100 Bhp/ ton. Now tell me, do the slicks with wider tread make sense.

[Zac]

Being under-powered and overweight makes your ability to take a corner at speed (and maintain that speed) even more significant. If you can exit a turn 2 mph faster than your competitors you maintain that advantage for the entire straight.

The reason to use a racing slick isn't a wider tread. It is the compound. After it comes up to temp, the tires used by most FSAE teams will be able to pull 1.5g steady-state pretty easily. A typical 13" passenger tire, particularly one designed for the Indian market, will be lucky to see .9g. On a 50 foot circle, that's a difference of 1.3 seconds.