710 pressure for a light car?

Well I've finally gotten my scratch built car ready to drive and since there's only a couple of autox's left in the season up here I'll wait untill next year to buy proper slicks. Since I have 710's with only 3 events on them I'll be using them,anyone try them on a 900lb car before?.Being so stiff a carcass I'm thinking mid teens as a starting point,weather won't likely be to warm either so some tire flex may help produce some heat.

Thoughts?

I haven't run the 710s, but I found I need to run tire pressures not too far off normal Miata pressures in my RA1s on the Locost. I originally started with them fairly soft, but every time I added pressure I got faster. I think I run them about 5 psi lighter than Miata pressures now, but it's been a while.

I thought the same thing Wonkothesane.

Haha,sort of like this? http://i117.photobucket.com/albums/o50/kevlarcorolla/newracecar003.jpg

Clearly those aren't "710 on" being old hard radial ta's.

900 pounds? Wow, you weren't kidding when you said light. Yes, mid-teens would probably be a good starting point.

Pics, pics!

I thought this was going to be about an upside down oil gauge.

I thought it was about oil too...

so yes. about those pics?

I have a sheet on Hoosier -6 tires. There is not a huge difference in the reccomended pressures from 1800 lbs to over 3000. Hot pressure runs from 34 to 43.

I would think the lighter the car, the higher the "normal" pressure to help build heat in them. I would start closer to the max on the tire sidewall and go from there.

-Rob

Wonkothesane wrote: I can't help you with the help, but I've gotta admit that I saw that and read "710" as OIL upside down... I couldn't figure out why you'd have to run a different oil pressure for a light car! :)

Ditto.

Wonkothesane wrote: I can't help you with the help, but I've gotta admit that I saw that and read "710" as OIL upside down... I couldn't figure out why you'd have to run a different oil pressure for a light car! :)

I was trying to figure out what pressure would be high enough (and in what units) to be at "710"

rob_lewis wrote: I would think the lighter the car, the higher the "normal" pressure to help build heat in them. I would start closer to the max on the tire sidewall and go from there. -Rob

So what is the "normal" pressure ? Heat build up is normally not an issue in autocross. You start with the hot pressure. A race tire such as the 710 is not like a street tire. The so called max pressure is not an issue. Start around 30 psi and work from there.

I would think with the sidewall/carcas designed for a car at least twice the weight would be far to stiff.If the tire has some additional flex it will build heat sooner right?.I just didn't want to waste too many runs getting it close. Ok here's the car,started building at the start of the year and had set a target of june to start testing-didn't make it. Here's the 1st drive last weekend,its the 3 lap of its young life.Had a coolant leak onto the header as can be seen up the front straight so that was the end of the test.

http://www.youtube.com/watch?v=X4eQ_5MQZXs

Fantastic machine!!! Sorry, I can not offer any advice on tire pressures for that work of art.

In reply to kevlarcorolla:

You sir are The Man. I will build one of those some day. Take lots of pictures and post them somewhere so I can steal your ideas. Pretty Please.

Now THAT is cool! toyman keeps bugging me to build something like that. I say to him: all we need are the right dies for my bender and we can start.

On 710's: I ran 21-22 PSI in the ones on the Abomination (~1600 pounds w/o driver) so mid teens are probably not a bad place to start. But other posters have mentioned it being hard to get heat in the tires with such a light car and I have to agree. Don't get me wrong; I like the 710, it's a good tire but in this situation you might be better off dropping coin on some Hoosier A6's. The temps on those have to be kept low for them to bite well.

Thanks,the car is designed around 20" hoosier slicks and the 710's are just to finish(well start for me)the last couple of events for the year.No point in spending money for the hoosiers,rather have fresh ones in the spring to go along with the triple element wings front and rear. Tha vid is with the tires at 20lbs,I was just getting ready to start tire temp testing/tuning when issues sent me packing.Looking at the inside/outside endges of the tire afterwards makes me think its too hard,they are 195's on a 7" wheel and there's an inch of untouched tire on the inside edge with close -2 degrees of camber so.......

Toyman pm me your e-mail and I'll send you my photobucket link,I don't have tons of pictures but you can have a look.If you have a question than ask and I'll do my best to provide an answer.

Bike powered? What engine?

In reply to Streetwiseguy:

Yes,its an '02 R1 engine.A miata donated the hubs,brakes and diff.

1st autox yesterday,very little grip from the 710's with a pressure range from 15 to 25psi.Tires barely warm to the touch after a run and no stone/grit retention.

http://www.youtube.com/watch?v=v00QPY2exHo

Looked pretty good. I'm kind of surprised you don't have any pickup on the tires. The Abomination starts picking up sand and grit as soon as I unload it. How old are the tires.

In reply to Toyman01:

Tires were bought new this year and have 3 events on a completely stripped geo metro(last years ice racer)and they gripped like normal on it.

Our local events are basically an "endurocross" - think of it as around 3 laps of an autox course, with a warmup lap to get up to speed. The lightweights have to take that warmup lap at full chat to get the tires fully heated, normal cars take it easier.

I checked with Brandon, he's running 30-ish on his NT01s on a 900 lb bike-engined car. He found the same thing I did - every time he added pressure he went faster.

Tom, that was a very impressive run. You handled the lack of grip beautifully. If they weren't getting warm at all, then you probably should have dropped a few pounds out of them, like maybe down to 10. I know racing slicks go down that low sometimes on FF cars. I'll bet you can't wait to get those slicks, huh?