Major changes to Astra chassis

[Efratech]

i dont get what you´re thinking. but i preffer the mattig kit.

[PrecisionBoost]

Well.... I'm thinking that even the best 205mm wide tires in the world won't be able to hold 625whp.

At this point with 235Whp I have a hard time getting traction in 1st, 2nd, 3rd, 4th, and part of 5th

The car is unsafe to drive on the street even at this level of power... I can be driving in 3rd and punch it and the tires let loose and throw me left or right slightly.

Part of that is suspension, but I still feel that the car needs to have nice big tires to make it both fast and safe.

So.... even with a limited slip differential and equal length drive shafts I will need wide tires to be able to handle high horsepower levels.

Just look at the Astra DTM.... the fenders are flared and stick out about 4" to 6" in order to accommodate wider tires.



Here is another nice widebody example of a newer astra.... I really like this one

[PrecisionBoost]

So are you converting it to AWD as well?

How is it going to handle with such wide tyres? Do you have to change all the steering rack?

I may or may not go AWD or RWD..... depends on what I can do with the current FWD.

I want to put in the Astra VXR M32 gearbox I purchased.... if I break it.... I will go with a sequential RWD race transmission.

The suspension and steering will need modifications to accommodate the wider tires.... if I don't get the geometry right the car will handle very poorly and destroy wheel bearings due to extra load.

I actually hate the design of the Astra/Lanos front suspension so I would much prefer to do as some people in the UK have and convert the fronts over to a Porsche suspension/spindle.

Alternatively I may machine all new components, it depends on which bolt pattern I go with.

[PrecisionBoost]

The more I look at it.... the more I like the Astra DTM.... it would be very easy to modify the fenders like this since they are at 90 degrees to the fenders.... all it would take is one long piece of 5" sheet metal and tack it onto the fender to create the necessary clearance.

The DTM continues on along the door like I want but it does it down near the bottom as opposed to near the window sill like the other supercars

[benzino]

wow!

[PrecisionBoost]

The astra DTM weighs in at 1150kg ( 2535lbs ) with driver and fuel..... so I should be fairly close to that weight.

The astra DTM makes about 470hp and 380 lbft of torque

It has a RWD sequential 6spd and the tires are 240mm in the front and 280mm in the rear


So logic dictates that if the DTM Astra is making 470hp/380lbft and it's main drive wheels are 280mm Race tires my car will need bigger tires than 280mm

That is to say I should be able to smoke an Astra DTM race car in a straight line because we have the same weight but I will have 200hp more power and torque at a lower RPM.

That isn't a small margin... were talking 38% more power.

I am assuming of course that the DTM car is making it's 470hp at the wheels as opposed to at the crank.... otherwise the power difference is even worse.

[PrecisionBoost]

Ok..... let's do some comparisons....

2006 Chevrolet Corvette Z06.... RWD... 505hp 470lbft...
Fronts: 275/35/18
Rear: 325/30-19

2006 Dodge Viper SRT10... RWD...600hp 560lbft
Front: 275/35-18
Rear: 345/30-19

2006 Ferrari F430... RWD... 490hp 342 lbft
Front: 225/35-19
Rear: 285/35-19

2006 Lamborghini Murcielago LP640...RWD... 640hp 487lbft
Front: 245/35-18
Rear: 335/30-18

2008 Porsche 911 GT3 RS... RWD... 415hp 300lbft
Front: 235/35-19
Rear: 305/30-19

2006 Porsche Carrera GT...RWD...605hp 437lbft
Front: 265/35-19
Rear: 335/30-20

[PrecisionBoost]

So.... if the drive wheels of all these 500 to 600hp supercars are all over 300mm then I feel I need something up in that range to handle the power I want to produce.

Yes.... this seems like a big project.... but the engine is done.... I'm in the midst of working with a few people to figure out the roll cage... and I have a significant portion of the parts sitting on the shelf waiting to go into the car.

The problem I'm having right now is that the IHRA roll cage is slightly different than the standard FIA roll cage.

So if I got with an IHRA cage I can drag race but not road race.

If I go with the FIA cage I can road race but not drag race.

Kind of sucks..... but I think I will go with the FIA cage as I want this car to be able to run the local road course that is in the midst of being built just outside of town.

I talked with the drag racing guys and one suggestion I threw at them was "what if I only give it full throttle for the first 1/8 mile and then coast for the last half to keep the ET higher than 11.49s and trap speed under 135MPH

Hopefully they will accept this and allow me to run the car on the drag strip.

Once I have a good 1/8 mile time I can simply calculate that forwards to get a very good estimate on the 1/4 mile time (there are online calculators which figure that out for you )

Who knows.... perhaps if I get to know them good enough they will let me do one 1/4 mile pass after they see I'm a safe driver.

[PrecisionBoost]

Well.... I've found both my rims and tires.

Victor Lemans 18" X 11" with 25mm offset ( Porsche 5 X 130 pattern )

Quite a reasonable price from a company up here in Canada

http://www.1010tires.com/wheel.asp?whee ... del=Lemans

For tires I'm looking at 315/30-18 BFG Drag Radials

http://www.tirerack.com/tires/tires.jsp ... es&place=5

They are a true competition tire..... but I've found a pile of people that use them as their everyday performance street tires.

Many have managed to get decent mileage from the tires... considering I will be putting on less than 1500 miles a year these tires should last me quite a long time.... most people were managing to get 6000 to 9000 miles including regular trips to the drag strip

They are meant to be driven to the track, deflated.... ran as a slick.... then re-inflated for your drive home.

The odd thing is these are not really meant for autocross (due to sidewall design) but yet there have been a half dozen or more guys that have used them for that very purpose and managed to do fairly well with them.

With the low profile 30 series sidewall they should be similar to a 45 series street tire with respect to sidewall flex... certainly nothing like the competition R-Compound autocross tires but decent enough for driving around.

[jidasas]

As far as running at the drags...I know a few guys here who are allowed to run there cars but only for the 1/8th mile. They run only an 1/8th so that there speed is down...they do the same thing with motorcycles here. So, maybe they would let you run in 1/8th mile drags?


Jimmy

[2woo4you0]

First let me say I don't know much about drag racing, I'm far more into road racing and auto x stuff. Why not consider toyo R888s? Or Azenis or Hankooks 200tread rated tires if you want something that'll last longer. Remember OEM tires on cars like the SLR, ALina?, Mclaren, Viper, ect are 200-250 tread rating which isn't all that soft. DOT legal street tires are as low as 60 from what I've seen and a 200 tread rating can give you over 25k miles if you're not too hard on them....though I've also gotten less than 10k miles out of them but with some track days.

Also for roadracing 11" wide wheel is not very wide for a 335 tire, not sure how that works for drag.

What about brakes? I've seen 16" brakes with 335 tires that look mean but 15" is more than enough for such a light car. Man, the braking g force would make you sick. I've been in a 350z with 14" 6 piston brakes and large DOT race tires when making stops from around 130mph and it's just sickening...you don't even know what's happening until a couple seconds after you're completely stopped.

The wheels you posted don't have a weight but if you're spending all this money I hope you get something lightweight. You may have the power to overcome the weight but it'll help the ride quality with such larger wheels/tires and stiff sport suspension