How did the old guys launch?

[Jim Ratto]

Died with the combo you're going to build and the amount of hp you're expecting you can run with a lightened flywheel i bet.
I would go with a smaller diameter tire like the 185/195 and put a superdiff at least in your box if you wanna launch good.

Otherwise on the 12th of april at you dvk meeting i can give you some pointers of how i do it

sorry to get off topic, but Sheep ran a motor very similar to what Dieds will be running.....really bad tempered 1914 that kept within a fender of my 2276 out on our private 1/4 mile. Anyway, Sheep ran 185 radials, stock height rear axle, with Z bar, and a Crown 6lb aluminum flywheel. Sheep's car didn't bog down when he dropped the hammer, it would spin the tires and then extend front shocks up.

[Diederick/DVK]

He never broke his 'box?
So, how heavy should my flywheel be, ideally?

[Jim Ratto]

He never broke his 'box?
So, how heavy should my flywheel be, ideally?

I'd use 12.5lb

No sheep had a built trans in his red rider.

[Bewitched666]

2x that Died and superdiff your box

[Diederick/DVK]

yeah, but when you run a superdiff, don't you also have to run HD side covers? etc etc.

[Jim Ratto]

yeah, but when you run a superdiff, don't you also have to run HD side covers? etc etc.

nope.... you don't have to

[Bewitched666]

Like Jim said Died,not necessarily.

[Diederick/DVK]

Mmh, sounds interesting.
Still, I have no idea how to swap a diff! I'm afraid I'll have to outsource it...

[Bewitched666]

Its like brushing your teeth Died,haha
Only thing is when you buy a superdiff it comes with 2 spider gears and you need 4 so need to look for 2.
There is one for sale on the keversite for 150 euros including all 4 spider gears.

Takes some work to install it but its pretty straight forward

[Prowagen]

Wow this is a great thread for us rookies!

I never knew tire size was as critical, I always thought the wider the better for traction!

So I presume the trouble with bigger tyres is the width of the tread pattern giving you too much grip? Or is it also to do with the overall height of the tire? Say what would happen if you ran a non cal look tire that was 205 but a low profile like a 45?

Cheers,
Rob.

[Cheesepanzer]

Great thread! 

As I remember back to my early passes down OCIR I don't remember the track surface being "treated" like tracks are today.  I don't think they had special tractors with sprayers running a patch of VHT down the lanes, did they?

I "grew up" on the e-brake preloading approach and used it successfully to run 12's and not break gearboxes or CV's.  Everyone now seems to have moved to linelok's combined with 2-steps.  So to keep up with the Jones's I did this too.  It was a hard transition to go from "preload and rev" to "mat it and release the switch."   

I have a few slow 60 ft times due to not releasing the button.  DOH!

[Jim Ratto]

our little low dollar '66 drag sedan had line lock.
SODA sheared teeth off 4.37 ring gear after about 4 passes

we showed ring gear to Jim K at Der Trans and he knew instantly "using linelock huh?"

[Bewitched666]

I run with a line lock and never had problems with it,also preloaded the car.

In the pro stocker there is a 2stepline locker.
@prowagon i think it has to do with the tire height rather then width.Width is traction

[Prowagen]

@prowagon i think it has to do with the tire height rather then width.Width is traction

So if you ran a wide but low profile tire this would be the same as running a 165/185 but you would have better traction surely?

Rob.

[Diederick/DVK]

yeah, so i guess what you're asking is... width or height? do we want a 165 tyre cos of its width or the 2cm it is shorter?

[Bewitched666]

prowagen in some way yes,only you have to look at your hp output too.
Dont expet a 1679 to run 12 inch wide slicks and launch like the space shuttle

Its a combo you have to try,there is no fast rule of that tire width and height will work for that hp

[Jon]

Super interesting thread!
The COMBO, thats a magical thing, and so hard to figure out on your own...

But there are a couple of things I'm a bit uncertain about after reading this thread...
Sarge talks about narrow tires to prevent breakages in his first post... then it sort of drifts over to the width of the tires, but aren't you really talking about the weight of the rotating mass, it seems like it, as flywheels comes into play?
hmmm
Narrow tires saves gearboxes
Lighter wheels helps acceleration
Heavy flywheel helps getting heavy car moving
Spinning wheels compensates for a too "tall" gearbox (or to weak engine )

uhh or something... it's getting late

[Bewitched666]

I'm no scientist but it all depends on alot of factors,i do as i'm told from guys who already have years of racing under their belt.

The combo of your engine
combo of your gearbox
tires
weight of the car
condition of the strip,concrete in the launch part,traction compound etc
 etc

[jamiep_jamiep]

Guys, I don't want this thread to die as I NEED TO LEARN!!!

So, the smaller tyres, is if for the shorter side wall height or for the lower width? I appreciate that nowdays most people are running larger motors than back in the day, and so are a little less likeley to bog - so what would be a good compromise tyre size taking into account all of the above, trying to optimise tread width, weight, and sidewall height?

thansk for the great info!

[Lids]

i understand that a stock flywheel will help keep the revs, which is why it launches better.

[Neil Davies]

i understand that a stock flywheel will help keep the revs, which is why it launches better.

But if it bogs, it really bogs!

[EspenX]

Most important to use your hand brake to "load" the gearbox before blasting off the line (let the clutch out a bit while your staged with the hand brake pulled up a bit and your thumb holding down the button...you'll feel the car pull down in back).  Running 165 X 15's, I remember 20lbs of air pressure and coming off the line about 5000 rpm, seeing the tach jump to 7000 (tire spin) then lowering a few hundred rpm (grab) before climbing back to 7000 and the shift to second gear.  I know those 205/70's look cool and all, but I feel you'd be more prone to trans breakage with your engine size running big tires.  Just my $.02...there are lots of other opinions here, I'm sure!  Good luck

Ohh, please bring this thread back to life, it's one of my absolute favorites Thank you so much Sarge, for taking the time to explain it step by step in the post above. It is probably common knowledge for some, but for rookies like me, it seems like a nugget of gold If anyone have more old school tips like that, please post them here!

[Sarge]

Most important to use your hand brake to "load" the gearbox before blasting off the line (let the clutch out a bit while your staged with the hand brake pulled up a bit and your thumb holding down the button...you'll feel the car pull down in back).  Running 165 X 15's, I remember 20lbs of air pressure and coming off the line about 5000 rpm, seeing the tach jump to 7000 (tire spin) then lowering a few hundred rpm (grab) before climbing back to 7000 and the shift to second gear.  I know those 205/70's look cool and all, but I feel you'd be more prone to trans breakage with your engine size running big tires.  Just my $.02...there are lots of other opinions here, I'm sure!  Good luck

Ohh, please bring this thread back to life, it's one of my absolute favorites Thank you so much Sarge, for taking the time to explain it step by step in the post above. It is probably common knowledge for some, but for rookies like me, it seems like a nugget of gold If anyone have more old school tips like that, please post them here!

Speed secrets cost BEER

[John Rayburn]

You used to be a steal, Sarge. Now you're getting way too expensive!

[ian c]

I "grew up" on the e-brake preloading approach and used it successfully to run 12's and not break gearboxes or CV's.  Everyone now seems to have moved to linelok's combined with 2-steps.  So to keep up with the Jones's I did this too.  It was a hard transition to go from "preload and rev" to "mat it and release the switch."   

I have a few slow 60 ft times due to not releasing the button.  DOH!

if you wire a switch to your clutch you dont have to worry about the button .
if you wire it to your handbrake , you can launch just like you used too !!!

[Neil Davies]

I "grew up" on the e-brake preloading approach and used it successfully to run 12's and not break gearboxes or CV's.  Everyone now seems to have moved to linelok's combined with 2-steps.  So to keep up with the Jones's I did this too.  It was a hard transition to go from "preload and rev" to "mat it and release the switch."   

I have a few slow 60 ft times due to not releasing the button.  DOH!

if you wire a switch to your clutch you dont have to worry about the button .
if you wire it to your handbrake , you can launch just like you used too !!!

I did that - had a bar welded into the back of the handbrake that would operate a microswitch for the 2-step. Let off the handbrake and the MSD would go onto the higher rev limit. I added a switch onto the dash to switch the 2 step on to limit burn-out RPMs and did forget to turn that off a few times though...

[ian c]

i'm going with 2-step and line lock on the clutch switch
hidden switch on the dash to activate it
modifield "fuel" light in a 3-way motometer guage to let me know its activated !!!

[Sarge]

Wires, switches, line-lock, clutch switch, 2-step, MSD..., my head's spinnin'

[GreenTom]

hehe shouldn't it be "less is more"

Darge don't you like wires and stuff

[Sarge]

Serge, don't you like wires and stuff

Only if they involve blowing things up