620 Land Speed Record

[distributorguy]

2.73 S10 rear axle acquired.  Now all I need to do is change out the wheels and install C-clip eliminators and disc brakes.  And cut off all the brackets and weld on perches and...

[Stoffregen Motorsports]

Nice! Does the eliminator require new axle shafts? If so, get custom and have them drilled to 6 on 5.5.

[distributorguy]

C-clip eliminators are pressed into the axle tube, with a press-fit bearing on the axles so new axles are not required, although at $300, i can get finer spline axles to use with a mini-spool.  I'll evaluate the diff when I have time to tear it apart.  All the teeth are intact, but will likely require bearings, plus I like to make a solid pinion spacer for these so swapping gear sets becomes much easier than using the crush sleeve.  

 

I'll have to figure out disc brakes with a 6 x 5.5 rear however.  That'll get interesting.  Deep custom.  Lol.  With all the effort required, I'm still hunting for a stronger 9".  

[wayno]

I am curious, so the salt being rough and wet, I am focusing on the rough and tire slippage, would a larger/taller tire make it less rough and therefore slip less?

I was thinking like wash boarding on dirt roads, a larger tire rides smoother while very small tires like on a Mini  make it very rough.

[Lockleaf]

Early 90s pathfinder has a disc break option.

 

Honda passport and late model Chevy truck are other options that come to mind for 6lug disc. Any Toyota options?

[Stoffregen Motorsports]

Re-drill the stock S10 brake rotors for 6 lug.

[distributorguy]

I am curious, so the salt being rough and wet, I am focusing on the rough and tire slippage, would a larger/taller tire make it less rough and therefore slip less?

I was thinking like wash boarding on dirt roads, a larger tire rides smoother while very small tires like on a Mini  make it very rough.

 

Yes, we were running 1" shorter tires on the rear, and will now run the 25" front tires on front and rear next year.  I already have them.  The 24" tires had a wider tread, so there was a better contact patch.  We'll give that up for lower gearing and see how it goes.  I'm not sure we can go any bigger?  

 

I may find a way to fit Nissan rear disc brakes and rotors to the S10 axle, just for the fun of it.  I like the idea of making my own caliper brackets.  I've done it MANY times.  Why waste $100 in shop  time time drilling a $30 rotor?  

[datzenmike]

Do you really need (disc) brakes at all? Not going 400 mph, wouldn't a good e brake and wind resistance do? or just roll to a stop.

[distributorguy]

We will be running NO front brakes to eliminate drag, so yes, rear disc will be required.  Drums drag more than disc.  Rolling to a stop from only 110 actually takes quite a while, even with downshifts.  We only get 1 mile to do so, and turn out safely on the shortest course.  The first half mile flies by very, very fast. This isn't a freeway.  Keep in mind the total lack of traction, adrenaline at play, and a very rough course.  

[Stoffregen Motorsports]

And you don't need a parking brake so your brake options just opened up dramatically.

[distributorguy]

If I recall, I may have a pair of small Wilwood calipers new in the box hidden in my personal garage.  At least one anyway.  Maybe I'll use those on custom brackets?  

[Stoffregen Motorsports]

Why not? When you say small, you're talking about the minilights? Hopefully you've got at least four piston calipers if they're going to be your only brakes.

[datzenmike]

You said the salt was wet? Two things. If slushy, the rolling resistance is increased and it is slippery. Increased rolling resistance would help you slow down. Add engine compression and with being very slippery, you wouldn't want (or need) too much braking.

[Stoffregen Motorsports]

I vote for a parachute!

[datzenmike]

...and e brake.

[distributorguy]

Parachutes are required over 175 mph.  

If the course wash slushy, they'd either move it or stop racing.  Its hard to describe the conditions without being there to experience it.  Its like hard packed snow over wet snow.  In the afternoon, the water comes up to the surface so its more slippery hard packed snow.  In the cool and breezy evening, the water evaporates and/or recedes and the surface dries out.  

 

Yes, I need enough braking to stop a 4K lb. truck - but not lock up on a slippery surface.  If (when) we get to breaking 150, we add a chute.  One of the things I learned at Bonneville this year was how to pack a chute.  Cool stuff.  

[datzenmike]

Drove my old VW on a frozen lake. Doors and fenders cut off. Top speed? 45. Any faster the engine (32hp?) was able to over power the rear wheels and no amount of steering would keep it going straight and around and around it went. Sounds similar. Can you increase traction with more aggressive tread tires? Maybe narrower ones in front? Like pizza cutters?

[distributorguy]

We have pizza cutters on all 4 corners.  Basically motorcycle tires - Goodyear Front Runners.  Tread won't help.  Weight helps.  If you keep your center of gravity forward of your center of pressure (using ballast) you can gain weight and never spin out (like Burt Munro's explanation of throwing a rear-weighted dart).  For those who don't know, that's a "World's Fastest Indian" reference.  

Frontal air pressure versus traction is quite a thing.  Mad science.  Many equations I don't understand, but I'm decent at interpreting principles and experimenting.  The key is to go as light as possible without losing an unacceptable amount of traction.  And keep down-force on the drive wheels.  

[datzenmike]

I like Hopkins.

 

Can you deflect more wind up and over the cab by lowering the front? and back?

[Stoffregen Motorsports]

If you keep your center of gravity forward of your center of pressure (using ballast) you can gain weight and never spin out (like Burt Munro's explanation of throwing a rear-weighted dart).  For those who don't know, that's a "World's Fastest Indian" reference.  

 

I can picture the cigar and toothpick now.

[datzenmike]

Sometimes a cigar .... is just a cigar.

[G-Duax]

How did this go from the salt, to Monica Lewinsky ?

[distributorguy]

LOL!!!!

 

The truck is as slammed as far as I can take it without removing the inner fenders (they're already heavily modified - so much that I had to modify the clutch pedal), and the back needs a little rake for down force on the bed cover - maybe more than we have?   At this point, we can't go lower without removing the crossmember under the front of the oil pan, which I'd be afraid would open the oil pan to hitting the course more than it already can.  

 

I can deflect more air over the cab by stretching the hood scoop to the absolute legal height limit of 8", and extend it closer to the windshield.  That's the only allowable aero advantage we can take in production class.  I was able to mount wind tells on the hood scoop opening to see that air is in fact entering the scoop at the windshield.  Probably too much.  I will restrict the hood opening at the air cleaner to prevent more air from entering the engine bay.  I cannot push air from the radiator out the hole in the hood, as that's considered "venting" - illegal in production class for aero reasons.    Picture a late model Lotus to see how beneficial it could be.  

 

We have tight steering at 110, so I think front downforce is ample.  We are VERY close to 50/50 weight distribution.  Maybe even a little rear biased at this point.  That's the next step before disassembly - back on the corner scales.  

[distributorguy]

Maybe a dumb question, but given that traction doesn't exist on salt, is there ANY benefit to upgrading from 26 spline axles to 30's?  I can't fathom it would matter.  Either way, I have a GM 10-bolt diff and a 7.5" ring gear.  Weak, but it only sees 200-ish hp and very limited traction.  

[Ooph!]

Just thinking about your lack of traction at speed. If you have downforce on the front you should need less weight percentage statically on the front. My logic being as you move along the air pressure is forcing the front of the truck downward giving the steering wheels traction.

But in the rear it's a truck and probably have very little downforce if any.

 My experience is Dirt track racing, and generally use a larger rear weight percentage, mostly for traction on exit (on the throttle)

 54% rear is a very common number, if you watch these cars ( dirt modified and Late models ) depending on adjustments and track conditions the left front wheel can sometimes come off the ground, although not desired it does indicate how much force and weight is being transferred to the rear and yet there is still wheel spin.