Hill climb set-up?

[Sideways]

*Most* people Ive known tend to prefer ss/bb for "bumpier" tracks.  The rationale being that stiffer springs tend to bounce you off the road/really unsettle the car if the corners are really bumpy.  Softer springs will help absorb the bumps without sending you flying, and the bigger bars will help keep you flat.  Be warned- Many have issues going over board with the idea of "staying flat", and use bigger bars than need be-  Stiffening up roll so much that they lose traction.  The weight never fully settles on the wheel(s) it should be, and you lose a good degree of side to side independence when you go too stiff.  For the most part youll want to get the springs as stiff as you "need" them to be, and then use the bars to fine tune the characteristics of the car to handle the way you want.

But as always, take that with a grain of salt.  This is just what ive had some success with (in another car, my Z is still in the process of being set up :\), and those Ive known who do this type of racing.

[tube80z]

http://www.dragonhillclimb.com/records/ (I'm fifth overall all time)

 

http://m.youtube.com/watch?v=zZ8AulTJH7g <- 117.3 sec run

 

Cameron that's a really good time.  You've done an awesome job and I'm sure it feels really good having a time like that.

 

• Now am starting the 6 month off season and planning for the next Dragon hill climb at the end of march. This surface is very abrasive yet I'm struggling for forward traction. My rear tires wear fast and look like cheese gratered on what feels like .1 grit sandpaper asphault. I'm also spinning the tires all the way through third gear at the launch and elsewhere. Do not have nearly as much problem on other tracks. So question is how to maximize forward traction without other unmanagable compromises? As discusses in another thread Im making heim joint rear control arms to help stiffen the rear and reduce friction but what else should I be doing to be better out of the hole? Overall the car turns in well, generally puts down power OK outside of here with these tires, but tends to chase the rear mid corner. I'm confortable where it's at but always looking to go faster.

 

This course looks a lot like Bible Creek that we have here in the PNW.  Since you want to put power down better there's three things I can think of that will help.  The first is more weight on the rear tires.  If you have already moved the battery think about putting it as close to the bumper as you can get it.  Can you fugge the fuel cell back?  Anything else that can be moved or other weight that can come off the front?  Can you move the driver any more towards the rear?  Even though many of those things may slow the car slightly on transition it can help with rear traction and braking.

 

And we somewhat discussed this in the LC thread but I'd use a lower rear RC and an ARB to make the car turn.  While not scientific by any means I've found that a Z will often put power down better when the rear arms are level.  And they turn better when the rear arms are pointing down from the inside towards the tire.  (Lower to higher RC)  If you have adjustable shocks you can try and pull some front rebound to see if that helps but it may cause other issues.

 

And the last thing is more/better tires.  Can you run slicks?  There's a 23x10x15 FA front that potentially would work.  That would get more rubber on the ground and you can get Hoosier or Avons.  Berget recently has had some of the Avons and they are really sticky and hook up well.  I think they are 10 or 11 wide and we've been running them on 10 inch rims.  Those would be a better option if you can run them.  I know almost nothing about Hoosier R6 tires.  I can tell you the A6 is way better for hillclimbs as it heats up very quickly and it grippy.  The problem with Hoosier A6 tires is they fall of a cliff after 20 to 25 runs and buying used you don't always know where they are in the cycle.  Kumhos are better in this respect.  Not as fast but last a lot longer.

 

• Second question is I run used Hoosiers. Last year I ran 275 R15 R6 since I couldnt find any A6's used. I'm still not able to find A6's for next year in that size to fit my 15x10 rims. Other potential option is 245 R17 R6 to fit my street tire 17x9 rims which John Berget has available. So 275/15 R6 or 245/17 A6 if thats the only options available?

I recommend Avon slicks in a similar size.  Tell Bergert the soft ones.

• Last general question, for a bumpy humpy track like a hill where you are going back and forth across the crown and dealing with old asphault is a big spring / little bar or a soft spring / big bar setup better and why?

 

You're better with stiffer springs and less bar.  While both work about the same in corners you'll get a lot more pitch movement with softer springs and that will cause camber changes on the front and rear and will reduce the amount of traction you can use.  On a 240 for hillclimbs that were bumpy we typically used 450 to 550 rear springs with 25 to 50 more on the front.  This was in a car that was 1.5% rear heavy.  Front bar was 1 inch and rear was 0.7 inch.  The one major diff is we used wider rears by 2 inches and the car left the line very hard with little wheel spin.

 

If you're using droop limiters make sure that you have them backed off to where they only hold the spring at full droop.  Don't use any preload.  The other hot ticket for rougher tracks is to interconnect the limiters.  Basically one cable that connects via rollers across the car.  This allows the car to roll a little more freely but in pitch acts like you have stiff springs.  

 

 

Hope this helps,

Cary

[heavy85]

Thanks Cary. Earlier you said "Hillclimbs are probably the most fun thing I have done in a car" and I can fully attest to that. I've spent somewhere north of 40 days competing on variety of midwest track plus autox plus a couple years of w-w karts but nothing compares to a fast hill run.

 

Quick side story. My first event I was thinking maybe break 2 min. Was still on street tires and ended up mid 121s but happy and hooked. Second event switched to the R6's and finally broke the 2 min mark on the last run on Sunday with a 119.4. That felt sooo good. I couldnt believe the feeling at the top if the hill. Now this last event and my third hill climb on same R6 tires. Third run on Saturday I broke into 117 sec almost two seconds faster than ever before. When I reached the top I seriously was scared to death and seriously contemplated putting in on ths trailer for the weekend. I've never felt anything like that driving a car before. I got over it and went three or four more laps in the 117s and each one scared me just about the same but what a rush. Ended up spinning at the top of third gear over a crest trying to break into the 116s. Luckily stayed on pavement and only damage was no longer round tires. These are all 500 miles from home but am actually contemplated running all three events next year despite the distance because its that good.

 

Back to car set-up ......

 

The class I run 'SU' which requires DOT tires otherwise I would be on Avons. I'll have to ask if there is another class I could run on the more readily available slicks but I'm still on a rollbar instead of cage so that may limit classing.

 

Im still on 425/350 springs and do bottom the exhaust ina couple spots. Seems like I may want to go higher but was worried it would make the car less predictable?

 

Seat is all the way back and battery is in the front of the hatch - could move it to the back I guess. With just enough fuel Im at about 51/49 weight distribution and just under 2700 lb.

 

Its been on the list for a while but still dont have droop limiters. The fronts have helper springs and at full droop othe main springs are a good 1 to 1.5 inches slack. Should I get on this already?

Edited October 11, 2013 by heavy85

[tube80z]

Droop limiters are like having much stiffer springs than normal.  So when using them you may find the car reacts a lot quicker and generally will have less roll (the inside can't lift up as much).   For a strut car I think they are a good tool to help control roll and if you get fancy you can also use to control pitch (lift).  It's hard to say if they will make you much faster.  They really show up in quick transitions, like on an autox.  

 

I forgot to ask but can you do more wing or splitter?  More downforce should help find you time.  On the front you have canards and s-flaps you could try (rules allowing).  And on the rear maybe another element or more gurney (serrated ones can be taller and still don't have as much drag).  The toe-link arms will help but if you have urethan on the ARBs I'd look to mount those in a lower friction way.  That will make the car work better.  

 

For springs you can use a lot more rate and shouldn't really see issues.  I'm always surprised at how high a rate I can use before the tires start slipping/skipping.  ARB's seem to be more of an issue on this at least on cold tires.  And speaking of tires you are losing 1 to 2 seconds a mile on R6 versus A6 tires (assuming they are new or in their prime).  

 

Gotta go, wife is not happy

[Phantom]

My only hill climb experience was Cabbage Hill in Northern Idaho and then the Maryhill Loop here in Washington. Both times I had to deal with some seriously tight corners and relatively short straights.  Torque was king and being able to keep the engine in the fat spot of the torque curve helped me do well.  The first time out I was 1st in class and 3rd overall but that was another time.j  The more recent one at Maryhill was just a fun outing but JohnC's words really ring true.  Diminishing radius corners can really ruin your day.

tube80z - you ever run Maryhill?

[tube80z]

I hope to run it next year.  I worked it last year and drove one of the worker trucks.  So I have technically driven the road but not in anger.  It's one I'm really looking forward to.

 

I'd personally love to run the Dragon.  It's lot more open than most of the hills in the PNW.  They have a lot of tight corners and switchbacks.  The closest we had was the now defunct pioneer mountain hillclimb in Montana.  I think the next closest would be Hoopa in Northern California.  

[Phantom]

ZCCW rented the loop this past April for $250 and they joined with tNOrthwest Z club to field about 20 cars.  They let me join in and I had a ball.  It was very informal.  One guy at the top and one at the bottom with radios.  One car at a time ran the hill at about 90 second intervals and then everyone would caravan to the bottom and start over. My son and I both drove my LS1 powered 280Z and had a blast.  I was told the 300ZXTT's were hitting 85 before the cattle guard on the one semi-straight so that became my goal.  On my second run I hit 100 and the gauntlet was down.  I was running Dunlop Direzza 225/50-16's and they held well.  My old KYB's were shot so right after that I got the Techno Toy coil-over set-up with Koni's all the way around. Been a long time since I've had that much fun. Looking forward to doing it again.

I wonder whatever happened to the old Cabbage Hill road in Northern Idaho?  It's part of the original I-95 north of Lewiston where the Winchester grade is now.  It's a great hill climb road. The U of Idaho Sports Car Club - back when it existed - would get releases from the folks that live along the hill and then run it on a Saturday/Sunday.  It was about 4.2 miles of straights and some hairy corners.

[heavy85]

So control arms are almost done. Plan is to:

 

- Lower the splitter as its effective at higher speeds but is just too high.

- Finish modified stock arms w/ toe link and heims

- Swap from 3.7 to 3.56 diff as Im on the limiter at the finish and should be able to eliminate at least one 3-4 shift

- Install droop limiters on the front

- MAYBE up spring rates

 

Need to figure out tires in case I cant find 275/35-15 A6's.

 

Next round of questions. The first Dragon next year is in March. This means much cooler temps maybe in the 40s or 50's. Other than trying to preserve tire temps any other considerations? Also when I swap gears I'll have the diff out. Should I keep the OBX gear type or go back to the Nissan clutch type? I've been happy with the OBX but I havent played with R-comps ... ever before these last couple events.

Edited October 19, 2013 by heavy85

[heavy85]

My take on modified stock control arms.

 

 

Got some 500 lb springs for the front and going to move the 425's to the rear.  Front droop limiters installed. I'm debating splurging on some new A6's It's going to be a long offseason ....

Edited November 1, 2013 by heavy85

[RebekahsZ]

Can you show your front droop limiter pics?

[RebekahsZ]

Can you show your front droop limiter pics?

 

Wait till spring to get your A6s and make the vendor tell you the production/date codes and buy his newest stuff if you can find one that helpful. They gas off really quick. Storage conditions make a big difference. You might loose some grip just from letting them lay around all winter.

[tube80z]

My take on modified stock control arms.

 

 

Got some 500 lb springs for the front and going to move the 425's to the rear.  Front droop limiters installed. I'm debating splurging on some new A6's It's going to be a long offseason ....

 

Those look good to me.  

 

In your other post you were asking about raising tire temps.  There are a number of things you can do.  If you can drive the car before you run accelerating quickly and then standing on the brakes.  This will help get the core temp up.  For setup if you increase spring rate it will work the tires harder and so will raising the car (if you can raise the RCs on both ends is even better).  And you can sipe the tires.  That will help them to get to temp a lot quicker but you can overdo it.  You can also increase your damping ratio but that would require new or revalved shocks and may not be as easy as the others.

 

Keep up the great work,

Cary

[heavy85]

Can you show your front droop limiter pics?

[tube80z]

I like the sway bar bracket.  That's a nice way to do that.  

[RebekahsZ]

Curious to see how that droop strap mounting holds up just pinned to the sheet metal like that. Please comment on that over time.

[tube80z]

Curious to see how that droop strap mounting holds up just pinned to the sheet metal like that. Please comment on that over time.

 

I had mine on the car for 2 years with no problems.  As long as you're not pulling the sheet metal so it bends it's fine.  I ran this front and rear with turnbuckles to adjust the amount of droop.  I originally considered redoing them to be a mechanical stop on the opposite leg of the ARB but this worked well enough and there's always something else you can do when things work on a race car.

[JMortensen]

If the bolts were just a little higher they'd catch the thick insert at the top of the tower.

[heavy85]

The upper bolt goes through a doubler plate welded to the inside of the tower used for the welded strut tower braces. It aint goin anywhere.

[RebekahsZ]

Please don't think I was being critical. I just want to learn. I made my droop limiters WAY too complicated and am jealous of how clean yours looks. Ah, a doubler plate. That's the difference. My first go at it bent the crap out of my sheet metal.

Edited November 7, 2013 by RebekahsZ

[tube80z]

Mine were in the same location but held with a couple large fender washers.  And as Jon mentions if you go higher you can hook into the doubled sheet metal, which probably would be better if you don't have reinforcement.  I did the same in the rear and also saw no problems.