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 Post subject: Caltrac adjustments
PostPosted: Mon May 08, 2006 1:11 pm 
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Joined: Wed Nov 16, 2005 11:05 am
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Location: PA
This is my understanding. In order of hardest to softest hit to the tires:

HARDEST HIT:
Top hole, 0 preload (gap)
Top hole, 1/2 turn preload
Top hole, 1 turn preload
.
.
.
SOFTEST HIT:
Bottom hole, 0 preload (gap)
Bottom hole, 1/2 turn preload
Bottom hole, 1 turn preload
.
.
.

I'm running the bottom hole with 1/2 turn preload each side and the car doesn't spin at all. My 60fts are 1.70x running 12.40s on the motor. I can't run the bars in the top hole due to the transfer link contacting the leaf spring. I'm running -4* static pinion angle and have 2" lowering blocks. Would playing around with preload be able to get me consistent 1.6s if the car is hooking already???


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PostPosted: Mon May 08, 2006 2:02 pm 
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Nope, if it's hooked you're not likely going to see much playing with the cal-tracs. Just put the bigger pills in it :twisted:


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 Post subject:
PostPosted: Mon May 08, 2006 10:57 pm 
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Location: California gold country
If you took out the lowering block, do you think the link bar would still hit the spring?
Are you running multi leafs? or the Caltrac split leafs?

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 Post subject:
PostPosted: Tue May 09, 2006 1:24 pm 
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JohnDougherty wrote:If you took out the lowering block, do you think the link bar would still hit the spring?
Are you running multi leafs? or the Caltrac split leafs?


I'm running stock multileaf springs. I ran the bar in the top hole last season, but I added a set of 4* pinion shims to set my pinion angle and that's caused the bar to contact the spring.


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 Post subject:
PostPosted: Tue May 09, 2006 6:44 pm 
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Location: Caney, Ks
Hey guys

I am running Cal tracs too. But for some reason I started off in the top hole. The last time I tested at Mokan I had Goodyears 29.0/12.0/15 slicks with a D-3 Compound(which is the hardest compound). It was spinning right off the line on the footbrake and hooking when I used the transbrake until my front tires came back to the ground about 5 or so foot out then I started spinning again. So I called calvert racing and told me to check my front travel and I only had maybe 2in or so of front end travel. So I bought moroso trick springs for the front and gain ALOT of travel, which put my nose in the ground,(to get a idea where the front is sitting- the top of the tire is pretty much even with the bottom part of the front finder and I have 26" tall tires on it and the back is up higher) also put a set of 90/10 shocks on the front. Now I have bought a set of MT28.0/10.5/15 which are alot softer. So should I drop the cal tracs in the bottom hole and go from there? Let me know what you think of all this.

Adam


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 Post subject:
PostPosted: Tue May 09, 2006 8:43 pm 
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I would leave the caltrac's where they were before you made the front end changes. Don't change to many things with traction especially, cause you'll lose track of what worked and what didn't.

Make a few passes and then see where you are, then if need be, move the caltracs around or play with shocks, but not all at once unless you keep VERY good notes on it, and even then I wouldnt suggest it.

Scott

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Best so far of 10.51 @ 131mph with a best so far 60' /1.46


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 Post subject:
PostPosted: Wed May 10, 2006 2:52 pm 
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Scott's got a good point of not changing too many things at once. Did you ever drop the rear end back down now that you've switched to the shorter tires? How much shock travel do you have when the car is sitting at rest?

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 Post subject:
PostPosted: Wed May 10, 2006 3:09 pm 
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Well I was fixing to mount up the new 28's before I go test this friday. How much should I lower the back? Are you wanting to know the front shock travel or the back? And what is the best way to check it?

Thanks
Adam


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 Post subject:
PostPosted: Wed May 10, 2006 3:33 pm 
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It sounds like you have plenty on the front now, I was wondering about on the back. I would want it close to stock ride height if it will clear the tires. The thing is if the rear is jacked up some it's going to reduce the amount of travel your rear shocks have unless you've put extensions on the shocks (stock type shock mounts). On a leaf spring/cal trac type car you want the majority of your shock travel available in extension, so at rest only about an inch or so of the shock rod should be showing.

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 Post subject:
PostPosted: Wed May 10, 2006 5:41 pm 
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I dont have extensions on the back and I have alot more shock showing than a inch. Can you explain what the advantage and the cause of only haveing 1 inch or so showing of the shock on a stock multi leaf caltrac setup, because I am not very knowledgeable on this topic. Also, I have Comp. Eng. 3 ways on the back, and I was wondering what setting I should have them at and Why. Sorry for all the questions.. I am a young one that just wants to learn :D

Thanks
Adam


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 Post subject:
PostPosted: Wed May 10, 2006 11:46 pm 
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Location: upland, ca
well that doesnt really make sense, we are running the caltracs in the lower hole and a 3/16 gap and the car 60fts the hardest with this setup. my only reasoning is why this works is the pinion angle is set with the caltracs against the springs, so i may be shocking the tires harder this way. we ran the car last week at irwidale and it 60ft time was a 1.38.

on my brother superstocker we made our own caltrac style suspension device with a mount point much lower than the catracs and the bracket we made for the axle tube mount was much lower as well, essentially makeing a poor mans 4 link, this was on a 68 camaro with a 30x9 radial slick we saw a best 60ft time of 1.32.

so which way should you go? well we had rented a track nearby for a day with some freinds and worked on our setup, we made 30 hits and didnt make a full pass since all we were concerned about is 60ft times. we changed hole postions, preload, to a gap etc till we found what worked for our car.

also we found out that the front spring mounts in ovas are different than camaros, the camaro mounts make the car sit lower but provide a not so good postion for instant cernter, by making nova monts fit we were able to get the instant center where we wanted it. we used astro van fiberglass mono leafs in the rear, we had to machine our own front eye mounts to bolt to the spring, but they were so stiff and the price was unbeatable. i lost all my pics of the setup when my computer crashed, but next race i see the guy we sold the susp[ension too i'll snap some pics and post em.

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 Post subject:
PostPosted: Wed May 10, 2006 11:51 pm 
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Location: upland, ca
heres a pic of the camaro at vegas wehre it ran it best ever of 10.51 at 129 with a 60ft of 1.32 with our home made version of caltracs

Image


this is the nova i tune on that runs caltrac bars and leafs that 60 ft a 1.38 last week, best run to date is a 10.39 at 134.


Image


also the camaro was a 468 hp 355cid small blcok, nova is a 383 but we never dyno'd it, but im putting some better fully comp cnc ported afr 227 heads on it for next race, heads on it now are unported dart pro1's.

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 Post subject:
PostPosted: Thu May 11, 2006 6:33 am 
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Adam - these leaf spring cars, cal-tracs or slapper bars will almost always want to extend the shock at launch. I've never seen one that squats or compresses the shocks at launch. Depending on how much power, gear, tire and what shocks are on the car will determine how much it will extend the shocks.

A frequent problem people run into is that the car will run out of shock travel in extension (rebound) at launch which will break the tires loose at that point. So if you've got say 5" travel shocks and at rest the car has the shocks extended 2", you only will have 3" of extension available and the car may use all of that up when it launches.

Sixpack - how much height difference is there between the Nova and Camaro spring mounts?


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 Post subject:
PostPosted: Thu May 11, 2006 6:54 am 
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I'd love to get John or Travis from Calvert on here to discuss this with us but I don't know if they have the time. For the sake of argument, let's just pretend that all the caltrac stuff doesn't change the instant center at all - yes, I know that's what the idea is but let's look at this a different way.

Say that all the adjustments you have available are more of a dampener of sorts for rear end rotation. In that sense, upper hole has less leverage on the lever and will not be able to bend the spring as easy - that causes less spring deflection at the hit which has to be transfered to the tire - more initial hit. More preload does the same thing, the rear end will not rotate as much as it does if you have zero or a gap. So if you look at it this way,

Soft inital hit - lower hole, zero preload
Harder initial hit - lower hole, preloaded
Even Harder initial hit - upper hole zero preload
Hardest initial hit - upper hole with preload

With the bars in the upper hole there is going to be less housing rotation at launch, which gets transfered into the tire hitting it more violently.

Of course that throws all the Instant center change out the window, but it does make sense to me at least in regards to housing rotation and how it dampens the hit. Personally I don't think we're changing the instant center any with where that front bar attaches, but we are changing how much leverage the arm has against the spring.

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 Post subject:
PostPosted: Thu May 11, 2006 10:02 am 
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So how many truth or value do you guys put into a set of front end travel limiters? Right now I have none on my nova and when it launchs, it doesnt pull the tires quite yet, but I'm lookin at the sky for good portion of the run...

advice/ideas??

Scott

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'70 Nova
434 small block
Best so far of 10.51 @ 131mph with a best so far 60' /1.46


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