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Gremlin Traction Woes

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Rebel Machine View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rebel Machine Quote  Post ReplyReply Direct Link To This Post Posted: Oct/28/2020 at 7:24pm
My old Gremlin ran high 11s and never had trouble with traction even before I put Caltracs on it. 60' were 1.7xx but was banging on the pinion snubber. Those wide M/T Pro Radials you have should stick to about anything. Heck, my '69 AMX 60' went 1.424 on 255 60 15 M/T ET Street R DOT radials with 15lbs of pressure.

You said you've got the old slapper bars, maybe someone could take video of the rear when you launch it. Perhaps there's still some spring wrap. The Caltracs will stop that.

The big difference between slapper bars and Caltracs is the Caltracs put leverage at the front spring eye that transfer the weight rearwards. Slapper bars just keep the pinion from hitting the snubber.

-Steve-

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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Oct/28/2020 at 11:21pm
Here is a quick video of the slapper bars in action, they seem to be working as intended:

https://www.youtube.com/watch?v=YYx_JhVWRGE

I had the driveshaft hitting the floor before I installed them.

As you said, it seems the Caltracs offer some additional gains by shifting the instant centre for the rear suspension (I read that on the internet).

Looking at my timeslips from last night, and comparing them to the Wallace calculator, it seems that everything lines up pretty well and there is not much to gain in the 60' if it actually hooks up.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Oct/31/2020 at 6:13pm
I’ve posted in the suspension section as well, I’m trying to find some details or specifications of the small car 4 cylinder front springs? Can’t seem to find anywhere to buy them, only 6 cylinder and V8 springs. Even the 6 cylinder springs seem to be the heavier duty version, that’s what I have in the car now. I’m thinking to get some made if I have to, but can’t do much without specs to work to.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rcabt Quote  Post ReplyReply Direct Link To This Post Posted: Oct/31/2020 at 10:51pm
Have factory 6 springs in mine with 90/10 shocks and they have worked fine for 18 years. Had stock rear suspension, clamps on front part of the spring none on back half, slapper bars with snubber up against spring eye, air shocks with 5 lbs. in right left was 0. pinion angle was 3 negative, ran 1.42 to 1.45 60's with Hoosier quick time pros on a good track. Went to Calvert split leafs, bars and Rancho shocks with same tires, after a lot of tuning, same 60's, but about a thousand dollars lighter. Car left hard on both set-ups. 3000, footbrake, Ati converter, 400 turbo, 4.30 gear.  A lot depends on converter, launch rpm, gearing and track conditions. Have never ran radials so don't know about them, but the Quick time pros work well.11.50 x27 x15.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Nov/01/2020 at 1:04am
Nice to see the back to back comparison of Caltracs to slapper bars, I've got a bit of work to do to get my 60' times down to there.

I'm playing is a bit of a series we have running here at the moment, which requires radial tires, but realistically they should be more than good enough to get the job done at my level.

I've finished off the battery relocation, so hopefully that will help a little. Currently looking at options to get rid of the strut rod bushed up front.

I've butchered my 6 cylinder front springs to get the ride down to a acceptable level, so I sort of have no confidence in them now.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Nov/19/2020 at 7:06am
Feels like I have gone full circle and I am back to square one in more ways than one. ran the car last night and traction was again a massive issue. 5 runs with 60' times of 1.93, 1.73, 1.88, 2.04 and 2.07, so one good run with a lot of rubbish thrown in. By comparison, the previous time out it was 1.77, 1.75, 1.72, 1.68 and 1.71.

Lots of complaints about the track, particularly towards the end of the night. We have a theme night each week with half price entry and last night it was "Euro Night", so we had a whole bunch of late model Euro Trash running and the story was that these cars all running on street tires basically strip off whatever traction compounds has been laid down on the track. 

I didn't help the situation, even though the battery re-location is now complete. With all of my messing around with front springs, I ended up back on my original 350 lbs/in large car springs with the front end stuck up in the air, so that didn't really help at all.

The only positive outcome of the night was that there was a McLaren 720 S there running slower than me.

Anyway, some coilovers for the front are now on order, so hopefully they will help a little when they get here in a couple of months time.

In the meantime, I will put the cut down 6 cylinder small car springs back in and I have purchased some Opentracker Delrin strut rod bushings, which should be here in the next few days.  

 


Edited by WesternRed - Nov/19/2020 at 7:12am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve Obertanec Quote  Post ReplyReply Direct Link To This Post Posted: Nov/20/2020 at 6:56pm
No matter how much time & effort you put into it, track conditions will almost always have you leaving the track scratching your head.

An area I see some economical improvement would be Calvert 9 way adjustable rear shocks. Another thing may be the slapper bars. We have always had good luck with the old Southside Machine bars. They bolt on the rear with the U bolts & bolt to the front of the springs with a square U bolt.      

Real slicks make a world of difference as well. 

Good Luck! 
Steve Obertanec
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Nov/20/2020 at 7:06pm
I currently have Competition Engineering hocks on the back, but haven't actually played with the different settings, maybe I should give that a go.

Home made slapper bars on the back, was thinking to go to Caltracs, but have just spent all of my money on the coilover conversion for the front, so that would be something to revisit in the future.

I have the Summit Racing 3way adjustable shocks on the front at the moment, they are supposed to be 90/10, 80/20 and 70/30, but the human shock dyno suggests the they just have soft medium and hard with the the same rate on bump and rebound, they are set on the softest setting. The front end still feels very stiff to me, hence I'm hoping the coilovers will make a difference. I was having a bounce on a mates Valiant (Dodge Dart) and that is way softer in the front than my Gremlin.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve Obertanec Quote  Post ReplyReply Direct Link To This Post Posted: Nov/20/2020 at 7:15pm
The Southside type bars are way cheaper than the Caltracs. Competition Engineering sells almost the same thing. We buy them cheap at swap meets. We get anything close then modify to fit. Southside is back in business but not making AMC bars anymore. I have been 1.36 60' on this set up. I have a stack of 5 leaf springs, pretty stiff & the Calvert shocks were a million times better than the Summit 3 ways. The  Calvert shocks are 9 way adjustable Rancho shocks & adjust with a knob. They really slow down the separation which tends to pull the rear tires off the ground. Your rear shocks could be too short as well? 
Steve Obertanec
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Nov/20/2020 at 8:19pm
Sounds like I’ll be trying the rear shocks on the hardest setting, nothing to loose there.

There is a video earlier in the thread of the slapper bars in action.

I also have a feeling the rear springs are a bit tired and it seems to sit lower in the drivers side, I have been thinking to swap left with right.


Edited by WesternRed - Nov/20/2020 at 8:22pm
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