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Thread: traction
[' This thread is 2 pages long: (1)
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micah
Hauling
Posts: 167
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posted January 09, 2008 04:23 PM |
 Edited By: micah on 9 Jan 2008 16:25 |
traction
I need some guidance here again,,,,,how to get traction,,,,,too low for bars, yet i've seen some that look like they go on top the leaves. I know about the bag with water in the bed but i'm not interested in adding weight unless it works really well. Love to hear from you guys,,,,thanks again,,,,will send add a pic onto my pics of the weatherstripping.
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Brad
Rotorhead
Posts: 1672
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posted January 09, 2008 07:18 PM |
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composite leaf spring reduce axle wrap and therefore wheel hop. and reduce lateral axel movement. and weigh 60%less.
http://flex-a-form.com
besides that it's a 4-link
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datsunrides
Revvin Up
Posts: 58
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posted January 09, 2008 07:27 PM |
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Brad
Rotorhead
Posts: 1672
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posted January 10, 2008 09:20 AM |
Edited By: Brad on 10 Jan 2008 09:21
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Yes but it adds more weight and reduces ground clearance. And are designed for straight line performance only. They screw up handeling, no more corner carving because they load up the leafs real funny.
The composite springs are a better package. People remove their cal-tracs or other anti-wrap devices like this one, once composite leaf springs are installed.
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-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge
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datsunrides
Revvin Up
Posts: 58
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posted January 10, 2008 08:18 PM |
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Maybe something along the lines of an adjustable pinion snubber? That may help a bit with axle wrap.
Mark
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Brad
Rotorhead
Posts: 1672
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posted January 10, 2008 09:05 PM |
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I used leaf spring clamps on the front half of the stock leafs. Eleven bucks each. Autozone and Pep Boys carry them.
But again, composite leafs are the way to go.
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micah
Hauling
Posts: 167
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posted January 11, 2008 03:36 PM |
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thanks so much guys, looks like I'm going with composite leaf springs, thanks again!!
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sparky
Redlining
Posts: 299
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posted January 11, 2008 07:57 PM |
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Maybe if we pool together we can get a discount on a group buy for the composite leafs. I may be interested depending on price.
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Brad
Rotorhead
Posts: 1672
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posted January 15, 2008 01:32 PM |
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i'm down to buy a set
but it would have to meet certain specs since my suspension is tuned for 500lb front coils and TORSEN. and handles well.
i'm looking for composite leafs that are the same rate as mine. stock but with 2nd longest leaf removed. haven't measured the rate yet but stock is 312lb. so i think mine are about 240lb.
and need it to lower the repu about 1" more than what i have right now. overall i think that would make it approximately 3" lower than stock.
plus anyone know where i can get a 17mm grade 10 bolt with 5" shaft length so i can have it gundrilled and zerk fitted to become greaseable?
____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge
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bwaits
Hauling
Posts: 119
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posted January 17, 2008 10:08 AM |
Edited By: bwaits on 17 Jan 2008 10:08
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quote:
plus anyone know where i can get a 17mm grade 10 bolt with 5" shaft length so i can have it gundrilled and zerk fitted to become greaseable?
5" length under the head or 5" non threaded section under the head?
-billy
____________
ACT . Accufab . AEM . APEXi . AutoMeter . B&B . B&M . BBK . BORLA . Bosai . Brembo. Center Force . Earl’s . Eibach . Energy Suspension . Fluidyne . Goodridge . Greddy . HKS . INJEN . Innovate Motorsports . INTRAX . K&N . KONI . KYB . Magnacore . MOMO . MSD . NGK . NOLOGY . NOS . NX . Pace Setter . Power Slot . Prothane . ReSpeed . Rotora . Sparco . Suspension Techniques . Tanabe . Tokico . TurboNetics . Unorthodox Racing
ReSpeed Online Catalog
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Brad
Rotorhead
Posts: 1672
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posted January 17, 2008 11:17 AM |
Edited By: Brad on 17 Jan 2008 11:55
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quote:
quote:
plus anyone know where i can get a 17mm grade 10 bolt with 5" shaft length so i can have it gundrilled and zerk fitted to become greaseable?
5" length under the head or 5" non threaded section under the head?
-billy
Thanks for the reply Billy
5" under the head. 3" to 3.25" non threaded section under the head.
Stock length is 4" under the head but I need more room for:
-poly bushings that do not compress as much as rubber
-thicker shackles for less lateral deflection
-run a thicker, wider washer under the nut
-Nylox nut - if you know where to get one of these this size that would be great
For micah, sparky and anyone else considering composite leafs, there are more benefits not mentioned already:
-You can design the composite leaf dearched, to lower the truck instead of using blocks. Which reduces unsprung weight from not using blocks, and you can use shorter u-bolts to reduce unsprung weight too.
-dearching any leaf also reduces roll understeer
-dearching any leaf also reduces the rear roll center for more consistant handeling
-blocks give the axle tube more leverage to twist under acceleration, and thus increase axle-wrap
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-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge
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2wankel
Hauling
Posts: 133
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posted January 31, 2008 07:14 AM |
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Brad,
I just like to say thanks for the time and research you have put into researching suspension upgrades for the REPU.
Since you are ahead of us in this department, maybe in this post or a new thread we can have a list of your suspension mods and your goals for your truck. I think I would like to follow in your foot steps in upgrading the suspension.
My goals for my truck is...
I want my truck setup low and be able to hang in there with other sports cars in the twisties. Its funny, ever since I bought the truck I'm getting teased alot about how heavy it is and that it wont keep up other sports cars. I would like to prove them wrong; although, I have to admit that I cant possibly destroy new cars with current suspension technology, but I would love to give them a run for their money and make them think twice about challenging a REPU.
Ultimatly I would like to make the REPU the Japanese version of the Syclone.
Thanks,
kEn
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VMRC Website
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Brad
Rotorhead
Posts: 1672
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posted January 31, 2008 12:18 PM |
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Thanks for the compliment Ken. Nothing I'm doing is earth-shattering secret technology, just the usual stuff. I have 3 books on suspension design and tuning and I like to read. Here we go.
Front Suspension:
My coilovers for adjustable ride height. With 500lb spring (stock is 512). Search this forum for thead with pics and price if interested.
Bilstein Heavy Duty shock from 67-76 Camaro. Oval the bolt holes inward 1mm each hole with dremel.
1 1/8" front swaybar. Addco makes these and Quickor Suspension finally rememberd how to make it. (They used to make it, but then shipped my friend Courier versions. 3rd time they got it right).
All new MOOG bushings, balljoints, tie-rods with greaseable zerk fittings make it steer and respond a lot easier.
Don't lower the front so much that the lower a-arm points up. Screws up roll center and geometry. Keep it parallel to ground.
Toe: 1/16" toe in is okay but to autocross you really need some toe out for it to dive into corner. Which compromises braking. Stock is 1/4" toe in!!!!! to increase understeer or reduce all that rear supension oversteer your pick.
The upper a-arm shaft has threaded ends to allow you to move that upper a-arm forward or back. To adjust caster. Crank it as far rearward as possible to get max caster. These area pain to move - I removed the upper a-arms entirely and used a 1/2" breaker bar with 3 foot pipe cheater bar.
Rear suspension:
Not much you can do here, it's leaf springs. I removed 2nd longest leaf to reduce spring rate AND lower about 1", AND it dearched spring slightly to reduce roll steer.
1" solid STEEL block. Never use aluminum blocks - they crack. Steel all the way and DJM suspension makes SOLID steel blocks that bolt TO the leaf pack via new centerbolt. Heavy but durable.
Buy some leaf spring CLAMPS you can find them at auto parts stores sometimes. It's a big wide u-bolt with a thick wide plate. Clamp together the the leaf pack in front of the axle - it increases fore-aft location of the axle, and reduces axle wrap: hop-hop-hop.
Removed 80lb rear bumper - less oversteer, also less rotation. Raised the rear of the truck about 3/4 inch though!
New stocker rubber leaf and shackle bushings. The right shackle did bind up on me so I bought some poly bushings - just need to make greaseable shackle bolts and new, thicker 3/8" thick shackles to use them.
http://www.superpro.com.au/home.html SPF0311K is part#.
Composite leafs would go a long way here. Have them made de-arched to lower the truck right w/o blocks. Save unsprung weight there, plus composite weights 60% less than steel. De-arching also reduces roll understeer. Monoleaf provides better lateral axel location and reduces axle wrap. And u can use longer shackles to raise back up the rear if needed, which ALSO reduces the change in rear leaf height during cornering -- which really messes things up.
4wheelpartswarehouse.com has u-bolts that work and great thick washers and Nylox nuts. I posted part number here earlier. Traditional lock washers cannot handle the tightening torque the FSM suggests.
There are long steel plates under the spring plates. That tie the bottom of u-bolts together. They're prolly bent or warped - straighten them.
Good luck. I"m just trying to get REPU to handle as well as a 1st gen. And be a sleeper.
____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge
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Klaus44
Redlining
Posts: 365
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posted January 31, 2008 12:40 PM |
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Thanks for the summary, Brad!
I'd nominate this thread for a number of 'gold stars' for that post... (I immediately printed it out to add to one of my binders.) Good stuff!
(Let's not neglect the importance of specific wheel and tire combinations... let alone brakes...!)
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2wankel
Hauling
Posts: 133
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posted January 31, 2008 04:09 PM |
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Wow, thanks Brad. I have to digest this before asking anymore questions. Great info!
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2wankel
Hauling
Posts: 133
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posted February 03, 2008 09:58 AM |
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quote:
Toe: 1/16" toe in is okay but to autocross you really need some toe out for it to dive into corner. Which compromises braking. Stock is 1/4" toe in!!!!! to increase understeer or reduce all that rear supension oversteer your pick.
The upper a-arm shaft has threaded ends to allow you to move that upper a-arm forward or back. To adjust caster. Crank it as far rearward as possible to get max caster. These area pain to move - I removed the upper a-arms entirely and used a 1/2" breaker bar with 3 foot pipe cheater bar.
Hi Guys I'm back :-)
This past week and a half I installed four new ball joints, four new tie rod ends, new upper a-arm shafts with new dust boots, new idler arm, new sway bar bushings for the stock sway bar(i'll get thicker sway bar by the summer). I didnt get the lower a-arm bushings on time. So that is the only thing left besides the steering arm (the long bar that the tie rods connect to, I can't find it).
I also installed the upper a-arms before knowing about cranking them rearward. I'll do that. As far as alignment goes. I'm not sure about the toe in and toe out comment above. This is my daily driver and I will be autocrossing it as well. I'm also a spiritive driver. Whats the best setup for my alignment. Also if you have time, please explain why braking gets compromised.
Thanks much
____________
VMRC Website
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micah
Hauling
Posts: 167
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posted February 05, 2008 08:49 PM |
Edited By: micah on 5 Feb 2008 20:51
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yes Brad!!!! thanks soo much man, I still have'nt decided on what to do!!! All kinds of options. My tires are almost gone already, need traction so bad. Brad I'm gonna have to talk to you and pick your brain. I want to beat these new cars and I know I can after I solve the traction issue, no wrapping btw , just hop hop hop. I'm gone this far, might as well finish,,,,
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Brad
Rotorhead
Posts: 1672
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posted February 05, 2008 09:25 PM |
Edited By: Brad on 5 Feb 2008 21:28
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2wankel:
I like 1/16" Toe in. it's close enough to zero so it won't screw up tire wear but still toe-ing in for stability. And does not radically increase understeer like stock 1/4" toe in.
When you hit the brakes, a arm front suspension toes out so it messes up braking. | | brakes better than /
You can toe it out, i know guys with 1/4" toe out that autocross all the time but that much toe out ( or in) chews up the front tires. BUT, it'll really dive into corners.
MICAH:
axle wrap causes wheel hop. the spring winds up, axle moves forward, spring releases its energy very quickly and there's the hop.
if you want a band aid fix CLAMP the leaf pack in front of the axle to reduce wrap and better locate the axle, and it handles better too. PEP BOYS and AUTOZONE sometimes have these clamps. like fourteen bucks.
You can also ADD HALF a leaf to the front of the leaf pack - it reduces wrap and increase of spring rate is very small since most of the springing is done rear of the axle.
still say composite leafs are the way to go. guys remove their cal-tracs and other type traction bars after installing them, just not necessary anymore.
None of this is new technology, you can buy books on handling with good info and the older ones still talk leaf springs.
Now if someone can just clarify if rubber, urethane, nylon, delrin, or steel bushing in the leaf front spring eye is the best.......
____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge
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Brad
Rotorhead
Posts: 1672
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posted February 06, 2008 03:37 PM |
Edited By: Brad on 6 Feb 2008 15:40
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Also lowering blocks give the axle more leverage to wrap the axle up. > 2 inch blocks should be avoided.
I bet if you removed the blocks and clamped the front spring pack you'd increase traction. Also because the rear of truck will go up and increase rear center of gravity and thus increse weight transfer to the rear.
And thin sidwall tires are bad for traction. Thick 60 series or more tires help here.
Rear air shocks and an onboard compressor would be nice, increase rear wheel rate and increase CG for more weight transfer before you hammer it.
Shocks mounted one forward, one rearward does wonders to reduce axle wrap. Unfortunately REPU has them angled inward.
It's all tradeoffs. Looks, straight traction, cornering traction, cost, installation time, fabrication.
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bwaits
Hauling
Posts: 119
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posted February 07, 2008 01:44 PM |
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Maryland Metrics
quote:
Thanks for the reply Billy
5" under the head. 3" to 3.25" non threaded section under the head.
Stock length is 4" under the head but I need more room for:
-poly bushings that do not compress as much as rubber
-thicker shackles for less lateral deflection
-run a thicker, wider washer under the nut
-Nylox nut - if you know where to get one of these this size that would be great
I have had some good luck with these guys on some hard to find metric hardware. Give em a try.
http://mdmetric.com/
-billy
____________
ACT . Accufab . AEM . APEXi . AutoMeter . B&B . B&M . BBK . BORLA . Bosai . Brembo. Center Force . Earl’s . Eibach . Energy Suspension . Fluidyne . Goodridge . Greddy . HKS . INJEN . Innovate Motorsports . INTRAX . K&N . KONI . KYB . Magnacore . MOMO . MSD . NGK . NOLOGY . NOS . NX . Pace Setter . Power Slot . Prothane . ReSpeed . Rotora . Sparco . Suspension Techniques . Tanabe . Tokico . TurboNetics . Unorthodox Racing
ReSpeed Online Catalog
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