roadrace suspension mods

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roadrace suspension mods

Postby prime suspect » Wed Aug 11, 2010 10:45 pm

I am currently working on a 77 monza to race in the 24hrs of Lemons need some input on what i can to do CHEAP to improve the handling on this car it will be 4.3 man trans stock rear housing with the s10 rear disc setup s10 spindles w/s10 balljoints man steering man brakes i have read that i can get 9 degrees caster if i swap the upper front control arms side to side , is that too much caster ? how will that effect other alignment adjustments ? im going with custom steel wheels 3 in backspace 16 in tires 245/50 rr on 10 in wide and 225/50 frnt on 8 in wide
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Re: roadrace suspension mods

Postby NixVegaGT » Tue Sep 07, 2010 11:26 am

Sorry I didn't see this post earlier. I've got a couple suggestions, hopefully I'm not too late. All of my suggestions just involve labor. One suggestion is to try to lower the roll center but that's only if the front suspension geometry is the same as the early Vega. I'm not totally sure if it is.

Measure the distance between the upper control arm (UCA) pivot and the lower control arm (LCA) pivot. If it's less than 9" between them then this modification is worthwhile. It does require a tapered reemer that matches the BJ taper. I think it's 1.5"/ft. I actually borrowed one from a shop down the street. (anybody else that knows feel free to chime in here). They are not inexpensive but you could probably sell it when you're done. I think the rules only cover actually parts into the bottomline. This would be a tool purchase... The mod is to burry the BJs about .5" into the spindle mounts. You still have clearance, although tight, but more importantly you reduce the height of the spindle (UBJ pivot to LBJ pivot about 10"). This moves the rotation center out and therefore the roll center down.

Why is that important? Then you can absorb the roll through the springs/shocks/swaybar and not through the suspension components. A roll center that's too high will cause more skidding because the roll force is applied high. It's like pushing a heavy box across a floor. Pushing the box low moves it smoothly. Pushing it high causes the box to catch and move inconsistently. You can't really get the roll center too low with our cars. The built in suspension geometry will not allow it but the lower you get it the better.

Another mod is to lower the CG by lowering the car. There are two ways to do this inexpensively: Cut the springs, and make the front spring pocket deeper. Cutting the springs is pretty easy. I took 1 whole coil out of my front and rear springs in the Vega before going with coil overs. For the fronts cut one coil out, heat up the new top coil and flatten it out. I know what you're thinking but it won't ruin the spring at all. In fact cutting an old spring will yield a very stable spring. Just make sure you let the coil cool down slowly. Here's a couple pix:
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This does two things. It lowers the car a bit and it increases the spring rate. For my '73 Vega, cutting one coil out lowered the car about 1.25" and brought the rate up to 430 lb/in. This also flattens out the LCA to yield more favorable neg. camber gain.

In the rear cut 1.5 coils out. This will bring the rate up to about 175 lb/in. and reduce the height to more like 1.7". Then adjust the ride height in the front to match the rear or a bit lower with the next mod: Make the front spring pocket deeper. You do this by cutting the bottom of the spring perch in a slight spiral. Then bend a piece of sheet metal to match the dia. in a similar spiral. That adds depth to the pocket while keeping the index of the lower perch for the spring coil and the shock mount. Here's a couple pix. One note here, these pix are of my LCAs. I needed the pockets to be a LOT deeper. You may only need 1/2" or so. Just lower it enough to make the front a tiny bit lower for high speed stability.
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Fat sway bars if you can afford them. Leave the rear small dia. for better handling. Fat as you can get in the front. Lowering the front will yield a little bit better caster. If you're using S10 ball joints, weld the sleeves in the lowers move toward the front. That should help a little. Then you can mount the upper a little rearward.

Get rid of the front bumper if you can. Cheap posi?
- Nic '73 Vega GT "DogBoxx" Batwing LS1
http://www.cardomain.com/ride/2357894
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1973 Chevrolet Vega GT

Re: roadrace suspension mods

Postby NixVegaGT » Tue Sep 07, 2010 12:51 pm

I forgot to answer your question about 9º caster. That is a lot. The detriments to going that far with the caster is it really changes the camber dramatically in a turn. Could even be enough to reduce the contact patch and reduce adhesion. The other thing it does is require move force to steer the car. Hard on the arms in a 24 hr. race. Just something to think about.

One more thing. The tire size. I would consider making the front and rear tires the same. Just speaking from long track experience. it is really nice to be able to rotate the tires front to back to even out the ware. This is especially helpful if you are given a tire budget. If you can afford spacers you could potentially use a steelie with more neg. offset and tune the location of the tire in the front wheel well. I found I can just barely fit 245/40/17 in the front with some minor front fender modifications. This is on an early Vega. Here's a tip to getting an exact measurement: Use a piece of hardware steel and a threaded rod. You can find the best place to put the tires that way. Here's a pic:
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245/50/16 is pretty tall though at 25.7". Maybe something smaller in dia. would work on the front and the rear. GOOD LUCK!!
- Nic '73 Vega GT "DogBoxx" Batwing LS1
http://www.cardomain.com/ride/2357894
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Re: roadrace suspension mods

Postby jdascout » Sat May 14, 2016 1:07 pm

Postby jdascout » Sat May 14, 2016 9:59 am
H bodies came with a factory setting of -.5 to -1.5 being factory recommended caster setting. for quicker steering response a more positive caster angle is preferred. your K.P.I. is preferred King Pin Inclination Angle. Why do you think BMW's handle so well? they come with a +4-5 degrees of caster. So if swapping out the upper control arms is a quick easy gain of 2 degrees. I would jump om it. I am building a 1974 base model hatchback. I found a 1964 Buick 300 V8, it only weighs in at 405 lbs. Iron block/aluminum heads and intake. Factory rated at 335 ft lbs@3000 and 250h@ 4000, as a budget build I picked up some GT control arms w/poly bushings and S10 spacers. to get the handling I want I am thinking. Moog V8 Cargo Coils, S10 2" drop spindles. I bought some sway bars, one of my neighbors friends was over so I held my front sway bar up to his front bar. It looks just about 1" wider each side at the link eyelets. S10 Extreme ZRQ58 uses a 1 5/8 ft sway bar. get my drift? (no pun intended) So with the stiffer progressive rate Moog cargo coils, relative lite weight of the 300. this should stiffen it up, and drop it down to an even ride height or rake a bit.

any thoughts on this train of thought?
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Re: roadrace suspension mods

Postby hurleyc33 » Wed Jan 25, 2017 12:54 am

Ball joint reamers can be purchased a Speedway/Summit. They sell two tapers very reasonable prices. These two reamers will take care of about 90% of all Ball Joints. They also have extended BJ's for the top control arm, improving handling in the turns.
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