1978 C3 steering too tight, too sensitive

[Timrock]

1978 Coupe:

It is too much work driving my car! There is no play or give in the steering. The slightest bump and the wheel jerks. The car is in great shape and does not need front end work. The alignment is good. The car rides straight. Why is the steering so sensitive? Is there a way to "loosen" it up and give it a tiny bit of play?

I have just read the piece by toobroketoretire and I'm thinking that might be the answer to my problems. Tirepressure! My car has the 25560R15s. I have them set at 32lbs. The car rides really hard and is hard to handle. I really would like my wife to be able to drive this car, but as of now that's not likely. I'm gonna drop the pressure and see if that resolves the the issue?

I see that this issue is very common on the web, and have been reading about it, but there does not seem to be one good answer. Should I have the car re-aligned? The recommended settings seem to be all over the place. What are the proper settings? If the car is not fun to drive, why have it all?

I do have to replace the steering pressure vlave because of a slight leak, but that can't be the cause.

Please help!!

 

[toobroketoretire]

When I bought my '82 in 1988 I put 30 psi in the 255X60R15 tires and immediately wore the centers completely out when the sides still had 3/8" of tread left. My 16 year old son complained about the VERY harsh ride and how it made him sick to his stomach. The next set of tires I ran 25 psi and their centers also wore out long before the sides. I found the perfect pressures are 20 psi front and 17 psi rear and with those lower pressures I get over 50,000 miles out of my tires.

The huge "balloon" 255X60R15's have an 1875 pound load rating at 35 psi but when installed on a C3 they only support 900 pounds. That's why the lower 20/17 psi pressures are perfectly acceptable as long as those pressures are maintained.

 

[SVO]

Twichy Steering

Is this a car with manual steering converted to power steering? On a manual steering car, the steering arms (which attach to the spindle) have two positions for the tie rod end. The forward hole in the steering arm is for normal steering, the rear ward hole is for fast steering. On a factory power steering car, the rear ward hole is sealed with a metal rivet. If the car has been converted from manual to power, the tie rods need to be mounted in the forward hole. If the tie rods are in the rearward holes, with power steering, the steering will be over boosted resulting twitchy and very quick steering response. In addition, there is concern that such an steering arrangement may result in steering lock-up and loss of control when the wheels are turned to a hard left/right position.

As to the hard steering, has someone mis-adjusted the steering box? The box should have a small amount of "slack" in it when the wheels are pointed straight ahead.

As to running lower tire air pressure, I would approach that with much caution. Just my personal opinion.

 

[Timrock]

1978 C3 steering is way to sensitive

My car is a 78 base coupe 4-sp with power steering/brakes/windows and ac. I do not believe any conversion has been done. How would I adjust the steering box to give it some play?

 

[GTR1999]

Your car is setup as they all were and the PS, if correctly functioning, will certainly move the steering without issue with either 20 psi or 30 psi. Yes tire wear and feel will be different or if this was manual steering but there is a problem there. Steering boxes use usually too loose, especially ones that were worked on in the past. Look at the cover of the box at the lash screw, does it have any threads showing above the jam nut? If the front end is jacked up can you feel any difference going from lock to lock? The lash screw on the cover engages the teeth on the worm and sector so you can back it off if you want to test it. The correct on the car adjustment is to have the box on center, loosen the lash nut, tighten the lash screw until you feel it snug up and tighten the nut while holding the screw. If the box was too tight to cause your problem the gears are probably worn out and the box will need a proper rebuild. The control valve balances the pressure from R to L, if it was out of balance you would feel more assist in one direction then the other, really out the steering wheel would osillate. Does the pump make noise?

 

[Vettehead Mikey]

I run my tires at 30-32 psi and have no wear issues, rough ride, 'squirrlyness' in handling or oversensitive steering. The car is dead bone stock as they come.

 

[Timrock]

lowering the tire pressure has really worked

The pump does not make noise. I have lowered the tire pressure as was suggested to 20 in the front and 17 in the back. The ride and steering control are DRAMATICALLY better. I can now drive the car with one hand on the wheel. The ride has softened up nicely. I have a bad back, so this is great.

The car does still pull to the right very slightly. I have a leak in the pressure valve and have bought a new one. I'm going to replace it, as well as the old hoses. After that is all set up properly, if I still have a pull of any kind, I'll get a fresh alignment done at a Corvette specialist.

I may try to adjust the steering box also.

Thanks so much for your help.

 

[GTR1999]

If you need help with the box let me know I can walk you through it. If you have access to a 0-30 in/lb dial TW you would be better served to pull the box and make the adjustment on the bench.

You can run what tire psi you want but I run mine all at 30 psi without any wear or steering issue. 20/17 seems low to me but I'm not going to debate it. Back in the day when I was a kid installing new tires we set them all at 28 psi.

Good luck, I also know about a bad back!

 

[toobroketoretire]

The pump does not make noise. I have lowered the tire pressure as was suggested to 20 in the front and 17 in the back. The ride and steering control are DRAMATICALLY better. I can now drive the car with one hand on the wheel. The ride has softened up nicely. I have a bad back, so this is great.

The car does still pull to the right very slightly. I have a leak in the pressure valve and have bought a new one. I'm going to replace it, as well as the old hoses. After that is all set up properly, if I still have a pull of any kind, I'll get a fresh alignment done at a Corvette specialist.

I may try to adjust the steering box also.

Thanks so much for your help.

Congratulations, now there are two people in this world who know the big 225 thru 255X60R15's only require 20 psi front and 17 psi rear. I've been running those lower pressures for 25+ years and I get unbelievable mileage out of them. At 30 psi they were shot in only 20,000 miles but now I get 50,000 or more. And the ride is as soft as a full sized passenger car.

 

[toobroketoretire]

I run mine all at 30 psi without any wear or steering issue.

You'll realize 30 psi is way too much when it comes time to replace your tires. The centers will be worn smooth when the sides still have almost full tread depth. Since I bought my '82 in 1988 I have gone thru about 12-15 sets of tires so I have had the chance to closely observe the wear on each set. The G.M. engineers were fully aware of the tires only needing 20 psi/17 psi but couldn't recommend it for product liability reasons.

 

[GTR1999]

You'll realize 30 psi is way too much when it comes time to replace your tires. The centers will be worn smooth when the sides still have almost full tread depth. Since I bought my '82 in 1988 I have gone thru about 12-15 sets of tires so I have had the chance to closely observe the wear on each set. The G.M. engineers were fully aware of the tires only needing 20 psi/17 psi but couldn't recommend it for product liability reasons.

Well as I said I don't plan on debating but will only add, in my case anyway, I just replaced all 4 tires 1.5 years ago. I replaced them not because of wear, but age.They had about 10k miles on them at 30 psi and the tread was equal and not even 1/2 life but they were 8-10 years old. So could I have continued on with them, possibly but running tires over 8-9 years is not something I like to do. I have seen them blow out, not a pretty sight. I doubt I'll put more then 3k miles on them a year but I will check the thread to see.

 

[toobroketoretire]

Well as I said I don't plan on debating but will only add, in my case anyway, I just replaced all 4 tires 1.5 years ago. I replaced them not because of wear, but age.They had about 10k miles on them at 30 psi and the tread was equal and not even 1/2 life but they were 8-10 years old. So could I have continued on with them, possibly but running tires over 8-9 years is not something I like to do. I have seen them blow out, not a pretty sight. I doubt I'll put more then 3k miles on them a year but I will check the thread to see.

Now that I have brought the subject up continue to inflate them to 30 psi and note how the tread wears like maybe every 6 months. You'll quickly see how much faster the centers wear as I did for my first two sets. I was only getting around 20,000 to 25,000 miles out of my tires until I dropped the pressures down to 20 psi/17 psi and suddenly I was getting over 50,000 miles out of them. I average about 25,000 miles a year because my '71 is my daily driver so in just two years I have already hit the 50,000 mile mark.

About 6 months ago I conducted an interesting test to see how pressure affected the tire's width. I started with 35 psi and it measured 11-3/16" wide at the widest part of the bulging. I dropped the pressure to 30 psi and the width only increased an additional 1/32". By dropping the pressure to 25 psi the width increased an additional 1/32" and at 20 psi another 1/32". At 15 psi the width increased another 1/32", at 10 psi another 1/32", and at 5 psi it suddenly increased about 1/4". From the initial 35 psi the tire's width only increased a scant 5/32" TOTAL by the time it was down to 10 psi. It wasn't until I hit 5 psi was any visible bulging evident which proves a tire has to be damned near out of air before you can actually see any sign of bulging. Then I re-inflated it in 5 psi increments and found it had reached it's maximum height at only 10 psi as any additional air didn't change the vehicle's height. So it only took 10 psi to bring it up to full height and then the additional 7 psi just made the tire firmer.

The really nice thing about the lower pressures is the ride quality becomes as soft as a much heavier passenger car. Because of the huge internal volume of the 225 thru 255X60R15's they only need half the maximum pressure to support the same load (the maximum pressure being 35 psi for an 1875 pound load). But as it's only supporting 900 pounds the pressure can be reduced by half. If they were on a light VW bug only 10 psi would be needed.

 

[Timrock]

I run my tires at 30-32 psi and have no wear issues, rough ride, 'squirrlyness' in handling or oversensitive steering. The car is dead bone stock as they come.

This is not helpful. Thanks.

 

[Timrock]

Alignment. What are the proper alignment settings?

I would like to have my car aligned, but I don't know who to trust to do the job correctly. What are the proper settings for a 78 C3, and who should do the alignment? Thanks.

 

[Vettehead Mikey]

This is not helpful. Thanks.

You're welcome.

I was pointing out that a car in good condition will not behave as yours does because of higher tire pressure. Any difference you feel by deflating them may be masking the actual root cause.

 

[toobroketoretire]

Your steering seems too sensitive because of it's rock hard balloon tires caused by excessive pressures. Drop the pressures to 20/17 and it'll ride like a Cadillac and you'll get triple the mileage. My front tires have over 50,000 miles on them and they still have 1/4" of tread left. As the rear tires propel the car they won't last quite as long as the front tires but they'll still go 50,000 miles without any problem. Just remember to check the pressures every couple of weeks so if you get a slow leak you can catch it early.

To support a given load you have two choices: A high volume/low pressure tire or a low volume/high pressure tire and the big 225 thru 255X60R15's are high volume/low pressure tires that only require 20 psi. Something very few people know because all of our modern tires are of the low volume/high pressure variety.

Drop the pressures to 20/17 and you'll be thrilled with the results.

 

[Antz81]

You're welcome.

I was pointing out that a car in good condition will not behave as yours does because of higher tire pressure. Any difference you feel by deflating them may be masking the actual root cause.

I have to agree here. I run similar tire pressure and don't have the issue described by the OP.

 

[toobroketoretire]

You're welcome.

I was pointing out that a car in good condition will not behave as yours does because of higher tire pressure. Any difference you feel by deflating them may be masking the actual root cause.[/QUOTE


When the tires are grossly over-inflated the steering becomes REAL quick and you feel every teensy-tiny bump in the road. If you're running 30+ psi drop the pressure to 20/17 like I'm running and you'll discover how nice a C3 can feel. You never inflate tires to their maximum pressure unless they're supporting a maximum load and the huge tires on a C3 are only supporting HALF of their maximum load. Even the F-70 tires are huge by today's standards and they too can be run at the lower 20-17 psi pressures.

 

[Timrock]

tire pressure

Again Vettehead, not helpful. Rude and arrogant. The is a mint condition 78 coupe that has been thoroughly inspected and never hit. Never rusted, always garaged. Matching numbers, never been molested. You assume the car is not in good condition and you're wrong.

 

[Vettehead Mikey]

Wow- try to help someone...........

Good luck.