Steering, Suspension, & Brakes

I've noticed that under moderate to hard acceleration my car seems to lift a little - mostly the front left. When it does the car pulls a bit and then when I lift off the accelerator to shift it pulls back the other way. Didn't notice it till fairly recently. Only two changes have been the carb tuning (which did result in noticeably more torque :) ) and hitting a pot hole big enough to put a small dent/flat spot on the rim of my front left wheel. Car still tracks straight, no signs of damage to the front suspension, and I took the shock off to see if maybe the rebound valving was blown - it seems good. Haven't had alignment checked yet - what else would you check?



Edited 1 time(s). Last edit at 10/06/2013 10:59AM by rficalora.

Torque-induced precession? Maybe you need a little more right rudder during takeoff.



Edited 1 time(s). Last edit at 03/10/2013 12:08PM by lars49.

I'd take a look at the rear alignment to see if there is any thrust vectoring going on.

Lower air pressure in the right rear tire than in the left rear?

Hello Rob when the car starts doing that the car starts getting fun the way I see it you have three things to adjust if the issue is the rear end of the car controlling the front end which it should do I would start with looking at the toe adjustment keep in mind that depending on what kind of bushings you have the car will tighten the toe under hard exhilaration that means it wants to toe in the rear my car it toes out two more degrees right side then left side when the motor lifts the left front of the car it puts more weight on the right rear so the right rear should want more outward toe then left the next thing to look at is tire pressure trial and error will tell you what pressure gives you the most bite normally less pressure bites harder I would try not to very left to right pressure more than about 3 pounds first find a good baseline pressure that your car likes the next thing to adjust gets a little bit trickier but it will affect the car more than anything and that is the pre-load right to left on the sway bar I don't know what kind of adjustment you have on your sway bar but it should have a higher percentage of downforce on the left rear taking advantage of the car leaning on the right rear just because the car is leaning to the right does not mean it has to have more load on the right side tire the sway bar can keep the left side tire with the exact same amount of downforce no matter how much the car leans to the right when you start playing with sway bar adjustment you may also want to adjust the rear spring preload at the same time the most important thing in making these adjustments is right down each change you make and what it does to the car and do not adjust more than one thing at a time without testing tuning rear suspension is like making love to a woman you have to learn to massage it just right until it responds to your touch when you get it just right you'll know it because she'll scream LOL if the rear end of a car is set completely neutral and it gets a good bite it will turn left so hard it's almost unbelievable all because of the added weight or download on the right rear you cannot stop the torque of the motor from lifting the left front but you can compensate for it in rear suspension adjustment if you adjust something that makes the car turn right under a hard launch not tire pressure you have found the best adjustment spot for your car as long as the car still drives straight under normal driving what is normal driving? Signed more fun than a barrel of monkeys



Edited 2 time(s). Last edit at 03/12/2013 11:56AM by tomsbad6.

Hello rob Im just throwing this out there but if this just started after the pot hole I would check the crossmember bolts that could make it handel like that good luck and let us know how you make out

Rob,

Check your track measurements and, also, if you can, front suspension geometry. Your left front wheel may be jacked back a hair or the rear axle is jacked back a hair. It doesn't take much. I chased the same problem on a '57 AH 100/6 after I restored it. Took forever to figure out the axle was about 2mm out of kilter.

After changing motor mounts, front bushings, super expensive (in the 70s) alignment shop, etc. Pulled the rearend after an old racing dude suggested the rearend was bent. Measured and measured and I couldn't cipher the discrepancy. Took it to a machine shop with a proper jig and micrometers and, there it was! Changed everything.

Cheers,
Tim

Thanks for the ideas. Been traveling pretty much since posting this - Mexico to build a house (church mission project; my 4th and our church's 22nd); then Singapore for work. Back home now - son ran the riding mower w/no oil - blew up motor; connecting rod seized to crank and then disintegrated. Have to fix that before I get some time to figure out the car.

Quote:

.....son ran the riding mower w/no oil - blew up motor; connecting rod seized to crank.....

Boy, doesn't that sound familiar - happened the same way at our house a few years back.

Glad mine doesn't use or leak oil, cause I'm sure my son never checks it!

Torque steer what is it? Here are a couple videos that show real good examples of what a fast car naturally wants to do the first video. Titled first pass on spray is a fairly mild streetcar with a professional driver and an unbelievable transmission T5 the camshaft it's in my car is the cam used in Dino testing to build that motor I bought my cam from that engine builder cam and lifters used for 60 bucks it was his cam for testing cylinder heads in the Dino room it came with 12 different Dino Sheets and a lot of other good information the second video is just something I found on YouTube
[www.youtube.com]
[www.youtube.com]



Edited 1 time(s). Last edit at 03/24/2013 06:59PM by tomsbad6.

Yeah, I've seen the tendency in drag racing, but mine is doing it in semi-spirited street acceleration. I'm not dumping the clutch or accellerating hard enough to break the tires loose.

Hello hey Rob it's me again rear end torque steer use more noticeable under moderate acceleration versus breaking the tires loose when the tires break loose they're not pushing the bushings as hard as when the car is hooked up I would guess you have enough miles on your car that the bushings in the rear which looking at photos I count 12 bushings all designed to control the wheels lateral movement no bushings installed to control movement forward and backward a fast TR six will not run on rubber or urethane bushings and their bushings are set to control forward and backward more than lateral that is why Richard good came up with his NilTron bushings I would guess your car is getting enough miles on it that the bushings probably urethane can no longer control the rear wheels the good news there is a very simple test tie the front end of the car to the ground solid get in the car tried to gently take off watch the forward movement of the rear wheels if the wheel center moves more 1/8 of an inch you will know urethane bushings cannot handle it hard nylon bushings are very cheap and easy to make my car runs all steel bearings if you talk to Ted Lathrop he likes hime joints I am guessing if you try that test on your car you will probably find 3/8 of 1 inch of movement possibly more that will more than explain torque steer signed IRS is still my preference

I finally got a chance to look at the car today and looks like I found the source of the torque steer... with the back end up on jack stands I can wiggle the left wheel without much effort. Not an inch, but probably 1/4". I was by myself & dark out so it was hard to see where the movement was coming from. But, I didn't see the control arms moving so I think it is the bearing assembly. About a year ago one of the bearing assemblies was bad. I didn't keep notes & don't recall which side it was. If it turns out it's the same side, what would cause them to go bad so fast?

OK, it was definitely a failed hub. Thanks for the info Tom, you led me to it. Replaced it with a new one and torque steer is gone. Got a 3 year warranty this time - at least if it fails again I can get it replaced. Old one came from RockAuto. Was disappointed with them... I'd called Raybestos to confirm the axle nut torque setting and when they heard it failed in about 3k miles they said they could analyze it in their lab to figure out why it failed. I'd have to have the dealer I got it from send it to them but there'd be no charge. RockAuto's position, however, was once the part is out of warranty they don't want anything to do with it.

Hello Rob that's great the hub is a rather unlikely thing to go bad you would think I hope that fixes your problem

The hub is a bearing hub assembly from a 4x4 S10 pickup. It's used by a lot of custom and after market IRS's including many Factory Five cobras. Apparently they fail enough there's lots of forum chatter and improper torque seems to be the leading (perceived) reason - and different year ranges of S10's called for different torques. My 95 S10 pickup 4x4 brim hubs (used in my IRS) call fro 181 ft/lbs... I triple checked the torque this time.

But, I'm not sure torque was my problem... Mine were originally salvage yard parts and one was bad pretty much from day one (less than 20 miles anyway). I replaced it but don't recall if i did both or not. Thought I did, but now not sure. Reason i'm not sure is i know i bought 2 hubs. I kept the old ones. When this one failed, i opened the box with the old ones and one is clearly used. The other has light surface rust in a couple of spots but is definitely way cleaner and looks like it may be one of the new ones... so, now i'm wondering if I inadvertently put the used one back on?!?! Since I wasn't sure I went ahead and put a new (3yr warranty) hub on this time.

Frustrating thing is Raybestos offered to analyze my hub in their lab, but I had to have the dealer I got it from send it to them. Called RockAuto (where i bought them) and they had no interest in helping. Basic message from the support guy I talked to was once it's out of warranty they have no mechanism to receive it back and do anything. Needless to say my new one this time came from my local parts store.

Resurfacing this thread for some thoughts... while I had my car up on jack stands, I checked the rear suspension too. It's only been 5 months but both hub/bearing assemblies are already showing signs of wear. The left side in particular has some noticeable play. This is the 2nd new hub on that side in less than 4k miles. Since improper torque seems to be what most folks say is the cause of failure, and since I was having to use a rented torque wrench (spec is 181 ft/lbs and mine only goes to 100) I got two different torque wrenches the last time. I torqued it with one and then checked it with the other so I am very confident it was torqued to spec. The hubs i got have 3 year warranties so it wont cost me to redo them, but what else might be causing them to wear out so quickly?

Hello Rob I have no idea what you're hubs came out of so I cannot say for sure but I know with the Nissan hubs that I use S 13 platform they call it Nissan used it from 1990 to the present the Nissan guys will not run a aftermarket bearing you see good factory bearings on eBay selling for twice what a new aftermarket bearing costs they claimed aftermarket bearings never last more than a year my bearings had 60,000 miles on them when I got them and I have put another hundred thousand miles on with no problems mine do have a small dust seal between the bearing and a half shaft the half shaft slides into the seal you might check to see if that seal fits correctly if you have one I think it's great your at least wearing out parts driving the car most people that have nice cars never drive them

those bearings should think they're on vacation in a car is light as yours they had to of been designed for something heavier than that

The hubs I'm using are Chevy S-10 4x4 hubs. Definitely way heavier than my car -- don't get why they're wearing out. My car tracks straight & tires aren't wearing funny -- so can't imagine alignment is causing them to wear.

You mentioned "seals" -- hmmm. That is interesting and could explain the problem. The uprights on my IRS are basically just plate steel with a hole in it. The hub bolts to the outside & the axle stub passes through the hole from the back side. There is no provision for a seal... Guess I need to figure out if there's supposed to be a seal or if the S10 hubs have integral seals?

If not that, what else might cause them to wear so quickly - it's only been about 4-500 miles since I replaced them the last time??