bad shimmy

[surf monkey]

as anyone whos driven in the UK knows , the road conditions are shit...potholes and the like....out in the t tonite one wheel went into a pothole and both front wheels shimmied like fuck...slowed down (wasn`t going too fast thankfully)and it stopped almost instantly....i`ve been over bumps with both wheels and it handles ok....any ideas?

Monkey
www.monkey-inc.co.uk (http://www.monkey-inc.co.uk)

[choprods]

if it stops its gotta be wear on a steering part or kingpins/bushings.
You Could check your tires for runout/condition etc.......

[ELpolacko]

Check your alignment too!

Negative toe can do this exact same thing on a beam axle car. Also check for excess play in the steering links, loose tie rod ends, steering arms, worn box etc.

[Rand Man]

I think it is a type of bump steer condition. "A friend of mine" experienced this in Camero that had been jacked-up in the rear (which put it into negative caster). I believe the shimmy comes from a violent switch between toe-in and toe-out. This could come from worn parts such as tie rod ends or a design flaw. What type of front suspension do you have on what car? Transverse leaf spring, cross steering or side steer? Post some pictures. I’ll bet someone might be able to spot a design flaw.

[Pist-n-Broke]

Need more info. Type of susp? Not enough caster can cause this, bad ideler arm on A-Frame cars. Worn parts, It all needs to be good to drive right.
The Wizzard

[Eyeball]

If by shimmy you mean the tires were bouncing up and down like two basket balls I know what you are talking about. With my roadster you could be tooln' down the road just fine until you hit a pot hole and then it was like all hell had broken loose. One tire would start and then transfer the shimmy or bounce to the other but if you slowed down it would go away. My roadster and my brothers A both suffered from it and the cure was tube shocks. I originally had lever type and he had speedway friction shocks.

[Eyeball]

One more thing, the old oil filled lever shocks worked fine on my roadster but as soon as one got weak I started to have the problem. I replaced them with another used set and was fine again until one of them failed. I looked at the price of rebuilt or having mine rebuilt compared to tube shocks.


So, I now run tube shocks. http://www.jalopyjournal.com/ubbthreads/images/graemlins/smirk.gif

Hope this helps.

[safariknut]

If you have a beam axle with cross spring suspension and cross steering(drag link runs parallel to axle)you might be experiencing drag link flexing.My cousin's 32 had this same problem and he cured it by installing a steering damper(a tubular shock absorber mounted parallel and connected to the drag link)from a Jeep Wagoneer and the problem was gone.
He used to experience this phenomenon when crossing railroad tracks at about 15-20 mph.The front wheels would oscillate from side to side violently and if you sped up it would get worse.You had to almost stop before it would cease.

[**DONOTDELETE**]

I've been waiting for someone to suggest a steering damper. I bought one from a VW bug(?) that I'll mount to the '36 axle and the tie rod. Looks the same as the $99 chrome-plated one and costs ten bucks if you shop.

[TV]

When I bought my 32PU it had the same problem, drove fine but don't hit a bump with one tire. I could also make it do it by steping on the brakes just as front tire hit a bump. The answere was, install a steering dampner, no more problem. I've got 10,000 miles without it doing it I'd say its fixed.--TV http://www.jalopyjournal.com/ubbthreads/images/graemlins/cool.gif { Bumpsteer}

[surf monkey]

thanks guys....steering dampers been mentioned by some guys over here too...heres a pic of the setup
monkey

[willowbilly3]

I had a 78 chevy 4x4 in my shop with the same problem. Low milage truck, everything was tight, toe was set but when he hit the railroad tracks it would go into the wobbling death tremors. Steering stabilizer fixed it.

[Jimv]

what your feeling is Bumpsteer.Just last week Thirtycoupe & I checked the toe in on my T & we got 1/4" toe out!! reset it & got it to 3/16ths" or so toe in( should be 1/8th).I took it out & the thing had bad Bumpsteer. exactly what you explained. Last nite I reset the front end to 1/16th toe in & its gone!! runs great.
just double check it & you should be OK.
jimV

[HOTRODPRIMER]

SM,I see the shock mount at the bottom of your spring perch,,but, you have the shock mounted to the axle.

Could the shock not have enough travel and bottom out and cause the problem?

Maybe turn the mount around if there is room to do so and remount the bottom of your shock,,,,,,,,,,,don't cost anything but time to try! HRP

[Rand Man]

I see the problem. You're trying to steer that thing from the wrong side. Just kidding! Please send a side view. Is the rear of the steering rod lower than the rear attachment point of the radius rod? The way I understand it, the steering rod needs to be parallel with the radius rods, and also run fairly level. When you hit a big bump, the steering rod (if not in line) could flex and start a chain reaction. In the case of the truck, the sidewalls of the tall tires are probably flexing.

In general, the car following little bumps in the road describes bump steer. If you’re running bias-ply tires, they will want to follow bumps. Good shocks and a steering damper will help smooth things out. A case of the shimmy-shakes is serious situation. Get your basic geometry right.

[surf monkey]

thanks guys....the more i read about it the more i`m inclined to try the damper first.....theres plenty of travel in the shocks....i`m pretty sure the steering rod is parallel with the radius rod and definately above the rear attachment (the car is in the garage, which happens to be at the mother-in-laws, bless her..so i cant go and check)...can someone describe bumpsteer to me?

Monkey www.monkey-inc.co.uk (http://www.monkey-inc.co.uk)

[**DONOTDELETE**]

Here's what might work for you....

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2489063159&rd=1&sspage name=STRK%3AMEWA%3AIT

[surf monkey]

cheers for that..although he`s only shipping to the states...I might have tracked one down over here...has anyone used one of the so-cal ones that clamps onto the radius rod?
monkey

[HOTRODPRIMER]

yeah,the socal one helped on my roadster!HRP

[I go pogo]

[ QUOTE ]
Check your alignment too!

[/ QUOTE ]
The toe-in is the easiest first fix.Sandman and I played with his alignment for about 20 minutes befor we hit the wight toe-in. prior to that the ride could be varry exciting! Sandman drives allover Texas now.
pogo