Front End Bounce At 50mph

[WhiteTBucket]

Hi T Bucketeers, From a UK newbie, (Paul)

Has any one encountered Axle oscillation at 50 mph and again at 60 mph ?

This is NOt steering shimmy or wheel wobble, I've had and rectified both of these.

It starts at around 50 to 51mph and the same at 60-61mph, The hole front end starts to see saw from left to right, it steers straight and if you increase speed to 55 it disappears.

It appears to be as if i have square wheels or flat spots on the tyres ! I've got new tyres that have been balanced with the wheels off the car, Tracking set at 1/8 toe in, castor at 9 degrees.

The front end is Total Performance with aluminium Wilwood hubs, two pot Wilwood calipers, 4-1/2 x 15 Billet wheels, MT S/R radial tyres, and friction shocks as per TP front end.

Beginning to think it may be hubs out of balance, so next step may be to try wheel balance ON car to balance whole rotaing assembly of Hub and wheel.

Any ideas ?

Many thanks, Paul Q UK

 

[Rick]

Hi T Bucketeers, From a UK newbie, (Paul)

Has any one encountered Axle oscillation at 50 mph and again at 60 mph ?

This is NOt steering shimmy or wheel wobble, I've had and rectified both of these.

It starts at around 50 to 51mph and the same at 60-61mph, The hole front end starts to see saw from left to right, it steers straight and if you increase speed to 55 it disappears.

It appears to be as if i have square wheels or flat spots on the tyres ! I've got new tyres that have been balanced with the wheels off the car, Tracking set at 1/8 toe in, castor at 9 degrees.

The front end is Total Performance with aluminium Wilwood hubs, two pot Wilwood calipers, 4-1/2 x 15 Billet wheels, MT S/R radial tyres, and friction shocks as per TP front end.

Beginning to think it may be hubs out of balance, so next step may be to try wheel balance ON car to balance whole rotaing assembly of Hub and wheel.

Any ideas ?

Many thanks, Paul Q UK

I had this problem and it went away when i put hyd.shocks on the front.I had many scary drives when the front end started bouncing left to right really fast.As i said the only thing i did was take the friction shocks off and put hyd. shocks on.Wintec and RPM sell the bolt on kit for the total frame.

 

[409T]

I had this problem and it went away when i put hyd.shocks on the front.I had many scary drives when the front end started bouncing left to right really fast.As i said the only thing i did was take the friction shocks off and put hyd. shocks on.Wintec and RPM sell the bolt on kit for the total frame.

I had the same problem and went from regular oil filled shocks to gas charged ones and it went away for me as well. I still wonder what the cause was. The owner before me put unusually long shackles on the front spring and I never changed them. Anyone think this could be the cause?

Jeff

 

[T-Test]

I had a '40 Ford front axle that was worn out where the king pins went through the axle, caused a shimmy as you described. I couldn't get it repaired, so I replaced it with another that I had. Bought another to replace that one from RPM. Also check the tightness of lever shocks and probably be better to replace with hydraulic or gas shocks. Bruce

 

["The Bat" out of hell]

Like they said but nicely" friction shocks are junk",but the action is starting from wheel,tire or disk out of balance or out of round or even too high PSI in tires or can be just bumps placed right to start it [ so check same]but none of them can be controled well by friction shocks enless there very hard on and the prob is very small.
Put some real shocks on it and you'll be much more happy and safe too.

 

[VegasBruce]

I check my friction shocks every time I check the oil. They are a high maintenance item, and have to be kept tight. I know the car would handle better with hydraulic shock, but I like the look.

 

[WhiteTBucket]

I check my friction shocks every time I check the oil. They are a high maintenance item, and have to be kept tight. I know the car would handle better with hydraulic shock, but I like the look.

Thanks for all your thoughts guys, I like the look of the frictions too but may consider Hyd' shocks as i would like to get to the magic Ton without shaking to bits on the way.

Gonna try on car wheel balance first to try and get whole hub and wheel assembly balanced to see if that helps.

Cheers Paul Q

 

[BERNIESWELDING]

the reason you are having this problem is because you mentioned your camber was a 9 degree, that is too steep. it needs to be between 5 and 8 degrees. look in a suspension book and there is different set up's for different applications. there are some good reference books available. also check the weight capacity of your front spring. it might need a leaf or more added.remember the functioning is in the geometry.

 

[RPM]

the reason you are having this problem is because you mentioned your camber was a 9 degree, that is too steep. it needs to be between 5 and 8 degrees. look in a suspension book and there is different set up's for different applications. there are some good reference books available. also check the weight capacity of your front spring. it might need a leaf or more added.remember the functioning is in the geometry.

His castor, not camber is at 9 degrees Big difference in the two terms.

 

[guilld]

If the castor limit was 9 degrees why do you see the old sling shot dragsters with what looks like 15 degrees. I would think from my experience with bikes the more castor (rake on a bike) the more it wants to go in a straight line. When going slow the wheel would have a tendancy to want to flop over.

 

[ellis8500]

It is true that more caster will make the car run a straight line. Toe-in also helps it run straight. However, there can be too much of a good thing. More caster increases steering forces. For manual steering, 6 degrees seems to be a good amount of caster for running straight and not having too heavy a steering wheel. With power steering the caster can be somewhat higher. Toe-in also helps the car run straight. However, too much of that and you'll wear the tires out too soon. If you read about both here and on other forums and articles, you'll find that caster of 5 to 6 degrees is the accepted norm along with about 1/8th inch toe-in. Keep in mind that both of these are typical and good starting points. the best values for YOUR CAR can only be determined as you drive it and adjust.

 

[BERNIESWELDING]

ok i made a mistake it is caster instead of camber.



i am a welder, i hang semi molten metal up side down, known as overhead welding