Front wheel hop under high speed braking, any ideas?

[CID440]

So I've noticed this problem recently while at freeway speeds only, around town and speeds under 50 mph it's non existant.  I'm running the master power disc brake system and have the hotchkis upper control arms with relocation blocks.

It feels like a warped rotor would feel but you'd think it would always be apparent at any speed.  I was very hard on them brakes on the autocross courses but that was two years ago and this problem just started occurring.


Anyone got any ideas or input.

[CID440]

Every bolt is tight up there so.....   ?

[brads70]

Worn shocks or in the suspension?

[jimynick]

First place I'd look would be the shocks. If they're doing their job, that shouldn't be happening. 

[Skunkworks Challenger]

Hard spots on the rotor caused by heat/wear or warpage.  PK

[Matt70]

If this is a pretty violent vibration (like wheel hop) and your not feeling anything at lower speeds I don't think it's warped rotors. If they were that bad I would think it would be felt at lower speeds also 

[dodj]

Strut rods (bushings) and shocks are the first things I would look closely at.

[HP2]

Strut rods (bushings) and shocks are the first things I would look closely at.

X2 here as something to check out in detail. Strut bushing integrity is actually a big part of braking stabiity. For that matter, ball joint and control arm bushig inspections should be done as well. lateral loads on an autocross could deform or destroy any cheap or marginally good bushings and joints.

While you may have been hard on the brakes at the autocross, you typically do not put enough heat in them during a 20 second run to actually warp them. Plus the break between runs allow them to cool enough to not consider warping a problem, IMO.

Also, are you sure its the front? Wheel hop in the rear under hard braking is not uncommon with leaf spring cars. But, Is it hard braking or only high speed braking?

TC

[CID440]

Yep I'm sure its the front.  Hard braking brings it out more so than just a light touch of the pedal at speed.

Strut rod bushings replaced with energy suspension polyurethane bushings last year along with lower control arm bushings,  Ball joints new when disc brake kit was installed, upper control arms and ties rods are hotchkis with heim joints, shocks have around 6000 miles on them.

I will get under there and check them strut rods for tight along with everything else hoping maybe it will be that easy,  regardless I'm getting some new drilled slotted rotors for her for X-mas

Thanx all for your input and will update.

[CID440]

Strut rods (bushings) and shocks are the first things I would look closely at.

  That was it!  The new bushings must have squished and settled.  Both sides were loose and tightened up a nuts worth of threads.

Thanx for the help guys