Wiggle when BRAKING

[Roger08LTZ]

I was originally thinking of just replacing nearly everything in the front end as my Tahoe has 195,000 miles on it, but the components are adding up to more than I'm willing to spend right now. I have a Z55 suspension and all parts appear to be original or GM replacements. I'd like to identify the true cause of the issue rather than rebuild the entire suspension.

The symptom: When at highway speeds I hop on the brakes, there is a wiggle, where it pulls a bit first left, then right. The usual suspect for a pull when breaking is of course the brakes, but after this first wiggle when the car comes from full highway float to nose down then the breaking is dead straight no matter how hard you press the brakes, you can have your hands off the wheel and it stops dead straight. It's just the moment when the nose drops when the car seems to be unstable, so I'm thinking suspension. Next week, I'll run this up on the lift and check it out. Just wondering if there are some usual suspects to look for. I'm not sure when this started as this is my wife's car and I don't normally drive it. This week I'm driving it, it's not that bad, but it doesn't feel right and I'd like to correct it.

The rear air shock air bags are completely torn and the compressor does not work, but it sits just fine without the air shocks working. We almost never load much cargo or tow with this car, so I think I'm going to ignore the rear for now and focus on the front as I feel this wiggle would be from the front suspension.

Any ideas what would cause this wiggle when breaking at highway speeds. Thanks!

 

[B-train]

I'd look at upper control arms for sure - at 195k, the upper ball joints are most likely shot. Probably due for lower ball joints and then maybe tire rod ends if needed.

The way you describe it make me believe the same as what you suspect. Once the suspension/alignment squares itself back up, them it brakes straight and doesn't move. Just spend the money on new OEM parts and redo anything needed up front. As for the rear, if the compressor is still working just do Arnott shocks to save some money. Otherwise OE aren't too awful and just keep it like it was.

 

[Joseph Garcia]

As @B-train suggested, I'd first look at control arm bushings and ball joints. If there is any play, replace both the upper and lower control arms with OEM parts, which will include the ball joints.

I'm assuming that you have struts on the front, and if you do, one completely collapsed strut with no damping at all could be a cause of the nose dive.

 

[mb1500]

Tire condition / PSI? Last alignment was?

 

[Geotrash]

Sway bar end links.

 

[Roger08LTZ]

If anyone is interested, the root cause of the problem was an internally damaged right front brake hose. The diagnosis trick was to crack open the break bladder on each caliper fluid should freely flow with no input other than opening the bleeder. on mine the left side flowed freely and nothing came from the right side. What was happening was the left caliper was hitting first pulling the car left then probable a half second later the right caliper hits and pulls it back to the right. The part was GM Genuine Parts 176-2003 Front Passenger Side Hydraulic Brake Hose Assembly was a whopping $14.23 on Amazon, so they might be worth replacing proactively the next time if you are changing calipers. Car stops perfectly now. 100% fixed!

One suppressing thing to me was that the genuine part was $15 and the AutoZone Duralast was $48 similar to other local stores. So I waited the 1 day for the Amazon shipment to arrive.

 

[Fless]

We all need to be careful with "genuine" parts coming from Amazon, eBay, etc. Lots of counterfeit parts out there identifying as OE. Use a trusted vendor like dealership, Rock Auto, or brick and mortar parts store.

 

[Marky Dissod]

Never a bad idea to replace - or upgrade! - brake hoses when replacing / upgrading calipers.
(When was it ever a good idea to buy car parts from the rain forest?)