Scary rear end feeling at high speeds!

[Riftur]

Originally Posted by Tcoat

With the little info we have I am still putting my money on a tweaked sub frame that instead of being properly straightened was just adjusted with a bolt. Of course as you said there are many, many possibilities but this is my armchair diagnosis.

Thats where I would start also.

[Brzlimited661]

Update. I looked up my tires they are a cheap brand called pantera sport never heard of them a bargain brand im sure. It could be a combination of cheap tires and a non experienced alignment tech?

[Tcoat]

Originally Posted by Brzlimited661

Update. I looked up my tires they are a cheap brand called pantera sport never heard of them a bargain brand im sure. It could be a combination of cheap tires and a non experienced alignment tech?

The alignment some of us are talking about is not just the suspension. Like Deejay said they need to be looking at the alignment of the actual frame (not really a frame but close enough) of the car.


Can't even find any decent info on those tires.

[8RZ]

Are they even rated for "high speed?"

[Tcoat]

Originally Posted by 8RZ

Are they even rated for "high speed?"

They have a W rating but since manufacturers rate their own tires and there is really no standard for measurement that doesn't mean much.


This Pantera is speed rated

[Summerwolf]

Originally Posted by Brzlimited661

The door was replaced fender and the A pillar was pushed in the front driver side was tweaked slightly only thing the alignment shop told me needed replacing in the future was a ball joint.

So it hasn't been checked with any frame / body tools?

I kind of doubt that it is as simple as tires, seeing how extensive the damage was. Check over the measurements and start doing the elimination process.

[Spuds]

So, just explaining this because it may not be clear.

What everyone is referring to on the frame alignment is that a suspension alignment can only get the car set up statically. If something is wrong with the frame or suspension components, a good static set up may be very wrong dynamically when you put a transverse load on it such as going around a corner.

...

Another question I don't recall the answer to, is this literally just one place that this occurs, or is it on all off ramps? There's 2 places by my house where there is just no grip at the rear due to road surface/contour/magic/cold tires/whatever. If it's just one off-ramp, it could be just that patch of pavement.

[Brzlimited661]

Originally Posted by Spuds

So, just explaining this because it may not be clear.

What everyone is referring to on the frame alignment is that a suspension alignment can only get the car set up statically. If something is wrong with the frame or suspension components, a good static set up may be very wrong dynamically when you put a transverse load on it such as going around a corner.

...

Another question I don't recall the answer to, is this literally just one place that this occurs, or is it on all off ramps? There's 2 places by my house where there is just no grip at the rear due to road surface/contour/magic/cold tires/whatever. If it's just one off-ramp, it could be just that patch of pavement.

Thanks for explaining that. The car does do this on multiple offramps but only at high speed not low speeds i have not found a left turn to replicate this at a high enough speed

[guybo]

Switch the rear and front wheels (like a simple rotation) and take it for a drive. Tell us what happens

[humfrz]

Originally Posted by guybo

Switch the rear and front wheels (like a simple rotation) and take it for a drive. Tell us what happens

I see that he already tried that (post 10)


humfrz

[NOHOME]

Originally Posted by Brzlimited661

Ok so i have A 2014 brz that i took to get an alignment after an acident they got the car within specs they said but whenever i exit a freeway offramp the rear end wants to slide in a violent fashion. We checked the rear end everyrhing seems solid and not loose.
The only thing that is not within specs even with a camber bolt they installed on the driver side front wheel is the front caster which is at 4.24 degrees. Any ideas?

So the car was fine before the accident.

After the accident, the DS front alignment is still off. Caster you say.

The car becomes unsettled during a high speed RH sweep ( my interpretation of exiting a HWY)

Such a maneuver loads the DS front. DS front is the one with the wonky caster.

If the DS caster is not the same as the PS caster for any reason, the car is going to pitch a fit. Kinda like when you get the bad grocery cart with a bent front wheel; where the one wheel just kind of vibrates along. The fit might be induced either because the car has a dynamic caster change induced by the turn or from unloading the inside wheel and transferring all of the load to the one with a different caster setting.

If it a dynamic issue, you wont catch it with a wheel alignment. You will need to put the car on a chassis rack and make sure that it is square. Assuming that it is, you then need to find the bent part that is causing the caster number to be off.

If your alignment shop shoed you out the door with an out-of-spec caster value without bothering to figure out why it was out of spec, then you need a new alignment shop.

Tire wear might be a clue also, but rather than wait for a tire to wear out, go buy a cheap laser thermometer and after a good run down the HWY, pull over somewhere safe and see if there is a noticeable difference in tire temps.

[Brzlimited661]

Originally Posted by NOHOME

So the car was fine before the accident.

After the accident, the DS front alignment is still off. Caster you say.

The car becomes unsettled during a high speed RH sweep ( my interpretation of exiting a HWY)

Such a maneuver loads the DS front. DS front is the one with the wonky caster.

If the DS caster is not the same as the PS caster for any reason, the car is going to pitch a fit. Kinda like when you get the bad grocery cart with a bent front wheel; where the one wheel just kind of vibrates along. The fit might be induced either because the car has a dynamic caster change induced by the turn or from unloading the inside wheel and transferring all of the load to the one with a different caster setting.

If it a dynamic issue, you wont catch it with a wheel alignment. You will need to put the car on a chassis rack and make sure that it is square. Assuming that it is, you then need to find the bent part that is causing the caster number to be off.

If your alignment shop shoed you out the door with an out-of-spec caster value without bothering to figure out why it was out of spec, then you need a new alignment shop.

Tire wear might be a clue also, but rather than wait for a tire to wear out, go buy a cheap laser thermometer and after a good run down the HWY, pull over somewhere safe and see if there is a noticeable difference in tire temps.

What is Ds and Ps ? Thanks again for the insight

[Brayden_23]

Originally Posted by Brzlimited661

What is Ds and Ps ? Thanks again for the insight

DS = Driver Side
PS = Passenger Side

[humfrz]

Originally Posted by Brayden_23

DS = Driver Side
PS = Passenger Side

Except for cars in certain other countries ....then it can get confusing ...


humfrz