Loose Rear End on Hard Braking - Fix?

[Random driver]

I just installed G LOC R12 front and R10 brake pads on my GT350R. Also replaced brake fluid with Castrol SRH Racing fluid. Car has 1400 miles. I bedded-in the pads the past two days. Then today, I did some testing from 100-0 and 60-0. 60-0 seemed normal and the car seemed balanced. Good initial bite and great stopping power. But above 60 (around 80 to 100mph) while braking hard, the rear end was loose and would step out towards the passenger side. I thought it might be a poor line (not driving straight and having the car positioned poorly). But, after repeated attempts and being careful to have the car positioned straight, the car continued to step out with the rear towards the passenger side.

Its pretty unnerving. I want to try to dial this out before next track day.

I did not really do any hard braking before with the oem pads and fluid. So, I do not know if the car would have done the same thing before the GLOC pads.

Anyone experience this? Any solutions? Thank you in advance for any insight.

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[nastang87xx]

Sounds like you're trying to fix something that's not broken with new pads, at least based on only having 1400 miles on the car. 400 grit those rotors and go back to OEM pads and see if you're getting the same thing.

 

[CSL]

Sounds like the rear pad is too aggressive. I went with a front that is probably a bit more aggressive than the R12 (Raybestos ST43) and kept the stock rears. It works really well.

 

[Spacebird]

I've got the exact same setup which I ran at COTA. I buried the brakes at 140mph lap after lap and did not feel the rear end step out.

Are you running a track alignment?

 

[Random driver]

Sounds like you're trying to fix something that's not broken with new pads, at least based on only having 1400 miles on the car. 400 grit those rotors and go back to OEM pads and see if you're getting the same thing.

Ha. Very true Nastang. But, thats part of the fun..."fixing" something thats not broken.

The OEM pads are really good. But, I want a more aggressive pad for the track. I suspect the car well do just fine as soon as I figure out the tail wagging.

 

[Random driver]

Sounds like the rear pad is too aggressive. I went with a front that is probably a bit more aggressive than the R12 (Raybestos ST43) and kept the stock rears. It works really well.

Thanks for the insight. I might try that set up if I cant figure out the current tail out issue.

 

[Random driver]

I've got the exact same setup which I ran at COTA. I buried the brakes at 140mph lap after lap and did not feel the rear end step out.

Are you running a track alignment?

Well, that is great info. I can now eliminate one variable. I'll stick with the pad set up (R12 f R10 r) and work on track alignment. I still have street alignment. I wanted to see how tire wear and times improved from street to track alignment. But, maybe I'll skip that as I do not want to test the car balance at 100+ under hard braking.

Many thanks Spacebird.

 

[CoolTech]

If it is consistently sliding the same way under hard braking, you should have the alignment checked.

 

[Random driver]

If it is consistently sliding the same way under hard braking, you should have the alignment checked.

Thanks Cooltech. Gonna work on alignment tomorrow.

 

[RustedAngel]

You're sure the shipping blocks aren't in your rear shocks, yes?

 

[Random driver]

You're sure the shipping blocks aren't in your rear shocks, yes?

Yes, thankfully had those removed when I took delivery.

 

[dsm_mikey]

I have a 2016 GT350R/ I am running the factory CUP2 tires and am currently running the GLOC 16's Front and 12 Rear and Love them! I run at Road America and have 0 braking issues currently. I run -2.5 Front Camber (Vorschlag Camber Plates maxxed out) and -1.7 Rear Camber and 1/8" total Toe OUT Front and 1/8" total Toe IN REAR.

I did have instability under hard braking in a straight line earlier in the year when I had about 1/8" Toe Out in the rear. I changed this to 1/8" Toe IN for the Rear and everything is much more stable under hard braking.

I did run the 12/10 combo previously and had 0 braking issues. I would definitely check alignment!

There IS a HUGE difference between the Stock pads and these pads in braking. The GLOCs are night and day...how do I know?? My brother ran the stock pads with his GT350 (Non -R) and I drove it back to back with my mine...seriously...night and day difference. Not even close. Keep in mind my R runs Cup2's and he had the stock SS's on. This was back to back runs at Road America (25 minute sessions). All the above aside, the stock pads are the best stock pads on any car I've driven. They can put up with track abuse, just not the ideal choice in my opinion.

I personally did not care for the 12's in the front and went to the 16/10 combo for most of the year and switched to 16/12 with the last pad change. Both 16/12 and 16/10 feel great.

Danny and his support from GLOC are the best. A+ company. A+ Product.

-Mike

 

[firestarter2]

If it is consistently sliding the same way under hard braking, you should have the alignment checked.

Make sure the road you are on isnt banked most are for drainage lol

 

[firestarter2]

I see my toe in degrees?

I have a 2016 GT350R/ I am running the factory CUP2 tires and am currently running the GLOC 16's Front and 12 Rear and Love them! I run at Road America and have 0 braking issues currently. I run -2.5 Front Camber (Vorschlag Camber Plates maxxed out) and -1.7 Rear Camber and 1/8" total Toe OUT Front and 1/8" total Toe IN REAR.

I did have instability under hard braking in a straight line earlier in the year when I had about 1/8" Toe Out in the rear. I changed this to 1/8" Toe IN for the Rear and everything is much more stable under hard braking.

I did run the 12/10 combo previously and had 0 braking issues. I would definitely check alignment!

There IS a HUGE difference between the Stock pads and these pads in braking. The GLOCs are night and day...how do I know?? My brother ran the stock pads with his GT350 (Non -R) and I drove it back to back with my mine...seriously...night and day difference. Not even close. Keep in mind my R runs Cup2's and he had the stock SS's on. This was back to back runs at Road America (25 minute sessions). All the above aside, the stock pads are the best stock pads on any car I've driven. They can put up with track abuse, just not the ideal choice in my opinion.

I personally did not care for the 12's in the front and went to the 16/10 combo for most of the year and switched to 16/12 with the last pad change. Both 16/12 and 16/10 feel great.

Danny and his support from GLOC are the best. A+ company. A+ Product.

-Mike

 

[DrumReaper]

I performed a panic stop from 65mph one day and the backend stepped out on me, but it had more to do with the road surface than the performance of the brakes.

In Utah during the FRP performance driving day, I stepped on those brakes as hard as I could lap after lap without any loss of composure of the car.

It's likely the road surface.

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