Brake bias spring-GM?
Large Impressive Member
Joined: Jul 2003
Posts: 65,811
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
I've never heard of a GM one. But yes, I also got mine from DRM. They're available elsewhere, too.
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Melting Slicks
Joined: Oct 2000
Posts: 3,426
Likes: 4
From: Heidelberg PA
Cruise-In V Veteran
Originally Posted by CentralCoaster
60/40 spring? You'd be locking up the rear brakes if you had one of those.
Thread Starter
Racer
Joined: Oct 2005
Posts: 264
Likes: 1
From: La Grande Oregon
Originally Posted by CentralCoaster
60/40 spring? You'd be locking up the rear brakes if you had one of those.
CC, from what i have read here you have done a lot of brake testing with yours. This is my first vette in thirty years (86 Z-51) and i have lot to learn, so tell me why you feel this isn't a good idea for street/high speed back road set up? joe
Drifting
Joined: Mar 2002
Posts: 1,251
Likes: 2
From: Thomson Georgia
I have the DRM spring in both the 89, 90 vettes and haven't had any problems with the rears locking up before the fronts.
Granted, I am running the 275s and 315s and Z06 brakes on the 90.
There isn't as much nose dive under hard apply and the abs takes care of lockup.
Granted, I am running the 275s and 315s and Z06 brakes on the 90.
There isn't as much nose dive under hard apply and the abs takes care of lockup.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
It appears that the 60/40 50/50 terms are used loosely. That's not a true indication of bias nor would you want that bias.
Line pressure is only one of the factors. 50/50 line pressure won't get you 50/50 bias. To get 50/50 bias, you'd need an infinitely stiff bias spring, (or a solid metal sleeve) in the combination valve. I don't have all the answers yet... but getting closer. I've got a handful of bias springs from various years and some hydraulic guages. I need to invest in some more plumbing and a decent used master cylinder.
I do know that the stock 85 spring is a 31 lb/in spring, the abs DRM spring is a 45 lb/in spring, and GM changed the combination valve, maybe just the spring, many times over the C4 run. I presume to make it stiffer.
BTW, I'm running a 110 lb bias spring, which puts me probably very close to 50/50 line pressure. But that's to compensate for the large front caliper pistons and rotor diameter. So bias to the wheels is probably close to stock. Best 60-0mph is 118 ft if I recall correctly.
Line pressure is only one of the factors. 50/50 line pressure won't get you 50/50 bias. To get 50/50 bias, you'd need an infinitely stiff bias spring, (or a solid metal sleeve) in the combination valve. I don't have all the answers yet... but getting closer. I've got a handful of bias springs from various years and some hydraulic guages. I need to invest in some more plumbing and a decent used master cylinder.
I do know that the stock 85 spring is a 31 lb/in spring, the abs DRM spring is a 45 lb/in spring, and GM changed the combination valve, maybe just the spring, many times over the C4 run. I presume to make it stiffer.
BTW, I'm running a 110 lb bias spring, which puts me probably very close to 50/50 line pressure. But that's to compensate for the large front caliper pistons and rotor diameter. So bias to the wheels is probably close to stock. Best 60-0mph is 118 ft if I recall correctly.
Last edited by CentralCoaster; Jan 9, 2006 at 12:30 PM.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Originally Posted by bluealtered
CC, from what i have read here you have done a lot of brake testing with yours. This is my first vette in thirty years (86 Z-51) and i have lot to learn, so tell me why you feel this isn't a good idea for street/high speed back road set up? joe
I think the DRM spring is the best brake upgrade you can buy for the money.
Melting Slicks
Joined: Oct 2000
Posts: 3,426
Likes: 4
From: Heidelberg PA
Cruise-In V Veteran
Originally Posted by CentralCoaster
I think the DRM spring is the best brake upgrade you can buy for the money.
Thread Starter
Racer
Joined: Oct 2005
Posts: 264
Likes: 1
From: La Grande Oregon
Thanks everybody, this is what i was looking for, great info so i dont have repeat what has been done by others before me. I learn something new every day just by coming to this site!...
