Holbert Brake upgrade project. Big red, without the red.
12-14-2008, 07:59 PM
#16
Three Wheelin'
those calipers have been exposed to some major heat and corrosion. If i remember, my very first pictures of the cars underbody were shots of the brake area and it looked similar to this. I wonder if it was from the original salt exposure from the Bonneville speed runs? the calipers are pretty clean, just stained and there is a lot of heat marks on them. Scots are even worse. He is kind of keeping up, and doing it with the smaller rotors and the single piston caliper S brakes. 
. He turns those pagid orange in to moon dust.
mk
. He turns those pagid orange in to moon dust.mk
... now, try some wheels cleaner ( acid) for aluminium.... let it bite a time and steam high pressure it of... remember, the shinyer it is , the more it will radiate heat to the air ... .... that dust and corrosion is as a insulation layer to the ambient air... which is his only refrigerant medium ! 
12-14-2008, 08:05 PM
#17
Mark,
BTDT, it's OK to open up the radius of the caliper a little. On my last
project I started with the 993 TT calipers and machined the edges out
a little so i could fit in a 350 mm rotor (13.75") anyway, the same thing
can be done with the S4 caliper, you won't get the same diameter as you
would with a big red but you'll still gain a lot. And, Mark A. can get you the
seals to rebuild those calipers. And do replace those oem lines with SS ones..
BTDT, it's OK to open up the radius of the caliper a little. On my last
project I started with the 993 TT calipers and machined the edges out
a little so i could fit in a 350 mm rotor (13.75") anyway, the same thing
can be done with the S4 caliper, you won't get the same diameter as you
would with a big red but you'll still gain a lot. And, Mark A. can get you the
seals to rebuild those calipers. And do replace those oem lines with SS ones..
12-14-2008, 09:56 PM
#18
Rennlist Member
Thread Starter
Joe, (Bump) ,
can you post a picture of the final caliper after it has been machined?
Why would I not be able to have exactly the same diameter as the GTS? That is exactly the plan. to move the caliper out exact the 9mm bigger radius, to equal the GTS rotor size and caliper position. am i missing something?
S4 304mm, GTS and 993TT 322mm and you went 350? thats big!
mk
can you post a picture of the final caliper after it has been machined?
Why would I not be able to have exactly the same diameter as the GTS? That is exactly the plan. to move the caliper out exact the 9mm bigger radius, to equal the GTS rotor size and caliper position. am i missing something?
S4 304mm, GTS and 993TT 322mm and you went 350? thats big!
mk
Mark,
BTDT, it's OK to open up the radius of the caliper a little. On my last
project I started with the 993 TT calipers and machined the edges out
a little so i could fit in a 350 mm rotor (13.75") anyway, the same thing
can be done with the S4 caliper, you won't get the same diameter as you
would with a big red but you'll still gain a lot. And, Mark A. can get you the
seals to rebuild those calipers. And do replace those oem lines with SS ones..
BTDT, it's OK to open up the radius of the caliper a little. On my last
project I started with the 993 TT calipers and machined the edges out
a little so i could fit in a 350 mm rotor (13.75") anyway, the same thing
can be done with the S4 caliper, you won't get the same diameter as you
would with a big red but you'll still gain a lot. And, Mark A. can get you the
seals to rebuild those calipers. And do replace those oem lines with SS ones..
Last edited by mark kibort; 12-15-2008 at 03:22 PM.
12-14-2008, 10:55 PM
#19
Former Vendor
Join Date: Feb 2004
Posts: 2,139
Likes: 0
Received 0 Likes
on
0 Posts
Mark,
At your level of racing and brakes being so important, why not sell your S4s and buy a set of big blacks? I can understand the engineering exercise here and the challenge of doing this but it's about time for a fresh set of front brakes, no?
Constantine
At your level of racing and brakes being so important, why not sell your S4s and buy a set of big blacks? I can understand the engineering exercise here and the challenge of doing this but it's about time for a fresh set of front brakes, no?
Constantine
12-14-2008, 11:01 PM
#20
Nordschleife Master
Seriously i dont trust cut up lug nuts to hold my brakes on a little crappy 50 hp honda, let alone a 928, let alone let alone a 928 thats being raced.
The calipers look like they need to be torn down so why not just sell those calipers as a core rebuild, and buy the big blacks?
Im sure there is a method to his madness
12-14-2008, 11:09 PM
#21
Rennlist Member
Thread Starter
As soon as i find a fresh $1000 bill 
, Ill have to make due and monitor them carefully.
But yes, i would be nice to have a new set of brakes up front for the upcoming racing season.
mk
, Ill have to make due and monitor them carefully. But yes, i would be nice to have a new set of brakes up front for the upcoming racing season.
mk
12-14-2008, 11:16 PM
#22
Rennlist Member
Thread Starter
Thanks.
Again, those cut up lug nuts are actually pretty good material, but no, they wont be the finished product. a larger piece to extend the contact patch to what is seen normally, will be used and probably a dense aluminum or steel washer will be used. (we are talking .35")
Those calipers are plenty. again, if you see the pads of some real fast pro racers, they are not much different. again, the S4 pad is almost identical to the F50 ferarri pad.
I dont know what the mode of failure of these brakes are, but i suspect it would be something like leaks or pulling to one side, under braking. Like most things on this car, it usually looks pretty good on the inside, but bad on the outside. when I bled the fluid, it always looks very clean, even after a good cooking
mk
Again, those cut up lug nuts are actually pretty good material, but no, they wont be the finished product. a larger piece to extend the contact patch to what is seen normally, will be used and probably a dense aluminum or steel washer will be used. (we are talking .35")
Those calipers are plenty. again, if you see the pads of some real fast pro racers, they are not much different. again, the S4 pad is almost identical to the F50 ferarri pad.
I dont know what the mode of failure of these brakes are, but i suspect it would be something like leaks or pulling to one side, under braking. Like most things on this car, it usually looks pretty good on the inside, but bad on the outside. when I bled the fluid, it always looks very clean, even after a good cooking
mk
thats what everyone has been saying!
Seriously i dont trust cut up lug nuts to hold my brakes on a little crappy 50 hp honda, let alone a 928, let alone let alone a 928 thats being raced.
The calipers look like they need to be torn down so why not just sell those calipers as a core rebuild, and buy the big blacks?
Im sure there is a method to his madness
Seriously i dont trust cut up lug nuts to hold my brakes on a little crappy 50 hp honda, let alone a 928, let alone let alone a 928 thats being raced.
The calipers look like they need to be torn down so why not just sell those calipers as a core rebuild, and buy the big blacks?
Im sure there is a method to his madness
12-14-2008, 11:52 PM
#23
Nordschleife Master
hey its your car do what you want
when you mentioned a spacer though i was imagining something much different then what your planning which is basically just a fat washer. I would look at a plate thats going to be allot more rigid and support the entire caliper rather then just using a couple washers.
when you mentioned a spacer though i was imagining something much different then what your planning which is basically just a fat washer. I would look at a plate thats going to be allot more rigid and support the entire caliper rather then just using a couple washers.
12-15-2008, 12:37 AM
#24
Rennlist Member
Thread Starter
I thought that too, until i looked at how the calipers mount to the hub. (just two simple 1" diameter contact points with a big fat bolt holding it to the hub assembly.
I could run a piece of 6061 (or steel) bar stock across both holes if that would help or be better and safer.
mk
I could run a piece of 6061 (or steel) bar stock across both holes if that would help or be better and safer.
mk
hey its your car do what you want
when you mentioned a spacer though i was imagining something much different then what your planning which is basically just a fat washer. I would look at a plate thats going to be allot more rigid and support the entire caliper rather then just using a couple washers.
when you mentioned a spacer though i was imagining something much different then what your planning which is basically just a fat washer. I would look at a plate thats going to be allot more rigid and support the entire caliper rather then just using a couple washers.
12-15-2008, 06:48 AM
#26
Here's a good set of pads for you, the RS 29 pads seem to offer what you are looking for, they transfer less heat into the caliper, http://www.pagid-brake-pads.co.uk/pr...ist.php?md=169
Some more details of all of the Pagid range, i was supplied The Pagid RS4-4 with my Ferrari F50 conversion kit. They are great on the street and quite, hope they are good on the track too, I have heard they are good. http://www.pagid-brake-pads.co.uk/products/index.php
Greg
Some more details of all of the Pagid range, i was supplied The Pagid RS4-4 with my Ferrari F50 conversion kit. They are great on the street and quite, hope they are good on the track too, I have heard they are good. http://www.pagid-brake-pads.co.uk/products/index.php
Greg
12-15-2008, 06:58 AM
#27
Addict
Rennlist Member
Rennlist Member
I thought that too, until i looked at how the calipers mount to the hub. (just two simple 1" diameter contact points with a big fat bolt holding it to the hub assembly.
I could run a piece of 6061 (or steel) bar stock across both holes if that would help or be better and safer.
mk
I could run a piece of 6061 (or steel) bar stock across both holes if that would help or be better and safer.
mk
As I said in earlier post the force on the bolts (except bending due to the relocation of the caliper outwards) will actually reduce unless you increase the available retardation ie even bigger tyres.
The oem bolts are only G8.8 - change them to G12.9 and you shouldn't have any problems.
12-15-2008, 11:34 AM
#28
Rennlist Member
Thread Starter
Im not worrried about heat transfer, im trying to improve the braking capacity.
the RS-29 pads are endurance pads (not the direction i was lookng to go) . the only options in the pagid line would be the step up in temperature capability and braking force at high temp which would be the RS-14s (pagid blacks ) or even the pagid greys. It sounds like they are near the performance of the Hawks HT10s or 14s which are a huge improvement ive been told by some top WC guys and BMW club guys, over the oranges for just the things I need to fix in the braking performance area. They are also kind to rotors, if you can believe that.
The larger rotor will give more heat disapating capabilites
mk
the RS-29 pads are endurance pads (not the direction i was lookng to go) . the only options in the pagid line would be the step up in temperature capability and braking force at high temp which would be the RS-14s (pagid blacks ) or even the pagid greys. It sounds like they are near the performance of the Hawks HT10s or 14s which are a huge improvement ive been told by some top WC guys and BMW club guys, over the oranges for just the things I need to fix in the braking performance area. They are also kind to rotors, if you can believe that.
The larger rotor will give more heat disapating capabilites
mk
Here's a good set of pads for you, the RS 29 pads seem to offer what you are looking for, they transfer less heat into the caliper, http://www.pagid-brake-pads.co.uk/pr...ist.php?md=169
Some more details of all of the Pagid range, i was supplied The Pagid RS4-4 with my Ferrari F50 conversion kit. They are great on the street and quite, hope they are good on the track too, I have heard they are good. http://www.pagid-brake-pads.co.uk/products/index.php
Greg
Some more details of all of the Pagid range, i was supplied The Pagid RS4-4 with my Ferrari F50 conversion kit. They are great on the street and quite, hope they are good on the track too, I have heard they are good. http://www.pagid-brake-pads.co.uk/products/index.php
Greg
12-15-2008, 11:42 AM
#29
Rennlist Member
Thread Starter
That was the plan, go to a near interference fit with the spacers. is there a need to make it out of one bar for both holes?
Also, your right about the forces going down. Im only trying to get more braking force at the calipers for better modulation when the pads start to get real hot. The high temp rated pads should give more bit when they get in the 1200 degree range as they are rated. Currently, padig oranges are rated to fade in the 1000 degree range.
It would be interesting to get some kind of telemetry output of the braking system to see what kind of braking pressures are created at the different track speeds during threshold braking.
mk
Also, your right about the forces going down. Im only trying to get more braking force at the calipers for better modulation when the pads start to get real hot. The high temp rated pads should give more bit when they get in the 1200 degree range as they are rated. Currently, padig oranges are rated to fade in the 1000 degree range.
It would be interesting to get some kind of telemetry output of the braking system to see what kind of braking pressures are created at the different track speeds during threshold braking.
mk
If you can machine a single piece of 6061 so that the bolts are nearly an interference fit then you will almost alleviate any bending in the bolts - Good.
As I said in earlier post the force on the bolts (except bending due to the relocation of the caliper outwards) will actually reduce unless you increase the available retardation ie even bigger tyres.
The oem bolts are only G8.8 - change them to G12.9 and you shouldn't have any problems.
As I said in earlier post the force on the bolts (except bending due to the relocation of the caliper outwards) will actually reduce unless you increase the available retardation ie even bigger tyres.
The oem bolts are only G8.8 - change them to G12.9 and you shouldn't have any problems.
12-15-2008, 02:26 PM
#30
Rennlist Member
I would lean toward a steel plate per axle rather than two spacers per axle. If you use parts that are machined precisely so that the contact faces are parallel it probably won't make much difference, but IMHO a single piece would be stronger so why not. +1 on the stronger bolts, also burnish the contact faces down to bare metal. The oxidation buildup in there may prevent the surfaces from mating precisely, especially with a clean spacer in between, that buildup will lead to a greater reduction in rigidity of the assembly than precisely-milled spacers would with the surfaces cleaned up.