Landracing Forum
Tech Information => Technical Discussion => Topic started by: wickedwagens on February 17, 2014, 01:27:18 AM
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I'm putting the suspension back together and have everything to go either direction. 4 wheels disc or 4 wheel drum or any combination of the two. I was thinking that since you can not put a lot of stopping force to the salt there would not be much gain going to a disc setup. I was also thinking about possibly having less rolling resistance with the drum brakes. What are your ideas, recommendations, and experiences with this?
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I have no experience either way, but through out the course of my build, a lot of racers have told me that my rear disc brakes are over kill.
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Tom Burkland told me you can never have too much brake!
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You can retract shoes all the way, whereas discs tend to drag a bit.
I removed my front brakes and will be running rear drums only this year.
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I race bikes -- and take the time before runs to use a scraper or something to pull the pucks off the rotors. Ir's a bit of a pain - but showed some increase in top speed over a handful of runs for comparison. I don't have immediate braking that way -- have to pump the lever a few times, and that has caught me by surprise at Maxton :evil:, but at the salt there's no good need for brakes.
As for disc vs. drum -- I'd far rather have drum brakes on the pickup, for instance, because there are too many ways that the salt and crud will farkle with the sliding parts of the disc system. Drum brakes are easier to clean. I vote for drum brakes, adjusted for minimum drag.
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You can retract shoes all the way, whereas discs tend to drag a bit.
I removed my front brakes and will be running rear drums only this year.
What he said. :cheers:
Sid.
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I removed my front brakes and will be running rear drums only this year.
Chris, Are you going to make it to Wilmington before Speedweek and if so will this matter?
Gregg
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You can retract shoes all the way, whereas discs tend to drag a bit.
You can eliminate the drag by spot facing the disc pads with a small drill bit and running springs to knock the pads back. This is very common on road race cars. Tony
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If I were going as fast as Tom---I would agree--- but I am not so I opted for Drum less drag, and on the lakester aero also.
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You can retract shoes all the way, whereas discs tend to drag a bit.
You can eliminate the drag by spot facing the disc pads with a small drill bit and running springs to knock the pads back. This is very common on road race cars. Tony
Do you have more info on this as I'm having a hard time visualizing it?
Discs do drag and I've never liked that on the Stude. We've tried to pry them away before but it is a pain on that car and if the driver forgets just once in staging and presses the pedal that is lost. I'm going to try rear discs only on the lakester and since the calipers will be easier to get to, will pry them off but if the above will do that then I'm very interested.
Jon I'll have to disagree with you on the effects of salt on disc vs. drums. Way less parts with disc brakes. The year we ....
(http://purplesagetradingpost.com/sumner/hooley/2007-11.jpg)
.... ran through the water at the end of the road I had to completely rebuild the rear drums on the truck but the front disc's survived. Most all boat trailers now that have brakes have gone from drums to disc. Lots of parts to rust up with the drums. The problem with the discs is when the rotors rust up and then drag even more. They do have stainless steel rotors available for boat trailer brakes.
The whole thing still comes down to what Sparky said and that is how fast are you running and where. 250 on the salt is different than 250 at EM or one of the mile tracks, but you probably are going to have different chutes there also. Also are you driving a brick that wants to stop once you are out of the gas or a streamliner that will coast forever? Under 250 I for sure would not worry about front brakes and about anything will work on the back if you have the right chute for the car,
Sum
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Okay, Sum -- whatever works for you. I've had far more problems with the discs than with drum -- on my last three pickups. I understand about the number of parts, but what goes awry in the discs (mine) is that pads won't slide back and forth properly. The pins corrode and the pads lock into position. And yes, Nancy and I have driven the vehicles through similar lakes as the one shown in your photo. :evil:
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I forgot to add that I will be running 125-160 mph range.
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See Reply #3. Best for salt. Maybe not for airports -- although don't know what your speed would be in a mile.
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Tony, some photos of your spot face and spring trick will be a big help.
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Once, many years ago when we were drag racing we put springs between the pads to push them off of the rotors. When I went through the traps so as not to break out I hit the brakes and the car made an immediate Left turn and I darn near rolled it in the lights. The springs were removed before I made another pass.
Doug :evil: :cheers: :cheers: :cheers:
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I removed my front brakes and will be running rear drums only this year.
Chris, Are you going to make it to Wilmington before Speedweek and if so will this matter?
Gregg
:-o
I hadn't even given it a thought. The spindles and hubs are cut, and there's no going back at this point.
I guess if the rear drums will haul it down from 105-110 before I wind up in the hangar, I might still be able to run Wilmington.
Gregg, seriously - I hadn't even given it a thought . . . :oops:
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Bo and Sum, The springs are made of spring steel wire and there are two per caliper. Take a matching drill bit and spot face the pads to hook the end of the wire spring. The wire hooks on both pads (one wire spring on the front part of the pads and the other on the back part of the pads). It gives just enough force to knock the pads back of the rotor. The spring in the picture came from one of my friends in NASCAR and is very common for qualifying in NASCAR. They are not that hard to make. Tony
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Anyone who has ridden a dirt bike down a steep hill knows you can't stop or slow down without front brakes, You can't stop fast anywhere without front brakes. I learned this fast hill climbing on my 1st dirt bike. Going down the hill,appllied rear brake didn't slow much at all, steering and sliding like crazy out of control to bottom. Since learned to use front brake.
You bike guys know this :roll:
I've told this story before. Several years ago, before SCTA put a stop to it my cousins were doing a short test run away from course at El Mirage in there blown Chrysler Stude. Ed gave it a short blast and Sh.t NO BRAKES :-o Well it had brakes
on the rears only, and they were working, but they were not stopping the car, they were just locked up and sliding as if on ice.
JL222
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I hadn't even given it a thought. The spindles and hubs are cut, and there's no going back at this point.
I guess if the rear drums will haul it down from 105-110 before I wind up in the hangar, I might still be able to run Wilmington.
Gregg, seriously - I hadn't even given it a thought . . . :oops:
No need to worry about a hangar but there are steel poles that have the approach landing lights on them.
If you run off the end of the track, just be sure to steer left or right to miss them!!!!! :-o :evil: :-D :cheers:
Gregg
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No need to worry about a hangar but there are steel poles that have the approach landing lights on them.
If you run off the end of the track, just be sure to steer left or right to miss them!!!!! :-o :evil: :-D :cheers:
Gregg
Gregg, that's all fine and well - but the reason I removed the brakes was so I could lower the front end further - which required I choke off the steering so the wheels wouldn't rub in the fender wells.
:|
I guess I'll see how it works at Bonneville, and worry about Wilmington later in the season.
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It ain't like you're goin' 122 MPH.
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It ain't like you're goin' 122 MPH.
Something you've done backwards . . . :wink:
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On our roadster, I set it up with a double master cylinder using both ports, paired, to operate the rear drums. This lets the master cylinder pushrod move enough fluid while leaving the brake shoe adjustment looser. You may need to step down a size on the master cylinder bore diameter, or pedal pressure gets higher....probably not a big deal.
Two notes for this method: one, you need to ditch all the handbrake stuff in the rear drums (more stuff to rust), and two, it gets the shoes far enough back that you can still get the drums off after everything rusts on the way home!
I vote for rear drums because wheel cylinders are MUCH easier and cheaper to repair than calipers. (really easy when you throw away all that emergency brake stuff)
JimL
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It ain't like you're goin' 122 MPH.
Something you've done backwards . . . :wink:
Nice play Gentlemen. :wink:
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On our roadster, I set it up with a double master cylinder using both ports, paired, to operate the rear drums. This lets the master cylinder pushrod move enough fluid while leaving the brake shoe adjustment looser. You may need to step down a size on the master cylinder bore diameter, or pedal pressure gets higher....probably not a big deal.
Two notes for this method: one, you need to ditch all the handbrake stuff in the rear drums (more stuff to rust), and two, it gets the shoes far enough back that you can still get the drums off after everything rusts on the way home!
I vote for rear drums because wheel cylinders are MUCH easier and cheaper to repair than calipers. (really easy when you throw away all that emergency brake stuff)
JimL
So you run two lines out back - one for each wheel cylinder? Actually, that would be nice if you were to lose one side.
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Or...You could run a vacuum pump to the master cyl. and retract the pads ala` Penske
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I ran two into one right after the master cylinder, and then split again at the rear axle. I used extra long flexible hose at the backing plates, in a U shape turn, to allow pulling the axles far enough to change punkins without opening the brake lines on the salt. Poor mans quick-change.
This was a handbrake actuation, using a clutch pedal 'under-dash bracket' turned upside down for a pivot.
I am not a big fan of foot operated brakes in a salt-flats car. The fireboots are too big, the pedal is hard to reach during hand maneuvering in the pits, and its just one more obstacle to clean up the tracked in salt in the foot well.
Handbrake is easier to modulate when loading and unloading, and you can reach it through a window/door on the trailer. If you make it strong, (hence a clutch pedal bracket/pivot out of a pickup) you can have a side extension to get it even easier to reach during loading or pit maneuvering. We had the handle curved over so a short extension could slip on, for "outside" braking.
And no master cylinder where its hard to reach or exposed to underhood salt.
JimL
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"Something you've done backwards . . . "
Just rotating for panoramic camera shots.
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Never used any thing but rear drum brakes on 2 different cars. 140-215 mph. All emergency brake stuff removed. Can back them off so they never drag. Use a 7/8" Wilwood master cylinder and hand brake for the roadster and stock 1940 Chevrolet master cylinder for my coupe. Both are 1957 Pontiacs and I feel they are more aerodynamic than disc's. Opinion no proof.
Never went out the back door at El Mirage even when chute failed. I like the KISS method.......JD
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Thanks for all of the replies. It sounds like the disc brakes will not make it back on the car. I will run 4 wheel drum brakes and set them up for 0 drag.
Thanks again for all the help.
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Many of you that know me from the last 15 years on the HAMB know I harp on the CORRECT mix of MC and Wheel Cylinders combined with pedal ratio. The fact is, you need components matched. I use the Wagner brake bible and match up components for a good baseline that we can work from if needed.