Brake Cylinder Question??

[Robert101]

Hi,

I have a 1999 2500. I have read where some folks are putting larger better wheel cylinders in the rear brakes.

I am not clear on what kind of cylinders they are using, part numbers, availability, and if any modifications need to be perfomed... . ???



Also, I am looking at getting speed bleeders. Are they the same size for the smaller cylinders, as the large ones??



Thank You for your help. Any info will be appreciated. .



Robert

 

[Robert101]

Whoops

Sorry,

i posted this to the 1st gen site. . someone may be able to help anyway. . I will wait before I post to next gen. .

Sorry for the Faux Paux.

Robert

 

[Greenleaf]

We had just discussed this very same topic a day or so ago. The (1st gen trucks) have either 1" or 1. 5" wheel cylinders. The 250 truck employs 2. 5" rear shoes and the 350 trucks employ 3. 0" shoes. Some of the 250 trucks guys will convert to the larger wheel cylinder when converting to the larger (wider) rear shoes.



Some..... 'er, I mean, a great deal of argument has been brought to the table about the effects of employing a larger cylinder. I still need to know if the master cylinder is the same for both truck models... ... . anyone... ... .



As far as conversion difficulties. There are none. The new parts bolt into place.



I might add, that I know nothing about the 1999 model outside the engine of corse. I have nine ISB engines here in the stables.



GL

 

[JLEONARD]

The (1st gen trucks) have either 1" or 1. 5" wheel cylinders

I'm not sure of the above... when I did my rear brakes 4 years ago, my son ordered every size cylinder that was in the parts book list for a 91 250 or 350.

I remember there was a 7/8", 1" ,and 1 1/8" I believe. I'm talking ID here. Mine was the 1 1/8" ... at least that was what was on the truck as stock.

1 1/2" seems awfully large to me.

Jay

 

[Greenleaf]

I think you are correct. It's 1 1/8" that the 350 rigs use. Just for fun, I'll call my NAPA supplier to learn just how many differnt wheel cylinders are offered as well as the master cylinder part number or numbers available.

 

[Ggg]

My 91 DRW had 1 1/8" bore wheel cyls. and the "upgraede" GM ones I used are 1 3/16" bore.

 

[HFletcher]

Hi all! I don't know how to post a link, but I recently came across another forum which I think hits the nail on the head regarding rear brake upgrades: //www.nwbombers.com/forum/index.php?showtopic=12826&st=0:

 

[tugboatphil]

HFletcher,



If you would have put http: right before the rest of what you had, you would have had it come out as a link.

 

[cerberusiam]

I used the 1 1/8" wheel cylinders ad the 3" shoes when I redid my brakes and they fit correctly. According to the Wagner book the part # for the 3/4 and 1 ton MC's are the same. That would indicate the MC should flow enough to feed the larger wheel cylinders adequately. In a practical application I did notice better braking with the bigger cylinders and shoes, but, how much is due to driving it with worn parts and fixing it or actual better braking is pretty subjective. I did find I had to replace the master cylinder to get the full effect though. In all fairness my truck has always had decent brakes even before I started working on it. I have not had the problems with the RWAL that others have had and even towing a trailer never saw any braking problems, but, after warping 2 sets of front rotors there was an obvious problem witht he rears.



The 1 3/16 GM cylinders are kind of a no-mans-land as far as the efficacy. I have not found a concrete answer about whether they are too big for the MC or just fine. I think the differences, if they could be defined, would probably fall under the heading off "nit-picking" and would not be even be noticed 99% of the time. FWIW thats my . 02

 

[EZGZ]

I have some experience with wheel cylinder size and there effects from working on my VW dune buggy.



Normally most of the braking is done by the front because the weight shifts there as you brake when moving forward anyway.



The bigger the wheel cylinder compared to the master cylinder the more power you get. That is why before disc brakes they had larger wheel cylinders on the front than the back.



Since my dune buggy kit car has virtually all the weight on the back the front wheels would lock and skid when I came up to stop signs to quick. I read an article about swaping the front wheel cylinders with the rears and it cured my problem very nicely. Having larger than stock tires on the rear probably helped. Some folks only run brakes on the rear and all this is done with a standard master cylinder.



Most after market brake company's would recomend a larger master cylinder if you purchased a disc brake kit for these kit cars because it usually takes more fluid to operate them. I found that I had to push a lot harder to lock my rear wheels and went back to the smaller master cylinder 7/8 to3/4 and it gave me a lot more stopping power with less effort.



Now coming back full circle to our trucks. If you go with the 3 inch pads alone you would have longer life and a bit more stopping power. If you increase the size of your wheel cylinder you will really start changing the bias and you will get more power to the rear I think on my buggy it was going from 19MM up to 22 MM that made a noticeble difference but keep in mind I was swaping front to rear cylinders and changed tire size so maybe I just got lucky.



A final observation is that you might not need to get a bigger master cylinder because we are only dealing with the rear drum brakes and as long as you adjust them or they self adjust you really won't be needing that much more fluid to operate them ounce there in adjustment.



Brakes are a real touchy subject because of legal liability. I am not suggesting anyone follow my example but I am just now facing the issue with my trucks rear brakes and mixing information I gained here and adding some of my own. I feel very comfortable working on my brakes and am looking forward to stopping that front end shudder and wear from my fronts.



I think it goes with saying that I will be illimitating the ABS feature in the process and if I ever sell my truck I will put it in writting and keep a signed copy from the buyer that he is aware of the changes.



Hope this helps some folks on the edge of understanding.

 

[Greenleaf]

That's a good point about making the potential new owner aware of changes.



-S