I am installing a set of wilwood reverse mount clutch/brake pedals in my 28 coupe that is channeled. In order to acheive a comfortable pedal position i need to cut about 2" out of the pedals. This will equate to an approx 5:1 pedal ratio I am running a ford 8" w/ drums in the rear 1" master, and the standard 11" disc in the front with a 7/8" master. 2 questions: Will the pedal ratio be sufficient? Can I safely cut and weld the wilwood aluminum pedals? ( I have a qualified tig welder that would/will be doing the cutting/welding). I have a few pictures later Thanks Heres the pedals 6.25:1 out of the box:
Hey sorry can't answer your question about the ratio but where did you get those and how much were they? Thanks
am making a suggestion without seeing a photo your underdash space: raise pedal ***embly &use remote reservoirs???
Wilwood offers a 5:1 pedal. See if you can swap. If not, buy just arms. I would not trust welding an aluminum brake arm.
If you aren't picky, and particularly if you are going to hack them up, used Wilwood and similar pedals are all over fleaBay from race teams. 5:1 seems awfully low, particularly since you aren't going to run power brakes. http://v8****rel.com/_i/V8****relBrakeCalculationWorksheet.xls That is a simple Excel worksheet I created. Go to the force tab. You can erase the data that is in there, plug in your own, and compare it to other known setups. You will have to keep to unboosted setups to have it mean anything, but that should give you a fair indication if you are in the ballpark. It works only on discs, so you will have to ignore the rear. Just stop at line 28. You will need to know the piston diameter for your calipers. I cannot recall a setup that uses a larger master for the rear than front, but then again, drums are kind of a mystery to me. Hanging pedals are 7:1, 6¼:1, 6:1 and 5:1. Wilwood sells a 5:1 hanging pedal, part number 340-5180. Not sure if that will fit, but might be easier than cutting. I believe that the pedals are cast aluminum. I suppose you will know if that can be welded or not. If not, perhaps copying this as an alternative? http://colemanracing.com/store/shopexd.asp?id=5506 Since 5:1 is an off-t******lf ratio for Wilwood, I would imagine they could tell you if your system would work with them or not.
Actually that picture I posted is the wrong one I have the metal master cylinders. I am out of room as far as raising the ***m it's hitting the top of the tank/ cowl. The pedal position is in the arch ov my foot now. I'll answer the other questions and post a picture when I get back to the house
Thanks for the info guys, below are a couple photos showing what im doing the bracket will come off the hoop to hang the pedals. The plan is to give wilwood a call first to see what they suggest, and if their 5:1 pedals are any shorter
Just checked on wilwood site, looks like the 5:1 pedal ***m. is about 1.86" shorter than the 6.25:1 set I have. So I guess that leaves the question if 5:1 is suitable for my application??
This has been my hot potato layely. Here's the deal. You can use any pedal ratio you want, so long as you match it with a master cylinder of the correct bore. In a nut shell, the short pedal will require a smaller bore master to achieve acceptable line pressures. I worked up a calculator on mine the other day and actually have a similar situation. The correct master for a 5:1, non-power is 7/8" bore. The 6.25:1 pedal would work better with a 1" bore. This is all ***uming you have enough leg to muster 120-150 lbs of force on the pedal. If you find that the pedal is a bit too hard with a 7/8" bore, you can go down to a 3/4" bore and achieve the same line pressure with less effort. Most people think the small bore masters feel mushy. They do with a 6-7:1 ratio. Use your 7/8" master with a 5:1 pedal and evaluate. If you need to adjust, you will have a basis for the decision. Here's a couple more threads on the topic: http://www.jalopyjournal.com/forum/showthread.php?t=438400&showall=1 http://www.jalopyjournal.com/forum/showthread.php?t=440709
The only thing I would add is that as you decrease MC piston dia, you also decrease the volume of fluid displaced per unit of pedal travel. A 1" MC will move more fluid in 1" of pedal travel than a 3/4" MC would, and so on. I've never had this be a problem with disc brake systems, but you'll want to check how much stroke your drum cylinders require and then run the numbers on the volume of fluid required to move them that far. If you have 1" wheel cylinders that need a half inch of stroke each, that's ~0.785 cu in of fluid volume. If you have a 3/4" master cylinder, you'd need ~1.78" of stroke to displace that much fluid. That's getting right to the edge of what you can get out of that master cylinder and pedal set-up, which is why the pedal can sometimes feel mushy. Not saying it can't work, I'm just saying you need to check your volumes to be sure. The good news is, that's something you can do mathematically, before you spend any money on parts.
CH, that's exactly the exercise I was going through on my sanity check thread. The wheel cylinders may have a half inch stroke, but they only use a fraction of it. In drum brakes, the factory spec is often .025 slack on the initial adjustment. (that is, the pads are measured and adjusted to the ID of the drum minus .025) Then they can usually be tightened slightly. So if the shoes back off maybe .030 in the middle, the necessary stroke at the wheel cylinder would be double that, .060. Add the other side of the same wheel cylinder, now .120 effective stroke used. It's the disc up front that eat up the volume. I did the math on my 2.5" piston calipers and found that the typical master has 3 times the stroke volume over what the calipers and wheels should use under normal cir***stances. You have to go way under 1" on the master to narrow that margin.
Ok, a little update on this. I spoke with the tech folks at Wilwood today about my setup and how it would work/feel with the 5:1 pedals and the master cyl. sizes I currently have. He said that everything should work well together and that I would have a "firm" pedal. The only thing he recommended I might change is to a 7/8" master cyl for the rear drums. He felt I could most likely get it to balance out well with by adjusting the balance bar, but if I didnt like the feel, the way it stopped, etc to change to the 7/8. So I got the 5:1 pedal ***m. ordered and hopefully the 1.8" difference in pedal height will get me a more comfortable pedal position.
We've shortened a couple sets for racecar applications and had no problem at all. Our peddles were aluminum and when welding them we just sleeved the shaft with a piece of rectangle aluminum stock and tig welded them. very strong and no effect on performance.
Have you thought of the bracket to hold it to the roll bar yet? Think a flat piece coming off the pipe would be strong enough?
Hi guys, you would really want about a 7:1 ratio, in a panic stop your leg and foot applies about 100 to 125 lbs of preasure, at the wheels with a 7:1 ratio you will get about a 1000 psi spike and then drop to about 700 to 800 lbs constant preasure. You want to make sure you dont have much less than that. Todd
Yeah the brackets are done, the bracket for the brake ***m. is the same for each pedal ratio offered. I had them built based off the set I have.
I called the Wilwood tech line and they told me what to use. This was for '40 Ford drum brakes front and rear on an 8" channeled car. I used the 5.1:1 arms, 1" bore for the front and back brake master cylinders with a bias balance bar and 3/4" bore for the clutch master cylinder. The bias balance bar is set at neutral. I also shortened the swing arms about 1-1/2 inches. I also bought two Ford replacement brake pad rubbers and made aluminum plates that the covers will slip over. The plates were welded to the shortened swing arms and gusseted for strength. The Ford covers make the swing arms look less like a race car piece and have more surface area for my big feet to hit. I had the aluminum swing arms shortened and the plates added by a certified welder at a race ch***is shop. The swing arms and pedals are a tight fit on each side of the steering column and the three master cylinders barely fit under the dash. So far this set up has worked flawlessly even in a panic stop.
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