• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Brake m/cyl diameters for race set-up?

Share this page

B

BuggerAll

Jedi Hopeful
Offline
I'm converting to rear disk setup on the Spridget H-car. I decided to simultaneously upgrade the brake m/cyl set-up from a tsock twin-circuit sylinder to a Tilton-style, with separate m/cyls for front and rear brakes, hanging the clutch m/cyl off the side of a stock pedal box a la Speedwell. What cylinder diameters are people using for the dual m/cyl set-up?

I was thinking the baseline would be 3/4" - 3/4". Wilwood cylinders look to be more economical than Girling, plus they come with the mounting options in a kit - remote reservoir v. reservoir mounted on cylinder, etc.

Thanks for any help on this -

nr. 0 Hprod
 
I like the 5/8" - 3/4" - 3/4" arrangement for front, rear and clutch respectfully. This has worked well from both a pedal effort perspective and a braking effectiveness perspective. My Spridget uses the stock pan as well with an adapter plate to orient the mounting holes for the brake masters and has side mounting of the clutch master.

I also use an in-line Wilwood Bias valve on the line to the rear. The bias bar on the brake pedal is not easily-adjustable. This has worked well on both disk/drum and disk/disk systems. The rear disk setup I use is a custom setup which mounts the rear disk to the back of the double bearing hub. I don't have to remove the rotor hat or caliper to change diffs. Saves a good bit of time.

The 3/4 clutch master moves a little bit more fluid than stock and helps with selecting release arm pushrods and getting clutch release and engagement where I like it. The pedal is a bit stiffer, but that's okay.

I've got a mix of Wilwood and Girling cylinders. All mine are integral reservoir.

HTH,
Mike Miller
 
Hi Mike - thanks for the info. I think I'll try a pair of 3/4" cyls to begin with and have a 5/8" on hand as well so I can experiment. I am installing a WC rear disk setup with Wilwood calipers, so I'm hoping for good results. Last season I had a lot of problems using the disk/drum setup, in order to maintain stability under hard braking I had to adjust the bias very much forward. I hope with the disks in the back it won't be so twitchy with a little more rear brake. I have some corner weighting issues to contend with as well. In fact, had quite a few teething problems in my first season back in 35 years. Hopefully the more sophisticated braking setup will help build in some more smooth -

Mike MacQ 0 Hprod
 
You normally use a smaller bore on the front, because a smaller bore creates more pressure for the front, I'd follow Mike's suggestion. You only need about 10-15% rear brake bias, just enough to keep the rear of the car from coming around under hard braking, anymore than that and you get yourself into trouble real quick.
 
Thanks for the follow-up, Hap. I was thinking that since the standrad cyling bore is 3/4" I would start with that for the fronts, but given the inputs here about the 5/8" bore I will start with that as a baseline. Testing day before the first race of the season next year will be pretty busy, it looks like. I'll have a whole bunch of new things to dial in. Think I'll start a new thread about weight-jacking.
 
I brake more on the rear end so I use a F/R/C = 5/8";5/8";3/4" with lots of bias to the rear end.
DSC01285.JPG


Too large masters give too high brake pedal forces.

Cheers
Chris
 
Nice installation, Mad Marx. I think the twitchiness I get under hard braking when I use more rear brake bias may be due to the fact that I am running a locked (welded) rear end. I must say, from the photo it looks like the balance bar on your set-up has a lot of pre-load on the (rear?) center cylinder -
 
I use a welded diff too and I like the car to slide into the corners like a motorbike. I never had a lock on the rear.
The rear end is not preloaded. The length of the push rods are different because the front end needs more brake fluid moved than the rear. If you apply the brakes the bar will be perpendicular then and the ratio you've set will be there.

Cheers
Chris
 
Back
Top