Riley 1.5 brake conversion

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moggiegeek
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Riley 1.5 brake conversion

Post by moggiegeek »

While stripping down and refurbishing a set of Riley 1.5 front brakes I discovered a curious assortment of wheel cylinders. It appears that they have all been rebored and then fitted with new pistons. I think....The bore is larger than genuine Riley 1.5 cylinders I have as NOS. Confusing. The internal seals are perfect but the dust covers are deteriorated. I want to replace these but does anyone recognise the girling numbers so I might be able to source a refurb kit. Numbers are
303210
412660
412660
303200W.
philthehill
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Re: Riley 1.5 brake conversion

Post by philthehill »

Doing an internet search Girling 303210 comes up as fitted to Healy 100/4 with 7/8" bore.

https://www.ebay.co.uk/itm/Brake-Wheel- ... SwqYRcxKMP

moggiegeek
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Re: Riley 1.5 brake conversion

Post by moggiegeek »

Thanks Phil, ordered new rubbers for 7/8 cylinders.
Riley cylinders are 3/4 dia so if if fitted the 7/8 cylinders would this ease the pedal pressure for the equivalent stopping power?
philthehill
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Re: Riley 1.5 brake conversion

Post by philthehill »

With the larger internal diameter wheel cylinder less pressure is required at the master cylinder to obtain the same pressure at the wheel cylinder. The larger piston of the wheel cylinder will result in slightly longer travel of the brake pedal as more brake fluid needs to be displaced to allow the wheel cylinder piston to travel the same distance.

paul 300358
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Re: Riley 1.5 brake conversion

Post by paul 300358 »

oliver90owner
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Re: Riley 1.5 brake conversi

Post by oliver90owner »

Pressure = Force/Area. Pressure is transmitted equally in all directions within a fluid, so exactly the same pressure at the master cylinder as at the slaves will be the order of the day!

Rearranging the above formula, Pressure*Area = Force.

Increasing the slave cylinder diameter has several effects.

There will be a larger force at the slave, if the area is increased. Work done at both ends (which is Force *Displacement) must also remain true, so for the same amount of work done at the brake shoe end, the master cylinder piston must move that much further for the same slave piston movement (obviously the liquid is incompressible so volume changes in each part must be equal).

Transmitting energy from the master cylinder to the slave cylinder is quite efficient, there normally being only relatively small pumping losses associated with hydraulic systems such as these! It is basically the increased force of the brake friction material against the drum (or disc), with no actual movement, which will generate the increased friction (braking action) at the wheel end.

That being said, too much force at one end of the vehicle can lock those wheels before the other end is providing much braking force. The most braking force is generally at the front, particularly as the downwards force increases on the front wheels as the front end becomes ‘heavier’ under breaking. The rears are still expected to derive optimum braking action to control the vehicle... it’s why F1 car drivers alter the brake balance for different corners/circuits.
IslipMinor
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Re: Riley 1.5 brake conversion

Post by IslipMinor »

Moggiegeek,

Yes, the 7/8" front cylinders will reduce the pedal pressure for the same braking effort, but, as has already been said it will increase the brake bias towards the front as well. What rear cylinders are fitted, and what rear drum diameter and master cylinder bore diameter do you have.

Will this information I have a brake design tool that will give the front/rear balance, pedal pressure etc.

As a general comment, whilst the Riley brakes are 9" diameter, the 3/4" cylinders are too small and need high pedal pressures to make the work. Also they result in too much rear brake effort, much the same as the original 7" Minor drum setup did.
Richard


philthehill
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Re: Riley 1.5 brake conversion

Post by philthehill »

When I had the Riley 1.5 9" drum brakes on the front of my Minor the rear brakes were still the 7" Minor. Only when I fitted the Marina disc brakes on the front did I feel the need to fit the Wolseley 8" brakes to the rear so as to balance up the braking.
I did not have a servo fitted or brake bias valve and never once did I feel the need to fit either. The car remained steady when undertaking very hard braking on both road and track - nor was it effected by rotational forces lifting the weight off the rear wheels.
I did fit the smaller internal dia master cylinder which raised the force generated at the wheel cylinders and raised the pressure on the brake linings very slightly - but every little helps.

Some fit the Mini rear brake pressure regulating valve into the Minor rear brake hydraulic system to limit the forces acting on the rear brakes.

http://www.minispares.com/product/Class ... |Back%20to

IslipMinor
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Re: Riley 1.5 brake conversion

Post by IslipMinor »

Some fit the Mini rear brake pressure regulating valve into the Minor rear brake hydraulic system
Yes they do!

After completing the restoration in 1998, which included fitting Metro-based front disc brakes, with the standard 7" Minor rear brakes, fitted with the later, smaller cylinders with 3/4" bore, I found that under reasonably heavy braking I could lock the rear wheels. Generally only one wheel locked, whichever was the lighter loaded, but more concerning was coming into roundabouts in the wet, where the rear could start to step out of line, if the braking was a bit heavy. We are NOT talking about maximum emergency stop type braking, just hard braking under 'enthusiastic' driving conditions!

I fitted a Mini rear pressure limiting valve, which shuts off the flow of brake fluid to the rear brakes, once a certain line pressure has been reached. To make the system more tailored to a Minor, I converted the valve to be adjustable, and was surprised how much I needed to reduce the rear brake line pressure to prevent lock-up. The MOT man comments every time that the rear brake performance under footbrake is much worse than using the handbrake - he does know why though!

The picture below shows the modifications needed to make the standard 'fixed' Mini rear valve adjustable:
Mini Pressure Limiting Valve.jpg
Mini Pressure Limiting Valve.jpg (53.92 KiB) Viewed 2520 times
Richard


moggiegeek
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Re: Riley 1.5 brake conversion

Post by moggiegeek »

I haven't decided which combination to fit yet. It has a standard brake master cylinder and Servo fitted currently on standard but completely refurbished minor brakes.
I have gathered and rebuilt bits over the years so I could have :
At the front: Riley 1.5 with standard cylinders, Riley 1.5 with 7/8 cylinders or Wolseley 1500.
At the back: Wolseley 1500.
The car will be a 1275 uprated as discussed previously and it has front antiroll bar and Koni's all round.
Best combination advice welcomed
IslipMinor
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Re: Riley 1.5 brake conversion

Post by IslipMinor »

Which bore master cylinder is fitted? The 948 engined cars were originally fitted with a 7/8" bore, and the 1098 had a 13/16" bore. I am not sure if the early 7/8" master cylinder is still available, but if the later smaller bore unit is fitted to an early car, then the pedal pressures will be lighter, but all will still work well!

The master cylinder bore size has no effect of front/rear balance, only on the pedal pressure required to operate the brakes.
Richard


philthehill
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Re: Riley 1.5 brake conversion

Post by philthehill »

Richard
The master cylinder fitted to my Minor is the later 13/16" internal diameter. The early 7/8" (14/16" internal diameter master cylinder is no longer available. The difference of 1/16" internal diameter may be small but it does make a difference.

Phil

paul 300358
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Re: Riley 1.5 brake conversion

Post by paul 300358 »

How will the diameter difference of the master cylinder alter the front back balance?
philthehill
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Re: Riley 1.5 brake conversion

Post by philthehill »

The brake line pressure/force will not alter between front and rear brakes - but changing the working diameter of the drums and/or changing the internal size of the wheel cylinders will effect and alter the turning forces required to slow the drum/wheel.
If the rear brake drums/braking forces were excessive the retarding forces could be so great as to lock the brakes/wheels which could unsettle the car and lead to the car spinning out of control.
Originally cars only had brakes on the rear axle but it was found that fitting brakes to both the rear and front axles made the cars better balanced which kept the car on a straight line when braking was undertaken.
The relationship between the forces required to slow the drum/wheel has to be balanced between front and rear brakes so as to give good straight line braking. Hard braking should not be undertaking when turning a corner - on the other hand hard accelerating through and out of a corner is acceptable and preferable to braking.
Having tried various combinations of braking - 7" front / 7" rear drums, 9" front / 7" rear drums, 9" front discs / 7" rear drums, 9" discs / 8" rear drums and both sizes of master cylinder for both road and competition use I consider the 9" discs and 8" rear drums without servo to be ideal for my requirements.

moggiegeek
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Re: Riley 1.5 brake conversion

Post by moggiegeek »

Given the different drum brakes I've got available what combination would give the best combination?
philthehill
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Re: Riley 1.5 brake conversion

Post by philthehill »

In descending order of preference and efficiency:-

(1) The best combination of drum brakes in my opinion / experience would be a full set of Riley 1.5 brakes - that is front and rear with 13/16" diameter master cylinder.

(2) If that cannot be achieved the next best combination is Riley 1.5 front brakes and Wolseley 1500 rears. 9" front drums and 8" rear drums with 13/16" diameter master cylinder.

(3) If that cannot be achieved the next best combination is Wolseley 1500 front brakes and Wolseley 1500 rears with 13/16" diameter master cylinder.

(4) If that cannot be achieved the next best combination is Morris 8" front brakes and Morris 7" rears with 13/16" diameter master cylinder.

(5) Last of all Morris 7" front brakes and Morris 7" rear brakes with either 7/8" or 13/16" diameter master cylinder.

philthehill
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Re: Riley 1.5 brake conversion

Post by philthehill »

Something is causing me problems editing the above post so have to make the comment below as a separate post.

I have not included the use of Morris Minor 8" front brakes and Wolseley 8" rear brakes as the more powerful Wolseley 8" rears could upset the bias between the front and rear 8" brakes therefore I have not included the 8" front and 8" rear combination.

The 7" front and 7" rear brakes are not powerful enough to cause a significant bias between front and rear brakes.

IslipMinor
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Re: Riley 1.5 brake conversion

Post by IslipMinor »

Phil, Do you have details of the Riley 1.5 rear brakes? Drum diameter, shoe size and cylinder bore diameter? I presume they are the same leading/trailing shoes set up as the standard Minor?

I will add it to the brake design model I have, and publish the whole set of results.
Richard


philthehill
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Re: Riley 1.5 brake conversion

Post by philthehill »

Richard
The Riley 1.5 rear brakes are either 8" or 9" dia with narrow brake shoes (brake shoe width is 1 3/4" wide x 8 3/4" long. These measurements need confirming as they are taken from the web and had a question mark after the measurements ).
You may be able to extrapolate the dia from the pictures below.

They are the same leading / trailing brake shoe set up as per the Minor.

The bore size of the Riley 1.5 rear brake cylinders is 3/4"

https://www.ebay.co.uk/itm/1958-1965-RI ... SwjKddva3Y

See also http://rileymotorclub.org/wp-content/up ... Spares.pdf

The bore of the Riley 1.5 brake master cylinder is 3/4".

Below are pictures of the Riley 1.5 rear brake set up.
Riley 1.5 rear brakes 1.jpg
Riley 1.5 rear brakes 1.jpg (328.75 KiB) Viewed 2395 times
Riley 1.5 rear brakes 2.jpg
Riley 1.5 rear brakes 2.jpg (215.63 KiB) Viewed 2395 times
Phil

moggiegeek
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Re: Riley 1.5 brake conversion

Post by moggiegeek »

Thanks Phil, final question is when fitting the Riley brakes as in option one would you favour the 3/4 or 7/8 cylinders?
This will mean there is a fully refurbed set of Wolseley fronts and Riley fronts which I could be persuaded to part with.
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