Plus two brakes with bolt-on hubs

[CBUEB1771]

I can take an angle grinder to the rod end to radius the sharp top edge

Andrew,
I would be very cautious about taking a die grinder to the steering ball joint. The steering forces end up as hoop stress in the forging you are about to attack. If there are only forging marks to remove you might be OK. I would think about other ways to move the disc outboard just a bit. You could machine a bit off of the back face of the hub where the disc mounts and then shim the calipers outboard a bit. Unfortunately you'll be looking for 0.01" here and 0.01" there.
Russ

[paddy]

Do these look like they will help?

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 0334986870

Paddy

[RotoFlexible]

Russ: Point taken. Turning the rotors will get me a little more clearance. I could have the shop take additional metal off the inside. Tom at Dave Bean mentioned that they deliberately thin the discs to work with racing calipers, so this may be a reasonable option. Unfortunately, I can shim the calipers inwards but not outwards... I sent the photo to Tom, waiting to see what he recommends. It's only that sharp corner that needs to be relieved.

Paddy: If the 26R arms shift the tie rod end slightly inward, then yes those would help (as would shimming my arms inwards, away from the rotor). Otherwise, no.

[RotoFlexible]

The new brakes are in place but not yet bled or tested (roads too crummy). After the rotors were turned, I took a file to the offending tie rod end and was able to eliminate the interference by rounding off the upper contour. It is only a problem on one side - very tight clearance on the other, but no interference.

I ordered the wrong pistons and seals. The calipers I installed have "16P" on the castings but are actually the later 16PB, which take a different type of seal. If in doubt, refer to the +2 parts manual at rdent.com. Ray swapped them so I only had to eat the shipping.

I was able to hook up the banjo bolts on the existing brake lines to the new calipers without difficulty.

[RotoFlexible]

I finally got to test the big brakes. They work well and give me a little more stopping power for the same push - just what I was looking for. They are also smoother than the old brakes - I guess the old rotors were slightly out of true.

There is still a little air in the lines that I haven't been able to bleed out yet, so there is some initial pedal travel. Once that is taken up, the pedal is not as rock-hard as previously - it has a more progressive feel. The stop is very sure, straight, and easy to modulate. Once I sort out the bleeding problem, I think I am going to like these a lot.

[Lincoln62]

Those tie rod ends seem pretty blocky looking compared to others I have seen. If there are different brands available you may even find a suitable tie rod end that has a slightly different profile and doesn't rub.

Peter
66S2

[worzel]

Hi

Whilst on this subject- regular readers might recall "teething problems" I was having with a plus brake conversion on a sprint. Switching to softer pads cured that but I was curious if anyboby else had upped the size of the master cylinder from 0.7 to 0.75 (same size as a TR6 I believe).

Only reason for asking is that pedal travel must increase with the larger plus 2 pistons (by what percentage I don't know since I don't know the size of plus 2 pistons compared to the std sprint ones. Presumably a switch from 0.7 to 0.75 would increase pedal effort by 1/14 th and reduce travel by the same amount.

Any comments?

John

[paddy]

Since it's the area of the m/c piston that counts rather than the diameter, the difference will be nearer to 15%.

Paddy

[ncm]

Girling indicate the size of the caliper piston used by the type number...in 1/8" increments. Hence the type 14 caliper you have removed has a piston diameter of 1 3/4" (14/8") and the replacement type 16 uses a 2" piston.

Brian.

[CBUEB1771]

Girling indicate the size of the caliper piston used by the type number...in 1/8" increments. Hence the type 14 caliper you have removed has a piston diameter of 1 3/4" (14/8") and the replacement type 16 uses a 2" piston.

Brian.

Actually the pistons of the Type 14 calipers have 1.893" diameter and the Type 16 are 2.125". This is covered in numerous sources (eg Dave Bean reference catalog). So the Type 16s have 26% more piston area than the 14s. Going from the 0.70" master to the 0.75" would recover just over half of the increased pedal travel needed to move the Type 16 pistons the same distance as a Type 14. That is not normally the goal, most people change to the larger bore calipers to get increased braking for the same pedal effort at the expense of some increase in pedal travel. The distance the pistons travel should not vary much by caliper type. This is governed by how far the seals like to pull the piston back and how far the discs push the pads back due to runout and axle deflection.

[gerrym]

Andrew, looking at your photographs of the brake hose connected to the PB16s or Plus 2 brakes.

All the plus 2 I have seen have used a section of hard line from the caliper to a bracket mounted off the hub. The hose then runs straightforward away from the spring before curving back towards chassis. I'm sure this was the factory routing. No banjo on the end of the hose, just another 3/8UNF threaded bubble seal.

I believe this minimises hose "whip" and keeps the hose away from the spring and suspension.
Regards
Gerry

[ncm]

I'll plead guilty to posting something that I've read on't net without checking it out first however I have since measured a genuine Girling type 14 piston at 48mm(1.889")diameter as noted above, but there is a generous radius between the o/d and the face,the flat area of which has a diameter of approx 44.5mm(1.75"), so would it be correct to conclude that the working area of the piston is 1.75" diameter?

Brian.

[paddy]

The "effective" surface area is always determined by the outside diameter of the piston, at the point that it contacts the seal, irrespective of the shape of the surface at the rear of the piston; this is what determines the volume of fluid displaced by the piston as it moves.

Paddy

[RotoFlexible]

Most people change to the larger bore calipers to get increased braking for the same pedal effort at the expense of some increase in pedal travel.

That was my goal. The increased braking is certainly there and the pedal is more progressive (a positive spin on "increased pedal travel)."

All the plus 2 I have seen have used a section of hard line from the caliper to a bracket mounted off the hub. The hose then runs straightforward away from the spring before curving back towards chassis. I'm sure this was the factory routing. No banjo on the end of the hose, just another 3/8UNF threaded bubble seal.
I believe this minimises hose "whip" and keeps the hose away from the spring and suspension.

True. I don't think the plus 2 calipers I bought included the bracket, and my nice new flex hoses are sized for the original arrangement. But the plus 2 setup is preferable for the reasons you state.