Brake pedal adjustment

[OliveR]

Thanks for your reply Alan.

Just for info my car is a RHD GT40. So the brake lines are not in the same position that a LHD GT40. My master cylinder for front brakes is the one at the center (of the 3 master cylinders) meaning that the master cylinder for rear brakes is on the right.

Following what you said about the cable for the remote cross shaft I think I would need to turn the cross shaft in order to install the cable on the right of the pedal box.

I replaced my 3 master cylinders because the clutch and the font brake master cylinders were leaking so I decided to replace all. I bought exactly the same ones I had (same manufacturer - Wilwood / Same diameter).

I agree with you that before replacing the master cylinders all was OK and when reinstalling the cross shaft I didn't have any choices about the position as I have pin locks on both side of the cross shaft.

So I think the only solution is to bleed again the front brakes and check again the distribution of the front and rear brakes.

I'll let you again but many thanks again for all your helps.

OliveR

 

[Tim Kay]

Oliver,

I haven't read your whole post, so excuse me if this has already been addressed, looking at the picture you posted of the pedal assembly, brake bias bar, nuts and lock pins, correct me if I'm wrong, the bias bar looks like it's set to initiate the right m/c first thus more pressure. And if I understand correctly you're right master cylinder is the rear brake. If that's the case then your rear will receive more pressure than your front (all things being equal ie cylinder, calipers ect)

Is it possible you reversed the cylinder set up, front and rear, from its original position? It's possible your bar setting is correct if you swapped cylinder position.

 

[OliveR]

Tim... That's a good question !!! I'm wondering now when I disassembled the pedal box and the master cylinders if the brake lines were logically in front of their master cylinders (Front brake line connected to the center master cylinder and Rear brake line connected to the right master cylinder).

I've reinstalled like described below but I cannot remember how it was before ???

As your car is a RHD you know that rear brake line pass just on the right of the pedal box so that's why I've plug that line on the right master cylinder but is it correct ???

Don't tell me they had install the brake lines in contrast they should have !!!

All is possible nowadays I know...

I am in full doubt now !!

OliveR

 

[Tim Kay]

Oliver, my center master cylinder is the rear, my far right master cylinder is the front (Obviously the left master cylinder is the clutch).

This doesn't necessarily mean yours is the same but it's easy enough to simply follow the lines from the top of each master cylinder

Tim

 

[OliveR]

Tim, I'm sure I've well connected the brake lines to the correct master cylinders BUT the bias bar setting is not correct.

As Im' going to install a remote bias bar adjuster I'll need to turn the bar. I currently cannot install the adapter cable because it will touch the clutch pedal.

As Alan told below the bias bar ball must be closer to the front master cylinder in order to have better effort on the front brake. When you see my picture it seems to be ok but not enough.

I'll check that tomorrow.

I have to solve my problem quickly I'm going to test my GT40 on a racetrack October, 20...

By the way any of you plan to come to Le Mans Classic next year (4/5/6 of July) ? From my side I've already registered my car to test it on Le Mans 24hours racetrack.. (tested my Cobra last year but really want to test the 1966 winner...)

OliveR

 

[Seymour Snerd]

.

Just for info my car is a RHD GT40.

Ah! That changes the logic.... Now I understand much better your question about what side to put the cable on. And, which cylinder is front vs rear on my car would have no bearing on yours. Also, you've reminded me that the cylinder is connected to the hard lines by hose, and thus, at least in principle, you could have reconnected them in reverse from what they were (if the hoses are long enough.) So I'm learning more here than you. :laugh:

 

[OliveR]

Well I've played the contorsionist this morning but I'm happy !

I turned the cross shaft in order to be able to install the remote cable adjuster (when I'll receive it) and when reinstalling the cross shaft in the pedal I found that it was a little bit hard to insert it meaning that the cross shaft couldn't move as it should. I made the necessary and now that's perfect the cross shaft can move easily.
I've adjusted the cross shaft in order to have more pressure on front brake and I've tested on the road, my rear wheels don't stop anymore before the front wheels.
I now have to bleed again the front brakes (at first pedal pressure it's a bit soft and at the second pedal pressure it's hard meaning that I have air bubbles in the brake lines).

Many thanks to Alan, Tim, Michel and Dave.

Here is a picture of my installation now:



OliveR

 

[Seymour Snerd]

Great news; glad it's getting explained and fixed.

The only left over thing I'm wondering is why master cylinders are failing although your leaking symptom sounds different from Dave's no-bleed symptom. I'm assuming Wilwood has low-cost rebuild kits, so it might be interesting or worthwhile taking the old ones apart to look at and maybe rebuild. And of course I'd be curious what the insides look like...... not that I want to make extra work for anyone else....

 

[Tim Kay]

Alan,

Although my m\c are very low mileage (1,000) they were put into service around 2009. I was noticing when I changed the fluid a few weeks ago that not only was it extremely dirty but one of the m\c is weeping so likely I'll rebuild them soon. My thought was it could be due to lack of use.

Tim

 

[Seymour Snerd]

Alan,

Although my m\c are very low mileage (1,000) they were put into service around 2009. I was noticing when I changed the fluid a few weeks ago that not only was it extremely dirty but one of the m\c is weeping so likely I'll rebuild them soon. My thought was it could be due to lack of use.

Tim

Yes, not doing an annual (or so) fluid change could do them in.

 

[OliveR]

Alan, Tim, I get my car one year ago (October, 29) the day of my birthday (40 years old - what could I better expect for my gift ???).

I drove it 4300 miles this year and today the car has 8000 miles. I think the brakes and clutch fluids have never been replaced nor the master cylinders.

I'm going to try to disassemble one of my master cylinder and check/make pictures and post them for you Alan. When ? I don't know but in few times, I'll let you know.

By the way Alan, as I know that you really well know the SPF GT40, could you please give me the reference of the Front / Rear wheel bearings ? (Not going to replace them now but beginning of next year).
Just for info I noticed that the little bolts that keep tighten the wheel bearings have a too small head that don't allow you to tighten them as they should. I've replaced them by bigger heads and that's now perfect. At the beginning when I get the car I had to disassemble 3 times the driveshaft in order to re-tighten that too small bolts.
Maybe you have already made that modification...

Thanks,

OliveR

 

[Seymour Snerd]

By the way Alan, as I know that you really well know the SPF GT40, could you please give me the reference of the Front / Rear wheel bearings ? (Not going to replace them now but beginning of next year).
Just for info I noticed that the little bolts that keep tighten the wheel bearings have a too small head that don't allow you to tighten them as they should. I've replaced them by bigger heads and that's now perfect. At the beginning when I get the car I had to disassemble 3 times the driveshaft in order to re-tighten that too small bolts.
Maybe you have already made that modification...

That's one of the few areas I have not taken apart. :lipsrsealed:

There was a thread a long time ago about the stability of that adjustment and whether the rear upright and bearing arrangement was really a good idea (i.e. that it was imprecisely machined and adjustable, vs. using a precise spacer between the inner races of bearings which is then clamped at high force. I believe Holman and Moody (at least) make a spacer for the rear bearings but the last time I spoke them about it you send them your rear upright and they custom fit the spacers. At the end of that, however, you never have to adjust your rear bearings again.

Other people on the thread (Richard Woerz, I think; Grady maybe) have had their rear uprights apart and might know the bearing part numbers.

I'll try to find that thread....

 

[OliveR]

Thanks for the info about the modifications of the rear upright / spacer but it would be easier for me to replace the wheel bearings.

I would need to find a specialist her ein France to apply that modiciations and it won't be easy...

OliveR

 

[Pierre-Louis]

Olivier,

Maybe you should ask to the place in Too Loose where some fine 40' you know is serviced . The guy seems to know a lot...

 

[OliveR]

You're right Pilou, GT40P/1040 is 15 miles far away from my house.... I'll call the chief mechanic.

Thanks,

OliveR

 

[Seymour Snerd]

The thread I was thinking of is this one:

http://www.gt40s.com/forum/superformance-gt40s/30710-adjusting-spf-wheel-bearings.html

It spends a lot of time on discussing and indentifying and source of the seals on either side of the bearings. But along the way it does seem to identify the rear wheel bearings. I don't know about the front. I hope someone else does.

 

[OliveR]

Thank you very much Alan.. I have lots of reading with that interesting post...

OliveR

 

[Seymour Snerd]

Regarding the front bearing, you may have to resort to taking it apart to see what number is stamped on the bearing parts. I think that is at least a reasonable job to do.

In the case of the rear, that's not so easy since you need to press it apart.... but, we seem to know the part number at the rear so all is not lost....

I don't know if the press tool is still available. That would require a call to Olthoff to find out.

 

[OliveR]

Alan, that's not a problem for me to disassemble the front or the rear bearings... I have a big press tool and have done it already 3 times.

OliveR

 

[DaveM]

The front and rear wheel bearings are the same. As noted in the linked discussion the SKF bearing cone and race correspond to the Nilos #. The inner Nilos is 18690/18620AV so the bearing cone is 18690 and the race 18620. The outer Nilos is 18790/18720AV so the bearing cone is 18790 and the race 18720. As mentioned machining a spacer between the inner cones might help maintain load better especially if either bearing has too much clearance on the stub axle. I've found I had to green Loctite one rear outer cone to the axle because it was not a press fit.
On the Wilwood m/c Wilwood does not make rebuild kits for these. Guess they figure they're disposable. On disassembly they look suspiciously like Girling internals. I haven't miked up the seals, but do have a Girling rebuild kit for comparison. Changing fluid annually should be highly recommended, but even with that I've still had 2 clutch m/c fail in 5 years. The recommendation to change the fluid lines between the reservoirs and m/c to Teflon lined seems prudent.