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MG TD TF 1500 - Clutch Bite Point
|The clutch in the TF is less than a year old. The bite point is too high and causes difficulty with hill starts. At rest the arm from the bell housing in just slightly forward from the vertical (exactly as shown in the manual). However the relay arm at the sump is also vertical. The manual shows this pointing forward by about 30degs. The manual drawings are for a cable clutch and mine is a rod one. It is almost as though the connecting rod is too short. Has anyone got any ideas please. I will add that the gears engage quietly and I can stall the engine if I attempt a take off in first gear with the handbrake on.|
|Just searched the archives properly - was originally only looking at this years posts.Looks like I need to makeup and adjustable rod. Any up to date advice appreciated.|
|I fitted the Moss adjustable rod - it works. What you have to remember is which way to turn it to shorten or lengthen it (opposing threads on the ends. I have both pivot arms moving a similar angle each way. Gear change still stiff on this 5 speed box though.|
|Consider also the O'Connor modification (info in archives). A notable improvement for me.|
|Definitely worth doing as well.|
|You can also fit my rose jointed clutch kit and set it up exactly as you want to and no more bent clutch rods.|
|And add the needle bearing to the clutch lever.|
|Fancy Declan! I dig the engineering you set up in there.|
I made an adjustable rod dome years ago. I dont remember details but I did write up a "How-To" at the time.
Here is an excerpt.
Now the price of the adjustable link is not all that bad at $42 but I decided to roll my own. I needed to be careful or I could easily wind up having it cost me more.
I bought a 3' piece of 1/2" OD tubing at Sears, $9. I had a piece but it was a bit bent so I got a new piece. It was, as is to be expected, crap metal.
I had some 1/2 by 6 HRS flat stock, that Brian had bought 15 years ago when he was working on the Willies and I cut two 3" long pieces 3/4" wide and trimmed them down to 1/2 by 5/8 and turned a 3/8 round section on the end of each one.
Holding the pieces by the round end I milled a DEEP slot to form the clevis.
I adjusted the width of the slot to have only about 0.005" of clearance on the lever.
There are two of these; one will be RH 3/-24 thread the other LH 3/8-24 thread. Also the levers they go on to are different so the widths will vary.
I then cross drilled the clevis for the pins using my shop made cross drilling fixture. The tub was oversize and would not fit a 5C collet so I switched to ER-40
I did need to buy a 3/8-24 LH tap ( another $10 bringing my total to $19 almost half way to the cost of new), but I did not want to spring for a die. I chased both the LH and the RH threads.
With the clevises completed I made two custom small pattern nuts, one LH and one RH. I drilled out two 5/16 nuts and threaded them 3/8-24 L & R.
I cut a 9" piece of 1/2" tubing, cleaned the ID to 3/8 and drilled 25/64 by 0.100 deep. I put a strong 45 on the ends.
Using some 1/2 1144 rod I made some solid ends, about 3/8 long. These had a 0.100 step press fit on the 25/64 hole and a letter Q hole through. A strong 45 bevel was on the step. I pressed these into the rod and then Bridget TIG-ed them for me.
Back to the lathe, to machine the welds back and tap the plugs 3/8-24, right on one end and left on the other.
Now I could assemble the rod. Red is for the RHT and Blue is for the LHT I later stamped the parts with an L and a R just before I painted them.
And here is a close up.
I also made two custom clevis pins. I had to open the holes in the levers up to 21/64 to take care of the oval-ing. These pins fit the enlarged holes.
The front lever mounts on a pin bolted into the oil pan as I noted. It has an oilite bearing. It was quite worn. Abingdon wanted about $27 or a new lever and $20 for the bearing. Measuring it up it appeared to be metric, 16 mm OD and 12 mm ID. About 1” long. McMasters had some bearings but not 25 mm long. The longest was 16 mm. I got some of these and trimmed the length done to 12.5 mm
Using the ER-40 collet chuck solves the holding problem since these collets fit metric parts also.
They were about a 0.002” press fit and I may eventually need to do something with the ID. They fit fine before the press.
I now need to put the tranny back and see if things will work.
About 3 days work to save $20 (I hope).
I did check the picture links and they are still good.
|Thank you everyone for your comments. However I now think that (unfortunately) the problem lies within the bell housing. I don't see how tinkering with the rods and leavers would change the bite point. Surely this will be reflected in the position of the thrust bearing and consequently that of the leaver at the bell housing. As the friction plate wears the thrust will move away from the engine and the bite point will nearer the end of the travel of the pedal. New rods, leavers and bushing could give me a smoother pedal but will not affect the actual operation of the clutch. I would appreciate further advice before I remove the gearbox.|
|Jan I believe that is the purpose of the adjustable upper rod as supplied by Declan, Moss, AS and others. The upper adjustability allows one to compensate for wear. The advantage of Declan's setup is the Heim ends. It prevents the rods from being bent as it's design mounts it externally to the fulcrum points. I have the Moss setup of the adjustable rods top and bottom. My car had a cable originally. I'm happy with the new arrangement. |
|W A Chasser|
You can indeed adjust the bite point with the rods and the angle of the lever. My clutch rods incorporate the "O'Connor" mod-otherwise the rose joints will not fit and I find that the "O'Connor" mod is a vast improvement. My clutch is like a modern car with no nasty bite.
|Here is my recommendation on setting the clutch rods based on my kit but applies also to the original set-up.|
There is also a pedal stop in the pedal box on later cars.
|Looked up details of the O'Connor mods to the clutch. I had rebushed all the pivots last year so didn't need one of the kits. I spent a very enjoyable afternoon modifying my linkage. I cut the relay bar and found a M10 tap cut a perfect thread into the two ends. A piece of threaded bar and two nuts enabled me to set the relay arm at the correct 4.00 O'Clock position and drilling a new hole in the arm was easy. I have a 5speed box fitted with the engine move forwards and found the actuating rod from the pedal was a little short. A sleeve taped to 1/4BSF cured this. I don't know if it is the position of the relay arm or moving the pivot point or perhaps both but the clutch action is totally transformed. For anyone with reasonable engineering skills and basic tools this is a really enjoyable job and the results are outstanding.|
|I cheated: I fitted an MGA twin-bore master cylinder, which bolts on with the same bolts, and made up a hydraulic clutch. Another advantage is that the A cylinder bore is only 1", so you get a lighter brake pedal. You do have to keep the adjusters up, though. |
|D A Provan|
This thread was discussed between 01/06/2017 and 09/06/2017
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