Greeves Leading Link Fork Geometry

[oldslowcoach]

Hi
Are there any obvious geometry differences between Scottish, Hawkstone, and road forks? I have a pair off a 62 TE with flush competition number plate tabs, beefier loop around the tyre and extra strengthening brackets around rubber bushes. The other pair has a flimsier loop, no strengthening brackets at rubber bush and protruding competition number plate tabs. Both pairs have steering head bearings that steepen the angle of the fork tubes. With regard to the head bearings steepening the angle of the fork tubes, was this the same for all models? I am trying to identify a likely model the flimsy loop pair came off. I do have photographs but I am unable to attach them, more than happy to email to anyone

Regards
Peter

[Brian Thompson]

Steering head angles (trials machines.)

The only info I can offer on this relates to the differences between TA and TC models. Not only was the head angle steepened (by 2%) on the TC, also the fork crown plates were changed which gave 20% more steering lock. This resulted in the wheelbase being shortened, from 52" (TA) to 51 3/4" (TC.) Details on all these changes and more can be found in 'LL'#43 in Andrew kings excellent article on the development and differences between the various 'Scottish' trials models.

Finally, I've attached a pic I took of page 12 in 'LL'#47. This clearly shows the different steering head angles between the TA and TC.

Can anyone else help out with this query please, or add any further info?

Brian.

[Peter Rotherham]

Leading Link Forks.

Hi, this will be an overview I'm afraid, but the exact details of Fork angles/bearing types, lengths, etc,. would probably take me all night to type in with one finger! (I'm not too good at Computers). So here goes....

You say you have two pairs. You identify them easily enough by their construction. What you haven't said is what 'bike you want them for.

Essentially, Greeves started experimenting with 'Trailing' link forks, (Like Lambrettas), but went to 'leading' link types, initially damped with a rubber in torsion 'cone' on the early (1953 - 57) bikes. There was a brief period of part Girling Units/rubber forks, then came the first sort of leading link units, seen in about late 57/early 58. The TA series had cup & cone head bearings. The top yoke, a simple steel pressing was straight = Road bikes, 'v' shaped backwards = Scrambles, 'v' shaped forwards = Trials. Soon adopted onto redesigned road bikes, the forks gained lugs for mudguards and no plates. by 1961/2 a heavier type of this fork was seen, coming in on the 'E' range of Trials bikes. A change to taper roller head bearings also followed with a slightly beefed up alloy beam and a longer frame spine which now went around and behind the gearbox. This was later altered to reduce the overall length of the cradle to allow repositioning of the engine, (technical stuff, beyond me!). The Forks had reinforced loop plates and a shallower angle loop, which had different fixings for the Rubber Bushes. After these came the 'banana' forks, but even they had variants......

Forks were basically cut & shut to order, for silverstones and off road bikes, and/or road bikes. There are post 63 bikes out there with the earlier forks on. Ex-Factory Staff may know if this was a 'use up the parts' process, or maybe intended. However, for us, the owner faced with needing a set of Greeves forks, the first question is.....What model have I got? What do I intend to use it for? How do I want it to be when finished, concours or usable? After that, there are only 5 main points.Did/does your bike have the early or later type of LL forks?Does the frame have Taper roller or ball bearing head races.If its a road bike, does it have the smaller, angular loop on the swinging arm and the added mudguard loop?Are the forks short or have welded on handlebars?Are there extra bits on that may be ISDT fittings or for different brake anchors?What types of wheel do you wish to fit?

The best way to identify your 'bike is from the GREEVES book, or from the Villiers engined bikes series, most of which are still on sale at Autojumbles & shows. Invaluable to any owner as they have good photos and give basic info. More detailed stuff does reside with the GRA, but is open to members only I'm afraid.

Does that help? If you wish to know EXACTLY what type of forks you should use, it will be neccesary to know which model of Greeves you have..........

[oldslowcoach]

Fork puzzle solved

Thank you Brian and Peter

straight = Road bikes, 'v' shaped backwards = Scrambles, 'v' shaped forwards = Trials

- is the answer. The flimsy pair I was trying to identify never seemed right around the yokes. Turn the top yoke to 'v' shaped backwards and now it all fits perfectly. Scrambler forks. This is all jolly handy as I want them for a 5TA engined 59 Hawkstone. The bike has had an interesting sort of non history as follows -

Built around 1963 with 59 chassis and 59 Triumph engine
Purchased by my father in 1965 as he liked the one in "Built for speed" and taken to Germany to set standard times for Army motorcycle events. Parked up in uk from 67 to 70 while we were in Malaya. 1971, forks swapped for AMC Teledraulics but mercifully front paddle hub wheel retained. Teledraulics never fitted and bike parked up. 1978 my brother and I fit incompatible Greeves forks and ride around garden and adjacent field. After a few rides over six months the ignition fails. Parked up ever since ( over 30 years ) and now owned by myself.

I took a punt on these cheap forks on US ebay reasoning that it was mainly scramblers that went to the US. Now I can get it going. Only problem is that myself and the forks are in Brisbane Australia and the bike is in Wiltshire UK. Unfortunately I do not have any photographs of the bike but it is like the one in Built for speed but it has the original 63 build Butler glass fibre boat tail saddle / mudguard and matching front mudguard, also kept. Just in case you think we were crazy not fixing it earlier we did have other off road Triumphs to ride. Recently I have bought a 3TA engined Scottish and have a couple of other Scottish chassis likely to receive Triumph motive power, so I could certainly keep a dedicated Greeves Triumph forum ticking over

Regards
Peter

[Geoffrey Medd]

I am wondering how to determine if my metalastic front fork bushes are shot, the bike is a 1960 TCS. I assume that the indicator is the centre to centre dimension of the damper holes? Could anyone please provide me with a dimension ? I assume it is also needed when the holes are drilled for the shear pins, thats assuming I can locate new bushes!! Thanks.

[John Wakefield]

This is the drawing you need and it gives the measurement. A word of warning before you go dismantling your forks, no new bushes are current available. The last ones were sold by Villiers Services some months ago and they are not planning to get a new batch made.

[Geoffrey Medd]

Thanks very much John, a big help. On the subject of the front Metalastic type bushes. I did a bit of research myself and approached a firm called AV Industrial Products (Engineering) of Leicester who provided a what I thought was a fairly reasonable quote for manufacturing the bushes. However the quote was only based on physical dimensions of the bushes and the Shore hardness. What is missing is the specification provided by Greeves to Metalastic for the original manufacture, either written or a performance spec, upon which the bushes could be validated. Without that any ordering would be risky, especially as a minimum order of 50 is required!! I f we did have a spec then possibly a crowd funding effort by members could be arranged and the bushes distributed by Villiers or Greeves? Regards

[John Wakefield]

Geoff as you dont say what the quote was from AV Industrial we dont know if it is a reasonable price compared with that of Robush the agents for the successor to Metalastic (Trelleborg) who have recently quoted 57 GB pounds per bush plus VAT (68.50) which would be 137 per pair again with min batch 50. Of course the final price due to shipping costs, and dealer mark up would make them nearer 150 per pair. A better way round the problem would be for the GRA to place the order (they have a large bank balance according to last balance sheet) The bushes could then be sold on with a small mark up by the club.

[whitehillbillies]

I have seen on other forum sites where Members band together and do a Group Buy, for a Product.

whitehillbilly

[Geoffrey Medd]

Hello John,
The quote I received was for ?42.25 per bush plus VAT for 45 Shore bushes. Min order quantity of 50 and a 14/16 week delivery. I went back to them yesterday on the specification side and they said "For IOS Bushes we perform tests to find radial and axial stiffness". But as I said earlier this doesn't mean anything (to me) unless we have comparable values for bushes we know work. I suppose one way would be to subject a Metalastic bush to the same test? If anyone has a spare bush (!) I would be willing to do the necessary liaison with AV to carry out any investigative work, I'm assuming that there may be a charge for this. Regards

[John Wakefield]

Bit of a dilemma Geoff. the bushes may be some 15 GBP plus VAT cheaper but if they dont work out to have the correct axial stiffness its a gamble, you could end up with 2.5k of scrap and a lot of irate buyers. I understand that someone some years ago had a batch made by another supplier and the failure rate was extremely high on scramble bikes, some lasting only one meeting. So maybe best to pay the extra and get the original spec bushes which have been proven quality. Incidentally I understand that the lead time from Robush was around 7 weeks. There is still the issue of the 50 shore for road and racing bikes.

[whitehillbillies]

Trailing arm Bushes for Vehicles come in many different sizes.
I wonder if one could be found to suit.
Find Vehicle Bush Size - SuperPro

whitehillbilly

[John Wakefield]

Trailing arm Bushes for Vehicles come in many different sizes.
I wonder if one could be found to suit.
Find Vehicle Bush Size - SuperPro

whitehillbilly

I think that avenue has been been down 'Whitehillbilly' it would appear that the size chosen by Greeves was in the 1950's a popular vehicle suspension bush, it has long been obsolete and taken out of manufacturers catalogues. The issue is not finding a supplier, (there is one Robush), the issue is the high outlay for a minimum order of a component that may well sit on the shelf for a number of years. Despite many of these bushes now being over 60 years old, the failure rate is very small. And with many bikes now only used for showing the demand may well remain low. I still feel that the solution may well be for the club (GRA) to make the purchase and then sell them through the current regalia sales.