How to: Triumph OIF to pre-OIF frame

[TanDawg100]

This subject has come up before and the answers are somewhat vague. Apparently Moore’s Cycle and SRM make kits for this- however being a machinist I always want to make my own stuff so I plunged into the nuances and befuddlements of this adaptation.

To be clear this is a '70 TR6 frame and a '71 or '72 front steering head. It has the big scoop drum brake. There may be slight differences with other years of both frames and front ends.
(I actually "dual pathed" this whole scenario- I first tried to use the original OIF steering stem bearings with my own sleeves to fit the '70 frame- I'll get into why this didn't work in a bit.)

Okay let's look at the steering stem- Triumph couldn't have created a more difficult situation in regards to the stem and the changes they made when they went from the earlier frames to the OIF:


On the left is the steering head stem and lower clamp that typically fits a pre-OIF frame. On the right is the OIF steering head stem and lower clamp.
On the pre-OIF the stem measures about .994" until you get to the step at the base of the stem where you see some braze- there it jumps to the larger diameter of 1.064". The I.D. of the bottom bearing in the Lowbrow Customs tapered bearing kit (For converting the unit frame to tapered roller bearings) is 1.0625" so it is about a .0015" press fit on this slightly larger diameter.
On the OIF stem the stem at the bearing locations measures exactly .750". The step at the base of the OIF stem measures 1.051"- roughly .013" smaller than the pre-OIF! So you cannot get a good register fit of the bearing I.D. on this OIF step because it is simply too small!
The bearing is around .575" in length, the step on the OIF is about .250" in length so you can make a spacer that is 1.0625" O.D., .750" I.D. and .325" long that when slipped into the bearing favoring the top half or the smaller end of the bearings taper- it will now allow it to fit flush with the base of the stem clamp and will register on the original bearing surface making it a good solid- registered fit.
(I happened to have some A-2 tool steel that was exactly 1.0625" OD- with a bit of polishing it slips into the bearing snuggly- I then drilled and bored it for the .750" I.D. so that it fits the stem nicely. You could use any steel- but A-2, O-1 and drill rod is available in the exact O.D. that you need and typically comes with an almost ground like surface on the O.D.)
I think the photos are self explanatory:


So now we have the lower bearing properly fit to the OIF steering stem.


Next is the top bearing situation.
The Lowbrow bearing kit's top bearing is identical to the bottom bearing dimensionally except it had a dust shield swedged into it but only part way:

In this photo I already have the spacer slipped into it up to where the dust shield extends into the bearing I.D. I made this spacer identical to the bottom one except I made it about .500" in length to be sure it would register on the OIF stems bearing surface.

The OIF stem nut slips nicely into the swedged dust shield and will come up against the spacer I have fitted to the I.D. of the bearing.

Okay to recap- we now have spacers that allow the Lowbrow bearings to properly register and fit on our OIF stem- the hard parts done! Once you install the races into the frame as per the usual methods as shown in English 101 and so forth you can simply grease your bearings, slip the lower one onto the stem, slide the stem up through the steering head and install the top bearing with the dust shield- then the top clamp then the steering stem nut and snug it all down and Bob's your uncle!
Except for one thing- the lower clamp on the OIF is a bit different in that the little lip that leads up to the machined lower bearing surface is "taller" and will interfere with the frames steering head and not allow the bearing to seat properly:

In this photo you can see a shiny spot and a burr where I milled some material away on the vertical lip coming from the bolt hole area of the forging/casting. I in fact need to do it a bit more. Study the two clamps in this area- I think you'll see the differences:

Once this is properly clearance everything should fit up sweetly! The original fork stops will work too.

The one thing I'm going to do is make an aluminum or possibly a steel tube to slip over the stem to be captured between the two spacers- why? To make sure that they don't slip out of the bearings to the middle of the stem. Now this get's a bit tricky because you can't measure exactly what the distance between the two is once it's installed. But you can install it all with out the tube spacer and measure how much your steering stem extends above the dust shield on the top. you have to hold it tightly in place and then measure- mine was roughly 5/16". Pull it out of the steering head, mock it up on the bench and measure between the two bearing spacers inside to inside on the stem- this will get you close- I'd make it a bit shy of this over all length- the main thing is that the spacers never slip down or up completely out of the bearings- this way you keep them in place- make sense? If not I can photo graph this as well. Just make sure everything tightens up properly and there is no vertical play in the steering head assembly once it is installed.

There you have it- or at least what I came up with!

Okay so now why can't we use the OIF's original .750" I.D. bearings?
I tried this first- got some new bearings and races. (Which in a standard size like that are really inexpensive I might add!) I then went to the work of actually making the sleeve to press onto the races that will allow it to fit the pre OIF frames steering head. But before I made the sleeve I took this much smaller race and held it in the area that it should seat on in the steering head- and as I feared it really didn't sit properly due to the radius on the outside bottom edge of the race and the flat in the steering head which was just narrow enough I was afraid the race could possibly pound into the portion of the steering head below the race flats. I hope this makes sense- I can do a drawing to clarify. I thought "no problem"- I'll just make a "cup" with a bottom that will allow it to seat properly in the steering heads race pocket. Here is what I came up with:


Sweet! So I installed these into the steering head and slipped the OIF stem and lower clamp in place and slapped the top clamp in place and... The stem just didn't come up far enough that I felt like I would get the stem nut adequately threaded on there.
If you look closely these smaller bearings are Taller. Plus the OIF bearing sits on top of the larger O.D. part at the base of the stem. That along with the fact that I had to make a pocket style sleeve (even though the bottom thin flange in my pockets is only about .040") the multiple stack ups was just too much and my stem came up short.
So in the end I went back to the early tapered roller bearing conversion kit and made the "internal" spacers- this gave me adequate stem extension out of the top to get the nut threaded on good. You might be able to find shorter .750" I.D. bearings... but they get expensive... so I went the other way and I believe it will work out much better.
I hope this helps others making this conversion in the future.

[Howitzer]

Good post. Thanks for the edification.

[KT]

GREAT POST! very indepth Nice work also....

[Howitzer]

Do you know if the Lowbrow Customs tapered bearing kit (For converting the unit frame to tapered roller bearings) will fit a set of pre-unit forks. They bottom tree looks like the one you have pictured on the left except my forks have these two "wings" on them. I wanted to order that set from lowbrow but I'm not sure if they will fit my forks. Any advice would be greatly appreciated.

[TanDawg100]

Do you know if the Lowbrow Customs tapered bearing kit (For converting the unit frame to tapered roller bearings) will fit a set of pre-unit forks. They bottom tree looks like the one you have pictured on the left except my forks have these two "wings" on them. I wanted to order that set from lowbrow but I'm not sure if they will fit my forks. Any advice would be greatly appreciated.

I haven't looked into that particular application- however if you hit Tyler or Kyle (or Wes or any number of these guys) they should be able to tell you. Triumph loved to make little changes on everything from year to year or model to model so be specific when you ask those guys. I'm fairly certain there will be a bearing kit available for your application.

[gravelveins]

now, if you could just do this for a 69 BSA neck...i would think you're totally killer.

i mean this is already an awesome thread with tons of valuable info...
but i don't really feel like paying over $100 to get some tapered roller bearings from somewhere in the UK.

[TanDawg100]

now, if you could just do this for a 69 BSA neck...i would think you're totally killer.

i mean this is already an awesome thread with tons of valuable info...
but i don't really feel like paying over $100 to get some tapered roller bearings from somewhere in the UK.

Sooo... I take it that the only tapered bearings available for your BSA are $100? Should be very similar to Triumph- if not the same I would think but I don't know for sure... anyone know the answer?

[Tyler]

Do you know if the Lowbrow Customs tapered bearing kit (For converting the unit frame to tapered roller bearings) will fit a set of pre-unit forks. They bottom tree looks like the one you have pictured on the left except my forks have these two "wings" on them. I wanted to order that set from lowbrow but I'm not sure if they will fit my forks. Any advice would be greatly appreciated.

Pre unit fork should have the same neck from '54 on up for sure. The lower tree you are describing, if it has 'wings' that stick pretty far out sounds like the mid to late 50s front ends, those wings are the fork stops. The top of the stem should be 1" OD and the bottom of the stem where it steps out a bit where the bearing sits should be about 1.0625" or so. If you have a digital caliper measure it to be sure, but it sounds right. Do you have any idea what year the front end is?

Tyler

[gravelveins]

tri and bsa front ends look almost identical except for the stem size..i think BSA stems are larger(?)
i've sourced tapered bearings from some stores overseas...
and it's like $90 for the bearings itself...but then they bite you in the but with the shipping.

oh well...gotta do what you really gotta do sometimes i guess.
just want to make my bike right and good.

[TanDawg100]

tri and bsa front ends look almost identical except for the stem size..i think BSA stems are larger(?)
i've sourced tapered bearings from some stores overseas...
and it's like $90 for the bearings itself...but then they bite you in the but with the shipping.

oh well...gotta do what you really gotta do sometimes i guess.
just want to make my bike right and good.

Don't be so quick to give up- do as Tyler suggested and get some calipers or a 1"-2" micrometer and measure where the bottom bearing slips onto the stem. Odd's are he can fix you up with what you need. 50 bucks beats the hell outta 100 bucks...

[Howitzer]

Pre unit fork should have the same neck from '54 on up for sure. The lower tree you are describing, if it has 'wings' that stick pretty far out sounds like the mid to late 50s front ends, those wings are the fork stops. The top of the stem should be 1" OD and the bottom of the stem where it steps out a bit where the bearing sits should be about 1.0625" or so. If you have a digital caliper measure it to be sure, but it sounds right. Do you have any idea what year the front end is?

Tyler

Thanks for the advice Tyler. I don't know the exact year they are from. I got them from lurkingclass and, if i remember correctly, he said they were early 1950's. I forgot to ask for a specific year. I did find out that those bearing would fit my forks though. The bearings are currently en route, so I can let you guys know how they fit once I get them.

[buzzkilr]

I know this post is way old but if anyone is out there from the original thread and can answer my questions I would appreciate it! I'm about to do this same maneuver. 71 OIF forks on a 70 T120r frame. Could I make the shown spacers a little tight for the bearing ID so they are less likely to move up or fall down? Maybe use some bushing Loctite to secure them further? Orrr maybe a piece of PVC tube that isn't too tight lengthwise could be placed in the center?

[TriNortchopz]

the same how-to is posted on JJ by TanDawg, with a few different replies which may be of interest:

https://www.jockeyjournal.com/thread...y-frame.66344/


more here:

Triumph T140 forks to pre OIF 650 frame
"A bottom yoke and stem top nut from a disc brake Trident would be a better option."
https://www.accessnorton.com/NortonC...0-frame.26501/

Front end options pre unit
https://www.triumphrat.net/threads/f...e-unit.901329/

this may be of interest:

FRONT ENDS AND FORK TUBES
"The following pictures should help you determine if the front end of your bike is the right type for the year of the bike..."
http://raskcycle.com/techtip/webdoc18.html

TAPERED ROLLER BEARING SET, FOR 1" STEERING STEM TO TRIUMPH PRE-OIF
"This bearing set will allow you to fit a variety of 1" springer and other 1" stem front ends;

Triumph 650 twin cylinder 1963-1970 Triumph 350, 500 twin cylinder 1967-74 Triumph 500, 650 pre unit twin cylinder 1954-1962 swing arm frame (please note will not suit early 1954 frames) Triumph triple cylinder 1968-1974 BSA triple cylinder 1969-1971"
https://www.trojanclassics.com/taper...eering-stem-to

Front And Rear Suspension
https://oldscoolchoppers.com/collect...orks-and-parts

[buzzkilr]

the same how-to is posted on JJ by TanDawg, with a few different replies which may be of interest:

https://www.jockeyjournal.com/thread...y-frame.66344/


more here:

Triumph T140 forks to pre OIF 650 frame
"A bottom yoke and stem top nut from a disc brake Trident would be a better option."
https://www.accessnorton.com/NortonC...0-frame.26501/

Front end options pre unit
https://www.triumphrat.net/threads/f...e-unit.901329/

this may be of interest:

FRONT ENDS AND FORK TUBES
"The following pictures should help you determine if the front end of your bike is the right type for the year of the bike..."
http://raskcycle.com/techtip/webdoc18.html

TAPERED ROLLER BEARING SET, FOR 1" STEERING STEM TO TRIUMPH PRE-OIF
"This bearing set will allow you to fit a variety of 1" springer and other 1" stem front ends;

Triumph 650 twin cylinder 1963-1970 Triumph 350, 500 twin cylinder 1967-74 Triumph 500, 650 pre unit twin cylinder 1954-1962 swing arm frame (please note will not suit early 1954 frames) Triumph triple cylinder 1968-1974 BSA triple cylinder 1969-1971"
https://www.trojanclassics.com/taper...eering-stem-to

Front And Rear Suspension
https://oldscoolchoppers.com/collect...orks-and-parts

Hey thanks! Again! Just saw your reply today. Seems super do able!

[buzzkilr]

Ok so I made the spacers as described above. But now I'm a bit confused. Won't the stem nut just drive my top .500 spacer right out of the bearing when I tighten it up?

[TriNortchopz]

...Won't the stem nut just drive my top .500 spacer right out of the bearing when I tighten it up?

Were you able to do the pre-assembly as noted above to check the amount the top of the steering stem is sticking out above the top dust shield, to be able to determine the length of the steel spacer sleeve;

"...I'm going to do is make an aluminum or possibly a steel tube to slip over the stem to be captured between the two spacers- why? To make sure that they don't slip out of the bearings to the middle of the stem. Now this get's a bit tricky because you can't measure exactly what the distance between the two is once it's installed. But you can install it all with out the tube spacer and measure how much your steering stem extends above the dust shield on the top. you have to hold it tightly in place and then measure- mine was roughly 5/16". Pull it out of the steering head, mock it up on the bench and measure between the two bearing spacers inside to inside on the stem- this will get you close- I'd make it a bit shy of this over all length- the main thing is that the spacers never slip down or up completely out of the bearings- this way you keep them in place- make sense?"


Do you also have the two steering head bearing abutment rings as part of your '71 assembly?

#83-2007; Abutment ring, steering head bearing, Triumph TR6, TR7, T120, T140 TSS, TSX

OD: 1+25/32" (45.1mm)
ID: 1+7/16" (36.5mm)
*NOTE:
NOTE this item appears incorrectly in some Triumph parts books as dust cover.

Located above the lower head bearing and below the upper bearing.

https://www.classic-bike-shop.com/83...tsx-2958-p.asp

Parts assembly, forks, 1971/1972:


As noted above, the numbers are mixed up for the bearing rings and the dust cover in this parts assembly image;
#13 and #15; the 2 bearing rings (#15) are listed as the dust cover (#13) in the description notes below the image - see here:
https://draganfly.co.uk/product-cate...1971-72-forks/

[buzzkilr]

Thanks sir! I was under the impression the spacer sleeve was optional I'm thinking now it's not! That drawing had confused me in the Glenn's book I think its shown the same. Well I'll keep at it then!

PS If I use a T150 lower tree and the top hat along with the Lowbrow tapered bearing kit would that dispense with all the spacers desribed by the original poster?

[TriNortchopz]

...If I use a T150 lower tree and the top hat along with the Lowbrow tapered bearing kit would that dispense with all the spacers desribed by the original poster?

found this:

"The situation with using T-140 fronts on older frames pertaining to the T-150 steering stem is this: Can you just bolt on the T140 parts?
Yes you can, BUT you have about HALF of the thread engagement on the top nut!
I put a T140 front on my A75 and wasn't about to use the standard stem after seeing this.
I used a late T150 lower with the correct length stem, Not worth the risk imo to save a few bucks and possibly have the threads strip and your front end go loose!"
and
"I just mocked up OIF drum brake yokes on a 1964 frame. The nut is screwed on about two turns..."

"...'68 frame and T140 forks - wont fit..." "It will fit, just the stem top nut only has a few threads to grab;
a T150 yoke is just easier with a 'dry' frame, because the stem is the same length as the 'dry' frame's original stem and the bearings match."

"T140 stem is shorter. A change that came about with the the oil bearing frame and tapered bearings? The T150 didn't change from the early bearings/neck specifications so the late T150 disc brake stem is longer to fit the early bearing/neck arrangement."

https://www.britbike.com/forums/ubbt...&Number=522658


For reference:

Front forks spares & parts for Triumph 1968-75 – T150/T160
Part Number & Description
https://draganfly.co.uk/product-cate...nt-forks-t150/


Yokes, Bearings and Conversions

Recently I have had a number of enquiries regarding the correct arrangement of parts in the steering head area of various Trident and Rocket 3 models, and the correct way of converting earlier drum brake models, of both variants, to Disc brake.

In 1969/70 models, the arrangement of the steering head races is fairly obvious, however the problems start occurring with the introduction of the forks used with the conical hub brake in 1971. Although the yokes used in these forks are similar to the Triumph/BSA Twin models that used them, there are important differences with regard to the location of the steering races, and the length of the steering stem.
The bottom yoke is the only one affected, and it is very dangerous to try to use a twin yoke on a triple.

The frame headstock lug used in all T150 Trident models was the same general forging as that used in the 1963-1970 6T/TR6/T120 Triumph twin models, the later Daytona models, and generally dimensionally the same as BSA Rocket 3, and therefore the headrace cups and cones were also (nearly) identical.
However, the fork yokes used for the 1971/72 Triple drum brake and 1973/75 Triple disc brake models used a smaller diameter stem than the 1969/70 Triple models, or the other earlier twins
and another piece, part number 97-4145 was fitted into the arrangement to adapt the smaller stem to the existing top cone.
The dust shield fitted in the top cone remained unchanged.
As this adaptor (#97-4145) is a separate piece it is not supplied in headrace "sets" and has to be moved from the existing top cone to the replacement.
The bottom cup and cone remained unchanged, with in Triple yokes, the smaller diameter stem having a thickened lower register to locate the lower cone by its inside diameter.
The small stem design, when used in the "oil-in-frame" twin was engineered to allow the use of two taper roller headraces in a smaller headstock. In this version of the arrangement the taper roller sat on the thickened lower area, around a ground raised area of stem. The Trident did not receive this modification until the T160 model of 1975, which also had a longer stem too, so the bottom yoke is specific to that model.
The very few disc braked Daytona models produced used the old headstock arrangements, and therefore the fork yokes from the T150, and the adaptor.

This knowledge usefully leads to the choice of the correct method of fitting a set of T120 or T140 disc brake forks and wheel to an earlier T100/T120 Twin or T150/A75 Triple.

The "oil in frame" twin that carried the disc brake fork used the small diameter steering stem and taper roller headraces. The bottom yoke is not suitable for fitting these forks into an earlier twin or triple because the location arrangements for the cup and cone headraces are incorrectly sized or positioned.

The correct bottom yoke to use for this modification is the one from a 1973/75 T150 Trident. Either style of disc fork top yoke, with the instruments mounted under the dummy fork top-nuts, or in the T160 style pods, may be used when doing this conversion.
The 97-4145 adaptor must, of course, be fitted. There are also damping and springing specification changes between twin and triple, but these internals are interchangeable.

The overall length of the steering stem was also different between the variations in yokes, and only the T150 disc type yoke has the correct length for this "Retro-fitting"..."

http://www.triples.co.uk/articles/articles/yokes.htm


Top Spacer for Triumph Triples Fork Bearings
Part Number 97-4145



Original equipment on Triumph triples with disc brake front ends.

To allow forks with ¾” stem, conical and disc brake, 1971 on style, to be used on pre-oil-in-frame necks.
Used with 99-3733/A Taper Bearing Kit.
As fitted to top bearing cone on 1971 on T150 and A75 models, and the Triumph Hurricane X75.

http://www.britcycle.com/Products/97/97_4145.htm

Taper Bearing Set For Triumph Steering Heads
Part Number 99-3733/A

Includes top dustcover. Taper bearing set for Triumph steering heads on the following models: 1956 onward Triumph preunit 500, all 1956 through 1970 Triumph 650, 1967 onwards Triumph 500 twins except TR5T.

Replaces cups, cones and loose balls, providing easier installation, less frequent adjustments, longer life, and better handling. We also stock taper bearing conversion kits for many other models of Triumph, BSA, and Norton..."
http://www.britcycle.com/Products/99/99_3733a.htm

Heavy Duty Taper Bearing Set For Triumph Steering Heads
Part Number 99-3733/B

Replaces cups, cone and balls for many models.
See also 99-3733/A, our non-heavy duty set.
How to; Installation Instructions
http://www.britcycle.com/Products/99/99_3733b.htm

[buzzkilr]

Thank you ....again! I'd rather get a drum T150 lower tree I assume it also has the longer stem?

[TriNortchopz]

...I'd rather get a drum T150 lower tree I assume it also has the longer stem?

from what I read above,

"I used a late T150 lower with the correct length stem..."

"a T150 yoke is just easier with a 'dry' frame, because the stem is the same length as the 'dry' frame's original stem and the bearings match."

"...The T150 didn't change from the early bearings/neck specifications so the late T150 disc brake stem is longer to fit the early bearing/neck arrangement."

"The frame headstock lug used in all T150 Trident models was the same general forging as that used in the 1963-1970 6T/TR6/T120 Triumph twin models...
the fork yokes used for the 1971/72 Triple drum brake and 1973/75 Triple disc brake models used a smaller diameter stem than the 1969/70 Triple models, or the other earlier twins
and another piece, part number 97-4145 was fitted into the arrangement to adapt the smaller stem to the existing top cone...The small stem design, when used in the "oil-in-frame" twin was engineered to allow the use of two taper roller headraces in a smaller headstock. In this version of the arrangement the taper roller sat on the thickened lower area, around a ground raised area of stem. The Trident did not receive this modification until the T160 model of 1975, which also had a longer stem too, so the bottom yoke is specific to that model...The overall length of the steering stem was also different between the variations in yokes, and only the T150 disc type yoke has the correct length for this "Retro-fitting".

Top Spacer for Triumph Triples Fork Bearings
Part Number 97-4145
Original equipment on Triumph triples with disc brake front ends.
To allow forks with ¾” stem, conical and disc brake, 1971 on style, to be used on pre-oil-in-frame necks.
Used with 99-3733/A Taper Bearing Kit.
As fitted to top bearing cone on 1971 on T150 and A75 models.

found this:

Installing OIF forks on 63-70 Models

"...Your top bearing cone will fit the OIF stem,if you get the collar from a '71-'74 T150.It's a top-hat shape and it fits neatly between the bearing and stem.P/N 97-4145.
The '71-'72 T150 lower yoke is right if you have the drum brake.Your lower bearing cone will fit that yoke."

"I am purchasing a kit from SRM Engineering that should allow me to put a 1972 front end on a 1967 frame

Code SRMTR8 - Taper rollers with specially made outers.
£48.68"

"I converted a 71 T150 front end from conical to disc from a T140. I used a later T150 bottom triple clamp and a roller bearing conversion from The Bonneville Shop that pressed right in..."

"...TR6 has dry-frame steering head with cup-'n'-cone steering bearings, T150 has dry-frame steering head with cup-'n'-cone steering bearings, oif steering head is both slightly shorter and has taper-roller bearings... t is possible to use the oif bottom yoke and steering stem, but the top nut doesn't pick up many threads on the stem; also you need taper-roller steering bearings that'll fit the dry-frame steering head, which can make it even more difficult to attach the nut to the stem?"

"...almost nothing is interchangeable between disc and comical forks. Disc yokes hold the legs almost an inch further apart - 7-5/8" centres vs. 6-3/4" centres. Even comical and disc axle clamps aren't interchangeable."

"...What you need to look at is a 73(2nd series)or 74 T150 parts book. I would not use the T160 book as it uses OIF T120/T140 steering head bearings. You can see these books at www.bigdcycle.com or www.classicbike.biz . The frame bearings (97-0111) and the lower tree bearing (97-0431) are the same on the T150 and your bike. The race bearings are also the same size. The difference is your have free balls (forgive me) and the T150 were in a cage. I would use the T150 top bearing so all parts match. The steering head area on the T120/T150, distance wise, from bearing to bearing is the same..."

https://www.triumphrat.net/threads/i...models.194400/


TRIDENT EVOLUTION
T150 Trident genealogy can be broken down into 2-year chunks, with significant changes made with each, followed by the ’75 T160 Trident and then…oblivion.

The 1969 and 1970 T150 Trident were essentially the same bike other than the clunky bodywork that came on the early ’69s. They were based upon the prevalent Triumph hardware of the time, ie: 8-inch TLS front brake,...

The 1971 and 1972 T150 adopted the more modern-looking bodywork and cycle gear from the new Oil-in-Frame Bonneville and TR6 lines launched in 1971. These included those gorgeous new conical hubs front and rear...

The next major change came with the 1973 and 1974 T150V, with addition of a much-needed hydraulic front disk brake...

https://www.webbikeworld.com/triumph-trident/