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Fork Tube Size

16K views 26 replies 9 participants last post by  o1marc 
#1 ·
I can find every bike under the sun fork diameters in mm, but absolutely nothing for Triumph. What size in mm are my 70 Tiger forks?
 
#4 · (Edited)
34mm works out to 1.338, so larger than the 1.303. I've found on other search that said they were 1.625 (1-5/8"), but that works out to 41.275 and I don't think they are that large.I'm trying to fit dual disc fork legs in my Tiger trees so I don't have to replace all the headlight and gauge package also, or do extensive modifications to make that all work. I wonder if there is enough meat in the stock trees to bore them out 1mm to accept a set of 35mm and not break when tightening them down. The only way I will do all the headlight mounting mods is if I can find a reasonably priced set of Ceriani's.
 
#7 · (Edited)
Guys, come on. I'm doing research right now so I have my ducks in a row when I get the bike in my possession after the first of the year. I wouldn't ask you questions I could answer myself if I could.
The responses are starting to go left field, so let me clear up what I am doing again. I have a 70 Tiger. I want to adapt a set of Kimtab mag wheels with dual discs on it. I don't think Triumph has a solution to my issue so Triumph parts are out and I'm looking to adapt a pair of modern forklegs with dual calipers. I was under the assumption the Triumph had 35mm forks, instead of the spindly 33mm they seem to actually be. I need to fab bearing/rotor carriers for the Kimtabs anyways so I can deal with rotor offset to accommodate caliper spacing at that time. This way all I need to mod I believe will be wheel spacers to fit the forks I chose. If I use a stock 33mm tree and take out 1mm they become 35mm. Now forks fits in my trees with no mods to lights and gauges. After some research I wouldn't mind using Triumph calipers. The glitch now is knowing the fork width spacing on the Triumph and the fork donor bike to see how much mods will be needed at the lower forks for spacers.
 
#6 ·
Hi Marc, The idea you have is good, but using later Triumph forks & sliders w/disc mounting won't really work in your trees. The top of the station tubes is different, being straight on the disc legs (not tapered) & therefore needing an upper pinch bolt as the later tree uses. The other consideration is the front hub. The disc hub unit is wider so needs the later trees to match. Yes, if you go with later trees then you'll need to make a new mounting for the gauges. On the late bikes the top fork leg bolt, meaning the one that holds the late gauge bracket is just that a gauge bracket retainer. It retains the gauge mount only. Doesn't do anything with the spring as there is a lower plug looking bolt that retains the spring, it doesn't hold the leg on either. Again the top of the leg is simply "pinched" by the top tree clamp. Your top bolt actually pulls the leg up into the top tree taper, so the later forks are a complete redesign.

The thing about your forks is the slim narrow look is so desirable. Plus the chrome trim & shape of the legs. I've no idea what's available, but would it be practical to get a spool front hub & fit discs to it, then weld caliper brackets on your sliders?

To me doesn't look like there is enough material to taper the top of later tube to make a taper to fit either a stock top tree.

Looking at top tree, I personally would feel comfortable boring out only 1mm. I'm no engineer so take my opinion for what it's worth.

Comparing the inside of the early & late top tree the later tree has a boss cast inside for the pinch bolt & threads. The early tree is rather hollow there so I don't feel is practical to bore one straight & add a pinch bolt.

Good luck on your project. Let us know how it turns out.
Don
 
#8 ·
Does Triumph make Left and Right calipers ? Since you're not committed to using only Triumph parts, maybe consider using a beefier triple and grafting correct stem and bearing cups ? Those old triples are not really that strong to begin with. For a performance front end I wouldn't want weakened components. This why people without the fab and engineering skills required usually swap the whole front end out, wheel, forks,triples, calipers and all. My boss used to have a plaque on the wall: " When you're up to your ass in alligators, it's difficult to remember that your original objective was to drain the swamp."
 
#9 · (Edited)
Daytona 675 is dual disc front end, so yes, left and right calipers. I'm trying not to change the silhouette of the bike. If I go with swapping trees then it means changing gauges, headlight, etc. that I am trying to avoid. I just need from the forks down to be able to have dual discs. So ultimately the only difference is the wheels and brakes with minor differences in the lower legs. The only way I will go with different trees is if they are Ceriani GP forks. If I bore the trees I would only need to take out 1mm out of the lower tree to accept 35mm forks and I would machine the taper on the fork to match the top tree.

Actually the Daytona used Brembo and Nissan calipers, but the 1200 Trophy uses a Triumph caliper in pairs.

 
#10 ·
I still can't quite figure what you are doing/asking.

the initial request seemed to be about a 1970 Meriden Triumph.
You asked questions about the stanchions, and got an answer.

Then you revealed that you wanted to add dual disc legs, which one would generally read to mean that you plan to add Meriden Triumph ones?

Then you show a picture of Hinkley Triumph Brake callipers.
Hinkley triumphs have nothing whatsoever in common with the Meriden plant. ( other than the ownership of a name. Like modern Indians are nothing to do with 40's bikes.)

what exactly are you planning?
 
#12 ·
I understood the plan as adoption of more current front legs + Hinckley Triumph calipers + Kitman allu wheels to original 70 Triumph triple tree to keep original lamp, instruments and bracket intact.
Only one problem I see here is to find out if a width of the front Kitman wheel with discs is not bigger then original triple tree width.

My question is why would you do it, for better braking or you just prefer a look of Kitmann wheels ?
I wasn't thrilled with a performance of the front Triumph drum until last year, when finally I found a local shop able to change my shoes lining for a proper one and arc them properly too ( $40.- ).
After this i build my peg on the front slider to make it longer and without any clearance in the front brake plate.
Now I enjoy 2 finger front brake as effective as old Honda CB750 disc.
 
#13 · (Edited)
I thought I explained it in post #7. I have set of Kimtab snowflake wheels like on my XR1327 and the Kawaton. I think they would look period correct on the 70 Tiger. They are dual disc, so I need a lower fork leg that will accept a caliper on each side. I understand that the fork width spacing is different from bike to bike, so I need only for the forks to mount into the Triumph trees. The Kimtabs I have came bare, so custom bearing/rotor carriers need to be machined and can accommodate spacing to match the caliper placement, and then spacers for the wheels to finish it all off.
Just want something like this without the expense of the Ceriani's.



The Triumph calipers with the name would just be an added touch, doesn't matter what factory the bike or brakes came from, everything can be fabbed to make it work.
 
#14 ·
The two solutions that I can think off are.

Find a twin disc bike ( probably from the same era) possibly Japanese .
See if you can fit the stanchions into the original triumph yokes.
Then modify the new spindle/axle to fit the cast wheels.

A lot of Japanese wheels (I think) came with a removable spindle rather than fixed.

What a lot of people do to 60's triumphs is to take a 70's trident complete disc front end and use the yokes on the 60's frame.
A 71 on twin frame was different so the yokes don't fit. They can be made to fit, but the spindle is too short for safety

When the racers started adding a second disc, they simply added a left carrier backwards on the right.
It looked horrible but who cared?

Then people started making right handed legs, but the Lockheed caliper had to be mounted upside down

Later bikes used brembo and they can be configured either way. Afaik the brembo fits as a direct swap but the fittings are metric
 
#15 ·
I got one of my new Kimtabs delivered today that I bought on eBay. The seller pulled a bait and switch on me.
I bought this:

Kimtab rim snowflake design very rare twin disc 19"


I asked him to remove the tire as it has no value to me and I didn't want to pay the shipping on the added weight. "So he did me a favor" and saved me more weight by removing the unobtainium Kimtab rotors.
Now I have to pay probably 3x's what it would have in shipping if they were still on the wheel.

I received this:
 
#16 · (Edited)
Has anyone ever welded tabs on a stock front leg. In my mind I don't see an issue. I do remember a conversation with Steve Storz when I wanted to weld caliper mount tabs on my vintage Ceriani's before I realized how valuable they were. He said I would distort the tube and they'd never work right again. Looking at these stock legs I don't see an issue as there are factory lugs welded on. If I can weld a couple of tabs to mount calipers all my issues are gone.
 
#17 ·
I am a bit confused too -- however one part i think i am clear on is that you want to stay with your 1970 "triple trees" and modify them(if possible) to fit a twin disc brake set up - regardless of the diameter of the fork tubes and how much you can bore the trees out - i think your biggest hurdle is that the width of your 1970 trees is too narrow to take any kind of twin brake set up ( i may be wrong but i think the width of the "Dry frame" forks is less than the OIF models )
 
#18 · (Edited)
I don't believe the Triumph is any narrower than my Ceriani forks that I have dual discs on. Anyway, all the potential issues I have come up with have made me come to the conclusion that my easiest out is to just weld on 4 tabs (2 per leg) to the lower legs to mount calipers and be done. No more issue with gauges, triple tree tapers, fender mounting, etc.
I'll weld on tabs to mount these Triumph calipers making it look more "factory original"


I've asked but haven't gotten an answer yet from anyone who has access to a set of forks to measure the distance between the fork tubes.

Fork spacing on the Ceriani's is only 5.25", Surely the Triumph is wider? On My Ceriani's I don't think I could have accomplished it with anything other than the 1/8" thick Kimtab rotor as it sits about 1/16" from the fork tube when mounted up. A Honda CB 750 rotor would not fit this application.
 
#19 ·
I have read in the past that caliper mounts have been welded both to Triumph ali fork bottoms ( before RH disc slider was available) and the the steel earlier T120 type - by Meriden - so its possible but how you do it without distortion I have no idea --- looking forward to see a pic of the completed front end with those calipers
 
#20 · (Edited)
Because I don't have them in hand don't know, are my 70 sliders aluminum or steel. Either way competent alloy welder will know how to weld them without warping them by tacking and cooling and moving around. Working a deal right now for a set of lower sliders, not many spares around. I have the wheel and once I have sliders and calipers I can start the process without having the bike here. Just need some measurements for the axle.
 
#21 ·
what size wheel are you fitting to the front?

changing the standard size often ends up with a worse handling bike.
The standard Triumph disc could lock the front wheel

I am 99% sure that the original fork lowers are steel.
They moved to alloy when the frames went OIF
 
#25 ·
Just for reference you can see what little clearance I have between rotor and slider on the Ceriani/Kimtab set up. The rotor specific bolts have a thin head or they would hit the slider:



Spacing between fork tubes is only 5.25", so fitting this same set up onto the Triumph shouldn't be a problem:



I'm basically trying to end up with this same type set up on the Tiger:

 
#27 ·
I found a set of used legs for $60. They have 6" extended forks in them. I had the seller pull the sliders off because I have no use for extended tubes and don't want to pay the added shipping for the larger size and weight and I don't want to bother flipping them on eBay. Unless someone here needs them.
Anyone here have a set of sliders for cheap?
 
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