The Definitive USD Fork Conversion for Sprints Thread

[ibslo]

Ken, thanks for the offer, I may take you up on it. I'm going with convertibars or maybe lsl with risers. have seals and bearings coming. it will be a few months before i get all the parts together. will take pics as i go along. You have made it so i can get everything ready to install with much less downtime for the Sprint. Cheers, Maury

[DEcosse]

Originally Posted by ibslo

... I may take you up on it. I'm going with convertibars or maybe lsl with risers. ...

Do you have the TLS top clamp already?
Or just forks & Triple Tree?

If the former, you might save the money on the LSL kit - I simply drilled the TLS top clamp as you'll see in post #6.
It is about 7mm thick there so plenty of material to work with & be substantial.

Then all you need to add are risers and bars of your choosing - you can even go with Fat (29/22 Conical) Bars if you like (LSL clamp kit has only 22mm, no choice there).
I have Rizoma bars & risers on an OEM GSXR top clamp on both my TL & SV (well actually the SV is a 'std size bar on OEM SV risers while the TL has the Rizoma risers and bars) Risomas are super nice (have them on all three bikes!) but they are expensive.
At BikeBandit - where you can use our TriumphRat -10% coupon! - you can get ProTaper Risers and Renthal or Protaper Contour or Protaper Evo bars for already discounted prices less ANOTHER 10%!

Of course the Convertibars - like OnD's have the advantage of adjustability. Not cheap though!
OnD won't mind me saying - he already had made the Convertibar switch with his OEM forks.
So his delta for the fork conversion 'only' involved the new 50mm fork clamps which he was able to buy stand-alone
(nice feature by Convertibar to allow this without having to buy full new kit!!! )

.

[dolson]

Tis good enough to rate a stickie Ken with OnD's help. Good on both of you.

Don

[oldndumb]

While I appreciate the kind words, DEcosse deserves all credit. He was the one that did the computations that determined the TL set would fit. All I did was the grunt work and the money.

While I did replace the fork seals, I left the springs as they were to determine a baseline for future enhancements. I played around with the settings until I arrived at something that suited me around town. I am not a suspension guru, but I know that it was a big improvement over the ST forks as regards keeping the rubber in full contact with the road.

I have done two track days with the stock TL forks and am satisfied with them. The first 30 minutes had me a bit concerned, but after playing with the adjustments I was confident enough to get edge to edge use of the tires. A better rider would benefit from a re-valve kit, and would drop their lap times. But since I am not an expert rider, I am happy with it as is.

My hat is off to DEcosse for his efforts and willingness to share his research, computations, and advice. :

[DEcosse]

Originally Posted by DEcosse

.... one of the key assets for this kit is that it involves very few custom parts ...

I'd like to revist this statement from the opening post, which will help define all of the requirements for customization.

Actually there are a sum total of ZERO parts that have to be made from scratch, or even need the complexity of any mechanical drawings!

There are 4 parts that do require some minimal machining work - I would estimate all four should be readily done in an hour by anyone with access to a lathe and a mill.
(can even be mini bench top tools or simply take them to a machine shop).

So take these parts for execution all at the same time - they can even be done while your Sprint is still intact (unless you utilize your original Sprint axle spacer(s) as donors) other than the time you need to remove the ignition - which can be re-installed again, even modified.

These parts and their modification:
1. Ignition Assembly
Machine 5mm off the locking pin (both pin & housing)
Elongate the mounting holes with a file to fit the TLS clamp posts.

2. TLS Top Clamp
Machine 10mm off the mounting posts
Optional - add holes for bar risers.

3. Axle Spacer(s)
One required for early model (12.5mm long)
Two required for late model (13.5mm long)
Either sacrifice the original(s) from your Sprint or buy new ones if you want to keep your bike operational. ($11 for new spacer)
In either case, just machine to length.

4. Collar Nut (Early Model Only requires this - late does not)
Machine collar nut length to remove 14.5mm.
Leaves new length (from inside face of flange) at 58mm, new net will be 43.5mm

5. Bottom Triple Mod (Optional)
If you're going to the machine shop anyway, you may wish to get the OEM steering stop 'nubbins' removed from the bottom triple. This is not necessary unless you choose to use the option mentioned to mount the new stops on this component.
Regardless, it could be done at home with simple tools - file alone even - but I throw this on the list in case you would like to have it done in a mill.

6. Hayabusa Fork Mod - for TL fender (Optional)
This does not need to be done on TL forks (obviously!) and only done on 'Busa if you wish to use TL fender rather than 'Busa.
It can be done at home - does not require sophisticated machining.
Tools required - hacksaw, file, 5mm (or 13/64) drill and M6 tap.
Trim the top (original) front fender mount down flush with the mounting bracket; add an M6 threaded hole per the picture above.
Note that this could still be utilized for a 'Busa fender simply by adding spacer to replace the material removed in the first step.

Once you have the parts above ready to go, the actual 'swap' project can easily be accomplished in an afternoon or plan for a leisurely weekend project.

[DEcosse]

As well as EBay, these sites are probably the best source for TL forks. Hayabusa are much more prevalent on EBay.

Site #1

Site #2


.

[joggele]

WOW! It's a great work ! That's, what I must have


greets
Jürgen

[johnO]

thanks for the great information ! i notice that both the tl and 'busas have oem steering dampers.do you know if these were used in any of the conversions? i never felt the need for one on my RS,however if the usd forks were designed for a damper,i'd be inclined to use one. your thoughts .........

[DEcosse]

None of these conversions from first post had steering dampers.
It should not be necessary - the trail will actually be slightly longer with the shorter offset of the new triple clamps; therefor if you didn't feel need for it previously, you certainly won't after.
With my Speed Triple (approximately same geometry) I absolutely needed the damper with the OEM triumph front end - did not even bother with it after the conversion. There is no tendency to head-shake whatsoever - very stable, yet still responsive to steer.

The steering will certainly feel different - you will likely find much improved feel in cornering, that the bike will stay in the lean you put it in, without tendency to either sit up or fall in adversely.

[DaveM]

Johno I would concur with DEcosse, the Sprint does not need a steering dampener, it is pure bling and would serve no useful purpose on these bikes.

When you have steeper steering angles, the bike weighs 55 kilos less, a shorter bike length and you have more horsepower then I would agree. But you don't have any of those on a Sprint.

I ride my Sprint like a sports bike on a variety of not so good quality mountain roads and so does dolson, the bike is heavy enough with long enough angle and bike length to not require a dampener at all.

DaveM