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Hey guys, it's been a minute since I've been active here, but I'm hoping to get some fresh new advice from the community.

I have a 2010 Street Triple with forks swapped from a 2008 Daytona with Traxxion AK20 cartridges. I recently took the forks in for service and my mechanic recommended that the lower tubes be replaced. That's an expensive part to buy new, so much so that I could more or less get an entire used fork assembly, so I'm looking for other options.

I've seen some options for lower tubes for 13+ Daytonas and STRs, and my question is, are these compatible with the 06-08 Daytona forks? I know that lower tubes are compatible among all of the different 1st gen models, and it seems like the 13+ parts are the same dimensions, but I can't seem to track down part numbers to confirm.

Also, a bonus question: are my AK20 cartridges compatible with a 13+ STR fork set if I go that route?

Thanks a million!
 

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Hi,


I do not know anything about the AK20 cartridges, but I swapped the fork of my Standard Street Triple to a 2007 Tuna fork in 2016 and in 2018 I got hold on a 2016 STR RX fork which

I use since then. I serviced both forks this winter, despite the colour, both are identical.


Hope this helps.


Best regards
Dirk
 

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I assume by lower tubes you mean the stanchions (chrome tubes). In short there are 3 different stanchions used on Daytonas and ST3s. There is the standard non-r ST3 stanchion, there's the Daytona R Ohlins stanchion, and then there's the rest. ST3 non-r *should* only be used on ST3 non-r forks, Daytona R can only be used on Daytona R, and the rest are interchangeable.

To answer the bonus question, yes, the AK20 cartridges you have can be used in ST3R forks.
 

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I assume by lower tubes you mean the stanchions (chrome tubes). In short there are 3 different stanchions used on Daytonas and ST3s. There is the standard non-r ST3 stanchion, there's the Daytona R Ohlins stanchion, and then there's the rest. ST3 non-r should only be used on ST3 non-r forks, Daytona R can only be used on Daytona R, and the rest are interchangeable.

To answer the bonus question, yes, the AK20 cartridges you have can be used in ST3R forks.
Hi Renboy,

Do you mean that a 2012 Daytona 675 (gen 2) stanchion is the same as 2006-2008 Daytona 675/street triple 675R (gen 1)? I have removed the stanchion from fork leg casting on an 2008 Daytona. The Thread pitch is 1.25mm. Im about to buy a 2011>2012 stanchion online but they dont want to measure the threads for me. I know that on the outside, the gen 2 has a different fork leg casting than the gen 1. Have you ever fitted a gen 2 stanchion to a gen 1 fork leg casting?
 

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Hi,
sorry Renboy, but that is not true. The Gen 1 and 2 Daytona inner tubes have the same thread, but the length is different. Gen 2 is 538 mm long, Gen 1 528 mm. The exchange will work , but you will get 10mm less fork travel if you use a Gen 2 tube on a Gen 1 fork . The other way round you will need a spacer underneath the TopCap, otherwise the cartridge can be damaged when bottoming out.
 

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I thought they were both 528mm. The Ohlins Daytona R tubes are 538mm. I'll measure tomorrow as I have a 1st gen already apart, and I'll drop the outer tube on one of the spare 2nd gen forks I have here. I won't get an overall length, just the length above the casting. The section in the casting will be the same.
 

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Hi,
I have both Gen tubes (unfortunately bent slightly) apart lying around. I measured them they are definitely 538 and 528mm. Street triple up to 2012 is 525mm.
Hi Dirk,

Are you sure Gen 1 (2006-2008) is 528mm long and Gen 2 is (2009-2012) is 538mm long? If so, it means Gen 2 would have a deeper thread in the casting. I am looking online and aftermarket stanchions are both advertised 528mm long for both Gen 1 & Gen 2.
 

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Yes this is 100% sure, if this means the fork after 2009, that has the High and Low speed adjustment in the fork bottom casting, the darker golden/bronze outer tubes and the wheel axle thread on the opposite side. You won't find aftermarket tubes with the original length for this fork. I had contact to TNK in Italy concerning this.
Best Regards
 

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Yes this is 100% sure, if this means the fork after 2009, that has the High and Low speed adjustment in the fork bottom casting, the darker golden/bronze outer tubes and the wheel axle thread on the opposite side. You won't find aftermarket tubes with the original length for this fork. I had contact to TNK in Italy concerning this.
Best Regards
That is strange from TNK. Do Gen 1 and Gen 2 have the same o-ring face area and thread length? Both would have 1.25mm pitch?

Please do take pictures, I would really appreciate it. Thank you.

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Hi Thomas,
thread and o-ring area is identical. I used Daytona Gen2 fork-castings and cartridges with street triple chrome-tubes before. These and the Gen1 tubes are only a little shorter, and you need a spacer-ring to avoid destruction of the damper when bottoming out. This is because the mechanical bottom-out stop is when the upper end of the inner-tube hits the rigid Top-Cap. If the inner-tube is shorter, the sensitive damper-rod hits the end cap of the cartridge-tube before. You can try this very simple:
1. Mount the cartrige into the fork bottom
2. Screw the crome-tube into the fork bottom until it is in its seat
3. Screw the top-cap onto the damper-rod, until it has the correct position concerning the rebound adjauster
4. Now slide the damper into the bottom-out position.
If there is still a gap between the chrome-tube and the top-cap, measure it and add 2 mm for security......this is the thickness you need to avoid bottoming -out onto the damper-rod .
 

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Yes this is 100% sure, if this means the fork after 2009, that has the High and Low speed adjustment in the fork bottom casting, the darker golden/bronze outer tubes and the wheel axle thread on the opposite side. You won't find aftermarket tubes with the original length for this fork. I had contact to TNK in Italy concerning this.
Best Regards
What was TNK response?

Hi Thomas,
thread and o-ring area is identical. I used Daytona Gen2 fork-castings and cartridges with street triple chrome-tubes before. These and the Gen1 tubes are only a little shorter, and you need a spacer-ring to avoid destruction of the damper when bottoming out. This is because the mechanical bottom-out stop is when the upper end of the inner-tube hits the rigid Top-Cap. If the inner-tube is shorter, the sensitive damper-rod hits the end cap of the cartridge-tube before. You can try this very simple:
1. Mount the cartrige into the fork bottom
2. Screw the crome-tube into the fork bottom until it is in its seat
3. Screw the top-cap onto the damper-rod, until it has the correct position concerning the rebound adjauster
4. Now slide the damper into the bottom-out position.
If there is still a gap between the chrome-tube and the top-cap, measure it and add 2 mm for security......this is the thickness you need to avoid bottoming -out onto the damper-rod .
I was exactly planning on finding out the mechanical bottom out position as you explained. I just need chrome tubes now. Thank you for the pictures, helped me a lot to decide. Danke.
 

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You're welcome. TNK answered, that they do not produce chrome tubes for KYB 41 USD forks with a length of 538. For Daytona 675 Gen2 they produce 43mm tubes for R/Ohlins forks only. They also have 538mm KYB tubes with 538mm length for older Speed Triple models.
 

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So we have a discrepency here. Sorry it took so long, but I finally got around to checking the fork tubes. As mentioned earlier I could only get a measure of the length of tube outside the casing. On the gen 1 fork I already had a fork apart so that was quick and I got a measurement of 491mm. On the gen 2 fork I measured by lowering the outer fork tube and measuring from the top of the slid down tube down to the casting and adjusting for the 1mm difference that the outer tube sits higher than the chrome stanchion. In that case I got a measurement of 490mm. And to be sure I checked and the casting overall height is the same (when comparing appropriate sides). I can only assume that the 1mm difference between the two tubes can be accounted for by manufacturing tolerances of both the tube and thread depth in the casting.
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Hi Renboy,
the seat of the stanchion in the bottoms differ, that is the point.
Gen 2: stanchion length: 538 mm
- seat depth: 48 mm
= free stanchion length: 490 mm

Gen 1: stanchion length: 528 mm
- seat depth: 38 mm
= free stanchion length: 490 mm

The difference of 1mm you measured is just caused by measuring accuracy I think.
Here is what I measured, when I took the Gen2 fork apart:
 

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After thinking about this a bit, I can completely understand that the ST3R forks are a different length than the Daytona forks given that the ST3R has more rake/trail than the Daytona. But I can't see how the 1st and 2nd gen Daytona forks would differ in stanchion length since the outer tubes are the same length, and the castings are almost identical. In the following pics you can see that the right fork casting from the 1st gen is the same (compression adjuster aside) as the left fork casting from the 2nd gen. I know the castings were changed between the generations so that the pinch bolt side and threaded side were reversed I assume so that no one could use one 1st gen fork and one 2nd gen fork on the same bike. The second pic shows the difference in length of the casting from the same gen but different side.
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