Measured Front Fork Travel

[YamaPA]

Moderators...feel free to move ths to technical forum if you feel its a better fit.

I've got a cable tie on my front forks which allows me to measure my fork travel usage. I routinely use up 6.5 inches of travel (as measured with the bike on the center stand, the front wheel off the ground and measured from the botttom of the dust wipe to the top of the cable tie), but cannot for the life of me use up that last supposed .98 inches of travel.

I havent been inside the forks to check oil level which may or may not be too high (which increases the air pressure which stiffens the fork compression near the end of travel ). I can ROUTINELY use up 6.5 inches, but never exceed that usage even when purposely trying...and yes, I try damn hard. Hmmmm I say. Am wondering has anyone else ACTUALLY MEASURED their travel usage? Please do NOT tell me I havent hit a bump large enough to use the full travel......I weigh in at 215 lbs. naked (get your ice pikes out for that mental image) and unless I drop the bike on the front end from 50 feet up, it simply is not using it up...on or off road.

If you HAVE NOT ACTUALLY measured your travel, please do NOT comment.

 

[Firefight911]

Max measured travel, and I've tried as well, has been 175 mm. Total available is 190 mm.

We'll see if I can get some measurements as we go in to the forks on Thursday to see what is really in there compared to the service manual specs.

 

[YamaPA]

Thanks for the reply. So, you got 6.88 inches of measured used travel and I got 6.5 inches. Hmmmmm. I'm willing to be there is a rubber bump damper at the bottom of the forks or a hydraulic bottoming cone. I would appreciate you telling me what's in there as well as what the measured travel would be without the spring installed. If I was going to be in there, I'd measure the oil left after the spring was removed slowly (so as not to withdraw too much oil on the spring) and then when I refilled it, I'd probably use a distance of 20 mm MORE to the oil level. You can easily add oil anytime in 10 cc units. Thanks again.

 

[biting_point]

i didnt measure my fork travel, but just did a shot of the forks..
it seems to move a lot during turning..

go pro low angle.mov

 

[3putt]

I run with a zip tie on my forks from day one. Did some pretty rough off road last summer in CO. and never got over 6-1/2" or so, plus broke my fender.

I changed out the dual rate spring for a .95 and now get full travel but only on severe hits like a ditch. Full travel is like 1/2" from the bottom.

My weight is 180 lbs without gear.

I suspected the oil level was off at first also, but found it was in specs (150mm).

http://www.yamahasupertenere.com/index.php?topic=2811.msg48498#msg48498

 

[YamaPA]

If someone has the forks apart and is willing to take accurate measurments, orient the spring on a desk and keep it one position. Start measuring all the gaps between the coils and sum up the total. If its less than 7.48 inches, we are having coil binding issues....simple as that. If we get more than 7.48 inches space between the gaps, then it is likely a fluid level issue.

If Tiger one CHANGED HIS SPRING and now gets full travel......hmmmmmm.

 

[Firefight911]

I'll measure them once I get home. I will say that the new springs have quite literally transformed this bike's front end.

I need to spend time with tuning now but......wow!!!!!

Not sure if it's bind or hydraulics but we'll sort it out.


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I am here: http://maps.google.com/maps?ll=38.004768,-122.532702

 

[3putt]

There are 38 coils if you count the ends, .230" OD so if you could fully compress without distortion, it would be solid at 7.99" travel. Now this is starting from fully extended spring, if you take into account the preload when at the top of the travel to support the weight of the bike, then maybe less than 7" total travel.

Spring length is 16.73", minus (38 coils at .230" thick) = 8.74" = 7.99" left for travel not counting preload.

P.S. If I change anything in the future it will be raise the oil level to 160mm when I change the oil.

 

[YamaPA]

There are 38 coils if you count the ends, .230" OD so if you could fully compress without distortion, it would be solid at 7.99" travel. Now this is starting from fully extended spring, if you take into account the preload when at the top of the travel to support the weight of the bike, then maybe less than 7" total travel.

Spring length is 16.73", minus (38 coils at .230" thick) = 8.74" = 7.99" left for travel not counting preload.

P.S. If I change anything in the future it will be raise the oil level to 160mm when I change the oil.

Good job Tiger! Thank you.

So, what we have learned from this little experiment so far it that it is probably unlikely (not definite, but unlikely) that in stock form with stock springs you will get the full advertised front fork travel of 7.48 inches. Chances are that the spring has some preload (and I would probably guess at 25 mm or 1 inch although I could be wrong as I have not been inside my forks to date) and as such we get our answer of 6.99 inches of travel (with 1 inch or spring preload). We will get more than 6.99 inches of travel with less than 1 inch of preload and less than 6.99 inches of travel with more than 1 inch of preload. But anything more than 0.5 inches of spring preload will not allow us to get full travel of 7.48 inches.....plus of minus tolerances for spring manufacturing, etc.

With the above said, I decided to call Yamaha technical support this afternoon to see what info they had available. I spoke with Meagan. She did some reasearch in to their manuals, etc. and said she did NOT have the preload on the spring. The only info I got from her which was of use was that the spring free length is 16.83", not 16.73"......can one say that is a result of spring sag or manufacturing tolerance difference? I then relayed the jist of the above information to her saying "how do we verify this to be a problem or not?". She said approach your dealer with the inquiry and they will contact Yamaha. So there you have it folks. I have a call into my dealer already to see what they think.

Here is the thing, and be mindful that I have not been inside the forks to date......if we are indeed achieveing coil binding before full travel is reached, such is not good on the spring seat (which is really part of the top part of the cartidge on a normal cartridge type fork) and the fork cap. These devices (the spring seat more so than the fork cap) are not designed for the load pressures when a bike of this weight bottoms, and such, I can see after repeated bottomings the catrtidge actually failing down the road.

If anyone has their forks apart and can measure spring preload with the stock spring in place and the adjusters backed full off, please do so.

 

[Firefight911]

Interesting stuff.

Of course, I had the forks apart yesterday so can not now measure for you. In installing the new springs, we matched the free length of the stock springs with a manufactured spacer. At this point I have the preload adjusters run all the way out but have not gone through the proper process of setting my race sag, etc. More to follow....

 

[3putt]

[quote author=YamaPA]
She did some reasearch in to their manuals, etc. and said she did NOT have the preload on the spring. The only info I got from her which was of use was that the spring free length is 16.83", not 16.73"......can one say that is a result of spring sag or manufacturing tolerance difference? No, this mistake is from my lack of memory and not referring to the service manual.

If anyone has their forks apart and can measure spring preload with the stock spring in place and the adjusters backed full off, please do so. Preload is such that a spring compressor is needed, where I have been able to pull it down my hand (using the puller) on other bikes.
[/quote]

On assembling my new spring from Traxxion, they recommended 15mm preload, so would expect the actual compression of the OEM spring would be similar.

I learned that the OEM springs were not going to full travel well before I decided to replace the springs. Ziptie NEVER got more than 6-1/2" travel or even less. You can put a zip tie on your forks and check it, not hard to do. Course you may not want to break your fender in half in doing the test as I did. LOL.

P.S. The spring seat at the top is a plastic spacer, I finally cracked mine through removing and installing several times, so made some out of T6 6061. My previous link shows the plastic spacer in the pics.

 

[YamaPA]

Tiger One,

The 16.73 vs. 16.83 may or may not be your error.....did you actually measure the spring (its next to a ruler)? The difference can be a manufactuing tolerance difference or spring sag. If the spring measures even LESS than 16.73, it provides less space before coil binding.

I do not understand why you cracked your front fender. At 6.5 inches of used travel, there is plenty of clearance for the fender. What do you think caused the fender to crack?

Great, we have a plastic spring seat. Nice. Am sure mine is hosed already as a result of the bottoming. Thanks for that bit of info.

 

[3putt]

Actually the preload can be figured in my link where I documented the install of the 14" springs. I measured 61mm with preload adjuster completely backed off all the way, but with 2 washers. Remove the washers and you get another 5mm or 66mm total.

16.83" - 14" = 2.83"
66mm = 2.6"

So with the preload adjuster all the way backed off = .23" preload, so little over a 1/2 " with stock preload or there a bouts.

 

[YamaPA]

I should have asked above....

....what is the ID of the stock spring and what is the OD of the stock spring? It's time for me to source an aftermarket spring I do believe.

One last question....is the .95 rate spring good for you, or would you have preferred a stiffer spring in hindsight?

Thanks

 

[3putt]

I would be willing to bet that you have not cracked the plastic spacer. My hamfisted work on disassembly and reassembly finally wore it down on mine. Regular service should not hurt it.

Yes, my spring is about 16.83 (using a ruler). The tolerance for wear in the manual is 16.49".

There is NO spring to replace it with. You must choose your weight or get Traxxion (or another suspension shop) to choose for you, and then they can order a custom spring made. Traxxion has done at least a couple so they have some history. Firefight911 used a local shop and they sourced/ordered a custom spring.

I documented breaking my fender in another thread, but basically, due to extra weight of the "FenderExtender" and some VERY hard hits on rough off road rocky terrain. My fender flexed and then cracked at the lower mount point. I was able to apply electrical tape in the field and it held to get me home (about another 1200 miles). I repaired it with carbon fibre on the inside and am still using it on the bike today. A battle scar.

 

[3putt]

I should have asked above....

....what is the ID of the stock spring and what is the OD of the stock spring? It's time for me to source an aftermarket spring I do believe.

One last question....is the .95 rate spring good for you, or would you have preferred a stiffer spring in hindsight?

Thanks

ID at the top where it slips over the spacer = .910" at the bottom it is 1.060" ID (tapers slightly at the top) But, I used spacer of PVC and washer at the top so didn't matter.
OD is 1.525" at bottom and 1.512" at the top.

 

[Firefight911]

My springs were sourced by James at Super Plush and they came from Traxxion Dynamics.

I am running a .95kg/mm linear rate. We put a spacer in that created the length to match the stock spring free length at this point. The preload adjusters are run all the way out at this point but I have not spent the requisite bench time to get the numbers set properly for sag.

Fork oil height matched stock specs per the manual.


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I am here: http://maps.google.com/maps?ll=38.670485,-121.145857

 

[YamaPA]

I was looking to source a spring and revalve the front end this winter, so I did some digging around. I know Traxxion was mentioned above, but I have also used RIch at Sonic Springs in the past. I have a phone meeting scheduled with Rich for tomorrow. In the meantime, I called Race Tech and after 3 days of trying to get the person I wanted, I got his secretary who supposedly butted him during a meeting and wast told....they have developed a "kit" for the Super Tenere, but is is not available for sale at this time. I was told it will be available in 30 days. That is all I have on that piece of info.

 

[fredz43]

I'll be going to the Indy Dealer Show the weekend of Feb 17-19. Race Tech is always there and I'll make sure to talk to them abotu what they might have for the Super Tenere.

 

[GoNotShow]

I was looking to source a spring and revalve the front end this winter, so I did some digging around. I know Traxxion was mentioned above, but I have also used RIch at Sonic Springs in the past. I have a phone meeting scheduled with Rich for tomorrow. In the meantime, I called Race Tech and after 3 days of trying to get the person I wanted, I got his secretary who supposedly butted him during a meeting and wast told....they have developed a "kit" for the Super Tenere, but is is not available for sale at this time. I was told it will be available in 30 days. That is all I have on that piece of info.

Sweet! Looking forward to seeing what Race Tech has to offer. I can't wait to ditch the dual rate spring and drop in some new valves.