Aprilia Tuono Rear Shock (Sachs)

[treybrad]

Yes but what is your free sag? I suspect you have none which is important.

Hmm, it's between 15-20mm, which seems in the ballpark. You're saying yours doesn't sag at all with the weight of the bike?

Edited to add, this is with all three bags mounted, measured directly above the rear axle. I get another ~20mm of sag when I plop myself on the bike.

trey

 

[Ruggybuggy]

Hmm, it's between 15-20mm, which seems in the ballpark. You're saying yours doesn't sag at all with the weight of the bike?

Edited to add, this is with all three bags mounted, measured directly above the rear axle. I get another ~20mm of sag when I plop myself on the bike.

trey

Nope. When I knock the bike off the centre stand the shock is topped out. I visited a few suspension sites and as I understand it if you have no free sag then a heavier spring is required. I had to crank down the 170mm X 115nm spring down too a point to where the it leaves next to nothing for free sag. From what I've learned choose a spring that will give you 3-5mm of free sag. This will give you the correct spring to start with then adjust preload to achieve rider sag. Rider sag for sport bikes and a firmer ride 30-35mm and longer travel suspension bikes 35-40mm.

This guy sums it up pretty good.
[video=youtube_share;F4dEjzbJoHE]http://youtu.be/F4dEjzbJoHE[/video]

His next video convinces me that a heavier spring is needed base on the position of my adjustment rings.
[video=youtube_share;J01dD727Sy0]http://youtu.be/J01dD727Sy0[/video]

I did try to call KFG racing today but they where closed but will call them in the morning. Ideally a 150mm X 120-130nm spring would work or maybe a 180mm X 12-130nm spring. My understanding is they don't make a 150mm X 120nm spring so I'll see what they suggest.

 

[Ruggybuggy]

After some careful measuring I set the free sag to 5mm and was able to acheive a rider sag of 40mm. This is a little on the high side but acceptable. One thing that is out is the preload on the adjustment. I'm adjusting my 170mm spring down to 143mm and the spec is around 15mm. I think that the 180mm X 120nm spring would be perfect for a ride of my weight (175) but the 170mm X 115nm spring would work for those lighter riders wanting a plush ride.

 

[Antarius]

That guy above is Dave Moss and I was one of his sponsored racers in 2013. Great guy, unbeliebably knowledgable.

Fyi, a 150mm spring won't get heavy enough. Hence why the longer springs were neccesary.

 

[Ruggybuggy]

That guy above is Dave Moss and I was one of his sponsored racers in 2013. Great guy, unbeliebably knowledgable.

Fyi, a 150mm spring won't get heavy enough. Hence why the longer springs were neccesary.

I remembered you mentioning that before so I think I'll try the 180 X 120. Wonder if KFG will take the 170 back? if not so be it, I knew this might happen going in.

 

[Antarius]

I remembered you mentioning that before so I think I'll try the 180 X 120. Wounder if KFG will take the 170 back? if not so be it, I knew this might happen going in.

Id ride it first .

 

[Ruggybuggy]

I would love too but we have 2' of snow and -20C. I'm taking the NC to Florida after New Years for three weeks but won't be able wrench on it. Personally I think it will work fine but it's not perfect and I have a bad case of OCD. Wife and friends point that out but I don't see it.

 

[treybrad]

Interesting, sounds like my free sag is a bit too much. I'll snug down the preload a bit more and see what happens to my rider sag -- maybe that'll firm it up a little bit more.

trey

 

[treybrad]

Well, I may have solved some of my complaints about the spring being soft. Either it settled a bit, or I just didn't measure it right the first time.... oops.

I had more like 25mm of free sag, and when I sat on the bike I was pushing 55mm. I added a few more turns of preload and now I'm at ~10mm of free sag, and ~42-43mm of rider sag, around 28% total travel.

While I was at it I went another 5 clicks harder on the damping, I'm now about 5 clicks from max. Where is everyone else at with the damping? I'm thinking the heavier spring is making me need to crank the damping up.

Curious to see how it feels on the way to work tomorrow.

trey

 

[Antarius]

You will need more rebound damping with a stiffer spring, you are correct.

28% and 10mm seems solid though! Good work!

 

[Ruggybuggy]

I contacted KFG racing today and ordered up the 180mm X 120nm spring and I'll see what the numbers are on that one. I never considered the rebound damping setting and it might be close to max for the 120nm spring. I do have a buddy that rebuilds snowmobile shocks and I'm sure he could revalve or add thicker oil to get the damping under control if I end up at the max setting.

The main reason I went with the 180mm spring was to bring the adjustment rings more to the middle point of the shock .

Just curious but has anyone measured the full compression of the suspension with the Sachs installed? Do we lose, gain or stay the same?

 

[Antarius]

I believe the shock has 5.4 inches of travel compared to 5.9 inches on stock -- but same eyelet to eyelet dimensions. This means no ride height change, and only 1/2" of reduced travel.

I contacted KFG racing today and ordered up the 180mm X 120nm spring and I'll see what the numbers are on that one. I never considered the rebound damping setting and it might be close to max for the 120nm spring. I do have a buddy that rebuilds snowmobile shocks and I'm sure he could revalve or add thicker oil to get the damping under control if I end up at the max setting.

The main reason I went with the 180mm spring was to bring the adjustment rings more to the middle point of the shock .

Just curious but has anyone measured the full compression of the suspension with the Sachs installed? Do we lose, gain or stay the same?

 

[Ruggybuggy]

I believe the shock has 5.4 inches of travel compared to 5.9 inches on stock -- but same eyelet to eyelet dimensions. This means no ride height change, and only 1/2" of reduced travel.

That's 1/2" at the shock. I wonder what that translates too when measured at the swing arm?

 

[Antarius]

That's 1/2" at the shock. I wonder what that translates too when measured at the swing arm?

I'd imagine its only a 0.5" loss since we're using the stock linkages? Good question.

 

[treybrad]

That's 1/2" at the shock. I wonder what that translates too when measured at the swing arm?

Where are y'all coming up with the numbers? I know 5.9" is the quoted travel at the wheel for the NC, I'm assuming 5.4" is the travel quoted for the Tuono at the wheel?

If so, and the eye to eye length is the same, I'd expect the travel to be the same, or no? Maybe a slight difference in shock construction, but I'd bet the difference in travel between the two bikes is mainly from linkage differences.

Or I could be wayyy off course

I'm much happier with mine after the adjustments I made last night. Firmed it up a good bit more, now it's right where I want it, if not a little too stiff. I'll leave it alone for a while and see what I think with time. Nice to know it's just a matter of fine tuning to get it where I want it.

trey

 

[Ruggybuggy]

The new spring came in from KFG. I installed it Saturday and learned a few more things about the swap. I went with the 180mm X 120nm spring and my sag numbers are perfect. The spring leave plenty of adjustment so it should work for heavier riders.


First the springs. The 180 is to the left, 170 in the middle and the stock 160 Tuono spring is the right one.

This is the 170mm X 110nm spring installed and set to my sag (175lbs). You can see where the adjustment rings are set and I wasn't able to achieve proper free sag when the proper rider sag was set.

This is the 180mm X 120nm spring installed and notice now where the adjustment rings are set. This was close to where the rings are after sag was set.

I disassembled the NC's shock to see what I was working with and I was amazed how strong the spring was. I used a large spring compressor at work and it took some effort to compress it.

Comparison of the NC and Tuono.

I compared the two shocks and they are identical in both length and compression. The Tuono's shocks adjustment screw does both rebound and adjustment. Turn the adjustment screw out and compression is very easy and it rebounds almost instantly. Turn the screw all the way in and compression very difficult and rebound is very slow. Set the screw to a little over half way and it's similar to the NC. The screw has 42 positions and my final setting was 30 clicks in.

You can see how the stroke is the same and I did measure it and found them to be almost the same.

This is the Tuono shock installed on the bike with the 170 spring and for comparison the bottom picture is the 180 spring installed with the correct free sag and rider sag. Note the position of the adjustment rings. I set free sag to 5mm and rider sag was set to 38mm. My weight is 175lbs.

There is only one issue with using the shock that hasn't been discussed. The Tuono (Sachs) shock uses a rubber mounted bushing on the bottom and the NC uses a bushing with needle bearings on the bottom. How long will that rubber bushing last used in that position? The Sachs does have a needle bearing arrangement but in the top position when mounted to the NC.

 

[Garnet]

Hagon shocks have had some failures which has been blamed on the lack of needle bearing on the bottom. On some bikes the bushing does not allow enough pivoting action and the eye eventually breaks off the shock. Not sure if anyone has had this problem on an NC. The Tuono suspension must pivot more at the top of the shock than the bottom.

I would monitor the state of the bushing closely. Perhaps a grease fitting could be added. Is there a chance that the shock is mounted the other way up on a Tuono?

Thanks for all the great pics.

 

[Ruggybuggy]

Hagon shocks have had some failures which has been blamed on the lack of needle bearing on the bottom. On some bikes the bushing does not allow enough pivoting action and the eye eventually breaks off the shock. Not sure if anyone has had this problem on an NC. The Tuono suspension must pivot more at the top of the shock than the bottom.

I would monitor the state of the bushing closely. Perhaps a grease fitting could be added. Is there a chance that the shock is mounted the other way up on a Tuono?

Thanks for all the great pics.

The shock on the Tuono is mounted in the same position, adjustment rings up. The Tuono uses a triangular wishbone set up and the bottom of the shock would experience movement.



I did loosen off the bottom shock bolt when I mounted it on the NC and worked the suspension to check for binding and didn't experience any. I think chances of the shock breaking off are remote. The more likely cause would be that the rubber would twist and fail over a period of time.

Disclaimer: But what do I know, I'm not an engineer but I did stay at a Holiday Inn.

 

[LM15]

Thank you Ruggybuggy for all the research, information and photos you have provided on this subject. I, as well as others, appreciate your efforts.

 

[Antarius]

Yup. That's super good info.