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Installing forks that have MORE travel than stock

Q

quasi888

Moto babies
Joined
Jul 31, 2003
Location
Roseville, CA
Moto(s)
'12 Aprilia Shiver 750
Name
Dave
Greetings all.

I have just acquired a '12 Aprilia Shiver 750. Its front suspension is non-adjustable (not even for preload). On top of that, the Marzocchi-manufactured forks are essentially non-serviceable, and there are no aftermarket cartridges/kits available for it.

Other Shiver users have replaced their forks with 06-10 Tuono 1000R forks, which match the 51mm/53mm upper tube diameters, are adjustable, and have far more upgrade kit/catridge options. But these can be a little hard to find in good condition. This would also require the same Brembo calipers that came with the Tuono, another added expense.

I'm currently looking at a set of Aprilia Dorsoduro forks as an alternative. The Dorsoduro and the Shiver (both discontinued models) shared the same overall platform, but the DD was a little more supermoto focused, and had slightly better forks with preload and rebound adjustability. (And they're gold! Always a bonus.)

However, being more SM-focused, the DD had longer forks. Overall length is ~2.5" longer than the Shiver forks. Since I want to maintain the same overall ride height / geometry that I currently have, I can of course just raise the fork tubes in the triples. (I'll likely have to get rid of the MX-style forks and install riser clip-ons, though.)

But the DD forks also have longer travel -- 170mm, to be exact, compared to the Shiver's 120mm.

So I have 2 questions:

1. If I'm going for rider sag of, say, 35% of total travel, I'd just be dialing in preload for ~60mm of sag (as opposed to ~40mm on the 120mm Shiver forks), correct?

2. Assuming I've dialed in the correct amount of sag in #1, are there any downsides at all to having more travel "on tap"? Common sense tells me no, but just want to make sure.

Thanks in advance!
 
1. No, not really. If you put the forks at the stock ride-height and then use 20mm more sag, the front suspension position is now 20mm lower all the time. That's way too low and will ride poorly. Id much rather start with 40mm sag. But even that will probably suck.

2. Yes there can be consequences. The main problem is that a lot of street bikes will slam the fender or tire into the radiator/exhaust/engine with too much travel. A less severe but still problematic issue is with dynamic suspension position and how it rides. Too little suspension height when braking hard because of soft springs feels terrible.

Suspension travel, chassis geometry, and suspension setup (springrate, preload, damping, bottom-out control) all go hand in hand when making a motorcycle feel 'right' when riding. Most bikes will feel normal if you only change a few things a little or change one thing a lot. 20mm is a large change. Putting forks onto a bike that has a different use-case is a huge change. It likely the the longer SM forks have significantly lighter springs since they have more travel to use. They also probably can't add enough preload to get to 40mm sag, since they were designed for 60mm sag. The bottom-out control on SM forks will be way different. And the damping will be suited to the longer travel & lighter springs. Because of these large changes, you have no chance of keeping the dynamic geometry anywhere close to stock with the new forks. And it probably won't ride well.

A lot of people in this situation sometimes go with an entire front end swaps - Forks, triple, axle, wheel, brakes. Best case, the steering stem is the same. Medium case, you get new stem bearings or swap stems. Worst case, you get a new steering stem machined and pressed into the new triple. If you pick a common bike, this can be cheaper than using parts that are hard to find or require extensive modification.
 
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Thanks Robert. You've touched on some things that I subconsciously had a hunch would be true, but was really hoping would not be. But it makes sense.

Guess I'll go back to looking for a set of old Tuono forks.
 
If all else fails, someone can make that swap work well. Springs can be changed. Damping can be adjusted. Travel can be shortened. A great suspension tuner could probably guess at the necessary changes and it would probably work better than OEM. It just costs time and money. I'd guess a good tuner would charge you almost $1000 to shorten the travel, re-valve, and re-spring the new forks.
 
You can shorten travel and length on those DD forks.
You can also put cartridges in your stock forks, like modified gsxr cartridges I do for damper rod forks.
 
TWF said:
You can shorten travel and length on those DD forks.

You can also put cartridges in your stock forks, like modified gsxr cartridges I do for damper rod forks.
Click to expand...

Zoran! Good to see you still around! (I am coming back from a 10+ year hiatus from riding, but you helped me out with some SV upgrades years ago.)

Your words intrigue me. I suppose anything is possible with time, money, and expertise, but I'm trying to come up with the most cost-effective way to get upgraded forks on this bike.

I like the look of the DD forks, and the fact that I can re-use my existing calipers. But this sounds like quite an operation to shorten their overall length AND their travel.

With regard to my stock forks, as I mentioned, they are Marzocchis. Over the years, Shivers have come with Showa, Sachs, and Marzocchi forks, and I have not seen any aftermarket companies make any cartridges/kits for the Marzocchis.

If you have any ideas, and/or if you would be able to offer any services for such a project, please feel free to PM.
 
quasi888 said:
I like the look of the DD forks, and the fact that I can re-use my existing calipers. But this sounds like quite an operation to shorten their overall length AND their travel.
Click to expand...

Actually it is pretty easy and simple to shorten them.
Are DD Marzocchi as well?
I will pm you with some info tomorrow.
 
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