[Bella749]

As some/most prolly know, the 749R is the odd-ball when it comes to rear suspension. Stock, it has a shorter stroke (56mm vs. 71mm), much stiffer spring and damping, and a flat-rate linkage vs. progressive rate.

So, in my quest to gather as much info as possible, I've spoken to several of the well-known supension gurus and found out some pretty interesting info.

First off, There are 3 different Ohlins shocks that will fit the 749R. The DU301 "triple-adjustable" common to all 749/999 bikes, and two specific 749R shocks that are listed as OEM by Ohlins according to Dan Kyle (forgot P/N's). One of these "OEM" shock is listed as 71mm stroke, and the other listed as 56mm stroke. The standard spring rates for both are much stiffer than that of the DU301 and the valving to suit. All the shocks are 305mm in length.

Next point, info from another well-respected source revealed one particular fast racer running the standard (progressive) link with one of the longer stroke shocks. Apparently, the flat-rate link and short stroke combo, designed to combat rear-end squat, works well on smooth tracks as in Europe, but not so well here on our bumpy tracks here in the Colonies. Makes sense to me, and I may go this route for ease of setup, as I already have some good experience with setting up that combo.

So, for those with experience setting up 749R's in particular, if you wouldn't mind pleease post up some comments on your setup. I, for one, would greatly appreciate it to help me get my bike sorted for the track so I can enjoy the ride and not spend the whole day messing with suspension.

Specifically, for those lightweights (I'm 145lbs), how do you use the recommended 10-12+ kg spring (for flat rate link) and get good sag numbers? My DU301 has a 7.13kg spring and my sag numbers show that is a little light, but not wayyy off. Bear in mind, I have not yet moved the axle beyond the standard swingarm length, and I understand that will create more leverage on the spring, but that big of a jump in spring rate?

Next question is with the forks... I'm going with .90kg springs; how well will the stock valving handle that change, and what oil to use with the R/T forks (weight range? The Showas on my 749Bip handled the change reasonably well after I changed the oil weight and made a very minor change to the stock valving.

Thanks in advance, and Special thanks to Dan Kyle, NCRick (Cogent Dynamics) and Ducshop for their time and information provided.

 

[trussdude]

I raced a 749r and 999r back to back many times. I always preferred the rear end of the 749r.

I ended up making the rear end of the 999r the same as the 749r.

 

[KiwiEd]

Hey Bella749, great post !!! ..... I'm not far from getting my recently purchased 749R ready for the track. Sadly, it was a bit of a dog ... poorly maintained, crashed often and shabby looks ... but the price reflected that so I can't bleat too much. I'm giving it a pretty comprehensive make over so hopefully the past will be the past
I will be addressing the whole suspension issue as well so I will watch this post with interest.
Cheers. Ed.

 

[Bella749]

You used the short-stroke shock, I presume? Run "standard" sag numbers, or any deviation from the norm?

 

[tye1138]

Who would have guessed, I'd be here squakin' about my experiences with this bloody bike!

Anyhow, everyone who races these things, kinda knows the best setup; 30mm offset, lengthen the wheel base. Those are the two magical mods and once you do those, the bike kinda transforms itself into a different creature. Its much more stable at high speeds and seems to steer better at those speeds as well.

I run a .95 front spring and stock spring in the rear. Sag in the front is set to 30mm and shock is set to base Ducati settings, which is basically the same.

When I first got my bike, the suspension had been built by Dan Kyle, I have the receipts. But it had been done 2 years previous, so I decided a few months ago, to have it all re-done again. We altered the shim stack in the forks and shock to compensate for the tracks I frequent. We also replaced the shock's valve and oil level.

What I got out of this was roughly a 2 second per lap decrease in my laptimes. The bike felt like it was on rails after some adjustment's. But I got frustrated with the rear end being so bloody stiff! It was really eating up tires and they were over-heating as well. So I went out and bought a DU315, which is the 3 way adjustable version. It was MUCH better, but it had way too much travel since I got the 71mm version. So I sold it and kept the stock one. Dan Kyle gave me the wink-wink on that shock and said to keep the stock one.

Anyhow, I love my 749R, we connect in a way I've never felt before. I throw a lot of curve balls in its direction and it seems to hit them all. I'm not a very hard-charging motorcycle racer. If the bike doesn't feel planted, I'm gonna ride like a pussy. Thats not to say I can't slide it around, because I can with no problem if I need to. But I need to first feel secure in how the bike performs and thats one thing I love about this bike, it exudes confidence when setup properly. I firmly believe setup is everything on any bike and since Ducati already gives you a pretty decent setup with the 749R, why not continue to use what they've given?



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[Bella749]

Thanks Tye... thanks for that P/N. So, DU 315 is the 749R specific, 71mm version. IIRC, DU324 is the 56mm version, but I thought Mr. Kyle said that too was a Hi/Lo compression model; whereas the OEM shock is lo speed only.

If you don't mind me asking, what is your weight and spring rate? Do you have your free sag vs. rider sag numbers available?

Also, how much ride height you running in the rear measured by the adjuster length. (I really need to get a ride height jig)

I am planning on switching the front geometry when I pull the forks. First line on forks to top of clamp, correct?

Swingarm stops are already ground off, just gotta get a smaller sprocket to move the wheel back. P.O. put a brandnew ZVM2 chain and left the stock length (495mm) with a 40T sprocket... Hoping a 38T will get me to 505mm or I'll have to get a new chain.

 

[tye1138]

The DU 324 is both high speed and low speed. I'm not sure which one has the shorter throw, the D315 has the longer throw, thats why I didn't bother with it.

In terms of my numbers, they won't help you for a few reasons.

One, I'm running 16.5" Dunlop slicks. So not only are my wheels smaller, but my tires are taller.

Two, I weigh roughly 160-165 with gear, which is exactly spec to the 749R's stock shock spring rate, which is a 120nm spring.

Three, I run my wheel all the way back, as far as it can go in the swing arm. That makes my wheel base numbers, totally different.

Anyhow, here are my numbers off the top of my head.

Front ride height (1 ring showing) 620mm (top of triple to bottom of fork tube)
Front Sag 30mm, 6 turns on the preload adjuster
Rear ride height (6 threads showing on both eyes) 254mm
Rear Sag 30mm, 140mm spring preload
Swing arm length 510mm



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[Bella749]

No, the numbers do help, especially knowing what tires you're running. A little math goes a long way

More important than the ulitmate rider sag is the free sag vs. rider sag.. it helps determine the way the spring is acting based on the weight of the bike alone and the rider; especially with the rear.

Good info, thanks.

Any others out there mind sharing?

 

[tye1138]

One thing about sag to remember, numbers are just numbers...



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[Bella749]

One thing about sag to remember, numbers are just numbers...

Well, they're more than just numbers. The sag establishes the dynamic geometry of the chassis. Also helps confirm proper spring rates for a bike/rider combo. On my base 749 a 2mm change in rear sag made a world of difference in keeping the bike from running wide on corner exit. Right now, I'm trying to get the bike "in the ball park", so all I have to do is make minimal adjustments trackside. I'm very limited on how much track time I can get nowadays, so any info is helpful. I'm trying to crack the code on a mis-matched shock/link combo based on theory. Not the best way, but it's a way nonetheless

The forks are relatively easy. The .95 springs are just a bit too stiff, but I'm gonna see if I can make them work. Most definitely feels better than Biposto Showas with 1.0kg springs.

 

[tye1138]

What I mean is, just because someone says 30mm is the proper sag, doesn't mean it is.

Preload is the only way to really effect sag. But as you get quicker, you'll make preload changes to compensate for track conditions. So sure, you can start at 30mm, its a good base, but in reality, you'll be altering it.



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[Ducshop]

When setting the "R"s up have found the 120 stock spring too stiff for the weights you guys are, even with it's link ratio, I would say a 95 or 100 is more in order. I have Doug Chandlers set up sheet when he raced one in AMA and he ran a 100 or 105, I have his shock valving spec sheet too which seams to work for a lot of riders we work with, with only a small change.

 

[boostedt0y]

Offset: 30mm
Rake: 23.5
Front ride height: forks flush with the triple clamp
Swing arm length: 505mm
Ride height: 245mm (measured eye to eye)
Front sag: 35 mm
Rear sag: 30 mm

I am running 17in Marchesini mags with Pirellis Supercorsas. I weigh 170lbs without gear and the stock fork springs work great for me. I brought the forks over to Dan Kyle in Monterey and he revalved them with his superbike valve kit. My bike also has an aftermarket Ohlins unit on there, but I haven't bothered looking at the model number. The spring has also been swapped out. I'll try to take a peak when I get home.

 

[Bella749]

When setting the "R"s up have found the 120 stock spring too stiff for the weights you guys are, even with it's link ratio, I would say a 95 or 100 is more in order. I have Doug Chandlers set up sheet when he raced one in AMA and he ran a 100 or 105, I have his shock valving spec sheet too which seams to work for a lot of riders we work with, with only a small change.

That shock weight sounds more realistic to me. Was Chandler running the long or short stroke shock? This seems to be the biggest are of concern for me right now.

I must either (A) ensure I'm getting the proper valving to work with the longer travel shock and flat-rate link, or (B) just get a progressive rate link and run my DU301 with a -20/21 spring.

Option A would be ideal if the setup works better than option B.

Option B is a safe bet; it's definitely more affordable, and I have experience with that setup.

 

[tye1138]

When setting the "R"s up have found the 120 stock spring too stiff for the weights you guys are, even with it's link ratio, I would say a 95 or 100 is more in order. I have Doug Chandlers set up sheet when he raced one in AMA and he ran a 100 or 105, I have his shock valving spec sheet too which seams to work for a lot of riders we work with, with only a small change.

Its stiff if you run the wheel base stock, but once you extend it a bit, the stiffness goes away pretty quick, at least for me thats been the case. Last time I asked my local suspension tuner, he kinda wanted it to be a bit stiffer!



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[Bella749]

Last time I asked my local suspension tuner, he kinda wanted it to be a bit stiffer!

I'm gonna leave that one alone

 

[trussdude]

I have Doug Chandlers set up sheet when he raced one in AMA

I think I would be more inclined to us Tye's setup than some oldtimer that doesn't race any more.

 

[slapnuts]

I think I would be more inclined to us Tye's setup than some oldtimer that doesn't race any more.

I'd be more inclined to listen to Mark at Ducshop, than Tye.

Any others out there mind sharing?

I'm by no means a small guy and I run a 100 rear spring, with the shock set up/valved by Mark. I switched from the progressive to the linear link this season. We dropped it in and sag was spot on. It took some significant set up changes and I'm still working on rear traction at one track in particular. I'm not convinced one link is better than the other yet, for me its really down to preference. There are some tracks where I think I prefer the prog. link, but I'd have to run them back to back with two shocks to be sure. We've got a very fast guy (VERY VERY fast) running a 999R with the stock progressive linkage.

On the front, I would think .90's would work for a guy weighing 150lbs ish with the stock valving. The SBK valves def. help over the bumps for me, but the biggest change was going to .95's to get the sag right and more adj. in preload (rather than being cranked all the way in), which Dan Kyle did.

One thing is for sure you learn a lot by changing your setup and starting over - more than just being able to say "it runs on rails". As an example, I like a bike with "faster" rebound, front and rear, and I ride better with a setup on the "stiffer" side. Sag specific numbers vary from track to track and runs in a range (for me 30-35 rear, 35-40 front) - they are really down to preference and what the bike is doing (right or wrong). I would make one change at a time, so you can feel the difference. It takes longer, but I think it helps you learn more as a rider.

 

[KiwiEd]

" I'm by no means a small guy and I run a 100 rear spring "

Good to know that somebody racing these is on the same page as me . I'm certaintly not a midget either .... but neither am I a fat man, just bigger than your average racer.
But that doesn't stop me doing and loving the sport.

These are great posts and I'm relishing the info and opinions being sounded.

 

[JDuc]

Thought I'd chime in as well. I'm enjoying reading the thread. Already subscribed to the thread when it was still just one page...just wanted to show my appreciation. Keep it going! Only wish I had something more valuable to add...but I don't at this point.:think: