954 Front End Issues
 

Over the winter I changed out the front end to a 954 set up with new Race Tech spring and gold valve. If I get a chance, I will post pics with all the mods (track only bike now).
I recently took it to the track. It turned in very nicely and stopped like crazy with the 330mm front discs. The problem I had was the front bars shacking back and forth on 2 left hand off camber corners that drop off quickly (4th gear). It would also do the same coming over one of the rises on the straight away (6th gear). I tried moving my weight forward, giving it more gas, being light on the bars but once the oscillation started, it persisted for a while. It would be real stable on other left hand corners that were flat or were the front end was compressed more. This never occurred with stock fork. The only difference besides the front for change was going to Michelin Power Ones.
The Power Ones lasted 3 days and still have 1 more day left on them. They were the bullocks. I had slipstone on for 2-3 years and they would be trashed in 2 days. I don't want to trash the Bridgestone because this may have been caused by other factors that I won't go into now.
I set up the front using the exact geometry as the stock set up i.e. forks dropped 10mm and 5mm spacer on the rear. Yes I measured the distance to the axle prior to dis-assembly and set it the same disctance. I'm of the belief that this may be a geometry or suspension issue so any comments would be welcome.

Well I never nailed down what exact measurements I had before my swap, but I did end up having to raise the forks some in the end to get the handling right.

I haven't had any oscillation / shaking with my setup, even when I had the forks too low (ride height too high) and while I did add a damper, I did so just because I got it cheap off ebay.

If your springs are significantly higher rate, you may be riding higher than you think. Did you get them sprung for your weight on the VTR or the 954? (I bet they are different calculations on their formula)

Both set ups were re-sprung with the correct springs for my weight and sag set the same i.e. 30mm. So from a geometry point of view, they should be identical. The VTR forks with RT springs and gold valves worked real well compared to stock; that is until the 954 conversion. It works that much better. It tracked exactly were it was pointed and turning in was very easy. I just need to correct the intermittent handling issues and then concentrate on using less brakes and more throttle :lol:

I recall reading that 954 forks were shorter than the VTR's stock unit (whereas the RC51 forks are the same length). This shortness could be altering your geometry and weight distribution. Just a thought.....

When you measured to the front axle, did you take into account the 954 forks have top out springs?

If not you might have some trail issues.

I measured the stock fork from the bottom of the yoke to the center line of the wheel fully extended then set up the 954 the same. Geometry should be the same. I did not take into account the top up spring. If it changes the geometry, then that could be the cause. I would have to lower the rear to compensate since the forks are flush with the top of the triple.

If you didn't fully extend the fork, then your numbers are not correct.

In fact you have the forks pulled down to low as compared to stock.

To get the proper numbers (if you have a front end stand that lifts from the steering stem) remove the front wheel and then reinstall the axle.

Then have someone put their foot on the axle and push down. When the forks are fully extended, then take a measurement and re-set the forks to get the same fully extended measurement as you had with the stock forks.

Once you have done this, then you can start dialing things in to your liking. ;)

dont forget the vtr fork sticks out of the top yoke for the handlebar !!

ive a 1000rr front end on , it needs a damper now 100 percent ,

the symptoms you describe are geometry difference by the sounds of it alright
,
i feel from my bike it needs to drop lower to get it to turn in but im reluctent to drop the bike on the legs further because its already unstable ,

ive to do some riding to figure out where i need to go from here ,

but id recommend getting a damper on ,

just get a superhawk damper and whatever clamp size you need for the leg (50mm?)

tankslappers aint good :shock: ;)

Does anyone know if a Scotts damper will work with a CBR1000 top triple on our bike? I'm not sure how they attach, but from the website it looks like maybe it would still work?

I'd also be interested in other brands that will work with a CBR1000rr front on a superhawk without too much modding. Not sure what direction to go with this. (edit: didn't see the last post, so that answers this question, but still wondering about the Scotts damper).

I have a CBR1000rr front end on mine now, and it does get a bit twitchy sometimes without a damper . . .

You do not automatically need a damper just because you are using CBR 1000RR forks... I have no need for a damper with mine...

I'm probably adding one just the same, since I got one dirt cheap, but I really don't need it...

If you "need" a damper, you have the geometry wrong... And it's fixable without one...

The Scotts damper is mounted by a clamp that affixes to a replacement nut on the top triple... The nut is the same size and thread for the 929RR/954RR CBR's and the Superhawk, and I'm fairly sure it also applies to the 1000RR so the important part is the part that mounts to the tank bolts...

So basically, if you can verify that the size and thread of that nut is the same, just go ahead and order the mounting kit for the Superhawk, and it will fit just fine...

It looks like the CBR1000RR top triple is missing the little groove that the damper mount's "machined register" fits into. So I'd have to make the groove myself, which shouldn't be very difficult I guess. I'd probably also have to grind off the stock CBR1000RR damper mounts in order for it to fit flush. I think I'll call them and see if they've ever tried this. They don't make a CBR1000RR damper.

And I agree that you don't "need" a damper with 1000RR forks, as I've yet to encounter true steering shake with this setup, but I'd like to be able to add a little more resistance to steering inputs. It just feels a little more "loose" than I want it. I might also try tightening the steering head nut a little bit and see if that helps any. Right now it's torqued to the middle of spec, so I think I could go a little tighter, especially with All Balls bearings.

Right, I forgot about the ugly mounting holes... Wouldn't it be possible to use them? just make a custom bracket that bolts to the triple and then bolt the damper to that? If you want the measurements on the holes, let me know and I'll attack the damper/bracket with the calipers...

I e-mailed Scotts to see if they have a solution. On their forum, they said they were never able to "defeat" the HESD, so never made a damper for the CBR1000rr. But that doesn't make sense to me. GPR has an aftermarket damper for the CBR1000rr . . . maybe I'll try to make that one work.

And it should be possible to fabricate a mount that would fit, and probably pretty easy for someone with the right fab equipment, but I think it would be easier to grind off the mounting holes on the triple clamp, and then fit a superhawk mount to it. Especially since all I have to work with right now is a dremel.

I've also thought about trying to make the HESD work on the superhawk. They are very cheap on eBay, but I wouldn't know where to start . . . and they're ugly.

Well... I have a more or less well stacked machineshop... ;) And my gut instinct is still to grind and use the Superhawk mounting...

I'd probably stay away from a CBR 1000RR specific mount regardless of the make... That one will most definetly have a standing part at the tank with the boltholes in the wrong places...

The HESD is a no-go on a Superhawk... It needs a trigger signal from the gauges/ECU to switch resistance based on roadspeed... So unless you figure that out, it's not going to give you any resistance at all... (you could just wire in a switch though)

I agree that probably I should need a damper. It is either a geometry or a dampening issue. I've been listening to some of the Dave Moss's videos and in one segment he mentions the very same issue of front end wobble in off camber down hill turns and the cause being a rebound issue. So before going the dampener route, I will try removing some rebound. I set the rebound based on past experience but I could very well have too much.
The Michelin tire rep looked at the tires and suggested that I drop the front or raise the back since I wasn't using the front tire as much as the rear.
I have no stability issues braking or during any other turn ins, so adding rear height should not cause any problem except to cause an increase in wobble in the same locations on the track. Simple to reverse if it does.
The only way to sort it out is start making adjustments 1 at a time and take notes of all changes. It could turn out to be a combination of things.

I need to find more time and $$ for additional track days. I spent the wad with the front end, tail section, rear sets, front stay, painting, etc. There is a couple of guys on this site that are responsible for me being in this predicament :lol::lol:. I'm not saying I was tricked into it but it's like flashing chrome to an HD rider. However, I've seen many others on this forum with a far worse sickness.:laughing2:

well if you ride on bumpy roads hard you do ;)

the bike is much more unstable and slaps which is not a characteristic of the stable standard geometry

im going to look a the differences between the three i ride and try to calculate ,

the one with the r1 front , with the yokes dropped about 15 mm turns best

the standard one is shit but stable ,

and the 1000rr fronted one feels the best quality damping , but the steering aint quite right yet ,

as i said in my other post it feels like it needs to quicken , but its too unstable to drop any more without a damper

thats my opinion ,

and was trying to help the original poster with the original problem , which was steering stability ,, after a front end change driving hard

You are welcome to come over here and try to school me on hard riding if you like... I'm not promising that I'm going to leave you behind, but I doubt you will be the one leaving me behind either... So I do know what it means to ride a bike hard on a bad surface... And I still don't need a damper...

I would in some instances prefer to have one for the ability to adjust it to give me a bit of resistance for my prefernce of riding style, but I don't need it...

The point is, neither should you need it, or the OP, since adding a damper to fix a geometry problem only masks it, and when the time comes when the damper can't compensate enough, it hurts a lot more than if you didn't have the damper, allowing you to push the bike to a point where you really get hurt...

D VTR RIDER has the rigth idea I think...

Dropping the front changes geometry in one way, raising the rear in another, even if it seems similar, it's completely different and can have dramaticly different results... Try that in small steps before you give in and slap a damper on there...

i didnt mention your ability it doesent interest me , the op had a q about unstable steering over bumps ,

thats what steering dampers are for ,( im not a fan, as a rule i dont like em) , but ..
the sportier the geometry , which is also affected by trail !
you can induce a tankslapper particularly while riding hard over uneven surfaces , its not always possible to correct one, as of course you would know , right? (no matter what your ability :rolleyes:

no he might not need one , i never said he did ,

but its a simple , real , actual , possible solution to the problem

you do know the 1000rr comes with a damper right ?,

btw there not many racebikes round this way with no dampers fitted :D

anyway i stand by my original, intended to help , having worked through similar problems on my own bikes post

:D:D

Man this is getting a bit heated.....

I argee with Tweety though in the fact that you shouldn't need a damper. Mine is set up fairly aggressively and really doesn't need one.

Back to the OP, I still believe that the measurements are off on his set up.
By forgetting about the top out springs, he has ended up with too much trail and is causing some strange things to happen.

So IMHO the first step is to remeasure the front and set it to the stock trail numbers and then go from there.

Right here point to exactly what I've been saying...... Though don't just start changing things willy nilly..... Adding height also changes the braking characteristics and how the bike transitions from side to side.

Remeasure the front end with the top out springs extended and after re setting it you might be supprised how the bike works.

I think 8541Hawk is on the right track - as usual.

The front height measurement should be made from the axle to the bottom of the frame head, not to the triple clamp - there are too many variables, with that measurement.

The 954 fork has a long topout spring, which interferes with the top of the fork travel, so you end up with less travel and need to set it up with less sag. With 30 mm of sag, your front end is probably low, compared to the stock setup. This decreases the fork rake and shortens the trail. The 954 triple clamp will have less offset than the stock clamp, which gets some of the trail back. But it sounds like you have too little trail, which is causing the front end to be unstable when it is lightly loaded - your described instability is when the front end is light - which is where it typically occurs.

I would recommend shortening the topout spring to free up the top of travel, especially since the fork is probably shorter than stock anyway, but it's a substantial project. Start with increasing the preload to decrease the sag and raise the front. RaceTech sells shortened topout springs for the RC51-SP2, for that reason. They probably have some for the 954 forks - they might even be the same spring.

That doesn't sound right, there should be 10-11mm of the fork above the triple, or at least I needed that much to get it to handle right.

Here is a picture of mine from when I added the GPR, but I really didn't need it:

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