Greetings, I have few questions for track junkies and those with suspension experience.

Whenever I'm at the track, it feels like the back of the bike is lower then the front. When I get on the throttle during corner exit, back side sags even more, front gets really light and handle bars start to vibrate. I feel like I have to hold on for dear life just to stay on the seat. It's very confidence robbing.

As far as suspension maintenance, I don't think anything was done. I purchased the bike 2 years ago with 2300 mi on the odometer so I'm fairly certain nothing was changed. Fork oil had most likely broken down and does very little (bike has 7K miles now). Front is very soft and suspension travel is substantial which I'm not happy about at all. I had sag set and baseline done at the track but that was middle of last year. Basically track side provider closed all the valves to stiffen it up a little, and while it helped, problem still exists and appears to get worse with time.

I have Penske shock on the way and I hope that I'll be able to at least lessen the effects of above-described issues. It is sprung for my weight so maybe that alone will help with the back side issue. With height adjustment, I should be able to raise the rear if stiffer spring alone does not do the trick. I will consider more drastic measures, such as lowering the triple, if all else fails.

All of that will still leave me with significant fork travel. I guess my questions are: Is my logic correct? Would you advise against swapping just the shock without touching the forks? How will this affect suspension geometry? Can I get away with just swapping fork oil to heavier weight or should I bite the bullet and get them rebuilt now? How should I proceed with that? Just springs? Springs and valves? Springs, valves, cartridges? What gains can I expect from each?

I realize I just asked a lot of questions and it's hard to diagnose mechanical problems on a forum but I'm hoping that with such large F4 community someone had to run into something similar and can offer advice.

Sorry for the long post and thank you in advance.

 

Of course the easiest is to pull the forks and send them to someone for the works. At the opposite end of the spectrum, assuming the front spring rates are within reason and the sag is OK (about 30% travel with you on the bike?) you can fool with some slightly thicker oil and see how it helps. My Blackbird was too softly damped in the front and I thought about gold valves, but just as an experiment I sucked 100ml of the oil out and replaced it with 10W, which was about 30% thicker if I recall correctly. Made a huge difference, I never bothered doing anything else.
My fear for you is that you'll jack the back up a bit and then the front will be overloaded when braking - thicker oil may not be enough. Worth a try though.

 

I'm 200lbs, and the first time I took my F4i to the track with stock suspension I knew I had to change things. I was bottoming out everywhere, you could even see it in my pictures.

I had the shock rebuilt, re-sprung and re-valved by Racetech. To save some money, I changed the fork springs myself and used stock 5wt. oil. Its a pretty good set up for not a lot of money. I have to run the rebound dampening all the way in on the forks though.

I'm happy with it now, much much better on the track. My next step is to re-valve the forks.

I think you will be much happier if you do something to the forks when you put your shock in.

 

OK, you asked for it (in another thread)!! FWIW, here's what I would do factoring in cost/age of bike/rider experience...

1) you've got a great shock on the way. If you got it used, I hope that you bought the *right* one for the bike of course (I can never tell with Penskes cuz they don't have specific PNs stamped on the head).
- set the shock length to the same as stock
- install shock
- turn the rebound and compression to full soft
- Use the preload adjuster to set the rear sag to 10mm free and 25 to 30mm rider (this will be one P/L adjustment that will give you those numbers if the spring is correct)
- turn the rebound and compression to the middle of their ranges.
- make valving adjustments as needed after riding

2) Forks - if you weigh even slightly more than Danny Pedrosa, then you will at least need springs.
- Springs: If you bought the shock new, check with the shop for their recommended spring rate for your weight (to match their rear rate choice). If you bought it used, do some research to find the spring rate and then look on traxxion.com or racetech.com (AND CALL THEM!) or some such to get an idea.
- Valves: I WOULD consider REBOUND valves for the forks. I would NOT spend the money on full-on cartridges for that bike. Save your money and get seat time on the track or your favorite back road. You might consider either traxxion REBOUND valves or Race-Tech gold REBOUND valves for the forks. I wouldn't bother with the compression side. Get the whole set up from the valve proprietor (air gap, oil brand/weight, spring rate, sag numbers, new seals, bushings, etc.)

Then go out and ride the wheels off that F4 and enjoy that super compliant and relatively low dollar suspension on one of the most neutral handling greatest street/track bikes ever made!! - VE

 

Pardon late reply but I wanted to make sure I had something useful to add. Penske triple arrived this week and I just installed it couple hours ago. First thing I noticed was that I had to raise the rear about an inch to even install the little sucker. If you look at pic 1 you can see that ride height is at its lowest settings - I still have 12mm of adjustment. Now there is no doubt in my mind that my rear was too low and that caused slow turn in, front wheel to unload, and handle bars to vibrate on corner exit. Second thing I immediately noticed was how much firmer rear was when I set on the bike. It sagged and rebounded a lot less. Shock was actually absorbing (imagine that) downward force versus just applying Newtons third law. Stock 150 lbs spring for a guy that's 6'3" 190 lbs (w/o gear) is a bad joke.

I went for a quick ride around the block street figher style (got a few WTF looks ) and noticed that rear was firm but now front felt even worse as it had plenty of fork travel. It just felf weird, still rear / soft front. All of that was expected but unfortunately I won't have any better idea of how the ride was affected until my next track day.

@skapan
Thanks for sharing your experiences and advice. I think you're right, thicker oil may not be enough now that rear is higher and more force is exerted on the front wheel. Even with stock ride height I was bottoming out during hard braking.

@JimT
I know what you mean about bottoming out. I've done around 8 track days on all the valves closed and I'm bottoming out again. It's so confidence robbing that I vouched not to do another track day until I sort this out. I'm going to replace the springs and start with stock oil. If it's still too soft I will attempt to compensate with different oil weight as suggested by skapan.

@VitaminE
I was hoping you would chime in - appreciate it.
1) I could not set the shock length to same as stock. You see in the pic 1 that ride height is not raised at all on the Penske. I think my stock shock was low on nitrogen and rear sagged more then it should or my fat *** caused permanent damage to it . Thank you for the settings advice. I'm a complete noob when it comes to this and I bought the shock from a guy who's only 7 lbs lighter so I'm just going to leave his settings and hope for the best. Once I have track-side vendor set my sag and baseline maybe they can educate me on how to set this thing up. I wrote down your advice in the owners manual and will certainly apply it once I'm more comfortable.
2) Yep, springs will be replaced. I bought it used so I'll be calling Traxxion and RaceTech tomorrow. Looking at their spring rate calculator (http://old.racetech.com/evalving/Spr...ork&bikeid=190) I should go with 0.955 kg/mm. I'll hold off with valves as I don't think my pace warrants it but thanks for the advice. I jot it down in my notes for future reference.

QFT! Amen brother.

Can you guys let me know if I installed it correctly? If you look at pic 2 you can see top eyelet points to the left, while bottom one (pic 3) points right. I could not adjust it by rotating entire shock so that they're inline. I doubt it will cause any damage but would like confirmation and advice on how to adjust this. Did I mention I'm a complete noob when it comes to suspension?

Thanks!

Pic 1


Pic 2


Pic 3

 

with all that good advice I have one more piece you will always have that squat in the rear when getting on the juice, you will want to put on a 7 hundred lb spring to keep the squat form happening there is nothing worse than having lots of power being roobed from the bike squatting when you are in a hurry to get out of a corner, now it may not sound right but that is what we use on our aprilias and suzukis at the track and our riders are about 150 lbs to 170 with leathers on and it works so get a stiff *** spring and a penske shock set the front up with race tech gold valves and fiddle with the oil levels more so than the thickness if the oil is too thick it can damge the shims in the valves so be carefull messing with the fork oil weights, you will have better luck messin witht the levels!!!! it is tried and proven!!!

 

it will be fine they have great swivels you should have no problems at all there but i am telling you you will need a stiffer spring on the back

 

Be super smooth on the brakes. You WILL bottom out the OEM F4i springs. This is no surprise. They run about .78 kg/mm if memory serves....


Could not get the Penske to match the OEM shock length???!!! Its your bike (and your collarbones) but I recommend to you VERY STRONGLY that you call Penske and make certain that the shock you have is the *correct* one for the F4i. I would have to hear it from them myself that it is. I doubt it that much!!! The previous owner may well have *used* it on an F4i but that doesn't mean its the right one.

Penske's are hard to ID as they do not stamp bike specific PNs onto the shock head. You'll need to pull the shock from the bike and give them the measurements that they ask for to "roughly" ID it. I say roughly because even with all that, the valve body can't be ID'd from the outside.

I'm saying this to you because I'm truly concerned that with a 1" increase in shock length, the bike may be unsafe or borderline unsafe to ride at high speed. Alot of these "rule of thumb" numbers depend on the linkage - I realize that. But IMO 1" at the shock seriously affects the bike geometry. Remember what I said about "neutral handling" in the previous post - you can throw that out the window with that kind of rear ride height increase!!

Personal Experience: The linkage on the F3 and the F4/i is pretty similar. I had a 98 F3 back in the day that I bought with an Ohlins (correct for the bike!) that had been raised I'm thinking like 14 threads from baseline. I believe it was about 1/2 inch at the shock. The rear traction on that bike was severely compromised until I lowered it back to OEM spec and then raised it a couple of threads at a time (ending at 4 threads out). The bike DEFINITELY TURNED IN FAST at +14 threads but who cares when you high side the thing 2 times in one season??

Bottom line - Penske is a top shelf company and I cannot conceive of a world where they build a shock for the bike that raises the SHOCK height (never mind the overall ride height) 1" MINIMUM. On the correct shock for the F4i, they would have at least offered the OEM geometry within the adjustable range. VERIFY THE LENGTHS OF THE OEM SHOCK AND THE PENSKE AND CALL THEM BEFORE RIDING PLEASE!!!

Install is fine. Some Penske's have heim joints which do allow the shock to rotate somewhat like you're showing. - VE

 

Just to clarify, by shock length you mean distance from eyelet to eyelet? If so then no. I meant that ride height was raised by roughly an inch looking at the subframe middle point. Shock size/length seemed the same when I placed the 2 side-by-side. I did not measure them, and in hind side I should have. After taking stocker out and trying to run lower bolt through, it would not slide in easily. I would say that when looking through the hole on the mounting bracket, Penske eyelet was "sticking out" ~1.2mm and I had to raise the rear in order to compensate and slide in the bold. Again, I'm eyeballing here but it seemed that looking at the subframe just above the rear axle, it did raise some. Maybe less then an inch, it was not substantial, but did occur. Am I making any sense? My apologies, I should have been more clear in the post.
Knowing that the 1" raise I spoke about was in ride height and not shock length do you still think it's dangerous?
I contacted the seller and he sent me high res pics of the shock installed on his F4i, however, as you stated, that doesn't mean it's the right shock and I highly value structural integrity of my bones so I'll pull it out, measure, compare to stocker and call Penske to verify.

Once again, thank you for sharing your experiences and advice.

 

Great advice, thanks!

To be clear, you're saying that your 150 to 170 lbs riders use 700 lbs springs? I looked up my spring and assuming that sprung weight seller mentioned is accurate it would put it at 650 lbs. Not enough?

I did have couple guys recommend playing with oil level vs weight but how would I know how little is too little?