CrankenFine

Out riding today and a couple times when turning into driveways with a high lip I bottomed the front suspension hard enough to hear it clunk. So tonight looking at Racetech's chart for my weight it lists several spring rates, .90 being closest to their ideal recommened .898 spring rate for me. I weigh about 180 lbs, does this sound right?

In addition to changing the springs I was thinking about changing to fresh fork oil. Racetech recommends 140 mm of 15 wt which they say requires 2 liters. The shop manual calls for 130 mm of "Pro Honda Suspension fluid SS-8" whatever that is, and it looks like exactly 1 liter would be enough. Can I trust their recommended setup and quantities? I don't ride super agressive, but reasonably fast on roads I know.

I think I am also headed for a new JD shock, though not until after I do MCCTs and this front fork. We have short, sharp tree root bumps all over the place and even crusing straight up, the back end occasionally bounces me up a couple inches. I have messed with all the rear shock settings, it's apparently junk. I know the seat hardness makes this problem worse but that's another project...

8541Hawk

Yes the springs sound about right unless you are a hard braker them you might want to go up .05 on the spring rate.

Yes you should change the fork oil at the very least. Ideally you would re-valve the forks for the new spring rate.

SS-8 is 10wt and the oil height listed in the manual is just a starting point from which you tune from.

smokinjoe73

Take a look at sonic springs if you want to save some money on the deal. I use both (in diff bikes) and they seem equal. Until you do the spring change you can just raise the oil level maybe 3/4 inch to stop the bottoming.

CrankenFine

Thanks, for both of those tips.

I am a hard braker, it's a carryover habit from bicycling and needing to stop fast on 25mm tires.

I know the valving needs to be done eventually, I was hoping springs would at least cure the bottoming problem which seems potentially dangerous and destructive to me. If this change isn't noticeably better, I'll proceed in that direction, so I may be in touch with you again.

Also thanks for the fork oil explanation.

CrankenFine

Thanks for that info, I will check out Sonic too. The oil level adjustment is clever. I will probably do that first, since its quick to try. Worst case I could siphon some back out. Time to fire up the area/volume calculator.

D VTR RIDER

The only way of fixing the stock front end, short of changing out to upside down forks, is to install Race Tech spring or equivalent and gold valves. The transformation will be huge.

JamieDaugherty

I'd suggest 0.90kg/mm springs for your weight. On the street you can't brake hard enough to make a difference, so don't adjust the rate for that.

As for fluid, the SS stuff is what comes in the forks from the factory and is known to be partly to mostly crappy. You should run Honda Pro Oils 5wt - that's the best stuff. As already suggested, revalving the forks is the really the best thing. Don't try to run higher weight to adjust for the stock valving as that just makes things worse and takes you in the opposite direction you want to go. Run the HP 5w and correct springs until you have the scratch to get your valving setup correctly.

I always set VTR forks with a fluid height of 120mm, in case that helps. Good luck!

CrankenFine

Jamie, thanks a bunch.

nath981

If you don't have the money to do the USD conversion, or at least the gold valves, then you might want to do what the below link describes.

VTR1000F FireStorm Suspension Mods!!

I used this method to do my forks with 7.5 weight oil and racetech springs a few years ago. If I recall correctly, you need to cut the spacers for on top of the springs and after you get them back together and on the bike, and before adding oil and with no caps on, compress the forks completely to determine the bottom out point and note this for when you adjust the sag and preload. I have plastic ties on the fork legs to help measure and note suspension travel.

This set up works well with the OEM unsprung weight components, but works even better with lighter unsprung components like rotors, wheels and tires like Power Pures. Much smoother ride, esp noticeable over rough roads.

CrankenFine

Thanks for the detailed method description. What is the USD conversion?

Part of my reason for not going whole hog on the forks right now is that we just finally got some riding weather after endless weeks of rain and cold, so I don't want to dissassemble my front end and send the forks away now to a suspension specialist for a complete fix. Of course, the same aforementioned bad weather prevented me from becoming acquainted with my ride enough to even realize how much the fork needed attention prior to now - otherwise I could have dealt with this more timely during all that rain. Murphy's law...

smokinjoe73

USD is upside down forks. You can swap forks most easily from another honda (rc51, CBR1000RR, etc). This is definitely a costlier route & somewhat more involved. You can do the fork oil without missing riding time, same with springs. Gold valves are a little more labor intensive that the first two but you will notice a huge diff with just the first 2.

CrankenFine

10-4 all that. Just ordered springs. First rainy day after they arrive, I am swapping out the old ones. I'll have to invite a couple buds over to perform the sag work.

Tormoz

I'm curious, did you ever get this done and if so, how were the results? I weigh about 190 lbs and I too am experiencing my forks bottoming over some sharper bumps, but AFAIK, they're not really sharp enough that I ought to be bottoming.

8541Hawk

Well if the spring rate is correct and you have the proper sag and you still have bottoming issues you need to raise the oil level in the forks.

Tormoz

I'm 90% sure they are the stock fork springs (the previous owner didn't mention anything about swapping them out), and the bike has 30,000 miles, so I suspect some new springs would help.

JamieDaugherty

My guess is that your forks aren't bottoming at all - you are feeling the harshness of the stock valving. Basically the stock pistons are so restrictive that you can't push the fluid through them fast enough. It's like a hydraulic lock, the forks are actually not moving, which is why you think they are bottoming. Technically speaking this is called excessive high speed damping. Springs and oil height won't really help with that, you need a revalve to make the forks work well.

Tormoz

That's possible, but I'm pretty sure they're bottoming, because I am aware of the feeling of the forks traveling quite a bit before hearing and feeling kind of a clunk.

One way to be sure, though: I'll put a cable tie around the fork tube and see how far up it gets pushed; the bump where I experience what I think is bottoming isn't far from my house.

nath981

and that would be a couple inches below the lower triple, i.e., not to the triple.

Tormoz

I'll post my results when I check it. Kind of a noobie question, but I imagine setting the stock preload setting to a harder (clockwise) setting wouldn't help much, or would it?

JamieDaugherty

To be even MORE specific, the forks have 120mm of travel. I'd measure the actual travel used and not the distance to the triples.

No, the stock fork springs are a very low rate so adjusting the preload doesn't effect it that much. Let us know what you find out.

CrankenFine

Sorry i have not visited my own thread in a long time. After I got my suspension straightened out I forgot to post. I did change the front to a pair of Sonic .90 springs. This definitely did stop the bottoming and like you I heard a very noticeable "clunk" along with a shock thru the bars on certain bumps. My bike had only about 4K miles on it at the time.

I think I erred a tad too low on the spring rate for my style of riding as the fork dips noticeably whenever I apply my front brake, so I'll switch to Racetech .95 springs over the winter. (and let JD work his magic on my front fork valving)

But between the new springs up front and the JD rebuilt shock in the back, it's a much more pleasant bike to ride altogether.

Tormoz

Thanks for the update. Is changing out the springs, oil, etc. a big job for a someone with reasonable skills and the manual? Just trying to get a sense of how much time I should allow.

Old Yeller

the dipping will be helped a lot with the valves. I run a .90 and 12 ounces of 7wt in mine. Even with intermediate track use the dipping is not a problem at all.

CrankenFine

I did the front springs in about an hour and I did everything from on top.
I supported the bike rear on a workstand and the front from underneath with a hydraulic jack and a piece of lumber. I then pulled only one side at a time leaving the other spring assembly intact to help hold the bike up. I made the new spacers the same length as the stock ones minus the difference in spring length. (the new springs are longer than stock).

I followed the manual regarding getting the preload adjusters out of the top tube retaining nuts. I did not change oil or adjust oil height. Note: The damper rods may fall into the tube under their own weight if not supported while working, but reaching down inside the tube with a piece of bent wire pulls them right back up.

Tormoz

Thanks for the info -- sounds like a nice way to replace the springs if, as you said, you're not doing the fork oil as well. I'm planning on changing the fork oil at the same time, so I'll probably take the longer route of removing the forks.

On another note, I did check to see if my forks were bottoming on a couple bumps (by wrapping a plastic tie-down around one fork tube). Yup, bottoming. For the time being I cranked up my preload a bit which doesn't prevent the bottoming but does make the front end feel better.

WAYNEHAMMER

Sorry guys. I know this is an old thread, but I'm gonna change my fork seals tomorrow. I have racetech springs and gold valves. What do you mean by oil height/air height? Do I measure from the top of the tube till I hit oil and that is my measurement?

CrankenFine

Yes but it's assumed each leg is off the bike so you can hold it plumb and the tube is fully compressed. ( sorry if I'm telling you something you already know)
In this condition you can accurately measure height from top. Stock figure is 130mm or 5.1 inches from the top. Ask Jamie Daugherty for modified amount suggestions for your application. There's a link to a pdf of the factory manual in the Knowledgebase section. You want Section 13, page 18 if you need any additional info.

smokinjoe73

Will you notice the subtle nuances in damping landing the front end from stunting? Might be a waste....Maybe put the dinero towards a jacket.

CrankenFine

That's pretty funny. I didn't even notice Wayne's avatar.

WAYNEHAMMER

I don't ride like that anymore. Too hard on my bike. Plus I have a family now. Can't be getting hurt. Thank you