front suspension travel and proper setting?

[shrike]

Since I had my 2005 Bandit 1200 I think the suspension is bad. I am not trying to bash the bike, I think the suspension is not properly set. First I found the front suspension was too soft. There was some play in the suspension and it was fixed by the dealer (bad bushings apparently). While they were at it I told them to put progressive springs. I think it's the ones made by Progressive and not Race Tech.
So now I think the suspension is too hard in the front. I weigh about 160 lbs.  The roads are bad around here and the fron of the bike jumps on almost every bump. It also seems to bottom if the bumps are a bit big. I don't think it is normal, I think it does not use all the travel of the front suspension. In a straight line it's not so bad but when I am turning and the road is less than perfect I find the bike gets upset way too easily and I really hate the feeling.
I don't know much about suspension so I am reading a bit and gathering info. I reckon the first step would be to set the sag properly. I will do that with the method described by Race Tech which I found in another post.
Today I also put some tie wraps on the front legs to see what is the travel of the suspension.  The forks are flush with the top of the clamps.  The tie wraps stop at about two inches below the bottom clamps.  I think I reas another post where the user was saying his tie wraps stopped at  inch below the clamps. Can anyone confirm what is the distance where the tie wraps should stop when the suspension REALLY bottoms out?

I need to know if I am using all the travel available or I should take some oil out?
Thanks...

[pmackie]

Hey Shrike

I'll try to help here.

First, for preload, the factory lists the full stoke of the fork at 5.1 inches. Measure this by putting the bike on the centre stand, unloading the front wheel completely, and then measure up the 5.1 and put a felt mark on the tube. Then you can measure down to this mark from the lower clamp to determine full stroke to your zip tie. Static sag should be in the range of 1/3 of stroke, or 1.6" +/-.

It sounds like your forks are not quite right, even with the Progressive Suspension springs. One thing I would be concerned about is whether your shop put the correct amount of fluid in the forks. On my 2G 600 forks, the call for LESS fluid in the forks with the Progressive springs than stock. If the shop did not remove fluid when they put in the springs, this could be part of the problem. Without enough air space, the forks will feel "harsh" on both small and large hits, and will NOT stroke completely.

You need to see if the fork oil level meets Progressive's recommended level. To measure fork oil level, you need to carefully remove the fork caps and springs, slowly compress the forks completely and measure the distance from the top of the fork caps to the level of the oil. Your Progressive Suspension instructions should list the correct level.

The only adjustment options you have are preload, fork oil level and fork oil viscosity, beyond changing springs (which you've already done). These are NOT the best forks in the world, but can be made to work reasonably well. For my setup, I have done the following, I'm 180 lbs and usually do longer tours:

1. Progressive Suspension fork springs.
2. Approx 1" preload (progressive recommends you start with springs flush with top cap. I have changed preload 3x until I got what I wanted - 1" over top of clamps).
3. 80% SAE 10W and 20% SAE 20W fork oil. So a blend to increase viscosity slightly. Firms up compression and rebound slightly, but be carefull, too much oil viscosity will make the forks harsh as well.
4. 1/4" higher fork oil level (slightly MORE oil) than recommended by Progressive. This makes the end for stroke stiffer, without having much effect in the early part of the stroke. Be carefull though, as mentioned above, too much oil will definately have a negative effect.

If I were to do it again, I think I would use Race Tech straight wound springs, although the Progressive DO provide a good compromise for touring.

Beyond these options, the next choice is to rebuild the forks using Race Tech Gold Valves.

I hope this helps...

[shrike]

Thanks for the reply Pmackie.
I had the data for the travel of the front suspension in the manual  but did not know where the 5.1 inches stopped. I did not think of just unloading the front suspension by putting it on the centerstand and then measuring. I hope I get the time tonight to check ithis  out.
Unfortunately I did not get the instructions from Progressive but I will contact them and ask if they can email them to me.
I had just a couple of questions.

So the travel for the rear suspension is given on a vertical axis but for the front suspension it is given along the axis of the forks right? I am talking about the data given in the manual. I will use that data to set the sag.

When you say level of oil to the fork caps, do you mean tot he top of the tubes where the caps sit? Or do you substract from the top of the tubes the thickness of the caps as if they were installed? I am not sure if what I say is clear...
When I set my suspension I will start with your setting for preload but maybe less oil since I would rather have a more comfortable suspension for touring so it absorbs more efficiently the bumps. I am not riding agressively and I know my limits. I just want to bottom out the least possible. 

So your srpings are 1 inch below the top of the clamps and the forks are flush in the clamps?

Thanks.

[shrike]

Out of curiosity I measured the travel on the forks at break time.  I put the bike on the centerstand and asked a fellow worker to push on the rear of the bike.  The forks extended and I measured 130 mm from the top of the dust shields. It came to about 3 mm or 5 mm from the bottom clamps. Is this right? This means if I drop the forks in the clamps they will always hit the clamps?
Am I doing something wrong?

[pmackie]

Good point Shrike

I went and measured my 2G 600, although it may be a little different than your 1200.

My service manual says the fork stroke is 5.1" (130mm), but my zip tie on the forks is only showing movement of 4.25". With my forks dropped 5/8" in the clamps, I have 5.1" (130mm) of space between the body of the dust shield (NOT the top of the extension that protects the tube from rock chips) and the bottom triple tree. I always thought the 1200 had slightly LONGER forks, but maybe I'm wrong. Maybe recheck your measurements to make sure you're not measuring from the top of the "rock shield".

Anyway...my 600, (and most other damper rod forks) have a bottoming cone that takes up approx 1/2" at the end of the stroke. This is designed to dramatically increase the compression damping when the forks "bottom" out. In effect, it takes a REALLY big hit to actually bottom the forks. They will vitually hydraulic lock for the last 1/2", in addition, there is a "top out" spring, that usually takes another 1/4"+, which eliminates "clunking" when the forks extend completly, so this is where the extra travel went.

So the travel for the rear suspension is given on a vertical axis but for the front suspension it is given along the axis of the forks right?

Correct, the 5.1" is the "fork stroke" - including the top out spring and the bottoming cone. You will only see the full stoke by compressing the top out spring and full compressing the fork over the bottoming cone. Actual usable stoke is closer to 4.25-4.5".

When you say level of oil to the fork caps, do you mean tot he top of the tubes where the caps sit?

Oops...yes, I'm talking about the distance from the top of the tubes, with the caps removed, to the oil in the tube, with the springs removed.

So your srpings are 1 inch below the top of the clamps and the forks are flush in the clamps?

Sorry...I wasn't compeletey clear here either. My fork tubes (caps removed) are 5/8" above the level of the top triple clamp. I have my springs approx 3/4" above the top of the tubes, resulting in close to 1-1/2" total preload. BUT, the 2G 600 does NOT have preload adjusters in the fork caps, so your set-up will have to be different. For your bike, definately get the install instructions from Progressive Suspension. But don't be afraid to play with the preload, especially since your bike as adjustable preload built into the fork caps.

I hope this is a little more clear. Good luck and let me know what you find out/decide to try.

[shrike]

First thanks a lot for the effort put into answering my questions. It's really appreciated.
I will for sure post my results when I will be done but it might take a week or maybe more. I don't think I have the time to tinker with it this week end and neither during the week.
I am pretty sure I measured the 130 mm from the dust shield (rubber part with spring around it). I wonder if I should pull on the wheel once it's off the ground before measuring. I also wonder if I did not measure with the wheel on the ground. But it's more clear after your explanations so I have to redo my measurements.

I have the feeling the suspension really does hydraulic lock much too early. I'll keep you posted.

Thanks once again!

[shrike]

well I checked the oil level today. One leg was at 130 mm and the other was 80!!!! I went with the litterature from Progressive suspension's web site which says the distance from top of the legs to the oil level should be at least 140 mm. I put thinner oil also 10W. I hope it won't be too thin. I think before there was 15W weight at least. It was clear there was a viscosity difference. I did not have the time to take the bike for a spin, maybe tonight. The forks seem a bit soft now but the sag is not good either. 30% of 130 mm should be 40 mm. Stock spacers and preload set at maximum gives me somewhere around 46 mm.
I want to put spacers 10-12 mm longer so when the preload is at minimum the sag will be ok for when I am alone so I can adjust if I load the bike with extra luggage or another passenger.
Which brings me to the question. I tried finding PVC tubes at 1.25 inch or 1 5/16 inch outside diameter but I cannot find. In these dimensions I can only find ABS tubing. Can I use ABS tubing for spacers or will it be destroyed by oil?

[pmackie]

Yea...you can use ABS with no problems (at least I haven't had any in the past).

At 80mm oil level, I'm not surprised that the forks were harsh and not stoking completely.

[shrike]

Ok cool, so I'll go for ABS then.
I took the bike to work this morning. Much more comfortable but suspension is a bit soft, it dives more now when braking but I prefer it to how it was before. I will play with the preload and the weight of oil like you did. I'll buy a seringe and take about 75 ml out and replace it with 15 weight oil or 20 weight oil and see what that does
Thanks once again for the input