Bonneville America Forums Forums Technical Forums General Tech Front Forks

Is it me or are the front forks on my 2003 TBA weak. It seems even the smallest bump or grabbing the front braked to hard bottoms them out. What would be the fix for this? New springs? New fluid? Whole new set of forks?

What're you doing, sitting on your handlebars? I've gotten my forks to bottom out, but I've really gotta be trying hard to do it.

Matt

Nah, I’m getting to old for that kind of fancy riding. Seriously though, it really doesn’t take much to feel the front end bottom out.

I replaced my springs with Progressive and the front end dive is greatly reduced.

Drivr,

I would have your dealer check to make sure they have fluid in them at appropriate levels, unless your a really big brute, you should not be able to do that under normal opperating condition. I can't squash mine out.

where's Adey

hey phil
where did you get the front springs from?

I also replaced the front springs, and the dive is not only reduced but virtually eliminated. Better take it easy over big bumps with these springs or your rims will get worn out.

Ryan

Got them from Paul (fryguy)

Go with the Progressive springs ( MAWonline $70) and up the fork oil to 15W. That did it for me, a HUGE difference in handling.

How much of a job is it to replace the springs? Now before the nice weather hits would be a good time to do this sort of thing.

Unscrew the fork caps(being careful by putting your hand over the nut, because they can spring out like a Jack-in-the-box), Take out the old springs using a coat hanger with a little hook bent on the end, and put in the new ones. There's also a spring seat and a spacer on top of the the springs, so watch out for those and remeber which order they go back in)If you aren't close to a required fork oil change(24,000 miles or 4 years), I wouldn't sweat it.

If you want to try the 15w fork oil, then it's more involved. Best to get a shop manual if you don't have one, and you don't feel all that sure of what you're doing. If you're confident, then you'll want to take the forks off, drain the oil into a pan. Measure out 548cc(18.5 oz) of fork oil and pour it in. Then pump the fork a few times to get any trapped air out of the oil. Fully compress the fork, and then let it sit a few minute to stabilize. Use a wooden dowel(found at any good hardware store), and stick it down inside the fork till it dips into the oil. Holding the dowel firmly against the edge of the fork tube, take a Sharpie and mark it at the top of the inner fork tube. Remove the dowel and take a tape measure and measure the distance from the Sharpie mark to where the dowel starts to get wet with oil(like a dipstick on a car). The distance should be 166mm(6 1/2"). It's better to slightly underfill than to overfill as more oil means more pressure in the forks which can blow the fork seals, and you don't want to have to change those out. If you have too much oil in, take a Turkey baster found at any grocery store, and remove a bit of the oil till you get the correct amount.

Then just put your fork springs in with tighter coil windings on top, and the spacer and spring seat(looks like a big washer). Then put the fork top cap screw back on with some steady pressure on it. Be careful here, because if you aren't you can crossthread the top cap. I've found it's easier to do this job with the correct 22mm 6 point socket, than with a wrench(spanner for you english types).

Now that is what I call instructions! I ordered some Progressive springs last night and now can’t wait to get them installed.
You folks have corrupted me, I get a great deal on a bike and now all I want to do is ride and accessorize it.

Thanks for all the responses.
Jason

Put the new springs in today. Now if only it were riding weather...

You will love them. I changed mine last fall and just that change was amazing. For Christmas my wife got me the Progressive Suspension 440 shocks. The weather here has been crud lately too, but a small ride I got in a couple weeks ago told me how great they are as well. Bumps where I normally tried to put a little daylight between the seat and my butt felt almost non-existent.

Sitting here waiting for my igniter box, I thought I'd cut off a 1/2" of the spacers since I'm running a slightly taller Metzeler 880, and the Progressive Springs are a bit longer than stock.

I hope you either did one fork at a time, or put the bike on the jack and raised it some. Because if you don't do that and take off both fork caps at the same time, the bike's front end will sink down. After reading this thread again, I realized I forgot to include that important bit of info.

Hope you get a chance to take the bike for a ride soon with the new springs in. I still think it's the best mod I've done on my bike. That fork dive under braking with the stock springs used to bug the ^&*$ out of me.

yep, one at a time while the bike was on the lift. more so that if I screwed something up the cost to fix would be less. But it was a piece of cake. I just found a shop manual on ebay so I am waiting for that as well. the guy had 2 different Bonneville shop manuals for sale and they both were for the America. I did not know which one covered my 2003 so I bought them both. Will probably offer up the one I dont need on the classifieds on this site.

Derek,

Why is fork oil required to be changed. Does it really break down? I haven't changed mine in 4 years. I do want the progressive springs but I don't want to change the oil.

later
Paul

Which part number on MAWonline?

The part number for the BA is #111145. I got mine here MAW online

If you check out the Progressive Suspension website, they suggest changing for oil every 20,000 miles or every one year. Mine is an '03 and I haven't changed mine either. Most likely the oil collects moisture over time and loses it's viscosity and ability to help rebound the forks. They suggest a 10wt fork oil as a good all purpose oil. Suppose I'll have to do that this summer...

Thanks for answering both questions Throb.

Later,
Paul

Here are my thoughts for anyone who is thinking about changing out your springs.
Raise the bike, I had mine on my lift and strapped down it is a lot easier to work on when it is on that lift.
Remove the handlebars. I could not get the spacers out without doing this and it is easier to get the end caps on and off with a socket than a wrench.
Keep a few rags/towels handy, the springs are in oil so when you take them out they are gonna drip.
When putting the end caps back on (the progressive springs are slightly longer than stock so your going to have to push the cap down) use a socket. that way you can push down and turn and the same time.

It was a very simple job to do and I will let you know how the feel and handle as soon as I can get her out on the road.

Jason

Btw Jason, the shop manuals cover all the new vertical twins. If it's an older one though, it won't have any 865cc specific items or the Thruxton. And thanks for adding those tips.

Quote:

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You might even be able to get this done at the Georgia Rally in May if you're going. Ask Dinqua/Pat or Chy.

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I was thinking of that too

Derek,

So you changed the fluid in your front forks. With no sealed cap in place, the forks compress easily?

One thing to note about the fluid level of 166mm. This is the level when the forks are fully compressed AND vertical. So those that renew the fork oil without removal of the forks, take note. 166mm on an incline is not 166mm when brought to vertical. Someone please take out their protractor and do the algebra. Safe to say that the oil level will be on the safer side of give or take.

A second item to note about the fluid level: The height of 166mm is measured when the springs are NOT in place. Another member was asking if a difference in displacement existed between the stock springs and the replacement springs. Surely, the progressive springs displace more oil than the stokers. Again, as another member suggested, measure the oil level BEFORE removal of the old springs. Then after the new oil is dumped in and allowed to equalize, and then corrected to 166mm on a fully compressed fork, whew, drop in the progressive spring and measure the oil level.

Can someone that has laboratory glass determine the difference in displacement? That would be sweet. I am guessing at least a mm in height.

I’ve got a bicycle stand that has soft jaws. Thinking about using that to hold each fork while I renew the oil.

Thanks for the notes regarding the forks oil/spring issues. Please comment on my notes above as I have yet to expose any oil of a hydraulic nature to Florida air.

The forks compress easily without the caps on. I would advise to check both fork tubes for oil levels before removing the old springs if you're going to the trouble of doing that. I just don't trust the factory that both forks would have the same amount of oil in them. Only takes an extra minute or two to check.

IMO, if you put in the Progressive springs with the tighter windings on top, you shouldn't see an appreciable difference in the oil level. But no harm in doing a thorough job and taking the extra few minutes to measure.

Personally, I can't see changing the oil with the forks on the bike as a great way of doing it. It'll be tough to get all of the oil out of the forks since we don't have a drain plug. Might as well do it the way the book says, but that's just me.

Somebody has already mentioned strapping the bike down to the jack, but I want to re-emphasize that. It's also a good idea to make sure you don't have your jack postioned too far aft when you raise the bike. I've had the whole bike and jack tip backward on me in the past because I had the jack placed too far back. You can even place some short 2x4s, or whatever you have laying around, under the back tire to insure it won't tip backward.

Thanks.

I jacked my bike up high enough to slide my foot stool under the rear tire