Prolink Fork In Early Model Frame & Steering Damper

alimey4u2 · Post by **alimey4u2** » Fri Jul 18, 2008 12:26 pm

cbxtacy wrote:To answer all your questions about how it works

1. It uses the whole stroke of the damper side to side

2. the cooler is not in the airstream so placing a small obstruction in front of it does no real harm

3. It takes very little friction for a damper to be effective, even with the damper on the stiffest setting there is no flex in the bracket

It's ugly, effective, and simple to fabricate. I went to Home Depot and a couple hours later, the damper was working. I used to have it mounted similar to Larry's (you can still see the fork connector still on the forks) but it was too close to the tank and there was too much side to side movement.

Thanks George for the clarification...

cbxtacy · Post by **cbxtacy** » Fri Jul 18, 2008 1:43 pm

I don't like the looks of it though and I'll probably remove the outboard bracket and have something nice looking fabricated. Someday. Larry and Don you don't know how lucky you are. To have days when you don't ride because of the weather. I'll probably re-do the bracket on the first cold/rainy day. Might take years.

cbxtacy · Post by **cbxtacy** » Fri Jul 18, 2008 3:44 pm

my concern with clearances is to not have the damper touch the cooler. When it was mounted similar to Larry's, at full lock it was real close to the tank and if you turned the forks real fast lock to lock it would touch. I'm going to trim up the outer bracket and get the damper closer to the cooler with enough buffer space to where I don't worry. And if it gets just a bit to close, I got an aluminum bar, L shaped, 4' long from Home Depot to re-do it. The bracket on the bottom of the steering stem is steel, from a chunk 1/8"x1"x8' long. To make the precision bends I used big hammer and vise.

Don #6141 · Post by **Don #6141** » Fri Jul 18, 2008 4:12 pm

cbxtacy wrote:Larry and Don you don't know how lucky you are. To have days when you don't ride because of the weather. I'll probably re-do the bracket on the first cold/rainy day. Might take years.

Yeah - I'm about 150 miles farther south latitude than San Diego so I only have to wait 'til about the middle of December. Then I get about a 6 week 'break' where I don't have to mow the grass and I put the hardtop on the convertible. Come the end of January, it's back to mowing and driving topless again. We can still ride all year . . . . but when it does rain in December/January, it gets a bit chilly for riding - Some years we go all winter without a freeze

I want to get the valve cover on the X chromed . . . . but it's either buy a second one, have it done and then swap it out or wait 'til January and do the only one I have which is on the bike

The Red '79 with all the 1100F parts and ProLink forks you posted the pictures of for Dave last month is the Katrina Bike he built for me and I've not seen any need for a steering dampener on it so far - Between Dave and I, we've put about 1,000 miles on it since he got it finished. I had a box stock silver '79 before the storm and the difference in handing between that bike and the red one I have now is almost night and day . . . . I would never have guessed that the forks, wheels, swingarm and shocks could make such a difference and yet have a basically 'stock' looking bike - Mine feels as safe and stable with 2 up as my old bike did solo

I've been carefully following this thread since the beginning because it covers many of the same issues Dave and I have discussed at length when 'designing' my bike. For anyone contemplating the upgrade, '79 and '80 model bikes should have all come with the 39mm forks from the factory . . . . and the Intercepter bars offer a much more comfortable riding position than the sportkit bars do - One more 'advantage' in my book

Don

cbxtacy · Post by **cbxtacy** » Fri Jul 18, 2008 4:16 pm

pm me your address, I'll send you a cover, clean and polish it then chrome it, swap it out, and send me yours. Next time I'm in Mississippi you owe me lunch.

Don #6141 · Post by **Don #6141** » Fri Jul 18, 2008 4:24 pm

I'll buy you more than lunch if you ever transit the Gulf Coast on I-10 and can stop for a break George - No need to swap the covers

We'll go share a couple pitchers of NewCastle!

Don

cbxtacy · Post by **cbxtacy** » Fri Jul 18, 2008 6:15 pm

I've always been of the opinion if it doesn't feel like it needs it, don't put one on (steering damper). My wire wheeled 79 isn't real stable with or without it. It got a steering damper from when I road raced it and they were mandatory. My 82 needs one. My turbo (82 with VFR single sided swingarm, CBR600F3 front wheel) doesn't need one. Same suspension geometry but half the unsprung weight.

alimey4u2 · Post by **alimey4u2** » Fri Jul 18, 2008 7:39 pm

Three times I have been in a tank slapper. The first outside Bunn prison with my front wheel in the air. Another when I came across a Combine Harvester around the bend of a lovely fast North Carolina road. The third when I had both wheels in the air after crossing a railway line & spotting an oncoming North Carolina Highway Patrol car....

After the third time I realised I needed a steering damper...

cbxtacy · Post by **cbxtacy** » Fri Jul 18, 2008 7:49 pm

seems like my pro link CBX's have always been less stable then early ones. Early ones have smaller forks but everything is considerably lighter on them. I believe the lighter weight makes the difference. Maybe, also, the different suspension geometry. I've never had a pro link that didn't wobble at one time or another unless they got much lighter and smaller dia wheels with lighter brakes.

alimey4u2 · Post by **alimey4u2** » Fri Jul 18, 2008 7:53 pm

Could it be the effect of the fairing George ?

cbxtacy · Post by **cbxtacy** » Fri Jul 18, 2008 7:59 pm

Na, they were unstable naked. I think the weight is the biggest contributing factor.

alimey4u2 · Post by **alimey4u2** » Fri Jul 18, 2008 8:07 pm

cbxtacy wrote:Na, they were unstable naked. I think the weight is the biggest contributing factor.

Unsprung or just total weight George ??

cbxtacy · Post by **cbxtacy** » Fri Jul 18, 2008 8:15 pm

unsprung. The biggest contrubuting factor has got to be them vented rotors. But I believe it's three factors contribute to it. Unsprung weight, suspension geometry, fairing. and the biggest contributer is the unsprung weight. But I could be rong

alimey4u2 · Post by **alimey4u2** » Fri Jul 18, 2008 8:17 pm

Again, Thanks George.....

Don #6141 · Post by **Don #6141** » Fri Jul 18, 2008 9:52 pm

I found a lengthy dissertation on motorcycle stability and sure enough, front wheel weight was one thing cited as being a part of the problem

"Some bikes tend to wobble, especially when carrying an additional passenger or other heavy luggage near the rear. A most important point to bear in mind is that the fundamental mechanisim for causing this sort of wobble is inherent in the layout of the motorcycle and the only way to prevent it is to damp it out or tune it out of the system and the following measures may be helpful:

* Increase the lateral fork stiffness

* Reduce the trail; there are limits to this approach as it may impair directional stability

* Reduce the mass of the front wheel and fork, thereby reducing their moment of inertia about the steering axis. This cuts down the energy in the oscillating parts for a given magnitude and frequency of wobble, so that the inherent dampening has a greater proportional effect. This reduction of inertia also raises the system's natural wobble frequency

* Fit a hydraulic steering dampener"

They went on to say that for many bikes, it's only a problem 'hands off' because the natural dampening effect of the riders hands on the bars negates the problem to a large degree - We've all ridden some bikes where they felt quite stable with two hands on the bars, but a little shaky when you took one hand off. I know that when I took an otherwise perfectly stable dual sport bike down the Continental Divide, I began to have stability problems when I loaded it down with gear . . . . all piled on at the rear, even though I kept it all as low as possible

It sounds like front wheel and fork weight adds to the problem if you already have a wobble or instability problem, more so than the weight being the actual cause of the problem

For an early bike, a smaller, lighter wheel, coupled with stiffer forks seems to be the ticket. Pehraps the ProLink bikes got the stiffer forks because they were necessary due to all the added unsprung weight the huge vented rotors added? . . . . coupled with the extra mass of the fairing concentrated near the front - Added weight near either end can be a problem and after the added the fairing, they added the mounts and bags to the back. It's no wonder George feels the ProLinks feel more unstable

Wondering if Larry noticed any improvement when he went with the new Dymag wheel? Did things improve even more when you stiffened the front end by going to the 39mm ProLink forks? Riding impressions (without the dampener) at each stage of modification would be interesting . . . . and if you felt the dampener was still needed after all was said and done - Evidently you did as I gather the first time you installed the dampener was after all of the other improvements failed to solve the problem . . . . true?

I also wonder what the small increase in wheelbase I have due to the slightly longer 1100F rear swingarm has to do with the overall stability? Perhaps it also reduces the moment of inertia like reducing the weight of the luggage or passenger would do? I say this because my new red bike is waaaaay more stable two up than my previous silver stock bike was - It's about as stable two up as my earlier bike was one up . . . . and Carolyn has gained a bit of weight in the interim to boot ;)

One thing is a given: Small changes here and there to the chassis can make large changes in handling and stability. I would prefer to tune the chassis as much as possible and save the use of a mechanical dampener to a last resort . . . . though just installing one can be the 'easy' way out I guess - But it still seems like a Band-Aid over the real problem to me. Not all bikes wobble and it would be interesting to explore the small differences between them in an effort to understand why. As Mike added a few pages back - Some identical, stock bikes perform much differently than others do

Don