Lowering forks

[AndrewB]

I'd like to lower my front forks approx 1" by adding a set of the small compression springs (from a R80 RT) below the valve housing on the absorber. I'd then cut off the large main spring the same height as the small R80 springs to compensate for the lowers sitting higher up the stanchion.
I've been running a 90/100 front tire and would like to return the footprint closer to stock while keeping the larger front tire. I'm also hoping my progressive springs will soften up a little with the small compression springs.
Has anyone done this or anything similar?

[steve hawkins]

No but I have allowed my fork legs to protrude throught the top yoke by half an inch to compensate for running a 19 inch wheel.....It was easier......

[Barry]

I'd like to lower my front forks approx 1" by adding a set of the small compression springs (from a R80 RT) below the valve housing on the absorber.

Do you really mean below the valve housing ?  The right hand spring #11 has no effect on ride height at all it's just spring loading the later type valve body.

or are you thinking below the damper rod piston like a topping out spring. This would be the left hand spring #11 in your top diagram.

Which ever way you do this have you measured static and rider sag with your current setup and do you know what figures you are aiming for with the new setup. For stock springs static sag should be around 30mm and rider sag 45 -50mm. For riders of average weight the stock springs give rider sag figures in the recommended ball park which usually means that unless the rider is above average weight stiffer than stock springs are a bad idea. My apologies in advance if I do you a disservice but do you realise shortening the main spring will make it even stiffer.  

[AndrewB]

I was thinking I would place the #11 spring (R80 1st diagram) bellow #21 (R65 2nd diagram). Similar set up to the picture bellow.

I had thought about raising the forks thru the top yoke but my understanding is it's not possible on my 83.

[Barry]

 Your fork internals if original do not look  like the picture above and you would not be able to fit the spring in that position.

#21 in the lower diagram is the old style full length valve body which is held inside a recess in the bottom of the stanchion by a circlip #19. There is no room for a spring between the valve body and circlip. There is only room for a thin shim #20. If you put a spring on the other side of the circlip all it would do is act as an anti bottoming spring. They were available as an after market part at one time for the mainstream airhead forks but are not considered a good idea as they reduce available fork travel.

Did I read that you have progressive springs fitted ? If so I wonder if the real problem is that the springs are too stiff. Measuring static and rider sag will tell you if the spring rate is in the right ball park.

[AndrewB]

"If you put a spring on the other side of the circlip all it would do is act as an anti bottoming spring. They were available as an after market part at one time for the mainstream airhead forks but are not considered a good idea as they reduce available fork travel."

So what your saying is I could achieve lowering the forks by adding these springs bellow the circlip? But at the cost of fork travel and a stiffer ride?

My main goal is getting the cornering ability back, while keeping the larger tire. The stiffness of the shocks is secondary.

[nhmaf]

The 81-84 twin shock (rear) bikes all used the same fork and steering yoke, so you can slide the tubes upward above the top yoke/plate if you wish.   This would give you a lower ride height but maintain existing suspension travel.  It will tend to affect the rake and wheelbase, so steering will get quicker.  Be careful not to overdo.

[montmil]

... I had thought about raising the forks thru the top yoke but my understanding is it's not possible on my 83.

Handlebar interference, correct?

[Barry]

So what your saying is I could achieve lowering the forks by adding these springs bellow the circlip? But at the cost of fork travel and a stiffer ride?

Adding springs below the circlip will not  change the ride height nor will it stiffen the ride except very close to full compression when it reduces the maximum fork travel.

To lower the ride height with springs you will have to increase rider sag (the amount of fork travel used up just by sitting on the bike). Taken beyond 55mm means there will be less than 2/3rds  fork travel before the forks bottom out. Not a good idea but if you really want to do it you need to use that short spring as a topping out spring. That is fit it under the damper rod piston in place of or maybe in addition to the topping out bush #24 on the lower diagram. I know that Progressive market these short springs as a kit together with a shorter main spring for lowering Harley's by 1" or 2 " In that case they add 1 or 2 short springs  to the existing topping out spring which sounds crazy to me but you might find some guidance on their web site. The only thing that I have which illustrates the idea is the left hand example in the diagram below. Bear in mind that our forks have a short poly bush in place of  the first top out spring.

[nhmaf]

... I had thought about raising the forks thru the top yoke but my understanding is it's not possible on my 83.

Handlebar interference, correct?

One can get at least a significant fraction of an inch with the standard bar mount, but with bar risers/barbacks or clipons one could get into the realm of the ridiculous in my opinion..
 

The fork travel on the R65 is already somewhat less than the R80/R100, and I think if one were to further reduce the travel, it would get very stiff/hard/nasty very quickly, again, just my humble opinion.

[AndrewB]

Barry thanks for the info. In the future I may go with shorter shocks in the rear and a lower front end as well.
For now I'll raise the fork tubes through the top yoke by a 1/2". I'm running Euro style handlebars so the tubes will clear fine.
What's the best way to do this? Should I remove the front wheel, fender etc. and do each tube separately, measure w/ a vernier caliper? Or leave the wheel, fender, etc intact, and slide both up at the same time?
I'm a little concerned that the tubes with be hard to slide up and may need some motivation. I don't want to bend those tubes out of alignment.

[AndrewB]

Well I've been riding for a few weeks with the forks lowered by about a 1/2". The nice cornering ability is back, I'm really enjoying it. Also sits better on the center stand.
To do this I removed the front wheel, fender brace and fender. Then loosened the four bolts on the yokes holding fork legs. I grabbed on to one fork leg just bellow the bottom yoke and turned it back and forth. slowly moving it up a half inch. Repeated the process on the other leg. Dialed them both in evenly by measuring the fork length protruding through the top yoke. I ditched the plastic dust covers for added clearance. Then tighten everything up to factory torque.
I also removed the plastic spacers that came with my Progressive fork springs. This added some sage and improved the ride.

[wirewrkr]

The 81-84 twin shock (rear) bikes all used the same fork and steering yoke, so you can slide the tubes upward above the top yoke/plate if you wish.   This would give you a lower ride height but maintain existing suspension travel.  It will tend to affect the rake and wheelbase, so steering will get quicker.  Be careful not to overdo.

Steering will be a little different, but the rake is permanently set at the factory, as well as the wheel base.
They don't changed unless you cut the frame neck and and move it.

[steve hawkins]

If you shorten one side of a triangle, then the at least one angle and one other length will change......It will be the one that is not fixed.....

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