6" spacer on Progressive fork springs??

[scaylabs]

Hi guys,

I'm doing the fork seals on my 82 1100GL and installing Progressive springs. My problem is that the new springs are over 3" shorter than the stock ones! I would need a 6" spacer to make it to the edge of the forks.

I don't see anyone with spacers this big, could it be correct?

The springs are the 11-1107 which are the ones listed on progressivesuspension.com for my bike.


Here you can see the Progressive spring (18"), the stock spring (21 1/4") and the stock spacer (3 1/8")

[salty_monk]

I believe the ones on my 1000G were 90mm which is about 3 1/2".

As long as the space between the coils adds up enough that it can't go coil bound (i.e. the coils can't all touch when fork is at full travel) you'll be fine.

If you google there is a calculator somewhere that allows you to put in length, wire dia & number of coils plus travel but it's easy enough to work out manually.

Basically count the number of coils & multiply by the wire diameter then take that figure away from the total length & make sure the resulting figure is more than the 5" of fork travel that your bike likely has....

[scaylabs]

Thank you, that was fast!

A little more search brought a couple of similar questions and they ended up using the stock spacer plus an additional 3" PVC one, so I guess it's OK.

Thanks again!

[mike_of_bbg]

You can review the Progressive part specs here:

http://www.progressivesuspension.com/pdfs/7100-105.pdf

Although they sell slightly longer springs, the 1107's seem to be unique in their spring rate and OD. Anything you bought would require a spacer.

The L's have longer fork springs I think because the axle isn't below them.

[OLDENUFF]

Had exactly the same problem with the progressives that came for my 1980 L. I called Z1 and spoke to Chris. He in turn called progressive about it and called me back. What a great bunch at Z1. Anyhow they said a 6" spacer was way too much. I would have very little travel. They did come up with a spring 20 3/4 " with the same rate. Call Chris @ Z1 and explain it to him. It was just last week so he should know exactly what you are talking about. Good luck with it.

[salty_monk]

I don't get that... as long as the coil can't bind then there is no problem using as much spacer as it takes in my opinion.

Do the maths...

[scaylabs]

I don't get that... as long as the coil can't bind then there is no problem using as much spacer as it takes in my opinion.

Do the maths...

If I got what you meant earlier, since the G and the GL have the same fork travel (160mm according to my service manual) the most that the spring will need to compress is also the same, even if the total length (with spacer) is longer on the GL.

[Steve]

A little more search brought a couple of similar questions and they ended up using the stock spacer plus an additional 3" PVC one, so I guess it's OK.

Why not just use a single piece of PVC that's 6" long?

.

[scaylabs]

Just 'cause the kit comes with a 10" piece of PVC, not 12".

I could make a Home depot run if you think it makes a difference.

[mike_of_bbg]

Remember that the Progressive springs are stiffer, and you might not need as much pre-load: on the other hand, the stock springs are probably sacked and the included 3" spacers might not be enough pre-load. Measure how deep your tubes are. Aim for 1-1.5" of pre-load, adjust as necessary. I'd also use a single PVC spacer in each tube and put an appropriate washer between the spring and PVC if you don't have an appropriate stock spacer.

[Steve]

Just 'cause the kit comes with a 10" piece of PVC, not 12".

I could make a Home depot run if you think it makes a difference.

See my comment below, 5" spacers might work for you.

Remember that the Progressive springs are stiffer, and you might not need as much pre-load: on the other hand, the stock springs are probably sacked and the included 3" spacers might not be enough pre-load. Measure how deep your tubes are. Aim for 1-1.5" of pre-load, adjust as necessary. I'd also use a single PVC spacer in each tube and put an appropriate washer between the spring and PVC if you don't have an appropriate stock spacer.

All this talk of preload does not make a bit of difference until you measure how much you need.

To determine how much you need, you need to measure your suspension's "sag". Measure between two points with the forks at full extension, when it's on the center stand. You can measure from the bottom of the lower triple tree to the top of the dust boot on the slider. You will need help with the next step, but take the bike off the centerstand, put your weight on the bike like you would be riding down the road. Measure between the same two points. You are looking for no more than 20-25% "sag". Most of our forks have about 6" of travel, so you are looking for 1-1.5" difference. If, for example, you have 2.5" of sag, you need to add 1-1.5" of spacer to bring it back up to the proper height. If your current spacer is 3", that means your new spacer needs to be 4-4.5".

The same principle applies at the rear, as far as choosing your preload, only you have about 4", instead of 6" to play with, so your "sag" should only be .75-1.0".

.

[Nessism]

Those springs are designed such that the spacers should come up flush with the top of the forks at full extension. After installing the top cap there is roughly 3/4" of actual spring preload. I don't know how long the spacer would have to be to achieve this, but I'd start there with the spacers and then adjust as needed per Steve's suggestion.

[mike_of_bbg]

All this talk of preload does not make a bit of difference until you measure how much you need.

Did I not say, "Adjust as necessary" ???

He needs to start with something. The new springs are shorter (see OP) and 3" spacers will probably be negative pre-load. Plus they'll be stiffer, so pre-load measurements with his old springs aren't going to be representative.

Yes, sag in the range of 20-30% is what you're after. I've gotten the impression reading lots of Progressive fork spring posts that 1-1.5" of pre-load with Progressive springs gets there pretty well. I'd aim for the longer range, as saws are usually better at making spacers smaller rather than larger Washers can help make incremental lengthening adjustments though.

[salty_monk]

If I got what you meant earlier, since the G and the GL have the same fork travel (160mm according to my service manual) the most that the spring will need to compress is also the same, even if the total length (with spacer) is longer on the GL.

You are correct, if the fork travel is quoted at 160mm that's all the compression you need (plus a little bit for safety sake I would say).

Measure the spring in mm (We'll call this figure "Y"). Measure the wire dia in mm. Count the number of coils.

Multiply number of coils by Wire Dia. (We'll call this figure "X")

Subtract X from Y to see if it's larger than 160mm. So Y-X=>160mm

It's pretty simple. As long as it does, use the suggestions above to sort out preload & exact spacer length. Level with the Top of the tube as progressive suggests is usually about right for me (165lb without gear on).

I always put a washer between spacers, you can double them up with a washer between them but a single piece is neater. One trick I have used is if you run out of pipe but only need 5mm extra preload or something just put a couple of extra washers on the top.

Best,

Dan

[Steve]

Did I not say, "Adjust as necessary" ???

Yes, you did.

However most people freak out trying to get the spacer length correct before putting it together to measure the sag.

Like you went on to say, "you have to start somewhere". If you measure more than the desired amount of sag, adding to the spacer length will only raise ride height with the current springs. Hopefully, you won't bind the springs before end of fork travel.

In an ideal world, the springs would be the perfect strength and the perfect length, but that would be too many variations, so they make them in specifit strengths (spring rate) and let us adapt the length.

.