[Inclag]

Modding my Boxxer Team to 7" of travel tonight if it is possible. I'd like to make a 1" shorter dummy rod, but don't have the proper 0.500" stainless steel tubing to fabricate one at the moment.

So I was wondering what points are colliding during bottom out on the Boxxer? Is it the bottom of the stanchion against the lowers? If so, I presume that I should be able to add a 1" spacer between the spring base plate and lowers, to reduce travel by 1" and then just slide the stanchions up in the crowns to lower the front fork.

 

[NJHCx4xLIFE]

When you lower a fork you limit how far it can extend, not how far it can compress if that makes sense. It tops out 1" inch shorter instead of compressing 1" less at the end of the stroke. My Lowered RS sits lower in the travel from the start. Never lowered a boxxer though so not sure what you need to do.

 

[Welshy.]

The best and most commonly used way to lower forks is by adding a spacer under the top out spring. This will effectively pull the stantions (in this case) one inch lower into the lowers.

The only complication then is working out oil heights for the damper side.

 

[Inclag]

The best and most commonly used way to lower forks is by adding a spacer under the top out spring. This will effectively pull the stantions (in this case) one inch lower into the lowers.

The only complication then is working out oil heights for the damper side.

Only problem with this is that it adds, 1" of length and preload to the main spring, which will not work out so well.

I may be able to cut the main spring by ~1" and flip a spacer back and forth between the main spring and negative spring for 7-8" of travel. Will have to check the main spring though to see if I can still manage 8" of travel while removing 1" of its free length.

 

[Inclag]

When you lower a fork you limit how far it can extend, not how far it can compress if that makes sense. It tops out 1" inch shorter instead of compressing 1" less at the end of the stroke. My Lowered RS sits lower in the travel from the start. Never lowered a boxxer though so not sure what you need to do.

 

[NJHCx4xLIFE]

Said the same exact thing as Welshy

 

[Welshy.]

He was trying to say that your method would only change where the fork bottoms out, not the stantion length.

In theory, your method could work. There is a ~4mm thick rubber bumber at the bottom of the lowers on the spring side, if you sourced another one of these, and made up a spacer as per your original idea and popped the bumper on top of it (purely for peace of mind) it could work.

Only down side is the added stantion length above the top crown, but if that doesn't worry you, your plan should go down no problems.

 

[NJHCx4xLIFE]

He was trying to say that your method would only change where the fork bottoms out, not the stantion length.

In theory, your method could work. There is a ~4mm thick rubber bumber at the bottom of the lowers on the spring side, if you sourced another one of these, and made up a spacer as per your original idea and popped the bumper on top of it (purely for peace of mind) it could work.

Only down side is the added stantion length above the top crown, but if that doesn't worry you, your plan should go down no problems.

Could work except the fork would be bottoming out on that bumper over and over instead of rarely like when using the fork the way it was designed. The way you described sees a lot less force (just that of the spring extending) compared to the force of all the weight/force compressing the fork at bottom out slamming into that spacer.

 

[Inclag]

He was trying to say that your method would only change where the fork bottoms out, not the stantion length.

In theory, your method could work. There is a ~4mm thick rubber bumber at the bottom of the lowers on the spring side, if you sourced another one of these, and made up a spacer as per your original idea and popped the bumper on top of it (purely for peace of mind) it could work.

Only down side is the added stantion length above the top crown, but if that doesn't worry you, your plan should go down no problems.

That's what I thought my first post said. Reach bottom out sooner and just slide the stanchions up in the crowns.

I do like the idea of cutting the spring and just flipping around a spacer, however that may be a little more time than I bargained for for a night project.

 

[Inclag]

Could work except the fork would be bottoming out on that bumper over and over instead of rarely like when using the fork the way it was designed. The way you described sees a lot less force (just that of the spring extending) compared to the force of all the weight/force compressing the fork at bottom out slamming into that spacer.

As long as oil heights are corrected and proper spring rate is achieved there's no reason that anything else would be different.

 

[Welshy.]

That's what I thought my first post said. Reach bottom out sooner and just slide the stanchions up in the crowns.

I do like the idea of cutting the spring and just flipping around a spacer, however that may be a little more time than I bargained for for a night project.

Hang on, thinking about it now, the Boxxers do come stock with a fair bit of preload on the spring. You may be able to get away with just removing the preload spacers, 5-10mm worth, and then trying to compress the spring slightly to put the top cap on.

True, you will have slightly more preload, but it saves you cutting your spring, and allows you to do it the seemingly safer and easier method.

 

[Inclag]

Hang on, thinking about it now, the Boxxers do come stock with a fair bit of preload on the spring. You may be able to get away with just removing the preload spacers, 5-10mm worth, and then trying to compress the spring slightly to put the top cap on.

True, you will have slightly more preload, but it saves you cutting your spring, and allows you to do it the seemingly safer and easier method.

Hmmm, that may work. I'd probably want a hair more preload anyway to stay a little higher in travel if I reduce it some as it is. Guess, I'll make a spacer and leave the spring as is and see how it feels afterward.

 

[davep]

Limiting the travel with larger bottom out bumpers will require a different, stiffer spring. You will loose the last (stiffest) inch of spring compression and will be most likely slamming your stanchions through the B/O bumper eventually. You might also mess up the damper side seal head with repeated impacts.

The proper way to do this is to add a shim to the negative/top out spring to prevent fork extension. Whatever shim length you choose would be the amount of travel lost and the amount the overall length of the fork would shorten. You can use PVC, or a longer spring, or travel spacers...whatever. Of course, this requires a shorter main spring or it will be pre-loaded via the ammount that you added to the top out spring.

As mentioned, the boxxer does require (IIRC) a minimum of 2 or 3 spring pre-load spacers stock. At 5mm each, that is 1/2 inch. I would think, that simply removing the all pre-load spacers (and maybe fabing up a thinner one to sit at the bottom of the spring/top of the spring rod as it is 5mm as well I think) would result in enough 'slop' to be able to shorten the fork without modding the spring...It is certianly worth a try as it would be 100% reversable and would not take much time to try it out.

The down side is the spring might either be over-preloaded, or too soft or both for the new travel amount, where as cutting the spring will increase its rate by the exact ratio of the change in travel.

 

[b1k3_r1d3r]

why not buy old 7" boxxer springs, they have to be somwhere, then you do the negative spring mod of adding a spacer and your set.

 

[davep]

two springs vs one, the rate would be WAY off unless you were a super lightweight and ran a single 7" extra stiff.

I have not had them side by side, but the 7" springs may not be 1" shorter either. Stanchion length, pre-load spacers, spring rod configuration, etc could all be different enough to effect the spring length significantly.

 

[Inclag]

Limiting the travel with larger bottom out bumpers will require a different, stiffer spring. You will loose the last (stiffest) inch of spring compression and will be most likely slamming your stanchions through the B/O bumper eventually. You might also mess up the damper side seal head with repeated impacts.

The proper way to do this is to add a shim to the negative/top out spring to prevent fork extension. Whatever shim length you choose would be the amount of travel lost and the amount the overall length of the fork would shorten. You can use PVC, or a longer spring, or travel spacers...whatever. Of course, this requires a shorter main spring or it will be pre-loaded via the ammount that you added to the top out spring.

As mentioned, the boxxer does require (IIRC) a minimum of 2 or 3 spring pre-load spacers stock. At 5mm each, that is 1/2 inch. I would think, that simply removing the all pre-load spacers (and maybe fabing up a thinner one to sit at the bottom of the spring/top of the spring rod as it is 5mm as well I think) would result in enough 'slop' to be able to shorten the fork without modding the spring...It is certianly worth a try as it would be 100% reversable and would not take much time to try it out.

The down side is the spring might either be over-preloaded, or too soft or both for the new travel amount, where as cutting the spring will increase its rate by the exact ratio of the change in travel.

Finishing up the mod right now and throwing the fork back together. Ended up turning a Nylon (Bright green bearing material Nylon, sorry forgot the name but it doesn't matter) spacer that reduces travel ~ 0.9" for the top out space.

Fabbed a thinner preload spacer too, but as of right now am using one of the standard ~ 0.125" thick Boxxer ones. Will see how this feels and play around with preload and springrate accordingly.

 

[Steve M]

Limiting the travel with larger bottom out bumpers will require a different, stiffer spring. You will loose the last (stiffest) inch of spring compression and will be most likely slamming your stanchions through the B/O bumper eventually. You might also mess up the damper side seal head with repeated impacts.

The proper way to do this is to add a shim to the negative/top out spring to prevent fork extension. Whatever shim length you choose would be the amount of travel lost and the amount the overall length of the fork would shorten. You can use PVC, or a longer spring, or travel spacers...whatever. Of course, this requires a shorter main spring or it will be pre-loaded via the ammount that you added to the top out spring.

As mentioned, the boxxer does require (IIRC) a minimum of 2 or 3 spring pre-load spacers stock. At 5mm each, that is 1/2 inch. I would think, that simply removing the all pre-load spacers (and maybe fabing up a thinner one to sit at the bottom of the spring/top of the spring rod as it is 5mm as well I think) would result in enough 'slop' to be able to shorten the fork without modding the spring...It is certianly worth a try as it would be 100% reversable and would not take much time to try it out.

The down side is the spring might either be over-preloaded, or too soft or both for the new travel amount, where as cutting the spring will increase its rate by the exact ratio of the change in travel.

Correct on all counts except that last one - cutting the spring 1" won't up the rate to 8/7ths its original rate, because you're not removing 1/8th of the spring's actual free length (since spring length /= fork travel). It will at least help however, as by and large it's a step in the right direction.

 

[captainspauldin]

The only complication then is working out oil heights for the damper side.

That won't matter, the rebound piston will just be 1" higher than normal, the oil will still flow into the compression the same way as if it was 8" of travel..

 

[shift96]

Just buy a 7" fork

 

[Inclag]

Just buy a 7" fork

Why?

I was able to convert my 09 Boxxer Team to a hair over 7" of travel in the matter of an hour after determining which method to go about it, all for a total cost of zero legal tender.

 

[shift96]

So it's a 7.25 or so fork now? Why even bother. I like to tinker just like the next guy so I guess I understand. sounds like it was a cool project though.

 

[Inclag]

So it's a 7.25 or so fork now? Why even bother. I like to tinker just like the next guy so I guess I understand. sounds like it was a cool project though.

More like ~7.1".

I found that my demo 8 handled loads better in the taller and steeper setting so I decided to flip the rear shock links back to the slacker and lower setting and lower the fork and it's travel to maintain a steeper geometry.

Now my bike in the low setting has a 13.9"ish BB as opposed to the standard 14.5" or taller 14.96". But now I have a head angle that is the same or damn near around what the steep/tall setting was. In theory this should help even more with cornering and maintaining a lower COG.

Guess I'll know more after racing this weekend. It's easy enough to go back to the steeper and taller setting if I decide on that being the ideal riding setup for myself.