2020 V4s suspension discussion

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So finished up the suspension work and ended up here:

Front
10/15 preload.
Free sag: 28mm
Rider sag: 40

Rear
17mm preload. (6mm less than stock 85n spring)
Free: 14mm
Rider: 32

I am still bottoming out the front forks with the 11.0 springs. I can’t believe I’m going to have to go to a 12 at 220-ish pounds fully loaded with gear. I’m at 10 of 15 preload adjustment. Was 13/15 on 10.0 springs. I would’ve thought a bigger change.

It’s only happening on 160mph to 40ish HARD BRAKING… and on the track where I’m coming down from even faster. I think it’s going to be worse….
Reduce your air gap. A little bit makes a lot of difference (there’s a chart in some of the Ohlins fork manuals that show how quickly the force increases as the gap reduces). Maybe 10 to 15 ml of oil per side at first and see what happens.
 
Reduce your air gap. A little bit makes a lot of difference (there’s a chart in some of the Ohlins fork manuals that show how quickly the force increases as the gap reduces). Maybe 10 to 15 ml of oil per side at first and see what happens.
Will try this next. To confirm. Air gap is set without spring installed and little plastic spring holder. ?
 
So finished up the suspension work and ended up here:

Front
10/15 preload.
Free sag: 28mm
Rider sag: 40

Rear
17mm preload. (6mm less than stock 85n spring)
Free: 14mm
Rider: 32

I am still bottoming out the front forks with the 11.0 springs. I can’t believe I’m going to have to go to a 12 at 220-ish pounds fully loaded with gear. I’m at 10 of 15 preload adjustment. Was 13/15 on 10.0 springs. I would’ve thought a bigger change.

It’s only happening on 160mph to 40ish HARD BRAKING… and on the track where I’m coming down from even faster. I think it’s going to be worse….
So wanted to finish up this thread with results and learnings…for future reference and new members doing this themselves for the first time like me!



So when I did this the first time around, (BIG thanks go BP who lent me tools, and provided phone tech support!!), it was a pain, first fork took me several hours, second fork took me 40min!

Key points:

1 – get a head stand that lifts from above the tire, on the frame/lower triple, regular fork stands won’t work, so you’ll have to support bike from rafters or get creative otherwise!

2 – once fork is removed, simple matter to unwind all the preload, then unscrew the top cap and pull out careful not to damage/bend the long pole with needle that runs all the way to bottom of fork. Use a wrench and cap tool to break the nut on the center rod loose, then simply unscrew the top cap all the way.
IMG_3674.jpeg

IMG_3676.jpeg

3 – Next you gotta remove the stock spring, to do that you have to use a center rod pullup tool, or needle nose pliers to unload (lift up on center rod)..this takes the pressure off the nut and you can then use your fingers to remove the nut fully…then slide off the metal spacer that was held down by the nut and spring pressure. Note: carful with the pliers on the center rod…you can mar and cause some particles and debris then cause you issues down the road (lesson learned!) Best to use pickup rod instead.

IMG_3779.png

4 – Now invert the forks and dump the oil. When you refill the oil level in forks is measured WITHOUT the spring and plastic collar. 230mm is the proper fluid level, if you set it with the spring and collar installed your level will not be correct. Work the center rod up and down and you’ll be surprised how much oil comes out. Best to leave hanging upside down overnight. Best to waste a liter or so of good oil by adding 300mL, working the center rod up and down, then dumping again, and repeat until the dumped oil is clean looking!

5 – Install plastic collar, replace spring, shove the metal holder piece down, compress spring with your hands to get the nut started, then work that nut all the way down the center rod, almost until the end of the threads.

6 – Screw on the top cap/rod with needle, until its fully screwed IN. It will hit a hard stop when you are at the end of travel (why its important to drive the NUT all the way down in step #5 above). THEN bring the NUT up flush with the bottom of the cap and tighten holding the preload (top blue part of cap) steady. Do NOT use the cap removal tool on this step, you will then prevent the preload part from being able to move! This is hard to visualize the first time you do it, and is the reason I spent an embarrassingly long time on the first damn fork!
IMG_3671.jpeg



Final thoughts:

1 – I got frustrated and was a little rough with the pliers (ordered pull up rod after first run through!), this marr’ed the center rod and caused some metal debris to drop down in the bottom of fork!

2 – I didn’t flush first time with clean oil, just dumped and replaced.

3 – I didn’t work the center rod enough to get oil fully through the entire assembly during refill process. This caused my oil level to be way too high artificially and therefore I had too little oil in the forks.

1 and 2 and 3 combined to make it so when I first got everything back together, my test ride produced some crappy results: I was bottoming out easily. I set my preload to 8/15 and 15/15 and still bottomed out the same, that’s when I knew some Phuckerey was going on….

So when I took it all back apart and actually used a liter of fresh fluid to pump it out again and again until it was clear, I also got a lot of the marr’ed center rod crap (metal debris)…it had to have been blocking the fluid pathing internally…which caused some funkiness on my forks! Also my fluid level when I removed spring and collar was WAY too low, as in not enough fork oil…



So ALL THAT TO SAY:

Here is my data after redoing it all:

Rider weight with full track gear: 226lbs



Front: 11.0 spring installed from 10.0 stock spring.

8/15 turns preload

40mm rider sag

26mm free/bike sag



Rear: 105n spring installed from 85n stock spring

12mm preload.

12mm thread showing above top collar, spring measures 160mm exactly off the bike = 12mm of preload on the spring installed. Total distance available on shock is 174mm (from bottom of shock to end of threads on top).

(174-160 = 14mm, the two collars combined are 14mm, so my actual preload installed on rear spring is 12mm. With zero threads showing above top collar, you would have Zero preload on the spring. So whatever your MM measurement above top collar IS your installed preload, assuming your spring is actually 160mm (mine was).

30mm rider sag

15mm free/bike sag

EDIT: PS - i did replace seal and dust sleeves as well during this work. the fixed bearings were fine with only 4k miles, did not replace those...
 
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One thing to note, the damper rod is threaded internally. When removing the nut on the damper rod, if you thread a bolt into the damper rod you can use an hex head socket to spin the damper rod while holding the nut to remove it from the rod. If the bolt you use is long enough, you can also use it to pull up the damper rod.

I found working all the air out of the rebound (right) fork took way longer than the compression (left) fork.
 
One thing to note, the damper rod is threaded internally. When removing the nut on the damper rod, if you thread a bolt into the damper rod you can use an hex head socket to spin the damper rod while holding the nut to remove it from the rod. If the bolt you use is long enough, you can also use it to pull up the damper rod.

I found working all the air out of the rebound (right) fork took way longer than the compression (left) fork.
Think I used some allthread with a double nut and fender washer at the top, threaded into the ID of the cartridge- makes for a decent pull up handle, and also captures the cartridge nut so it won't go flying if you aren't ready for it to pop off. The reverse is easier too, as that nut is fine thread, so with the cartridge pulled up the nut automatically centers so it's easy to start back on. If it's long enough it keeps your contact points out of the fork oil if you let everything drop into the tube once the nut & retainer are off.
 
To hold the fork tube to service, I get a piece of 2x4, bore an appropriate hole, rip it down the centerline, then put it in the big vice and clamp it down clam shell esque. Same thing with the cartridges if they need to be taken apart for damping stack changes.
 
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