Modern Vespa

Well, I got the Bitubo front shock on the LX150 today. Another of those jobs that looked like it would take an hour, maybe more, that ended up taking three... Taking the old one off I could not get the nut off the tophat that is located on the brake/speedo side off. Grrrr. Then when I put the Bitubo on I had a bear of a time getting the same one started. I ended up getting the bolt shoved up into the hole and couldn't get it out. I ended up reaching around the top with one of those pick tools to get it loose.

Other than that, it was pretty straightforward to swap the new for the stock shock.

So, the instructions are next to worthless. How do I adjust this thing? The lower spring stop is adjustable, adding or removing compression, and the valving is adjustable. How much of each and when do I adjust valving and when do I adjust compression of the spring?

Also, did anyone get a spanner with their Bitubo? I didn't, and the spanner in the tool kit for the rear shock it too thick. I can grind it down to fit, but I don't want to too much for fear it won't work on the rear.

Thanks for any help,
Steve

Set the sag on the spring first, Steve, at one-third to one-half of the shock's travel. Then back-off all damping, and go for a short (and relatively slow) ride. You should feel the shock bouncing, due to the absence of rebound damping (like dribbling a basketball). Add about a quarter of the rebound damping, and continue your ride. Your shock should now be rebounding less (not dribbling without harder, or more frequent, input). If it's still bouncing, add another quarter of the rebound damping. Don't over-damp the rebound, or you'll be pumping-down the shock. The shock will not be able to recover, or expand, from the previous bounce. Now leave the rebound damping alone, and think about the compression damping. This one's much more subtle. The compression damping will mostly affect they way the shock responds to small abrupt bumps. If you add too much compression damping, your shock will feel harsh. Try riding without compression damping for a week or two, and then add a quarter compression damping at a time, to get a feel for the setting.
One final note, the damping settings are just trimmers. When you back-off the settings, you still have damping. The shock's valving, and spring rate, are the shock's major shock characteristics.

Thank you Gary! Very helpful and thorough, as usual.

I understand your instructions clearly except the initial "sag" setting. While I had the scoot on the jack with the shock at full extension, it still had some spring compression on it. I only had the adjustment nut up maybe 1/4" from the lower mount. It won't go full slack (no compression) when backed off completely.

I'll try this as the weather breaks again. It is raining now, and it is supposed to turn back into snow Tuesday, Wednesday and Thursday...

BTW, I completely understand the results without any rebound adjustment dialed in. My '29 Ford Model A did not have the optional lever-type shock absorbers. Rebound eventually was dampened by the semi-elliptical leaf springs. 70MPH in that thing was scary!

Thanks again,
Steve

You're welcome, Steve. I'm glad you found my explanation useful.
I believe you're referring to the spring's preload. The nomenclature is confusing, because the spring's preload compresses the spring. You use the spring preload ring to adjust the laden sag. I mentioned earlier to set the sag to 1/2 of the shock's travel. In practice, the sag is set between 1/3 and 1/2 of the shock's travel, with 1/2 being a better setting for a cantilever fork suspension.
The shock has a compression valve circuit, that resists initial compression of the shock spring. The compression setting is a trimmer for the shock's compression valve.

I'm interested in the progress of this post 'cos I've just had Bitubos fitted to my ET4 187. I have the same problems as Steve, but following Gary's instructions, I'm pretty sure I can sort the settings out.

Like Steve though, I'm having trouble finding a hook spanner to fit the preload adjustment rings on the shocks. Can anyone advise a solution ?? Has anyone else found a tool that fits ??

Sure. You can use a large pair of channel-lock pliers. They provide grip and leverage that's superior to a spanner. You'll find many other uses for them as well.

Thanks for the hint. I have been putting off adjusting my pre load again due to lack of a easy use tool. The slip joint pliers I understand, next to a hammer and duct tape one of the best tools, , Beale.

Gary,

I *think* we are talking about the same thing, but I may be confusing myself. Please look at the attached image and see if I follow along correctly.

As I understand, you are saying that I should completely back off and then tighten the compression adjustment nut by an amount 1/3 to 1/2 of the total travel of the shock. That "sets the sag."

Then I loosen the rebound dampener completely and go for a ride. Here's where I will have no dampening (your dribbling basketball example.) I then tighten the rebound dampener 1/4 turn at a time, but not so far as to over dampen.

I then make subtle 1/4 turn adjustments to the compression adjustment nut to adjust for small bumps and harshness.


As the compression adjustment nut is shown in the photo, I have it about 1/4" from being completely backed off. Pretty much hanging from the handlebars, I can compress the shock about two inches, but it has not bottomed out at this point. from what I understand, I need to tighten the compression adjustment nut another 1/2" to 3/4" to get to the initial "set the sag" setting? Then I add in rebound damper 1/4 turn at a time (it is currently backed completely off) and finally I come back and adjust the compression adjustment nut 1/4 turn at a time for fine tuning.

Do I understand correctly?

Thanks so much for taking the time to explain this for me (and hopefully others.) I expected that the shock would come with instructions, but alas... (I was also hoping it would come with the appropriate spanner. )

[edit] I see while I was writing that using slip-joint pliers came up. I use them in place of spanners in other applications, but wanted to keep the nice not on the Bitubo in good shape since it is so visible.

Steve,

The miscommunication is my fault. I should have defined laden sag from the outset. Please allow me to start over, from the beginning.

The shock has a range of travel, which should be specified by Bitubo. For explanatory purposes, let's say it's 3".
To set the sag, you'll need to measure the length of the front suspension when it's fully extended and unladen (not under any load). Then measure the front suspension when you're sitting on the scooter. That's the laden length (under the static load of the scooter plus rider). It should be 1" to 1 1/2" shorter than the unladen measurement. You can adjust the shock's laden length, with the spring preload ring. That's the ring that you've labeled "compression adjustment". The spring preload doesn't change the characteristics of the shock. It only adjusts where the shock sits, within its range of travel. It's a constant-rate spring. Let's say the spring rate is 60 LBS per inch. Even if the spring preload compresses the spring one inch, the next inch of travel is still at the same rate of 60 LBS per inch. It also expands at a rate of 60 LBS per inch, keeping the scooter's attitude level in potholes.

Apparently, the Bitubo shock doesn't have a compression valve trimmer. That's okay. As I've mentioned earlier, compression valving is very subtle.

The rebound valve trimmer should have a total adjustment travel, specified by Bitubo. It's usually graduated in "clicks", but could also be specified as a number of turns. When I say to add-in a quarter of the rebound damping, I mean to add-in a quarter of its full travel. For example, if the total rebound is specified as 12 clicks, then add 3 clicks for a quarter of the rebound damping. Road conditions are so dynamic, that is doesn't make sense to measure damping in any smaller quantity than a quarter of it's full range. You'd never be able to discern anything smaller.

Did I make it any clearer, or did I make it more confusing?

Gary,

Absolutely clear now! Thank you very much. I misinterpreted the terminology in your first post, and something you said in the second made me question my understanding of the first.

With what I have labeled as the compression adjustment nut backed completely off, and the damper adjustment backed completely off, there is a difference of 7/8" between unladen (wheel lifted slightly off the ground) to laden (with my 180# load on the saddle.) I bounced around a bit to get things settled.

There are 10 clicks on the damper adjustment knob.

So using your example of 3" shock travel (nothing is specified in any literature I have and searching for the LX 150 on Bitubo's page only links to http://tinyurl.com/rw8w5 ) my 7/8" sag adjustment would be almost at the 1/3 of the range ad you suggested.

Then I start with the rebound adjuster knob turned it 2 clicks (a little less than 1/4 of the range) and work from there.

Got it! Don't I?

Arrrggg! Rain, snow and high in the low 30s until next weekend. Can't really road test in that...

Thank you again Gary for your patience, thorough explanation, and knowledge! You are truly a valuable asset to Modern Vespa!
Steve

I have a pair of these too, but was hoping to find a more purpose built tool to protect the condition of the adjuster rings.

What I'd really like is something like the channel-lock pliers, but with "teeth" that fit into the notches on the Bitubo adjustment rings.

Ideas anybody ??

Yes cynic64, you can buy spanners. It will be hit and miss to find one that's perfect for the Bitubo ring though.
Bicycles use spanners for their headsets and bottom brackets. Park tools makes professional tools for professional bicycles. Try Park Tools, Performance Bicycle, and Bike Nashbar on the web.
Another suggestion is to slip-on two short lengths of rubber hose, onto the jaws of your channel-lock pliers.

Excellent, Steve.
I'd add-in a little more laden sag though. I recall reading in published literature, that the stock shock travel is 3.4". I'd make the laden sag at least 1 1/4". You don't want the shock topping-out in dips and holes, if you can avoid it.
Two clicks-in on the rebound damping is a perfect starting point. Ride around with 1 1/4" laden sag and 2 clicks-in damping for a while, until you think you can characterize how bouncy the front-end is. Dippy, wavy, roads are better for this than broken road surfaces. Remember, the rebound control is just a trimmer. The shock valving already matches the spring rate.

Cheers Gary, I'll try your web suggestions and see what they've got. I'm also going to talk to a couple of the local motorbike dealers and see what they have, given that a lot of sports bikes now use adjustable shocks.

Thanks again

Julian (a.k.a cynic64)

Will do! Thanks again for the help.

Next up, the Variator on the Metropolitan and then the LX. But first I've *got* to replace an injector on the WRX! Come on, Spring!

Hi
I don't have the Bitubo shock, just the stock shock and have tried various c-spanners and the channel-lock pliers but with no success. I don't remember having this much trouble when adjusting the shocks on my motorbikes. The shock is on the softest setting and occassionally bottoms out when hitting potholes. My daughter wants to have a go as pillion passenger so I need to adjust it to take her extra weight. Is it possible for the adjustment nut to have ceased as there is quite alot of salt corrosion on the back end of the scooter (it was like this when I bought it).

Suggestions would be welcome.

Wendy

Have you got the proper "knuckle skinning" tool? Give it a squirt with WD40 first,then have a go...

Hope this helps.

I don't have the original tool kit as the scoot was second hand, but have tried the WD40 with no success.

Wendy

Hmm,you might be right then,it may be seized...

I seem to remember someone on here had a spare tool. (Sorry,that sounds REALLY bad.... ).Give it a while,I'm sure they'll chip in..

If there is a dealer/shop nearby, you can ask them if they would do the adjustment for free. I would think that they may be fine with that. I'd ask, though, if they were planning on charging ahead of time. I had to replace a tiny screw that fell out of my Toyota keychair automatic door lock controller. The service person picked one off of the counter, and then wrote up an invoice for 34 cents!

Edit: I didn't read the part about the shock being seized. I doubt that a shop would happily agree to unseizing it for free

Ian,

Are you refering to this post - I Can't find this tool on line!

Tim

Yes Tim,I was... Is it the same tool for a GT and an ET4?

I'd go with Harnadem's advice though....no tears and blood that way...

I'm not sure but when I 1st saw that post I looked everywhere for that tool and I even had a hard time trying to find it on the Motion Pro site.

Tim

I got a shock spanner off of EBay to adjust shocks on Vespas and Lambrettas, it does fit perfectly but it's quite short so you can't get any leverage.

'Scoots' I know what you mean about shedding blood, I 've only had my ET for just over a week and already have cuts/grazes on my hands!

'Harnadem' I think your right, there is a local motorcycle shop that does work on any make of bike, I will give them a ring tomorrow and see what they can do.

Thanks for all your replies.

Wendy

Please Wendy,call me Ian...

The one you get with the kit doesn't give you MUCH leverage!

Get used to the blood/cuts/grazes,it comes with the bike.Whenever my wife sees me armed with spanners,she gets the first aid kit out!

I slid a pipe over the spanner wrench that came with my ET4 when I adjusted the rear shock so I could get more leverage.

Tim

I tried the pipe bit, but as I didn't have a piece of pipe I took the bung out of the end of a paint roller, gave me the leverage alright, but the shock wouldn't budge. The bung will not go back in now as the pipe is somewhat mis-shapen!!

Wendy