V2 MotoAmerica Race Bike Build

Bruce Wayne said:

All race teams measure and set the shock length like this, it's the only accurate way of getting repeatable measurements. Andriani has a store in the US or go through WRS Italy they have it listed on their website, it's about $1,100 AUD not sure what US price is

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I see. Well, I would probably just have the suspension place do it. I’m assuming they have that tool. If not, I’ll find one that does.

I didn’t know you could change the length of a “preset” shock. I guess I’m still learning a lot.

Is 323mm where it just “ended up,” or did you pick that, specifically? I was going to try and get mine to 321-322, so 323 is right in the range.

You can buy new // tech one from Andreani USA:
https://andreaniusa.com/product/andreaniandreani-tools04-u20-1132/Or the older style Ktech one from Orient Express:
https://www.orientexpress.com/product/20022/k-tech-suspension-shock-tools
^^^ this seems to have gone up in price quite a bit, I think I paid $450 for mine years ago

JBJR said:

I see. Well, I would probably just have the suspension place do it. I’m assuming they have that tool. If not, I’ll find one that does.

I didn’t know you could change the length of a “preset” shock. I guess I’m still learning a lot.

Is 323mm where it just “ended up,” or did you pick that, specifically? I was going to try and get mine to 321-322, so 323 is right in the range.

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Shock length depends on geometry that you want to achieve and tire profile.

Bruce could be using a tire that’s smaller in diameter and needs to compensate to keep his geometry (rake/anti-squat/etc the same

The spec sheet that came with my ohlins says 317mm as delivered with +4/-8mm adjustability. I measure off the bike with preload removed with calipers like these: Amazon.com Stretching it on a jig is more accurate, but it is not worth $1k to me as a club racer.

This is a comparison of STD shock length VS ours, we run our forks flush 0.0mm
This isn't the file we use I just put some Data in to show difference, I'm away so have limited access to ur files.

Bruce Wayne said:

This is a comparison of STD shock length VS ours, we run our forks flush 0.0mm
This isn't the file we use I just put some Data in to show difference, I'm away so have limited access to ur files.

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Are you aiming for 99 mm of trail on your settings? That number seems to be the holy grail of trail these days

SuperDomestique said:

Are you aiming for 99 mm of trail on your settings? That number seems to be the holy grail of trail these days

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Bruce Wayne said:

This is a comparison of STD shock length VS ours, we run our forks flush 0.0mm
This isn't the file we use I just put some Data in to show difference, I'm away so have limited access to ur files.

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That is excellent info. Assuming spring rate is constant, 1mm of shock length change results in about 1.4mm of ride height change.

*1.2mm (it won't let me edit now)

cu260r6 said:

The spec sheet that came with my ohlins says 317mm as delivered with +4/-8mm adjustability. I measure off the bike with preload removed with calipers like these: Amazon.com Stretching it on a jig is more accurate, but it is not worth $1k to me as a club racer.

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Thanks for adding some input here.

So, I guess I really just didn't understand how some shocks are built, what a top out spring is and what a stretcher is and does. I thought the stretcher actually increased the length of the shock.

I measured the Ohlins and got 312mm, which I thought was short of the 317mm that it's supposed to be in the manual, which I thought was weird. I checked with the suspension guy that I bought it from, and he says that 317m includes the top out spring. And to get the full measurement, you have to use one of those stretcher things. So, I guess my shock is 317mm. I could have this suspension guy stretch it, but it seems that everyone's input here, and some other places, is that they come 317mm, including top out.

So, anyway. I'll keep it and install it at the 317mm length, and then make adjustments from there. I checked with some of the better teams running it in MotoA, and they say there's plenty of adjustment to get the bike set up right.

I do have the flat link on now. I put them OEM shock back on, just to see what it does to the geometry. Making no other adjustments, other than the linkage: free sag increased a few milimeters, while rider sag remained the same. Not sure if this is how it's "supposed" to work, going from progressive to more linear, but that's what I saw.

90nm spring gets here today. I'll load it on the shock and get it on the bike.

Bruce Wayne said:

This is a comparison of STD shock length VS ours, we run our forks flush 0.0mm
This isn't the file we use I just put some Data in to show difference, I'm away so have limited access to ur files.

Click to expand...

So very helpful. Thank you.

I took some pictures of some of the top MotoA bikes in parc ferme, a while back. Most had flush forks. So that seems to be the set up.

Do you have standard fork length, or are they stroked / made longer?

When I had the Sachs shock on, and forks at 5mm sticking out (which I think is how it comes), the bike was not turning in how I want. Which I why I've got all fussy about this ride height adjustment. I need to drop the forks or raise the rear, or both. But I guess I'll have to start over with this new Ohlins rear and just go from there.

cu260r6 said:

That is excellent info. Assuming spring rate is constant, 1mm of shock length change results in about 1.4mm of ride height change.

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It is, indeed.

That's a pretty low ratio, compared to other bikes, if I'm not mistaken. I thought the standard rule of thumb was 1mm of shock length is 2-3mm ride height.

Knowing absolutly nothing, my assumption is that our shocks permit a lower linkage leverage ratio (and a flatter rate overall) since they can be longer when mounted on the side. Traditional mounting locations behind the engine, below the subframe, and in front of the rear tire require a shorter shock and more complicated linkage.

JBJR said:

So very helpful. Thank you.

I took some pictures of some of the top MotoA bikes in parc ferme, a while back. Most had flush forks. So that seems to be the set up.

Do you have standard fork length, or are they stroked / made longer?

When I had the Sachs shock on, and forks at 5mm sticking out (which I think is how it comes), the bike was not turning in how I want. Which I why I've got all fussy about this ride height adjustment. I need to drop the forks or raise the rear, or both. But I guess I'll have to start over with this new Ohlins rear and just go from there.

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Bruce could be raising both front and rear for higher CoG and keeping geometry the same. Why not just throw a bolt through both shock eyelets to check if they line up to see if they’re the same length?

cu260r6 said:

Knowing absolutly nothing, my assumption is that our shocks permit a lower linkage leverage ratio (and a flatter rate overall) since they can be longer when mounted on the side. Traditional mounting locations behind the engine, below the subframe, and in front of the rear tire require a shorter shock and more complicated linkage.

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Good enough theory for me!

What kind of SAG numbers are you getting? I’m getting some weird numbers with this new Ohilns shock on. With only about 10mm of preload compression, I’m getting 14mm of free sag to get 29mm of rider sag. I messed with it a lot and tried a bunch of different things just to make sure I wasn’t doing it wrong and kept getting the same.

I backed off a bit more, to 8 mm of spring compression to get 33 mm of rider sag (I’m going for 33 to 35mm) and end up with 17-18mm free sag.

I’ve never seen free sag to rider sag ratio like this.

Ohlins shock on.

I never measure sag on a racebike, sorry. A MA tech told me free sag is somewhat useful to ballpark, but feel should determine the spring rate and preload and not rider sag.

cu260r6 said:

I never measure sag on a racebike, sorry. A MA tech told me free sag is somewhat useful to ballpack, but feel should determine the spring rate and preload and not rider sag.

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I don’t necessarily disagree with that, but usually getting it in the ballpark is a good thing to do. At least it has been for me.

Sounds like you're in the right range. My ohlins spec sheet recommends 29mm ride sag, so you're close enough to do a few laps and see how it feels. Please report back when you do.

cu260r6 said:

Sounds like you're in the right range. My ohlins spec sheet recommends 29mm ride sag, so you're close enough to do a few laps and see how it feels. Please report back when you do.

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A top team here in the states told me 30-35 is best on these bikes. When I had the Sachs shock on, I think I was at 32mm, and it felt pretty good. I'm going to shoot for similar numbers.

I think I'm going to put the standard / V2 linkage and rod back on. I'm pretty sure that I can't run the 1199 one. It was probably dumb putting it on. And I'm honestly not sure how necessary it is.

I need to get this radiator on before I can ride it. And I have Twins events the next two weeks. So I'll be on a pause with the V2 a bit.