New GT DH bike?

syadasti · Jun 21, 2004

I think that is the Mongoose Freedrive FR bike called the "Black Diamond"

A few teaser specs:
-150, 170 or 190mm adjustable travel
-interchangeable dropouts for 135mm QR hubs or 150mm through-axle

Shmoe · Jun 21, 2004

Looks like its straight outta 1996. haha.

-BB- · Jun 21, 2004

http://www.schwinnbike.com/images/catalog/lg_50.1.S4-Rocket-RebBlkk.jpg

Looks like it might be the DH version of the schwinn XC design.

syadasti · Jun 21, 2004

Its not a Schwinn though

They are all pacific bikes in reality

Here is some misc. coverage of this design:

http://www.velonews.com/tech/report/articles/6205.0.html

http://www.bikemagic.com/news/article.asp?UAN=3847

Teocali All Mountain Bike

Supposedly the revised iDrive version is better than these or the Schwinn...

Jm_ · Jun 21, 2004

The whole i-drive idea is rediculous. The point is to build something that is like a URT, but through the use of eccentricts or linkages, keep the bottom bracket in the same relative place...

Just make it a single pivot bike.....it would be 10x simpler and have most of the same traits. I realize it wouldn't looks as complicated though... :rolleyes:

Seriously, it's complicated for the sake of stupidity, there are so many other bikes out there that are way simpler, and require much less metal to make(and therefore lighter with less engineering) and will have as good or better pedaling/suspension traits.

Jm_ · Jun 21, 2004

stoney98 said:
it has the seated pedaling characteristics of a urt (good)
the standing susp of a single pivot (good)
very moinor chaingrawth (good)

what's to not get?

You got to be kidding?

The seated pedaling chars of a URT are very bad, in no way are they "good".

The standing suspension of a single pivot? Err...just make it a single pivot then...

Minimal chain growth? Not any more minimal than an FSR bike or other, notice that the BB does change on an I-drive as it goes through travel, that means chain growth.

Even still, a conventional diamond-type frame is always going to be far lighter, and variations on the diamond not too far off, and in the end bikes like the specialized stumpjumper, iron horse hollowpoint, trek fuel, GF sugar, are far ahead of the I-drive, no matter how different they make the I-drive look.

syadasti · Jun 21, 2004

I always get a laugh when I see people who bought those Maverick creations

Another version of this oddity that still survives today...

I suppose isn't not as bad as a single crown inverted fork... Oh wait, they are going to make one of those too :nuts:

Jm_ · Jun 21, 2004

syadasti said:
I always get a laugh when I see people who bought those Maverick creations Another version of this oddity that still survives today...

I suppose isn't not as bad as a single crown inverted fork... Oh wait, they are going to make one of those too :nuts:

Well, the dual crown maverick works for a few reasons, by bulging the uppers they were able to weld a hollow crown and have 50-something-mm uppers with relatively small 30mm stanchions. It saves tons of weight, but make no mistake, it's an XC fork, the tubes are very thin and it's not recommended for anything freeride. It also doesn't ride as well as say a Z150, but it rides pretty darn well considering the weight. It uses an air spring and a closed cartridge damper, so those are some limiting factors, but still, for the weight there is nothing that approaches it, and it's a pretty sound idea.

The single crown on the other hand is a bad idea. Single crown inverted forks are bad because they are flexy in the most CRITICAL direction for a fork to be stiff. With enough material and engineering they can work, but you can make a cheaper, lighter, and simpler single crown non-inverted fork much easier, so it begs the question, why? The "stiffer for and aft" myth is easily negated by just using bigger diameter tubes, Like on my shiver SC, it has 30mm stanchions but the uppers are bigger. New standard forks have 32mm stanchions. Any "stiffer for-aft" advantage that my shiver SC had is not gone because fork makers are using bigger stanchions now. The "less unsprung weight" myth is easily negated by a slight variation in rim and tire choices. Fork lowers are usually magnesium and extremely light, a half-pound variation in tires and wheels (not that hard to do) is going to completely negate the "less unsprung weight" advantage. Inverted is not the way to go for a single crown.

RhinofromWA · Jun 21, 2004

Jm_ said:
The whole i-drive idea is rediculous. The point is to build something that is like a URT, but through the use of eccentricts or linkages, keep the bottom bracket in the same relative place...

Just make it a single pivot bike.....it would be 10x simpler and have most of the same traits. I realize it wouldn't looks as complicated though...

Seriously, it's complicated for the sake of stupidity, there are so many other bikes out there that are way simpler, and require much less metal to make(and therefore lighter with less engineering) and will have as good or better pedaling/suspension traits.

I am going to side with Jm_ here.....

I never warmed up to these rigs....like Jm_ says, why? The old GT had chain growth and BB movement...so do these. The riders weight is suspended on a suspension member.... :think:

Don't know if it effects it enough to make a difference. Will it make it more URT like when standing?

I will say it has just as many moving parts as a 4 bar though.....

*starting something*

lol

RhinofromWA · Jun 21, 2004

stoney98 said:
Chaingrowth, if there is that much, why then was I able to single speed my I-drive w/o and issues?

w/o "any issues" ? no tensioner? Confused.....there is chain growth....is it enough? Got any pics....are you riding it like that right now? Is your chain tight throughout the travel?

Jm_ · Jun 21, 2004

stoney98 said:
Chaingrowth, if there is that much, why then was I able to single speed my I-drive w/o and issues?

I didn't say it was excessive. Where did you read that?

My point was that while it is minimal, there are other bikes where the same is true, and they are far simpler.

Lexx D · Jun 21, 2004

Jm_ said:
You got to be kidding?

The seated pedaling chars of a URT are very bad, in no way are they "good".

The standing suspension of a single pivot? Err...just make it a single pivot then...

Minimal chain growth? Not any more minimal than an FSR bike or other, notice that the BB does change on an I-drive as it goes through travel, that means chain growth.

Even still, a conventional diamond-type frame is always going to be far lighter, and variations on the diamond not too far off, and in the end bikes like the specialized stumpjumper, iron horse hollowpoint, trek fuel, GF sugar, are far ahead of the I-drive, no matter how different they make the I-drive look.

The chain growth thing is wrong. The one nice thing about urt(or i drives) was how the suspension didn't effect shifting or chain length. An fsr changes chain length quite a bit. That's why they don't always shift as well as other designs.

:think:

who cares if it's going to be lighter? They are try to make it pedal better and shift better. Who cares if a fuel is lighter? We're talking about a new DH bike here.

Jm_ · Jun 21, 2004

Lexx D said:
The chain growth thing is wrong. The one nice thing about urt(or i drives) was how the suspension didn't effect shifting or chain length. An fsr changes chain length quite a bit. That's why they don't always shift as well as other designs.

who cares if it's going to be lighter? They are try to make it pedal better and shift better. Who cares if a fuel is lighter? We're talking about a new DH bike here.

don't comment if you don't understand the I-drive.

The bb placement is not constant, and it doesn't work the same as a URT.

The dogbone attaches the bottom bracket to the frame, and causes it to "rotate" in the eccentric. So as the rear end moves away from the main frame, the bottom bracket moves CLOSER within the eccentric. In effect, similer to what would happen if it was just a single pivot.

This is why there is chain growth, this is why it pedals better than a standard URT.

syadasti · Jun 21, 2004

Lexx D said:
The chain growth thing is wrong. The one nice thing about urt(or i drives) was how the suspension didn't effect shifting or chain length. An fsr changes chain length quite a bit. That's why they don't always shift as well as other designs.

FSR does not have lots of chaingrowth.

You want a bike with lots of growth, check out a high pivot bike like a bullit :eek:

RhinofromWA · Jun 21, 2004

Lexx D said:
The chain growth thing is wrong. The one nice thing about urt(or i drives) was how the suspension didn't effect shifting or chain length. An fsr changes chain length quite a bit. That's why they don't always shift as well as other designs.

I drives did/do (old school design) have chain growth.... The Idrive tried to get a little chain growth and a little BB movement to help make neither a problem compared to a URT design. (atleast that is my take) An URT with it's BB has zero chain growth the I-Drive did have some.....an URT also had BB movement tried to decrease with the Idrive withteh Dogbone/Eccentric set up.

Do FSR designs shift that bad? I have heard the Yeti/Schwinn DH bikes had more of a problem than the other similiar designs something with havin to mount the derailer in a wierd place.

RhinofromWA · Jun 21, 2004

syadasti said:
FSR does not have lots of chaingrowth.

You want a bike with lots of growth, check out a high pivot bike like a bullit

My LTS and STS did!

This is not mine but it is a year older than my old STS. It did have noticable chain growth....atleast I noticed it.

Rhino

syadasti · Jun 21, 2004

RhinofromWA said:
My LTS and STS did!
This is not mine but it is a year older than my old STS. It did have noticable chain growth....atleast I noticed it.

Rhino

Here I'll make it easy for you to read

FSR does not have lots of chaingrowth.

You see lots would be something like a Bullit where the chaingrows about 2-2.5"

Not a FSR bike where the chaingrowth is minimal. If they scaled the Bullit down to the same travel as your LTS/STS, it would probably have something like 1-1.5" of growth at that travel vs. little or no chainstay on a properly made horst-link bike. You are probably confusing some other effect of poor GT design...

RhinofromWA · Jun 21, 2004

syadasti said:
Here I'll make it easy for you to read

FSR does not have lots of chaingrowth.

You see lots would be something like a Bullit where the chaingrows about 2-2.5"

Not a FSR bike where the chaingrowth is minimal. If they scaled the Bullit down to the same travel as your LTS/STS, it would probably have something like 1-1.5" of growth at that travel vs. little or no chainstay on a properly made horst-link bike. You are probably confusing some other effect of poor GT design...

Oh I read it, and I am telling you my GT(Though not an FSR but similiar) had much chain growth....or so it felt through the pedals. Even at 4.5" of travel....it was definately noticable.

You are confusing "little" and "no." It is impossible for a FSR not to have change in the chainstay length.

For an FSR design to have a verticle wheel path (or so they like to say) it has to have chain stay growth.....it just can't even be near verticle without it.

Unless you are saying your FSR design acts like a Rotec (concentric BB pivot? haha) and I don't think you are.

"Little" chainstay growth is an opinion. "Some" or "none" is fact.

The GT was coined active in it's day....it fall kind of inbetween the old Giant NRS(?) and a Horst link bike as they are seen today.

Jm_ · Jun 21, 2004

RhinofromWA said:
For an FSR design to have a verticle wheel path (or so they like to say) .

but really they do not.

They move in an arc about a virtual pivot. The arc is "more vertical" than a single pivot, BUT it's still an arc, it's not vertical. The fact that is is an arc means that the chain growth is pretty minimal, although comparing a 3" FSR with a 9" FSR type bike is just not a fair comparission, there's a huge difference in chain growth between the two.

Skookum · Jun 21, 2004

holy crap talk about havin opinions..... they hand out phd's for mt. biking knowledge to some of you guys? yipeee that'll go far...

i don't like new GT's. :blah:

RhinofromWA · Jun 21, 2004

Skookum said:
holy crap talk about havin opinions..... they hand out phd's for mt. biking knowledge to some of you guys? yipeee that'll go far...
i don't like new GT's.

U R a closet new GT lover....come on, admit it!

RhinofromWA · Jun 21, 2004

Jm_ said:
but really they do not.

They move in an arc about a virtual pivot. The arc is "more vertical" than a single pivot, BUT it's still an arc, it's not vertical. The fact that is is an arc means that the chain growth is pretty minimal, although comparing a 3" FSR with a 9" FSR type bike is just not a fair comparission, there's a huge difference in chain growth between the two.

If it is moving up more verticle than a BB pivot it has growth....to the extent it is a problem is simply a opinion/personal taste.

Kind of like "verticle"...it is more verticle than other "not so" verticle designs.....and I guess we should ask if the chainstay growth we are talking about is the distance between the BB spindel and the axle or the relation it is for and aft from each other?

The farther it goes up with less arc the longer that chainstay gets......

(FWIW, I already knew the FSR's were not truely verticle designs....and I don't know, relatively, anything about suspension!

haha)

bighitfsr · Jun 21, 2004

"An fsr changes chain length quite a bit"

Depends on which FSR.
A BigHit has about 5mm (Max) of chain growth, an M1 has more chain growth than a geminiDH, yeti dh9, v10 ...).
Bighits have virtually the same axle paths as stinkys (and any other bike with the swing arm pivot right behind the BB), not straight up and down at all.
Notice how much lower the horst link on an M1/haro DHR is compared to a bighit.
If you take the spring off the shock of my bighit and cycle the suspesion the derailer barely moves, absolutely minimal chain growth.

The mechanic at my LBS (mech engineering student) is building his own g-boxx DH bike and has been evaulating popular suspension designs as part of research project.
Another finding of his is that a v10 has pretty much a regular arc to its axle path nothing even slightly resembling an "S".

thaflyinfatman · Jun 21, 2004

Jm_ said:
but really they do not.

They move in an arc about a virtual pivot. The arc is "more vertical" than a single pivot, BUT it's still an arc, it's not vertical. The fact that is is an arc means that the chain growth is pretty minimal, although comparing a 3" FSR with a 9" FSR type bike is just not a fair comparission, there's a huge difference in chain growth between the two.

"More vertical"? Most of them ARE effectively singlepivots - the centre of curvature on most FSR bikes only varies by a few millimetres.

syadasti · Jun 21, 2004

thaflyinfatman said:
"More vertical"? Most of them ARE effectively singlepivots - the centre of curvature on most FSR bikes only varies by a few millimetres.

sshhhhh! The marketing men in black will come to take you away if you talk like that :devil:

Acadian · Jun 21, 2004

found THIS a while back when I was on I-Drives...dunno how accurate it is tho

Jm_ · Jun 21, 2004

thaflyinfatman said:
"More vertical"? Most of them ARE effectively singlepivots - the centre of curvature on most FSR bikes only varies by a few millimetres.

you missed the part where i said it was an arc, that means a constant radius, that means it travels around a point

syadasti · Jun 21, 2004

Jm_ said:
you missed the part where i said it was an arc, that means a constant radius, that means it travels around a point

He's got a point TFFM - its a special 4-bar linkage which works to achieve an effective/virtual pivot point that would be hard to achieve as a single pivot design. But some people would have a hard time noticing the huge performance difference some people/companies claim

Jm_ · Jun 21, 2004

Repack said:
About chain growth: Just draw an imaginary line between the main pivot and the rear axle. Then look where the FSR pivot is. The lower the pivot, the more chain growth. .

That's backwards. The higher the pivot is(in relation to the bottom bracket) the more growth there is.

This is why rotecs, lenzes, and coves have zero chain growth, because the pivot is around the bottom bracket, there is no growth. A traditional URT has no chaingrowth as well obviously.

As soon as the pivot is not concentric, there is chain growth, IE: the amount of distance that the chain has to travel increases as the travel increases.

This also applies to an FSR, the problem is though that the pivot on the main frame is fairly meaningless, what you really must look at is where the virtual pivot is.

Jm_ · Jun 22, 2004

Repack said:
My bad. Typo. I've been drinking and surfing again.

I'm down to one beer. I should freak out and run up and down the hall...

RhinofromWA · Jun 22, 2004

Repack said:
If it was an LTS or STS, than it was an FSR bike. The RTS was not FSR.
Not about what RFW said, but FSR depends on some chain growth. The tension on it is intended to be enough to counteract bob. Specialized claims "no pedaling input", but that is far from true.

Tell me about it.

I owned a RTS (1st FS bike) before my LTS and STS. Talk about high pivot :eek:

I loved that bike but for 1.75" of rear travel it sure bobbed (more raised with each stroke) like mad. Of course this was affter coming off my DB Ascent with Biopace chainrings. (YIKES!)

The LTS and STS were better....but still the chian growth was noticiable for me....maybe I was just sensitive after ridings years on my RTS?

If I remember right:
RTS= Rocker tuned Suspension
LTS= I forget...Link Tuned Suspension
STS= Single Tube System

thaflyinfatman · Jun 22, 2004

Jm_ said:
you missed the part where i said it was an arc, that means a constant radius, that means it travels around a point

And you missed the point: how is it "more vertical" than a singlepivot, given that a) it behaves like a singlepivot, and b) the centre of curvature is about as low as it could actually be without being bb-centric?

Besides that, what makes vertical better (than whatever alternative) anyway?

Jm_ · Jun 22, 2004

thaflyinfatman said:
And you missed the point: how is it "more vertical" than a singlepivot, given that a) it behaves like a singlepivot, and b) the centre of curvature is about as low as it could actually be without being bb-centric?

Besides that, what makes vertical better (than whatever alternative) anyway?

The radius is bigger.

Think about it, virtual pivot in front of the BB, radius, arc....

thaflyinfatman · Jun 22, 2004

Jm_ said:
The radius is bigger.

Think about it, virtual pivot in front of the BB, radius, arc....

HAHAHA!!
And the virtual pivot moves down and back, giving a centre of curvature right behind the BB, making the radius about as short as you could possibly make it with any singlepivot.

Seriously dude, drop the condescencion. It's hilariously stupid, especially when you're actually talking out your arse.

Jm_ · Jun 22, 2004

thaflyinfatman said:
HAHAHA!!
And the virtual pivot moves down and back, giving a centre of curvature right behind the BB, making the radius about as short as you could possibly make it with any singlepivot.

Seriously dude, drop the condescencion. It's hilariously stupid, especially when you're actually talking out your arse.

no, the virtual pivot does not move, that's why it is an arc

you should quit while you are behind

New GT DH bike?

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