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Interbike Dirt Demo: GT I-Drive Pro

Thought the shows were over? Nope, we've still got loads of Interbike stuff to work through - here're first impressions of GT's carbon fibre I-Drive

Posted: 9 October 2006
by Mike Davis
ib06_idrivepro_lo (34K) ib06_idrivepro_shock_lo (7K) ib06_idrivepro_seat_lo (5K)

We've still got a bunch of bikes to tell you about from Interbike's Dirt Demo - 2007 tackle that we haven't ridden enough to call "tested" but can present some brief first impressions of. GT's I-Drive Pro continues the "like an existing bike but in carbon" trend (see also: Giant Anthem Advanced, Cannondale Rush Carbon), being an evolved version of the company's 100mm travel I-Drive 4 platform.

The back end of the I-Drive Pro is the same slimline aluminium as the all-metal bikes. But it's attached to a chunky carbon front end. It's a fairly straightforward shape, with plenty of volume for stiffness and the merest hint of curves. Cable routing is internal, and we particularly like the subtle reinterpretation of GT's trademark pierced seat tube design.

Between the two bits is the I-Drive mechanism, featuring a pivoting bottom bracket that swings back and forth to minimise pedal feedback. We know riders who've tried, but just don't get on with mobile bottom brackets, but we don't find it particularly objectionable - certainly less so than the pedals kicking back at you over bumps.

The Fox RP23 shock is a particularly dinky one, and you do get the occasional feeling that it's having to work quite hard to keep up. Most of the time it's perfectly happy, though. You can coax a bit of give out of the slimline back end, but the chassis as a whole feels pretty stout thanks to the carbon bigness up front. The Pro didn't instantly blow us away like the Anthem Advanced did, but we wouldn't read too much into that - remember, these are only brief rides. We'll try and get a full test soon...

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Discuss this story


4AssedMonkey
So, you have a well tested suspension design for a mountain bike that's had lots of real world use and some refinement. You're happy with it and decide to freshen up the range with a spangly lightweight carbon model.

So do you:

"Decide" to put the shortest possible shock in and design the carbon mainframe to accomodate it, just as many manufacturers are realising the potential of longer shocks with lower ratios.

OR;

Use the tried and tested design only in carbon, with the same shock that you know works well.

OR;

Use the wonderful properties of carbon to tweak things slightly in order to run a slightly longer stroke shock without affecting the shock angle/rate.

In my head, it's NOT the first one, so why have they done it? Surely not as a gramme saving measure when they could have just specc'ed a lighter shock?

Is this a glorious cock-up that was too expensive to rectify?
Posted: 09/10/2006 15:11


Mike Davis
I believe that the shock stroke is the same as the aluminium bikes.
Posted: 09/10/2006 16:06


4AssedMonkey
Is it? That shock looks either half compressed or the umpa-lumpa version!
Posted: 09/10/2006 16:13


Owen Fackrell
It looks the same length as my idrive 4 which is a 165mm eye to eye length.
Posted: 09/10/2006 21:07


Errrmmm Yesss ( Dyl, 69ers still ROCK )
Yeah same as the ID4 in everyway but Carbon upfront. Which saves about 100grams I'd bet.

My ID5 Mediums got a 195, the Smalls have the size below this stupidly.

But thats the first ever GT review, well I've seen on BM, so good and look forward to reading the write up, being a GT ID fan.


Posted: 10/10/2006 16:31


Mike Davis
We reviewed the ID4 when it first came out.
Posted: 10/10/2006 16:57


John Gourette
So 6" bikes use 190/200mm shocks with a 50mm stroke and nobody bats an eyelid. But put a 165mm, 38mm stroke shock on a 4" bike and it's a problem. No it's not.
Posted: 10/10/2006 17:13


Mike Davis
My 4in bike uses a 200x50mm shock, and the nearest 6in bike to me has a 220mm ;-)
Posted: 10/10/2006 17:24


John Gourette
6" or 6.5" inch Mike? ;-) If so the 65mm stroke still gives a similar ration to a 165mm shock on a 4" bike.
Posted: 10/10/2006 17:46


Mike Davis
150mm, so average 2.3:1. 38 on a 100mm bike is 2.63:1, which as you say is firmly in the realms of acceptability but on the high side for my tastes ;-)
Posted: 10/10/2006 18:06


Saint Mike! :-)
(unrelated, but...)

what's that? scott ransom? short stroke, high pressure?
Posted: 10/10/2006 18:53


John Gourette
The Ransom breaks all the rules and rides great Mike!.
Posted: 10/10/2006 19:15


Errrmmm Yesss ( Dyl, 69ers still ROCK )
until the high pressure shock goes Bang and blows your legs off.

* will go look for ID4 review *


Posted: 10/10/2006 22:19


Errrmmm Yesss ( Dyl, 69ers still ROCK )
Nice review mike.

The answer to why it's different to the old design is, they've lessened the I-drive effect, so it doesn't cause the opposite reaction it's more neutral, upsides being outta the saddle peddling, downside being less active while not seated, where as I never felt that on the older design. It moves about 1/2 the amount, yes I've been comparing to my old frame.




Posted: 10/10/2006 22:32


Mike Davis
The Ransom breaks all the rules and rides great Mike!.

Aye. It helps that the shock was designed for the bike. You wouldn't want to try that kind of setup with a regular shock ;-)
Posted: 11/10/2006 09:45


Dan : /
can't help worrying that I might be picking pieces of Swinger out of my legs with the pressure I have to run for my not insubstantial weight! (Giant manual says start with putting in your weight in lbs i.e. 224)...didn't move when I did that. Out of interest can anyone tell me the shock stroke on my 05 reign? I think it's 50mm but dont ever seem to get more than about 40mm; thinking that I might not be getting me full 6'' ?
Posted: 11/10/2006 09:53


Errrmmm Yesss ( Dyl, 69ers still ROCK )
Dan take all of the air out, compress it fully and measure the stroke, if it looks to low then you might have too much oil in there.

I'm only getting 38mm's outta 50mm's on my GT, falls through the travel aswell, so looking into getting a larger AVA air can to sort this soon.


Ot I could fit my vannila and sell it :)


Posted: 11/10/2006 11:51


Dan : /
cheers Dylan, I did take all the air out a while back and still only seemed to get 45mm ish. The think is I've never actually noticed bottoming the suspension out so I dont know whether I've used full travel. If I soften it any more then it gets too soft and sags about 20-25mm. It could be a 50mm stroke shock but it could also be 45mm!
Posted: 11/10/2006 11:59


Errrmmm Yesss ( Dyl, 69ers still ROCK )
whats the eye to eye length ( middle of the 1 bolt to the other ) if it's 195 then it's 50mm.

drain abit off oil out by angling the bike so the air valve is at the low point, when you release some air it'll force some oil out don't drain to much, see if that helps.


Posted: 11/10/2006 12:13


Dan : /
cheers I shall have a poke with it tonight!
Posted: 11/10/2006 12:16


Mike Davis
What pressure have you got in the SPV chamber?

Posted: 11/10/2006 14:30


Mike Davis
Oh, and you can't let damping oil out of a shock through the air valve unless something has gone horribly wrong. Any oily stuff that comes out of the valve is just air sleeve/seal lubricant.
Posted: 11/10/2006 14:31


Errrmmm Yesss ( Dyl, 69ers still ROCK )
Sometimes there still over filled, not that sorting mine out got me more than 1/2inch more travel. ( it's not damping oil, thats sealed seperately )



Hence AVA sleeve, or old Coil on there :)


Posted: 11/10/2006 15:01


Errrmmm Yesss ( Dyl, 69ers still ROCK )
SPV loads, his regien rides like a HT pretty much.


Posted: 11/10/2006 15:01


Dan : /
Mike, I've got quite abit in the SPV; cant remember exactly but about 120 ish I think. To be honest I'm always fiddling with the SPV pressure because I'm trying to get a balance between small bump plushness and pedalling efficieny (although the reign doesnt really bob that much anyway). Mike can you recommend any particular setup that you found worked when you tested the reign? I'm about 225lbs if that helps. Also do you happen to know what the stroke should be on the shock? cheers

Dylan; I'll have you know I dont ride by bike like a hardtail..I aim for the big rocks on purpose!

;-)
Posted: 12/10/2006 10:06


Mike Davis
Dan, since you weigh about 50% more than me, I don't think my setup would be terribly relevant ;-) I usually start with the minimum pressure in the SPV, set the sag with the main chamber and go from there, adding SPV pressure until it all feels stable enough or the small-bump sensitivity goes away. The two chambers are a bit interdependent, though - if you change one you may have to change the other too.

Stroke should be 50mm, off the top of my head.
Posted: 12/10/2006 10:14


Dan : /
cheers mike
Posted: 12/10/2006 10:25


Errrmmm Yesss ( Dyl, 69ers still ROCK )
Dan its likely the pressure we are running them at causing them to ramp up more than normal towards the end, hence no full travel, hence for me a AVA sleeve should sort it.


Posted: 12/10/2006 11:23


Dan : /
yeah, not really sure to be honest. Coming off drop offs the suspension doesnt feel like it ramps up. I thought I was getting full travel on the peaks rides as on that first stupidly rocky descent I was matching Tims speed (on the whyte 46) and the suspension felt ok, however if it really is a 50mm stroke shock then I must have only been getting 5 and bit inches out of it.
Posted: 12/10/2006 13:16


Errrmmm Yesss ( Dyl, 69ers still ROCK )
Mine falls through the travel then ramps up to only get 3.8inches of travel, outta the 5.

Not that I'm saying I care or need the other inch, I tried with the Sag at 50% area still didn't get near full travel.


not willing to drain more air out.



Must price a AVA sleeve :)


Posted: 12/10/2006 13:27


Cormac Eason
Have you tried letting the air out of the shock and seeing whether it compresses the full way without air in it? It sounds like the shock has too much oil in it (This is a common problem with Marzocchi forks). How to drain oil from teh shock depends a lot on the shock though I don't thin it'll just come out of the air valve as you compress it like with Marzocchi forks.
Posted: 12/10/2006 13:54


Mike Davis
Have you tried reading the whole thread? :-)
Posted: 12/10/2006 13:59


Errrmmm Yesss ( Dyl, 69ers still ROCK )
Been there Suggested that Cormac, but you can't be expected to read all, a mistake I often make.


I'm struggling after 3years of blissful Coil useage :)



Posted: 12/10/2006 14:11


Errrmmm Yesss ( Dyl, 69ers still ROCK )
Dan, have you tried doing a 20ft drop to flat ?? might get full travel then :)



Posted: 12/10/2006 14:12


Cormac Eason
Oopsie :¬/

Silly multi page threads...
Posted: 12/10/2006 14:18


Dan : /
hmm, I might leave the 20 ft drop until I my knee pads are broken in ;-)


oh I dunno, might contact giant and see if they have any suggestions. It's not that the bike feels bad or anything and I know it's pretty quick down the downs but I just feel like I paid for 6'' so I want 6''!!

*awaits smutty remarks*
Posted: 12/10/2006 14:45


Errrmmm Yesss ( Dyl, 69ers still ROCK )
Male Pro's always lie Dan, if you want 6"'s, you've got to Pay for 7"'s.


Posted: 12/10/2006 14:55


Dan : /
eh?
Posted: 12/10/2006 16:38


Errrmmm Yesss ( Dyl, 69ers still ROCK )
Sorry you asked for a Smutty remark, that was the best I could do at the time.


Posted: 12/10/2006 16:41


Errrmmm Yesss ( Dyl, 69ers still ROCK )
Just slapped big 2.5 All condition, but mud capable tyres on the GT, to hell with the convention of going smaller for mud :)

Small test so far, gives it a 29er feel, ignores rocks and roots, accelorates abit slower (1%), but holds it's speed better (10%)

Need to try it on peaks rock soon I think :)



Posted: 12/10/2006 16:44

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