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doctorstewie":3tvgwwr9 said:
The bottom bracket pivots in the bb shell which by using witchcraft means it's active all the time, unlike urt.
Can someone explain the appeal and longevity of GT i Drives?
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The bottom bracket pivots in the bb shell which by using witchcraft means it's active all the time, unlike urt.
scottproonly
Retro Guru
I really did used to like the way my idrive rode.it certainly did not ride like a urt.the thing that let mine down was the interrupted seat tube combined with my riding style caused 2 seat towers to snap.then my next bike was a specialized enduro and that broke at the interrupted seat tube too. Then,as if by magic gt and specialized and lots of other companies stopped making frames this way. It cant be a coincidence! Sorry to hijack the thread but the op did mention longevity.
doctorstewie
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Brock: that's the thing: It's the witchcraft that amazes me. It seems to me ( and I am not trying to be difficult ) that they have spent a hell of a lot of effort in making an urt not ride like an urt. I'd have just not made an urt. Then again I am out of work and they are engineers so fair play to them: they are smarter than me
I would really like to know how they get past the massive unsprung weight by using the pivoted BB shell.
I would really like to know how they get past the massive unsprung weight by using the pivoted BB shell.
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I can't remember why exactly but the witchcraft means it's not urt. It's a clever system that allows the pivot point to be in a better position than most. It's just that the one I had was early and not high spec so not very impressive.
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twain":35m3tnda said:
Hi
Unified rear triangle
To best understand it basically it's the rear end on an early full suspension rig, a solid triangle with NO pivot points within the structure itself, check out the ass end of my Orange X1 in signature or the Schwinn both are classes as URT's
By 1997/8 most had moved away from the design but GT and a few others stick with and played with the design for a little longer.
works well but other designs worked better and allowed for greater travel, for the past 10 years its been the preserve of cheap catalogue bikes, But has since made a comeback on a Szabo 29er
Check out last pages on Schwinn build for a look at it
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According to an old MBUK the idea was to make a suss system that didn't always feel like suss so that people who were used to rigid rear ends would not be put off. URT is laughed at now but if you think about what most people were riding at the time it makes sense.
thanks Spud - am familiar with that design - just never heard its proper term
i guess horst link is the go to now (so i've heard/seen) am i right in thinking the action of the URT design creates more of a 'radial/arc' like swing at the back than the more 'vertical/paralell o the frame' movement horst link provides? (avoiding slackening the chain when bouncing up and down)???
unless i've got that wrong, but its what makes sense in my head when i think how each linkage moves...
i guess horst link is the go to now (so i've heard/seen) am i right in thinking the action of the URT design creates more of a 'radial/arc' like swing at the back than the more 'vertical/paralell o the frame' movement horst link provides? (avoiding slackening the chain when bouncing up and down)???
unless i've got that wrong, but its what makes sense in my head when i think how each linkage moves...
doctorstewie
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Twain: yep. More to the point it's much less active when you are standing up, because the BB is on the swingarm. Suspension works better the less weight is on the UNsprung part of the system. ( ie the stuff outboard of the shock ) because it's less mass to move and therefore takes less energy to move, meaning the bike goes faster and the suspension moves more.
When you stand up on an URT your weight gets added to the weight of the swingarm, wheel, tyre etc, so it massively reduces the effectiveness of the suspension. This was seen as a good thing by people who didn't want a bouncy bike when standing up, and you can see the appeal as it meant less adjustment of riding style. Hence I can see the appeal of such a bike, I am just saying that if that is what GT were trying to do with the iDrive - make a bike that didn't feel too suspesiony then why not just do an URT anyway? or redesign the RST which had a similar feel? But then I suppose it's just technology moving forward and the iDrive is a development of that. I guess it's just not my bag ( being a fan of single pivots or Horst Link designs )
When you stand up on an URT your weight gets added to the weight of the swingarm, wheel, tyre etc, so it massively reduces the effectiveness of the suspension. This was seen as a good thing by people who didn't want a bouncy bike when standing up, and you can see the appeal as it meant less adjustment of riding style. Hence I can see the appeal of such a bike, I am just saying that if that is what GT were trying to do with the iDrive - make a bike that didn't feel too suspesiony then why not just do an URT anyway? or redesign the RST which had a similar feel? But then I suppose it's just technology moving forward and the iDrive is a development of that. I guess it's just not my bag ( being a fan of single pivots or Horst Link designs )
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The I-drive is different though. As you say, the bottom bracket on urt is part of the rear triangle and fixed so does not work when standing up. The I-drive pivots on the bb and is not a fixed part of the rear triangle so is not urt.
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