Old GT Full Suspension - The Perfect Road Build Platform?

General Discussion about electric bicycles.
Post Reply
Electric Earth   100 W

100 W
Posts: 105
Joined: Nov 11 2018 8:02pm

Old GT Full Suspension - The Perfect Road Build Platform?

Post by Electric Earth » May 15 2020 7:27am

In my research/planning of a build to do ~35mph and long distances on bike paths, roads, and gravel rail-trails, it seems like one of these old GT full suspension bikes would be perfect. There's no need for long suspension travel if not off-roading, but I figure some rear suspension would be nice for high speeds and long distances. The main triangle in these bikes is completely open, so there's more room for a big battery than the modern full suspension bikes I've found. Is there any reason one of these old GTs wouldn't make a great build platform? I'm thinking this frame with the smallest hub-motor that'll do the speed I want, and a custom bike-packing style frame-bag with a hard lining would make for the best build. With a modern fork, it'll have a nice sized hydraulic disk front brake. I'm sure the frame wouldn't have a problem fitting a 2" tire. With any luck, maybe closer to 2.5"? A sturdy seat-post mounted rear rack would even make the rear suspension practically disappear, and maybe even the hub motor to the casual glance, and let me carry a little bit of cargo. Thoughts on using one of these for a build?

Image

SL33   10 µW

10 µW
Posts: 5
Joined: Mar 18 2020 10:30am

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by SL33 » May 15 2020 8:13am

V-brakes will be a bit weak...
Another bike i've seen like this is the specialized epic.
I've got 2 full sus e-bike that work. Trek Fuel and Devinci moonracer

Electric Earth   100 W

100 W
Posts: 105
Joined: Nov 11 2018 8:02pm

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by Electric Earth » May 15 2020 10:03am

Since the v-brake would only be in the rear, with a nice hydraulic disk front, I think it would be fine. A v-brake will easily lock a rear wheel if need be.

It's hard for me to tell very well from the picture, but the Specialized seems like it might still have a fairly small main triangle. It might be tough to fit a lot of battery in there. Kinda cool, interesting suspension design, though.

User avatar
Stealth_Chopper   1 W

1 W
Posts: 52
Joined: Aug 30 2019 8:08am

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by Stealth_Chopper » May 15 2020 6:43pm

Hi,
Yes, I considered that model, LTS and your hub motor plan reads well to me.
The bike looks good and linking the spring in that manner maybe superior to other designs.
Articles I read about the GT indicated a good ride, maybe one of the best, a winner
Complaints included squeaking which is effectively cancelled by wind noise on an eBike

" The first generation LTS frames used an investment cast titanium rocker link. The advent of disc brakes was still a few years away, so hydraulic rim brakes were the only option for riders looking for increased stopping power over cantilever brakes."
Jim Busby Jr. CT GT
"Whichever way he approached the kinematics, it (RTS below) just wouldn’t work. To make the rocker larger and to control the anti-squat with 100mm of rear wheel travel proved impossible.
Attachments
GT_LTS_1995.jpg
GT_LTS_1995.jpg (254.35 KiB) Viewed 327 times
GT_RTS.jpg
GT_RTS.jpg (229.43 KiB) Viewed 327 times
USA.jpg
USA.jpg (244.53 KiB) Viewed 327 times
Last edited by Stealth_Chopper on May 15 2020 10:14pm, edited 2 times in total.

john61ct   100 GW

100 GW
Posts: 6308
Joined: Dec 18 2018 2:06pm

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by john61ct » May 15 2020 7:27pm

What specific model is it? GT is a company right?

User avatar
motomech   1 GW

1 GW
Posts: 3464
Joined: Sep 11 2010 12:21am
Location: Punta Cana Baja Mexico

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by motomech » May 15 2020 8:43pm

Yeah, I always start w/ older FS mountain bikes for my road going ebikes. Best value in Ebiking!
...but I figure some rear suspension would be nice for high speeds and long distances.
Especially if you don't change that seat:)

Another thing you might want to spend money on are better pedal gear-sets so you can pedal along up to maybe, 25 mph. 11 T sm. on the rear and the biggest chain-ring that will fit that won't contact the chain-stay. Probably a 48T.
How fast do you want to go?
Motomech


'07 GT Idive 4 4.0, Q100H 201 frt. mounted, 14S Multistar LiPoly, elifebike 9-FET 20A controller. Mean Well HLG-320H-54A, Crazy Bobs on Alex DM32's 21 to 22 MPH. viewtopic.php?f=3&t=28151&p=1373714&hilit=Idrive#p13737

User avatar
Stealth_Chopper   1 W

1 W
Posts: 52
Joined: Aug 30 2019 8:08am

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by Stealth_Chopper » May 15 2020 10:31pm

Bike has potential, I think, do you have a G T that fits?
A Vintage Hydraulic brake maybe an option,
Your pictured triangle looks bigger than the specialized = knock off?

Imagine rocks like this GT winner vid, with power instead of pedaling.
https://youtu.be/IZ0fsxv-KNw?t=112

Electric Earth wrote:
May 15 2020 10:03am
Since the v-brake would only be in the rear, with a nice hydraulic disk front, I think it would be fine. A v-brake will easily lock a rear wheel if need be.

It's hard for me to tell very well from the picture, but the Specialized seems like it might still have a fairly small main triangle. It might be tough to fit a lot of battery in there. Kinda cool, interesting suspension design, though.

Electric Earth   100 W

100 W
Posts: 105
Joined: Nov 11 2018 8:02pm

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by Electric Earth » May 15 2020 10:49pm

I don't have the GT yet, but getting a suitable frame is something I'm willing to invest my time and effort into. So far I'm at the stage of finding the best platform to build on(within reason, monetarily). Then I'll move onto the motor selection, figure out/build battery, and select controller. I've built a couple budget friendly ebikes and am ready to spend more money on something nicer that will last. I don't mind putting $1,000 into the build. I've seen a couple of these GTs on craigslist in the past, so I know they're out there. If it comes down to it, I'm sure ebay could provide.

My goal is to probably use a the smallest hubmotor that will get me ~35mph. Stealth is the goal. More speed would be great but not necessary; I wouldn't want much less. I want this to be capable of longer trips and the speed will save me some time over the course of an 80mi trip.

User avatar
MadRhino   100 GW

100 GW
Posts: 7016
Joined: Sep 03 2010 5:28pm
Location: Montreal QC Canada

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by MadRhino » May 15 2020 11:01pm

Stealth_Chopper wrote:
May 15 2020 10:31pm
...Imagine rocks like this GT winner vid, with power instead of pedaling.
https://youtu.be/IZ0fsxv-KNw?t=112
:D
I had a Scott Unitrack at the moment of this race in 1994. Very similar bike.
Foes and Cannondale were showing their prototypes that year. They anticipated the future of DH bikes for the next decade.

That is kind of... 3 generations back in DH bike development, close to antique. :wink:
The time on this course had been cut by half since then.
Make it fool-proof, and I will make a better fool.
Current bikes
Street:
Trek Session 10 mod. Variable geometry. 70mph
Dirt:
Santa Cruz V10. 50mph

MikeSSS   100 W

100 W
Posts: 271
Joined: Jul 31 2016 10:52pm
Location: San Antonio, TX

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by MikeSSS » May 15 2020 11:50pm

I'm working on the same type project. Really like the GT LTS design, especially the open triangle. My host bike will be a Mongoose FS made before Mongoose was a Wal-Mart brand. But now I'll be looking for a GT LTS 1, 2, 3, 4 if I can find one.

MAC rear hub motor looks like a good choice, using a Grin torque arm. The MAC 8T would be the one for high speeds. I'm planning on a MAC 12T rear hub motor for a bucket list ride at Moab Slickrock Practice Loop. Planning to use a 52v, 20Ah battery.

At REI there was a seatpost rack that had available side brackets for panniers. This and a brake disc on the motor, even if not used, would make the motor less obvious. These MTX Dual Side Frames were made to fit MTX BeamRack Series racks.

Looks like you are on the right track for a good ride and practical bike. Keep us posted on your progress.

Best wishes,

Mike S

User avatar
Stealth_Chopper   1 W

1 W
Posts: 52
Joined: Aug 30 2019 8:08am

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by Stealth_Chopper » May 16 2020 1:02pm

The Specialized "Epic" FSR had a rear suspension design that caught my attention for a possible hub motor build, because it does not interfere with 'the triangle'.
Specialized_Epic_M4_Comp - Edited.png
Specialized_Epic_M4_Comp - Edited.png (511 KiB) Viewed 279 times
Specialized Stumpjumper FSR shock mount design seems opposite of some (all?)
Attachments
94_Stumpjumper_FSR_Shock.jpeg
94_Stumpjumper_FSR_Shock.jpeg (77.29 KiB) Viewed 266 times

Electric Earth   100 W

100 W
Posts: 105
Joined: Nov 11 2018 8:02pm

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by Electric Earth » May 17 2020 3:42am

Ooo. That mid-90s FSR looks promising too. Thanks for posting!

User avatar
motomech   1 GW

1 GW
Posts: 3464
Joined: Sep 11 2010 12:21am
Location: Punta Cana Baja Mexico

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by motomech » May 17 2020 10:24am

There are lot's of FS bikes w/ good triangle space, but it might take a while to find them;

viewtopic.php?f=3&t=28151&hilit=triangle+space

Early to mid 2000's Giant Trance and Anthem's, Trek Fuel's, Kona Stinky's and Rocky Mountain Edge's and Slayer's are some of the best.
A real Fox Float air shock is a plus.
Motomech


'07 GT Idive 4 4.0, Q100H 201 frt. mounted, 14S Multistar LiPoly, elifebike 9-FET 20A controller. Mean Well HLG-320H-54A, Crazy Bobs on Alex DM32's 21 to 22 MPH. viewtopic.php?f=3&t=28151&p=1373714&hilit=Idrive#p13737

2old   100 kW

100 kW
Posts: 1314
Joined: Jul 19 2014 3:20pm
Location: Socal

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by 2old » May 17 2020 11:49am

The GT is a great choice IMO; friends rode them very well off road, so should excel on road. Any of the Unified Rear Triangle (URT) bikes should also suffice although their performance off road was deemed deficient by many, should be OK on road.

User avatar
MadRhino   100 GW

100 GW
Posts: 7016
Joined: Sep 03 2010 5:28pm
Location: Montreal QC Canada

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by MadRhino » May 17 2020 12:07pm

Yep. No doubt those 1st generation DH bikes are making smooth road bikes, and they have plenty of space in the triangle.

Not for fast ebikes though, because they are not stiff enough frames for high speed with the extra weight. I’d say, faster than 40 mph, it is better to build on more recent FS frames even if battery placement is more complicated. The 2000-2010 decade had produced the most robust DH frames, because the races were extreme then. Some were stiffer than many motorcycles frames, and make the ideal ebike performance platform.
Make it fool-proof, and I will make a better fool.
Current bikes
Street:
Trek Session 10 mod. Variable geometry. 70mph
Dirt:
Santa Cruz V10. 50mph

Returnformer   10 W

10 W
Posts: 82
Joined: Apr 12 2019 12:00am

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by Returnformer » May 20 2020 7:49pm

I just came across one in Facebook marketplace:

https://www.facebook.com/marketplace/it ... 840022134/

Electric Earth   100 W

100 W
Posts: 105
Joined: Nov 11 2018 8:02pm

Re: Old GT Full Suspension - The Perfect Road Build Platform?

Post by Electric Earth » May 21 2020 7:50am

motomech wrote:
May 17 2020 10:24am
Early to mid 2000's Giant Trance and Anthem's, Trek Fuel's, Kona Stinky's and Rocky Mountain Edge's and Slayer's are some of the best.
Thanks for the link. My last bike was on a mid-2000s Trek Fuel frame. While better than most modern FS bikes, it still didn't have a ton of space. I'm not sure how big of a battery I could fit in there.

Post Reply